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Digitized by the Internet Archive 
 in 2015 
 
 https://archive.org/details/elementsofartofdOObert_0 
 
ELEMENTS 
 
 ART OF DYEING 
 
 AND BLEACHING. 
 
 C. L. AND A. B. BERTHOLLET. 
 
 .... ..isaK .--^- ■ 
 
 TRAJjfSLiTSD /HOM Tl'lt;, FRENCH, ^ 
 
 WITH NOTES ANb ENGRAVINGS, ILIJJSTR ATIVE AND 
 StJPPIElVfEN^ARt, ■ 
 
 BY ANDREW URE, M.D. F.R.S. 
 
 REVISED AND CORRECTED BY AN EXPERIENCED PRACTICAL DYER AND CALICO PRINTER. 
 
 LONDON : 
 PRINTED FOR THOMAS TEGG, CHEAPSIDE; 
 
 R. GRIFFIN AND CO., GLASGOW ; TEGG AND CO., DUBLIN AND J. AND 
 S. A. TEGG, SYDNEY AND HOBART TOWN. 
 
 MDCCCXLI. 
 
T r 
 
 SI 
 
 7 
 
 BOLT COURT, LONDON 
 
 TKE GETTY CBHi^Fi 
 
ADVERTISEMENT. 
 
 The chief object of the author of these Elements was, to apply 
 the theories which had recently diffused so vivid a light on 
 chemistry, to the phenomena presented by the art of dyeing, 
 and to its ordinary processes, of which he gave the description. 
 
 The arts can make but a limited progress, when they are di- 
 rected merely by a blind practice. Thus, they have remained for 
 several centuries in nearly the same state in China and in India. 
 But if artizans be guided by the knowledge of those properties 
 which have been investigated by physics, and its complement, 
 chemistry, there are no boundaries to the perfection which they 
 may reach. How many advantages has that nation, so powerful 
 by its industry, derived from Watt, Wedgewood, Henry, and 
 some other philosophers ! 
 
 In this respect, a happy revolution has been effected among 
 ourselves. Our manufactories are no longer intrusted to igno- 
 rant workmen. In the greater part of them are to be found 
 very enlightened individuals, well informed philosophers, to 
 whom, indeed, we must have recourse, if we wish to excite the 
 progress of the useful arts, and remove the obstacles which 
 stand in their way. 
 
 By such considerations the author of this Work has been 
 actuated. He has been less occupied with the collection of 
 recipes, than in explaining the properties on which those effects 
 depend' which we wish to produce. He has endeavoured, how- 
 ever, to introduce great precision into the description of the 
 processes, selecting those which deserve most confidence. 
 
 1,^ tCc 
 
iv 
 
 ADVERTISEMENT. 
 
 Some persons imagine, that physical theories are merely 
 systems, to which we wish to accommodate nature, without 
 regard to the practice of the workshops. Yet these theories 
 are themselves only the result of analytical experiments. To 
 observation they always appeal ; and, in seeking to direct it, 
 they fix attention on the very facts whose relations cannot as 
 yet be established with those already classed. They indicate, 
 moreover, their application, which they also try to circumscribe 
 within just limits. 
 
 The theory of the art of dyeing is connected on one side 
 with the most delicate speculations of natural philosophy ; on 
 the other, with the practice of many different arts. It is not 
 to be regarded as a portion of knowledge which can be carried 
 to perfection by itself. Its improvements must follow the 
 advancement of the physical sciences, and of several other arts. 
 
 The author of these Elements, whose sole pretensions in this 
 second edition were to render his work less defective, and to 
 introduce recent discoveries, has associated with himself a fellow- 
 labourer,* who, directing from his youth peculiar attention to 
 this object, may eventually conduct it to greater perfection. 
 
 * This fond parental anticipation does not seem to have been realized. M. Berthollet, 
 junior, died a considerable time before his father. 
 
TRANSLATOR'S PREFACE. 
 
 Among the academicians of France, who figured in the 
 antiphlogistic revolution of chemistry, M. Berthollet, if not 
 entitled to the first place, yields precedence to Lavoisier alone. 
 His early discovery of the composition of ammonia, was of 
 capital importance. It threw light on many obscure chemical 
 phenomena, and furnished an excellent mirror of gaseous re- 
 search. 
 
 But undoubtedly M. BerthoUet's peculiar merit consisted in 
 applying scientific results to the common business of life. 
 Scheele's happy genius, while examining an ore of manganese, 
 revealed to the world that singularly energetic element, chlo- 
 rine, called by him dephlogisticated marine acid. Amongst its 
 other properties noticed by this distinguished chemist, was the 
 blanching effect it had upon the cork of his phial. This pro- 
 perty suggested to BerthoUet's active mind a new art, that of 
 bleaching without exposure to sunshine and air. This art, 
 which has been of incalculable benefit to the manufactures of 
 linen and cotton, was expounded by him with much sagacity 
 and address, in a treatise, which forms a principal part of the 
 present publication. Though important improvements in the 
 mode of preparing and applying this blanching power have been 
 made, and particularly by British manufacturers, since Ber- 
 thoUet's time, it must be admitted, that his principles, as far as 
 practice is concerned, have recently received little further eluci- ^- 
 dation. The theoretical modifications, occasioned by Sir II. 
 Davy's admirable researches on chlorine, with an account of the 
 actual processes adopted by our bleachers, have been briefly 
 stated in the jiotes of the translator. 
 
vi 
 
 translator's preface. 
 
 M, Berthollet's success in bleaching naturally led the govern- 
 ment of France to select him as a fit successor to M. Macquer, 
 in superintending the dyeing establishments of that kingdom. 
 This honourable appointment, previously held by very eminent 
 chemists, turned Berthollet's attention to the art of dyeing, the 
 operations of vrhicli he seems to have studied with great assi- 
 duity. His Elements of this art must undoubtedly be regarded 
 as constituting the first truly philosophical treatise on the sub- 
 ject ; nor has any work appeared since, which can bear a com- 
 parison with it for precision of detail and explication. The 
 variou^s essays on dyeing, and dye-stuffs, which have within 
 these few years been multiplied in our Encyclopedias, &c., are, 
 in a great measure, extracts from BerthoUet. 
 
 It is more than probable, indeed, that these Elements will 
 henceforth be accounted his principal performance; for not- 
 withstanding the air of profound speculation which pervades 
 his Chemical Statics, and the valuable remarks scattered 
 through that elaborate work, the hypothesis of indefinite 
 combination which forms its basis, has greatly lessened its 
 estimation among chemists, since the theory of definite and 
 multiple combination has been satisfactorily established. Ber- 
 zelius, in his essay on chemical proportions, has endeavoured, 
 with some ingenuity, to reconcile Berthollet's statical doctrines 
 to the atomic theory, but apparently with little success. 
 
 The first edition of the Elements of Dyeing was very ably 
 translated into English by Dr. Hamilton ; and had not the 
 French philosopher published a second edition containing im- 
 portant modifications and additions, the labour of the present 
 translator would have been altogether superfluous. It is hoped 
 that the copious notes now appended, will be found a useful 
 supplement to the original work. They contain details of the 
 most remarkable chemical researches connected with dyeing and 
 dye-stuffs which have recently appeared in scientific journals, as 
 also extracts from the valuable work of Vitalis,* on the Adri- 
 anople madder red, and on calico printing, along with some 
 ' observations not hitherto laid before the public. 
 
 The Plates furnished by the translator, represent some of the 
 most useful machines at present employed in our best dyeing 
 establishments. 
 
 * Coiirs elenicntaire de tcintiue. Paris, 1823. 
 
translator's preface. 
 
 vii 
 
 The following obituary notice of BerthoUet was published by 
 M. J. J. Virey, in the Journal de Pharmacie for December 
 1822. It may probably prove acceptable to some readers : — 
 
 M. Claude-Louis BerthoUet, Member of the Royal Academy 
 of Sciences, of the Institute, and of several other academies. 
 Count and Peer of France, &c., was born in 1749, at Talloire, 
 in Savoy, He received the degree of Doctor in Medicine, 
 became attached to the house of Orleans, and entered the 
 Academy of Sciences in 1780. In 1794 he received the ap- 
 pointment of Professor of Chemistry in the Normal school, and 
 subsequently in the Polytechnic school. He was nominated a 
 member of the Institute at its formation. His probity caused 
 him to be appointed to collect the objects of art conquered in 
 our triumphs in Italy. He soon afterwards joined the memo- 
 rable expedition to Egypt, and returned in 1799, with the 
 extraordinary man who raised him to the rank of senator, 
 along with* his colleague, Monge, who appreciated the value of 
 his genius. Nominated to the Chamber of Peers by his Ma- 
 jesty, in 1814, he continued a member of it till his death, which 
 happened on the 6th of November, 1822, at the age of 73 years 
 and a few months. 
 
 His splendid career was marked by ^important discoveries, 
 although his hands were deficient in address, his style and elo- 
 cution in perspicuity. A friend of the great and unfortunate 
 founder of pneumatic chemistry, Lavoisier, he co-operated with 
 him, with Guy ton de Morveau, Fourcroy, &c., in reforming the 
 nomenclature of this science. His analysis of ammonia, — his 
 discoveries on fulminating silver, — the manufacture of the deto- 
 nating powder of chlorate of potash, — the bleaching of goods 
 by chlorine, — his researches on prussic acid, in which hydrogen 
 acts the (acidifying) part of oxygen, — his valuable labours on 
 dyeing, which first illustrated the principles of this art, — his 
 profound observations on sulphuretted hydrogen, w^hose acidify- 
 ing properties he pointed out, — above all, his capital work 
 Chemical Statics, of which he had conceived the basis amidst 
 the burning sands of Egypt, and while braving the murderous 
 steel of the Arabs — the foundation of the Chemical Society of 
 Arcueil, in that celebrated retirement of his old age, where he 
 delighted to assemble round him young men eager to collect 
 the fruits of his experience, in order to perpetuate his labours 
 
viii 
 
 translator's preface. 
 
 and his renown — such are the titles of BerthoUet to immortality, 
 if this award can be at all promised to men. 
 
 If we penetrate into the privacy of his life, we shall see 
 him, under a modest exterior, and a robust frame, concealing 
 a sensible heart; we shall contemplate this soul, too exalted 
 not to be simple in its greatness, possessed of that intrepid 
 firmness, which yielded neither to the accidents of fortune, to 
 dangers, nor to power. Never would his candour make a com- 
 promise with error or falsehood, or prefer wealth to self-esteem. 
 Even in the bosom of those political tempests which held 
 nothing sacred, he retained his imperturbable strength of mind. 
 Such lofty virtues were venerated by all parties, zealous to 
 contribute to the illustration of a glory become in some mea- 
 sure European. 
 
 His tomb has received the sincere tears of his friends, 
 Laplace, Chaptal, of his pupils erewhile, but now his honour- 
 able competitors. Gay Lussac, Thenard, and many other associ- 
 ates of labours, always subservient to the love of his country 
 and of science." 
 
 Glasgow, July 2, 1824. 
 
EXPLANATION OF THE PLATES. 
 
 Plate I. Apparatus for Bleaching by Chlorine. 
 
 Fig. 1. Horizontal projection according to the line A'B', and section of the fur- 
 naces according to C D. 
 
 A, Tub of Immersion. 
 
 B, Receiver. 
 
 M, M, M, M, M, Plates which close exactly the space between the upper shal- 
 low tub, and the sides of the receiver. Only the side looking to the furnace is left 
 open. 
 
 Q, Pipe into which the syphon for running the Chlorine solution into the im- 
 mersion tub is introduced. 
 
 O, O, Cross pieces which support the shallow tubs, and are fixed into the ex- 
 tremities N, N, N, N, of four uprights. 
 
 K, Circular grooves cut out in the plate, which closes the space between the 
 second shallow tub, and the side of the receiver, for the passage of the conductor 
 tubes, one of which is traced in the figure. 
 
 C, C, Partition which separates the receiver from the furnaces. 
 
 D, Plan of a furnace, of the boiler E, serving for a sand bath, and of the mat- 
 rass F, which communicates by the tube G with the intermediate bottle H, enclosed 
 in its double box I : in the furnace, round the sand bath, and oppqsite each angle, 
 channels have been cut, which serve as chimnies and registers. A section of the 
 second furnace D is made at the height of the fire-place, that the grate d may be 
 perceived, and the plate of iron d', which separates the fire-place from the ash-pit. 
 
 Fig. 2. Vertical section of the receiver, and of the immersion tub, according to 
 the lines A B and CD. 
 
 L, L, Shallow tubs, separated from each other by the cross pieces O, fixed on 
 the uprights N. The space between them and the sides of the receiver is closed by 
 the plates M, M, M, so as to leave a free space, but on sides alternately opposite ; 
 that is to say, from the side of the furnaces to the inferior shallow tub, as also to the 
 superior, and on the side of the immersion tub, to the middle shallow tub. 
 
 P, P, P, Tubes which allow the gas to pass from one shallow tub to its superior, 
 when it contains a stratum of it, equal to the length of these tubes. The tube of 
 the upper shallow tub is made long enough, as is shown, to disperse the gas, which 
 being undissolved in the water, would be diffused in the air, and annoy the workmen. 
 
 K, Conductor tube, which proceeds from the intermediate bottle, and terminates 
 under the lower shallow tub. 
 
 Q, Pipe which communicates down to the bottom of the apparatus, in order that 
 the syphon R may conduct the most concentrated acid (aqueous chlorine) into the 
 immersion tub. 
 
 S, Tube of safety. 
 
 D, Elevation of the furnace provided with all its distillatory apparatus. 
 
 Fig. 3. Vertical projection of the two distillatory apparatuses, according to the 
 line D D. The letters indicate the same objects as in the two preceding figures. 
 
 Fig. 4. Vertical section of a furnace, and of one of the boxes, to show its in- 
 ternal iorm, and the position of the sand bath. 
 
 Fig. 5. Plan of a furnace without a sand bath. ' 
 
 Fig. 6. Plan and elevation of the boiler serving as a sand bath. 
 
 Fig, 7. F, matrass ; T, cork of the matrass. 
 
 Fig. 8. V, small syphon to draw out the air from beneath the shallow tubs. 
 
 Fig. 9. I, box, with two square cells, serving to contain the intermediate bottles, 
 drawn on a double scale. Y, small box, which encloses the bottle held iu one of 
 the cells, by the corners X, X, X, X. 
 
 Fig. 10. Elevation of the same box, furnished with its two bottkc. 
 
 Plan and elevation of the small boxes, Y. 
 
X 
 
 EXPLANATION OF 
 
 Plate II. Fig. 1, 2, 3, 4. Apparatus for the running off leys. The same 
 letters serve for the same objects in these different figures. 
 Fig. 1. Vertical section of the apparatus. 
 
 A, tub. 
 
 B, boiler, the bottom of which is concave, and provided with a stopcock T. On 
 the pipe to which this stopcock is attached, a socket is soldered, into which the 
 glass tube, V, enters, that communicates by another kneed socket with one of the 
 wooden pipes F, which afford passage to the steam. This tube serves to show what 
 height the liquor rises to in the boiler. The bottom of this is sustained on the edge 
 of the interior masonry of the furnace, except in the part corresponding to the 
 aperture S, through which the smoke passes off. Its edges are turned back on the 
 masonry for receiving the tub, they are then raised round it, in order that the 
 vapour and the liquid may not find an outlet between the tub and the boiler. 
 
 H, Grating of deal, the ribs of which rest at their ends on the edges of the 
 masonry of the furnace, and which are supported by two bars, 1 1, connected with 
 the grating by four copper straps, which bear upon the corners. 
 
 D, Body of the pump. It has at its lower part an inverted cup, pierced with 
 small holes, to prevent in the aspiration (sucking) the introduction of bodies which 
 might hinder the valves from shutting, or might scratch the body of the pump. It 
 is prolonged by a thin copper pipe, C, which, at the upper part of the tub, carries 
 a copper heel, on which the cylinder of copper, K, rests. This cylinder stands on 
 four castors. It carries four sockets, to each of which an arm, X, X, is adjusted, 
 of a length equal to the diameter of the tub, and pierced with holes, like the bulb 
 of a watering pot. In order that the ley raised by the pump may be diffused, the 
 pipe of the pump is perforated in like manner with small holes in the whole por- 
 tion which corresponds to the copper cylinder ; and in order that the ley may not 
 run off by the bottom of this cylinder, it presses exactly at this part on the pipe of 
 the pump. The arms X are fitted on like the bayonet to the muzzle of a musket ; 
 they are taken off, for the introduction and removal of the cloths. 
 
 The cylinder is terminated by a ratchet wheel L, the number of whose teeth 
 should be a prime number, in order that having no exact divisor, the arms may not 
 be periodically brought back to the same positions. The ratchet L is set in motion 
 by a rod «, hooked to one of the pieces of wood that form the frame-work, on which 
 the balance-beam d of the pump rests, and fixed very freely by a pin to a horizontal 
 rod b. This rod is fixed in like manner, by its other extremity, to one of the branches 
 of a bell. movement M, whose, other branch communicates, by the rod c, with the 
 balance-beam. Hence, on turning the handle e, every movement of the balance- 
 beam is communicated to the rods, and onwards to the ratchet, which, for each 
 stroke of the piston, percurs the space of one tooth. 
 
 The body of the pump D and the pipe C, are joined by two straps and screws. 
 Under these straps passes an iron collar, traversed by six bolts, whose screwed ends 
 are fixed with nuts to a copper platform placed on the grating, and bears no weight 
 on the bottom of the boiler. The pipe C is also held fast at its upper end by an 
 iron strap, adapted to, and fixed on the cross bar f. 
 
 G represents the copper funnel, by which are introduced the solution of potash, 
 and the waters necessary for the lixivium. It terminates in one of the tubes F, to 
 prevent the solution of potash spouting out on the adjoining pieces. 
 
 P indicates the form of the fire-place, the grate being at R, and the ash-pit at Q. 
 The smoke issues by the aperture S, of which only half the altitude is seen here ; it 
 circulates by the flue U round the boiler, entering then into the tube of the chim- 
 ney, which rises vertically. 
 
 Fig. 2. Horizontal section of the tub taken above the platform of copper I, on 
 which are fixed by nuts the six bolts which support the body of the pump. 
 
 rrif Furnace door. ^ 
 
 The dotted lines ww, indicate the separation, formed by fire bricks, in the flue 
 which runs round the boiler, and which determines the entrance of the smoke into 
 this passage, as well as its issue into the vertical pipe p. 
 
 Fig. 3. Vertical projection of the apparatus taken in another direction. 
 
 h, Register, with which the chimney ought to be furnished. 
 
 q, Rim of the boiler turned up on the outside of the tub. 
 
 Fig, 4. Horizontal projection of the apparatus, according to the line T" G' 
 
THE PLATES. 
 
 xi 
 
 Fig. 2. V, Horizontal projection of the body of the pump, in which the details of 
 the adjustment of the piston are represented. * 
 
 D, Vertical section of the body of the pump ; r, clack valve, s, piston ; j?, cup 
 attached by a strap to the lower extremity of the body of the pump. 
 
 Fig. 4. Horizontal projection, and vertical section of the cylinder K, which bears 
 the sockets to which the arms X X are adjusted. 
 
 C, copper pipe to which is soldered the heel x : y, brass castors which rest on 
 the heel and which support the cylinder K. 
 
 u^UyU, sockets having an opening for receiving the knob soldered to the extre- 
 mity of the arms. L, ratchet wheel fixed to the upper part of the cylinder K. It 
 contains in the figure 17 teeth. 
 
 These two figures have been ^made on a double scale, in order that the details 
 might be better understood. 
 
 The apparatus for chlorine, and for the running off of leys, are on the same scale. 
 
 N.B. — To avoid embarrassing the figures, a small plank is not represented here, 
 which, when the apparatus is constructed on as large dimensions as at present, 
 should be placed at about two yards from the ground, for throwing the goods upon, 
 and from which a child can hand them to the workman, who arranges them in the 
 tub. 
 
 Fig. 5. Vessels for the testing of potashes. 
 
 1. Small measure ; it is filled by plunging the bulb into the liquid, and stopping 
 the tube with the finger whenever it is fulj. It may then be carried without fear of 
 losing what it contains. To make it flow, the finger has only to be lifted. 
 
 2. Tube containing up to the mark 50 times the small measure. 
 
 3. Goblet or jar in which the mixture of the test acid is made and the solution 
 of potash. 
 
 4. Tube employed for stirring, and making the traces on stained paper. 
 
 For the trial of chlorine, the small measure is filled with the solution of indigo, 
 which is poured into a glass jar of the same form as the above, or into a glass tum- 
 bler ; then the number of measures is introduced that are required for discharging 
 its colour. 
 
 Fig. 6. Ordinary distribution (arrangement) of the mode of running off leys. 
 
 1. Tub on whose bottom a wooden grating is placed, or some simple pieces of 
 wood, which prevent the cloths, when heaped, from choking up the aperture of the 
 pipe 3, by which the ley falls back into the boiler. 
 
 2. Boiler, here represented cut vertically through its diameter, or order to see 
 its form. Those usually employed are different, and do not possess the advantage 
 which the present one does, of directing the liquid, which spouts up, when the 
 ebullition is brisk, towards the middle of the boiler. It has been, moreover, repre- 
 sented as mounted on a furnace different from those which the bleachers usually 
 construct. Its construction is nearly the same as that of the furnace of 
 
 Fig. 1. The form of this boiler and of its furnace is adopted in a great many dye- 
 houses. When their dimensions are good, there is much economy of fuel, and con- 
 venience of manipulation. Those of the figure have been copied from well con- 
 structed furnaces. If pit coal be burned, the height of the fire-place should be 
 diminished a little, and if turf, a little increased. 
 
 Instead of sinking the furnace into the ground, its bottom may, however, be put 
 nearly on a level with that of the tub, and the ley made to fall back from the tub 
 into the boiler by a kneed pipe, w^hich reaching to near the bottom of the tub, and 
 opening above the .boiler, does the office of a syphon, and reconveys to it the leys 
 which had gone through the v^hole thickness of the goods. 
 
EXPLANATION OF THE PLATES 
 
 FURNISHED BY THE TRANSLATOR. 
 
 Plates I. and II. represent the padding machine, for applying mordants to 
 cotton cloth, or generally speaking, for passing cloth through any chemical solution. 
 It consists of a frame in which are placed two rollers, either of wood with an axis of 
 iron, or of cast-iron covered with copper. The upper roller is pressed, by means of 
 levers, against the under one, which revolves horizontally in a box, containing the 
 mordant that is to be put on the cloth. 
 
 The bevelled wheel and shaft that convey the power to the padding machine, are 
 represented in plate II. as inclined ; a circumstance not essential, but accidentally 
 required in the particular machine from which this drawing was taken. 
 
 Plates III. and IV. represent the wash or dash weel. The pieces of cloth are put 
 into the quadrantal compartments of the wheel, into which a stream of pure water 
 flows through a circular slit in its posterior surface. By the rotation of the wheel, 
 the cloth is dashed backwards and forwards between the quadrantal partitions. 
 Twenty-five revolutions per minute is the proper speed of a wash wheel six feet in dia- 
 meter. Some persons suppose them to perform better with twenty- six or twenty- 
 seven revolutions ; but any considerable deviation from this velocity either impairs 
 the utility of the machine, or destroys its functions altogether. In these and the 
 other plates, the parts are so distinctly delineated by the artist, as to supersede the 
 necessity of letters of reference and minute explanation. 
 
 Plate V. A bucking boiler, exhibiting the fire-place, the iron boiler, surmounted 
 by the wooden crib, with its grated bottom and central iron pipe. Whenever the 
 water or alkaline ley boils briskly, its vapour, confined by the goods in the crib, 
 presses on the surface of the liquid, and forces this to issue in a sudden stream 
 from the top of the pipe, whence it is spread over the surface of the goods, and 
 gradually percolates down through them. The liquid in its descent becomes slightly 
 cooled ; but after a little while, accumulating and becoming hot again in the boiler, 
 a new eruption of boiling liquid takes place. A more complex, though, I believe, 
 not a more effective form of bucking apparatus, is described in the Edinburgh Ency- 
 clopedia, article Bleaching, 
 
 Plates VI. and VII. Cylinder printing machine. 
 
 A. The engraved copper roller. 
 
 B. The mandril on which the roller is fixed. 
 
 C. The back roller covered with soft materials. It presses the piece of cloth to 
 be printed against the copper roller, 
 
 D. Situation for a second copper roller, when two colours are to be applied at 
 once. In this case, the back roller is pressed against it by means of the screws E. 
 
 F. The colour-box. 
 
 G. Steel doctor for scraping off the colours from those parts of the roller which 
 are not engraved. 
 
 H. Wheel which gives a horizontal motion to the doctor. 
 
 I. A long piece of thick woollen cloth, sewed end to end, which passes under the 
 back roller, along with the piece of cloth to be printed. 
 
 K. Beam on which the pieces of cloth are rolled before being printed. 
 
CONTENTS. 
 
 Historical Summary of the Art of Dyeing 
 
 FIRST PART, 
 
 OF DYEING IN GENERAL. 
 
 Page 
 1 
 
 SECTION I. 
 
 OP THE GENERAL PROPERTIES OF COLOURING SUBSTANCES, 
 
 Chap. I. Of the Theory of Colours, and of the distinctive Properties of 
 Colouring Particles ..... 
 II. Of Mordants ...... 
 
 III. Of Astringents in general, and particularly of the Gallic Acid and 
 
 Tannin ...... 
 
 IV. Of the action of different substances, particularly of Air and Light; 
 
 on Colours ...... 
 
 V. Recapitulation of the Theory laid down in this Section 
 
 19 
 40 
 
 53 
 
 71 
 87 
 
 SECTION IL 
 
 OF THE DIFFERENCES WHICH DISTINGUISH WOOL, SILK, COTTON, AND LINEN, 
 (flax,) and OF THE OPERATIONS BY WHICH THESE SUBSTANCES ARE 
 DISPOSED TO RECEIVE DYES. 
 
 Chap, I. Considerations on the 
 Substances 
 II. Of Wool 
 
 III. Of Silk 
 
 IV. Of Cotton 
 
 V. Of Flax and Hemp 
 
 differences between Animal and Vegetable 
 
 93 
 95 
 101 
 108 
 111 
 
 SECTION in. 
 
 OF BLEACHING BY THE OXYGENATED MURIATIC ACID (CHLORINE.) 
 
 Introduction 
 
 Chap. I. Theory of Bleaching 
 
 116 
 118 
 
xiv 
 
 CONTENTS, 
 
 Page 
 
 Chap. II. Of the Preparation of Chlorine Liquor . . . .121 
 
 III. Of Leys 126 
 
 IV. Of the Immersions in the Chlorine Liquor . . .136 
 V. Of the Washings . . . . . .139 
 
 VI. Of the other Operations of Bleaching .... 141 
 
 VII. Number and Order of the Operations . ' . . . 144 
 
 VIII. Of the different Preparations of Bleaching Liquor . .146 
 
 IX. Of the other Uses of Chlorine . . . . 150 
 
 1. Preliminary Maceration of the Fibres . . . 158 
 
 2. Of the Leys and Immersions in Chlorine . • . .159 
 
 3. Bath of Sulphuric Acid . . . . .160 
 
 4. Soaping . . . . . . . ib. 
 
 5. To give Pliancy to Hemp -Cotton . . . .161 
 
 6. To give the Appearance of ordinary Cotton to Hemp-Cotton ib. 
 
 SECTION IV. 
 
 OF DYEING OPERATIONS IN GENERAL. 
 
 Chap. I. Of Dye-houses and the Manipulations of the Art of Dyeing . 162 
 II. Of Fuel . . . . . . .166 
 
 III. Of the Means of ascertaining the Goodness of a Colour (Dye) . 174 
 Instructions concerning the Debouilli (chemical trials) on Wool 
 and Woollen Cloths . . . . . * . 179 
 
 SECTION V. 
 
 OF THE CHEMICAL AGENTS EMPLOYED IN DYEING. 
 
 Chap. I. Of the Acids ....... 188 
 
 1. Of Sulphuric Acid . . . . . .191 
 
 2. Of Nitric or Nitrous Acid . . . . .194 
 
 3. Of Muriatic Acid ...... 200 
 
 4. Of Aqua Regia, or Nitro-muriatic Acid . . . 205 
 
 5. Of Bitartrate and Binoxalate of Potash, and of Acetic Acid . 210 
 II. Of Alum, or the Sulphate of Alumina . . . .215 
 
 III. Of the Sulphate, and some other Combinations of Iron . . 224 
 
 IV. Of Sulphate of Copper . . . . . 229 
 V. Of Verdigris, or the Acetate of Copper . . . .231 
 
 VI. Of the Acetate of Lead, or Salt of Saturn . . . 235 
 
 VII. Of the Fixed Alkalies . . . . .237 
 
 1. Of Potash . . . . . . ib. 
 
 2. Of Soda . . .... 242 
 
 VIII. Of Soap . . . .... 245 
 
 IX. Of Sulphur . . .... 248 
 
 X. Of Waters . . . . . . .250 
 
CONTENTS. 
 
 XV 
 
 SECOND PART. 
 
 OF THE PROCESSES OF ART. 
 SECTION I. 
 
 OF BLACK. 
 
 Page 
 
 Chap. I. Of the Processes for Dyeing Black .... 253 
 
 II. Observations on the Processes for Dyeing Black . . . 265 
 
 III. Of Grey . . . . . . .269 
 
 SECTION II. 
 
 OF BLUE. 
 
 Chap. I. Of Indigo . . . . . . .273 
 
 II. Of Pastel and Woad . . . . . .286 
 
 III. Of Dyeing Blue with Indigo and Pastel Vat . . .290 
 
 IV. Of Saxon Blue . . . . . . .303 
 
 V. Of Dyeing Blue by means of Prussiate of Iron . . . 307 
 
 SECTION III. 
 
 OF RED. 
 
 Chap. I. Of Madder ....... 313 
 
 II. Of the Processes used in Dyeing with Madder . . . 320 
 
 Process of Adrianople, or Turkey Red . . . 327 
 
 III. Of Cochineal 342 
 
 IV. Of Dyeing Scarlet . . . . . . 347 
 
 V. Of the Crimson Dye . . . . . .354 
 
 VI. OfKermes . . . . . .359 
 
 VII. Of Lac, or Gum Lac . . . . . .363 
 
 VIII. Of Archil . 365 
 
 IX. OfCarthamus . . . . . . .369 
 
 X. Of Brazil Wood . . . . . . .377 
 
 XI. Of Logwood . . . . . . .384 
 
 SECTION IV. 
 
 OF YELLOW. 
 
 Chap. I. Of Weld . 388 
 
 IL Of Fustic {Bois Jaune) . . . . .393 
 
 III. Of Quercitron . . . . . . • 395 
 
 IV. Of Annotto (Roucou) . . . . . - 398 
 V. Of Saw-wort {Sarrette) Serratula Tinctorial and several other 
 
 Articles capable of Dyeing Yellow .... 402 
 
xvi 
 
 CONTENTS, 
 
 SECTION V. 
 
 OF DUN, ROOT, OR FAWN COLOUR (fAUVE.) 
 
 Page 
 
 Chap. I. Of Walnut Peels . . • . .409 
 
 II. Of Sumach, and some other Substances capable of affording a Dun 
 
 Colour . . . . . . .412 
 
 SECTION VI. 
 
 of compound colours. 
 
 Of the Mixture of Blue and Yellow, or Green . . .419 
 
 Of the Mixture of Red and Blue . . . . .428 
 
 Of the Mixture of Red and Yellow . . . .438 
 
 Of the Colours resulting from the Mixture of Black with other 
 
 Colours, and of Brownings . . . . .440 
 
1 
 
\ 
 
 I 
 
 \ 
 
PLATE VI. 
 
HISTORICAL SUMMARY 
 
 OF 
 
 THE ART OF DYEING. 
 
 The desire of attracting public admiration may be observed 
 even in the least civilized state of society. Among the means 
 of distinction which are eagerly laid hold of, the glare of colours 
 is one of the most obvious. Savages assume an imposing aspect, 
 by staining their skins, or v^earing feathers, stones, and shells, 
 with gaudy colours. The Gaulish women gave themselves, on 
 festivals, an olive-brown complexion, by means of woad ; and 
 those of high rank were no doiibt jealous of this distinction. 
 
 The art of dyeing, therefore, has unquestionably a very an- 
 cient origin ; for when nature afforded colouring substances of 
 easy application, there might arise among people but slightly 
 civilized, methods of dyeing which have been sought after by 
 polished nations. Thus the Gauls prepared some dyes which 
 were not disdained by the Romans. ^ But for its enlargement 
 and perfection, the art required to follow the progress of manu- 
 factures and luxury. 
 
 The Egyptians, according to Pliny,* had discovered a mode 
 of dyeing analogous to that of our printed calicoes. Cloths, 
 impregnated probably with different mordants, were plunged 
 in a bath, in which they assumed different colours. He alludes 
 to the employment of these mordants in the following passage : 
 Candida vela postquam attrivere, illiuuntur non coloribus, aed 
 colorem sorbentihus medic amentis. It may, however, be pre- 
 sumed, that manufactures possessed little activity among a people 
 
 * Hist, Natur. lib. xxxv. cap. 2. 
 B 
 
2 
 
 HISTORICAL SUMMARY. 
 
 where the authority of the priesthood prohibited by law every 
 change in even the most indifferent customs. 
 
 It is to Greece that our attention turns, when we wish to 
 ascertain the progress which the human mind had made in an- 
 tiquity. Here, however, we find a vast difference between 
 the fine arts,* and the useful arts, or the arts of luxury ; a 
 difference of which the cause is obvious. Public opinion set 
 these arts at an immense distance from each other : glory was 
 associated with the former, but the latter were confounded with 
 servile labours. 
 
 This distinction was, in some measure, well founded. The 
 painter, the statuary, the architect, stamped their genius on their 
 productions. Their arts did not each require a long series of 
 efforts for its advancement ; nor did it enrich itself slowly by 
 the casualties and experiments of ages. Imagination could 
 suddenly overleap the boundaries of time ; and the masterpieces 
 which appeared in rapid succession among the Greeks were 
 destined to become the admiration of posterity. 
 
 Yet this people, so ingenious, so sensitive, and so fertile in 
 great men, suffered themselves to be seduced in the distribution 
 of their esteem by tastes often frivolous. He who won a victory 
 in wrestling, pugilism, or the race, obtained crowns, and enjoyed 
 the greatest honours ; but the useful arts were degraded even 
 in the eyes of their philosophers. 
 
 Here we perceive one of the most striking characters which 
 distinguish the ancients from the moderns. The Greek philo- 
 sophers, occupied especially in speculations which might ensure 
 to them the homage of a people so prone to enthusiasm, re- 
 garded the useful arts as unworthy of their attention. This 
 contempt was inherited by the Romans. Pliny, in speakin^g 
 of dyeing, avowedly neglects to describe operations which do 
 not belong to a liberal art. Nec tingendi rationem omisissemus, 
 si unquam ea liberalium artium fuisset. 
 
 Ever since philosophy has taken observation for a guide, and, 
 abandoning the illusions of systems, has adhered to the study 
 of the phenomena of nature, and of the real properties to which 
 they owe their origin, it has followed the chain of the numerous 
 wonders which it has analyzed, in subserviency to the welfare 
 
 * Poetical arts would be here a juster expression ; for statuary is surely an art of 
 luxury. — T. 
 
HISTORICAL SUMMARY. 
 
 3 
 
 of society. It has recognized in manufacturing industry, as 
 well as in commerce, the source of the prosperity of the nation, 
 the germ of a great population, the principal support of agri- 
 culture. But it was the Academy of Sciences of Paris which 
 first sought to spread the light of science over all the arts, which 
 first formed the project of publishing their description, and 
 which, in the midst of prohibitory ordinances, arrived at this 
 truth, — That national industry was to be augmented and en- 
 lightened by a free communication of the processes which it 
 employed ; and that the sacrifices which it might make by this 
 publicity, are well recompensed by the advantages thence de- 
 rived. This project was extended to all the objects of our 
 studies, by the Encyclopaedia, the mightiest monument which 
 philosophy and reason have ever raised. 
 
 The art of dyeing must have felt feebly, w^e perceive, the 
 influence of learning among the Greeks. Yet the activity of 
 genius has something sympathetic, and industry multiplies her 
 trials when solicited by luxury. Let us observe, then, to what 
 point refinement had raised it in the prosperous days of Greece ; 
 let us consult the picture of it traced by Barthelemy. 
 
 A great proportion of the citizens of Athens passed their 
 time in the different tribunals, and received a salary of three 
 oboli, that is, fourpence halfpenny a-day. The average price 
 of the setier (twelve bushels of Paris) of corn, whose value is 
 the least uncertain standard of comparison, was thirteen French 
 livres, (lOs. lOd. English), that is, a little more than the half of the 
 medium price with us. A citizen of Athens could thus, with 
 the daily pay annexed to the most important functions of the 
 republic, purchase a measure of corn, which would at present 
 cost sevenpence halfpenny English. In order to form an idea, 
 therefore, not indeed of the public magnificence, nor of that 
 of some individuals, but of the ease and luxury of the ordinary 
 class of citizens, we must represent to ourselves what they would 
 be at Paris, if the salary of the public functionaries was fifteen 
 sous (sevenpence halfpenny) a-day. 
 
 ^* Many of them (the Athenians) went barefooted. The 
 common people were clad in cloth which had received no dye, 
 and which could therefore be re-whitened. The rich preferred 
 coloured clothes they held in considerable estimation those 
 
 * Voyage de jeune Anacharsis. 
 B 2 
 
4 
 
 HISTORICAL SUMMARY. 
 
 which had been dyed scarlet, by means of small reddish grains, 
 and in still higher those of a purple dye." 
 
 Silk, which is subjected to the most varied processes of dye- 
 ing, comes originally from China. . It was, say the Chinese 
 annals, the wife of the emperor Hoang-ti who first engaged in 
 spinning the cocoons which are naturally found on trees. Silk 
 was carried thereafter into Hindostan, and thence into Persia, 
 Greece, and Rome. But it arrived here at a very late period. 
 Some have concluded, from a verse in the Georgics of Virgil,* 
 that its use was known at Rome in the time of Augustus. We 
 find less doubtful indications in Pliny. Silk bore still so high 
 a price in the time of the emperor Justinian, that it was sold 
 for its weight of gold.f Lastly, some monks brought from India 
 to Constantinople eggs of the silk-worm, and established there 
 the method of rearing them, and of spinning the down of their 
 cocoons. J 
 
 It appears to have been in the time of the Crusades that silk- 
 worms were introduced into Italy. 
 
 The axt of dyeing webs seems to have been unknown in Greece 
 before Alexander's invasion of India. Pliny relates, that the 
 sails of his vessels were there dyed of different colours. Hence 
 the Greeks possibly borrowed this art from the Indians. 
 
 India is indeed the nursery of that knowledge and those arts 
 which were subsequently diffused and improved among other 
 nations. Fortunate accidents might be readily multiplied in a 
 country rich in natural productions ; which requires little labour 
 to supply the subsistence of its inhabitants ; and whose popula- 
 tion was promoted by the profusion of nature, and the simplicity 
 of manners, ere the tyranny of those conquerors who have now 
 succeeded to it had committed its ravages; but religious preju- 
 dices, and the unalterable division of castes, soon shackled 
 industry. The arts have been thenceforward stationary in 
 India: and it would appear, that in the time of Alexander, 
 dyeing had attained nearly the same state as at present, in regard 
 to cotton goods ; for silk was still unknown there, or at least 
 very scarce. 
 
 The beautiful colours which we observe on the Indian goods, 
 
 * Vellemque utfoliis depectant tenuia Seres. — Georg. lib. ii. 
 
 t Voltaire, Essai sur les Moeurs, &c. 
 
 J Procop. lib. iv. cap. 17. De bello Gothico. 
 
HISTORICAL SUMMARY. 
 
 5 
 
 to which the name of Perses was originally given, because it was 
 through the trade of Persia that they first reached us, might 
 lead to the belief that the art of dyeing was there pushed to a 
 great degree of perfection. But we learn from the description 
 which Beaulieu gave, at the request of Dufay, of operations 
 performed in his presence,* that the processes of the Indians 
 are so complicated, tedious, and imperfect, that they would be 
 impracticable elsewhere, from the difference in the price of 
 labour. European manufactures soon surpassed them in correct- 
 ness of design, variety of shade, and simplicity of manipulation. 
 If they have not yet rivalled the vivacity of two or three of their 
 colours, this must be ascribed merely to the superiority of some 
 colouring substances, or perhaps to the very length and multi- 
 plicity of the operations. 
 
 We may therefore conclude, that the art of dyeing was less 
 extended and less improved among the ancients than among the 
 moderns ; but the former possessed a dye which has been lost or 
 neglected, and which was the most eagerly desired object of 
 luxury, — this was purple. Its processes have, however, been 
 better preserved in historical monuments, than those of any 
 other colours. 
 
 We shall not dwell on the tales with which it has been attempt- 
 ed to embellish the origin of the purple dye. There is a great 
 probability of the discovery having been made at Tyre, and that 
 it contributed much to the opulence of this celebrated city. 
 
 The liquor which was employed to dye the purple, was de- 
 rived from two principal species of shells. The larger bore the 
 name of \he purple; and the other was a species of whelk. Both 
 were subdivided into several varieties. They were further dis- 
 tinguished by the greater or less beauty of colour which they 
 could afford, and according to the coasts where the fishing was 
 carried on. 
 
 The colouring juice of the purples is contained in a vessel 
 which is found in the throat. Only one drop of liquid was ob- 
 tained from each shell-fish. The whelks were bruised : These 
 contained a very small quantity of a red liquor, verging on 
 black, {Nigricantis Rosce. — Plin.) 
 
 * "Traite sur les toiles peintes," in which we observe the manner of fahricating printed 
 calicoes in India and in Europe. The opinion given in the text is confirmed by the' more 
 exact detail found in Bancroft " on Permanent Colours." 
 
6 
 
 HISTORICAL SUMMARY. 
 
 When they had collected a certain quantity of the colouring 
 liquor, they added to it a proportion of sea-salt. They then 
 macerated for three days ; after which five times as much water 
 was added. This mixture w^as kept at a moderate heat, sepa- 
 rating from time to time the animal matters which rose to the 
 surface. These operations lasted ten days. They now tried, 
 with a little white wool, if the liquid had taken the proper hue. 
 The stuff* was subjected to different preparations before it was dyed. 
 Some passed it through lime-water ; others prepared it with a spe- 
 cies of fucus, which served, like some of our astringents, to render 
 the colour more durable. We do not know precisely the marine 
 plant to which the ancients gave the name of fucus ; but it was 
 of such extensive use in their dye-works, that the word became 
 a generic name for all kinds of colouring substances, (dye-stuffs.) 
 Pileur d'Apligny conjectures, that it might be a species of 
 archil or rocella^ which is found on the coasts of Candia;* 
 others, again, prepared the cloth with alkanet. 
 
 The juice of the whelk did not yield of itself a permanent 
 colour; but it increased the brilliancy of the colour of the other 
 shell-fish. The purple of Tyre was made in tw^o operations. 
 They commenced by dyeing with the juice of the purpvra ; 
 after this they gave it a second dye with the juice of the whelk, 
 whence Pliny calls it purpura dihapha. In other processes, the 
 liquors of two species of shell-fish were mingled ; thus, for 110 
 pounds of w^ool, 440 pounds of the liquor of the whelk, and 
 220 pounds of that of the piirpura were taken. An amethyst 
 colour was thereby obtained. Sometimes a body or basis was 
 given with the coccus, which is our kennes, and after that the 
 dye was completed with the juice of the purpura. Finally, 
 they combined some of the preceding methods, and thereby 
 obtained a great variety of purple hues, which were distin- 
 guished by different names. That of Tyre possessed, according 
 to Pliny, the colour of coagulated blood ; the amethyst purple 
 had that of the stone so called ; another species resembled 
 violet, &c.f 
 
 * Essai siir les moyens de perfectionner Tart de la teinture. 
 
 f Those who wish to acquire more extensive information on the purple of the ancients 
 may consult among the moderns the following works : — " Fabii Colomni lyncsei purpura;" 
 ' G. Gottl. Richter, Progr. de purpurse antiquo et novo pigmento;" " Reaumur, Mem. 
 de Pacademie, 1711;" and especially a learned work by M. Bischolf, entitled, "Versuche 
 einer Geschichte der Faberkunst, &c. 1788." 
 
HISTORICAL SUMMARY. 
 
 7 
 
 It seems that some kinds of purple preserved their colour a 
 very long time : Plutarch relates, in the life of Alexander, that 
 the Greeks found in the treasury of the king of Persia a great 
 quantity of purple, of which the beauty was not affected though 
 it was 190 years old. 
 
 The very small quantity of liquor which was extracted from 
 each shell, and the length of the dyeing process, gave to the 
 purple so high a price, that, in the time of Augustus, a pound 
 of wool dyed in Tyrian purple could not be had for less than 
 1000 denarii, about 700 French livres, (£28 sterling.) 
 
 The priests, who sought always to take advantage of what 
 might make an impression on the people, attributed, in early 
 times, a sacred character to the purple. It was a colour pleasing 
 to the Deity, and which must be reserved for his worship. 
 Although the purple has been lost for a long time, the pride 
 of the name has been preserved in our sacerdotal hierarchy. 
 
 Purple was almost every where an attribute of exalted birth, 
 and of dignities. It served as a decoration to the first magistrates 
 of Rome. But the luxury which was afterwards carried to 
 excess in this capital of the world, rendered the use of it 
 common to opulent individuals, until the emperors reserved 
 to themselves the privilege of wearing it. It soon became the 
 symbol of their inauguration. They appointed officers who 
 were charged with the superintendence of this dye in the 
 manufactories, where it was prepared for them alone, principally 
 in Phoenicia. The punishment of death was decreed against 
 all those who might have the audacity to wear purple, even 
 should they cover it with another dye. 
 
 The penalty annexed to this whimsical kind of high treason, 
 was undoubtedly the cause which made the art of dyeing purple 
 disappear, first in the West, and much later in the East, where 
 this art still existed in vigour in the eleventh century. 
 
 There was extracted from coccus, now known under the name 
 of kermes, (an account of which may be seen Sect. iii. Part 2,) 
 a dye, which was hardly less esteemed than the purple, and 
 which was sometimes associated with it, as we have already 
 mentioned. Pliny relates, that it was employed for the robes 
 of emperors. The name of scarlet was usually given to it ; but 
 it was sometimes confounded with purple. 
 
 It was only in the age of Alexander and his successors, 
 
8 
 
 HISTORICAL SUMMARY. 
 
 according to Pliny, that the Greeks sought to give some 
 perfection to black, blue, yellow, and green (dyes.) 
 
 Among the Romans, newly married women wore in the early 
 times a yellow veil. This colour was appropriated to matrons. 
 
 In the games of the circus, four parties were distinguished by 
 their colours : green, color prasinus ; orange, rufatus ; ash-colour, 
 venetus ; and white. 
 
 We may judge of the qualities of these colours by the sub- 
 stances which they employed. As Bischoff has made very 
 extensive researches on this subject, T shall give, after him, an 
 enumeration of the ingredients which entered into the art of 
 dyeing in those times, independently of the coccus and the 
 purple shell-fish. 
 
 1. Alum; but we may see in the first part of this work, 
 (Sect. V.) that very probably the ancients were not acquainted 
 with our alum in a state of purity. 
 
 2. Alkanet. Suidas relates, that the substance served like- 
 wise as a pigment for women. 
 
 3. The blood of birds, which was employed by the Jews. 
 
 4. The fucus. That of Crete was preferred. It was usually 
 employed to give a basis or ground to good colours. 
 
 5. Broom. 
 
 6. Violet. The Gauls prepared from it a colour which re- 
 sembled one species of purple. 
 
 7. Lotus medicago arborea. Snail trefoil, (Luzerne en arbre.) • 
 The bark served for dyeing skins, and the root was employed in 
 dyeing wool. 
 
 8. The bark of the walnut tree and the rind of the nut. 
 
 9. Madder. It is not known whether the madder of the ancients 
 be the same plant as ours, or some other root of the same family. 
 
 10. Woad. {Glastum,) This plant was certainly employed 
 by the ancients; but it is doubtful if they gave it the same 
 preparation as we do. 
 
 They made use of the sulphate of iron, and of that of copper, 
 for dyeing black, especially skins. Nut-galls, of which the most 
 valued came from Comagena, served as the astringent. They 
 used, as a substitute for it, the seeds contained in the pods of an 
 acacia peculiar to Egypt. They also employed the bark of 
 pomegranate and of some other astringents.* 
 
 * Ameilhoii, Mem. dc Plnstit. litter, et beaux arts, torn. iii. 
 
HISTORICAL SUMMARY. 
 
 9 
 
 Although the ancients may have used some substances of 
 which no memorial is preserved, it is easy to see that the acqui- 
 sitions which we have made, especially since the discovery of 
 America, give us a great superiority with regard to several co- 
 lours. But is the regret frequently expressed for the loss of 
 the purple well founded ? Are we not able to rival the beauty 
 ^ of this highly -famed colour ? 
 
 The shell-fish which furnished the colouring liquor of the 
 purple, exist probably in as great abundance as formerly. They 
 have been sufficiently characterized to enable us to recognize 
 them. In fact, Thomas Gage relates that there was found near 
 Nicoya, a small Spanish town of South America, shell-fish pos- 
 sessed of all the properties described by Pliny and the other 
 ancient writers. It appears, even, that some use was made of 
 these shell-fish for dying cotton on the coasts of Guayaquil and 
 Guatimala.* Cole discovered some of them in 1686 on the 
 English coasts ; Plumier found a species of them at the An- 
 tilles ; Reaumur made several experiments on the huccinum 
 which he found on the coasts of Peru ; Duhamel made also 
 several on the colouring juice of the shell-fish which bears the 
 name oi purpura, which he found in abundance on the coasts of 
 Provence. He observed that this juice assumes a purple colour 
 only by the action of light, as Reaumur had already remarked 
 respecting the colouring juice of the huccinum ; that this juice, 
 at first white, assumes a yellowish-green colour, which deepens, 
 verging on blue ; that, finally, it is seen to redden, and in less 
 than five minutes to become of a very vivid deep purple colour. f 
 Now, the purple of the ancients possessed these characters. 
 
 Moreover, we have a very detailed description of the manner 
 in which the fishing was conducted of the shell-fish which served 
 for purple, in a work of an eye-witness, Eudocia Macremboli- 
 tissa, daughter of the emperor Constantine VII I., who lived in 
 the eleventh century.;]: 
 
 Our indifference, therefore, in procuring the purple, and in 
 
 * Histoire philosophiqiie et politique dii commerce des Indes, liv. viii. 
 t Mem. de TAcad. 1736. 
 
 J Eudocia Macrcmbolilissa was married to a Constantine, and after his death to Ro- 
 manus III., who was elected emperor in 1068. Her work is to be found in a collection 
 published by M. d'Ansede Villoison, under the title of" Anecdota Grseca h regia parisiensi 
 et ^ veneta S. Marci bibliothecis deprompta, T, i. IZSl." 
 
10 
 
 HISTORICAL SUMMARY. 
 
 profiting by the researches which some moderns have success- 
 fully made, probably proceeds from our having acquired more 
 beautiful and less costly colours. Many learned men are of 
 this opinion.* 
 
 In fact, the kermes afforded a colour which was esteemed by 
 the ancients as almost equal to the purple (purpura,) and which 
 contributed to that distinguished by the name of color hysginus. 
 Now, we understand the management of the kermes in probably 
 a more advantageous manner than the ancients did, because we 
 possess a pure alum, which disposes the stuff to receive a finer 
 and more permanent colour ; and yet our dyers have been 
 obliged to renounce its use almost entirely, notwithstanding the 
 solidity of its colour, because it cannot, in point of beauty, bear 
 a comparison with the colours now produced from cochineal. 
 
 Supposing the slight difference which may exist between the 
 colour of the kermes, and that of the purple of Tyre, to be 
 compensated by the advantage which we derive from our alum, 
 we might regard this purple, which was so precious that the 
 Cassars reserved it to themselves under penalty of death, to be 
 similar to that blood-red which we observe in ancient tapestries, 
 for the production of which kermes was employed. 
 
 The supposition, that the colour which we derive from kermes 
 is preferable to that w^hich the ancients obtained from it can 
 be supported by the testimony even of Pliny ; for he insinuates 
 that it had little permanence ; but the colour which is now 
 given by means of kermes, to wool prepared with alum, is of the 
 greatest durability. 
 
 Soap, the discovery of which is ascribed to the Gauls, appears 
 to have had no other use among the ancients than that of a po- 
 made for cleansing the hair, or for staining it with any colours 
 which they chose to mix with it.f This substance is, how- 
 ever, of such utility, that it must give us a superiority in 
 bleaching, and in some parts of dyeing. They supplied its use, 
 in the scouring of wool and whitening of cloth, by a plant which 
 Pliny calls radicula, which was termed struthion by the Greeks, 
 and which some consider as our saponaria ; as also by another 
 plant, which Pliny designates as a species of poppy. Homer 
 
 * Bisclioff, Vcrsuclie, &c. Goguet, de Torigine des lois, arts, et des sciences, 2 partie, 
 liv. ii. 
 
 f Goguet, Ibid, premiere partic, liv. ii. Ameilhon, Mem. dc I'lnstit. torn. ii. 
 
HISTORICAL SUMMARY. 
 
 11 
 
 paints the princess Nausica and her waiting-maids treading 
 their dresses with their feet in ditches in order to bleach 
 them. From other evidence we learn that wood ashes were 
 mingled with them ; and also, that some earthy boles were em- 
 ployed. 
 
 We have acquired from the New World several dye-stuffs, 
 cochineal, Brazil wood, logwood, annotta. We owe the su- 
 periority of our dyes especially to the preparation of alum 
 and to the solution of tin, which lends such lustre to se- 
 veral colouring substances. Silk, which has become so com- 
 mon with us, and which takes such lively and brilliant dyes ; 
 the rapid movements of commerce, which place the produc- 
 tions of China and the Indies within the enjoyment of even 
 the common people ; an active and enlightened industry, stimu- 
 lated by the rivalship of the different nations of Europe, who 
 endeavour to counterbalance their instruments of power ; all 
 these circumstances set an immense interval between the luxu- 
 ries most familiar to us, and those of the most opulent indi- 
 viduals among the ancients. Europe, however, before acquiring 
 this superiority, experienced all the devastations of barbarism. 
 
 In the fifth century the arts became extinct in the West ; 
 soon thereafter, almost every trace of intelligence, reason^ 
 humanity, and industry, disappeared. A few decayed arts, 
 indeed, were preserved merely in Italy. Muratori quotes a 
 manuscript of the eighth century,* in which we find some de- 
 scription of dyes, chiefly for skins, and some processes of 
 the other arts ; but the Latin, which is almost unintelligible, 
 and some chasms in the writing, prevent us from forming a just 
 idea of these processes. f 
 
 The arts were better preserved in the East, whence were 
 derived, till the twelfth century, the objects of luxury which a 
 few of the great were able to procure. During the Crusades, 
 the Venetians reared their power on the frenzy of the age : 
 their fleets took charge of the victualling of our fatal emigrations ; 
 their commerce became enriched ; the arts were established 
 among them, enlightened by the manufactures of the Greeks ; 
 and from this city they were propagated into the other parts 
 
 * Diss, de textrina et vestibus sseculor. rudium antiq. ital. vol. ii. 
 
 i* I shall quote literally a description of alum, which seems to prove, that only aluminous 
 stalactites, or a volcanic earth impregnated with alum, was used. " De Alumen. Alumen 
 autem metallum, est terra floricns de eri^arin. Eritarin terra est alba, facilis ad pisandum." 
 
12 
 
 HISTORICAL SUMMARY. 
 
 of Italy. In 1338, 200 manufacturers were employed in Flo- 
 rence, who fabricated, it was said, from 70,000 to 80,000 pieces 
 of cloth, forming an object of commerce worth 1,200,000 golden 
 crowns. 
 
 The discovery of rocella was accidentally made by a merchant 
 of Florence, about the year 1300. Having remarl^ed that urine 
 gave a fine colour to a species of moss, he made experiments, 
 and learned to prepare archil. He kept this discovery secret 
 for a long time. His descendants, of whom a branch still 
 remains, according to the report of Dominique Manni, have 
 retained the name of Ruccelai^ from the Spanish word oreiglia, 
 which that species of moss bore. 
 
 The arts long continued to be cultivated in Italy with increas- 
 ing success. In 1429 appeared at Venice the first collection of 
 processes employed in dyeing, under the name of Mariegola 
 delV Arte de Tentori, A second edition of it, much enlarged, 
 was given in 1510. One Giovan Ventura Rosetti formed the 
 project of giving more extent and utility to this description. 
 He travelled into the different parts of Italy and the neighbour- 
 ing countries, where the arts had begun to revive, to learn the 
 processes which were there pursued ; and he published, under 
 the name of Plictho, a collection, which, according to Bischoff*, 
 is the first wherein the different processes were assembled, and 
 which must be regarded as the primary impulse towards that 
 perfection which the art of dyeing has since reached.* 
 
 It is to be remarked, that in the work of Plictho there is no 
 mention made of either cochineal or indigo ; so that in 1548 
 these two colouring substances were probably not yet employed 
 in Italy. Pliny indeed speaks of a substance which came from 
 India, and to which the name of Indicum was given ; but no 
 use was made of it except for painting. It is, however, very 
 probable that the Indians used it in dyeing ; it appears, even, 
 that the first which was employed in Europe was brought from 
 the East Indies by the Dutch. The cultivation of it was first 
 established in Mexico, and thence in the other parts of America, 
 
 * " Plictho deir arte de tentori, che insegna tenger panni, tele banbasi e sede, si per 
 Parte magiorc, come per la comune. Venezia, 1548." This work has been translated 
 into French under the title of " Suite du tenturicr parfait, ou Tart de teindre les laincs, 
 soies, fils, peaux, poils, plumes, &c. comme il se pratique a Venise, G^nes, Florence, et 
 dans tout le Levant, et la maniere de passer en chamois toute sorte de peaux ; traduite 
 de Titalien. Paris, 1716." 
 
HISTORICAL SUMMARY. 
 
 13 
 
 where it has acquired qualities superior to what comes to us 
 from India.* 
 
 For a long time Italy, and particularly Venice, possessed 
 almost exclusively the art of dyeing, which contributed to the 
 prosperity of their manufactures and their commerce ; but by 
 degrees this art was introduced into France. Giles Gobelin 
 made an establishment in the place which bears his name. This 
 enterprise was regarded as so rash, that the name of Gobelins 
 Folly was given to the establishment ; and the success which it 
 obtained so astonished our ancestors, that they believed Gobelin 
 had entered into a compact with the devil. 
 
 The discovery of the scarlet dye may be regarded as the most 
 remarkable era in the art of dyeing ; not only by the lustre 
 wdiich distinguishes it, but also by the brilliancy which we can 
 impart, by means of the same process, to several other colours. 
 We have seen that the ancients gave the name of scarlet to the 
 colour which they obtained from kermes, and which was very 
 inferior in beauty to what we designate by the same appellation. 
 
 Some Spaniards having observed that the inhabitants of 
 Mexico made use of cochineal for colouring their houses and 
 dyeing their cottons, informed the ministry of the beauty of 
 this colour ; and Cortes received, in 1 523, an order to promote 
 the multiplication of the precious insect which produced it. The 
 colour which cochineal gives naturally is, however, a rather dull 
 crimson. 
 
 A little while after the cochineal became known in Europe, 
 the scarlet process, by means of the solution of tin, was dis- 
 covered. It is stated, that about 1630 Cornelius Drebbel ob- 
 served, by an accidental mixture, the brilliancy which the 
 solution of tin gave to the infusion of cochineal. He com- 
 municated his observation to his son-in-law, Kuffelar, who was 
 a dyer at Leyden. He soon improved the process, kept it secret 
 in his workshop, and brought into vogue the colour which bore 
 his name.f 
 
 Soon thereafter, a German chemist, called KusteVy Kuffler^ 
 or Kepjler, found out also the scarlet process by means of the 
 solution of tin. He carried his secret to London in 1643. A 
 
 * The indigo imported into Great Britain from Calcutta now, is in general superior to 
 the South American. — T. 
 
 -f Grundriss der Farhekunst. Sigismond. Friedrich Hermstadt. 
 
14 
 
 HISTORICAL SUMMARY, 
 
 Flemish painter named Kloeck or Jean Glucq, procured the 
 knowledge of it, and entered into partnership with a family of 
 the name of JuUienne^ the last of whom died in 1767.* This 
 process was subsequently diffused over Europe. Kloeck tra- 
 velled in the East, which, since the time of the Greeks, had 
 preserved a remnant of manufactures ; and he naturalized in 
 Flanders the art of dyeing on wool and silk, which flourished 
 there for a long time. M. Francheville fixes the death of this 
 man, who was so useful to his country, towards the year 1550.f 
 
 The employment of indigo, which has been likewise a great 
 acquisition to the art of dyeing, experienced more difficulty in 
 its establishment than that of cochineal. It was severely pro- 
 hibited in England under the leign of Elizabeth, as well as 
 logwood, which was ordered to be burned whenever it was found 
 in a manufactory. This prohibition was removed only in the 
 reign of Charles IL 
 
 The use of indigo was equally proscribed in Saxony. It was 
 treated in the ordinance issued against it (which reminds one of 
 the decree against tartar emetic,) as a corrosive colour, and food 
 for the devil. Fressende Teufels.% 
 
 This is a grand example of the abuses into which an un- 
 enlightened administration, easily misled by the suggestions of 
 personal interests, may fall. The blue dyers, who were in pos- 
 session of the process with pastil and woad, represented that 
 indigo would ruin the commerce of these two substances, which 
 were native productions. This motive, which would be still 
 specious in the eyes of several persons, readily determined the 
 issuing a prohibition, which was soon to be eluded, at the 
 expense of paying a tribute to the industry of other nations. 
 The prejudice against indigo was also communicated to France ; 
 and in the Instructions of Colbert it is forbidden to put above 
 a certain proportion of it into the w^oad vats. 
 
 Colbert gave to French manufactures, which had remained 
 languishing under the stormy administrations of Richelieu and 
 Mazarin, an impulse which soon advanced them beyond the 
 progress of other nations. He called forth the most expert 
 artists ; he recompensed every talent ; he established several 
 
 * Notice sur la manufacture nationale de tapisserie des Gobelins ; par Guillaumeau. 
 J Mem. de Berlin, 1767. 
 f Bischoff, Versuche, &c. 
 
HISTORICAL SUMMARY. 
 
 15 
 
 manufactories ; and it may be remarked, that those of Vaurobais 
 and Sedan were designated, in the letters-patent which were 
 granted them, under the name of fine cloths of Dutch and 
 English fabric. He published, in 1672, a code of instruction 
 for dyers, which merits attention.* 
 
 There are presented in this, first the motives which give im- 
 portance to the object under consideration : — If the manu- 
 factures of silk, wool, and thread, are those which serve prin- 
 cipally to sustain and give value to commerce, dyeing, which 
 communicates to them that beautiful* variety of colours which 
 makes them agreeable, imitating whatever is most lovely in 
 nature, forms the soul, without which the body would have but 
 a feeble existence. 
 
 *^ Wool and silk, which, in their natural colours, show rather 
 the rudeness of the age, than the genius of man, and the refine- 
 ment of our days, would command but a moderate trade, if 
 dyeing did not -impart to them that elegance which makes them 
 be sought after and desired even by, the most barbarous nations. 
 
 " All visible objects are distinguished or rendered desirable 
 by their colours, which must be not only beautiful to give com- 
 mercial currency to the stuffs, but also good, that their durability 
 be equal to that of the fabrics to which they are applied." 
 
 In placing alongside of several salutary regulations, instructions 
 for cultivators and artists, Colbert did homage to that feudal 
 spirit, which multiplying with fiscal views the shackles of com- 
 merce, manufactures and agriculture, had impressed throughout 
 nearly the whole of Europe the idea of regarding these bonds 
 as indispensable. Instead of restricting himself to measures 
 which should serve to guarantee the fidelity of the fabrics and 
 the goodness of the colours, — instead of developing the germ 
 of that honour which belongs to commerce, and which promotes 
 its interest, he pushed the prohibitory regulation to the point 
 of requiring, that the dyeing of black cloth should be begun by 
 the dyers in the grand tint, and finished by the dyers of the 
 little tint. — ( Teinturiers en grand teint, et en petit teint.J The 
 
 * " Instruction generale pour la teinture des laines et manufactures de laines, de toutes 
 nuances, et pour la culture des drogues ou ingredients qu'on emploie." This work was 
 reprinted in 1708, under the following title: — " Le teinturier parfoit, ou instruction nou- 
 velle et generale pour la teinture des laines et manufacture de laine de toutes couleurs, et 
 pour la culture des drogues ou ingre'dients qu'on y emploie." 
 
16 
 
 HISTORICAL SUMMARY. 
 
 former were allowed to have in their possession only a certain 
 number of ingredients, while the latter were also restricted to 
 a certain number. Neither the one nor the other were per- 
 mitted to have Brazil wood, &c. It is true, indeed, that the 
 sad effects of these prohibitions were tempered by the facility 
 of evasion, as well as by the premiums awarded to those who 
 made some advancement in their art, and whose discoveries being 
 subsequently communicated to the public, produced modifications 
 in the regulations. French manufactures lost their pre-emi- 
 nence by the revocation of the edict of Nantes, which scattered 
 them over the rest of Europe, leaving desolation in our factories. 
 
 Since this period, the department of administration charged 
 with the superintendence of our arts and manufactures, has 
 been constantly occupied with the means of repairing our losses, 
 and of making our industry flourish. It- has employed that 
 plan in particular, which, with a judicious liberty, is the most 
 efficacious of all, viz. the diffusion of instruction and scientific 
 knowledge. 
 
 Dufay, Hello t, Macquer, were, in succession, charged with 
 the duty of presiding over the art of dyeing ; and to their 
 labours we owe valuable improvements. Dufay was the first 
 who formed sound, though incomplete ideas, on the nature of 
 the colouring particles, and on the forces by which they adhered 
 to cloth. He examined some processes with sagacity, and 
 established the surest tests which could at that time be formed, 
 for determining in a ready and practical manner the goodness of 
 a colour. Hellot published a methodical description of the 
 processes which are practised in the dyeing of wool, which 
 forms still the best treatise we possess on this subject. Mac- 
 quer gave an exact description of the processes executed in 
 silk: he made known the combinations of the colouring prin- 
 ciple of Prussian blue ; he tried to apply its use to dyeing ; 
 and he furnished a process for imparting to silk brilliant 
 colours by means of cochineal. 
 
 The soHcitude of administration has had, in the judgment of 
 foreigners, the success which it deserved. Anderson ascribes to 
 the perfection of our dyes the superiority which some French 
 manufactures have preserved over those of the nations which 
 possess the finest wools;* and Home thus explains himself: — 
 
 * History of Commerce. 
 
HISTORICAL SUMMARY. 
 
 17 
 
 It is to tli8 Academy of Sciences that the French owe the 
 superiority which they enjoy in several arts, and especially in 
 that of dyeing."* Several distinguished philosophers, indeed, 
 have followed with equal success the example set by the Aca- 
 demy of Sciences. 
 
 Macquer had undertaken to pubHsh general treatise on 
 dyes, of which he gave the prospectus in 1781; but the languor 
 which for a long time announced his dissolution, prevented him 
 from executing it. He who replaced Macquer in the adminis- 
 tration of commerce, endeavoured, in the first edition of these 
 Elements, to connect the theory of the phenomena presented by 
 the art of dyeing, with the great discoveries which had effected 
 at that period a revolution in chemistry; to make the application 
 of it to the practice of this art ; and to pave the way for a new 
 career of advancement, by a more exact analysis of the proper- 
 ties of the substances which serve as agents in dyeing, or which 
 have relations with the qualities of colours. 
 
 * Essay on the Bleaching of Cloth. 
 
 C 
 
THE AUT OF DYEING^ 
 
 PART T. 
 OF DYEING IN GENERAL, 
 
 SECTION L 
 
 OF THE GENERAL PROPERTIES OF COLOURING SUBSTANCES. 
 
 CHAPTER L 
 
 Of the Theory of Colours, and of the distinctive Properties of 
 Colouring Particles, 
 
 The physical theory of colours may appear foreign to a work, in 
 which we are to consider only the properties which distinguish 
 them, in reference to the agents which are employed in their 
 application to the stuffs which receive them, and to the circum- 
 stances which produce in them changes or modifications. It 
 may however be interesting and possibly useful to the discus- 
 sions on which we are about to enter, to establish a connexion 
 between the phenomena which the colouring substances produce, 
 and those which the great Newton has analyzed in his '^Optics." 
 
 We shall begin, then, by examining if the theory of Newton, 
 concerning the colours assumed by transparent liquid or solid 
 bodies, such as air, water, glass, according to the difference of 
 tenuity of the plates which they form, and according to their 
 respective density, can be applied to bodies constantly coloured, 
 such as the colouring substances which are the objects of 
 dyeing. 
 
 In order to represent the ideas of Newton, and the conse- 
 
 c 2 
 
20 
 
 BERTHOLLET ON DYEING 
 
 quences to be drawn from his observations, we shall enjoy the 
 advantage of being guided by the treatise of Haiiy, where phy- 
 sical knowledge is concentrated with equal elegance, clearness, 
 and precision.* 
 
 In proportion as the transparent parts of bodies vary in 
 size," says Newton, they reflect the rays of one colour, and 
 transmit the rays of another colour, for the same reason that 
 thin plates and bubbles reflect the light, or transmit those rays ; 
 now, this is the principle of the uniform colours of all bodies. "f 
 Newton, however, supported this induction merely by the 
 experiments which he made on colourless substances. Delaval 
 endeavoured to discover proofs of it in the operations which 
 chemistry causes bodies to undergo, and in those of the art of 
 dyeing.^ Some doubts had been offered about this application 
 of the theory of Newton, in the first edition of this work; 
 since which time Bancroft has opposed to it a great number of 
 facts. § We shall avail ourselves of these several observations 
 in the discussion which we are about to undertake, solely in the 
 view of recalling to this interesting object the attention of those 
 who can follow the traces of Newton. We must begin by form- 
 ing an exact idea of the opinion which it is proposed to examine. 
 
 In every body the particles are separated from each other 
 by small interstices, which we call pores, and which contain 
 different subtile fluids. These particles having a determinate 
 thickness, repel the rays, which in penetrating them, are found 
 in a fit (retour) of easy reflection, and the body thus assumes 
 the colour, either simple or mixed, analogous to that of the 
 reflected rays, and which depends on the degree of tenuity of 
 the particles. 
 
 In fact we have seen, that coloured rings are produced in 
 the plates of solid bodies, as well as in those of liquids or fluids ; 
 and since every little space comprised in one of these plates 
 reflects or refracts the light, it follows, that if this plate were 
 
 * Traits ^l^mentaire de physique, tome ii. 
 f Optic, lib. ii. part. 3. prop. 5. 
 
 X " Experimental Inquiries of the cause of the changes of colours in opaque and natu- 
 rally coloured bodies." " Letter to the earl of Morton, on the relation between the 
 specific gravity of several metals and their colours." This last work was honoured, in 
 1765, with a medal by the Royal Society. 
 
 § Experimental Researches concerning the philosophy of permanent colours. 
 
IN GENERAL. 
 
 21 
 
 divided into a multitude of small fragments, eacli of these would 
 still produce the same effect as when it was in continuity with 
 the others. Now, as the particles of a body may be likened to 
 the separated fragments of a plate, whatever may be said of this 
 plate is exactly applicable to them also. 
 
 In speaking of the particles of bodies, it is not meant to 
 designate their smallest molecules, or those which we call integ- 
 rant molecules. In order to conceive what ought to be under- 
 stood by the particles which reflect the light, we may suppose, 
 with Newton, that the integrant molecules, already separated 
 from one another by the pores, form, by means of the union of 
 a certain number of them, other molecules of the second order, 
 separated by more extensive pores ; that these, in their turn, 
 compose molecules of the third order, with interstices always 
 more considerable ; and thus in succession. Now the particles 
 which reflect light in the ordinary state of a body, have a certain 
 thickness, whence result separations to a certain extent between 
 them : these particles are then considered as insulated, relatively 
 to the adjoining ones. The media which intercept them, namely, 
 the subtile fluids which occupy their pores, and the air which sur- 
 rounds their outer surface, perform the function of two glasses, 
 between which the plate of air in the experiment of Newton is 
 comprised ; for example, in a plate of mica of a perceptible 
 thickness, there are particles of a certain order, which possess 
 the property of reflecting the rays of a yellowish-white, and 
 these exist naturally at sufficient relative distances for the light 
 to act upon them, as if they existed alone. If we divide this 
 leaf into leaflets of a certain degree of tenuity, we insulate the 
 particles of another order, which will reflect other colours, as is 
 confirmed by observation. 
 
 " We have spoken, under the article divisibility, of a plate 
 detached from a piece of mica, whose degree of thinness was 
 such, that its primitive colour, which was yellowish-white, had 
 passed to the most intense blue." — Hauy^ 
 
 Yet, whatever tenuity be given to carmine or indigo, by 
 bruising, as Bancroft observes, the colour peculiar to each is not 
 affected. "We merely brighten it, by multiplying, according to 
 Monge, the surfaces which reffect the white. 
 
 It may, indeed, be replied, that these substances are composed 
 of homogeneous particles^ which, notwithstanding the greatest 
 
22 
 
 BERTHOLLET ON DYEING 
 
 division at which we can arrive, producing the same effect as 
 when they formed a continuity, whilst the mica has particles of 
 a certain order, which possess the property of reflecting the rays 
 of a yellowish-white ; while on dividing a plate into thin folia 
 to a certain degree of tenuity, we insulate the particles of 
 another order, which reflect the blue. 
 
 We shall here venture to offer some observations. 
 
 1. This manner of supposing mechanical arrangements, in 
 order to employ them in the explanations of physical properties, 
 without directly proving them, may easily serve to prop hypo- 
 theses otherwise entirely destitute of probability. 
 
 2* This supposition of particles of different orders, which 
 may reflect different colours in a homogeneous body, does not 
 accord with the opinion of Newton, who ascribed all the colours 
 obtained from plates of Muscovy talc, which is merely a mica> 
 to the thickness which he mechanically gave to these plates ; 
 and who compares these colours to those produced by soap bub*- 
 bles, according to the very variable thickness which they assume* 
 By this opinion, indigo and carmine ought certainly to afford 
 different colours, according to the tenuity of their parts ; but 
 we shall presently observe a circumstance, where it is difficult to 
 suppose that the particles of indigo preserve, along with their 
 colour, the same dimensions and the same density. 
 
 It is admitted, that a solvent must intervene in the dimensions 
 of the molecules which reffect the colours ; and this effect is 
 employed to explain some changes of colours produced by acids 
 and alkalies. We may easily explain, on the principles laid 
 down, the colours produced in certain liquors which are colour- 
 less, by the mixture of one of these liquors with the other, or 
 the changes of colour which a liquor naturally coloured suffers 
 in the same case* Thus, nitric acid dropped into alcohol, in 
 which an infusion of roses has been made too feeble to commu* 
 nicate any hue, developes instantly a colour similar to that of the 
 roses before infusion. The same acid, mingled with tincture of 
 litmus, changes the blue into a lively red. Syrup of violets 
 becomes green by the addition of an alkali. In all these mix- 
 tures, the union of the molecules of the two liquids forms 
 mixed molecules, whose thickness is different from that of the 
 component molecules, and occasions the reflection of the colour 
 analogous to this thickness.'* 
 
IN GENERAL. 
 
 23 
 
 Newton specifies more particularly the cause of the changes 
 of colour produced by acids and alkalies. It is known/' says 
 he, that saline menstrua are very proper for dissolving certain 
 substances, and it is also known, that some of them precipitate 
 what others dissolve ; and as it is the nature of acids to attenu- 
 ate and dissolve, and that of alkalies to thicken and precipitate, 
 if the colour of the syrup of violets were of the second order, 
 an acid liquid attenuating its particles would change this colour 
 into a red of the second order." 
 
 Delaval has also tried to explain the action of acids and 
 alkalies, by ascribing to the first the property of attenuating, 
 and to the second that of inspissating. Let us examine, there- 
 fore, if the properties of acids and alkalies, and those of the 
 solutions which they efiect, authorize these explanations. 
 
 If, in the effect which they produce, the union of the two 
 liquids forms mixed molecules, whose thickness is different from 
 that of the component molecules, and determines the reflection 
 of the colour analogous to this thickness, there must be a re- 
 markable difference in this respect between barytes, which has 
 a great specific gravity and a great fi^xity, and ammonia, which 
 is, on the contrary, specifically very light and of an elastic dis- 
 position : there ought to be found a similarity of effect between 
 some acids and some alkalies ; yet barytes and ammonia produce 
 the very same change. Sulphuric or phosphoric acid does not 
 act differently from carbonic acid, on the substances whose 
 colour they can alter. 
 
 The supposition advanced by Newton, that alkalies augment 
 the thickness of the molecules, and that acids attenuate, will 
 not appear well founded, to those who direct their attention to 
 the properties of the solutions of colouring substances in acids 
 or alkalies : the solution by alkalies properly presents, in the 
 greater number of cases, more decided characters of attenuation 
 than that which is due to acids, and it is for this reason that 
 they destroy, in dissolving them, the greater part of the colours 
 which have been fixed upon stuffs. It is only, therefore, for 
 explaining certain changes of colour, that to alkalies is assigned 
 a property which cannot be reconciled with observation. 
 
 We are now to examine a circumstance, where, notwithstand- 
 ing a great difference introduced into the density, and a great 
 attenuation of the colouring substance, this preserves unchange- 
 
24 
 
 BERTHOLLET ON DYEING 
 
 ably its colour. We shall confine ourselves to one example, 
 although we could adduce many of the same kind. It is from 
 indigo that we shall take it. If we dissolve indigo in sulphuric 
 acid, we may dilute the solution by successive additions of 
 water, so that it requires at least, according to the observation 
 of Bergmann,* twenty pounds of water in a cylindric vessel of 
 glass, seven inches diameter, to destroy the effect of the smallest 
 drop of the solution." 
 
 The molecules which always reflect the blue, ought however 
 to pass through all the dimensions which exist between that of 
 the solution of indigo, possessing much specific gravity, and that 
 of water ; they ought to suffer a greater and greater attenuation. 
 Further, we may substitute the acetic acid for the sulphuric, by 
 precipitating the latter with acetate of lead. A portion of the 
 indigo falls with the sulphate of lead. This precipitate, which 
 ought to have molecules much thicker, as well as the liquid 
 which holds the indigo in solution merely by means of the acetic 
 acid, possess equally the same blue colour. 
 
 Newton concluded from his observations, that the cor- 
 puscles which produce black, must be smaller than any of those 
 which produce other colours." — His theory appears to us to lead 
 even here to a result, which proves that a false application has 
 been made of it. In fact, ink consists of molecules, which are 
 a metallic compound in a state of precipitation, and which of 
 consequence, according to the very idea of Newton, are placed 
 in circumstances that announce the greatest compactness. If 
 we dilute it with much water, the black passes to blue or violet. 
 When the solution of indigo in sulphuric acid is much con- 
 densed, it appears absolutely black ; by dilution with water it 
 becomes blue; that is to say, by diminishing its condensation, 
 or by doing the contrary of what the theory requires. 
 
 Hitherto we have discussed the opinion on the supposition 
 that the colouring molecules act, by virtue of the form which 
 belongs to them, in the liquids in which they are in solution, as. 
 we see is stated in the following passage of Haiiy. '^With 
 regard to transparent and even coloured bodies, they seem to 
 offer a middle term between limpid and opaque bodies. Their 
 molecules reflect the rays of the colour under which they are 
 
 * M(^m. dcs Sav. dtr. torn. ix. 
 
IN GENERAL. 
 
 25 
 
 presented to the eye, and at the same time these bodies trans- 
 mit, throughout all their extent, other rays, which usually have 
 the same colour as the reflected rays. Thus the molecules situ- 
 ated at the surface reflect one part of the rays which arrive 
 at this surface, and transmit the rest ; other molecules situated 
 a little lower, reflect one part of the rays which have escaped 
 the first reflection, then transmit the others ; and thus in suc- 
 cession, to the last surface, where there still arrive a suffi- 
 ciently great number of rays passing into the air, to give the 
 body placed between the eye and the light a very sensible trans- 
 parency. It thence results, that the greater thickness the medium 
 has, the deeper is its colour, which agrees with observation. 
 
 This supposition will not accord with the opinion which we 
 must form of chemical combinations possessing liquidity, and in 
 which all the properties become common among all the parts by 
 their reciprocal action, whilst the equilibrium of the action is 
 not disturbed. The flgur.e which belongs to the different mole- 
 cules allows no influence to be perceived till they approach the 
 term where they must pass to the solid state : It is then, for 
 example, that Vv^ater, which tends to congeal, acquires an expan- 
 sion due to the effort which it makes, in order that its mole- 
 cules, in losing their liquidity, may assume an arrangement 
 determined by their surfaces. 
 
 Experiments made by Delaval appear to prove, that the 
 eff'ects attributed to the distinct parts of the colouring sub- 
 stances in solution, do not depend on their individual reflection. 
 He filled a flask, of a square form, with a coloured liquid, after 
 having covered three of its sides and the bottom with a black 
 paint ; and he observed, on looking to the liquid by the free 
 face, which formed a right angle with his window, to prevent 
 the reflection from the posterior surface, that the above liquid 
 appeared black, whatever might be its proper colour. Glasses 
 having the same form, and differently coloured, equally appeared 
 ^lack when they were covered with a black cloth, with the ex- 
 ception of one face which was left free, to admit the incident 
 light. If their mass be considerable, they thus also appeared 
 black ; but their fragments applied to a white ground, exhibited 
 the colour peculiar to them."* 
 
 * Mem. of the Liter, and Pliilos. Soc. of Maiicliester, vol. ii. 
 
26 
 
 BERTHOLLET ON DYEING 
 
 He thence concludes, that coloured liquids and glasses are 
 seen in their proper colours only by rays reflected from their 
 posterior surfaces ; so that it is the rays which have traversed 
 the coloured liquid or glass, which give the sensation of colour 
 by transmission or reflection. 
 
 He makes a remark, whose application is found in this place* 
 
 If a small quantity of colouring substance is mixed with a 
 medium which has no colour, the mass appears dyed with the 
 colouring substance. But if we add a great quantity of this 
 colouring matter, the mass appears black; consequently, in 
 ascribing to the colouring substance the power of reflection, we 
 advance a contradictory and inexplicable proposition ; for we 
 affirm, that the more of the substance, having the power of 
 reflection, the incident light encounters, the less light is re- 
 flected; so that if the colouring substance be very abundant, 
 there is no longer any colour but a black." 
 
 In order to extend this theory to opaque coloured bodies^ 
 Delaval supposes that they are always composed of two sub- 
 stances, one of which is white, and the other, which is coloured^ 
 possesses transparency, so that the rays of a certain colour 
 which traverse it, are reflected by the white surfaces that they 
 meet. When white molecules do not separate those which are 
 coloured, it is enough if there be present any medium whatever 
 possessed of a different density ; as Newton has shown that two 
 transparent substances, of a widely different density, produce an 
 opaque body* Delaval thus explains the colour of gold and 
 metallic oxides. 
 
 This explanation is very specious, and satisfies the greatei" 
 number of observations. Nevertheless its application appears 
 to us too general, because it requires us to suppose, between 
 the coloured molecules of the metals, the existence of a medium^ 
 which the other properties do not indicate, and because other 
 causes may produce the effect here ascribed to it. 
 
 In recapitulating what has been said, we find, that in order 
 to explain the different phenomena presented by coloured bodies, 
 1st, we consider, in a general manner, the colouring molecules of 
 a body as insulated^ relatively to those which adjoin them, and 
 the media which are interposed ; viz, the suhtile fluids lohich 
 occupy their pores, and the air surrounding their exterior surface, 
 
IN GENERAL. 
 
 27 
 
 as two glasses, between which is comprised the plate of air, as in 
 the experiment of Newton, 
 
 2* It is admitted, however^ that in the solutions which expe- 
 rience changes of colour by the action of acids and alkalies, the 
 union of the molecules of the two liquids forms mixed molecules, 
 whose thickness is different from that of the component mole-= 
 cules, without explaining the uniformity of effect of those acids 
 and alkalies which differ most in their specific gravity, fixity, 
 and volatility. 
 
 3. It is presumed, on the contrary, that in the solutions^ 
 combinations, and precipitations, where the substances preserve 
 the same colour, there occurs no alteration in their dimensions, 
 applying to the colouring parts the theory of No. L, although 
 the state in which they exist be equally the effect of a reciprocal 
 action, and although there be equally a combination. 
 
 4. In all the cases of transparency, the colouring molecules 
 are supposed to act individually on the rays of light ; and ex-^ 
 periment seems to prove, that the reflection of bodies which are 
 not opaque, takes place only at their anterior and posterior faces. 
 
 The effects observed in the solution of water in air, and in it^ 
 precipitation, appear to us capable of illustrating the properties 
 of solutions relatively to light. 
 
 When damp air has been compressed in a globe, according to 
 the experiment of Kratzeinstein related by Saussure,* and when 
 We restore the freedom of communication^ this air^ which, placed 
 between the eye and the light, exhibited at first only a pure" 
 transparencj^, causes vapours to be perceived, which have the 
 colours of the rainbow at the moment when the compression 
 is removed ; and it resumes its transparency by a new com- 
 pression. 
 
 This phenomenon is not difficult to analyse. When the air, 
 saturated with humidity in a state of compression, is suddenly 
 liberated, it produces by its dilatation a degree of cold, which 
 causes the precipitation of a part of the water which it held in 
 solution. Compression produces a contrary effect, by the heat 
 which accompanies it.f Saussure remarks that the phenomenon 
 due to the Vapours lasts only an instant, because the temperature 
 becoming fixed, the state of solution becomes equally so. 
 . Light, then, experiences no peculiar reflection or refraction 
 
 * Essai sur rhygrom. sect. 209. t Stat. chim. torn. i. p. 163. 
 
28 
 
 BERTHOLLET ON DYEING 
 
 from the water or air while the solution exists ^ and it is only 
 when these two elements acquire a peculiar existence that this 
 effect begins. Is it not natural to ascribe to other solutions 
 what is here observed in that of water ? On the other hand, 
 can we compare the constant properties of coloured substances 
 with the variable and transient effects owing to the refraction 
 and reflection of the molecules in simple juxta-position ? 
 
 Delaval made a great many experiments to prove, " that the 
 more considerable the density of constantly coloured bodies is^ 
 the greater also is their power of reflection (every thing else 
 being equal) for reflecting the least refrangible rays; that, on 
 the contrary, when they have less density, they can proportion- 
 ally reflect only the less refrangible rays ; and consequently they 
 must exhibit different colours, according to the order of their 
 density." 
 
 He makes choice particularly of metallic bodies to prove, 
 
 that they differ as to colour, exactly in the same gradation a& 
 in density ; the densest body being red, that which is immedi- 
 ately of a less density being orange-yellow," &c. 
 
 A little attention, however, is sufficient to convince us, that 
 there is no relation between the specific gravity of metals, or of 
 glasses coloured by their oxydes, and their colours. Delaval 
 regarded, with Newton, the solution of metals as a simple 
 division of their molecules, without regard to their oxydation, 
 the theory of which was then unknown, and on which princi- 
 pally depend the changes of colours in their solutions and oxydes. 
 To establish his opinion, and to make the peculiar colour of 
 every metal coincide with its specific gravity, he selected that 
 state of solution and oxydation which best suited his views. We 
 refer to the treatise of Bancroft for a detail of the facts hostile 
 to the opinion of Delaval. 
 
 Newton ascribed the colour of white metals to their exces- 
 sive density, by virtue of which they seem to reflect almost all 
 the incident light, unless, when dissolved in suitable menstrua, 
 they be thereby reduced into very small particles, when they 
 become transparent."* 
 
 If, from the density, we judge of the effect which silver ouglit 
 
 * The brilliant white of potassium and sodium, bodies of little density, seems adverse to- 
 this idea of Newton. — T. 
 
IN GENERAL. 
 
 29 
 
 to produce on light, its solution in nitric acid, which can take 
 up a great quantity of it, and can be diluted with water as much 
 as we please without decomposition, ought, in passing through 
 different densities, to acquire the property of reflecting different 
 colours. It remains, however, colourless and transparent, al- 
 though, according to the observation of Wollaston, the refract- 
 ing quality of the metallic solutions varies with their different 
 degrees of concentration.* It ought to tally with the density 
 and attenuation of the solutions or precipitates of cobalt, nickel, 
 and manganese, which, like silver, void of colour in the metallic 
 state, acquire it very intensely and very variously in their oxyda- 
 tion and precipitation. 
 
 The considerations now presented lead us to believe that we 
 ought not to confound the fugitive colours produced by the 
 reflection of plates, which follow the laws described by Newton, 
 with the colours which continue, notwithstanding the changes 
 of density and thickness. These appear to depend on pro- 
 perties, in which the peculiar affinity for the different rays of 
 light has an influence which resists that of the dimensions and 
 the density. On examining the facts, we perceive that con- 
 densed oxygen exercises a great power in this species of affinity. 
 A variable proportion of it, affecting in an insensible manner the 
 specific gravity of the metallic oxydes, produces in them great 
 changes of colour. In like manner, a little oxygen, conveyed 
 by muriatic acid to colouring substances, either makes their 
 colours disappear, or produces in them considerable alterations ; 
 whilst other combinations, for example that of alumina, which 
 precipitates the greater number of colouring substances in the 
 form of lakes, and which, according to the ideas of Newton and 
 Delaval, ought to give considerable density to these substances, 
 preserves meanwhile their proper colour, merely concentrating 
 it by the condensation which the earth occasions. 
 
 The very experiments of Newton prove, that the peculiar 
 affinity of different substances has a great influence on their 
 relations to the rays of light ; since, according to him, their 
 refractive power is proportional, not merely to their density, 
 but also to their inflammable disposition. This proposition 
 ought not to be taken with too great latitude ; for phosphorus, 
 
 * Phil. Trans. 1802. Ann. de chim. torn. xlvi. 
 
30 
 
 BERTHOLLET ON DYEING 
 
 which is very inflammable, has no great refrangency. It folic ws, 
 however, from the very observations on which the doctrine rests, 
 that there is a great difference of action, according to the affinity 
 of the bodies for the rays of light. 
 
 The interesting experiments of Dr. Blair likewise prove the 
 peculiar power of the aflSnity : — When light passes from any 
 medium whatever into a vacuum, the red rays are the least 
 refrangible, and the violet are at the other extreme ; but if 
 light passes from one medium into another, he shows, that it is 
 the quality or particular nature of these media that determines 
 which of these rays shall be the most refrangible, or if they 
 shall be equally so. The green rays occupy the middle of the 
 spectrum in the dispersion occasioned by crown glass ; they are 
 found among the least refrangible by the dispersive action of 
 flint glass ; but in muriatic acid these rays are found, on the 
 contrary, on the side of the violet or the most refrangible. It 
 thence happens, that the order of the colours is reversed in the 
 secondary spectrum, formed by a combination of crown glass 
 with the liquid.* 
 
 If we depart, in these considerations, from the consequences 
 to which physical observations have led — if we believe that we 
 must resist, in this particular, the authority of the great Newton, 
 and that of his illustrious interpreter, it is with regret ; for we 
 feel how important it is to connect all the effects due to the 
 reciprocal action of bodies, and we hope that future experiments 
 will flU up the space which here seems still to separate natural 
 philosophy and chemistry. Meanwhile, we shall conflne our^ 
 selves to the results of this last part of the science, which treats 
 of the properties of bodies. 
 
 In the metallic oxydes, and in several mineral substances, all 
 the parts are equally coloured ; but this is not the case with 
 vegetable or animal substances. The colour in the latter is 
 usually owing merely to particles, which are mixed or combined 
 with those constituting the bodies themselves ; and vegetables 
 contain sometimes different colouring molecules at different 
 periods of their growth, or in their different parts. 
 
 The colouring molecules of vegetable and animal substances 
 are almost the only ones employed for the purpose of dyeing ; 
 
 Bibliot. brit. torn. 8. 
 
IN GENERAL. 
 
 31 
 
 but they are often modified by the use of intermedia. Such 
 are the substances designated in this treatise by the name of 
 colouring particles. 
 
 These colouring particles do not exhibit, in their composition, 
 the simplicity of mineral substances, nor does oxygen affect 
 their colours in the same way. We shall examine, in one of 
 the following chapters, in what manner this principle acts upon 
 them so as to alter their nature. 
 
 Some chemists have regarded iron as the cause of all vegetable 
 and animal colours ; and Adolphus Becker employed, in support 
 of this opinion, considerations derived from the property which 
 this generally diffused metal possesses, of assuming a great 
 number of colours in the states of oxyde, solution, and vitrifi^ 
 cation,* 
 
 Iron, in fact, appears to be contained in all vegetable and 
 animal substances, but in extremely small quantity. Oak, one 
 of the vegetable substances which ought to yield the largest 
 residuum, leaves in its combustion only 1 -200th of its weight 
 of ashes ; and these ashes do not contain 1 -200th of iron. Can 
 the rich and splendid colours with which vegetables are ena- 
 melled be explained by so minute a proportion ? Is there in 
 reality any relation between the changeableness of some of these 
 colours, by acids, alkalies, and air, and the uniform succession 
 of colours which iron assumes according to its degree of 
 oxydation ? 
 
 The opinion which we are combating might indeed be sup- 
 ported by the suffrage of Bergmann, who supposed he had 
 proved that indigo owes its colour to the iron which it contains ;f 
 but we may be permitted to reply, that it is easy to show how 
 this great chemist had deceived himself on this subject. By 
 means of the alkaline prussiate, he obtained, from the ashes of 
 an ounce of indigo, from 30 to 32 grains of prussian blue ; and 
 he estimates the iron which this contains at 18 or 20 grains. 
 But in other places he proves, that the iron contained in a 
 substance forms at most but a fifth piart of the prussian blue 
 which we procure from its solution, and everywhere else he 
 employs this valuation. We must therefore reduce to six grains 
 
 * Specimen sistens experimenta circa mutationem colorum quorundam vegetabilium a 
 corporibus salibus, cum corollariis ; auctore J. F. Adolpho Becker, \779. 
 t Analyse chimique de Tindigo. Mem. des Savans etr. torn. ix. 
 
32 
 
 BERTHOLLET ON DYEING 
 
 the iron he obtained from an ounce of indigo. In the experi- 
 ments which follow the above, he proves, that the greater part 
 of this iron may be dissolved by muriatic acid, without the 
 colouring particles being affected ; so that the larger share of 
 this metal does not enter into their composition. From this it 
 clearly follows, that the colouring particles of this substance 
 must contain a quantity of iron so small, that can have but 
 little influence on its colour. 
 
 The means of chemical analysis which we possess are so far 
 from enabling us to determine the composition of the colouring 
 particles with sufficient precision for showing to what principles 
 they owe their properties, that we often observe a very different 
 composition giving rise to a colour of the same kind. The par- 
 ticles of indigo differ much from those which colour several 
 flowers blue. A great number of yellow substances afford 
 colours almost similar in appearance, which notwithstanding 
 differ much in their properties. 
 
 There are simple colours, and there are others arising from 
 the mixture of these colours, which are consequently compound. 
 Newton has given a general rule for forming any colour what- 
 ever, by means of other prismatic colours. Le Blond has proved 
 that we may procure all the colours which the art of the painter 
 can desire by the mixture of red, blue, and yellow.* Dufay 
 has shown that the same effect may be obtained in dyeing ; and 
 he has thence concluded, that there was in nature only three 
 primitive colours, which gave origin to all the rest. This 
 opinion has been embraced by several philosophers ; but it does 
 not appear to be sufficiently established. 
 
 Between simple colours and colours formed by the union, 
 of different rays, there is this difference : — the former, viewed 
 through the prism, retain their simplicity, while the latter are 
 decomposed. The green produced by the rays of this colour 
 suffers no decomposition by the prism. It has, therefore^ 
 the character of a simple and primitive colour. But the com- 
 pound green is separated into yellow and blue. 
 
 Although the green formed in dyeing results from a mixture 
 of blue and yellow, we must not consider all the greens as com- 
 binations of the two species of colouring particles. Thus, the 
 
 * L'Harmonie du coloris dans la pdinture, reduite en pratique. 
 
IN GENERAL. 
 
 33 
 
 green oxyde (hydra ted oxyde) of copper cannot be owing to 
 molecules of a different nature ; and the green of plants is un- 
 doubtedly produced by a homogeneous substance, in the same 
 way as the greater number of hues which exist in nature. This 
 colour owes then its origin sometimes to simple rays^ and some- 
 times to an union of different rays ; and some other colours are 
 in the same predicament. Were the green of plants due to two 
 substances, one of which is yellow and the other blue, it would 
 be extraordinary if we could not separate them, or at least 
 change their proportions by some solvent. There are, however, 
 some substances which contain colouring parts of different spe- 
 cies ; madder, for example, aa we shall see in the second part. 
 (Note A.) 
 
 The green, which we assume as an example of a truly com- 
 pound dyeing colour, shows that the colouring molecules cover 
 only one part of the surface of the stuff, although this may 
 appear of a full and uniform colour ; for, after the stuff has been 
 dyed blue, the yellow parts fix themselves on it, and produce 
 the green; and although the dyeing has been begun with 
 yellow, if a yellow of little permanence be employed, it may be 
 destroyed by air, and especially by chemical agents, while the 
 blue remains unaffected : which proves that it is on the stuff, 
 and not on the indigo, that the yellow particles have been prin- 
 cipally fixed. 
 
 Hence we see, that in order to procure the sensation of a 
 simple colour, the rays of the different colours require merely 
 to be approximated. In fact, we may produce a uniform colour 
 by the exact mixture of wools of different hues ; and in paint- 
 ing we obtain simple colours by the mixture of different ingre- 
 dients, which do not chemically combine. 
 
 The colouring particles form different combinations, and they 
 are applied either alone, or previously combined with other 
 substances, to wool, silk, linen, or cotton. The art of dyeing 
 consists in employing the affinities of the colouring particles so 
 as to extract, dissolve, and thereafter apply and fix them to the 
 substances to be dyed, which will be distinguished in this trea- 
 tise by the name of stuffs, whatsoever may be their nature and 
 their form. 
 
 It has been proposed to arrange colouring particles into ex- 
 tractive and resinous ; but this division conveys only incomplete 
 
34 
 
 BERTHOLLET ON DYEING 
 
 and false ideas of tlieir properties ; for there are colouring par- 
 ticles which, being insoluble in water, might be regarded as 
 resinous, and yet they do not dissolve in alcohol. Such are, the 
 red portion of carthamus, (safflower,) which dissolves merely by 
 means of an alkali ; and indigo, which, insoluble both in water 
 and alcohol, becomes soluble in alkalies only under certain cir- 
 cumstances ; but it dissolves readily in sulphuric acid. 
 
 The colouring particles which are soluble in water cannot be 
 compared to the mucilaginous and extractive parts of vegetables, 
 since the property of dissolving in water, like these substances, 
 gives no idea of the properties which it is essential to discover 
 in them; such as their relations to the chemical agents em- 
 ployed in dyeing, to air, to light, and to animal and vegetable 
 substances. 
 
 It is, moreover, an abuse injurious to the progress of sound 
 theorizing, to seek an explanation of the properties of colouring 
 substances in the mucilaginous, resinous, earthy, saline, and oily 
 parts which may be supposed to enter into their composition, as 
 Poerner particularly has done. 
 
 We have just seen, that in trying to account for the causes of 
 colours, and the nature of the colouring particles, two inconve- 
 niences have arisen : the one, from the attempt to explain the 
 action which the molecules of colouring substances exercise on 
 the rays of light by their density and thickness, without having 
 any means of determining these circumstances, and without 
 taking into view the afnnity arising from their chemical compo- 
 sition ; the other, to compare, from some slight relations, the 
 colouring particles with the mucilages and the resins, and to seek 
 to explain their properties by the parts supposed to enter into 
 their composition ; whereas their colouring properties ought to 
 be determined by direct experiments, and not be explained 
 by an imaginary composition. We depart from true theory, 
 which is solely the result of observation, when we ascribe to 
 laws purely mechanical the adherence of the colouring particles 
 to the substances which they dye, as well as the action of mor- 
 dants, and the difference between permanent and fugitive co- 
 lours. Hellot, to whom otherwise we are indebted for the best 
 practical treatise extant on dyeing wool, has fallen into a com- 
 plete illusion on this subject, and his theoretical ideas have 
 often influenced his observations, and the principles w^hich he 
 
IN GENERAL. 
 
 35 
 
 has laid down, as we may ascertain by the perusal of his work. 
 We may judge of his theory by the following passage : — I 
 believe it may be laid down as a general principle of the art 
 now treated of, that the whole invisible mechanism of dyeing 
 consists in dilating the pores of the bodies to be dyed, in de- 
 positing within them particles of a foreign matter, and in keep- 
 ing them there by a species of coat, {enduit,) which neither 
 water, rain, nor the rays of the sun, can affect ; in selecting 
 colouring molecules of such a tenuity that they may be retained 
 sufficiently incased in the pores of the subject, laid open by 
 the heat of boiling water, then contracted by cold, and farther 
 coated with a species of cement, {mastic,) which is left in the 
 very pores by the salts chosen to prepare them. Hence it 
 follows, that the pores of the fibres of wool, from which we 
 have fabricated or are going to fabricate stuffs, ought to be 
 cleansed, enlarged, coated over, then contracted, in order that 
 the colouring atom may be preserved in them nearly as a dia- 
 mond in the collet of a ring."* 
 
 We have reason to be surprised that Macquer should have 
 adopted the ideas of Hellot, Here would be the place," 
 says he, to explain the manner in which mordants act in 
 dyeing, and to develop the cause of fast and fugitive dyes ; but 
 these objects have been treated with so much sagacity by M. 
 Hellot, that I think it my duty to refer my reader to him."f 
 
 Dufay, however, had already perceived, that the colouring 
 particles were naturally disposed to contract a stronger or 
 weaker adhesion with the fibres which received them ; % and he 
 remarks very properly, that without this disposition the stuffs 
 would not take a colour similar to that of the dye-vat, or 
 divide equally with it the colouring particles; w^hereas the 
 liquor of the bath becomes sometimes as limpid as water, 
 giving up all its colouring matter to the stuff ; which seems," 
 says he, " to indicate that the ingredients have less attraction 
 for the water than for the particles of the wool." He adds, 
 that several other phenomena may be accounted for in the same 
 way ; but that such an explanation leaves still much to be de- 
 
 * L'Art de la teinture des laines, p. 42. 
 
 + L'Art de la teinture en soie, avant-propos, p. 8. 
 
 X Observations physique sur le melange de quelques couleurs dans la teinture. — Mem. de 
 Tacadem. 1737. 
 
 d2 
 
36 
 
 BERTHOLLET ON DYEING 
 
 sired, and that he would abandon it without difficulty were a 
 more probable one proposed. 
 
 Bergmann is the first who referred the phenomena of dyeing 
 entirely to chemical principles.* Having dyed wool and silk in 
 a solution of indigo, in sulphuric acid much diluted with water, 
 he explains the effects which he observed in this operation, by 
 ascribing them to the precipitation occasioned by the greater 
 affinity of the wool and the silk for the blue molecules, than 
 of these molecules and the acidulous water. He remarks, that 
 this affinity of the wool is powerful enough to deprive the 
 liquid entirely of its colouring particles ; but that the feebler 
 affinity of the silk can only diminish the proportion of these 
 particles in the bath ; and he shows, that on these different 
 affinities depend both the permanence and intensity of the 
 colour. 
 
 This is, in fact, the legitimate manner of viewing the phe- 
 nomena of dyeing, which are true chemical phenomena. 
 
 A short while thereafter Macquer adopted this theory, and 
 made just applications of it to the action of mordants, and parti- 
 cularly of alumina. f 
 
 Whatever may be the physical cause of colours, the colouring 
 particles, which it is the object of the art of dyeing to apply to 
 stuffs, possess chemical properties distinguishing them from 
 other substances dependent on the affinities which their particles 
 collectively exercise, as well as on the reciprocal action of these 
 particles, and on their constitution, which disposes them more 
 or less to assume the solid or the liquid state. 
 
 By virtue of these properties, they dissolve in different liquids, 
 they combine with acids, alkalies, oxydes^ with some earths, and 
 especially alumina ; they frequently precipitate the oxydes and 
 alumina from the acids which held them in solution ; in other 
 circumstances they even form super-compounds with the salts ; 
 sometimes they unite immediately to the stuffs ; more frequent- 
 ly they form with these substances a combination much more 
 intimate through diU intermedium , or even they do not combine 
 with it except through the intermedium; the intermedium modi- 
 
 * Analyse de Tindigo. Mem. des Savans etrang. torn. ix. ; Mem. envoy^ pour le 
 prix propose en 1776, et dans les notes sur le traits dc Scheffer. 
 f Diction, de cliim. 2nd edition, au mot teinture, 1778. 
 
IN GENERAL, 
 
 37 
 
 fying more or less their colour, their other properties, and even 
 their composition. 
 
 The difference in the affinity of the colouring particles for 
 wool, silk, and cotton, is sometimes so great, that they refuse to 
 combine with one of these substances, whilst they combine very 
 well with another ; thus, cotton takes no colour in the bath that 
 dyes wool scarlet. Dufay got a piece of stuff made, the warp 
 of which was wool, and the weft cotton; he passed this stuff 
 through the fulling-mill, to ensure the same preparation to the 
 wool and cotton ; but the wool took the scarlet dye, and the 
 cotton remained white. It is this difference of affinity which 
 makes it necessary to vary the preparations and the processes, 
 according to the nature of the substance which we wish to dye 
 of a particular colour. 
 
 If the effects of the intermedia employed in dyeing, and if 
 the fixation of the colouring particles on a stuff by itself, or by 
 means of an intermedium, be owing to the combinations which 
 are formed, we must still refer to chemical combination the 
 changes produced, by acids and alkalies, in several vegetable 
 colours, which chemists employ for verifying the nature of 
 different substances. We may compare the resulting compounds 
 to neutral salts, w^hich possess qualities distinct from those of 
 their components, but in which one of the components may be 
 in excess, so as to cause its properties to predominate. This 
 state of combination is observed between the colouring particles 
 of cochineal and the acidulous tartrate of potash, or cream of 
 tartar. On evaporating slowly a solution of this salt in a decoc- 
 tion of cochineal, crystals' are formed, which retain a fine ruby 
 colour, much more intense and more lively than that of the 
 liquid in which they were formed. 
 
 The reciprocal action of acids and alkalies being much greater 
 than that which they exercise in particular on the colouring 
 particles, they can mutually saturate each other, and then the 
 resulting compound has little effect on the colouring particles, so 
 that the changes which had been produced by one of the substances 
 disappear when it is neutralized by an antagonist substance. 
 
 Blue colours are not the only ones which can pass to red by 
 the agency of acids, and to green by that of alkalies ; the most 
 part of the red colours, that of the rose, for example, are exalted by 
 acids, and pass to green by alkalies; and some green colours, 
 
38 
 
 BERTHOLLET ON DYEING 
 
 such as that of the decoction of burdock, according to the testi- 
 mony of Nose,* and the green juice of the buckthorne berries, 
 {rhamus catharticus) according to Becker, redden also with acids. 
 
 This property, common to the most ordinary colours of vege- 
 tables, appears to prove that there is a close analogy betv^een 
 the greater part of their colouring matters ; nor is it without 
 foundation that Linnseusf thought the red colour owing to an 
 acid, of which he maintained the existence ; but there are also 
 several vegetables which contain a free acid, without possessing a 
 red colour. J 
 
 In the combination which the colouring molecules form with 
 the stuff, they preserve only a part of their original properties ; 
 on being associated with alumina, with the oxydes, and some 
 other substances, they are somewhat modified ; but the proper- 
 ties of the latter combinations are further modified when they 
 unite with the stuff. 
 
 These modifications are analogous to what is observed in 
 other chemical combinations ; but they are subject to a peculiar 
 degradation from the action of air and light ; sometimes, on the 
 contrary, they receive from these agents a new lustre, or a different 
 shade : there are also agents which, after combining with the 
 colouring particles, alter the colour which they first produced, 
 making it pass to yellow, and then destroy it ; such in particular 
 is oxygenated muriatic acid (chlorine ;) it acts by means of the 
 oxygen which it yields, and consequently differs *in nothing 
 except intensity from that of the atmospheric air.§ 
 
 It follows, from what has been stated, 1. That the colouring 
 molecules have affinities which produce their solution and their 
 
 * Versuch eineger Beytrage zur Chemie. 
 t Amsenitatum acad. torn. iv. 
 
 \ There are flowers whose colour appears to be naturally modified by a very feeble acid , 
 without being decidedly red : such is the flower of violet, whose violet juice becomes 
 blue when we leave it for some time in a tin vessel, probably because the acid which it 
 contained combines with a portion of oxyde on the surface of the tin ; such also is the 
 flower of the mallow, which becomes blue by simple drying. The primitive colour is 
 restored by the addition of a very small quantity of acid." — Observ. physico-chim^ sur les 
 coukurs^par Opoix, Journal de physique^ torn, viii, 
 
 § This theory is no longer tenable, since it is known that dry chlorine, even though con- 
 densed into the liquid state, does not blanch dry litmus paper. When moisture intervenes 
 muriatic acid is formed, and oxygen evolved ; to the action of which body on the colour the 
 bleaching effect is to be ascribed. Water is the source of the discoloration both in the 
 ancient and the modern process of bleaching. --T. 
 
IN GENERAL. 
 
 39 
 
 combination^ the effects of which, combining with those of their 
 own constitution, form the differences that distinguish them from 
 each other. 
 
 2. That they unite directly with the stuff, or by the aid of an 
 intermedium ; but the stuff has relations with them according to 
 its nature. 
 
 3. That, in combining with a substance, they experience a 
 change which modifies their colour, besides the modification 
 resulting from the shade peculiar to the substance to which they 
 combine. 
 
 4. That the colouring molecules differ not only from one 
 another by these different dispositions, but likewise by the 
 ulterior changes which they may suffer from the action of other 
 substances, and particularly from that of the air and light. 
 
 In order to establish, on these grounds, the principles of the 
 art of dyeing, so as to explain the peculiar phenomena which it 
 presents, to guide ourselves in its practice, and to obtain the 
 surest, easiest, and most economical processes, either for exe- 
 cuting known operations, or for fulfilling the demands of the 
 consumers, and improving the art, we shall in this section 
 examine more particularly the effects arising from the action of 
 substances which serve as intermedia^ and those produced by the 
 agents which may affect the nature of the colours. 
 
 But stuffs possess different relations with the colouring par- 
 ticles, and they must receive preparations preliminary to the 
 operations of dyeing : under this point of view, we shall exam- 
 ine them in the second section. 
 
 The third section will be devoted to the art of bleaching 
 linen and cotton by the oxygenated muriatic acid, (chlorine.) 
 
 We shall be occupied, in the fourth, with the manipulations 
 of dyeing in general, and the means by which we can ascertain 
 the goodness of colours. 
 
 We shall present, in the fifth, a summary account of the 
 principal ingredients employed in dyeing, in reference to dis- 
 solving, modifying, and fixing the colouring particles. 
 
 After having thus exhibited, in the first part of this work, the 
 general facts which are to be applied to particular operations, 
 we shall detail, in the second part, the processes of dyeing, ar- 
 ranging them into genera and species of colour. Here we shall 
 examine every colouring substance; we shall apply to the different 
 
40 
 
 BERTHOLLET ON DYEING 
 
 dyes the principles established in the first part ; we shall unfold 
 the processes of the art, and independently of the explanations, 
 we shall endeavour to improve it by direct experiments. We 
 shall then try to harmonize the results of experiment with the 
 principles of chemistry ; but we shall stop whenever these prin- 
 ciples cannot conduct us to satisfactory explanations, or we shall 
 confine ourselves to conjectures, to be verified by the future ad- 
 vancement of the science. 
 
 CHAPTER 11. 
 Of Mordants, 
 
 The term mordant is given to those substances which serve as 
 intermedia between the colouring parts and the stuffs which 
 they dye, either for facilitating or modifying their combination. 
 This word is rendered appropriate by the use which even the 
 ancients made of it.* We may distinguish, under the title of 
 alteratives, the ingredients which are employed merely with the 
 view of changing the shade. 
 
 Mordants merit the greatest attention. It is by them chiefly 
 that we diversify the colours, give them more brilliancy, fix them 
 on the stuffs, and render them more durable. 
 
 A mordant is not always a simple agent, but in the mixture 
 composing it different combinations are sometimes formed, so 
 that the substances which have been employed do not act imme- 
 diately, but by the resulting combinations. 
 
 Sometimes the mordant is mingled with the colouring par- 
 ticles ; sometimes the stuff* is impregnated with it before being 
 exposed to the dyeing bath. On other occasions these two 
 methods are combined. We may dye in succession with 
 liquors which contain different substances, the last of which 
 acts only on the parts with which the stuff* has been imbued by 
 the preceding operation. One solution, which is to yield its 
 basis to the stuff* has need of heat ; another requires the ope- 
 ration to be made in the cold. The mordant is frequently an 
 oxyde ; in which case its properties may vary, not only accord- 
 
 * Ameilhon. mem. de rinstitut. litter, torn. hi. 
 
IN GENERAL. 
 
 41 
 
 ing to its actual condition, but also according to the action of 
 the substances with which it is associated, and even according to 
 the circumstances of the operation. It is by the determination 
 of all these conditions that chemistry can particularly direct the 
 art of dyeing, can establish its processes in a constant manner, 
 removing from it whatever is useless or prejudicial, and trans- 
 ferring to one kind of dyeing what is found efficacious in another. 
 
 We shall describe, in the fifth section, the essential proper- 
 ties of the chemical agents of which the greatest use is made in 
 the quality of mordants : we shall determine, in the second 
 part, the particular eff'ects which they produce on every species 
 of colouring substance, detailing every fact which experience 
 has taught concerning those operations of dyeing in which they 
 are employed. At present we shall confine ourselves to the 
 development of the general observations which have been made 
 on their action. 
 
 There are colouring substances on which acids and alkalies 
 appear to have but a feeble action, which are soluble in water, 
 and combine immediately with stuffs ; such are several dun 
 colours, extracted from woods and roots, and the husks of the 
 walnut. These substances serve, therefore, the purpose of 
 dyeing without the aid of any mordants. There are some, 
 again, which dissolve only by alkalies, as, in particular, the 
 safflower. — Its colouring part quits the alkalies, and fixes on the 
 stuffs, when those are saturated with an acid. The anotto, which 
 dissolves easily by means of an alkali, abandons it to combine 
 with the stuff*, without the necessity of employing an acid. When 
 indigo is deprived of oxygen, it becomes yellow, and is then soluble 
 in alkalies. Stuffs may abstract it also from the alkalies, and then 
 it resumes its blue colour, through the agency of oxygen. Dyes 
 made with these colouring substances have no need of auxiliaries. 
 But the greater number combine only in small quantity with 
 the stuffs, when a base does not serve as an intermedium to their 
 union. They adhere feebly to it, and resist much less the 
 causes of destruction. 
 
 The substances employed as mordants should therefore furnish 
 a base which attaches itself to the stuffs and to the colouring 
 particles, and which resists their redissolution and destruction. 
 As to those substances, however, which occasion merely some 
 modifications in the colours, it is sufficient for them to be re- 
 
42 
 
 BERTHOLLET ON DYEING 
 
 tained in small quantity in the combination formed between the 
 stuffs, the mordant, and the colouring matter. Hence, although 
 alteratives act equally by combining, they should be distinguished, 
 however, from mordants, which serve to fix the combination. 
 
 Acids can in general dissolve the colouring substances, but 
 as they do not themselves possess the property of combining with 
 the stuff, they cannot serve as bonds of union ; on the contrary, 
 they usually carry off the colouring particles which had been 
 retained by the stuff, and they contribute to the colour which is 
 fixed, only in the quality of alteratives, by uniting in small 
 quantity to the coloured combination. 
 
 The alkalies, among which we must comprise the earths that 
 produce saturation with acids, can combine with the most part 
 of colouring substances ; but, in order to ascertain the effects 
 which they ought to produce according to their differences, and. 
 to compare them with those due to the acids, we must direct 
 our attention to the properties of the combinations which depend 
 on those of their elements. 
 
 While reciprocal affinity produces an union, the dispositions 
 of the substances to solidity or liquidity are preserved in the 
 combinations, with the differences proceeding from the conden- 
 sation which they experience.* 
 
 It thence results that the alkalies, which possess much solu- 
 bility, ought to form soluble combinations with the colouring 
 substances which have an affinity for them; but those which 
 have little solubility ought, on the contrary, to produce insol- 
 uble combinations. 
 
 These considerations, which are supported by the results of 
 the reciprocal action of acids and alkalies, and by the properties 
 of the combinations in general, lead us to distinguish the effects 
 of the different bases. Potash, soda, and ammonia, cannot 
 serve as intermedia to fix the colouring substances on stuffs; but 
 they may, as well as acids, effect the solution of colouring sub- 
 stances on which they have an action. Their affinity with the 
 stuffs should also tend to operate their solution. It is only as 
 alteratives that these alkalies can enter into coloured combina- 
 tions. If they produce some precipitation in the watery solu- 
 tions of colouring substances, it must be merely by separating a 
 body much more soluble, from another in itself slightly soluble, 
 
 * Essai (le statique chimique. 
 
IN GENERAL. 
 
 43 
 
 or by occasioning some change in a substance of somewhat un- 
 stable composition. 
 
 The other alkalies, namely, lime, barytes, strontian, and mag- 
 nesia, which possess little solubility, or a much greater tendency 
 to solidity, appear fitter to serve as mordants. In fact, these 
 alkaline earths have sufficient affinity to form, with colouring 
 substances, combinations which are precipitated from their 
 solution ; but they considerably affect their colours by their 
 alkaline properties. They possess too weak an affinity to enter 
 into an insoluble combination with the stuffs ; so that, far from 
 promoting the union of the colouring particles, on the contrary 
 they obstruct it, forming insulated precipitations. 
 
 Magnesia, which is insoluble, afforded the prospect of being 
 usefully employed as a mordant. In order to try it, acetate of 
 magnesia was mixed with an infusion of brazil wood. A pre- 
 cipitate took place of a dull violet colour. After ascertaining 
 the faculty it possesses of falling down with colouring sub- 
 stances, cotton was impregnated with the above salt, as is done 
 with the acetate of alumina; but this cotton took no more 
 colour than if it had received no mordant. Wool treated with 
 acetate of magnesia, did not derive from it the property of 
 fixing the colour of madder ; no more did silk. It appears, 
 then, that the alkalies in general can serve only as solvents or 
 alteratives ; but in this latter quality, those which have the 
 least solubility should be the most efficacious. The same thing 
 is true of the acids ; whence the utility of the bitartrate of potash 
 in several processes. 
 
 The body which possesses in an eminent degree the properties 
 suitable for a mordant is alumina. Insoluble when it does not 
 experience the action of acids or alkalies, it has a strong dispo- 
 sition to combine with the colouring particles ; it does not act on 
 their colours as the alkalies do, but it preserves very nearly 
 their natural hue. It separates also much more easily from the 
 acids which hold it in solution, than the alkaline bases do. 
 
 To be convinced of the property which alumina possesses, of 
 combining with the colouring particles, we have only to agitate 
 alumina, precipitated from the sulphate of alumina by an alkali, 
 with an infusion of brazil wood, when all the colouring particles 
 separate from the water, and remain fixed in the earth. It is 
 
44 
 
 BERTHOLLET ON DYEING 
 
 this combination which forms some lakes, and particularly the 
 stils de grains.'^ 
 
 This is not the method, however, in which it is directly em- 
 ployed for the composition of the most part of lakes. 
 
 A decoction of the colouring substance from which we wish 
 to obtain a lake, is mixed with a solution of the sulphate of 
 alumina. There is usually formed a precipitate, which carries 
 down a portion of the colouring substance. With some colour- 
 ing matters, however, no precipitate ensues. To cause, or to 
 complete it, the acid of the salt is saturated witb an alkali, when 
 the alumina falls down, retaining in combination with it the 
 colouring substance ; it is this precipitate, whose colour varies 
 with the substance employed, which forms the lakes, after 
 sufficient washing to carry off the saline particles. For the 
 stils de grains, the decoction, mingled with the sulphate of alu- 
 mina, is passed through a calcareous carbonate, which serves, at 
 least in part, to decompose the sulphate of alumina ; or through 
 a clay, whose action on the sulphuric acid contributes also to 
 the decomposition of the alum, and to the precipitation of the 
 lake. What occurs here by the action of the alkali or the clay, 
 which tend to seize the acid, is effected in dyeing by an opposite 
 action, by the affinity between the stuff and the coloured alumina. 
 
 The affinity of alumina for the different stuffs may be easily 
 proved. If an animal substance be dissolved by an alkali, and 
 if with this solution alum be mixed, the animal substance pre- 
 cipitates in combination with the alumina. The same combina- 
 tion is formed when, after mixing gelatin with a solution of 
 sulphate of alumina, an alkali is poured into it. 
 
 The combination of alumina and the animal substance may be 
 combined with a colouring substance. For example, when, in 
 the preceding experiment, the decoction of a colouring substance, 
 such as brazil wood, is mixed with the solution of sulphate of 
 alumina and gelatin, the coloured precipitate thus obtained 
 represents the combination which is formed with the stuffs in 
 those dyes where a mordant is employed. 
 
 Although it cannot be proved in the same manner, that alumina 
 enters into combination with linen and cotton, yet the effects 
 
 * Traits th^orique et pratique sur Tart de faire et d'appliquer les vcrnis, &c., par 
 Tingry, torn, ii. 
 
IN GENERAL. 
 
 45 
 
 which aluminous mordants produce upon these substances, leave 
 no doubt that a combination with alumina is formed. Hence, 
 by means of alumina, colouring substances which could not be 
 fixed, or would be speedily destroyed, quit their solvent, form 
 with the alumina more saturated and durable colours, and even 
 when the colour has disappeared, the stuff still retains the alu- 
 mina, which can fix new colouring substances, and impart to it 
 the requisite properties. Bancroft relates, that having impreg- 
 nated with acetate of alumina one part of a cotton web, while 
 the rest of it had no mordant, and having dyed this cloth with 
 saffron, he exposed it on the grass : The colour soon disappeared 
 on the part which had received no mordant, and some time after- 
 wards on the portion which had been imbued with the mordant. 
 He then dyed the cloth anew with saffron, when the exposure on 
 the grass produced the same effect. Finally, after a third dye- 
 ing, the mordant still gave the same faculty to the portion of the 
 cloth to which it had been applied. Hence alumina remained 
 fixed, notwithstanding the three dyeing operations. 
 
 It is manifest, therefore, when a stuff* acquires, by means of 
 an aluminous salt, the properties dependent on alumina, that it 
 can decompose ^this salt and combine with its alumina, whilst 
 the acid which held it in solution is disengaged and remains in 
 the bath ; but we must not thence conclude, that no portion of* 
 the acid remains in combination with the stuff*, so as to have 
 some influence on the colour. (Note B.) 
 
 Metallic oxides possess with several colouring particles such 
 an aflSinity, that they abandon the acids which kept them in solu- 
 tion to precipitate in combination with the colour. 
 
 On the other hand, all the oxydes possess the property of 
 combining with animal substances ; which several combinations 
 may be formed, by mixing with the metallic solutions an alkali 
 saturated with the animal substance.* 
 
 It is not therefore surprising, that the metallic oxydes can 
 serve as bonds of union between the colouring particles and 
 animal substances ; but they differ greatly in this respect. Let 
 us examine on what peculiarities these differences depend. 
 
 Although all the oxydes have a disposition to combine with 
 the animal substances, they differ much in this particular ; so 
 
 * Mem. de racademie, 1784. 
 
46 
 
 BERTHOLLET ON DYEING 
 
 that, especially when the animal substances form a solid tex- 
 ture, there are oxydes to which they can hardly unite. Supposing 
 the same degree of affinity, those oxydes which form a stronger 
 combination with the acids ought to abandon them with more 
 difficulty ; and again, the same oxyde ought to be more easily 
 precipitated from feeble acids than from such as act with more 
 energy. Hence it is not astonishing that there are only some 
 metallic solutions which can be employed as mordants, and that 
 in conformity with the purpose intended. 
 
 Some metallic substances carry into their combinations only a 
 white and colourless base ; others modify, by the association of 
 their own colour, and of the colouring matter ; but in several 
 oxydes the colour varies according to the proportion of oxygen 
 fixed in them, or according to other undetermined circumstances. 
 The latter oxydes could not serve as a base to durable colours, 
 whose lustre would be easily affected by these ready alteratives, 
 unless it were russet hues, whose slight changes would be 
 imperceptible. 
 
 The oxyde of tin surpasses all the others in its property of 
 becoming fixed on woollen and silken stuffs, but especially on the 
 former. It readily abandons the acid which holds it in solution 
 to combine with them, so that it is sufficient to impregnate wool 
 and silk with solution of tin, although they should be then 
 thoroughly washed ; a process which does not answer with other 
 metallic solutions. 
 
 Tin slightly oxydized, has, in reality, only an ashy colour. 
 But since it has a great affinity for oxygen, it takes enough of it 
 in the ordinary solutions to pass to the white colour ; or it may 
 complete its oxydizement even during the operations of dyeing. 
 It retains its oxygen with force, and hence, when highly oxyd- 
 ized, its oxygen exerts but little action on a colouring matter. 
 The oxyde of zinc appears to possess analogous properties, but 
 it has much less affinity with stuffs and with colouring particles; 
 while, on the other hand, it retains the acids more powerfully, 
 and is thereby much less fit for a mordant. (Note C.) 
 
 The affinity of the oxydes for substances of a vegetable nature 
 appears to be much weaker than for animal substances ; whence 
 it happens, that metallic solutions are not well adapted to serve 
 as mordants for colours in cotton and linen. An exception 
 must, however, be made in favour of the oxyde of iron, which 
 
IN GENERAL. 
 
 47 
 
 may be applied in a very solid manner to these substances, even 
 when it is precipitated from its solutions. To this purpose 
 Chaptal makes an interesting observation.* He states, that a 
 solution of iron disturbed by precipitation may be cleared up by 
 moving cotton and linen through it. We must, however, observe, 
 that the oxyde of iron differs in colour according to its state of 
 oxydation ; and that the action which it exercises on the colour- 
 ing substance, varies, as we shall see, according to that state. 
 The oxyde of copper has also some affinity for linen and cotton, 
 so that its solutions maybe employed in some processes. Oxyde 
 of manganese announces a similar disposition. 
 
 It follows from what we have now stated, 1. That the acids 
 and the alkalies are not fit for mordants, that is to say, for inter- 
 media or bonds of union between the stuffs and the colouring 
 substances, although those of sparing solubility can produce 
 species of lakes with colouring matters : 2, That of all the 
 earthy substances, alumina is the one eminently endowed with 
 the properties of a mordant, from its affinity with colouring 
 substances and with stuffs, and from its feeble attraction to acids : 
 3. That among metallic substances we must distinguish those 
 which afford a white base to the colouring substances, and those 
 which affect the colouring matters by their own colours. Among 
 the former, which are fit for light and splendid colours, the 
 solutions of tin hold the first rank, from the affinity of the 
 oxyde for the stuffs of an animal nature, and for the colouring 
 substances, as also from its weak attachment to acids. The 
 force with which it retains oxygen contributes to its qualities. 
 Among metallic substances, whose colour produces modifications, 
 iron is of the most extensive employment ; but its effects vary 
 according to its state of oxydation. 
 
 When the colouring particles have precipitated an oxyde from 
 its solvent, the latter has usually the power of dissolving a por- 
 tion of the combination of the colouring substance with the 
 oxyde, and the liquid remains coloured, although the precipitation 
 be facilitated, and rendered more complete, by the presence of 
 the stuff. The effects depend therefore in part, not only on 
 the proportion, but also on the species, of acid which acts as a 
 solvent to the oxyde. This observation is applicable to acids 
 
 * Mem. de Tinstit. torn. iii. 
 
48 
 
 BERTHOLLET ON DYEING 
 
 which hold alumina in solution ; but the acids, alkalies, metallic 
 solutions, and even the neutral salts, may serve as alterants. 
 
 We observe, that by varying the mordants we may greatly 
 multiply the shades obtainable from any one substance, especially 
 with the co-operation of the alterants. It is sufficient merely to 
 vary the method of applying them. Thus we shall obtain diffe- 
 rent effects, by impregnating a stuff with the mordant, or by 
 mixing the mordant in the dyeing bath ; by making the opera- 
 tion with heat or cold, with the continued contact of air, or 
 without its intervention ; by means of a solution in a strong 
 acid, or of one in a feebler or more volatile acid. 
 
 Drying favours the combination of the bases which have an 
 affinity for the stuff, because the water which produced the solu- 
 tion resists, by its own affinity, the action of the stuff that tends 
 to bring it to the solid state. 
 
 But the circumstances by which we ought to be regulated 
 vary according to the qualities of the stuff, which, by a disposi- 
 tion whose cause cannot always be assigned, requires sometimes 
 the aid of heat, whilst a stuff of a different nature combines 
 better in the cold. 
 
 Finally, the processes which a stuff should receive in succes- 
 sion, to attain the proposed end, sometimes decide the choice of 
 the solution of the mordant, and the manner of applying it. 
 This is particularly observable in reference to cloths for printing, 
 which should be able to pass through several operations without 
 suffering injury from any one of them. 
 
 This beautiful art, (calico printing,) which was introduced into 
 Europe only in the middle of the last century, has made the 
 most rapid progress, having arrived at a perfection not only very 
 superior to the condition in which it has remained for so many 
 centuries in Hindostan, but it has become one whose processes 
 possess the greatest precision, and are susceptible of the most 
 complete explanation. 
 
 The perfection to which it has been carried among us, princi- 
 pally by the active and enlightened industry of the celebrated 
 Oberkampf, recently seconded by that of Widmer, is owing in 
 part to the necessity of insulating the processes, in order to 
 succeed, not only in varying the -colours and the shades, but 
 likewise in securing to them a permanence which may resist the 
 operations requisite to give due whiteness to the intervals which 
 
IN GENERAL. 
 
 49 
 
 separate the printed spots. Hence it has been possible to observe 
 and ascertain the effects of every operation ; and hence every 
 colour has been subjected to the severest trials ; v^hereas the 
 other processes of dyeing often confound together different 
 effects, involving them in a fleeting lustre. 
 
 Since the processes of this art are v^ell fitted to give an exact 
 idea of the effects of mordants, and of the different circum- 
 stances v^hich modify them, v^e shall here trace an outline 
 of it. 
 
 The mordants possessed of great solubility, whose acid, 
 capable of being volatilized, is united to its base by a feeble 
 affinity, are preferred for calico printing, because, as they can 
 be put upon the cloth in a greater state of concentration, and 
 can be more completely decomposed upon it, more intense and 
 substantial colours may be obtained. Their solubility gives them 
 the further advantage of not rendering the mordant clotty, when 
 it is thickened, or unequable during its desiccation on the cloth, 
 by the effect of crystallization. 
 
 The acetate of alumina and the acetate of iron possess these 
 properties, and are sufficient to produce, with different colouring 
 substances, the greater number of the diversified hues observa- 
 ble in printed goods. 
 
 To prepare the acetate of alumina, three parts by weight of 
 alum, and one of acetate of lead, are dissolved in eight parts of 
 hot water. An eighth part of potash, and as much chalk, are 
 afterwards added. The oxyde of lead contained in the acetate, 
 forms, with the sulphuric acid of the alum, an insoluble salt, 
 which precipitates ; while the base of the alum, or the alumina, 
 remains in solution, combined with the acetic acid. Since in 
 this, the generally adopted process, the proportion of acetate of 
 lead, is not sufficiently great to effect the entire decomposition of 
 the alum, the chalk and potash are added, which serve to decom- 
 pose a portion of this salt, whose crystallization in the inspissated 
 mordant might have rendered its employment prejudicial. We 
 may produce, without the addition of the chalk or potash, an 
 acetate of alumina, which has not this inconvenience, by put- 
 ting along with the given proportions of alum and water three 
 and a half parts of acetate of lead. (Note D.) 
 
 The acetate of iron is made by the direct solution of pieces of 
 rusty iron in acetfe acid, the vinegar of commerce. (The crude 
 
 E 
 
50 
 
 BERTHOLLET ON DYEING 
 
 vinegar, called pyrolignous acid, is now usually employed for 
 this purpose in Great Britain. — T.) 
 
 The mordants are thickened with different kinds of gum, 
 starch, or flour. They should be sufficiently so to preserve, in 
 the impressions of the cloth, the outlines of the objects engraven 
 on the plate, but not so much as to hinder their leaving the 
 plate equably in their application to the cloth. This receives 
 as many different impressions as (here are different mordants ; 
 but no more are applied at a time than are to be coloured in the 
 same dyeing bath. 
 
 When the cloth is in this condition, it is left for several days, 
 stretched in the workshop, exposed to a moderate heat in a cham- 
 ber, called in the calico manufactories the hot room (or stove). 
 This heat^ bv favouring the volatilization of the acetic acid, 
 accelerates and completes the decomposition of the mordants, as 
 well as the combination of their bases with the cloth. On 
 coming out of this chamber it is passed into a boiler which con- 
 tains cow-dung diff*used through hot water. The effect of this 
 operation is to dissolve the substance made use of for thickening 
 the mordant, as also the portion of this mordant which, not 
 having combined with the stuff*, and being diffused in the dye- 
 bath, would soil it, both by the combination which it would 
 form with the colouring matter^ and by the action of the acid 
 which it might deposit upon it. Thus a twofold injury would 
 accrue to the cloth, by the impoverishment of the dye-bath, and 
 by the covering of the portions which should remain white, with 
 the combination, difficultly detachable, of the superfluous mor- 
 dant wnth the colouring matter. V/idmer conceives, that there 
 is formed, besides, in the dunging, a triple combination of the 
 animal matter with the alumina and the cloth, which improves the 
 beauty of the colours. This opinion is the more probable, since 
 water alone does not produce the effect of the dunging ; in 
 which process an examination, not however very elaborate, has 
 not enabled us to perceive any other substance capable of acting, 
 except a matter analogous to bile. (Note E.) 
 
 Before being dyed, the cloths ought still to be carefully 
 washed and beetled, to secure the removal of all the combined 
 mordant. Water and mechanical beating are here employed. 
 (The wash-wheels of our print-fields answer this purpose admi- 
 rably. — T.) They are then introduced into the dye-bath, where 
 
IN GENERAL. 
 
 51 
 
 the whole surface becomes coloured ; but the colours are much 
 deeper on the parts impressed with the mordant. The colouring 
 matter thus enters into a triple combination with the mordant 
 and the stuff, thereby acquiring the faculty of resisting external 
 agents much more than when it is insulated or combined with 
 the stuff without any mordant. (Note F.) 
 
 On this peculiarity are founded the processes employed for 
 restoring, to the parts of the cloth which have received no mor- 
 dant, the white colour which they possessed before this dyeing. 
 To produce it, the goods are boiled in water along with bran, 
 they are then exposed on the field, observing to lay on the grass 
 the surface of the cloth that bears the colours. By the alter- 
 nate repetition of these operations, the colouring matters un- 
 combined with the mordants are changed in their composition, 
 dissolved and detached ; whereas those which are actually com- 
 bined, far from suffering change, acquire more lustre, and thus 
 the figures alone remain coloured. (Note G.) 
 
 This destruction of the colouring particles by exposure in the 
 field, and ebullition wdth bran, is effected in the same manner as 
 that of the colouring particles of flax, and is explained in the 
 same way. The difference of the process consists solely in the 
 substitution of bran for alkalies ; because these would dissolve 
 a portion of the colouring substance fixed by the mordant, and 
 would alter its colour ; whereas the bran having a much weaker 
 action on this substance, affects merely the colouring particles, 
 rendered soluble by the action of the air. The identity of the 
 effects of this process with those of common bleaching, has led 
 Widmer to substitute for this method the employment of chlo- 
 rine, modified by an alkaline solution. Haussman has used 
 this plan with success ; and it is known to be practised in many 
 English manufactories,* (Note H.) 
 
 From madder, with acetate of alumina more or less diluted 
 with water, are obtained the deep reds, and their different shades, 
 down to a delicate rose colour ; with acetate of iron, from black 
 to lilac, passing through all the intermediate violet hues ; and 
 finally, with the mixture of these two mordants, in different 
 proportions, the amaranths, the mordores, (brownreds,) the 
 browns, and the puce-coloured. By substituting woad for mad- 
 
 * See Section III. 
 E 2 
 
52 BERTIIOLLET ON DYEING 
 
 der, we procure, with the first of the above mordants, the 
 yellows ; with the second, only dull olives ; but with their dif- 
 ferent mixtures, we have agreeable olive and bronze colours. 
 Combining the action of these two tinctorial substances in their 
 turn on each of these mordants, very diversified mingled hues 
 are obtained. When we treat of the particular processes of 
 dyeing, we shall enter into more details concerning those which 
 relate to the dyeing of printed goods. 
 
 The following are, in general, the steps of the operations of this 
 art. To apply to cloth the most soluble and most easily decom- 
 posed mordants ; to promote their drying and decomposition ; to 
 remove, by animalizing the cloth, whatever has not entered into 
 combination with it ; to dye, and to restore to the portions not 
 printed the purest white. To these operations the whole process 
 is reducible. It evidently proves, that linen and cotton are 
 susceptible of combination with the bases of the mordants ; 
 that this combination possesses a great aflinity for colouring 
 matters ; and that it communicates to them the property of being 
 much more unalterable by the ordinary agents of their destruction. 
 
 Some colours, however, may be directly printed upon cloth, 
 with all the solidity and lustre of which they are susceptible : 
 such, for example, is that of indigo, known under the name of 
 pencil blue^ because it is usually applied with this instrument ; 
 that called rust-yellow, because it is obtained by printing 
 on slightly oxydized oxyde of iron, resulting from the de- 
 composition of two parts of sulphate of iron with one of acetate 
 /f lead, diff'used in eight parts of water. These are styled 
 colours of application. They possess the great advantage of 
 requiring no operations except those of printing and washing. 
 The colours now mentioned, which have been long used, are 
 very durable, and so much the simpler, as they have no need of 
 a mordant ; but the number of those possessed of this property 
 are very limited. In others, we must attach to the stuff* at the 
 same time, a mordant and a colouring matter, capable of com- 
 bining together, and of thus uniting with the cloth. This method, 
 analogous to that used for wool and silk, of dyeing in a bath 
 composed of the mordant and the colouring substance, has 
 been hitherto successfully applied in only a very few cases, in 
 consequence of the weak aflinity which cotton and linen have 
 for colouring substances united to mordants. 
 
IN GENERAL. 
 
 53 
 
 There is another method, still little known, of producing upon 
 cloth, at little expense, a diversity of colours. It consists in 
 applying to the cloth, previously impregnated v^ith the mordants 
 and the dyes, substances w^hich, serving themselves as mordants, 
 modify the shade which the colouring matter has given, with 
 that already existing on the cloth : or to apply some others, 
 which, carrying with them an acid capable of dissolving this 
 mordant, and already combined with a colouring matter, thus 
 substitute a new mordant for that which is on the rest of the 
 cloth, and add also a colouring matter to that which was there 
 before. By a similar process, a white may be induced on dyed 
 goods. Oberkampf formerly employed, and then abandoned 
 this process. Widmer has since improved it much, and applied 
 it to colours w^hich presented the greatest difficulties. The 
 English manufacturers make great use of it ; they employ for 
 this purpose a bisulphate of potash, and lemon juice. This 
 composition may answer for cloth which has received little mor- 
 dant, but it is doubtful if it can serve for others.* (Note L) 
 
 CHAPTER III. 
 
 Of Astringents in general, and particularly of the Gallic Acid 
 
 and Tannin. 
 
 Astringents deserve peculiar attention, not only because 
 they are of great use in dyeing, but because by this title is dis- 
 tinguished a property common to a great many vegetables. 
 
 Perhaps there is no property in vegetables concerning which 
 such vague ideas have been currently received. A slight rela- 
 tion in taste has frequently been deemed enough to rank them 
 in the class of astringents ; and every substance has been com- 
 monly regarded as astringent or acerb, which turned a solution 
 of iron black. This effect has been presumed to arise from one 
 identical principle residing in all the bodies that produce it. Ex- 
 perience has subsequently shown, that two species of astringents 
 ought to be admitted, viz. tannin and gallic acid. Before describing 
 
 * The principle of Mr. Thompson's patent is excellent for this purpose. Dyed cloth 
 topically impressed with a thickened solution of any vegetable acid, tartaric for example, is 
 passed through a solution of chloiide of liiiie. — T. 
 
64 
 
 BERTHOLLET ON DYEING 
 
 the distinctive properties of these two substances, it is proper 
 to consider the gall-nut, which contains them both, the proper- 
 ties of which have been particularly examined, as it is of great 
 use in dyeing. 
 
 The gall-nut is an excrescence found on the young branches 
 of the oak, and chiefly of that species called rouvre, which grows 
 in the Levant, Istria, and the southern departments of France. 
 This excrescence is produced by the puncture of an insect, which 
 deposits eggs in the small incision which it makes in spring. The 
 juice which exudes from this wound becomes thick, accumu- 
 lates, and serves as a shelter to the young insect, till such time 
 as it can make its escape. When there is found no outlet for it, 
 it is found dead in the gall-nut. Sometimes, after it has quitted 
 its cell, other insects come to occupy it. 
 
 Different kinds of nut-galls are distinguished ; some of them 
 are white, others yellow, green, brown, red. Some are of an 
 ash-colour, and even blackish. They vary much in size, and are 
 round or irregular, light or heavy, smooth or covered with tuber- 
 cles. Such as are small, blackish, granular, and dense, are the 
 best. These are known under the name of Aleppo galls, im- 
 ported from that town, from Tripoli and Smyrna. In dyeing, 
 galls are usually distinguished into white and black. 
 
 Nut-galls dissolve almost entirely by long ebullition in water. 
 Sixteen drams yielded Neumann fourteen drams of extract. 
 Alcohol extracted only four grains from the residuum, which 
 weighed two drams. The same quantity treated at first with 
 alcohol, and then with water, afforded 12 drams and 2 scruples 
 of spirituous extract ; the residuuni weighed half a scruple 
 more than in the preceding experiment. The spirituous extract 
 has a stronger and more disagreeable taste than the other.* 
 
 Lewis, Macquer, Monnet, and the Academicians of Dijon, 
 made diflFerent experiments to determine the properties of the 
 astringent which is contained in nut-galls. They observed, that 
 the black colour afforded with solutions of iron depends on a 
 combination formed between the astringent and the iron. To 
 the suspension of these black molecules, the black colour of ink 
 is owing. If the solution be diluted with much water, these 
 
 * " The Chemical Works of Caspar Neumann, Sec.'" by William Lewis.— From 500 gr. 
 of Aleppo galls Sir H. Davy obtained by aqueous infusion 185 gr. of solid matter, of which 
 1-30 was tannin, mucibge 12, gallic acid about 31 , calcareous earth and saline matter 12. — T. 
 
IN GENERAL. 
 
 55 
 
 molecules fall down under the form of a deep blue powder. It 
 is these which are fixed on cloth dyed black. 
 
 We shall, for the. present, confine ourselves to these results, 
 because the properties which the astringent presents on different 
 occasions, and in different circumstances, will be better known 
 by an acquaintance with the two substances here included under 
 the same name. 
 
 To Scheele the discovery of the gallic, acid is due. We shall 
 here introduce the description which this great chemist gave 
 of the method by which he extracted this acid, and of its 
 properties. 
 
 " I passed through a coarse sieve one pound of nut-galls, and 
 infused this powder in about six pints of pure water, in a glass 
 globe, leaving it to act for four days, during which it was fre- 
 quently stirred with a glass rod. I filtered this liquid,* which 
 was limpid, and which had the colour of French wine. I left 
 it freely exposed to the air, in the same glass globe, covered 
 merely with grey paper. This was done in June. A month 
 afterwards I looked into this infusion, and found it covered 
 with a thick pellicle of mouldiness. In other respects it had 
 formed no precipitate, but it had no longer its former astringent 
 taste, and was more acid. I returned this infusion into the 
 same balloon, covered in the same way with paper. Five weeks 
 thereafter I examined it anew, when it was fully half evapor- 
 ated : I found a precipitate in it two fingers thick, and at top 
 a mucous pellicle ; it had lost all its styptic taste, and it still 
 coloured sulphate of iron black. I filtered the infusion, and 
 left it exposed to the air. By the following autumn the greater 
 part was evaporated away ; what remained was mixed with 
 much precipitate. I united these precipitates, and poured cold 
 water upon them. After they had fallen down, I decanted off* 
 the water, and then poured on as much hot water as was neces- 
 sary for their solution. I filtered the whole. The liquid, 
 w^hich was of a yellow-brown, was evaporated at a gentle heat. 
 During the evaporation, one part of it precipitated like a fine 
 sand, and another formed at the bottom in radiated crystals. 
 This salt was grey ; and, notwithstanding repeated solutions 
 
 * " If hot water be employed, or if the mixture be digested with heat, the infusion is 
 not limpid: this determined me to employ cold water, and digestion in the cold." — Joiirn^ 
 de phys. 1787. 
 
50 
 
 BERTHOLLET ON DYEING 
 
 and crystallizations, it was impossible for me to obtain it 
 whiter. - 
 
 ''This salt of gall-nuts comports itself in the following 
 manner : — 
 
 " 1. It has an acid taste, causes effervescence with chalk, and 
 colours infusion of litmus red. 
 
 2. An ounce and a half of boiling water is required for 
 dissolving completely half an ounce of this salt ; but whenever 
 the solution cools, the whole forms a concrete mass, composed 
 of small crystals. Half an ounce requires twelve ounces of cold 
 water for its solution. 
 
 It dissolves very easily in spirit of wine; for half an 
 ounce of this salt, only one-half of boiling spirit is necessary ; 
 but if cold spirit of wine be employed, then for half an ounce 
 two ounces of spirit are required. 
 
 '^4. It readily inflames in a crucible placed in an open fire, 
 melts with the diffusion of an agreeable odour, leaving a charcoal 
 which is difficultly reduced to ashes. 
 
 *' 5. Distilled in a retort, it becomes at first fiuid, and affords 
 an acid phlegm. No oil passes over, but at the end a white 
 sublimate rises, which attaches itself to the neck of the retort, 
 and remains fluid as long as it is hot, but afterwards crystallizes. 
 Much charcoal is found in the retort. This sublimate has 
 nearly the smell and the taste of benzoic acid, or salt of benzoin ; 
 it dissolves equally in water and in spirit of wine ; it reddens 
 infusion of litmus : and what is remarkable, it precipitates 
 metallic solutions with their diflferent colours, and the sulphate 
 of iron black. 
 
 6. The solution of the salt of gall-nut poured into the 
 solution of gold, renders it of a dull green, and eventually 
 throws down a powder which is the gold reduced. 
 
 '' 7. The solution of silver becomes brown, and deposits, with 
 heat, a grey powder, which is reduced silver. 
 
 ''8. The solution of mercury is precipitated of an orange- 
 yellow, 
 
 " 9. The solution of copper aflfords a brown precipitate. 
 '' 10. The vitriolic solution of iron becomes black ; the 
 stronger the solution, the deeper is the colour. 
 
 ''11. Lead dissolved in vinegar is precipitated white. 
 '' 12, Bismuth gives a precipitate of a lemon-yellow\ 
 
IN GENERAL. 
 
 57 
 
 " 13. Molybdic acid becomes of a dull yellow, without any 
 precipitate taking place. 
 
 14. Platinum, zinc, arsenious acid, tin, cobalt, and man- 
 ganese, experience no change. 
 
 15. Solutions of lime, magnesia, alumina, and barytes, are 
 not decomposed; but lime water causes an abundant grey 
 precipitate. 
 
 " 16. The salt of nut-galls is clianged into oxalic acid when 
 nitric acid is distilled from it in the usual way. 
 
 The white precipitate obtained when acetate of lead is 
 thrown down by nut-galls, may be again decomposed by sul- 
 phuric acid, and the salt of nut-galls is thus obtained in its 
 greatest purity. Since the infusion of nut-galls precipitates 
 the acetate of lead, I thought that I might be able to procure 
 this salt in a manner still more expeditious ; but this did not 
 succeed with me, for when I had decomposed this precipitate 
 by means of sulphuric acid, I recovered my infusion of galls 
 with its ordinary astringent taste. 
 
 If gall-nuts be distilled with a violent heat, an acidulous 
 phlegm is obtained, the smell of which is not disagreeable ; no 
 oil passes over, but towards the end a volatile salt rises, like 
 that obtained from the salt of gall-nuts distilled, and which has 
 the same properties. (No. 5.) It hence appears, that this salt 
 exists ready formed in the infusion of gall-nuts, although we 
 cannot obtain it in the way of ordinary crystallization, for it is 
 so intimately united with some mucilaginous principle or other 
 matter, that it cannot be separated from it without some interior 
 movement or fermentation." 
 
 Before prosecuting the examination of the properties of 
 gallic acid, to which, since the experiments of Scheele, chemists 
 ascribed exclusively the effects of astringents, we ought to 
 describe another substance, tannin, which has some properties 
 in common with it, but differs in other respects. 
 
 The art of tanning had been conducted by a blind routine, 
 till Seguin showed that astringents contained a peculiar sub- 
 stance, which, in combining with skin, gave it the properties 
 of tanned leather, and that the tanning effect arose from the 
 combination thus formed. To regulate this art, he had only to 
 determine the circumstances necessary for forming that combi- 
 
58 
 
 BERTHOLLET ON DYEING 
 
 nation, and for giving it the requisite qualities.* He proved 
 that animal glue had the property of forming a similar combina- 
 tion with tannin ; for on mingling a solution of strong glue 
 w^ith an astringent infusion, a substance fell down analogous to 
 tanned leather. By this test he could ascertain the quantity 
 and quality of tannin in an astringent substance, so as to trace 
 and measure its effects in the operations of tanning. 
 
 Since then, chemists have investigated the means of separating 
 the tannin from the gallic acid. For effecting this object, 
 Proust suggested the muriate of tin, which, whatever be its state 
 of oxydation, is decomposed by tannin, but not by gallic acid. 
 The tannate of tin which falls down, is thereafter decomposed 
 by sulphuretted hydrogen, when the tannin is pure.f But this 
 skilful chemist has himself admitted, that his process was imper- 
 fect ; for one portion of the tannin remained in solution, while 
 some of the extractive matter accompanied the portion which 
 precipitated.:}: 
 
 Fielder pretended to separate the gallic acid from the tannin 
 by means of alumina precipitated from its sulphate ;§ but on 
 carefully repeating this process, we have observed that the gallic 
 acid combined also with the alumina, and we have not been able 
 to separate it by this method. When gelatin precipitates tannin, 
 the gallic acid, which remains liquid, retains a portion of it ; 
 for these two substances exercise a mutual action which opposes 
 their separation, and we have in vain tried different processes for 
 removing this obstacle. 
 
 Gallic acid and tannin alike precipitate the solutions of iron. 
 Proust presumes that they cannot combine with the iron, unless 
 it be in the last stage of its oxydation. This opinion has been 
 discussed elsewhere. || We shall content ourselves with remark- 
 ing here, that tannin, and especially gallic acid, form with iron a 
 solution of a black-blue colour, as Delaval and Priestley observed 
 with infusion of nut-galls. There is a decomposition of water ; 
 but the iron can thus be brought only to the lowest degree of 
 oxydizement. The solution of protoxide of iron in acetic acid, 
 is likewise rendered black by tannin or gallic acid. These fcicts 
 
 * Joiini. de manuf. et arts, torn. iii. ; Annal. de cliim. torn. xx. 
 t Annal. de cliim. torn, xxv, ^ Ibid. torn. xli. 
 
 § Jouin. de Van. Mons. torn. i. || Essais do statique chim. torn. ii. 
 
IN GENERAL. 
 
 59 
 
 are sufficient to prove, that if the sHghtly oxydized sulphate and 
 muriate of iron do not produce a black colour with tannin or 
 gallic acid, this effect depends only on the stronger action which 
 the acids in this case exercise on the protoxide of iron, and 
 Proust himself points out this cause; but whatever happens, it 
 is not the less true, as he thinks, that these metallic salts are of 
 use in dyeing, only in so far as they are highly oxydized ; or, 
 that the oxyde of iron absorbs oxygen while it is in the dyeing 
 batli, or during the airing which the stuffs receive on coming out 
 of the bath. 
 
 The same chemist has very justly remarked the difference 
 between. the precipitates produced by tannin and by gallic acid. 
 " The per-sulphate is precipitated by tannin of a somewhat 
 dirty blue ; the deposite is copious, coarse, and black when it is 
 dry. On comparing the precipitate which the sulphate affords 
 with gallic acid, we find that it is very different. The latter is 
 extremely fine, and floats for a long time in the water. It is 
 perfectly black. While the gallate of iron is soluble in acids, 
 the tannate of iron is decomposed by them, parting with its 
 iron while the tanning matter falls." 
 
 Lastly, he has observed, that tannin was not a uniform sub- 
 stance ; but he regards that obtained from catechu, dragon's 
 blood, sumach, and yellow-wood, as possessing properties suffi- 
 ciently well marked to form distinct species. 
 
 Vauquelin has equally found a difference between the tannin 
 of gum-kino, and that of ordinary tan.* He remarks, that it 
 precipitates iron of a green hue, like that of cinchona and 
 rhubarb. 
 
 This difference among the tannins is very perceptible on 
 making comparative experiments with catechu and gall-nuts, or 
 oak-bark. It may be remarked, even on comparing the preci- 
 pitates obtained from gelatin, and those astringents whose pro- 
 perties are most similar, such as gall-nuts and sumach. The 
 tannate produced with sumach falls down less readily ; it is less 
 friable, and less coloured than that afforded by the gall-nut. 
 
 There is such a difference among astringents as to prevent 
 their properties from being considered as identical ; there is a 
 like difference among the tannates produced from the different 
 
 * Annal. cle cliim. torn. xlvi. 
 
60 
 
 BERTHOLLET ON DYEING 
 
 animal substances and the same kind of tannin ; for this pro- 
 perty of forming a combination with tannin does not belong ex- 
 clusively to gelatin. Albumen also possesses it ; but the tannates 
 which it forms are much more friable and less coloured than 
 those due to gelatin. 
 
 From the preceding statement it appears, that astringents may 
 owe the property of colouring black to the two distinct substances, 
 gallic acid and tannin ; and that the latter, far from being iden- 
 tical, has properties which differ more or less in all the vegetables 
 which contain it. One mode of distinguishing substances con- 
 taining tannin alone, is by examining if the precipitate obtained 
 be readily formed, so as to leave the supernatant liquid colour- 
 less. This happens when the tannin of catechu, for example, is 
 precipitated. But if we add a little gallic acid to the solution, 
 the supernatant liquid retains a black colour for a long time. 
 Different astringents examined in this manner, and among 
 the rest oak -bark, appeared to us not to contain gallic acid. 
 Besides gall-nuts, sumach alone exhibited evidence of the acid of 
 galls. That bark must, however, contain but little ; for when 
 it is subjected to the process of Scheele, none of it is obtained. 
 But all the astringents afforded with blue test paper marks of acid- 
 ity, which are even somewhat considerable in catechu, although 
 the presence of gallic acid in it cannot be suspected. Hence, the 
 acidity is not a proof of the existence of the gallic acid, but 
 may be owing to tannin, or a foreign acid. 
 
 White gall-nuts, subjected to the process of Scheele, afford 
 pretty soon an abundant deposite, less coloured than that yielded 
 by black gall-nuts. Nor has it the crystalline appearance, 
 though it is the gallic acid which forms this deposite ; nor is it 
 in a state of combination. We think it probable that the lat- 
 ter kind of gall-nuts contain a greater quantity of it ; though 
 our experiments do not enable us to affirm that this is certainly 
 the case. We have compared the relative quantities of tannin 
 afforded by these two species of gall-nuts, when they are pre- 
 cipitated by gelatin ; we have obtained apparently the same 
 quantity of precipitate from both, so that we cannot yet point 
 out wherein that difference consists which distinguishes these 
 gall-nuts, as is observed in the operations of dyeing, 
 
 A portion of the gallic acid exists certainly in the gall-nut ; 
 but may ?iot some of it be formed in the long space of time 
 
IN GENERAL. 
 
 Gl 
 
 which Scheele's process requires ? We are hitherto unable to 
 answer this question ; but we are led to suppose, that the tannin 
 is in a great measure destroyed, or that it suffers an alteration 
 which permits the gallic acid, which was in a state of combina- 
 tion with it, to crystallize ; for Sclieele remarks, that the infu- 
 sion of gall-nuts loses all its astringent taste. A portion of the 
 tannin is, however, preserved from this change by the action of 
 the gallic acid itself, which retains it in its precipitation and 
 crystallization. 
 
 It is this portion of tannin retained by tlie gallic acid, as ob- 
 tained by the process of Scheele, which affects its colour, and 
 prevents its properties from being properly insulated. Repeat- 
 ed crystallizations only make it brown, by the decomposition 
 occasioned by the heat. We have tried different methods of 
 purifying this acid ; that which succeeded best, consists in treat- 
 ing it with oxyde of tin, newly precipitated from its solu- 
 tion by an acid. The gallic acid then loses its colour, the tannin 
 which altered it being retained by the oxyde, and it crystallizes 
 in very white needles. In this state, it is perfectly similar in 
 its properties to that obtained by sublimation. We have seen 
 that Scheele observed this sublimate, but Deyeux has described 
 it more in detail. He prescribed the precautions which the dis- 
 tillation of the gall-nut requires to obtain this acid sublimate, 
 and he remarked that one part passed over in the liquor, whilst 
 another was decomposed by the fire. Hence, notwithstanding 
 every care, only a small quantity can thus be obtained. Deyeux 
 supposes, that when this acid is exposed to distillation, as well as 
 its combinations with the oxydes, pure oxygen gas is disengaged, 
 and much charcoal is left behind. But we obtained only car- 
 bonic acid during this distillation, which we conducted with the 
 greatest care, with the view of ascertaining the extraordinary 
 result which had been announced. 
 
 The oxyde of tin, by means of which gallic acid is purified, 
 appears to retain a portion of it, and to lessen its quantity a 
 little ; but we have not observed that decomposition of which 
 Proust speaks,* probably because it takes place only in the por- 
 tion combined with the oxyde of tin, of which we neglected the 
 examination ; and as he treated the infusion of nut-galls directly 
 
 * Annal. de cliiuiie, torn. xlii. 
 
62 
 
 BERTHOLLET ON DYEING 
 
 with the oxyde of tin, the quantity of tannin was capable of 
 causing the combination of all the gallic acid associated with it, 
 which does not happen when we thus treat gallic acid retaining 
 but a small portion of tannin. 
 
 Gallic acid may also be purified by means of albumen, which, 
 on coagulating with heat, separates the tannin with it ^ but it 
 retains at the same time gallic acid, and a portion of the albu- 
 men remaining liquid along with the gallic acid, causes this to 
 be diflScultly separable by crystallization. Hence the first 
 method is preferable. 
 
 Gallic acid, in its state of purity, excites an effervescence with 
 the alkaline carbonates, and assumes, on combining with potash 
 and soda, a greenish-blue colour, which becomes so deep by heat, 
 that the liquid appears black at a certain degree of condensation. 
 But it is green if we dilute the liquid, or if we put it into a tube 
 of small diameter. It takes a blue colour with lime, bary tes, and 
 strontian ; but on adding a greater quantity of acid, the colour 
 becomes red, after passing through severed shades. Though it 
 forms precipitates with these alkaline earths, the liquid con- 
 tinues coloured. This acid can scarcely be exposed to ebullition, 
 without assuming a brown shade, and suffering a degree of de- 
 composition. 
 
 The observations now presented, concerning the properties of 
 gallic acid, differ from those of Scheele, since, according to him, 
 this acid forms soluble salts with all the alkaline earths, except- 
 ing lime water. The reason of which is, that his trials were 
 made with solutions in the acids, so that the acid present did 
 not suffer these naturally insoluble salts to precipitate. We 
 conceive, that this acid forms with all the oxydes insoluble salts, 
 whenever this insolubility is not overcome by the action of an 
 acid or an alkali. 
 
 The aflSnities of tannin appear to differ very little from those 
 of gallic acid, at least in the combinations connected with the 
 art of dyeing. The differences of their efifects appear naturally 
 explicable from those of their solubility. 
 
 All the species of tannin seem to surpass gallic acid in their 
 tendency to solidity ; for, in the first place, they form an insolu- 
 ble subs^tance with gelatin, while gallic acid remains in a liquid 
 combination with it ; but albumen, which has more disposition 
 to coagulate than gelatin, can aflPord a solid combination with 
 
IN GENERAL. 
 
 63 
 
 gallic acid. 2. The combination of tannin with the solutions of 
 iron, forms a precipitate which is speedily separated and deposit- 
 ed, whereas gallic acid produces merely a transparent liquid, 
 whose colouring molecules settle slowly, and only in particular 
 circumstances. 3. Proust has observed, that the alkaline car- 
 bonates, and the most part of the very soluble neutral salts, 
 possess the property of precipitating tannin from its solutions, 
 in consequence of the great affinity which they have for water, 
 provided that the proportion of water be not too great.* Sul- 
 phuric acid acts in the same way. 4, The same chemist has 
 observed, and the observation was given in the first edition of 
 these Elements, that when several successive decoctions of gall- 
 nuts are made, the last are desitute of gallic acid. 
 
 It is only, indeed, by this superior tendency to form solid 
 combinations, that the properties of tannin appear to diflfer, in 
 reference to dyeing, from those of several colouring substances, 
 in which it exists in merely a lower degree. Thus the solution 
 of logwood and brazil wood does not form a precipitate with 
 gelatin ; but it produces one with albumen when aided by heat. 
 The solution of yellow-wood (fustic) yields a precipitate with 
 gelatin ; wherefore it contains a substance analogous to tannin, 
 according to the observations of Chaptal and Proust. f The 
 portion which is not precipitated affords a lighter and livelier 
 yellow ; but this portion is. itself separated in a concrete form 
 with albumen. On the one hand, several substances employed 
 as astringents have the property of dyeing different shades of 
 fawn and yellow ; on the other, the colouring substances which 
 have a deep colour, produce also a black colour w^th solutions of 
 iron ; and the blacks on printed goods are commonly obtained 
 from madder. 
 
 The astringents are employed not only to make the baths of 
 the black dye, but also to prepare stuflfs by the operation called 
 galling f which consists in impregnating the stuffs with the as- 
 tringent principle of nut-galls, as will be afterwards stated. 
 
 It became necessary to determine what pa-rt the gallic acid 
 and tannin might each have in this operation. To throw light 
 on this subject, we impregnated with gallic acid specimens of 
 silk, wool, and cotton, and then passed them through a solution 
 
 * Annal. de cliira. torn, xxxiv. 
 
 t Mem. de Plnstitut. torn. ii. 
 
64 
 
 BERTHOLLET ON DYEING 
 
 of iron. None of these specimens was coloured black, and the 
 cotton even took no dye ; but similar specimens, impregnated 
 in the same manner with infusion of nut-galls, took a black 
 colour with solution of iron. On performing the contrary ope- 
 ration, that is to say, impregnating the stuffs first with solution 
 of iron, we had a similar result. We next ascertained, that by 
 means of tannin, gallic acid also entered into combinations with 
 the stuffs. Hence, in the galling, the stuff unites to both the 
 substances which afford black with the solutions of iron. When 
 the stuff is impregnated with tannin alone, it takes also a black 
 colour. Both the substances associated in gall-nuts contri- 
 bute therefore to the black dye ; while tannin, but not 
 gallic acid, produces an analogous effect when it alone is 
 jiresent. It thence follows, that as both the substances can 
 yield a black precipitate with the sulphate of iron, we may thus 
 judge, at least approximatively, of the effect of the different as- 
 tringent substances in dyeing black. 
 
 A discussion has arisen concerning the properties of oak-bark, 
 which, it was asserted, might be substituted with advantage for 
 the gall-nut, even weight for weight, in all black dyeing. In 
 proof of this it was stated, that oak-bark was substituted in the 
 ordinary proportion for the gall-nuts which the hatters of Paris 
 put into their dyeing baths. But this effect proceeds from the 
 circumstance, that the dyeing of hats is produced particularly by 
 logwood, as we may ascertain by applying to a hat any acid, the 
 muriatic, for example, which reddens it immediately, as happens 
 to all the colours derived from logwood. For this dye, therefore, 
 nothing is required but a very little astringent matter, which 
 seems useful merely to deepen by another shade the colour 
 given by the logwood. In fact, a very small quantity of galls 
 enters into the process commonly employed for hats. We have 
 seen an expert hatter employ only one part of gall-nuts to 
 thirty of logwood. 
 
 The present discussion was brought before the Academy of 
 Sciences. The report of its commissioners contains details 
 which may be useful, because they state the proportion of the 
 astringent principle obtained from different substances, and the 
 comparative effect which they produce in dyeing black. For 
 this reason we shall give an extract of it. 
 
 The commissioners, Lavoisier, Vandermonde, Fourcroy, and 
 
IN GENERAL. 
 
 65 
 
 and the author of these Elements, compared in their experi- 
 ments, nut-galls, oak-bark, the raspings of the oak taken from 
 the interior of the wood, the raspings of the alburnum, (white 
 bark) of the oak, logwood, and sumach, in order to determine 
 the proportion of the dyeing principle contained in these sub- 
 stances. They took in succession two ounces of each, which 
 they boiled for half an hour in three pounds of water. This 
 first water was followed up by a second, which underwent the 
 same ebullition, and thus they continued till' these substances 
 seemed to be exhausted. They mixed together the decoctions 
 which they had obtained. They employed a very clear solution 
 of sulphate of iron, the proportion of sulphate and water in 
 which was exactly determined. They judged first of all of 
 the quantity of the astringent principle, by the quantity of sul- 
 phate which each liquor could decompose, and next by the weight 
 of the black precipitate, which was more or less speedily depo- 
 sited, adding to it a sufficient quantity of water. In order to 
 stop precisely at the point where the addition of the sulphate 
 became superfluous, it was necessary to proceed very slowly with 
 the precipitation towards the end, pouring in the solution of the 
 sulphate only drop by drop, and halting at the moment when a 
 new" addition of this substance no longer augmented the intensity 
 of the black colour. When the liquid was too opaque, and 
 when the change of colour could no more be distinguished, a 
 small portion of it was diluted with a good deal of water. To 
 this was added from the end of a glass tube a little of the solu- 
 tion of sulphate of iron, and it was thereby observed if the 
 point of saturation had been attained. Afterwards, when it was 
 wished to make the precipitate fall down in order to be collected, 
 the liquor was diluted with a great deal of water. 
 
 This operation deserves attention ; because it is an easy means 
 of determining in dye-houses the just proportions of astringents 
 and solutions of iron ; but we must bear in mind, that the solu- 
 tions of iron ought to be highly oxydized, in order to produce 
 the greatest effect. Although this consideration was not at- 
 tended to in the experiments of which we are about to state the 
 results, these merit no less confidence, because the same sul- 
 phate of iron was used in all the trials. 
 
 To saturate the decoction of two ounces of nut-galls, three 
 drams and sixty-one grains of sulphate of iron were required. 
 
 . F 
 
66 
 
 BERTHOLLET ON DYEING 
 
 The dry precipitate weighed seven drams and twenty-four 
 grains. 
 
 The decoction of oak-bark was of a deep yellow colour. A 
 small quantity of sulphate of iron gave it a dirty reddish hue ; 
 a more considerable addition made it pass to a brown-black. 
 Eighteen grains of sulphate of iron were necessary to saturate 
 the decoction of two ounces of this bark. The precipitate col- 
 lected and dried was in coarser particles and more difficult to 
 divide. It weighed twenty-two grains. The liher of the oak 
 presented very nearly the same results. 
 
 The decoction of the raspings of the heart of oak required 
 one dram and twenty-four grains of solution, and afforded one 
 dram and twenty-four grains of precipitate. The decoction of 
 the alburnum of oak produced very little precipitate. 
 
 The decoctjon of sumach assumed a violet red colour, when 
 there was added to it a little of the solution of sulphate of iron, 
 of which it required two drams and eighteen grains. The pre- 
 cipitate perfectly resembled that from the nut-galls ; but an ac- 
 cident prevented its weight from being ascertained. 
 
 The decoction of logwood was coloured sapphire blue by the 
 addition of the sulphate of iron. On exceeding the point of 
 saturation, the blue became greenish and dirty. The quantity 
 necessary to reach the point of saturation, was two drams and 
 twelve grains. The circumstances of colour which we have now 
 mentioned, may differ according to the state of oxydizement. 
 
 Trials of dyeing were thereafter made on patterns of woollen 
 cloth. These showed, that the quantities of astringents fitted 
 to give, with an equal weight of the same cloth, a black colour 
 of like intensity, were proportional to the quantities of astrin- 
 gent principle, which had been determined by the experiments 
 on each species ; but the black obtained with the different parts 
 of the oak, did not resist boiling so well as that produced with 
 nut-galls. 
 
 If the astringents submitted to trial in the preceding experi- ^ 
 ments, whose results agree with these of Lewis and Beunie, 
 prove that they cannot be compared weight for weight with gall- 
 nuts, and if sumach alone approaches their effects, we must not 
 thence conclude, that they cannot be employed in dyeing black. 
 But we conceive that it would be much more advantageous to 
 make use of them in galling, than in the dyeing bath, because 
 
IN GENERAL. 
 
 67 
 
 the black molecules which tannin forms with the oxyde of iron 
 are too quickly insulated and precipitated. We have made a 
 pretty deep black, by treating wool, and even silk, in this man- 
 ner with oak-bark. 
 
 It is said in the "Memoirs of Stockholm" for 1763, that we 
 may substitute for nut-galls uva ursi, gathered in autumn and 
 dried with care, so that its leaves continue green. 
 
 If gallic acid, the different species of tannin, and several other 
 colouring substances, such as logwood, brazil wood, and madder, 
 afford with the solutions of iron blacks more or less deep, there 
 must be something in common in the mode of acting of these 
 substances, whatever may be in other respects the difference of 
 their properties. It is our present object to determine this. 
 
 Monnet, and the academicians of Dijon, formerly remarked, 
 that the solution of gall-nut reduced the metal from the solutions 
 of gold and silver. Scheele observed, that gallic acid produced 
 this effect; and Proust has verified this property, not only in 
 tannin, but also in several other colouring substances. We are 
 warranted to conclude, from these facts, that the astringents, and 
 even the colouring substances in general, possess the property of 
 carrying off oxygen from those substances which can yield it 
 easily. 
 
 An observation of Proust informs us, that the astringent 
 produces a similar effect on the solutions of iron. This cele- 
 brated chemist evaporated a solution of iron highly oxydized 
 after precipitating it with nut-galls, and he observed that the 
 liquid, after the evaporation, yielded crystals of the green or 
 slightly oxydized sulphate. It thence results, that the black 
 molecules which fall down contain iron in only the lowest degree 
 of oxydation, since they leave in this state even that which they 
 could not abstract from the acid. 
 
 The black molecules then contain the iron in a black state 
 (protoxyde.) On the other hand, the astringent, in thus absorb- 
 ing oxygen, must experience the same changes that it suffers 
 when it is combined with oxygen ; but the infusion of an astrin- 
 gent deepens in colour, and becomes brown by simple exposure 
 to air ; and we shall see in the following chapter, that it under- 
 goes the same changes which a slight combustion produces, 
 taking this word as signifying a diminution of its oxygen and its 
 hydrogen, so that the carbon becomes predominant, 
 
 f2 
 
68 
 
 BERTHOLLET ON DYEING 
 
 The astringent ought to experience this effect in a high degree, 
 because it contains a great deal of carbon ; for gall-nut leaves, 
 after distillation, more than three-eighths of its weight of char- 
 coal. But when we employ a highly oxydized sulphate, it appears 
 from the experiments of Proust, that a portion of the tannin is 
 altered in its nature by a too energetic action of the oxygen. 
 
 We see now, how the black molecules may result from a com- 
 bination formed of black oxyde of iron and a substance which 
 must assume by degrees the same colour ; why astringents, al- 
 though differing in their other properties, ought to produce an 
 analogous effect ; and finally, why colouring substances of very 
 different kinds afford, with solutions of iron, colours approach- 
 ing more or less to the black hue. 
 
 We may observe that the gallic acid exhibits in its action on 
 solutions of iron a small difference, which seems to announce, 
 that it possesses in a less degree the property of abstracting 
 oxygen from iron. Tannin produces a black colour in a sulphate, 
 so little oxydized that the gallic acid does not change its hue, 
 unless it remains exposed to the air. 
 
 On comparing all the observations advanced on astringents, we 
 may draw the following conclusions : — 
 
 1. Gallic acid cannot serve by itself for the black dye, but it 
 may contribute to the effect caused by the tannin, either by 
 combining with the stuff, or by becoming fixed in the dyeing 
 bath on the galled stuff. 
 
 2. Tannin may serve, without the aid of gallic acid, for the 
 black dye. The different species of tannin possess in this respect 
 different properties as to the quality of the black, which can be 
 determined only by direct experiments. Astringents, besides 
 the quality of the black which they afford, differ also in the 
 quantity. Thus oak-bark, and the other parts of this wood, 
 contain far less astringent matter than gall-nuts. 
 
 3. It is especially for the galling that those astringents which 
 do not contain gallic acid may replace the gall-nuts, because the 
 black molecules which these form fall down too slowly ; and 
 besides, the quantity which must be employed to replace the gall- 
 nuts would be too considerable, and would embarrass the dye-bath. 
 Sumach is, among the astringents at present known, the one 
 which approaches the most to gall-nuts, and which is the fittest 
 to replace them. 
 
IN GENERAL. 
 
 63 
 
 4. With regard to ink, in which the colouring particles must, 
 not precipitate, no known astringent can be substituted for gall- 
 nuts, not even sumach, as Lewis has proved in his excellent ob- 
 servations on this preparation, which deserve to be somewhat 
 dwelt upon.* 
 
 If too large a portion of sulphate of iron be added to the 
 galls, the ink becomes speedily brown, and then passes to yel- 
 low, because the astringent is destroyed by the action of the 
 oxygen which the sulphate of iron affords, or progressively attracts 
 from the atmosphere ; for we shall see, that oxygen eventually 
 destroys those colouring substances with which it is combined in 
 too great quantity. When this accident happens from age, 
 Lewis found, that an infusion of gall-nuts passed over the 
 altered characters restored them ; and Blagden has indicated a 
 means still more efficacious, which is the prussiate of an alkali.f 
 Lewis ascertained, that the best proportion for ink was three 
 parts of gall-nuts to one of sulphate of iron ; that cherry gum 
 and plum-tree gum were as good as gum arable for giving the 
 necessary consistence, and for keeping suspended the black mole- 
 cules which tend to fall ; and that decoction of logwood, employed 
 instead of water for the infusion of the gall-nuts, improved the 
 beauty of the ink. 
 
 We have remarked, that both gallic acid and tannin gave to 
 iron the property of decomposing water, and of forming by this 
 means a solution of iron, which passes from blue or violet to 
 black. Delaval says, that he produced with the solution of this 
 metal and an infusion of nut-galls, the deepest black, and the 
 most indelible ink. J He adds, that on plunging into this tinc- 
 ture silks and woollen stuffs, without adding any acid to it, he 
 obtained them of the deepest and most indestructible black 
 colour. Proust also says, that he would prefer, both as to du- 
 rability and beauty, the ink made by dissolving iron in an infu- 
 sion of gall-nuts, to that which is prepared with the sulphate of 
 iron.§ He remarks in the same place, that the combination of 
 gallic acid and tannin with iron, is not changed into prussiate of 
 iron by the prussiate of potash ; an observation which had al- 
 ready been made by the academicians of Dijon. 
 
 * Lewis's Exper. Essay on the Commerce of the Arts. 
 
 f A solution of ferroprussiate of potash, faintly acidulated, or sulphuretted hydrogen 
 water, are the best restoratives of the characters of faded ink. — T. 
 
 t Expeiimental Inquiries. § Ann. de chim* torn, xxxv. 
 
70 
 
 BERTHOLLET ON DYEING 
 
 We have already mentioned, that Lewis had observed that a 
 decoction of logwood increased the beauty of ink. It is observed, 
 especially in the black dyes, that an addition of logwood gives 
 more lustre to black ; and we shall see, that it is advantageous 
 to fix a blue colour on stuff which is to be dyed black. Now, 
 logwood forms with the oxyde of copper, added to black dyes, a 
 blue colour, which contributes to the beauty of the black by 
 the mixture of that hue. 
 
 We must here remark, that the black of the dyes' is produced 
 only by the condensation of the molecules, which when more 
 diffused enjoy a particular colour, such as blue, dun, or violet. 
 But the mixture of two substances, whose diluted colour is dif- 
 ferent, yields a more intense black. This effect is readily ob- 
 servable in the mixture of two liquids of a deep colour, even 
 when no precipitation occurs by their mutual action. On this 
 occasion we shall adduce an observation of Hooke, quoted by 
 Newton : " If we take two coloured liquids, the one red, the 
 other blue, in sufficient quantity for them to appear very dark, 
 although each part be pretty diaphanous, they will cease to be 
 so on their mixture ; for the one transmitting only red rays, and 
 the other transmitting only blue rays, none will any longer pass 
 through the two liquids mixed together."* 
 
 The result is not, however, exactly such as Newton states it, 
 provided the two liquids are not of a nature to produce a preci- 
 pitate. The colour transmitted is always different from the two 
 insulated colours, and always deeper ; but if the mixture appears 
 opaque in a vessel of a certain size, it will appear still trans- 
 parent in a vessel of a smaller diameter. 
 
 We perceive, therefore, that it must be advantageous, for ob- 
 taining an intense black, to mingle different astringents, the 
 black of which is derived from different colours . Perhaps gallic 
 acid may thereby augment the black occasioned by the tannin ; 
 and perhaps it would be beneficial to employ a mixture of dif- 
 ferent kinds of tannin in galling. 
 
 We have hitherto considered tannin only in reference to black 
 dyes ; but its use is not confined to this kind of dyeing : it 
 exerts on several other colouring particles an affinity analogous 
 to what we have observed between it and gallic acid ; whence it 
 serves to fix them on stuffs, and to communicate stability to them. 
 
 * Optics, vol. i. 
 
IN GENERAL. 
 
 71 
 
 In this point of view it may be compared to mordants ; but as 
 it possesses in itself a colour which has a tinge of yellow or dun, 
 and as the effect of one colour must be to modify and darken 
 that peculiar to another colouring substance, the use of astrin- 
 gents as a mordant does not suit bright colours, particularly those 
 of little intensity. 
 
 CHAPTER IV. 
 
 Of the action of different Substances, particularly of Air and 
 Light, on Colours. 
 
 Hitherto we have considered the colouring molecules only 
 as substances forming different combinations, by which their 
 properties are modified ; but they may yield more or less easily 
 to the action of other substances, which destroy the combination 
 thus formed, or which by a sur-composition deteriorate their 
 properties. They may suffer the alterations produced by exter- 
 nal agents, either from the mutual action of their principles, or 
 of the substances which form a combination with them. 
 
 The power of resisting vegetable acids, alkalies, soap, and 
 above all, the action of air and light, constitutes the durability 
 of a colour ; but this property has a very unequal standard, ac- 
 cording to the nature of the colour and the species of stuff ; for 
 'in certain silk dyes the same permanence is not required as in 
 those of wool. 
 
 There is no obscurity in the action of water, alkalies, acids, 
 and soap : a solution is effected by means of these agents, or a 
 small portion of acid or alkali unites to the combination which 
 forms the colour ; for this is not destroyed, but merely changed, 
 and can be restored by removing the acid or the alkali. 
 
 This is not the case with the action of air and light. Till 
 lately, it was not known in what this action consisted ; but we 
 are at the present day much farther advanced in this theory, 
 which we proceed to detail. 
 
 Scheele had observed, that oxygenated muriatic acid (chlorine) 
 rendered the vegetable colours yellow, and he ascribed this 
 effect to the property which it possesses, of seizing the phlogis- 
 ton which enters into their composition. 
 
72 
 
 BERTHOLLET ON DYEING 
 
 The author of the Elements proved,* that the properties of 
 oxygenated muriatic acid (chlorine) arose from the oxygen, 
 which it readily yielded to the substances exposed to its action ; 
 that it commonly brought the colouring particles to a yellow 
 hue ; but that, by a continuance of its action, it destroyed their 
 colour, though he did not determine wherein this action 
 consisted.f 
 
 With regard to the action exercised by oxygen on the colour- 
 ing particles, Fourcroy afterwards made several observations 
 which throw much light on the changes which they experience, 
 especially when their aqueous solution remains exposed to the 
 air, or when it undergoes ebullition. He remarked that, by the 
 action of the air, vegetable decoctions formed pellicles, which 
 lost their solubility, and progressively changed their colour. He 
 traced the gradatioias of colour thus obtained, and concluded 
 from his observations, that oxygen entered into the composition 
 of these colouring particles ; that when it combined with them 
 their hue changed ; that the more of it they absorbed, the more 
 fixed their colour became ; and, that the mode of procuring un- 
 changeable colours for painting was, to select those which had 
 been exposed to the action of chlorine. | 
 
 The author of these Elements sought to determine more 
 peculiarly wherein the action of the air consisted, when it com- 
 bines with the colouiing particles, especially by examining the 
 operation of chlorine upon them.§ 
 
 We shall copy literally what had been stated in the first edition 
 of these Elements, because Bancroft, whose authority has great 
 weight v/ith us, has attempted to refute the theory there estab- 
 lished, and because we are desirous of enabling our readers to 
 weigh his reasons, and the grounds of our opinion. 
 
 We must distinguish, in reference to the effects of the air, 
 between the colours of metallic oxydes and those of the colour- 
 ing particles. I have proved, that the modifications of the 
 former are owing entirely to the different proportions of oxygen ; 
 but I have been led by my observations to a different opinion 
 concerning the modifications of the other colouring particles. 
 
 * Mem. de Tacad. 1785. 
 
 f For the theory of blanching by chlorine, see Note § to page 38. — T. 
 X Annal. dd chimie, torn. v. 
 
 § Annal. dc chimie, torn, vi Mem. sur Paction que Tacide muriatique oxygen^ excrce 
 gur les parties colorantcs. 
 
IN GENERAL. 
 
 73 
 
 " I have observed, that chlorine exhibited different phenomena 
 with the colouring particles ; that sometimes it discharged their 
 colour, rendering them white : that more frequently it caused 
 them to become yellow, dun, brown, and black, according to the 
 intensity of its action ; and that, when their colour seemed to 
 be discharged or blanched, heat, or the lapse of time, was suffi- 
 cient to render them yellow. 
 
 " I have compared the effect produced by chlorine, when the 
 colouring particles are rendered yellow, fawn or brown, with the 
 effects of a slight combustion ; and I have shown that they were 
 identical, that they were owing to the destruction of the hydro- 
 gen, which, combining with oxygen more easily, and at a lower 
 temperature than charcoal, leaves this predominant, whence the 
 natural colour of charcoal is blended more or less with that 
 which pre-existed. 
 
 " This effect is very perceptible, when sugar, indigo, or the 
 infusion of nut-galls or of sumach, is submitted to the action of 
 chlorine. The sugar and indigo assume a deep colour, and 
 afford unequivocal traces of a slight combustion. The infusion 
 of gall-nuts and of sumach forms a black deposite, which is char- 
 coal nearly pure." 
 
 These phenomena are analogous to those observed in the 
 distillation of an organic substance. In proportion as its 
 hydrogen is disengaged under the form of oil, or in the state of 
 gas, the substance turns yellow, and eventually only a black 
 charcoal remains. If we expel the hydrogen of an oil by heat, 
 it becomes brown. 
 
 Other experiments which I have made on alcohol and ether 
 have satisfied me, that oxygen united to muriatic acid possessed 
 the property of combining with the hydrogen, which abounds 
 in these substances, so as to form water. 
 
 When, therefore, chlorine renders a colour yellow, dun, or 
 brown, this effect is caused by the colouring substance suffering 
 a slight combustion, in which a greater or less part of its hydro- 
 gen has formed water ; whence the carbon becoming predomi- 
 nant, communicates its peculiar colour. 
 
 I have shown, that the art of bleaching goods depended on 
 this alteration of the colouring particles by the oxygen of the 
 atmosphere, the dew, and chlorine. The colouring particles 
 of flax become soluble in the alkali of the leys, which must be 
 
74 
 
 BERTHOLLET ON DYEING 
 
 alternated with the action of the oxygen. We may afterwards 
 precipitate from the alkali these colouring particles, which when 
 dried and collected are black. They therefore prove the truth 
 of this theory, both by the colour they have assumed, and by 
 the quantity of carbon they afford in their analysis. 
 
 " The alkaline solution of the colouring particles of the cloth, 
 which is blackish-brown, loses nearly its whole colour on pour- 
 ing into it a quantity of chlorine ; and the same effect may be 
 observed with several other substances, which have derived a 
 colour from a commencement of combustion. 
 
 A cloth may appear white, and yet become yellow in process 
 of time, especially if it be exposed to certain degrees of heat, 
 when the oxygenized particles have not been removed by a 
 sufficiently efficacious ley. In like manner, the green particles 
 of vegetables are blanched by the chlorine, but become yellow 
 on ebullition. 
 
 These facts prove, that oxygen may whiten or render pale 
 the colouring particles with which it combines, whether it has 
 begun to produce on them the effects of combustion, or whether 
 it may produce these effects but slowly, and especially when this 
 combustion is subjected to a certain degree of heat. 
 
 It is very probable that, in every ease, one portion of the 
 oxygen unites with the colouring particles without combining 
 particularly with the hydrogen, and that thereby the colouring 
 particles of the flax have become, from the action of the oxygen, 
 more soluble in the alkalies than they previously were. 
 
 The action of oxygen has an undoubted influence, in several 
 other circumstances, on the changes effected in the colouring 
 particles of vegetables. These particles are formed chiefly in 
 the leaves, the flowers, and the inner bark of trees. By degrees 
 they experience a slight combustion, either by the action of the 
 atmospheric air which surrounds them, or by that of the air 
 carried into the interior of the vegetables by particular vessels ; 
 whence it happens that the most part of trees contain colouring 
 particles of a dun hue, verging more or less on yellow, red, or 
 brown, which, by means of this combustion, thicken, and are 
 eventually thrown out of the vascular fibres of the bark, of 
 which I have found them to form the greater proportion. 
 
 " These observations teach us in what manner the air acts on 
 colouring substances of an animal or vegetable nature : it first 
 
o 
 
 IN GENERi\L. 
 
 75 
 
 combines with them, making them weaker and paler, and gra- 
 dually establishes a slight combustion, by which the hydrogen 
 in their composition is destroyed ; they pass to yellow, russet, 
 dun ; their affinity with the stuff seems to diminish, they are 
 detached from it, they are carried off by the water ; and all 
 these effects vary, and are finished more or less quickly, and 
 more or less completely, according to the nature of the colouring 
 particles, or rather according to the properties which they possess 
 in their actual state of combination. 
 
 The changes which occur in colours, arising from the com- 
 bination of the colouring particles with the metallic oxydes, are 
 a compound effect of the change produced in the colouring 
 particles and the metallic oxyde. 
 
 " The light of the sun accelerates greatly the destruction of 
 colours ; it ought then (if the theory which I have laid down be 
 just) to favour the combination of the oxygen, and the combustion 
 thereby produced. 
 
 Sennebier has given a great number of interesting observa- 
 tions, concerning the effects which light occasions in the different 
 substances, and particularly in colours; he ascribes these effects 
 to a direct combination of the light with these substances."* 
 
 The influence of light on the colour of woods has been long 
 ago remarked. In obscurity, they retain their natural state ; 
 but when exposed to light, become yellow, brov/n, and pass 
 into other shades. Sennebier observed the differences exhibited 
 by several species of wood in this respect. He found that the 
 changes were proportional to the vivacity of the light ; that they 
 took place even under water ; that moistened woods, however, 
 suffered changes less rapidly than those which were dry; that 
 it required several folds of ribbon to preserve a wood entirely ; 
 that black paper was sufficient, but with paper of other colours 
 the alteration was not prevented. A simple envelope of white 
 paper was insufficient, but two intercepted the action of the 
 light. 
 
 " This skilful philosopher extended his experiments to a great 
 
 * "Mem. physico chimiqne siir rinfluence de la lumi^re solaire," &c. tomes ii. et iii. 
 This philosopher, to whom physics is under so many ohligations, has adopted, in a great 
 measure, (Physiol, veget. torn, v.) the ideas exposed here ; and among which we must 
 distinguish between the positive consequences of observation, and the applications that are 
 yet merely conjectural. 
 
76 
 
 BERTHOLLET ON DYEING 
 
 number of vegetable substances. They may serve to clear up 
 several phenomena of vegetation, w^ith which I have at present 
 no concern. But to prove wherein the action of the sun on 
 colours consists, it would be sufficient to examine the pheno- 
 mena exhibited by the solution of the green particles of vege- 
 tables in alcohol. 
 
 " If this solution, which is of a fine green colour, be exposed 
 to the light of the sun, it speedily takes an olive tint, and then 
 is discharged in some minutes. If the light has little vivacity, 
 the effect is much slower ; but in perfect darkness, the colour is 
 preserved without alteration, or at least the alteration is very 
 tardy. Sennebier says that an alkali restores the green colour; 
 but if the liquid has experienced all the discoloration which it 
 can undergo, the alkali produces no change on it. He remarked, 
 that in azote or nitrogen the colour was not affected, and that 
 it suffered no change if the flask was full, 
 
 " I inverted over mercury a flask half filled with the green 
 solution, and exposed it to the light of the sun. When the 
 colour was discharged, the mercury was found to have risen in 
 the flask, and consequently the vital air had been absorbed, the 
 oxygen having combined with the colouring particles. I have 
 not observed the deposite of which Sennebier speaks ; the liquid 
 remained transparent, and of a clear yellow colour. 
 
 I evaporated this liquor; its colour soon deepened, becom- 
 ing brown ; and the residuum was black, and in a carbonaceous 
 state. 
 
 The light acted therefore by favouring the absorption of 
 oxygen and the combustion of the colouring matter. At first, 
 the marks of the combustion are not perceptible, the liquid 
 preserving merely a feeble yellow colour; but the combustion 
 is soon consummated by the action of the heat, when the liquid 
 turns brown, and leaves a black residuum. If the vessel in 
 which the liquid is put contains no oxygen gas, the light has 
 no action on the colouring particles. The azotic gas suffers no 
 diminution. 
 
 ^' The circumstance of ribbons and a simple white paper not 
 protecting from the action of light merits attention. It can 
 penetrate through envelopes vv^hich appear to us opaque, so as to 
 exert its energy at greater or less depths. 
 
 *'Beccaria, and after him Sennebier, have compared the 
 
IN GENERAL, 
 
 77 
 
 effects which light produces on ribbons of different colours ; 
 but the differences which they observed ought to be ascribed to 
 the nature of the colouring substances with which the ribbons 
 were dyed, rather than to the colours themselves ; for a ribbon 
 dyed with brazil wood will lose its colour much more speedily 
 than one dyed with cochineal, though the shade be the same. 
 
 Although light greatly accelerates the combustion of the 
 colouring particles, and though its presence even appears neces- 
 sary foi' the destruction of some of them, yet this effect takes 
 place in other circumstances without the aid of light. Having 
 placed several plants in darkness, in contact with oxygen gas, 
 I observed that some of them absorbed it. I also observed, 
 that the rose changed and took a darker tint without the contafct 
 of the air, undoubtedly because it contains a little oxygen, 
 whose state of combination becomes afterwards more intimate ; 
 but several species of flowers preserved their colour perfectly 
 well in azote. 
 
 " I placed tincture of litmus in contact with oxygen over 
 mercury, in darkness, and in the svm-liglit : the first was pre- 
 served very long without alteration, while the gas experienced 
 no diminution; the second lost much of its colour, it became 
 red, the oxygen gas was in a great measure absorbed, and a 
 little carbonic acid was formed, which undoubtedly produced 
 the change of the blue colour into red. 
 
 " This observation may give some idea of the changes of 
 colours occasioned by a peculiar disposition of the principles 
 existing in a vegetable substance, when it experiences, by com- 
 bination with oxygen, the effects of a slight combustion, which 
 may generate some acid, as in the leaves which redden in autumn 
 previous to their turning yellow, and in the streaks observable 
 in flowers of languid vegetation- 
 
 It is therefore proved, that light promotes the absorption 
 of oxygen by the colouring particles, and that a combustion 
 thus takes place, the ordinary effect of which is a predominance 
 of carbonaceous particles. 
 
 To the same cause must be ^scribed the decay remarked 
 in stuffs themselves by the action of light. ^ Among several 
 examples which T might adduce,' says Dufay, ' I shall mention 
 only a curtain of fugitive crimson taffeta, which had remained 
 long stretched behind a window : all the parts which were 
 
78 
 
 BERTHOLLET ON DYEING 
 
 opposite the panes of glass were entirely deprived of colour, 
 whilst those which corresponded to the wood of the casement 
 were much less faded ; and further, the silk itself was almost 
 destroyed in the discoloured parts, where the curtain could be 
 torn with the slightest effort, whilst it retained elsewhere nearly 
 its usual strength.'* 
 
 The colouring substances resist, therefore, the action of the 
 air in a greater or less degree, according as they are more or 
 less disposed to combine with oxygen, and to suffer from its 
 action a combustion more or less speedy, more or less con- 
 siderable. Light favours this effect in several circumstances ; 
 its concurrence is essential ; but the insulated colouring particles 
 are much more subject to this combustion than when they are 
 combined with a substance such as alumina, whether this de- 
 fends them by its incombustibility, or whether the force of 
 affinity binds them up, so to speak, and enfeebles their action 
 on other substances ; and in this principally consists the utility 
 of mordants. Finally, the latter combination acquires still 
 greater unchangeableness when it is intimately united with the 
 stuff. 
 
 " Thus the colouring matter of cochineal is easily dissolved in 
 water, and its colour is quickly affected in the air. When com- 
 bined with the oxyde of tin, it is much more lively, and scarcely 
 soluble in water ; but it is still readily altered by the air and by 
 chlorine. When it exists in triple combination with woollen 
 stuff, it resists these agents better. 
 
 **From these observations we are not to conclude that all the 
 yellow colours proceed from the carbonaceous portion of the 
 colouring substances; different compositions may afford the 
 same colour. Thus indigo is entirely different from the blue 
 of our flowers, from the blue of oxyde of copper, and from 
 Prussian blue. 
 
 Nor do I assert that oxygen may not unite in a small pro- 
 portion with some colouring particles, without weakening their 
 colour, or changing it to yellow. We shall find in the chapter 
 on indigo, that this substance possesses a green colour when 
 combined with an alkali, lime, or a metallic oxyde; but that it 
 resumes its colour, and separates from these solvents, on re- 
 
 * Mem. de racademie, 1737. 
 
IN GENERAL. 
 
 79 
 
 covering a small portion of the oxygen which it had lost. The 
 liquor of the buccinum, which served for djeing purple, is 
 naturally yellowish ; on being exposed to the air, and particularly 
 to the sun, it passes speedily through different shades, and 
 finally assumes that colour which was deemed so precious by the 
 ancients.* 
 
 It may be regarded even as a general fact, that colours 
 assume more brilliancy by combining with a small portion of 
 oxygen. It thence happens that the stuffs, as they come out of 
 the bath, ought to be agitated iti the air, and sometimes with- 
 drawn from the bath at intervals, in order to expose them to the 
 atmosphere. But the quantity of oxygen which fixes itself, 
 thus contributing to the lustre of the colour, is very inconsider- 
 able in some cases, and the degradation of shade soon begins. 
 
 The action of the air affects not only the colouring particles 
 and the stuff, but also the metallic oxydes which serve as an in- 
 termedium to them ; because the oxydes, which are at first de- 
 prived of a portion of their oxygen by the colouring particles, 
 may recover some of it. Hence, the oxydes, whose colour varies 
 with the proportion of their oxygen, exert an influence on the 
 changes experienced by the stuff. The alteration of the colour- 
 ing particles must also contribute to this effect. 
 
 " I have stated, that the colouring particles, in a state of com- 
 bination, were less liable to be affected by the action of the air 
 than when they are insulated. This is a circumstance very 
 commonly observed. There are, however^ particular exceptions. 
 Alkali produces a contrary effect. I half filled a phial with an 
 infusion of cochineal, and exposed it to light over mercury ; 
 another phial, similarly situated, contained an infusion of co- 
 chineal made with a little tartar ; and in a third, some alkali was 
 added to the infusion. The second phial suffered least altera- 
 tion in the same space of time, accompanied with the least 
 absorption of air. 
 
 ^^In the third, the liquid became at first brown, then the 
 colour disappeared, and the absorption of the air, although in- 
 considerable, was greater than in the two others. By evapora- 
 
 * "Decouverte cVune nouvelle teinture de pourpre, &c. par Reaumur; Mem. de Taca- 
 demie, ]7ll." According to the testimony of Eudocia, the purple took its lustre, and 
 arrived at its perfection, only by exposure to the sunbeams. 
 
80 
 
 BERTHOLLET ON DYEING 
 
 tion it assumed a brown colour, and the residuum was yellow- 
 brown. 
 
 I have made similar experiments on several colouring sub- 
 stances : the alkali deepened their colour, VN^hicli grew more and 
 more brown ; and it likewise favoured the absorption of the air. 
 Madder alone seemed to form an exception ; its colour, which at 
 first became deeper, was more durable than that of the infusion 
 without alkali. 
 
 The usual effect of alkalies on colouring particles is con- 
 formable to what they produce on several other substances, such 
 as sulphur. They promote the absorption of the air, because 
 they have a strong affinity for the substance w^hich results from 
 this absorption. 
 
 From this operation of alkalies, I explain a fact observed 
 by M. Becker.* When alkalies have rendered a vegetable in- 
 fusion green, we see it pass by degrees to yellow, if it be left 
 exposed to the air ; and when the yellow is once established, 
 acids can no more bring back the primitive colour. But this 
 effect does not occur when we abandon in the same way, for 
 some time, a vegetable colour which has been turned red by an 
 acid. We must, however, except those acids which act by giving 
 up their oxygen ; for the colour is equally destroyed in that 
 case." 
 
 Bancroft advances, in opposition to what we have thus stated : 
 1. That the colouring substances experience, from the action of 
 acids and other bodies, an alteration which cannot be compared 
 to combustion. In the preceding explanations, however, the 
 question is merely about the kind of alteration which depends 
 on the action of oxygen. 
 
 2. That oxygen, far from destroying colours, is sometimes 
 necessary to them ] for example, to indigo. Is not this what we 
 have said ? But we distinguish between the cases where it be- 
 comes an element of the colour, and those where its action is 
 destructive. 
 
 3. That the changes of colours produced by the air cannot 
 be ascribed to the carbon, which becomes predominant, because 
 several substances contain much carbon without having a colour 
 similar to what is ascribed to its excess, and because the colour 
 of carbon itself is due to oxygenation. 
 
 * Specimen, &c. 
 
IN GENERAL, 
 
 81 
 
 We have attempted to demonstrate, that the changes pro- 
 duced by the air when its action is favoured by light, are espe- 
 cially owing to a combination of the hydrogen of the colouring 
 substance with oxygen, whether this be absorbed from the 
 atmosphere, or be present in less intimate combination, either 
 in the colouring substance itself, or in the oxyde united with it;, 
 and that the effect was similar to a slow combustion, in which a 
 combination of hydrogen with oxygen was formed, so as to leave 
 a residuum containing a redundancy of carbon. This opinion 
 seems to be an immediate consequence of the phenomena that 
 have been detailed, which indicate the gradual decomposition of 
 all bodies containing hydrogen on being subjected to this action 
 of oxygen. 
 
 Bancroft regards charcoal as an oxyde, which he compares to 
 the oxyde of manganese. We do not think it necessary to take 
 up time in refuting his opinion'^ concerning the nature of char- 
 coal. The only object is to know, if, in the circumstances under 
 discussion, the change of colour may not have some analogy 
 with what is observed when a vegetable substance is distilled. 
 He pretends that this substance becomes in that case brown, 
 merely by the accession of oxygen from the atmosphere. Let 
 a distillation be made out of contact of the atmospheric air, 
 and he will observe that the same alteration of colour takes 
 place, either from the formation of water, or from the dis- 
 engagement of a greater proportion of hydrogen, so that the 
 properties of the charcoal become predominant. 
 
 Bancroft maintains, that the theory which he combats is 
 founded only on the phenomena of the colouring particles of 
 the cloth. The text which we have adduced proves the con- 
 trary, and we might easily multiply examples. 
 
 It was incorrect, according to him, to confound the effects of 
 the combination of oxygen gas with those of the chlorine ; but 
 we do not find in his work the experiments which he announced 
 as calculated to prove, that the chlorine often produces effects 
 contrary to those arising from the combination of oxygen. 
 
 We ought, undoubtedly, in comparing the effects of chlorine 
 with those of the absorption of oxygen gas, to take into con- 
 sideration the greater condensation of oxygen in the former, 
 
 Essai dc stutiqiie cliimiquo, torn. ii. 
 G 
 
82 
 
 BERTHOLLET ON DYEING 
 
 and the natural effects of muriatic acid.* We should also dis- 
 tinguish between the effects which the chlorine can produce, 
 when it has made the whole colour disappear, as we have seen, 
 and the effects due to the combination of its oxygen with the 
 hydrogen of the colouring particles, as well as those arising 
 from the difference of the colours, of which we shall speak in 
 the sequel. 
 
 The more lively oxygenation, by means of chlorine, prevents 
 us from obtaining readily those gradations of colour which are. 
 produced by the action of the air, and which become more 
 difficult the further they advance. Thus, conformably to the 
 observation of Fourcroy, when a colouring substance has experi- 
 enced some change by this action, it becomes, in similar cir- 
 cumstances, more fixed ; but in this first effect, a part of its 
 hydrogen must have entered into combination. 
 
 While we conceive that we have been able to refute the 
 objections of Bancroft concerning at least the most usual cause 
 of the degradation of colours by air and light, we admit, that 
 the consequences of the opinion which we endeavour to main- 
 tain, should not have been extended to the phenomena that 
 we are now going to examine, although this has been done with 
 mucli diffidence, and without overstepping the limits of a simple 
 conjecture. 
 
 Nitric acid, chlorine, and sulphurous acid, exercise on animal 
 substances a peculiar action, which merits examination, because 
 it may furnish some processes to dyeing. 
 
 Brunwiserf having observed that woods assumed different 
 colours on exposure to air, sought to determine the origin of 
 these colours, and to produce them artificially. He remarked, 
 that on moistening with nitric acid the surface of wood, princi-^ 
 pally young wood not very dry, it took a yellow colour. On 
 performing the same operation with muriatic acid, and sulphuric 
 acid, the wood assumed a violet colour ; and he looked upon 
 this violet as composed of a blue and a red colour. From these 
 observations he concluded, that as all the colours are produced 
 
 * Translating M. Berthollet*s idea into the modern language of chemistry, we would 
 say, " Take into consideration the intense affinity of chlorine for hydrogen, the liberation of 
 oxygen from the decomposed water, and the peculiar action of muriatic acid." 
 
 f Versuche mit mineralischen sauern Geistern, aus den holzern Farben zu ziehen, 1770. 
 In Abhaadlungen der Baierischen Akademie. 
 
IN GENERAL. 
 
 83 
 
 by the mixture of yellow, blue, and red, those which we observe 
 in the leaves, fruits, and flowers, arise from the colouring par- 
 ticles which exist in the wood, but which are disguised by an 
 alkali ; that the mineral acids, on seizing this alkali, set the 
 colouring particles at liberty ; and that the fixed air, in pene- 
 trating into the leaves, the fruits, and the flowers, naturally 
 produced the same effect, by combining with the alkali which 
 masked them. 
 
 The author attempted to apply to the arts his pretended 
 discovery as follows.* After watering chips of wood with nitric 
 acid, he poured water upon them, filtered the liquid, and made 
 use of it to dye wool, silk, and goat's hair, of a durable yellow ; 
 a colour due, by his account, to the yellow particles which were 
 contained in the wood, and which had been extracted or set at 
 liberty by the nitric acid. 
 
 De la Folic relates,f that having plunged a skein of white 
 silk into nitric acid, or aquafortis, of the usual commercial 
 strength, the silk assumed in three or four minutes a fine 
 jonquil-yellow hue. He washed it repeatedly with water, that 
 no adhering acid might remain to alter it. This colour resisted 
 several tests to which he exposed it, and the silk retained its 
 primitive lustre. When dipped into an alkaline solution, it 
 takes a beautiful orange colour. 
 
 Several experiments on this process are to be found in a 
 dissertation published by Gmelin.;]: He says,, that he has given 
 a fine sulphur colour to silk by keeping it for a day in cold 
 nitric acid, or for a few hours when the acid was hot. Ebul- 
 lition with soap and water impaired the lustre of this colour. 
 It became of a fine lemon colour by keeping' the silk for twelve 
 hours in an alkaline solution ; and it assumed a fine gold hue 
 when this solution was hot. 
 
 All solutions of metals in nitric acid gave to silk a yellow 
 colour more or less deep, as well as the solution of alumina in 
 the same acid. But the solution of calcareous earth and of 
 magnesia produced no effect. 
 
 * Entdeckung verschiedener vegetabilischen farberaaterialem seiden und wollen zeiige 
 schon und dauerhaft gelb zu Farben, 1771. 
 f Journ. de Phye. torn. iv. p. 349. 
 
 X J. Frieder. Gmelin, Prof. GOtting. de tingendo j)er nitri acidum, sivo nudum, sivc 
 terra aut metallo saturatum serico. Erfurti, 1785, 
 
 g2 
 
84 
 
 BERTHOLLET ON DYEING 
 
 The solution of tin mixed with solution of gold yielded, ac- 
 cording to La Folic,* a purple colour, which fixes upon silk; 
 hut Gmelin obtained by this process only a common yellow. 
 He proves also, that the different yellows w^hich Struve said he 
 had obtained from different metallic solutions, depend merely 
 on the acid of these solutions, f The only exception, perhaps, 
 is the solution of mercury, which gave silk a copper colour. 
 
 Baume describes a process capable of protecting silk from 
 any alteration. J " A mixture of two drams of nitrous acid and 
 one pound of alcohol is made, into which a few ounces of manu- 
 factured silk are put, either yellow, or previously whitened, for 
 that is absolutely indifferent. The vessel containing them is 
 placed for about 24 hours in a water-bath heated to 30 or 40 
 degrees R. (100^ or 120^ Fahr.) The silk becomes of a dull 
 yellowish-brown. It is now repeatedly washed in water, to 
 remove the acid with which it was impregnated. It is then 
 scoured with soap in the usual way ; afterwards washed to free 
 it from the soap water, and finally dried. 
 
 If we view this silk in the sun, it shines like threads of gold. 
 By the same process we may give silk different shades of the 
 above colour, and form what is called in dyeing degradation of 
 colour from white to the full tint. For this purpose it is suffi- 
 cient to let the silk infuse for a shorter time ; the first shade is 
 procured by one hour's infusion, and the others in proportion to 
 their duration." 
 
 Bergmann was aware of this process, when he published his 
 notes on the Treatise of Scheffer.§ He says, that ordinary 
 aquafortis gives, in three or four minutes, to wool and silk, a 
 bright, fine, and durable yellow ; that they must be immediately 
 washed; and the more dephlogisticated the acid (the more 
 colourless), the greater effect it produces. 
 
 To recapitulate : nitric acid, diluted with a certain quantity 
 of water, gives silk a yellow colour, of more or less depth, accord- 
 ing to the concentration of the acid, the temperature, and the 
 time of immersion : the silk must be carefully washed on coming 
 out of the acid. This colour has a good deal of lustre. We may 
 
 * Journ. de physique, torn. viii. 
 
 + Bernerisches Magazin der Natiukunst und Wissenchaften, vol. i. 
 J Ann. de chimic, torn. xvii. § Essai sur Tart de la teinture. 
 
IN GENERAL. 
 
 85 
 
 deepen the shade without perceptibly affecting the silk. This 
 process may be nsefally applied, not only to silk, but to other 
 animal substances ; and the colour may be modified by alkalies. 
 
 The solution (nitric) of calcareous earth, and that of magnesia, 
 produce no effect on silk, because they do not retain an excess 
 of acid. Solutions of alumina, and of all the metallic substances, 
 produce on the contrary a yellow of greater or less depth, be- 
 cause they all retain a greater or less excess of acid ; and it is 
 the acid in excess which acts on the silk as free acid. It was 
 the acid alone which coloured the animal substances yellow, 
 in the experiments of Brunwiser, and not the extracts of the 
 wood. 
 
 The yellow colour is not owing to iron, as De la Folic pre- 
 tended ; for the purest nitric acid, which consequently contains 
 no iron, produces it as well as that in which the presence of a 
 little of this metal may be suspected. 
 
 If silk be put into concentrated nitric acid, it speedily takes 
 a deep yellow colour^ loses its force of cohesion, and is dissolved. 
 During this solution, the azote which enters into the compo- 
 sition of animal substances is disengaged, occasioning a long 
 effervescence.* If heat be applied, much nitrous gas is formed, 
 and the liquid at first assumes a dark colour, becoming brown. 
 At this period, the oxygen of the nitric acid combines particu- 
 larly with the hydrogen which abounds in animal substances, 
 serving to form the oil extracted by distillation, which renders 
 them so combustible. One part of the oxygen enters into a 
 new combination, forming oxalic acid ; but, at the same time, 
 another substance of a detonating quality is produced, which is 
 yellow and bitter, whence it has been called amer by Welter.f 
 
 Welter extracted this substance not only from silk, but from 
 other animal substances ; and he observed, that it communicated 
 to white silk a beautiful yellow, which washing with water did 
 not impair. 
 
 It is to be desired that this expert chemist had prosecuted 
 his trials, in order to determine more exactly both the nature of 
 this substance and the circumstances of its production; we 
 might perhaps be able to deduce from it the cause of the yellow 
 colour which nitric acid communicates to animal substances 
 
 * Mem. de Tacad. 1785. f Ann. de chimie, torn. xxix. 
 
86 
 
 BERTHOLLET ON DYEING 
 
 when the action of this acid is less lively than that just de- 
 scribed. Perhaps, when it is confined to the surface of the silk, 
 the formation of this substance on it is determined by the ten- 
 dency of the silk to combination. 
 
 Chlorine gives likewise a yellow colour to animal substances ; 
 but this does not seem to be a general effect. We have seen 
 skins bleached by chlorine, and this colour is always much more 
 intense than that owing to nitric acid : thus, it appears to differ 
 from it, and to arise merely from a feeble combination of the 
 oxygen with the animal substance, which, when it is white, 
 takes a nearly similar hue on long exposure to the atmosphere. 
 It is also to be remarked, that the action of chlorine weakens 
 animal substances more easily than nitric acid, although the 
 latter be more condensed. 
 
 Sulphurous acid exercises also a peculiar action, which de- 
 serves more consideration, as it enters into the practice of 
 dyeing. 
 
 According to the observation of De la Folic, roses blanched 
 by the vapour of burning sulphur, become green in an alkaline 
 ley, and red in the acids. Sulphurous acid reddens tincture of 
 litmus, which possesses a very fugitive colour ; but it acts just 
 like the other acids on infusions of yellow wood, brazil wood, 
 and logwood; its vapour, however, is much more active, in 
 which respect it resembles chlorine.* Hence it is not judicious 
 to substitute the use of this for the fumes of sulphur. 
 
 When silk has undergone the action of the sulphur which is 
 to complete its whitening, sulphuric acid disengages from it an 
 odour of sulphurous acid, although this odour was not percepti- 
 ble beforehand. 
 
 From this circumstance we may conclude, that sulphurous 
 acid has the property of combining, in small quantity, with 
 animal substances, without experiencing decomposition ; in 
 which state it can disguise some colours, particularly that arising 
 from a combination of oxygen. But it would seem, that in the 
 lapse of time a more intimate union is effected between the 
 sulphurous gas and the oxygen. 
 
 This latter effect immediately takes place when sulphurous 
 acid is made to counteract the chlorine. The yellowed silk is 
 
 * JoLirn. de phys. 1774. 
 
IN GENERAL. 
 
 87 
 
 whitened by the sulphurous acid ; and the two operations may 
 be alternated. We shall have occasion to speak of the use 
 which Giobert has made of this property. 
 
 We are obliged to confine ourselves to these conjectural 
 views concerning the action which nitric acid, chlorine, and 
 sulphurous acid, exercise on animal substances, till experience 
 shall have conducted us to positive results. 
 
 CHAPTER V. 
 Recapitulation of the Theory laid down in this Section. 
 
 Substances which have constant colours should not be con- 
 founded with those which owe their variable and fugitive hues 
 to the dimensions and density of the plates of which they are 
 formed ; or, at least, the theory of the one cannot serve for the 
 explanation of the properties which the others possess, in refer- 
 ence to the colours which appear to depend on their peculiar 
 affinity for the rays of light. 
 
 Meanwhile, till chemistry can be reconciled with physics, in 
 explaining the phenomena exhibited by colours, we must con- 
 tent ourselves, in reference to the art of dyeing, with determin- 
 ing the affinities which characterize the colouring substances, 
 and the physical dispositions which modify their action in every 
 variety of circumstance. 
 
 Metallic colours must be distinguished from those which be- 
 long to vegetable and animal substances. 
 
 The colours of metals are modified and changed by oxydation, 
 and in proportion to the quantity of oxygen combined with them. 
 
 The vegetable and animal substances, which occasionally owe 
 to plates on their surface some plays of fugitive colours, may 
 themselves have a peculiar colour, or may indeed owe their 
 colours to coloured molecules which exist combined, or simply 
 mixed with them. It is molecules of this kind, extracted from 
 several substances, which receive different preparations, in order 
 to serve for the purposes of dyeing. 
 
 The affinities of the colouring particles for acids, alkalies 
 
88 
 
 BERTIIOLLET ON DYEING 
 
 earths, metallic oxydes, and wool, silk, cotton, and flax, consti- 
 tute their chief distinctive properties; but these are modified 
 by their physical qualities, and especially by their tendency to 
 assume the solid, or to continue in the liquid state. 
 
 In consequence of the aflinity between the colouring parti- 
 cles, and wool, silk, cotton, and flax, they combine more or less 
 easily, more or less intimately, with each of these substances : 
 from which arises a primary difference in the processes em- 
 ployed, according to the nature of the stuff" and of the colour- 
 ing substance. 
 
 Sometimes they umte immediately with the stuffs, but more 
 frequently they require a mordant, in order to be separated 
 from the solvent, and to be fixed on the stuff*, or at least to 
 acquire a greater permanence. 
 
 f lom the affinity of the colouring particles for alumina and 
 metallic oxydes, they form compounds with these substances, in 
 which their colour is more or less preserved, while it becomes 
 more stable, and more insensible to external agents. This 
 combination being formed of principles which possess the 
 faculty of uniting to vegetable, and particularly to animal sub- 
 stances, has also itself this property ; it enters into triple com- 
 binations with the stuflP, and the colour resulting from this 
 triple union thus acquires greater fixity, or the faculty of better 
 resisting external agents. 
 
 The colouring particles have frequently such an aflinity for 
 alumina and the metallic oxydes, that they separate them from 
 the acids which held them in solution, and fall down with these 
 bases; but sometimes the aflinity of the stuff* must determine 
 this combination. We have to distinguish between the che- 
 mical action of the substances which dissolve the colouring 
 particles, and those which fix them, or eflfect their destruction. 
 
 Colours experience great changes from the action of oxygen, 
 which eventually destroys them ; the other substances promote 
 or obstruct this action. 
 
 Of the two principles which compose the atmospheric air, it 
 is only the oxygen gas which acts on the colouring particles. 
 It combines with them, and thus impairs their colour or makes 
 them pale. But its action is soon chiefly exerted on the hy- 
 drogen, which enters into their composition, and it thereby 
 forms water. This effect may be compared to that of a feeble 
 
IN GENERAL, 
 
 89 
 
 combustion. Hence, the carbon which enters into the composi- 
 tion of the colouring particles becomes predominant, and the 
 colour usually passes to yellow, dun, or brown ; or this degra- 
 dation, blended with what remains of the first colour, or with 
 the efl^ect at the same time suffered by a metallic oxyde, pro- 
 duces other appearances. 
 
 Light promotes this decomposition of the colouring particles, 
 which frequently takes place only with its concurrence ; and 
 thus it contributes to the destruction of colours. Heat favours 
 it also, but less efficaciously than light, unless it have a certain 
 intensity.* 
 
 The oxygen present in the colouring particles may itself 
 undergo a combination productive of a slow alteration in the 
 colouring particles, especially by the action of light and heat. 
 
 The oxygen which is absorbed does not, however, always and 
 immediately produce that kind of combustion which alters and 
 destroys the colouring particles ; on the contrary, a certain 
 absorption is usually necessary to give the colours lustre, or 
 even to bring them out, while a larger proportion causes the 
 colour to disappear ; and it is but secondarily that the com- 
 bination of hydrogen is formed, which produces the appearances 
 of a slight combustion. 
 
 The colours are more or less durable, more or less fixed in 
 the air, according to the greater or less tendency which the 
 colouring particles have to experience that change, and to suffer 
 it in a greater or less degree ; for the resistance to this decom- 
 position increases as it advances. 
 
 The other substances exercise their action on the colouring 
 particles, either before they have been applied to the stuffs, or 
 after they have been fixed on them ; they thus have a different 
 use, or they may produce destructive effects. 
 
 The substances capable of dissolving the colouring particles, 
 serve to separate them from the particles with which they are 
 confounded ; and they prepare them, by the liquidity they com- 
 municate, for the action of the stuff*s that are to fix them, or for 
 the combinations they are to form. 
 
 The colouring particles are sometimes modified as to their 
 colours by the action of these substances, and as they usually 
 
 * Statique chimique, torn. i. p. 197. 
 
90 
 
 BERTHOLLET ON DYEING 
 
 retain a portion of them in the combinations which they after- 
 wards form ; or as, when the compound is formed, this may 
 take a portion of them by sur-composition, we call these sub- 
 stances alterants, in order to contrast their effect with that of 
 mordants. 
 
 We give the name of mordants to substances which, combining 
 with the colouring matters, serve to precipitate, to fix, and to 
 render them more durable. 
 
 These two genera of substances, therefore, which exercise the 
 same chemical action, are distinguishable by this ; — the alter- 
 ants, in consequence of their physical qualities, attenuate and 
 dissolve the colouring matters, so that only a small portion can 
 remain in combination when the colouring substances assume 
 the solid state ; such are the acids and alkalies properly called, 
 which, when they act with a certain energy, even deprive the 
 stuffs of those colouring particles which were fixed on them. 
 The power of resisting the action of them and of the air, con- 
 stitutes the permanency of colours. 
 
 The substances, on the contrary, which naturally tend to the 
 solid state, communicate this property to the colouring substances 
 with which they have an affinity, serving as intermedia between 
 them and the stuffs, with which also they must have a tendency 
 to combine. 
 
 The mordants produce this effect only sometimes, and change 
 but slightly the natural colour of a substance ; alumina, in 
 particular, has this property. Sometimes the colour of the 
 combination results from that of the tinctorial substance, joined 
 to that of the mordant; such are the metallic oxydes, which, 
 moreover, alter or ameliorate the natural colour by the action 
 of their oxygen. Thence arise their different effects. 
 
 1. The metallic oxydes, to which the oxygen adheres loosely, 
 are not fit to serve as intermedia to the colouring particles, 
 because they produce in them too considerable an oxydation. 
 The oxydes of silver, gold, and mercury, are in this predicament. 
 
 2. The oxydes which, on giving up more or less of their 
 oxygen, experience considerable changes in their colour, are 
 also bad intermedia, especially for light shades, because they 
 produce variable colours. Such are the oxydes of copper, lead, 
 and bismuth. 
 
 3. The oxydes which retain their oxygen with force, and 
 
IN GENERAL. 
 
 91 
 
 which change their colour very little when they have lost a 
 portion of it, are the most proper for accomplishing this object. 
 The oxyde of tin must be here particularly distinguished. It 
 easily abandons its solvent; it has a strong alSnity for the 
 colouring particles, and affords them a' very white base, one 
 capable of giving brilliancy to their hues, without altering them 
 by the mixture of another colour. The oxyde of zinc possesses 
 these properties in part. 
 
 In order to account for the colours that result from the com- 
 bination of the colouring particles with the basis which a mor- 
 dant gives them, we must also pay attention to the proportion 
 in which the colouring particles are united with this basis. Thus, 
 the solution of tin, which forms a very abundant precipitate 
 with a solution of the colouring particles, proving thereby that 
 the oxyde of tin enters in large proportion into the precipitate, 
 influences the colour of the precipitate, by the colour of the 
 base, much more than the solution of (sulphate of) zinc and of 
 alum does, which bodies usually form a much less considerable 
 precipitate. The precipitates produced by the two latter sub- 
 stances retain very nearly the natural colour of the colouring 
 particles. 
 
 In the action of mordants, therefore, we must distinguish the 
 combinations formed, by their means, between the colouring 
 particles and the intermedium which they furnish to the stuff; 
 the proportions of the colouring substance and the intermedium ; 
 the modifications of colour resulting from the association of the 
 colour of the colouring particles with the base to which they 
 are united ; and finally, the changes which the colouring par- 
 tides may suffer by the action exerted on them by that base. 
 
 Astringents do not differ essentially from colouring particles ; 
 but the latter take this name, especially when employed to 
 produce black with oxyde of iron, by restoring this metal to the 
 state of a black oxyde, and by their assuming a dark colour 
 from the action of oxygen. 
 
 The notion of an astringent supposes, moreover, the property 
 of combining in a certain quantity with animal substances, giving 
 them thus solidity and incorruptibility ; because these two pro- 
 perties are most commonly united. These again are derived 
 from their large sha^e of carbon, a circumstance in their com- 
 
92 
 
 BERTHOLLET ON DYEING. 
 
 position which gives them increased tendency to solidity, and 
 greater stability. 
 
 The natural properties of vegetable and animal substances 
 must depend on those of their elements, and consequently on 
 the proportions of these. These elements are principally oxygen, 
 hydrogen, azote, and carbon. The first three, naturally very 
 elastic, enter into solid combinations only by means of a force 
 that subdues their elasticity. This again produces more or 
 less effect, according to the temperature or the circumstances 
 which may cause the repressing (condensing) force to vary. The 
 carbon, on the other hand, must have a great disposition to 
 assume the solid state, and to maintain its constitution. 
 
SECTION IL 
 
 OF THE DIFFERENCES WHICH DISTINGUISH WOOL, SILK, COTTON, 
 AND LINEN (fLAx), AND OF THE OPERATIONS BY WHICH 
 THESE SUBSTANCES ARE DISPOSED TO RECEIVE DYES. 
 
 CHAPTER I. 
 
 Considerations on the differences between Animul and Vegetable 
 
 Substances, 
 
 We must not flatter ourselves that we can account for the differ- 
 ent results of organization. The knowledge which we have 
 acquired, however, of the composition of animal and vegetable 
 substances, may, agreeably to the preceding considerations, 
 give us some idea of the cause of the different tendencies which 
 wool, silk, cotton, and flax have to unite with the colouring 
 particles, and with the bases which constitute their mordants. 
 
 Wool and silk belong to animal substances ; cotton, flax, and 
 hemp, to vegetable. 
 
 The principal distinction between the composition of animal 
 and vegetable substances is, that animal substances contain the 
 peculiar principle, azote, in abundance, which, in the elastic 
 state, forms what was formerly called phlogisticated air, or 
 phlogisticated gas, and which exists in only a very small quan- 
 tity in vegetable substances. 2. Animal substances contain 
 much more hydrogen, or the basis of inflammable air.* 
 
 * Modern researches do not justify this position of M. Berthollet. Sugar and starch, 
 by the analyses of MM. Gay Lussac and Berzelius, contain about as much hydrogen as 
 fibrin does, and very little less than gelatin and albumen ; while, by my analyses, wool and 
 silk contain less hydrogen than cotton and flax, — See Phil. Trans, for 1822. 
 
 I subjoin the results of my analytical experiments on the four principal subjects of 
 dyeing. 
 
 
 Carbon. 
 
 Hydrogen. 
 
 Oxygen. 
 
 Azote. 
 
 Wool . 
 
 . 53.70 
 
 2.80 
 
 31.20 
 
 12.30 
 
 Silk 
 
 50.69 
 
 3.94 
 
 34.04 
 
 11.33 
 
 Cotton . 
 
 42.11 
 
 5.06 
 
 52.83 
 
 
 Flax . 
 
 . 42.81 
 
 5.50 
 
 51.70 
 
 
 The first two, independently of the azote, possess a marked difference of composition, 
 from their excess of carbon and deficiency of oxygen. — T. 
 
94 
 
 BERTHOLLET ON DYEING. 
 
 From these two causes, the differences observed in the distil- 
 lation of animal and vegetable substances arise. The former 
 produce much ammonia, v^hich is a compound of azote and hy- 
 drogen; the latter yield very little, and they afford usually 
 even a good deal of acid, the characteristic properties of which 
 flow from oxygen. From the former much oil is obtained, whose 
 predominant principle being hydrogen, it has a great tendency 
 to volatilize, and to separate at a slightly elevated temperature. 
 The latter often afford no perceptible quantity of it. The 
 former can produce prussic acid, which is a combination of azote, 
 hydrogen, and carbon ; and vegetables possess this property 
 only in so far as they contain azote. In consequence of this com- 
 position, animal substances yield, on being burned, a lively 
 flame, which bursts forth at the commencement ; but this 
 flame is, so to speak, speedily quenched by the charcoal that 
 is evolved, which has peculiar characters. Their combus- 
 tion is accompanied with a penetrating odour, arising from 
 the ammonia and oil formed, which escape inflammation. 
 They are subject to putrefaction, during which ammonia is pro- 
 duced, as it is in distillation, by the more intimate union of the 
 azote and the hydrogen ; whereas vegetable substances undergo 
 a spirituous or acid fermentation. We merely indicate in this 
 place ideas which have been developed in particular memoirs. 
 
 As animal substances contain a great deal of those principles 
 which tend to assume the elastic state, they have less cohesion 
 in their molecules than vegetables, and less stability in their 
 composition. We may observe, that when they acquire solidity, 
 they owe it most frequently to the mixture, or rather combina- 
 tion, of a foreign substance, such as the phosphate or carbonate 
 of lime in the bones. 
 
 Hence, they are more subject to be destroyed by different 
 agents, and more disposed to enter into combination with the 
 colouring particles. 
 
 Thus, fixed alkalies, when pure or caustic, destroy animal 
 substances, because they combine with them to saturation, and 
 thereby lose their causticity.* 
 
 From this action of alkalies on animal substances, it follows, 
 that these substances cannot resist leys, and that alkalies must 
 be had recourse to with much caution in the processes wherein 
 
 * Mcni. de racatlcmie, 1783. 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 
 
 95 
 
 such todies are dyed ; whereas the moderate use of alkalies is 
 not to be dreaded with regard to vegetable substances. 
 
 Nitric and sulphuric acids have also considerable action on ani- 
 mal substances. The former decomposes them, with the disen- 
 gagement of azote, the separation of fat or adipocere, and the 
 formation of carbonic and oxalic acids from a portion of the 
 hydrogen and the carbon. The latter acid disengages from 
 them inflammable gas, and probably azotic gas, while it reduces 
 the other principles into the carbonaceous state. 
 
 Silk appears to approach a little towards vegetable substances, 
 from its inferior disposition to combine with the colouring par- 
 ticles, and from its greater resistance to the action of alkalies and 
 acids. This may arise either from the same principles being here 
 more intimately combined than they are in wool, or more pro- 
 bably from the presence in it of less azote and less hydrogen.* 
 But although the alkalies and the acids exert a less lively action 
 on silk than on wool, we must nevertheless use them with much 
 precaution, because the brilliancy of colour sought for in silk 
 appears to depend on the polish of its surface, which we must 
 beware of injuring. 
 
 Cotton resists the action of acids better than flax and hemp ; 
 and it is with difficulty destroyed even by the nitric acid. 
 
 CHAPTER II- 
 Of Wool. 
 
 In the cloth manufactures wool is destined to different pur- 
 poses according to the length and fineness of its filaments ; but 
 there is a wide distance between the production of fine wooled 
 sheep and ordinary wool. Hence no little gratitude is due to 
 d'Aubenton for fixing public attention on this important object 
 of agricultural economy, and to those individuals who have since 
 prosecuted, with so much steadiness and success, the project of 
 renovating our degenerate breeds by means of Merinos. 
 
 Wool is naturally coated with a species of fat, called grease. 
 
 * The organic structure, and state of condensation in animal and vegetable fibres, should 
 be studied along with their chemical composition, in order to learn their dyeing relations. T. 
 
96 
 
 BERTHOLLET ON DYEING. 
 
 This coating preserves it from the moths.* Hence it is not 
 scoured till it is going to be spun or dyed. 
 
 In order to scour wool, it is put for about a quarter of an 
 hour into a boiler which contains a sufficient quantity of water, 
 mingled with one fourth of putrefied urine. The whole is then 
 heated as high as the hand can endure it, and it is stirred about 
 from time to time with rods. It is now washed, and set to 
 drain. The wool is removed thence into a large basket, placed 
 in running water where it is stirred, till the grease having en- 
 tirely left it, the water ceases to be milky. It is then taken to 
 be drained. In this operation it loses sometimes more than a 
 fourth of its weight. It is of great consequence that the scour- 
 ing be carefully performed, because the wool is thus alone pre- 
 pared for receiving the dye. 
 
 The residuum of the first operation is preserved in a tub, 
 to which, from time to time, some putrefied urine is added, so 
 that the grease present in it may serve to render more soluble 
 any thing adhering to the new wool. The ammonia of the 
 putrefied urine contributes probably to this eflfect. When wool 
 resists this operation, a little soap is added to the liquor ; but it 
 is only with much precaution that the use of soap is permitted 
 on fine wools, because it is apt to injure them. 
 
 Vauquelinf made experiments on the nature of the grease, 
 from which it appears to be formed, 1, of a soap, with basis of 
 potash, which forms its chief part ; 2, of a small quantity of 
 carbonate of potash; 3, of a notable quantity of acetate of potash; 
 
 4, of lime, whose state of combination he could not determine ; 
 
 5, of a small quantity of muriate of potash ; lastly, of an animal 
 matter, to which he ascribes the peculiar odour of the grease. 
 
 He regards the ammonia contained in the putrefied urine as 
 not being conducive to its action, and he even advises the use of 
 ordinary soap as better fitted to procure the desired whiteness to 
 wools ; but experience leads to results incompatible with the 
 opinion of this skilful chemist. 
 
 Wool is dyed in the fleece, or without being spun, principally 
 when it is to be employed for forming cloths of mixed colours ; or 
 otherwise it is dyed after being spun. It is then intended chiefly 
 for carpets, but it is most commonly dyed in the form of cloth. 
 
 * Reaumur remaiked, that it was sufficient to rub a stuff with greasy wool to preserve 
 it from moths. — Mm. de Vacademie^ 1728. 
 j Ann. dc chiaiie, torn, xlvdi. 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 
 
 97 
 
 When wool is djed in the fleece, its unconnected filaments 
 absorb a greater quantity of the colouring particles than when it 
 is spun ; for a like reason, woollen yarn consumes more colour 
 than woollen cloth. Cloths, however, exhibit much variety 
 among them, according to their degree of fineness, and the 
 closeness of their texture : besides, the difference of their 
 dimensions, the variable qualities of the dyeing ingredients 
 made use of, and the different circumstances of the operations, 
 teach us not to confide in the precise doses enjoined in the pro- 
 cesses usually described. This observation may be extended to 
 all dyes. 
 
 For the generality of dyes, wool requires to be prepared with 
 a bath, in which it is boiled along with saline substances, prin- 
 cipally alum and tartar. This is called the bouillon, which we 
 shall take care to describe under the different processes. But 
 there are dyes for which wool needs none of these prepara- 
 tions. It must, however, be well softened in tepid water, and 
 thereafter squeezed, or set to drain. This is a precaution 
 which must in general be taken with all substances which we 
 wish to dye, that the colour may more easily be introduced into 
 them, and more equally distributed. Wool, in particular, re- 
 quires heat to enable it to absorb the colouring particles ; a 
 circumstance which appears to depend on the disposition of 
 its filaments to form a dense texture. 
 
 Monge has explained the mechanism of felting, and the 
 effects of fulling, by the external conformation of wool, and 
 the hairs of animals. He has made interesting observations on 
 this subject, of which I shall relate the principal.* 
 
 Nothing peculiar can be discovered on the outside of the 
 fibres of wool and the hairs of animals by means of the mi- 
 croscope ; yet " the surfaces of these objects are not smooth ; 
 they must be formed either of plates, which cover each other 
 from the root to the point, nearly as the scales of fish overlap 
 each other from the head of the animal towards its tail ; or 
 rather perhaps of superposed zones, as is observed in horns. 
 
 If we seize a hair by the root with one hand, and draw it 
 through the two fingers of the other, from the root towards the 
 point, we experience scarcely any friction, or any resistance, 
 nor do we perceive any noise ; but if, on pinching it by the 
 
 * Observations sur le m^canisme dii feutrage. — Ann, de chimie, torn. vi. 
 
 H 
 
98 
 
 BERTHOLLET ON DYEING. 
 
 point, we make it slide equally between the fingers of tlie 
 other hand, from the point towards the root, we experience 
 a resistance which does not exist in the first case, and a tre- 
 mulousness perceptible to the touch is produced, which is also 
 manifested by an audible sound. 
 
 " We thus perceive that the contexture of the surface of the 
 hair is not the same from the root towards the point, as from 
 the point towards the root, and that a hair, when pressed, 
 ought to experience more resistance in sliding and taking a 
 progressive movement towards the point, than in sliding towards 
 the root; but as this very contexture forms the principal object 
 of this memoir, it is necessary still farther to confirm it by some 
 other observations. 
 
 " If, after seizing a hair between the thumb and the fore- 
 finger, we make the two fingers slide alternately one over the 
 other in the direction of the length of the hair, the hair takes a 
 progressive movement in the direction of its length, and this 
 movement is always towards the root. This effect does not 
 depend either on the nature of the skin of the fingers or on its 
 contexture, for if we turn back the hair, so that its point is 
 placed where its root was, the movement takes place recipro- 
 cally in the contrary direction ; that is to say, it is turned 
 always towards the root. 
 
 These observations, to which Monge adds some others, are 
 all referred to the hair of his head taken as an example ; but 
 they equally hold true of horse hair, fibres of wool, and in ge- 
 neral of the hairs of all animals. The surface of all these ob- 
 jects, therefore, is formed of rigid plates, superposed or tiled 
 from the root to the point, permitting the progressive movement 
 towards the root, and resisting a similar movement towards the 
 point. 
 
 This conformation is the main cause of the tendency to 
 felting, which the hairs of all animals in general possess. 
 
 The hatter, in fact, on striking with the cord of his bow the 
 flocks of wool, detaches and disperses in the air each of the 
 particular fibres ; these fibres fall down over one another in all 
 directions on the table, where they form a layer of a certain 
 thickness. The workman then covers them up with a cloth, 
 which he presses with his outstretched hands, working them 
 about in different directions. The pressure approximates towards 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 
 
 99 
 
 each other the woollen fibres, and multiplies their points of 
 contact ; the agitation gives each of them a progressive move- 
 ment towards the root. By means of this movement the hairs 
 interlace, and the lamellce of each hair, by hooking into those 
 of other hairs which lie in an opposite direction, maintain the 
 whole in the compact texture which the pressure first gave. 
 In proportion as the tissue is compacted, the pressure of the 
 hands ought to increase, both for the further condensation, 
 and for promoting the progressive movement of the hairs, as 
 well as their interlacement, which now meets v^ith greater 
 difficulty. But in all this operation the fibres of wool grapple 
 only with one another, and not with the cloth, whose fibres, 
 as we have already said, are smooth, and do not present the 
 same facility in this respect. 
 
 The conformation at the surface, of the fibres of wool and 
 the hairs of animals, does not constitute their sole disposition 
 to felting. It is not enough that every fibre shall take a pro- 
 gressive movement towards the root ; it is not enough that the 
 incHned lamellce^ on grappling with one another, shall maintain 
 the texture in the state into which the compression has put it ; 
 — it is further requisite, that the fibres shall not be straight 
 like needles; in consequence of the agitation, each of them 
 would continue its progressive movement without changing its 
 direction, and the effect of the operation would be, to remove 
 them all from the centre without producing any tissue. It is 
 necessary, therefore, that each fibre should be twisted, that the 
 extremity which is on the side next the root be disposed con- 
 tinually to change its direction, to interlace itself around new 
 fibres, and to turn back on the fibre itself, if so determined 
 by some change in the position of the rest of its length. Wool 
 being naturally constructed in this manner, is peculiarly well 
 adapted for felting, and may be so employed without being 
 subjected to any previous operation. 
 
 But the furs of the rabbit, the hare, and the beaver, are 
 naturally straight ; they cannot be employed alone for felting, 
 without having undergone a preliminary operation, which is 
 called secret age ; and which consists in rubbing them, before 
 they are stripped off*, with a brush moistened with a solution 
 of mercury in nitric acid. This solution, by acting on only 
 one side of the substance of the hairs, alters their right-lined 
 
 H 2 
 
100 
 
 BERTHOLLET ON DYEING. 
 
 direction, and communicates tlie disposition for felting which 
 wool naturally possesses. 
 
 The operation of fulling woollen stuiFs, has so close a rela- 
 tion with felting, that we cannot dispense with entering into 
 some details on this subject. 
 
 The roughness with which the fibres of wool are bristled at 
 their surface, and the disposition which the fibres have to take a 
 progressive movement in the direction of the root, is an obstacle 
 to the spinning of wool and to the fabrication of stuffs. In 
 order to spin the wool, and afterwards weave it, we are obliged 
 to coat all the fibres with a film of oil, which, by filling up the 
 cavities, renders the asperities less perceptible ; just as a film of 
 oil is put upon a smooth file, when we wish to render it still 
 smoother. When the piece of stuff* is manufactured, it must 
 be deprived of this oil, which gives it a disagreeable colour, 
 and constitutes a kind of filthiness, which would be an obstacle 
 to dyeing. For this purpose, it is carried to the fulling-mill, 
 where it is beat with mallets in a trough filled with water 
 through which clay (fuller's earth) has been diff'used. The clay 
 combines with the oil, which it renders soluble in water; both 
 are carried off* by the fresh water which the m.achine itself brings 
 upon it ; and at the end of a certain time the stuff* is scoured. 
 
 But scouring is not the only object of the fulling. The 
 alternate compressions which the beetles exert on the piece of 
 stuff*, especially when the scouring is well advanced, produce 
 an eff*ect analogous to that of the hand-pressure of the hatter. 
 The fibres of wool which compose one of the threads of the 
 woof or of the warp, take a progressive movement, get intro- 
 duced into one of the neighbouring threads, then into those 
 which follow, and soon all the threads both of the woof and 
 warp are felted together. The stufl^*, after having suff'ered a 
 narrowing in its two dimensions, partakes of the nature both of 
 web and felt ; it may be cut without being liable to open out 
 its threads, and there is no necessity for hemming the diff*erent 
 pieces which enter into the composition of a garment. If it be 
 ordinary knit wool, the stitch is no longer apt to run when it 
 happens to escape. Lastly, 'the threads of the woof and the 
 warp being no longer so well defined, or so distinct from each 
 other, the stuff*, which in other respects is thickened, forms a 
 warmer clothing." 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 
 
 101 
 
 CHAPTER HI. 
 Of Silk. 
 
 Silk is naturally coated with a substance, which has been re- 
 garded as a guin, to which it owes ks stiffness and elasticity. 
 The silk most common in our climates, contains besides a yellow 
 colouring matter. 
 
 The greater part of the uses to which silk is destined, require 
 it to be not only deprived of its colouring matter, but also of 
 the gum. This twofold object is accomplished by means of soap. 
 The name of decreusage (scouring) is given to the operation by 
 which silk acquires its pliancy and whiteness. 
 
 The scouring must not be so complete for the silks which are 
 to be dyed as for those intended to remain white ; and it should 
 even differ according to the colours proposed to be given. This 
 difference chiefly consists in the proportion of soap that is em- 
 ployed. Thus, for ordinary colours, we content ourselves with 
 boiling the silk for three or four hours in a solution containing 
 20 parts of soap for every 100 parts of silk, taking care to fill 
 up the boiler from time to time with water, in order to have 
 always a sufficiently large bath. The quantity of soap is in- 
 creased for silks which are to be dyed blue, and more especially 
 for those which are to be dyedj?072C^az^ (flesh-red), cherry colour, 
 &c. ; because these colours require a whiter ground than the 
 less delicate ones. In treating of each colour, the proportions 
 of soap suitable for the silk are indicated. 
 
 When silk is to be used white, it is made to undergo three 
 operations. The first is Ccilled degommaye (ungumming). It 
 consists in keeping its hanks in a solution of 30 parts, of soap 
 for 100 of silk. This solution must be very hot, but not in 
 ebullition. When the dipped portion of the hanks i& entirely 
 ungummed, which is known by the silk assuming Vvhiteness and 
 flexibility, the hanks are turned about (shaken over) on the rods 
 in order to subject the portion which had not been plunged to 
 the same operation ; and they are then withdrawn from the bath, 
 and fastened on pegs, in proportion as the ungumming is finished. 
 
 The second operation is the boil. The silks are enclosed in 
 
102 
 
 BERTHOLLET ON DYEING. 
 
 bags of coarse cloth, 26 to 33 pounds of silk being put in each 
 bag, called a poche (pocket). A soap-bath similar to the former 
 is prepared, with a smaller proportion of soap ; and they are 
 boiled for an hour and a half, taking care to stir about the bags, 
 so that those which touch the bottom may not experience too 
 great a heat. 
 
 The third operation is called whitening. This operation is 
 intended principally to give the silk a slight shade, which may 
 render the white more agreeable. Different names are given to 
 the white, according to the shade. Thus we have china-white, 
 silver-white, azure-white, thread-white. A solution of soap is 
 made, such that, on beating it, a froth is obtained from which we 
 may judge if it be of a proper strength. For the china-white, 
 which should have a somewhat red cast, a little anotto is added. 
 The silk is then left in it till it takes the desired shade. To the 
 other whites more or less of a blue cast is given by means of azure, 
 which is added to the solution of the soap, though some of it 
 has already been put into the boil. 
 
 To prepare the azure, some fine indigo is washed two or three 
 times in water moderately hot, when it is well ground in a mor- 
 tar, and boiling water is thrown over it. It is allowed to settle, 
 and the liquid is used, which retains only the most subtile parts. 
 This is called azure ; for which may be substituted a little of 
 the liquor of a fresh vat of indigo. 
 
 At Lyons, where a more perfect white is given than at Paris, 
 no soap is employed for the third operation ; but after the 
 second, the silks are washed, sulphured, and passed through 
 azure diffused in river water. In this method, it is of importance 
 to employ a very limpid water. — When the silks have become 
 very uniform, and have taken the wished-for shade, they are 
 wrung out and dried. 
 
 The white obtained by the method now pointed out, is not 
 brilliant enough for silks intended for white stuffs. They must 
 still be exposed to the fumes of sulphur. This operation will 
 be described in the article on sulphur. 
 
 Since soap appears to injure the lustre of silk, the Academy 
 of Lyons proposed, in 1761, as the subject of a prize, to find a 
 method of scouring silks without soap ; and this prize was ad- 
 judged to Rigaut de St. Quentin, who proposed to substitute for 
 soap a solution of salt of soda, or carbonate of soda, dissolved in 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 103 
 
 a quantity of water large enough not to affect the silk. But in- 
 conveniences must have been found in the employment of this 
 method, which was probably too active, since no use is made of 
 it, although it is known, and may be easily practised. 
 
 Collomb* published some observations on the bleaching of 
 silk by the action of water alone, which merit much attention. 
 Having perceived that a hank of yellow silk, which he had 
 boiled about three hoiirs in common water, had lost nearly an 
 eighth of its weight, he repeated the ebullition twice, and car- 
 ried by this means the diminution of weight to a fourth. 
 
 The silk which suffered this loss of weight, preserves, how- 
 ever, a yellow, or rather a chamois colour, which renders it unfit 
 for making stuffs intended to remain white, or to receive some 
 colours whose beauty depends on the whiteness of the ground 
 to which they are applied ; but it answers very well for colours 
 which that tinge cannot injure. Thus the black dye which it took 
 appeared preferable to that of silk bleached with soap. 
 
 After this operation, the silk remains very strong and tough, 
 and threads of it supported weights which broke threads bleached 
 with soap. 
 
 Eight hours of brisk ebullition are required for dissolving 
 away the whole varnish of silk, in which it loses a little more 
 than one fourth of its weight ; but the ebullition ought to last 
 longer when the barometer is low, because the greater the weight 
 of the atmosphere, the higher is the degree of heat which 
 boiling v^ater takes. 
 
 This consideration led CoUomb to try the boiling of silk in a 
 Papin's digester ; and in fact, it required only an hour and a 
 quarter to effect the complete solution of the varnish, although 
 the degree of heat was inferior to what produced some of the 
 phenomena observed by philosophers in this concentrated ebul- 
 lition. 
 
 The substance which the water dissolved, when evaporated, 
 was black, brittle, and brilliant in its fracture. On distillation, it 
 afforded the usual products of animal matter. It dissolved 
 readily in hot water, leaving very little on the filter. The solu- 
 tion, which was clear, and of a greenish yellow colour, was not 
 sensibly affected by acids or alkalies. 
 
 The solution of alum produced in it a precipitate of a dirty- 
 
 * Observations sur la dissolution dii vcrnis dc la soie. — Journ. de phys., Aout^ 1785. 
 
104 
 
 beiithollj:t on dyeing. 
 
 white colour; that of sulphate of copper, a black-brown precipi- 
 tate ; that of sulphate of iron, a brown precipitate ; the nitro- 
 muriatic solution of tin, a white precipitate ; the acetate of lead, 
 a brown precipitate. 
 
 All these precipitates are scanty, and more or less viscid. In- 
 fusion of nut-galls, and of sumach, occasioned a white precipi- 
 tate. 
 
 Alcohol does not dissolve this substance even by ebullition, 
 but only a yellow colouring portion. This solution left, on 
 evaporation, a scaly residuum of an amber-yellow. On boiling 
 15 grains of this substance in 1500 grains of alcohol, containing 
 some drops of muriatic acid, its solution was effected, but, on 
 cooling, this substance took the form of jelly. 
 
 The substance taken from silk in the scouring, is therefore of 
 an animal nature ; whence the soap-water which has served for 
 the scouring speedily putrefies. When this substance is no 
 longer retained by its affinity for silk, it becomes soluble in 
 water, but not in alcohol. Although it is not of a vegetable 
 nature, the term gum seems sufficiently proper. The yeJlow 
 colouring matter dissolves in alcohol. When this part is sepa- 
 rated, the gum becomes brown. It v/ould seem that this colour 
 is caused by the heat of ebullition, since, when the yellow 
 colouring portion only is removed by the process of Baume, of 
 which we shall presently speak, the silk remains white. 
 
 In the process of Collomb, the gum is removed, carrying with 
 it only a portion of the yellov/ colouring particles ; while, in 
 scouring with soap, the gum, and yellow colouring parts, are 
 both carried off from the silk. 
 
 When silk is intended for the manufacture of blonds, laces, 
 and gauzes, it should have its natural stiffness and elasticity. 
 The greater part of the silk produced in our climates has a 
 yellow colour. The white silk of China is therefore principally 
 employed for these objects, and a few others. It is not yet 
 positively ascertained v/hether the Chinese silk is naturally 
 vvhite, or rendered so by some unknown process. According to 
 Poivre, this silk is bleached by exposing it to the sun. But 
 some other circumstance is necessary ; for this method has been 
 tried without success. Baume has published a process which 
 he considers as analogous to the Chinese one.* 
 
 * Ann. de chimie, torn, xvii. 
 
DIFFERENCES BETV/EEN WOOL, SILK, &C. 
 
 105 
 
 This process consists, 1. In infusing the yellow silk, or that 
 which has not naturally a sufficiently pure white, in water 
 heated to 88° Fahr., to destroy the mutual adherence which 
 the threads had contracted in the winding ; 2. In making this 
 silk undergo two successive macerations, longer or shorter ac- 
 cording to the temperature, in a mixture of alcohol containing 
 l-64th of its weight of muriatic acid; 3. In washing the silk 
 with much care immediately after this operation, which, on 
 losing its colouring part, has given up but a portion of its gum ; 
 4. In drying this silk in a state of extension, to prevent it from 
 crisping. The muriatic acid employed ought to be thoroughly 
 free from nitric acid, v/hich gives, as we have seen, a yellow 
 colour to animal substances. For the same reason, such muri- 
 atic acid must be avoided as has been rendered yellow by 
 chlorine. Hermstadt affirms, that he repeated this operation 
 with success. 
 
 A skilful chemist, Giobert, makes objections to this process, 
 for which he substitutes a new one. We shall remark, mean- 
 while, tha.t in his experiments he employed l-48th of muriatic 
 acid, while Baume prescribed only l-64th. We shall here 
 present the extract which has been given of his work.^ 
 
 " The preparation of the acid pointed out by Baume is very 
 embarrassing. The green colour which the liquid assumes, the 
 species of jelly which it forms around each filament, and still 
 more the diminution of weight in the silk, are sufficient to 
 indicate that it would not be correct to view in the action of 
 this liquid only the destruction of the colouring matter. Even 
 in retaining a portion of its rawness f crud J, the silk is far from 
 preserving so much of it as is desired in the arts ; and this 
 process, which involves considerable expense, becomes more 
 costly than is imagined, from the diminution in the weight of 
 the silk. 
 
 Crell and Brugnatelli proposed chlorine. But it is known 
 that silk comports itself in the same way with this acid as 
 animal substances do, that is to say, it becomes yellow. Yet 
 Vv^e shall presentl}^ see that it may be employed. When this 
 substance is used in the form of gas, Giobert found that the 
 silk was soon destroyed by it. 
 
 * Bibliot. ital, torn. i. 
 
106 
 
 BERTHOLLET ON DYEING. 
 
 On employing it in the state of a pretty concentrated 
 solution, the yellow colour becomes weaker, and apparently 
 approaches to white ; but on taking it out of the aqueous 
 chlorine, the silk is of a yellowish colour, and this hue is more 
 durable than its natural one. 
 
 " From this result it appears that chlorine exercises on silk 
 a twofold action ; that is to say, it destroys its colouring matter 
 on the one hand, and on the other, it makes the same impression 
 as on animal substances in general — a change indicated by a 
 yellow tinge. 
 
 ^' This last impression is destroyed by the action of sulphurous 
 acid; and it is in the combined and alternating action of it 
 and chlorine that the author has attempted a new mode of 
 bleaching. 
 
 In the preceding experiments, and in- all those where 
 aqueous chlorine, however little concentrated, was employed, 
 Giobert observed that the silk was considerably weakened. 
 Very frequently, after being well washed, the filaments broke 
 in the wringing, 
 
 " The same liquor diluted to a great degree no longer pro- 
 duced this effect, yet it exerted a well marked action on the 
 colouring matter of the silk. On coming out of it, the silk 
 retains a portion of its natural colour, and being a little oxygen- 
 ated by the agency of the chlorine, it exhibits its effects and 
 appearances. 
 
 " On passing it then into liquid sulphurous acid, also very 
 dilute, the yellow tint is destroyed. 
 
 Giobert has succeeded in whitening the silk completely 
 and preserving its raw feel, by passing it alternately through 
 these two liquids for ten or twelve times, finishing the operation 
 with the sulphurous acid. 
 
 It is of the greatest importance to multiply the immersions, 
 and not to employ strong gaseous impregnations, by which the 
 silk would be either destroyed or considerably weakened. 
 
 " Silk bleached by this method is scarcely diminished in 
 weight. It retains its raw feel, its flexibility, and does not 
 appear to get stiff, while the bleaching is uniform in all its 
 parts. 
 
 ^' When it was compared with the silk bleached by the process 
 of Baume, the latter was found to present a more agreeable 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 
 
 107 
 
 gloss, while the former had merely a dead-white. This circum- 
 stance does not appear to Giobert very important, because the 
 chief use of bleached raw silk is in the manufacture of gauzes ; 
 and much gloss is not required in this kind of stuffs. 
 
 The dyers believe that silk which has received the fumes 
 of sulphur is not well adapted to receive colours. Giobert 
 attempted to rectify this principle with raw silk bleached by 
 the process just detailed. This silk took every colour, and 
 particularly the finest black." 
 
 Aluming ought to be considered as one of the general opera- 
 tions of silk dyeing, because without alum the most part of 
 colours applied to silk would possess neither beauty nor per- 
 manence. 
 
 To execute the aluming there is put into a tun or tub from 
 140 to 175 gallons of water, and 44 to 55 pounds of Roman 
 alum, previously dissolved in a kettle-full of sufficiently hot 
 water, stirring carefully during the mixture, to prevent the 
 crystallization of the alum. 
 
 After washing and beetling the silks, and even wringing them 
 on the jack and pin,'*' to extract the soap which they may have 
 retained, they are plunged into the alum bath. Here they are 
 left for eight or nine hours, after which they are twisted by 
 hand over the tun (vat), and taken to the river to be washed. 
 
 We may pass as much as 165 pounds of silk through a bath 
 like the preceding, without being under the necessity of adding 
 fresh alum. But when it is perceived that the bath begins to 
 become weak, which habit teaches by the taste, 22 to 26 pounds 
 of alum are dissolved, which are put into the bath, as at first ; 
 and thus it is continually renewed, till it begins to emit a dis- 
 agreeable smell. It is then thoroughly exhausted by passing 
 the silks through it which are intended for dull colours, such as 
 browns, chesnuts ; after which it is emptied out, and a new 
 alum liquor formed. 
 
 Silks are always alumed in the cold, because, when they are 
 alumed in a hot bath, they are apt to lose a portion of their 
 lustre. 
 
 * The usual frame for wringing hanks of yam, with the aid of a screwed rod. — T. 
 
108 
 
 BERTIIOLLET ON DYEING. 
 
 CHAPTER IV. 
 Of Cotton. 
 
 Cotton is the down or wool (bourre ) contained in the pod 
 of a plant which grows in hot countries. This down is sepa- 
 rated from the seeds which it envelopes by means of a kind of 
 mill. 
 
 Climate has a great influence on the qualities of cotton, and 
 the species of the cotton plant seem to correspond to the degree 
 of heat.* But a great variety are found in the West Tndia 
 islands ; and it appears from what Bennet says^l" that the 
 colonists have hitherto neglected to make a selection of those 
 which would be most advantageous, whence they have lost a 
 great part of the benefits which they might have derived from 
 this valuable production. 
 
 Five species of the cotton shrub have been distinguished, 
 which contain many varieties. Linnaeus has distinguished these 
 five species by the following names : gossypeum arboreum, or 
 the cotton tree of India ; gossypeum religiosum, a great shrub 
 which grows also in India ; gossypeum Barbadense, a biennial 
 shrub cultivated in Barbadoes ; gossypeum Jiirsutum, a shrub 
 v/hich is perennial in the hot climates of America, and annual 
 in the cold ; gossypeum herbaceum, which seems to be originally 
 from Persia, but which is cultivated in the islands of the Archi- 
 pelago, in Egypt, Malta, and Sicily. The Russians cultivate 
 it even in the government of Caucasus. 
 
 To these species may be added the cotton of Siam, rem.ark- 
 able for the fineness and silkiness of its filaments. 
 
 According to Guthrie, there has been cultivated for some 
 time in Germany an asclepias, asclepias syriaca, Linn, which 
 yields a very silky species of cotton.:): Manufactures have been 
 established in Saxony of stufis with this cotton, which rival silk 
 in lustre. 
 
 * Essais sur ks caracteres qui distinguent les cotons des di verses parties du monde, &c. 
 par M. Quatremere Disjonval. 
 
 •f Transactions of the Society instituted at London for the Encouragement of Arts, 
 Manufactures, and Commerce, vol. i. 
 
 J Memoirs of Manchester, vol, v. part 1. 
 
DIFFERENCES BETWEEN WOOL, SILK, 8cC. 
 
 109 
 
 The principal differences of cotton consist in the length of its 
 filaments, their fineness, their solidity, and their colour. In the 
 last point of view, several species are distinguished in com- 
 merce, which differ not only in tlieir absolute value, but also 
 in the uses for which they are intended. 
 
 The colour of cotton varies from deep yellow to white. The 
 highest coloured is that of Siam and Bengal ; with which stuffs 
 are often made that preserve the native hue. 
 
 Cotton has become, by the extent and variety of its uses, 
 one of the principal objects of manufactures and commerce. 
 From its manufacture being conducted with little expense of 
 labour, India has particularly derived much of the treasure 
 constantly poured into it. 
 
 A nation celebrated for its genius in the arts, has succeeded 
 in compensating the difference in the rate of wages by the ex- 
 pedition of machinery, and has thus drawn into its bosom this 
 source of prosperity. It must preserve exclusively the great 
 advantages which it now derives, were other nations not to 
 endeavour to promote, by particular measures of administration, 
 a competition of manufacture capable of supporting a part of 
 their population.* 
 
 To prepare cotton to receive the dye, it is subjected to an 
 operation, called in French decreusage (scouring.) Some per- 
 sons boil it in sour water ; but most frequently an alkaline ley 
 is employed. In this the cotton is boiled for two hours, after 
 
 * Some respectable philosophers, while claiming freedom for commerce and industry, 
 appear to have made too wide an application of their principles of political economy, when 
 they inveigh against those restraints which the vigilance of government puts on the intro- 
 duction of particular products of foreign manufacture. 
 
 When manufactures have acquired a marked superiority by peculiar processes, when 
 long practice has carried these processes to perfection, and when tbe dexterity acquired by 
 their workmen bids defiance to competition, we must for ever renounce them, or these 
 advantages must be balanced by import duties, or even by prohibitions. 
 
 It is said, that we thereby force capital into other directions less natural and advan- 
 tageous. This maxim is true with regard to objects in which manufactures possess natural 
 advantages or disadvantages. 
 
 But when merely temporary disadvantages are to be countervailed, when an object of 
 great consumption is concerned, which may afford employment to a large portion of the 
 population, it is the interest of the consumers themselves to submit to a temporary impost, 
 which may serve as a premium to a new branch of industry, and may even create sufficient 
 capitals to those who undertake it, by affording extraordinary profits up to a certain stage. 
 They are in the predicament of a landed proprietor, who renounces, for some time, a part 
 of his revenue, to establish a canal of irrigation on his estate. 
 
110 
 
 BERTHOLLET ON DYEING. 
 
 which it is wrung out. It is then rinsed in the river till the 
 water runs off clear, when it is dried. 
 
 Cotton cloth intended for printing is immersed for some time 
 in water charged with one-fiftieth at most of sulphuric acid, 
 after which it is washed with care in running water, and dried. 
 The acid used in this operation dissolves the calcareous earth, 
 and the oxyde of iron, which might have injured the colours. 
 
 The aluming is given in the proportion of a quarter of alum 
 for one part of cotton. The alum is dissolved with the precau- 
 tions pointed out in the preceding article, but a solution of soda 
 is added to it, which may be estimated at about one part of soda 
 for sixteen of alum. Some persons introduce a very small quan- 
 tity of tartar and arsenic. . The yarn is well impregnated with 
 this solution, by working it in small portions ; after which the 
 remainder of the bath is poured upon the whole yarn collected 
 in a vessel. It is left there for twenty-four hours. On coming 
 out of the aluming, it is set to purge itself in running water for 
 an hour and a half or two hours, and it is then washed. Cotton 
 absorbs about one-fortieth of its weight in this operation. 
 
 The galling is made with different proportions of gall-nuts or 
 other astringents, according to the quality of the astringent, 
 and the effect wished to be obtained. 
 
 The gall-nuts, bruised, are to be boiled about two hours in a 
 quantity of water, which ought to be proportioned to the quan- 
 tity of yarn to be galled. The bath is then allowed to cool, so 
 that the hand may bear dipping in it. It is divided into por- 
 tions, which are made as equal as possible, in order to operate 
 with small parcels, as is mentioned under aluming; and the 
 remaining liquor is in like manner thrown over the whole. 
 Here it is left for twenty-four hours, especially when it is in- 
 tended for maddering and for black ; with regard to other 
 colours, from twelve to fifteen hours may suffice ; after which it 
 is wrung out and dried. 
 
 When the galling is given to stuff's that have already received a 
 colour, it must be done in the cold, in order not to alter this colour. 
 
 Alumed cotton takes a greater increase of weight in the 
 galling than what is not alumed ; for although alumina fixes in 
 only small quantity on cotton, it communicates to it the pro- 
 perty of combining much better with the astringent principle, 
 as also with the colouring particles. 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 
 
 Ill 
 
 CHAPTER V. 
 
 Of Flax and Hemp. 
 
 Since flax and hemp present the same properties, in refer- 
 ence to dyeing, they are usually confounded together in this 
 work. 
 
 If cotton be an important object to our industry, flax and 
 hemp merit peculiar attention, both as a territorial production, 
 and as the most extensive source of employment to the people. 
 This manufacture is spread over the whole country, and is sub- 
 divided into branches, from the fabrication of cordage to that 
 of lace, and it flUs up the intervals of rural labours. 
 
 One consideration which ought not to be overlooked, is, that 
 the land most proper for hemp is that of marshes, from which 
 the water has been drained, and that it is a production particu- 
 larly adapted to small cultivators.* 
 
 Flax and hemp must undergo several preparations before 
 they can receive a dye. The first is steeping, by which the 
 bark of the plant is rendered separable, so as to become fit for 
 spinning. Steeping is an operation of such importance, from 
 the influence which it possesses on the quality and quantity of 
 the product, and from the deleterious qualities which it may 
 communicate to the air, that it is proper to give some idea of 
 the principles on which it should be conducted. The steeping 
 of flax, in particular, has engaged the attention of practical 
 men. 
 
 In steeping, it appears that a glutinous juice, which holds the 
 green colouring part of the plant in solution, and which unites 
 its cortical with its ligneous portion, suffers a more or less com- 
 plete putrefaction, according to the method employed; for, as 
 Rozier remarked,f carbonic acid gas and inflammable gas are 
 disengaged. This substance seems to resemble closely the glu- 
 tinous portion dissolved in the juice expressed from green 
 plants, which is separated along with the colouring particles 
 
 * Instruction familiere sur la culture et le roui du chanvre, a Tusage des gens de la 
 campagne, par Pertuis. 
 
 f Essai sur la cultu reet le rouissage du chanvre, par TAbbe Rozier. 
 
112 
 
 BERTHOLLET ON DYEING. 
 
 when it is exposed to a heat bordering on ebullition, and which 
 putrefies, and yields ammonia by distillation. 
 
 Although this substance be held in solution in the expressed 
 juice of plants, there is a probability that water alone cannor 
 separate it sufficiently from the cortical part ; and hemp which 
 has been steeped in too rapid a stream, wants pliancy and soft- 
 ness. 
 
 If the steeping be performed in stagnant waters, the hemp 
 contracts a brown colour ; but, above all, it loses its durability, 
 and exhales vapours productive of dangerous maladies. What 
 is steeped by exposing it merely to the action of the elements 
 on the ground, is also weakened, and requires much time and 
 manual labour. 
 
 It appears, therefore, that steeping is performed in the most - 
 advantageous manner in tanks placed on the banks of rivers, in 
 which the waier may be renewed, so much as to prevent a 
 putrefaction hurtful to the hemp and detrimental to health, 
 without obstructing the putrefaction necessary to render the 
 glutinous substance soluble in water. 
 
 Rozier found, that the steeping process went on when the 
 hemp was covered with a layer of earth, and he recommends 
 this method ; but it has been ascertained that the hemp was too 
 easily aflTected in this operation. 
 
 Proset* has proposed to mix a small quantity of caustic 
 alkali with the water in which the steeping takes place, in order 
 to increase its solvent power, and to prevent the putrefaction ; 
 but it appears from the experiments of Home, that alkaJies 
 retard the operation of the steeping, and render the flax liable 
 to break.f 
 
 During the maceration, as well as the previous and subse- 
 quent drying, the green colouring particles suff'er an alteration, 
 like that observed in the green substance of plants which have 
 been exposed to the action of air and the influence of light. 
 Their colour passes to yellow, dun, or even brown, by an 
 agency which we have compared to that of a slight combustion. 
 
 That substance is partly reduced into powder, which is dis- 
 persed during the dressing, rendering this operation dangerous 
 to those who practise it. Another portion remains attached to 
 
 * Mem. sur le rouissage du cbanvre. 
 f Essay on Bleaching. 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 113 
 
 the fibres ; but perhaps dissolved in the alkaline leys employed 
 before the bleaching, whereby all this foreign matter ought to 
 be separated. 
 
 For avoiding the acrid dust which rises during the hatcheling, 
 Marcandier has recommended to macerate the fibres in small 
 portions in hot water, to wash them with much care, and 
 thereafter to dry them. By this means we may diminish the 
 colouring matter, and render the flax or hemp softer and better 
 prepared for the action of the hackle. He has even suggested 
 the use of an alkaline solution.* 
 
 On a more complete solution of the colouring particles, is 
 founded a process published by the Prince de Saint-Sever, to 
 obtain fine dressed hemp.f He recommends to put the tress of 
 hemp in a ley made with a solution of two parts of soda to one 
 of lime, next to impregnate it with soap, to digest it for some 
 time, then to wash it well, and lastly, to hackle it. Several 
 processes analogous to the preceding have since then been 
 practised, under the veil of mystery. Their results had an 
 imposing aspect. But experience has sufficiently shown, that 
 besides the expense which they incurred, these processes in- 
 creased the proportion of tow, and the yarn obtained had less 
 durability, and little advantage in beauty over the yarn yielded 
 by the unprepared hemp. 
 
 Bralle, an old curate of the department of the Somme, occupied 
 himself regularly for several years with the means of improving 
 the preparation of hemp, as an object of great national interest. 
 His first attempts consisted in steeping hemp, as soon as it was 
 taken from the ground. On coming out of the steeping, he 
 separated the bark from it, which easily came off*. After cut- 
 ting the stem near the root, and dipping it in a weak solution 
 of black soap, he washed it with much care before desiccation. 
 The colouring portion which would have become insoluble, 
 except in alkalies, may also be dissolved and carried off by 
 water, assisted by a little soap. The fibre is then much whiter. 
 By combining the action of the sun with this process, he suc- 
 ceeded in making it still whiter. 
 
 These operations had the inconvenience of requiring long 
 
 * Traite de clianvre. 
 
 f Joiirn. de physique, introd. torn. ii. 
 
 I 
 
114 
 
 BERTHOLLET ON DYEING. 
 
 and minute manipulations. Bralle, however, hit upon a process, 
 by which a large quantity of hemp may be steeped in a few 
 hours, with the advantage of freeing the stems from their bark 
 without any waste, of preserving the length of the fibres, and 
 consequently of producing much less tow. 
 
 The process of Bralle, whose efficacy has been verified at 
 the Conservatoire des Arts on hemp intended for cordage and 
 sail-cloth, has just been published by order of government. It 
 consists in keeping the hemp plunged for two hours in water, 
 containing a forty-eighth part of green soap (soft soap) in solu- 
 tion, which is maintained at a temperature of from 194° to 
 200° Fahr. (Note K.) 
 
 A mode has been discovered of giving to the dressed hemp, 
 and even to the tow, a division and fineness which qualify it for 
 the same spinning processes as cotton ; so that with this pre- 
 paration alone, or mixed with cotton, stuffs may be made which 
 have a much more considerable value, than those of hemp in its 
 natural state. 
 
 Marcandier seems to be the first who engaged in this pro- 
 cess. He recommends to give to the tow, first of all, the pre- 
 paration which he prescribed for the dressed hemp. " In card- 
 ing it like wool, a fine medullary white substance is got, for 
 which heretofore no use was known. It can be employed by 
 itself in this state, not only to make ouates (fine cotton,) which, 
 in many respects, is better than the ordinary ouates, but it may 
 also be spun into a very fine yarn. It may likewise be mixed 
 with cotton, silk, wool, and even hair ; and the yarn resulting 
 from these different mixtures, furnishes, in its numberless 
 variety, materials for new trials interesting to the arts, and to 
 several manufactures." 
 
 This object has engaged much attention in Germany. Herm- 
 stadt quotes several works which treat of it.* He states, that, 
 according to Meidinger, the staple of hemp acquires the elas- 
 ticity of cotton, when, after being purified by a solution of pot- 
 ash and muriate of soda, it is fixed on cylinders of wood, and 
 dried in a stove. It is also asserted, says Hermstadt, that 
 hemp takes a fine texture when its moist fibres are put into a 
 wooden chest, with alternate layers of wood-ashes, closing the 
 
 * Grundris der Farbekunst. 
 
DIFFERENCES BETWEEN WOOL, SILK, &C. 
 
 115 
 
 chest with a cover, and putting it into a stove, heated not just 
 so high as to burn the wood. 
 
 Hermstadt informs us, that the hempen webs which have re- 
 ceived these preparations, lose the appearance of cotton by 
 repeated washings. 
 
 In treating of bleaching with chlorine, another process will be 
 pointed out. 
 
 Flax and hemp intended to be dyed, must be subjected to 
 the same operations as cotton, namely, scouring, aluming, and 
 galling. 
 
SECTION III. 
 
 on bleaching by the oxygenated muriatic acid, 
 (chlorine.) 
 
 The art of bleaching by chlorine, is a direct application of the 
 chemical properties of this acid; for the first knowledge of 
 wliich we are indebted to Scheele, but which were developed 
 and submitted to a regular theory in 1 785. 
 
 At this period, the first attempts at applying this acid (now 
 the element chlorine) to bleaching were promulgated. These 
 were soon prosecuted in England by the celebrated Watt, and 
 afterwards by Bonjour, Descroizille, Welter, Widmer, and 
 Haussmann. A description of this art, still in its infancy, was 
 published in the Annales de chimie for 1789; meanwhile it 
 continued to make some advances, which were successively pub- 
 lished. A second description was given of it, chiefly on the 
 data of Welter,* who had persevered in its practice on the great 
 scale ; and those who are acquainted with this able chemist, 
 know what confidence may be reposed in his observations. 
 
 Since then, different treatises on this process have appeared. 
 We shall here give an idea of such of them as have come to our 
 knowledge. 
 
 Pajot des Charmes published one,f which appeared in the 
 year 8, (1799.) In this, he speaks only of the first description 
 which had been given in the Annales, and neglects one which 
 had been made public five years before his own work, and of 
 which several separate editions had been given. 
 
 He represents the process which had been promulgated as 
 very difficult to execute; but the corrections which he pre- 
 tended to introduce, do not appear to us to have any other 
 
 INTRODUCTION. 
 
 * Journal des arts et manufactures. An. 3. 
 
 t L'art du blancliiment des toiles, fils, et coton do tout genre. 
 
ON BLEACHING BY CHLORINE. 
 
 117 
 
 effect than to diminisli its precision or advantages. Thus he 
 suppresses the intermediate vessel, which we considered to be 
 useful. He recommends, as a very beneficial change, to sub- 
 stitute leaden tubes for those of glass. He mixes potash with 
 the liquor (aqueous chlorine) to suppress its odour, the effect 
 of which mixture had been appreciated in the original descrip- 
 tion ; he regards the odour of chlorine, in the v/ay it had been 
 prescribed, as an insurm.ountable obstacle ; and he gives an 
 account of the distress which he had suffered in repeating this 
 process. He would have become satisfied that the process 
 might be executed v/ithout inconvenience, had he carefully 
 followed the directions, or had he visited the establishments 
 conducted by Widmer, Welter, or several others who used it 
 at that period. He exclaims against the length to which the 
 prescribed number of leys and immersions must give rise. The 
 limits of this number had been said to be between four and eighty 
 and we find (page 106 of his treatise) that he increases the leys 
 to six, and the immersions to seven. He gives, moreover, a 
 process for making sulphuric acid, by v/hich sulphurous acid 
 only can be obtained, &c. 
 
 Chaptal published a notice about a process long used for 
 bleaching cotton in the southern parts of France,* which had 
 been pointed out in our second account of bleaching. The 
 cotton is impregnated with a solution of soda, and subjected to 
 the vapour of boiling v/ater in a close vessel, where this vapour 
 suffers compression ; after which it is exposed for some days 
 on the grass. This process gave occasion to O'Reilly to publish j 
 a work on bleaching.f We shall not discuss the method which 
 he there extols, because his assertions have not hitherto been 
 confirmed by the experiments to which they led several ope- 
 rators. We shall merely remark, that in the same work he 
 describes an apparatus as well adapted to the preparation of 
 chlorine; but this apparatus is such, that the vapour of the 
 chlorine, by its elastic action, would cause all the water of the 
 intermediate vessel to spout out by the tube of safety, which 
 in fact would soon be emptied by the same cause. Several of 
 his details show that he described from imagination. 
 
 * Bulletin de la Society PhilomiUique. Bmmaire, An. 8. 
 -j- Essai siir le blanchiment. 
 
118 
 
 BERTHOLLET ON DYEING. 
 
 We owe to Westrumb* a work on the new mode of bleacli- 
 ing ; but this skilful chemist intimates, that he describes this 
 art only from his own trials, without taking into account what 
 experience had taught to actual practitioners. Rupp has given 
 interesting experiments on this subject, of some of which we 
 shall avail ourselves. f 
 
 We do not hope always to make the best selection in the ope- 
 rations which we are about to describe ; but we shall be guided 
 particularly by the observations of Widmer and Welter, who 
 have conducted this process for several years with increasing 
 success. We shall not advance, on views simply conjectural, 
 even the modifications which might be contrived ; but experi- 
 ence will undoubtedly teach us more and more to simplify, 
 improve, and extend the usefulness of the process. Those who 
 wish to employ it only on inconsiderable objects, by neglecting 
 trifling interests, or by resting satisfied with partial eff"ects, may 
 easily simplify both the apparatus and the manipulations. 
 
 In particular cases, bleaching may be greatly abridged, and 
 even reduced to a few hours ; but we must study, in a manu- 
 facture, to establish a series of operations, the success of which 
 shall be proof against accidents, and which shall steadily procure 
 employment to the same workmen, rather than accelerate any 
 particular process. 
 
 CHAPTER T 
 Theory of Bleaching, 
 
 Chemistry has made such progress in our times, as to render 
 an acquaintance with it indispensable to the practice of several 
 arts ; but the one which has for its object the bleaching of yarn 
 and cloth by chlorine, requires, in particular, an operator to 
 whom the science is not unknown. 
 
 Chlorine is the accent substituted in this mode of bleachinor 
 for atmospherical air, which requires tedious exposure on the 
 grass. For directing its preparation and effects, we must 
 therefore be well skilled in its properties. 
 
 Muriatic acid (the marine acid of the old chemists, and the 
 
 * Bcraeikungen iiiid Vorschlage fur Blcicher. t Mem. of Manchester, vol. v. 
 
ON BLEACHING BY CHLORINE. 
 
 119 
 
 hydrochloric of the modern French school) combines with 
 oxygen, and thereby assumes the properties of chlorine ; but 
 to make this combination effective, the oxygen must have lost 
 its elastic state. Thus it exists in the oxyde of manganese 
 (manganese of commerce) in very considerable quantity. When, 
 therefore, one part of oxyde of manganese is mixed with four 
 parts of the fuming, or six parts of ordinary muriatic acid, one 
 portion of the acid combines with the oxyde of manganese, with 
 the disengagement of the oxygen superfluous to this combina- 
 tion, which combining immediately with another portion of the 
 muriatic acid, thu-s forms the chlorine. The operation is pro- 
 moted and completed by the action of heat. The chlorine 
 assumes on its separation the gaseous state, when it is soluble 
 in water. The resulting liquid is of a greenish-yellow colour, 
 and of a very penetrating odour. If the temperature approaches 
 that of freezing water, the chlorine gas becomes concrete, and 
 adheres to the tube which conducts it into the water, whence it 
 precipitates, so that the liquid is less impregnated than at a 
 somevv^hat higher temperature. 
 
 It is easy to show that the oxyde of manganese contains much 
 oxygen ; for on urging it with a strong fire, it evolves a great 
 quantity ; after which the oxyde can produce but very little 
 chlorine. 
 
 We may be easily satisfied also of the existence of oxygen 
 in the chlorine. We have only to expose to the light of the 
 sun a phial filled with the above liquid, from which phial a 
 bent tube dips under a receiver filled with water. Bubbles of 
 air are soon disengaged, which pass into the receiver, consti- 
 tuting an elastic fluid, which possesses all the properties of pure 
 air or oxygen gas. When these bubbles cease to issue, the 
 liquid has lost its odour, colour, and all its distinctive properties. 
 It is now water impregnated with ordinary muriatic acid. The 
 composition and decomposition therefore equally prove, that 
 chlorine is simply a combination of muriatic acid and oxygen. 
 But this speedy decomposition by light shows, that the oxygen 
 very readily abandons the muriatic acid, either to assume the 
 elastic state, or to enter into other combinations ; and it is on 
 this that the characteristic properties of chlorine depend.* 
 
 * See Note to page 38, 
 
120 
 
 BERTHOLLET ON DYEING. 
 
 If vegetable colours be plunged into chlorine, they disappear 
 more or less quickly ; and when there is a mixture of different 
 colouring particles, some disappear more readily than others, 
 the whole, however, being more or less affected. When the 
 chlorine has thus exhausted its action, it is found to be reduced 
 to the state of ordinary muriatic acid ; the colouring particles 
 have therefore abstracted its oxygen. If we evaporate the 
 liquid in order to examine the state of the colouring particles, 
 we find that it yields a blackish residuum, as if its particles had 
 suffered a slight combustion. (Note L.) 
 
 It is in this way also that colours are more or less speedily 
 destroyed by the action of the air, especially when it is promoted 
 by the solar beams, as was shown in the preceding section. 
 Hence chlorine easily and quickly produces the effects which 
 air and light operate in a longer space of time, because the 
 oxygen, deprived in part of its elasticity, and adhering loosely 
 to the acid, enters readily into combination with the substances 
 for which it has an affinity. 
 
 The filaments of flax and hem^p are enveloped in colouring 
 particles, retained in them by a true combination, and w^hicli 
 mask their whiteness. When these colouring particles combine 
 with oxygen they are decomposed, so as to become soluble in 
 alkalies. Hence the potash of the ley dissolves, and sepa^rates 
 them from the filaments. On repeating several times the 
 exposure on the grass, or the immersion in chlorine, and the 
 action of the leys, w^e separate all the colouring particles of the 
 filaments which remain white. By these operations the yarn 
 loses nearly one-third of its weight. 
 
 If an acid be poured on the solution of the colouring particles 
 in potash, and if we dry the precipitate formed, which remains 
 upon a filter, it is blackish, and has the appearance of a body 
 which has suffered a slight combustion, or has been carbonized. 
 The ley, when saturated with the colouring particles, loses all 
 its activity. What is here said of potash, is equally applicable 
 to soda. 
 
 Yarn bleached by the ordinary process, or by that just 
 described, has lost a portion of its strength, whence it no longer 
 can sustain the same weight as before bleaching ; but if both 
 operations be made with equal care, the yarn bleached by means 
 of chlorine preserves more strength than that which has been 
 
ON BLEACHING BY CHLORINE. 
 
 121 
 
 treated by long exposure on the grass, because tlie leys have 
 been less numerous, and the operations not nearly so long. 
 
 This mode of bleaching, then, is produced by the successive 
 action of leys and of chlorine. We must therefore describe the 
 apparatus and operations w^hich the chlorine solution and the 
 leys require, as well as the means of promoting their action, 
 preventing their inconveniences, improving the w^hiteness, or 
 giving to bleached objects the qualities that are desired. Lastly, 
 we shall examine some other applications of the properties of 
 chlorine. 
 
 CHAPTER II. 
 
 Of the Preparation of the Oxygenated Liquor^ 
 ( Solution of Chlorine.) 
 
 The purpose of the apparatus used in this preparation is, to 
 disengage the chlorine^ and to combine it with water. It is 
 therefore divided into two parts, — the one v/hich comprehends 
 the extrication of the gas, and the other its combination with 
 water. 
 
 For the first object, a furnace is employed, capable of contain- 
 ing an iron pot to serve as a sand-bath. It is usually con- 
 structed of brick. The inspection of the plate will give an 
 idea of one of these furnaces. In the sand bath is placed a 
 matrass containing the mixture, to be subsequently described. 
 
 Matrasses from 15 to 17 inches in diameter are preferable to 
 those of greater dimensions, because they are less liable to 
 break, are more easily managed, and much cheaper. The ellip- 
 tical form is more advantageous than the spherical, because with 
 an equal diameter the capacity is greater. If one matrass be 
 inadequate for procuring the liquor which is wanted, tv/o fur- 
 naces can be placed alongside of each other, (See fig. 1, 3, 4.) 
 w^hich can be put in action successively, or at the same time. 
 
 The second part of the apparatus in which the gas is received, 
 is the receiver. It has an interior diameter of nearly three feet, 
 but it may be 6^ feet and even more in diameter. Its sides and 
 its bottom ought to be form.ed of strong oaken staves, hooped 
 with iron, and covered with a cement. 
 
 To protect the inside of the receiver, as well as the cisterns, 
 from the action of the lic^uor, they must be covered with a 
 
122 
 
 BERTHOLLET ON DYEING. 
 
 resinous coat, of a consistence not soft enough to run, or hard 
 enough to break off in scales. 
 
 The interior of the receiver is furnished with three inverted 
 tubs, (fig. 2. L L L) destined to receive the gas extricated from 
 the matrass. The depth of each tub ought to be about 3 inches. 
 Their connexion with one another does not admit of iron, which 
 would be attacked by the chlorine. They are secured by trans- 
 verse bars fixed to the circumference of the receiver. The 
 space between the tubs and the sides of the receiver is 
 closed, with the exception of an opening, which permits the 
 liquor to communicate from one tub to another, and which 
 ought to be placed alternately on the opposite sides, as may be 
 seen, (fig. 1, 2.) 
 
 The inferior tub, as well as the middle one, carries in its 
 bottom a glass tube, destined to transmit into the upper the 
 chlorine, when the former are filled with it. This tube is half 
 an inch shorter than the interior edge of the tub, (fig. 2. P P.) 
 
 Between the matrass and the receiver is a bottle, into which 
 a little water is put. It has three tubulures. To one is adapted 
 the tube of communication between the matrass and itself ; 
 from the second proceeds the conducting tube (K. fig. 2.) destined 
 to convey the gas under the lowest tub of the receiver; the 
 third receives a tube open at both ends, which bears the name of 
 tube of safety, because it obviates absorption. To accomplish 
 this object, it must have, reckoning from the level of the water 
 in the bottle, a greater height than that of the portion of the 
 conductor tube, which plunges into the liquor of the receiver ; 
 otherwise the water of the bottle, pressed upon by the gas, 
 would escape at its upper part. The portion of this tube which 
 dips into the water of the bottle should also be shorter than 
 that of the conductor tube, which is above the level of the water 
 of the receiver ; so that when the vessels become cool, and a 
 partial vacuum is formed, the external air may enter by the tube 
 of safety before the water of the receiver can rush in through 
 the conductor tube. 
 
 All the tubulures are shut with accuracy, but in different 
 ways. The tube of safety, and the conductor tube are perma- 
 nently fixed. With this view, they are passed across a hollow 
 cork, which is coated inside and outside, with a mixture of wax 
 and turpentine, and forcibly pressed into the tubulure. 
 
 The tube of commu7iication between the matrass and the 
 
ON BLEACHING BY CHLORINE. 
 
 123 
 
 intermediate bottle should have a stopper at each extremity; 
 but as the stoppers must be removed at the end of each opera- 
 tion, they are not strongly pressed in, but merely covered with a 
 bladder, coated with the same mixture, to protect them from the 
 action of the gas ; and they are fixed down by packthread, or 
 rather by levers loaded with a weight at one of their ends. 
 
 Between the furnace and the intermediate bottle a deal parti- 
 tion is made, having an opening cut in it for the passage of the 
 tube of communication. 
 
 It is useful to attach to the upper tub a pipe, having a bent 
 extremity dipping into a vessel filled with solution of potash. 
 When, by any circumstance, the gas comes to fill the cavity of 
 this tub, the excess escapes by this pipe, and is absorbed by, the 
 potash, thus protecting the manufactory from the inconvenience 
 which would result from its diflfusion. 
 
 We may employ muriatic acid and oxyde of manganese di- 
 rectly, or we may substitute for the muriatic acid, sulphuric acid 
 and muriate of soda, which salt, when decomposed by this acid, 
 gives out the muriatic. The choice depends on the price of 
 those substances at the establishment. The process which we 
 are going to describe is the second one. It is the best, on the 
 whole. 
 
 Oxyde of manganese (manganese of commerce,) when of good 
 quality, is in black masses of greater or less size, composed of 
 small needles of a metallic lustre. It should contain very little 
 foreign mineral. It is reduced into powder, and well mixed 
 with the salt, in the proportions to be presently stated. 
 
 If a manufa^cture of sulphuric acid be at hand, we may dis- 
 pense with purchasing it concentrated, as it may be employed in 
 the state in which it comes out of the leaden chamber, provided 
 it have a proper degree of concentration. 
 
 Concentrated sulphuric acid, such as is found in commerce 
 under the name of oil of viti^iol, marks 168° by the hydrometer 
 of Twaddell, (1.848 specific gravity.) It is here presumed to be 
 in that state. 
 
 The proportions of the ingredients which appear to us most 
 suitable are, 10 parts of oxyde of manganese, 20 parts of sul- 
 phuric acid concentrated to the above degree, and 27 parts of 
 muriate of soda. We do not, however, affirm, that these are 
 the most exact proportions which can be determined. (Note M.) 
 
124 
 
 BERTHOLLET ON DYEING, 
 
 If tlie manganese is of inferior quality, which is discovered 
 by the residuum of the operation not retaining its black colour, 
 the proportion of it must be increased in the following opera- 
 tions till a residuum be left which preserves a tinge of black. 
 
 The sulphuric acid should be diluted with an equal weight 
 of water. Rupp and Westrumb recommend a larger propor- 
 tion. This mixture is best made in a leaden vessel. 
 
 Our process is presumed to be made with 1 1 pounds of man- 
 ganese, 22 of acid, and 29^ of salt. 
 
 After mixing the salt and manganese, they are introduced 
 into the matrass, which is then placed in the sand-bath, when 
 the sulphuric acid, previously diluted and cooled, is poured into 
 it. The tube of communication is now fitted to the orifice of 
 the matrass. The ascent of the water of the intermediate bottle 
 into the tube of safety denotes that the openings are air-tight. 
 This may be further ascertained, by presenting to them the 
 moistened stopper of an ammonia bottle ; for however small the 
 portion of chlorine may be which escapes, it becomes manifest 
 by a white vapour. 
 
 We may kindle the fire in the furnace before placing the ma- 
 trass in the sand-bath, taking care that the heat is not so great as 
 to expose the matrass to be cracked when set in it ; or we may 
 wait till the whole apparatus is arranged, before lighting the 
 fire. The heat is then to be very cautiously raised, till the in- 
 termediate bottle ceases to be filled with yellow vapours, and 
 till the conductor tube begins to grow warm. The fire must 
 now be extinguished. An operation for the above quantities 
 lasts from six to eight hours. We must not delay withdrawing 
 the matrass from the sand-bath till the movement of ebullition 
 be entirely calm. The tube of communication is to be unluted, 
 and whenever the sm.ell is somewhat dissipated^ the matrass is 
 taken out, and placed in a basket containing dry straw. It is 
 emptied whenever there is no danger of cracking the neck with 
 the heat. 
 
 During the operation, the part of the matrass exterior to 
 the sand-bath must be covered with woollen cloth, pasteboard, 
 or any similar substance capable of confining the heat. 
 
 The accidents to be feared in this operation are the boiling 
 over, and concretion of the residuum. The former occurs durinof 
 the heats of sum/mer. It is also occasioned by the bad quality 
 
ON BLEACHING BY CHLORINE. 
 
 125 
 
 of the manganese. It may be avoided in both cases, by diminish- 
 ing the doses. To guard against the obstruction of the tubes, 
 which might arise from the boiling over, they must be made of * 
 sufficient magnitude. If, however, through inadvertency, the 
 intermediate phial should be filled, so as to make it doubtful if 
 the mixture can pass into the receiver, the matrass ought to be 
 immediately removed. For if the mixture contained in it 
 passes into the receiver, yarn turned through the liquor would 
 take a yellow colour, which must be removed by means of sul- 
 phurous acid diluted with water. 
 
 The concretion of the residuum, which exposes the matrass 
 to be cracked during the emptying, may be occasioned by three 
 causes : the first is, too small a proportion of manganese ; the 
 second is, a lower temperature of the atmosphere than seven or 
 eight degrees, (about 46° F. ;) and the third is, keeping the 
 matrass in the sand-bath some time after the operation, which 
 happens when the heat has been pushed too far. The causes 
 being pointed out, it is easy to avoid them. 
 
 As the temperature approaches that of freezing water, the 
 gas occasionally takes a concrete form in the conductor tube, 
 so as to obstruct it. To prevent this misfortune, very wide 
 tubes must be employed. 
 
 Let us now turn our attention to the receiver. On adjusting 
 each tube, care must be taken to cover it with water, and to 
 extract all the air. This is done by means of a syphon intro- 
 duced into the side opening, from which the water is expelled 
 by blowing forcibly into its upper extremity. 
 
 The receiver being furnished with its tubs, and these being 
 covered with water, with the exception of the upper one, we 
 adapt the conductor tubes, passing them through the free space 
 between the upper and lower tubs and the side of the receiver, 
 and through an opening made in the board, which closes in the 
 middle tub on the same side. This opening must be exactly 
 shut as soon as the tubes are arranged. Lastly, the receiver is 
 filled with water, which is not to be emptied again unless when 
 repairs are to be made : care must however be taken every 
 morning to evacuate the air which may exist under the upper 
 tub, when the pipe just mentioned has not been placed in it. 
 
 From the arrangement of the tubs and the conductor pipe, it 
 is obvious that the gas always arrives beneath the lowest tub. 
 
126 
 
 BERTHOLLET ON DYEING. 
 
 and the liquor must consequently be strongest at the bottom of 
 the receiver. From this place also it must be drawn off, for 
 which purpose we adapt to the receiver a pipe (fig. 2. G.) of 
 wood, sand-stone, earthenware, or porcelain, which penetrates 
 to the bottom, and whose upper end is on a level with the edges 
 of the receiver. The liquor is run off by plunging a syphon 
 into this extremity, the longer branch of which terminates in 
 the water of the tub of immersion, (fig. 2. R.) In proportion 
 as the liquor flows out of the receiver, care is taken to replace 
 it by the addition of water or spent liquor. (Note N.) 
 
 CHAPTER III. 
 
 The defective manner in which leys are usually drawn, is the 
 most frequent, most powerful, and yet the least suspected cause 
 of the weakening of the substances subjected to bleaching. This 
 part of the art, practised at all times, important both by its 
 bad effects when ill conducted, and by the economy which it 
 introduces into bleaching, when suitably performed, has received 
 in modern times very little amelioration ; y et it has acquired 
 considerable improvements from more recent researches, especi- 
 ally those of Welter and Widmer. 
 
 It is necessary to know the exact quantity of alkali employed 
 in each ley, so as to be able to graduate its respective force, 
 and to proportion it to the quantity and nature of the mate- 
 rials to be bleached. Since the wood ashes, sodas, and the 
 different species of potash made use of, are composed of a mix- 
 ture of earths, salts, and alkalies, their weights indicate nothing ; 
 nor is the areometer a more faithful criterion, since the salts 
 mixed with the alkali also act upon it. Hence its indications 
 are more delusive as the proportions of the mixtures vary, not 
 only in the different species, but as they are not constant even 
 in^any one. 
 
 Home,* aware of the necessity of estimating exactly the 
 strength of leys, attempted to determine the quantity of alkali 
 
 * Essay on Bleaching. 
 
ON BLEACHING BY CHLORINE. 
 
 127 
 
 contained in the different substances employed by the bleachers, 
 by saturation with an acid. He thus assigned the order which 
 they ought to hold relative to their quality, and he has ex- 
 plained the nature of the substances found mixed with the 
 alkali, very ingeniously making allowance in his experiments 
 for the imperfection of the means of analysis then known. But 
 his results have not the precision of those since published. 
 Long afterwards* employed, for appreciating the real alkali of 
 potashes, the comparative precipitation of a certain weight of 
 alum, by pure potash, and by the potash under trial. Notwith- 
 standing the precautions which he suggested for removing the 
 causes of uncertainty attached to this mode of testing, he was 
 not able to give it either sufficient accuracy or simplicity.f 
 Lastly, Vauquelin took the task in hand, exhibiting the pro- 
 portions of the substances found in several species of com- 
 mercial potashes. He estimated the proportion of alkali, by 
 saturating with a nitric acid, of a very determinate degree of 
 concentration, the potashes submitted to examination, and by 
 comparing the quantity of acid necessary to its saturation with 
 the pure potash which it had required. 
 
 It is obvious, that since, in the art of bleaching, the alkaline 
 parts alone are of use, the value of potashes are to each other 
 as the quantities of acid necessary to their saturation ; and con- 
 sequently we become acquainted with that whose employment is 
 most advantageous, by comparing the price of each species with 
 the quantity of alkali which it contains. On these considera- 
 tions, Vauquelin constructed the following table : — 
 
 At the time of making his experiments, the potashes of 
 
 America, containing 0.743, 
 
 was worth 
 
 70 livres. 
 
 Pearl-ashes 
 
 }} 
 
 0.656 
 
 !) 
 
 60 
 
 Dantzic 
 
 99 
 
 0.524 
 
 ?J 
 
 57 I. lOs. 
 
 Treves 
 
 99 
 
 0.625 
 
 J5 
 
 55 
 
 Russia 
 
 99 
 
 0.670 
 
 >> 
 
 55 
 
 Vosges 
 
 99 
 
 0.385 
 
 55 
 
 35 
 
 Hence he concluded, that if the consumer wished to fix the 
 prices which he should give for each potash, according to the 
 alkali which it contains, taking for a standard the one which 
 
 * Ann. de chimie, torn. vii. ; and Treatise on Bleaching, 
 + Ann. de chimie, torn. xl. 
 
128 
 
 BERTHOLLET ON DYEING. 
 
 the above table presents as most advantageous, he would 
 have, — 
 
 1. For the potash of Russia . . 55 livres. 
 
 2. America .61 
 
 3. Pearlashes 54 liv. 3 sous. 
 
 4. „ Treves . . 51 6 
 
 5. ,f Dantzic . 43 
 
 6. Vosges . .31 12 
 
 He justly observes, that the data of these tables are subject to 
 variations, which fraud may increase ; but they may serve in all 
 circumstances as terms of comparison. 
 
 The testing of potashes, is useful,^ therefore, both for deter- 
 mining their commercial value, and as a guide in their subse- 
 quent employment. As the trials must be frequently repealed, 
 it is important to have a simple manner of doing it ; and under 
 this point of view, we know none preferable to that of Welter. 
 The process pointed out by the general administrators of gun- 
 powders and saltpetres,'* though better adapted to the end 
 which they proposed, is not so easy of execution. 
 
 We here give the process of Welter exactly as he practises it. 
 
 The principle of the testing is saturation with an acid. But 
 to render the different trials comparative, the acid must be of 
 a degree of concentration which is uniform, and easily ascer- 
 tained. Sulphuric acid, diluted with water till it is brought to 
 a determinate point of concentration, answers well. By saturat- 
 ing a certain weight of this dilute acid with a fixed weight of 
 fine pure chalk, dried by the heat of boiling water, the standard 
 may be fixed. This acid is the one most readily to be had, and 
 whose constitution is most uniform. The chalk selected for 
 determining its concentration is a substance equally common ; 
 it does not present the difficulties which occur in procuring 
 pure potash, and the temperature of boiling w^ater, eriiployed 
 for drying it, can be very easily observed with precision. To 
 avoid the embarrassment attending the preparation of standard 
 acid, a quantity of it sufficient for the trials of many years 
 may be made at once. 
 
 Yv^ere these analyses made on pieces of potashes taken at 
 random from the barrels, only ambiguous results would be got, 
 
 * Ann. dc cliimie, lorn, xli. 
 
ON BLEACHING BY CHLORINE. 
 
 129 
 
 because in the same barrel there are often different qualities. 
 The experiment should be made, therefore, only on solutions 
 prepared on the great scale as leys, and always with the same 
 weights of alkali to the same number of measures of water. 
 The most expeditious manner of making these solutions in the 
 cold, is to suspend the potash at the surface of the water in a 
 vessel of iron pierced with a great number of holes, or formed 
 of coarse iron wire. They should not be drawn off till we are 
 certain that the whole potash is dissolved, and till by agitation 
 the liquid is rendered uniform. 
 
 Besides these circumstances, the assay of potashes requires 
 slips of paper stained with litmus, or any other colour equally 
 sensible to acids, as that of mallows, radishes, &c. We should 
 also procure a glass rod, a small glass measure, and lastly, a tube 
 having as many times the capacity of the small measure, as 
 measures of water have been employed to one hundred-weight 
 of potash.— (See Plate II.) 
 
 We fill the tube with the solution of potash, and transfer it 
 into the goblet. We next fill the same tube with the test acid, 
 which is also poured into the goblet; we agitate with the glass rod, 
 and then draw a trace on one of the slips of stained paper with 
 the extremity of this rod moistened with the mixture. If the 
 trace do not become red, we add to the goblet a small measure of 
 the test acid, stir, and then make another trace on the paper, 
 alongside of the former. If the colour of the paper be not now 
 changed, we add one measure of acid more, and continue thus 
 .till the last drawn trace is red. 
 
 If we wish to compare the qualities of several potashes, it is 
 obvious, that we must regard as the best that which has required 
 the greatest number of measures of acid to produce a red streak, 
 since it is the one which saturates most acid. It is also obvious, 
 that we might express numerically the qualities of the different 
 species of potash, representing them by the number of measures 
 of acid which each of them has saturated ; which amounts to 
 counting the traces formed on the paper in each trial, taking 
 the first for as many as the tube contains of little measures, and 
 adding unity for each of the following marks till the last, which 
 ^we should not reckon, because its colour indicates that we have 
 passed the term of its saturation. 
 
 To obtain a suitable variation of the leys, it is convenient to 
 
 K 
 
130 
 
 BERTHOLLET ON DYEING. 
 
 have solutions of potash of an uniform strength, one for example 
 with which an equal number of measures of test acid and solu- 
 tion of potash are required to produce saturation. But whatever 
 be the value of a potash, its solution may be brought to this 
 point, by adding to it, for every hundred-weight of alkali, as 
 many measures of water, as there were measures of acid required, 
 to effect saturation on the quantity primarily employed. Hence 
 the number of measures of water forming the solution, ought 
 always to be equal to that which expresses the standard (titre) 
 of the potash. 
 
 If in an assay it should happen that the first trace was red, it 
 would be necessar}^ to add measures of the solution instead of 
 measures of acid; and hence potash should be added to the 
 solution to bring it to the fixed degree of concentration. 
 
 To make this more clear, suppose that we have employed 50 
 measures of water to dissolve one hundred-weight of potash, 
 (consequently the tube contains 50 times the small measure,) 
 and that we have '8 traces on the stained paper. The first count- 
 ing 50, each of the following 1, and the last being red, we would 
 say that the potash is of the standard 56 ; which would denote, 
 that to bring the solution to the fixed degree, (in this case 50,) 
 we must add as many times 6 measures of water as we have em- 
 ployed in hundred-weights of potash ; and employing potash 
 taken from the same cask, we should use 56 measures of water 
 for the solution. An assay made on opening the cask, is suffi- 
 cient for the whole period of employing that potash, remember- 
 ing to put, every time a new solution is made, as many measures 
 of water as the standard indicates. (Note O.) 
 
 The degree of concentration of these solutions does not allow 
 them to be employed directly in the leying. Only such a num- 
 ber of measures is taken as is necessary to give them sufficient 
 strength, when diluted with the water which fills the boiler and 
 the bucking tub, and for them to have the quantity of alkali 
 suited to the weight of the substances to be bleached. But 
 before pouring the alkali into the boiler, it is advantageous to 
 render it caustic ; for it has been proved, {Ann. de cliim, tom. vi.) 
 that in this state alkalies dissolve a fourth more of colouring 
 matter than when they are carbonated. The almost general^ 
 practice, however, is to ley in a mild state. It has even been 
 pretended, in some houses, that the lime employed to render the 
 
ON BLEACHING BY CHLORINE. 
 
 131 
 
 alkali caustic, injured the stuffs. The observations which we 
 have collected satisfy us, that this effect must be ascribed 
 solely to the increased energy acquired by the alkali, the 
 consequences of which may be prevented by a diminution of 
 its quantity. 
 
 To perform this operation, the lime newly slaked is put into a 
 large tub, the solution of potash is poured over it, they are 
 stirred together, and, after settling, the clear liquid is to be de- 
 canted off by means of a syphon. The residuum is then to be 
 washed away two or three times, and the washings added to the 
 ley. 
 
 One part of lime is sufKcient to render two parts of potashes 
 caustic. These proportions ought, however, to vary with the 
 qualities of the potashes ; and it is proper to ascertain that the 
 proportion of lime is not too great, because the property which 
 this substance possesses, of precipitating the colouring matter 
 held in solution by the alkalies^ (Ann. de chim. tom. vi.,) may 
 render an excess of it injurious. On this account, some solu- 
 tion of potash is to be mixed Vv^ith the liquor floating over the 
 lime, in the tub in which the potashes are made caustic, . If it 
 become turbid, it contains lime in solution, and solution of pot- 
 ash must therefore be added, till it no longer yields a precipitate. 
 
 We might probably apply this property of lime with advan- 
 tage, to carry off from spent leys the colouring matter with 
 which they are charged, and render them once more fit for 
 bleaching, by adding the proportion of alkali necessary to replace 
 that with which the stuffs remain imbued, so as to raise the leys 
 to the suitable standard. On the small scale, yarns have been 
 completely bleached, by employing in this way the very same 
 alkali in all the leys. It may be likewise beneficial, especially 
 in places where fuel is cheap, to evaporate the spent leys, and 
 to calcine the residua so as to destroy the colouring matter. But 
 these operations need only be performed on the first leys, which 
 are more concentrated, than the last. 
 
 According to the experiments of Kirwan* the use of alkaline 
 sulphurets might be tried. They have indeed the inconveniences 
 of producing spots in places w^hich come into contact with 
 metals ; but these will disappear by employing in the last leys 
 
 * Annal. de cliimie, torn. vi. 
 
132 
 
 BERTHOLLET OlS DYEING. 
 
 an alkali free from the sulphurets, or by passing them at the end 
 of this bleaching through an acidulated water. The following 
 is the order in which this celebrated chemist has classed, accord- 
 ing to their energy, the substances possessing the faculty of dis- 
 solving the colouring matter of flax: 1. The alkaline sulphu- 
 rets ; 2. Caustic potash ; 3. Caustic soda ; 4. Carbonate of pot- 
 ash ; and, 5. Carbonate of soda. Lime water appeared to him 
 to dissolve but a very little of it, which he ascribes to the small 
 solubility of the lime ; but independently of this cause, it is not 
 probable that lime, which forms an insoluble combination with 
 colouring matter held in solution by potash could of itself dis- 
 solve it. Kirwan observes, that sulphur did not augment the 
 solvent faculty of lime. Higgins, however, has stated, that there 
 is a remarkable economy in employing sulphuret of lime in 
 bleaching. Trials on the small scale have not had the success 
 that O'Reilly announced. — Journal des Arts, (Note P.) 
 
 The sulphurets present two inconveniences, which must 
 greatly diminish the benefit which their solvent faculty promises. 
 One is, to deteriorate rapidly boilers and metallic instruments 
 containing them ; another is, to waste a considerable quantity of 
 the chlorine, if the washings have not taken it completely out of 
 the matters that are bleaching. 
 
 The colouring matter acquires the property of being dissolved 
 by the alkalies only in the successive operations, between 
 every one of which whatever has become soluble ought to be 
 removed. Experience has proved that these steps are necessary 
 to obtain a fine white, not subject to vary; a white which 
 cannot be attained at a single operation.* The alkali deemed 
 necessary to dissolve the whole colouring matter of the sub- 
 stance we are bleaching, must therefore be divided into a cer- 
 tain number of leys ; and as it should be proportioned according 
 to the quantity of this colouring matter presumed to be present, 
 less of it may be employed in the last leys than in the first. 
 
 The most general manner of leying is the following : — 
 
 The large tub is so placed, that its bottom may be near to, 
 and on a level with the edges of a boiler, which is somewhat 
 sunk into excavated ground, to avoid too great an elevation of 
 the tub. A little above its bottom this is perforated with a 
 
 Annai. de cliira. torn. Xi. 
 
ON BLEACPIING BY CHLORINE. 
 
 133 
 
 hole, into which is fitted a small tube, that conducts the ley into 
 the boiler. The stuffs to be bleached are arranged in the tub 
 in horizontal layers. The boiler is then filled with water, which 
 is poured into the tub after closing the pipe that leads into the 
 boiler ; and this operation is continued till the water stands in 
 the tub a little above the goods, taking care to mingle with each 
 boiler-full of water a number of measures of solution of potash, 
 equably divided, so that with the last boiler-full the whole alkali 
 intended for the ley shall have been expended. The boiler 
 being equably filled, the fire is kindled, the pipe of communica- 
 tion is opened, and the water is kept at a uniform height in the 
 tub, by lifting it with a copper pail or bucket from the boiler, 
 and pouring it into the tub. When the ley (thus continually 
 lifted into the tub in proportion as it flows into the boiler) has 
 begun to boil in the caldron, the operation (of bucking) is pro- 
 longed more or less, according to the kind of matters that we 
 bleach, and the period of bleaching at which they have arrived. 
 The leying being finished, it is allowed to flov/ off* by a stopcock 
 fitted to the bottom of the boiler ; water is then poured into the 
 tub to cool it, and expel the remainder of the ley, after which 
 the tub is emptied. 
 
 Since the tub contains several times the capacity of the boiler, 
 and since, independently of the time which a considerable volume 
 of water takes to acquire a high temperature by the mixture (in 
 rotation) of a small quantity of heated water, the ley is continu- 
 ally cooled by the transfer from the boiler into the bucking- 
 tub, the ebullition in the boiler must be but very slowly brought 
 on. However long continued the leying may be, the tem- 
 perature cannot be carried higher than 72^ or 73^ (about 195^ 
 Fahr.) in the tub. From this arrangement it follows, therefore, 
 1. That a great body of water must be heated, in order that 
 the substances bleaching may be equably impregnated with the 
 ley ; and, 2, That we can give the leys only a heat inferior by 
 several degrees to that of boiling water. Hence the length of " 
 the operation, as also the waste of combustibles, and the great 
 labour: nor can the term of 80° (212° Fahr.) be obtained. 
 Several phenomena, however, and especially the superiority 
 found in patterns bleached in boiling leys, show how advan- 
 tageous the temperature of ebullition would be. 
 
134 
 
 BERTIIOLLET ON DYEING. 
 
 From these considerations Widmer contrived to place directly 
 above his boiler a tub, whose bottom was merely a strong lattice 
 work of wood. In the middle of the, boiler there is a pump 
 which raises the ley to the top of the tub, where it is diffused 
 by four pipes equal to the radius of the tub, and which are 
 turned circularly by a movement adjusted to the arm (lever) of 
 the pump. The ley is thus equably dispersed on the surface 
 of the goods ; it filters through them, and falls into the boiler. 
 Far from being liable to cool, it preserves its temperature in 
 this passage, because the goods are heated by the steam rising 
 from the boiler, which cannot escape except by passing through 
 their interstices. Two thermometers placed in an apparatus, 
 where the boiler was two yards in diameter, one at the base and 
 another at the top of a tub two yards high, constantly marked 
 the same degree of heat. In three hours of an uninterrupted 
 flowing, they both indicated 80°, (212° Fahr.) In the first trials, 
 Widmer made use of a tub whose height was two yards, and 
 whose diameter, equal to that of the boiler on which it stood, 
 was only two feet eight inches. The ley was drawn oS by a 
 stopcock adjusted to the bottom of the boiler, and it was 
 poured in with a bucket quicker than it could run completely 
 away. That remaining on the top of the goods boiled strongly 
 some minutes after the boiler was in ebullition, notwithstanding 
 the small surface which this apparatus presented to the vapour, 
 the cooling which the ley must have experienced in getting 
 back into the boiler from the top of the tub, and the distance 
 between this point and the boiler. By this method we may 
 communicate to goods a heat superior to that of boiling water. 
 The thermometers of the large apparatus rose to 84° (221° 
 Fahr.); but as soon as they passed the boiling point of water, 
 the pump could no longer raise the liquid ; and we do not 
 know how far it may be right to ley at higher temperatures. 
 To prevent the pressure of the steam from stopping the working 
 of the pump, Widmer next established four pipes, which open- 
 ing a communication between the upper part of the boiler and 
 that of the tub, gave a free outlet to the vapour. 
 
 This apparatus unites the advantages of leying in much less 
 time, at a boiling heat, and with less consumption of fuel ; for 
 intead of having to heat a ley incessantly cooled by the trans- 
 
i 
 
 ON BLEACHING BY CHLORINE. 
 
 135 
 
 fer, and which occupies the capacity of both the tub and the 
 boiler, the latter alone is filled, while the heat is preserved 
 during the running by the agency of the vapour. 
 
 Nearly 400 pieces, of from 23 to 24 yards each, may be leyed 
 at a time in an apparatus of the above dimensions. The longest 
 leying lasts six hours : it consumes five measures of coals. Its 
 efficacy is sufficiently proved by the uses to which the goods of 
 Widmer so bleached are applied, since there can be no more 
 delicate test for white, than the clearing the madder grounds of 
 printed calicoes ; and it has also diminished the number of opera- 
 tions to which he subjects the goods. We have had occasion 
 ourselves to ascertain these good effects on cotton cloth ; and we 
 believe that they will be experienced on applying this method to 
 the bleaching of linen webs. (Note Q.) 
 
 Bosc has asserted in a paper,* on which we have some reflec- 
 tions to offer, that it was prejudicial to the action of the alkali to 
 water the goods continually ; an idea which he founded on his 
 philosophical notions of bleaching. According to him, the so- 
 lution of the colouring particles in the alkali is a true combustion, 
 effected only on the colouring matter, because it is combustible 
 at a lower temperature than the fibres." Our only business, ^here- 
 fore, is to raise sufficiently the temperature of the steam, so as 
 to operate by its decomposition the combustion of the colouring 
 particles, which thus become soluble in the alkali. 
 
 When water is decomposed by means of charcoal at a much 
 higher temperature, there are produced carbonic acid and an in- 
 flammable gas, holding carbon in solution ; but the charcoal 
 w^hich has not entered into a gaseous combination has not become 
 more soluble in alkalies. This observation would be sufficient 
 to prove that the explanation of Bosc is not founded on the re- 
 ceived theories. 
 
 He makes Lavoisier say, that at 85 degrees of Reaumur, 
 (about 223"^ Fahr.) 'Svater forms a permanently elastic gas." 
 This illustrious chemist styled permanently aeriform fluids, those 
 which preserve this state notwithstanding changes of tempera- 
 ture and pressure. The vapour of water formed at 80° (212° F.) 
 under the ordinary pressure of the atmosphere, differs from that 
 formed at 85° only in being more dilated, and resisting a higher 
 (less) pressure. 
 
 * Bulietia de la societe creiicoiiiagement, pour riudustrie nationale. Crerminal, An. xi. 
 
136 
 
 BERTHOLLET ON DYEING. 
 
 He certifies, that in the apparatus which he describes, the heat 
 is carried beyond the 100th degree of Reaumur; but at nearly 
 17 degrees above the term of ebullition, (^50° F.) steam acquires 
 a double elastic force. His vast apparatus should therefore be 
 able to resist an effort superior to two atmospheres. He should 
 have bethought himself of determining the thickness necessary to 
 the great boiler which is to furnish this vapour, and have showed 
 us by what means he could fix down the different parts of the ap- 
 paratus to the masonry. 
 
 In making a comparative calculation of different modes of 
 bleaching, he regards as a matter of indifference the employ- 
 ment of chlorine without mixture, or combined with potash and 
 lime. We shall afterwards see how far this position is right. 
 
 When the results of different methods are compared, espe- 
 cially on cotton, where some days' expo^re on the grass forms 
 a part of these methods, and when it is not the object to attain 
 the most perfect white, it is easy to be led into error, because 
 all these methods readily yield a white, with which people may 
 often be satisfied. 
 
 CHAPTER IV. 
 Of the Immersions in the Solution of Chlorine, 
 
 If linen or cotton yarn is to be bleached, for its immersion 
 in the chlorine, we may place near the receiver a tub of the 
 same size, but a foot lower, (fig. 1, 2, A.) It is to be two-thirds 
 filled with water ; the liquor of the receiver is then run into it 
 by means of a syphon, as we have explained, agitating mean- 
 while, but without raising air bubbles. The hanks are arranged 
 in a basket of the same height as the tub of immersion, so as to 
 form two layers in it, leaving 8 inches empty. The basket 
 should contain from 220 to 330 pounds of yarns. This basket 
 is then raised by means of a crane or other equivalent machine, 
 and plunged into the immersion tub ; from which it is with- 
 drawn, and replunged into it continually, so as to renew inces- 
 santly the liquid which moistens the yarn. As soon as the 
 liquor is observed to be weakened, the basket is raised above 
 the tub^ and fresh liquor is run in from the receiver. This 
 process is continued luitil the liquor retains its strength, not- 
 
ON BLEACHING BY CHLORINE. 
 
 137 
 
 withstanding the repeated immersions of the yarn. This first 
 operation usually lasts two or three hours. 
 
 Instead of heaping the yarn in baskets, it may be plunged 
 much more freely in the liquor, by hanging it at two rods, 
 which pass through the middle of the hanks, and are supported 
 by a frame of the same size with the immersion tub. There is 
 then no danger of the yarn being bleached unequally. Less of 
 it, indeed, enters at a time into the tubs. The mode of working 
 is in other respects the §ame. 
 
 Chlorine weakens and even destroys yarns, as leys do, if it 
 be employed without precaution. Hence, when yarn is put 
 into a very strong solution it soon loses its tenacity. But it is 
 very easy to avoid this occurrence, by not dipping the yarn till 
 the liquid which comes out of the receiver be well mixed with 
 water, or be a dilute liquor with a supportable odour. In this 
 state of concentration, the chlorine does not attack yarn, though 
 plunged in it even for several days. We must not rest satisfied 
 with so vague a manner of judging, especially if we wish to 
 compare together several effects. 
 
 From the outset of his operations Descroizilles made use of a 
 solution of indigo in sulphuric acid, to estimate the comparative 
 strength of his liquors ; and he has since published a description 
 of the instrument which he contrived for this purpose.* The 
 solution of indigo ought to be prepared with seven parts of 
 concentrated sulphuric acid, and one part of fine indigo. These 
 two substances are mixed in a small matrass, which is plunged 
 for a few hours in water slightly tepid ; and the solution is then 
 mixed with 992 parts of water. 
 
 The strength of a liquor is judged of by the quantity of it 
 requisite in order that the colour of a stated measure of this 
 solution, in which the indigo forms 1 -1000th, be destroyed or 
 turned to a yellow hue. This trial is conveniently made with 
 a measure glass and a goblet, similar to those pointed out for 
 the trial of potashes. (Note M, latter part of.) 
 
 For a first immersion, the liquor may be of such a strength 
 that one measure of it shall deprive of colour from one-half to 
 two measures of solution of indigo. If the odour gives annoy- 
 ance, it may be diminished by diffusing some chalk and water in 
 
 * Journ, d'agriculture et des arts, torn, i. 
 
138 
 
 BERTHOLLET ON DYEING. 
 
 it. We have ascertained, that this easy method of obviating the 
 inconvenience of the smell, does not perceptibly impair the 
 energy of the liquor. The strength and duration of the im- 
 mersions which follow the first, are progressively less. Their 
 number varies also according to the fineness and quality of the 
 yarns. In general, they are limited to between five and nine. 
 
 Too weak a liquor should not be made use of, from fear of 
 weakening the yarn ; for its deficiency of action cannot be com- 
 pensated by a greater number of immersions. Tt is easy, more- 
 over, to avoid any accident from the liquor, by never omitting to 
 try its strength. Attention must also be paid, not to let the 
 yarn that is impregnated with it dry in the air ; it is thereby in- 
 jured, although no inconvenience happens while it is wet. 
 
 The bleaching of piece goods requires the same precautions. 
 The finer the cloth, the more economical, because it consumes 
 less liquor ; but to execute it commodiously, there must be, in- 
 stead of a single tub of the size of the receiver, four tubs suffi- 
 ciently large to contain each from ten to twelve pieces, 26 yards 
 long. These tubs, arranged one after the other, near the re- 
 ceiver, are each surmounted by a reel or winch. In front of the 
 first tub a table is placed, to which are attached at their corners 
 the ten pieces that are to be immersed together. After bringing 
 the liquor to the requisite degree, the end of the last attached 
 piece is thrown upon the winch of the first tub. A workman 
 immerses the pieces with a rod, in proportion as they pass over 
 the winch, which is turned by a child. The end of the last 
 piece is tied to a cord fixed to the framework of the winch, in 
 order that this end, which enters last into the tub, and which 
 finds the liquid now weakened by the pieces to whose train it is 
 attached, may enter first into the second tub, and that the end 
 which has been first in the preceding may, bypassing last into the 
 next, be placed in the same circumstances as the other. By giving 
 this rotation to the goods in the tubs, with a view of changing 
 them, and by successively passing each end first, they whiten 
 very equally. When the pieces have been passed from the first 
 into the second tub, new ones are introduced, which pass into the 
 second as soon as the former have entered the third, and which 
 pass in their turn into this, when the preceding pieces are in the 
 fourth. At the same time, fresh pieces should be put into the 
 first two tubs ; so that as soon as the pieces shall have travelled 
 
ON BLEACHING BY CHLORINE. 
 
 139 
 
 from one tub to another, others may enter immediately into the 
 former. When they have arrived at the fourth, and have remained 
 the requisite time in the liquor, they are piled up on the winch to 
 let them drain, then turned over on a wheelbarrow to be carried 
 to wash. Whenever the pieces are taken out of a tub, the 
 liquor of it is tested, that it may be restored to the proper 
 degree before introducing fresh pieces into it. Care should be 
 taken to plunge the pieces thoroughly, and not to let any of 
 their parts float above. The number, the strength, and duration 
 of the immersions, vary with cloths, as with yarns. 
 
 CHAPTER V. 
 Of the Washings, 
 
 Whoever projects an establishment should examine if the 
 place where he proposes to erect it, unites the advantages of 
 fabrication, commerce and carriage ; but, above all, he must have 
 pure water at command ; for, without this condition, he will not 
 succeed in obtaining a fine white. Muddy water, which leaves 
 a blackish deposite, may however be employed with success ; 
 but that whose deposite is yellow, gives always an unfavourable 
 shade. These observations are particularly applicable to the 
 bleaching of cotton, the white of which should have the greatest 
 lustre. 
 
 Immediately after each operation, we must, by a careful wash- 
 ing, discharge from yarns and stuffs the liquor with which they 
 are impregnated ; because, if it were carried into that of the 
 next operation, it would neutralize a portion of it, and thus im- 
 pair its action. This precaution, moreover, adds much to the 
 perfection of the white. 
 
 To wash linen or cotton yarns, a workman takes a hank in 
 each hand, plunges them in the water, agitates, withdraws, and 
 replunges them for three or four times, seizing the hank each 
 time by a different point. He then puts the two hanks together, 
 wrings them, and throws them down. 
 
 The washing of piece goods requires more apparatus in order 
 to be well executed. They are pretty generally washed by 
 hand, and beat with a rod or a mallet; but this method is im- 
 
140 
 
 BERTHOLLET ON DYEING. 
 
 perfect, especially because of the inequality of the washing. In 
 some establishments machines are employed, which accomplish 
 this object better. We are acquainted with none preferable to 
 that of the celebrated manufacture of Oberkampf, of which he 
 has had the kindness to impart the knowledge to several bleach- 
 ers. It consists of a strong beetle or mallet, which strikes the 
 pieces arranged on a circular table, moveable round a pivot. A 
 description, detailed enough to guide to its construction, would 
 require too much room for us to give it a place here. 
 
 We may, however, obtain a pretty complete washing, sufficient 
 for the most part of goods, by making use of two wooden rollers, 
 placed one above another on frames, set in the direction of the 
 breadth of a river. Their length is 1 foot 4 inches, the under 
 one is 1 foot 7 inches in diameter, while the upper is only 1 foot 
 4 inches. The latter is fluted parallel to its axis, the depth of 
 each furrow being nearly equal to one-half of the ridge. At 
 each extremity it has a pivot, fitted to a groove cut in the frame, 
 (support.) These pivots are not fixed, hence this cylinder can 
 rise freely above the other. The surface of the under roller is 
 smooth ; and it carries a handle at one of its pivots. When we 
 wish to wash goods by its means, we throw the piece into the 
 water, laying hold on one of its ends, and putting it between the 
 two cylinders. On turning the winch, the cloth passes between 
 them, pressed by the upper one, which, at every groove re- 
 ceives a small stroke, and communicates it to the cloth in its 
 tumbling round. Pieces passed in this way five or six times 
 successively, are very well washed. 
 
 To moisten goods, or to wash them slightly, we may also em- 
 ploy a species of reel (winch) with four leaves, placed on a river, 
 like the rollers. The piece whose end is laid on the reel is 
 thrown into the water, and, turning on the reel, the piece passes 
 over it, and falls on the other side into the water. If it be 
 rapidly enough turned, and if the pieces be thus passed several 
 times, they will be tolerably well washed by this simple means. 
 
 What has now been stated shows the advantages of arranging 
 the workshops as near as possible to the water pUiced at our dis- 
 posal. (Note R.) 
 
ON BLEACHING BY CHLORINE. 
 
 141 
 
 CHAPTER VI. 
 Of the other operations of Bleaching, 
 
 The bleacliing of goods commences by leaving them for some 
 time in tubs full of water. In a few days a fermentation com- 
 mences, which promotes the separation of the colouring matter, 
 and particularly of the paste with which weavers imbue their 
 webs. This operation, which is called ungumming, may, without 
 injury, last for eight or nine days, at mean temperatures. It 
 may be longer when the air is cold, and ought to be shorter in 
 summer, because it is to be feared that fermentation, pushed too 
 far, would affect the texture of the goods. Old leys are also 
 used for this purpose ; but the experiments of Home prove, that 
 it is more advantageous to employ only pure water. 
 
 As to yarns, it is sufficient for them to be steeped for two or 
 three days. 
 
 If the moist grey yarn, on coming out of the ley, be piled up, 
 it gradually heats, and eventually takes fire ; but if it reaches 
 only the animal temperature, it is not perceptibly weakened ; 
 the slight combustion which it thereby experiences even contri- 
 buting to the effect of the leys. If it be shut up in the dark, 
 however, when ill dried, it is speedily destroyed. 
 
 When no more greyness remains in linen yarn, or linen cloth, 
 which commonly occurs after the fourth immersion, it is passed 
 into water acidulated with sulphuric acid. For this purpose, 
 into a small tub containing water, sulphuric acid is poured, till 
 the mixture has assumed a degree of sourness approaching to 
 that of lemon juice. Into this the yarn is dipped, handful after 
 handful, so as thoroughly to imbue it. It is then thrown into 
 another tub large enough to hold 1200 pounds of it, in which it 
 is left for about 15 or 20 hours before being removed. A longer 
 continuance, of two or three days, for example, can do no harm, 
 provided care be taken that no portion of the yarn rises out of the 
 acid. As to piece goods, they are attached end to end, and passed 
 by means of a reel through large tubs full of acidulous water. 
 Linen yarns and cloth are passed three or four times through 
 the acidulous water, making it progressively weaker. It is suffi- 
 cient for cotton goods and yarn to be passed once. The quantity 
 
142 
 
 BERTHOLLET ON DYEING. 
 
 of acid employed in the first liquor is 18 pounds, for 1320 pounds 
 by weight ; and this proportion is diminished at each subsequent 
 operation. 
 
 Great pains must be taken to wash perfectly before and after 
 the acidulous water, otherwise a fine white can never be ob- 
 tained. It is no less important to prevent the yarns or cloth im- 
 pregnated with acidulous water from remaining long exposed to 
 the air ; for as the water evaporates, the acid becomes concen- 
 trated, acts on the fibre, and destroys it. 
 
 The acid dissolves the iron which in the course of the opera- 
 tions had been deposited on the stuffs, communicating to them 
 a faint yellowish tint. In proof of this, the prussiate of potash 
 occasions, after some time in the sour, a blue precipitate. But 
 is the action of the acid confined to the above use ? If it be, why 
 repeat this operation four times, and apply a ley between each of 
 them, while for cotton, equally exposed to be stained by the 
 ferruginous deposite, a single sour is sufficient ? 
 
 In Flanders, Holland, and Ireland, the bleaching of cloth by 
 the ancient methods is accelerated, by letting them stand for 
 several days in the acidulous liquors. Sour milk is commonly 
 employed for this purpose ; sometimes, also, bran or rye-meal is 
 mixed with the cloths, and the liquor of the tubs becomes sour 
 from fermentation. It was long believed that the fermentation 
 itself promoted the bleaching ; but it is now well proved that it 
 is the acid alone which acts. Home has satisfied himself, that 
 the vegetable and mineral acids may be substituted for milk and 
 rye-meal ; that sulphuric acid, however, combines most advan- 
 tages ; that muriatic and nitric acid produce the next greatest 
 effect, which effect is aided by a gentle heat: He assures us, 
 that sulphuric acid does, in five hours and less, what could be ob- 
 tained only in five days with bran or milk. To these substances he 
 also makes the serious objection, that they frequently run into 
 putrefaction, and thus affect the fabric. We may hesitate the 
 less to substitute water acidulated with sulphuric acid for milk 
 or rye-meal, as this change has been long adopted in England, 
 and in several French bleach- works. 
 
 Notwithstanding all these operations, the thread has not yet 
 got all the whiteness of which it is svisceptible. There remains 
 a matter insoluble in acids and alkalies, which is removed by 
 powerful washings in water frequently repeated, and by some 
 
ON BLEACHING BY CHLORINE. 
 
 143 
 
 days' exposure on the grass. There is a certain yellowish tint, 
 which is more effectually destroyed by the action of air and 
 light, than by that of chlorine. In general, yarns of a yellow 
 colour bleach with more difficulty than those of a grey hue bor- 
 dering on brown. For those, it is right to lengthen somewhat 
 the exposure on the ground. 
 
 For giving softness to yarns, some pounds of soap are added 
 to the last leys. Immediately afterwards they are laid out on 
 the green, on being lifted from which they are washed with great 
 care ; for if they retain any soap, their white might change. In 
 linen webs, the selvages being of a denser texture than the rest, 
 preserve for a longer time a tint, which can be completely re- 
 moved only by reiterated washings and soft soap. It is the 
 same with all the places on the body of the cloth where there 
 are broken threads repaired during the manufacture. These 
 constantly preserve a black hue, which yields only to rubbing 
 with a hot solution of soap, of greater or less strength. Some 
 persons are in the practice of treading the cloths in tubs along 
 with this solution, one or two times, towards the end of the 
 bleaching. This operation is performed with the feet, tramping 
 more or less according to the hardness of the web. • To cleanse 
 the cloth completely, it is soaped by hand in tubs, whose edges, 
 instead of being perpendicular to the bottom, are turned con- 
 siderably outwards, forming an inclined plane, on which the 
 workmen rest their webs, so as to rub them more convenienttyo 
 If the goods are almost quite cleared by the two treadings, a 
 single rubbing is sufficient to bring the selvages to the same tone 
 of white as the rest of the piece; most frequently two are given, 
 especially to webs of a dense texture, or , of a coarser yarn. 
 Occasionally they are obliged to rub, even separately, the spots 
 where the black threads are observed. All these manipulations, 
 by cleansing thoroughly the goods, give them, moreover, a cer- 
 tain pliancy, and that marrowy feel which is in request. The 
 whole of the soap that may possibly remain is removed, by ex- 
 posing them on the field, and washing them several times in 
 limpid water. The soaping does not begin till the webs have 
 passed once through the acid, care being had to lay them down on 
 the grass on their quitting each operation, and to water them on 
 it. They are next washed and lixiviated. The acid and soap 
 are alternated, till a perfect white be formed. 
 
144 
 
 BERTHOLLET ON DYEING. 
 
 Cotton stuffs do not present the same difficulties. The black 
 threads are easily cleared towards the end of the bleaching, by 
 soaping the places where they are observed ; but the selvages 
 whiten as rapidly as the body of the web ; and exposure on the 
 green may be dispensed with. 
 
 When a perfect white is obtained, the blueing is given in the 
 following way : — 
 
 The most beautiful azure-blue {smalt) is selected, the colour 
 of which proceeds from oxyde of cobalt reduced to a very subtile 
 powder. It is diffused through a little clear water. Some of 
 the water thus charged is drawn off, and passed through a silk 
 scarce, into a small tub filled with the most limpid water; and when 
 the workman judges, by a trial made on a handful of thread, 
 that the water is sufficiently charged, he passes through it 
 all the thread in succession, squeezing it, and taking care to 
 add blue from time to time, to keep the shade uniform. The 
 yarn is now carried to the wringing frame, and then dried in 
 the open air. 
 
 The preparation is the same for piece goods. They are wrung 
 at the peg, and dried. As to gauzes, lawns, and some other 
 cotton stuffs, a little starch is added to the water containing the 
 azure-blue. Cambrics are usually passed twice through the blue, 
 letting them dry between each operation. 
 
 CHAPTER VII. 
 Number and Order of the Operations, 
 
 Suppose there is a solution of potash made in the proportion 
 of 40 measures of water, each weighing 16 pounds, for a hun- 
 dred-weight of potash, and 1250 pounds of thread. 
 
 The linen or hempen yarns having been steeped in water for 
 three days, are to be well washed, and arranged in the ley-tub. 
 
 First ley ; 20 measures of solution of potash, three hours of 
 boiling. The ley, on cooling, becomes thick like a jelly. 
 
 Second ley^ for completing the removal of as many of the 
 colouring particles as possible. This ley contains 10 measures 
 of solution ; and the boiling lasts for two hours. 
 
ON BLEACHING BY CHLORINE. 
 
 145 
 
 Washing, to carry off the ley and the colouring particles 
 which it has dissolved. 
 
 First immersion. Liquor at 2° ; that is, of such strength that 
 one measure of liquor discolours two measures of solution of 
 indigo. The immersion is continued till the yarn no longer 
 weakens the liquid, after it is restored to its standard strength. 
 
 Washing, 
 
 Third ley ; 12 measures of solution; three hours of ebulli- 
 tion. 
 
 Second immersion. Liquor of the same strength as the first. 
 Fourth leg ; 8 measures of solution; two hours of ebullition. 
 Third immersion. 
 Washing. 
 
 Fifth ley ; 5 J measures of solution ; two hours of boiling. 
 Fourth immersion. Departing from this point, the liquor is 
 brought down to 1°. 
 
 Washing, At this period the white is usually manifest. 
 Acidulated water. 
 Washing, 
 
 Sixth ley ; 5 J measures ; two hours of ebullition. 
 Exposure on the green for six days. 
 W ashing. 
 Fifth immersion. 
 Washing, 
 Acidulous water. 
 Washing. 
 
 Seventh ley ; 4^ or 5 measures ; one hour of ebullition at 
 least. 
 
 Sixth immersion. 
 Washing. 
 Acidulous water. 
 Washing, 
 
 Ley and soap ; 3 measures of solution. To this 8 pounds of 
 black soap are added ; and the solution is heated till the hand 
 cannot be tolerated in it. When the soap has penetrated 
 thoroughly, the process is stopped. 
 
 Exposure on the grass, three days. 
 
 Washing, 
 
 Blueing, 
 
 L 
 
146 
 
 BERTHOLLET ON DYEING. 
 
 After this operation, the bleaching is finished, the thread is 
 wrung out, and is set to dry. 
 
 The operations are the same for linen cloth, only they must be 
 preceded by the ungumming. There may also be run upon 
 them, before the first ley, hot water, to which no alkali is added ; 
 an operation which lasts three hours. If the goods be not suffi- 
 ciently whitened, the bleaching must be continued in the order 
 indicated, setting out from the last ley. 
 
 The cotton cloths are ungummed, (freed from the dressing,) 
 then receive the hot water, and the operations prescribed for 
 yarns down to the last immersion. At this time they are white. 
 They are passed into blue acidulous water, and next dried. In 
 the first immersion, the liquor should be of only 1°, and some- 
 what weaker for the subsequent ones. A few measures less 
 should likewise be put in each lixivium. The black threads are 
 soaped after the third immersion. For cotton in hanks, the 
 same mode of operating is proper. 
 
 CHAPTER VIII. 
 Of the Different Preparations of Chlorine Liquor. 
 
 In the first experiments which were attempted on bleaching, 
 though it was proposed merely to employ the property which 
 chlorine possesses of destroying colours, yet potash was mixed 
 with it, which seemed to accelerate its effect. It was soon per- 
 ceived, that in order to obtain a uniform white, without weaken- 
 ing the cloth, the operations of ordinary bleaching must be 
 imitated ; the oxygenation of the colouring particles by a 
 liquor weak enough to do no injury to the fabric, being followed 
 up by the action of leys which serve to dissolve them. 
 
 Soon after the practice of the new bleaching had begun to be 
 established, a liquor mysteriously talked of, was prepared at 
 Javelle, which is still employed under the name of the lixivium of 
 Javelle.* It is a combination of chlorine with a certain propor- 
 tion of fixed alkali. This liquor can be imitated by employing 
 
 * Ann. de chimie, torn, ii. 
 
ON BLEACHING BY CHLORINE. 
 
 147 
 
 the following proportions for the distillation and the alkaline so- 
 lution :— Muriate of soda, 1193 grains ; sulphuric acid, 945 gr. ; 
 oxyde of manganese, 465 gr. The gas disengaged from these 
 materials is received in If pints of water, in which 1860 gr, of 
 common potash or soda have been dissolved. This liquor is to 
 be diluted for use with 10 or 12 parts of water. 
 
 To diminish the offensive odour of the chlorine, Descroizilles 
 mixed with it carbonate of lime or chalk. 
 
 A short time since, Tennant made a preparation for which he 
 obtained a patent in England : it is a combination of chlorine 
 and lime, or chloride of lime. This substance has the property 
 of absorbing readily a great quantity of chlorine. To obtain 
 this combination, it is requisite merely to pass the gas, as it is 
 disengaged, through slaked lime till it be saturated. This lime is 
 afterwards dissolved in a certain proportion of water; which 
 solution is employed in bleaching. Its effect maybe augmented 
 by the addition of a little sulphuric acid. ; ^^2^^ 'Ji^^^^'^fe^H^^^ ^'^'P"^%\ 
 
 To judge of the effect obtained from these different prep^am- 
 tions, and of their relative utility, we must call to mind, first of 
 all, the results of observations collected from the theory. 
 
 Oxygenated muriatic acid (chlorine) is composed of two ele- 
 ments, which are feebly united, and which are disposed to enter 
 into other combinations ; whence the easy oxygenation of sub- 
 stances exposed to its action. But this action is exerted with 
 greater facility and energy when not impaired by any combina- 
 tion which the chlorine may have previously made. Thus, in the 
 gaseous state, it acts with more energy than when it has been 
 combined with water beforehand ; and in that case its activity may 
 be too great for the object proposed in bleaching. The action of 
 the water, however, being very feeble, the liquid retains a lively 
 odour, and there may be obtained from it its whole sensible effect, 
 only retarded and modified at will, according to the concentration 
 which is given it. 
 
 The alkalies exercise a much more powerful action on chlorine 
 than water does, and thereby can give it a much greater con- 
 densation, repressing almost entirely its smell, which requires 
 freedom of expansion, and solution in air. The above (alkaline) 
 liquor is dissolved in a sufficient quantity of water to accomplish 
 the intended object of obviating the inconveniences of too brisk 
 an action. It produces its effect more quickly, probably because 
 
 L 2 
 
148 
 
 BERTHOLLET ON DYEING. 
 
 the potash tends to form a more intimate and more energetic 
 combination with the muriatic acid, while the colouring matter 
 exerts its action on the oxygen. 
 
 The advantages presented by the lixivium of Javelle, — the 
 chloride of potash or soda, are therefore — 1. To require a less 
 complex apparatus, for it is sufficient to employ a receiver con- 
 taining the alkaline solution, in order to condense the chlorine 
 gas, with the single precaution of plunging the conductor-tube 
 to the bottom of the receiver, and receiving the gas under a tub ; 
 2, To repress almost entirely the suffocating odour of the chlo- 
 rine ; 3. To furnish the agent of oxygenation, much more con- 
 densed, imder the same volume, and consequently to render it of 
 easier and less expensive carriage ; 4. lastly, To produce its effect 
 somewhat more speedily. — Let us next examine the disadvan- 
 tages of this preparation. 
 
 When a fixed alkali acts on the oxygenated muriatic acid 
 (chlorine) the effect is not simple ; a portion of the oxygen- 
 ated muriatic acid is merely condensed, retaining the proportion 
 of its elements, and the properties dependent on the tendency 
 which they preserve to enter into other combinations. 
 
 Another portion is decomposed ; and the result of the two 
 new combinations which are established in its stead, gives from 
 five to six parts of muriate of potash for one of chlorate of 
 potash, a salt which contains nearly 0.38 of its weight of oxygen, 
 to which it owes its characteristic properties. Now, the oxygen 
 present in this last combination, in which it is accumulated, is so 
 fixed down, that it can no longer attack the colouring particles, 
 nor resume the elastic state by the action of light. The whole of 
 the chlorine which suffers this transmutation of combination, is 
 therefore lost for bleaching. Its quantity varies according to the 
 condensation of the alkaline liquor which receives the gas, and it 
 appears to increase when the liquor is kept ; probably tempera- 
 ture causes the results to vary.* 
 
 We thus perceive that liquors, analogous to the lixivium of 
 Javelle, ought not to produce in their agency on the colouring 
 particles so much effect as the simple aqueous solution, which 
 contains, under the same liquid volume, a quantity of chlorine 
 gas equal to what has been condensed by the alkali. 
 
 Essai de statique ckimique, torn. ii. 
 
ON BLEACHING BY CHLORINE. 
 
 149 
 
 It has even been found, that by adding simply an alkaline so- 
 lution to chlorine, its discolouring effect was diminished. Rupp 
 has made decisive experiments on this subject. He employed a 
 solution of indigo for comparing, by the quantities of which the 
 colour was destroyed, the chlorine without mixture, with the 
 same after adding to it different proportions of potash ; but to 
 avoid the uncertainty which might have proceeded from the 
 action of the sulphuric acid on the potash combination, he de- 
 composed the solution of sulphate of indigo by acetate of lead, 
 thus rendering what he used, a solution of indigo in acetic acid. 
 He made similar trials with an infusion of cochineal, which is 
 still less liable to objections. It results equally from both, that 
 in proportion as potash is added, the bleaching power of chlorine 
 is diminished. The difference between the simple solution o 
 chlorine, and that with which he had mixed most potash, was 
 nearly one-fourth in favour of the former. 
 
 It is therefore proved, by theoretical considerations and direct 
 experiments, that the addition of an alkali, when even it is not 
 employed to condense the chlorine, impairs the effect which this 
 ought to produce. But in the lixivium of Javelle, it raises the 
 price of the liquor nearly three times higher. It is obvious, that 
 these disadvantages ought to make the use of it be rejected in a 
 manufacture where economy is an indispensable condition. 
 
 The chloride of lime has one advantage over the lixivium of 
 Javelle, from the great difference of price between lime and pot- 
 ash or soda ; and its state of condensation and desiccation, renders 
 its carriage less expensive. But it has also the inconvenience of 
 transforming a portion of the chlorine, and of containing chlorate, 
 which cannot be indicated in this combination by nomenclature, 
 which is precise only with regard to very uniform combinations : 
 it appears even that the proportion of chlorate is considerable ; 
 for if, after expelling, by a slight degree of heat, the chlorine 
 which has retained its properties, the remaining substance be ex- 
 amined, it is found no longer to produce discoloration ; and if 
 it be urged Vv^ith a stronger heat in this state, much oxygen gas 
 is disengaged. "Welter tells us, that in his comparative experi- 
 ments, he had observed, that the gas condensed by lime pro- 
 duced only one-tenth of the effect which may be obtained when 
 it is received in water. The use of the chloride of lime must 
 therefore be disadvantageous ; but it may be convenient for 
 
150 
 
 BERTHOLLET ON DYEING. 
 
 certain purposes, from the facility of carriage and preservation, 
 where the economy of the process is of secondary consequence. 
 Under this point of view, it merits the commendation, which it 
 has received. (Note S.) 
 
 The addition of sulphuric acid to the solution of the chloride 
 of lime, increases the effect, by the decomposition of the chlorate; 
 but to produce this effect fully, a quantity of acid is required 
 which might become dangerous. 
 
 These objections do not apply to the addition of chalk, which 
 has been recommended by Descroizilles, of which he makes use 
 in his elegant manufactory. Its value is very trifling ; and al- 
 though our experiments appear to prove that it somewhat les- 
 sened the total effect of the chlorine, yet this diminution is so 
 small that it may be neglected. Hence, though the process with 
 the simple solution of chlorine may be executed without incon- 
 venience, there is no harm in employing the addition of chalk, 
 so as to repress the greater part of the odour. We even recom- 
 mend not to omit its use, whenever persons are not very well 
 instructed in conducting the operations with the customary at- 
 tentions which are required. 
 
 CHAPTER IX. 
 Of the Other Uses of Chlorine, 
 
 The property of discolouring and whitening which chlo- 
 rine possesses, has met with several applications, which their 
 analogy to bleaching, and their relation to the art of dyeing, in- 
 duce us to enumerate. 
 
 When cloths have been printed with different mordants, they 
 are passed into the madder, where the designs assume different 
 hues, according to the nature of the mordants ; but the (vacant) 
 ground of these cloths also receives the madder colour. This 
 colour is much less fast than that which has been fixed by the 
 mordants ; and it must be destroyed by means of cow-dung and 
 bran, and long exposure on the grass. Nearly the same process 
 is employed to destroy the yellow ground of printed goods which 
 have been passed through weld to give the figures those hues 
 which belong to yellow. At Manchester, the properties of clilo- 
 
ON BLEACHING BY CHLORINE. 
 
 151 
 
 rine, modified by certain operations, which have not been made 
 public, were speedily applied to that purpose. 
 
 Widmer and Haussman made some trials, each in his own way, 
 from which it was ascertained, that a liquor, composed in the 
 proportions which we have pointed out for the lixivium of Ja- 
 velle, might be employed with success, but with the precaution 
 of diluting it for use with a larger quantity of water. We shall 
 state the result which Widmer has given of his experiments. 
 
 When the cloth comes out of the madder, it is exposed for 
 four or five days on the grass ; it is then passed through a bath of 
 cow-dung, after which it is laid down four days longer on the 
 grass, as at first. It is now submitted to an immersion of about 
 half an hour in the bleaching liquor, previously diluted with 
 about 35 parts of water. After this operation, the cloth must 
 be exposed for two days on the grass. It is then subjected to a 
 new immersion, and exposed for other two days on the field. 
 Betwixt each operation the cloth must be well washed and 
 beetled. The exposure on the field, here prescribed, is under- 
 stood to be during fine weather ; for in bad weather it must be 
 exposed some days longer. In general, the ground of a cloth 
 which has been well maddered, in order to have fast thorough- 
 proof colours, should be perfectly white after this manipulation. 
 
 It appears from this detail, that we no longer employ bran at 
 all for the whitening of maddered goods. It is also obvious, that 
 we have infinitely reduced the heating operations, since formerly, 
 a piece of goods, after the maddering, received at least from 
 three to six boils, whilst at the present day it gets one, or two at 
 most, and it is an infinitely less time on the grass. 
 
 I have often bleached maddered goods without giving them 
 any boil, submitting them merely to immersions every twenty- 
 four hours, and exposing them alternately on the field. But this 
 has several inconveniences. In the first place, the goods are 
 liable to have spots of a brick-red colour, which the workmen 
 call madder stains ; they proceed frequently from adulterated 
 madders ; an inconvenience felt only with the madders of Alsace. 
 At other times, fat or oily matters, which are present in the 
 goods, are the cause of them. These stains oblige us pretty 
 often to subject the cloth to two boils, because the action of the 
 acid, and the exposure on the grass, are insufficient. 
 
 The goods, on coming out of the madder, are laid on the 
 
152 
 
 BERTHOLLET ON DYEING. 
 
 field, because the large quantity of colouring matter deposited 
 on their ground, destroys too great a quantity of the acid, and 
 the colours are thus much impaired, which has led me to believe 
 that they need the contact of air to be rendered fast, if it be 
 permitted me to make use of this expression. 
 
 " The cloth, after the first exposure on the grass, is subjected 
 to a boil with cow dung. This operation has the advantage of 
 predisposing the cloth to become white, to heighten by its heat 
 the colours fixed by the mordants, and to render them more 
 durable under the action of the air, and of the solution of chloride 
 of potash. I have diluted the liquor very much, because I do 
 not then fear injury to any colour. I also pass through a colour 
 that has a black ground, or its derivative hues, with as much confi- 
 dence as those which have a mordant of alumina. The cloth, on 
 coming out of these immersions, sometimes appears not to be 
 sufiiciently bleached, but they are wonderfully disposed to re- 
 ceive the action of the atmospheric oxygen. I have found several 
 times, that on a piece of cloth being cut in two, when one-half 
 of it had an immersion, and the other none, the former bleached 
 more in two days on the field, than the latter in fifteen, 
 
 " When we are obliged to make the cloth undergo a second 
 boil, it is given on its return from the grass, immediately after 
 the first immersion in the liquor. By this second boil, we 
 succeed in reducing entirely into a species of soap, and removing 
 those spots of grease which I have mentioned above. This 
 likewise dissolves the colouring matters which have begun to 
 oxygenate. 
 
 ^^The cloths which come out of the weld, whether with a 
 yellow ground or a white, are first exposed for four or five days 
 on the grass, and are then, in like manner, subjected to an im- 
 mersion in the same liquor. The ground of the goods does not 
 appear at all bleached ; but as I have already stated, they are 
 disposed to receive the action of the oxygen, and at the end of 
 two or three days' exposure on the grass, they are of a superb 
 white. * When these cloths return for the last time from the field, 
 the yellow has a deep cast, which renders it somewhat dead. 
 
 This probably depends on the action of the oxygen of the 
 liquor, and of the atmosphere, which seems to have effected a 
 commencement of combustion. Its vivacity is easily restored, 
 by passing the cloths through a water very slightly acidulated 
 
ON BLEACHING BY CHLORINE. 
 
 153 
 
 with muriatic acid ; but the water must be no sourer than weak 
 lemonade. This operation has moreover the advantage of 
 carrying off the last portions of the yellow which may have re- 
 mained on the ground, or on the red ; and which, consequently, 
 would dull the lustre of both. This little manipulation, which 
 lasts, at farthest, five minutes, has also the advantage of rendering 
 the olive colours more of a greenish cast, tints which the dyer 
 has usually much difiiculty to obtain. 
 
 *^ I forgot to mention, that it is the strength of the colours 
 v/hich directs me as to the strength of the liquor. When the 
 colours are powerful, I contrive it so that the chlorine may pre- 
 dominate in the liquor ; on the contrary, if the colours be weak, 
 it is the alkali which ought to predominate. But if a saturated 
 chlorate of potash were made, it would no longer have the pro- 
 perty of bleaching. I suspected, that by passing cloths merely 
 into an alkaline water, it would dispose them equally to 
 whiten on the grass ; but experience has not realized this ex- 
 pectation. 
 
 I was a long while of obtaining complete success with the 
 solution " of chloride of potash, because I employed it in too 
 strong a dose, and, of consequence, I injured the colours. But 
 at present M. Oberkampf becomes every day more attached to 
 this new method, which is infinitely less costly than the old one, 
 and by which we obtain a more beautiful white, and far livelier 
 colours." 
 
 Widmer has, however, been obliged to abandon this process, 
 because it required to be conducted by himself, and because the 
 accidents, from inattention of workmen, rendered this method 
 too uncertain and too expensive. We know not whether a like 
 cause has made it be equally given up in the other manufactories, 
 or if they have found out some modifications which render the 
 process less uncertain ; but it should be retained for bleaching 
 cloths in the texture of which there is linen or cotton dyed with 
 some colour, which could not resist the too lively action of 
 chlorine, or even exposure on the grass. .(ISoTj; T.) 
 
 When we wish to deprive of colour a piece of cloth which has 
 some defect of dyeing or design, or whose colours have been ren- 
 dered dull by use, a ley should first be given to it, and then one 
 immersion, w^hich is commonly sufficient. It is now submitted to 
 a second ley, and passed through water acidulated with sulphuric 
 
154 
 
 BERTHOLLET ON DYEING. 
 
 acid. Without this last operation it would preserve a great part 
 of its mordant, and could not, for this reason, receive a new 
 impression or another design. 
 
 Chaptal made, at an early period, a happy application of the 
 properties of chlorine to the bleaching of paper, and the resto- 
 ration of engravings and books. We shall insert here the 
 description which he gave of his processes. 
 
 ^' Blotting paper put into a solution of chlorine, becomes 
 white in it, without being altered in its texture. The rags of 
 coarse and bad cloth, made use of in paper mills to form this 
 paper, are bleached by this solution, and then afford a paper of 
 superior quality. I have whitened by this process a hundred- 
 weight of paste intended to furnish blotting paper, and the in- 
 crease of value in the product was estimated at 25 per cent, 
 while the cost of the operation, rigorously calculated, did not 
 raise the expense above 7 per cent. 
 
 " The property which this solution possesses, of bleaching 
 paper, without affecting the texture, renders it valuable for re- 
 pairing old books, and smoked engravings. Engravings injured 
 to such a degree as to render the design difficult to be distin- 
 guished, have been repaired and refreshed in so astonishing a 
 manner as to appear new. Old books, soiled with that yellow 
 tint which time leaves on them, may be so restored as to make 
 us think they had just issued from the press. 
 
 Simple immersion in the chlorine, and a longer or shorter 
 continuance in it, according to the strength of the liquor, are 
 sufficient to bleach a print; but when a book is the object, other 
 precautions are necessary. As it is requisite that the acid should 
 moisten all the leaves, care must be taken to open the book well 
 up, and to make its boards rest on the edge of the vessel, so 
 that the paper alone dips into the liquor. Such leaves as are 
 sticking together, must be adroitly separated, that they may be 
 all equally impregnated. The liquor assumes a yellowish tint, 
 the paper becomes white, and after two or three hours the book 
 is withdrawn, in order to be plunged into pure water, which is 
 to be renewed from time to time to carry off any remaining 
 chlorine, along with its disagreeable smell. 
 
 This process has succeeded with me pretty well. It was the 
 first which I employed. But too frequently the colour of the 
 leaves was variegated ; sometimes several pages have not been at 
 
ON BLEACHING BY CHLORINE. 
 
 155 
 
 all bleached ; and I was forced to adopt a surer process. We 
 begin by unstitching the books and reducing them to leaves^ 
 These leaves are set in squares contrived in a shallow^ leaden tub, 
 with very thin plates, so that the leaves, laid flat, are separated 
 from one another by hardly perceptible intervals. The solution 
 is then poured gently in, making it fall on the sides of the tub ; 
 and to prevent the leaves from being deranged after the operation 
 is finished, the liquid is drawn ofl* by a stop-cock placed in the 
 bottom of the tub. This liquid is replaced by fresh water, which 
 washes the paper, and deprives it of the odour of the chlorine. 
 It is now hung up to dry, smoothed, and bound. I have restored 
 by this means several precious works, which were of no value 
 from their bad condition. The leaves may be set also upright 
 in the tub, a position which offers some advantages, as they are 
 less readily torn. For this purpose I constructed a wooden 
 frame, which I fixed down at the height which I thought suitable, 
 conformably to the height of the leaves that I wished to bleach. 
 This frame supported very thin slips of wood, leaving between 
 them intervals of half a line. I placed two leaves in each of 
 these intervals, and fastened them with two small wedges of 
 wood, which I pushed between the slips so as to press the leaves 
 against them. I give the more preference to this process, because, 
 when the operation is done, I lift out the frame with the leaves, 
 and plunge the whole into fresh water. By this operation, not 
 only books are restored, but the paper receives a degree of w^hite- 
 ness which it never had. This acid has also the advantage of 
 eflTacing spots of ink, which frequently depreciate books and 
 prints. This liquor does not attack the stains of grease or oil ; 
 but it has been long known, that a weak solution of potash 
 (caustic alkali) is a sure means of removing these marks. 
 
 When I have had to repair engravings in such bad condition 
 that they exhibited merely fragments pasted down on paper, I 
 was afraid of spoiling these fragments in the liquor, from the 
 loosening of the paste. In this case, I took the precaution of 
 enclosing the print in a large cylindrical jar, which I inverted 
 over a glass, into which I put the proper mixture for disen- 
 gaging chlorine gas. This aeriform substance filled the interior 
 of the jar, and acted on the print, consuming the filth, destroy- 
 ing the spots of ink, while the fragments remained glued, and 
 thus preserved their relative position." 
 
156 
 
 BERTHOLLET ON DYEING. 
 
 Loysel has prosecuted particularly the application of chlorine 
 to the bleaching of the paste of paper, because he was charged, 
 as member of the committee of assignats and coins, to inspect 
 this process, which was used for the assignat paper. We shall 
 present a summary of the observations which he published.* 
 
 By the ordinary processes, only a small portion of the rag can 
 furnish fine white paper; all the rest being appropriated to 
 papers of inferior quality. 
 
 The bleaching of the paste of paper, even when derived from 
 the most ordinary rags, can give it the quality of that of the 
 finest rags. 
 
 The tenacity of the paper depends on that of the fibres of 
 which it is fabricated. The rags of new cloth and cordage afford 
 a tougher paper than old rags. In the first rank are put rags of 
 fine new webs, either green, or bleached by the chlorine ; after 
 these come cordage and old rags. 
 
 The paper intended for bank-notes, or bills of commerce and 
 service, should be tough, to render it less apt to be torn than its 
 thinness would otherwise occasion. For this, it is right to employ 
 in whole, or in a great measure, materials of the first class. 
 
 The processes prescribed for the bleaching of threads and 
 cloths must be employed here ; that is to say, the substance 
 must be subjected to lixivia and immersions in the chlorine 
 liquor, when it is green (unbleached) ; but in operating upon 
 rags, it is sufficient to give them an immersion, and to pass them 
 afterwards into acidulated water. 
 
 An inconvenience has been experienced in operating upon the 
 paste of paper. It appeared very white, and yet it furnished an 
 unequal paper. It was because this paste subsided, so that the 
 leys and the liquors could hardly penetrate it. This incon- 
 venience was remedied by taking the matter in a medium state, 
 between that of a paste and of rags. This was secured by tear- 
 ing it asunder, under a first cylinder, thus destroying the texture 
 of the rags, and separating the fibres that composed the thread. 
 
 When a very tough paper is wanted, the green rags must be 
 submitted to the successive operations of bleaching. But when 
 whiteness is the principal object, the cost of the operation may 
 be consideriibly diminished, by leaving the rags for some time 
 
 Annales de chimie, torn, xxxix. 
 
ON BLEACHING BY CHLORINE. 
 
 157 
 
 in the fermenting tub, and washing them with care. After this, 
 one lixivium, two chlorine solutions, and acidulated water, will 
 be sufficient. 
 
 In this operation, the combination of chlorine and potash, dis- 
 solved in twenty times its weight of water, has been employed. 
 Undoubtedly, with a suitable apparatus, there might be used 
 without inconvenience simple solution of chlorine, or this 
 mingled with chalk. 
 
 Notwithstanding the increase of expense caused by this ad- 
 dition of alkali, Loysel shows, that the value added to the paper 
 by the process affords a considerable profit. 
 
 In treating of hemp and flax, we have described the processes 
 by which it has been attempted to give them the appearance of 
 cotton. Chlorine may be beneficially employed for this purpose. 
 
 Pajot des Charmes seems to have been the first who made this 
 application. "We shall recite the passage where he points it out.* 
 
 After having announced that the loose fibres bleach very 
 quickly, that is to say, at one or two immersions less than 
 average yarns, he adds : " It is to be remarked, that the tow of 
 flax or hemp proceeding from the fibres thus bleached, or 
 bleached separately, cut, if it be too long, and then carded, 
 singularly resembles the cotton of Siam, which is known to be 
 the shortest and the most common of the cottons of commerce. 
 When it is well carded, their difference cannot be discerned ; nor 
 is it possible to distinguish between them in spinning. I took 
 occasion to make some of it be woven at the end of a web : it 
 would have been taken for real cotton. I took occasion, in like 
 manner, to employ some of it for candle-wicks, without any 
 perceptible difference being found by the quantity of light or 
 the brightness. It would be very interesting, without doubt, 
 to know all the benefits which could be derived from this ap- 
 plication of chlorine to the arts of life." 
 
 Some time thereafter, but without knowing what has been 
 now detailed, a description of operations made in the laboratory 
 of the Polytechnic School, to accomplish the above object, was 
 published in its Journal. But Giobert has given us more ex- 
 tended and more exact observations, capable of directing this 
 new branch of art, which may probably acquire some importance. f 
 
 * L'art de blanchiment, page 106. 
 
 t Bibliot. ital. vol. ii. 
 
158 
 
 BERTHOLLET ON DYEING. 
 
 *^ Tlie process wlncli I have followed/* says he, is in general 
 the same as what Berthollet has just proposed, but with this dif- 
 ference, that in the trials made at the Polytechnic School, long- 
 fibres cut in fragments about 2J inches in length were employed ; 
 whereas, in all my attempts, and in my operations on the large 
 scale, I employed merely hemp tow of the worst quality, at three 
 sous the pound. 
 
 The process which Berthollet describes is the same, and 
 consists of the following operations : — ■ 
 
 The fibres are covered with water, and left in it for three or 
 four days ; after which they are boiled in simple water. 
 
 " 2. They are treated • with a ley, and then passed into the 
 chlorine ; operations which should be repeated alternately four 
 times. 
 
 "3. The fibres are now transferred into a bath of water, 
 charged with one-hundredth of sulphuric acid, and left in it for 
 half an hour. 
 
 " 4. The fibres, when taken out of this bath, are washed very 
 carefully, and plunged in soap water. They are then stretched 
 out, without wringing, on hurdles, and left to dry. 
 
 On this process Berthollet has remarked, 1. That it requires 
 only from five to six hours when small quantities are operated 
 on ; 2. That the loose fibres thus prepared, were capable of being 
 spun into very fine yarn of sufficient strength, although the fila- 
 ments had been cut very short in his trials ; 3. That the leys 
 should not be too strong, but that they should be boiling hot ; 
 4. That whether the finest flax or the coarsest hemp tow be em- 
 ployed, we obtain filaments equal in their fineness and whiteness ; 
 finally, he adds, that he believes by preventing too strong desic- 
 cation, the last immersion in soap water might be suppressed. 
 
 " The different observations which we are going to make on 
 this process, are the result of operations on a large scale, which 
 have brought into the market cottony cloth, and bales of this 
 hemp-cotton, which were not distinguishable from ordinary cot- 
 ton. From these results, various ameliorations have suggested 
 themselves. We shall follow in our operations the same order as 
 ought to be pursued in the practice of the above process. 
 
 " 1. Preliminary maceration of the fibres, (filasse.) 
 This operation is not absolutely necessary, audit may be sup- 
 plied by a good ley. But a previous maceration is more eco- 
 
ON BLEACHING BY CHLORINE. 
 
 159 
 
 nomlcal. Instead of pure water, old ley should be used in prefer- 
 ence ; but if there be none of this, plants, especially mucilagin- 
 ous ones, boiled in water with the addition of a little potash, afford 
 a better solvent. The steeping may also be continued longer, 
 even for fi^ e or six days, without risk in the hottest season, along 
 with the employment of alkalies that seem to favour the putrid 
 fermentation . In spring, autumn, and winter, it may be pro- 
 longed with advantage from seven to nine days. By this longer 
 maceration, the fibres become finer, that is to say, the filam.ents 
 come asunder, and the operations to which they are subjected in 
 the sequel have a greater effect. 
 
 When the fibres are well steeped, it is absolutely useless to 
 wash them with hot water, which only augments the cost. Cold 
 water is sufficient; but it must be in a stream, treading the 
 fibres with the feet till the water issues very clear, 
 
 '^2. Of the leys a7id immersions in solution of chlorine. 
 The leys might be dispensed with, by abandoning the fibres 
 to fermentation, in the manner above stated, after having passed 
 them through the chlorine ; but this practice is too tedious. 
 Nothing however occasions more inconvenience here than the lixi- 
 viation. Every filament of hemp or flax which has been lixivi- 
 ated thence derives stiffness, especially in its extremities, which 
 are to be joined continuously in the formation of yarn. Hence 
 its spinning becomes difficult, disagreeable, and unequal. The 
 spinster loses patience ; while the ends of the fibres do not twist 
 well together, their adhesion is imperfect, and by sliding on each 
 other, when the thread is slightly pulled, render it feebly tena- 
 cious. This may be regarded as a general fact. Yet leys can 
 hardly be dispensed with in a great manufacturing establishment 
 of hemp-cotton. For this reason, we must try to remedy these 
 inconveniences, which cannot be economically avoided. We 
 shall point out by and by two methods which succeed pretty 
 well. As to the leys, they ought not to be strong, as BerthoUet 
 rightly says ; but they should be very caustic, carefully prevent- 
 ing an excess of lime or of lime-water in the liquor ; for, in this 
 case, the fibres are too much weakened on one hand, and grow 
 stiff on the other. A ley is not too caustic, when on evaporating 
 a portion of the liquor, it is not disturbed, nor lets fall lime. 
 The ley-boil ought not to exceed three hours ; but after this the 
 greatest part of the hquor must be drawn off, and the fibres 
 
160 
 
 BERTHOLLET ON DYEING. 
 
 must be allowed to cool in a heap in the tub before washing 
 them. It is useful to place on the cloth which covers the fibres 
 large compressing weights. This repose of the fibres with little 
 liquor, has a more decided effect than the lixiviation ; and the 
 larger the quantity operated upon, the better does it answer. 
 
 It is useful to arrange the apparatus, so that the fibres can 
 be thereafter washed by a stream of water in the very tub in 
 which the lixiviation has taken place ; and it is in this same tub 
 that it is afterwards subjected to the chlorine, which ought to be 
 very weak. 
 
 3. Bath of sulphuric acid. 
 
 An acid bath is indispensable to give a shining whiteness to 
 the fibres. But these when bleached contain lime, which, 
 forming an insoluble salt with sulphuric acid, causes this to be 
 ill adapted for the purpose. The resulting sulphate of lime 
 adheres to the fibres, making them rigid ; nor is it possible to 
 carry it entirely away by washing. I have found, that by sub- 
 stituting muriatic acid for the sulphuric, the fibres have more 
 pliancy. Muriatic acid has a somewhat higher price in com- 
 merce ; but by making it within the manufactory, the expense 
 incurred by this substitution is not very considerable, and it 
 ought to be preferred. 
 " 4. Soaping. 
 
 ''The last operation is the soaping. This is indispensable; nor 
 ought any person to imagine he can do without it, for it is only 
 by the soaping that we succeed in thoroughly separating the 
 filaments. Besides, it is only by the soaping that we begin to 
 correct the rigidity which the ley gave to the fibres, and to give 
 them the pliancy of ordinary cotton. But to attain this end, 
 we must proceed in a different manner from that described by 
 BerthoUet. 
 
 " The fibres, on coming out of the preceding bath of muriatic 
 acid, instead of being washed with much care, as is stated in 
 BerthoUet's process, ought not to be washed at all. They 
 should be plunged, while still wet with the acid liquor, into the 
 hot soap-water, without fearing in the least the action of the 
 acid. The soap is decomposed by the acid, the resulting muriate 
 of soda is carried off by successive washings, and the oil of the 
 soap being absorbed by the fibres, gives them pliancy and soft- 
 ness. The filaments remain more delicate, and the successive 
 
ON BLEACHING BY CHLORINE. 
 
 161 
 
 operations of carding and spinning become consequently easier. 
 This is the first of the two methods which we announced for 
 removing from the fibres the stiffness which the alkalies of the 
 lixivia gave them. 
 
 5. To give pliancy to hemp-cotton. 
 " Notwithstanding the preceding processes, the cotton has not 
 yet got all the pliancy which is required. This will be com- 
 pletely given by the following operation. The dried fibres are 
 formed into large bales, and kept well packed up in a somewhat 
 damp place for two or three months. A species of fermentation 
 is by this means excited in the fibres, which gives them the de- 
 sired fineness, 
 
 " 6. To give the appearances of ordinary cotton to hemp-cotton. 
 The cotton procured from hemp by the preceding operations, 
 whatever care may have been bestowed, is always different from 
 ordinary cotton, and it is easy to distinguish it. The fibres 
 preserve a peculiar glitter very different from the dead white of 
 cotton. This lustre is sufficiently agreeable, and may possibly 
 be sought after for several objects of manufacture ; but it is not 
 a property of cotton, and must therefore be regarded as a defect 
 in our attempts to imitate ordinary cotton. I have discovered 
 only one method of remedying it, which consists in mixing by 
 the cards from 10 to 15 per cent, of ordinary cotton with that of 
 hemp. The cotton yarn made by this means is no longer dis^- 
 tinguishable from ordinary cotton yarn." 
 
SECTION IV. 
 
 OF DYEING OPERATIONS IN GENERAL. 
 CHAPTER I. 
 
 Of Dyehouses and the Manipulations of the Art of Dyeing. 
 
 If it may be regarded as a general principle^ that processes per- 
 formed in a great manufactory are more advantageous than those 
 which are insulated, {isoles,) since from the subdivision of labour 
 each vrorkman, occupied with a single object, acquires celerity 
 and perfection in his employment, and since every thing being 
 concatenated, each portion of the work is carried forward with- 
 out loss of time ; this principle should be applied to dyeing for 
 a peculiar reason, because the residuum of one process can fre- 
 quently serve for another. A bath which is found to be too 
 much exhausted for one colour, or even for what is called the 
 suites (gradations) of a colour, may either give a ground {footing) 
 to other dye-stuffs, or form a new bath, by mixing other ingre- 
 dients with it. Gall-nuts which have been employed for galling 
 silk, may still be useful for other operations on wool and cotton. 
 A great number of similar examples might be adduced. 
 
 By such considerations, it would be easy to prove how adverse 
 to the advances of the art were that division into the great and 
 little dije, that classification of silk, wool, and linen dyers, and 
 those regulations which prohibited a dyer of one class to keep 
 by him the ingredients assigned to another class. On the con- 
 trary, it seems proper to encourage large undertakings in dyeing ; 
 and those who are to direct them ought to lay down a plan of 
 the operations, so that there may be a relation between them all, 
 and that there may be no waste of ingredients, time, fuel, or 
 manual exertion. This arrangement should be made subservient 
 to the probable demfinds of commerce. 
 
OF DYEING OPERATIONS IN GENERAL. 
 
 163 
 
 A dye-house ought to be spacious, well lighted, and as near as 
 possible to a stream of water. It should be floored with lime 
 and cement ; it should be provided with ready outlets for the 
 water and the spent dye-baths ; and the whole so ordered as to 
 secure the utmost cleanliness. 
 
 The boilers, whose arrangement and size depend on the opera- 
 tions for which they are intended, should be made of copper or 
 brass; except for dyeing scarlet, for which it is better to employ 
 boilers of tin, as well as for other delicate colours, where a solu- 
 tion of tin is made use of. Brass is less liable to be attacked 
 by saline substances, and to stain the goods, than copper. We 
 shall see, however, that in many cases vessels of wood may be 
 substituted for metal boilers. It is of consequence to cleanse 
 the boilers well after every operation ; and such as are of great 
 capacity ought to have in their bottom a copper pipe, with a 
 stopcock at its outer end, which is opened when the baths are to 
 be emptied. 
 
 Above each boiler, holes are pierced in the chimney-piece or 
 wall, for resting the ends of poles, which serve to sustain the 
 hanks of vv^ool or silk while draining, or stuffs of which only 
 small portions are to be dyed. Thus also the bath liquor falls 
 back into the boiler. 
 
 For piece goods, a winch or reel is employed, the two ends of 
 which rest in two forks of iron, placed, at pleasure, in holes 
 bored in the curb that supports the edges of the coppers. 
 
 Several silk and cotton dyes, for which ebullition ought not to 
 be employed, are performed in long vessels of copper or wood^ 
 called troughs or backs, (barques ou haquets,) 
 
 As the most part of colours applied on silk are very delicate, 
 they require to be speedily dried to prevent their changing. For 
 this purpose a drying room is provided, which is heated by means 
 of a stove. The silk is stretched on a moveable pole called a 
 shaker, (hranloire,) which is hung up and agitated to accelerate 
 the desiccation. A drying room is also used for cotton cloths 
 which have been impregnated with a mordant. 
 
 Long details must be entered into, were we to describe every 
 thing which constitutes a dye-house. Inspection will instruct 
 much more speedily and exactly than a minute description of 
 these objects could do. The distribution of a dye-house ought 
 also to be subservient to the operations for which it is destined. 
 
 M 2 
 
164 
 
 BERTHOLLET ON DYEING 
 
 It should be so regulated, that these operations may follow one 
 another with the most advantage. 
 
 But it is desirable for the advancement of the art, as well as 
 that of the science itself, that a small place may be reserved, in 
 which the apparatus necessary for the common experiments of 
 chemistry and the trial of dyes may be collected. 
 
 The manipulations of dyeing are neither difficult nor com- 
 plex. Their object is, to impregnate the substance which we 
 wish to dye with the colouring particles held in solution in a 
 bath ; to make the agency of the air co-operate in the fixation of 
 the colouring particles, or in giving them lustre ; and to dis- 
 charge with care such as have not been fixed in the dyed stuff*. 
 We shall content ourselves with giving an account of the most 
 common manipulations, and of the denominations. 
 
 When one or more pieces of goods are to be dyed, the wdnch 
 (reel) is employed as above described. One end of the cloth is 
 wrapped round this reel, which being turned quickly, carries 
 round the whole piece in succession. The winch is next turned 
 in the opposite direction, in order that the part of the web which 
 was first plunged the former time, may be last at the second im- 
 mersion, whereby the dyeing is rendered as equable as possible. 
 If the piece of goods be long enough, or if several are to be 
 dyed of the same colour, their two extremities are stitched to- 
 gether, the winch is passed within, and then set on its forks. 
 
 When a solution of iron is employed, especially to give dif- 
 ferent shades to cotton goods, which are, for example, to be after- 
 wards passed through madder, we must prevent with great care 
 the progressive and unequal oxydation of the metal, according to 
 the directions of Chaptal on this subject,* which we shall take 
 occasion to recite. 
 
 If wool in the fleece is to be dyed, there is set over the boiler 
 a very broad kind of ladder, (called by English dyers a scraiv or 
 scray,) the bars of which are very close together. On this the 
 wool is laid to be drained and aired, as well as during the chang- 
 ing of the bath. 
 
 When the wool is in skeins, a rod is passed through each of 
 them, and the manipulation is the same as for silk and thread. 
 This manipulation consists in turning round in the bath the 
 
 * Memoires de Tinstit. ton), iii. 
 
OPERATIONS IN GENERAL. 
 
 165 
 
 hanks of silk, and the skeins of thread or woollen yarn on the 
 rods. This is called User, (shaking over,) and to the rod the 
 name lisoer (skein stick) is given. 
 
 After silks and yarns have been dyed, it is necessary to wring 
 them, in order to squeeze out the excess of the colouring parti- 
 cles. This operation is performed on a cylindrical piece of wood, 
 which is fixed at one end in a wall or to a post. It is called espart. 
 When this operation is repeated several times in succession, in 
 order to dry and give lustre, it is called ckevieller, (wringing by 
 the jack and pin.) 
 
 When a certain quantity of ingredients is added to a bath, it 
 is said that a brevet is given it ; and it is pallied {on le pallie) by 
 stirring it about and mixing it with a rake. 
 
 Sometimes a first colour is given in order to apply another 
 one above it, thus forming a compound colour. This is what is 
 called giving a ground, {donner un pied,) 
 
 Dishroder {rinse) is to wash silk from its dye, or its soap water, 
 in a small quantity of water, to which the name of disbrodure 
 (rinsing) is given. 
 
 When a stuff must be passed several times through the same 
 bath, the name passe {dip) is given to each particular operation. 
 
 A colour is rosed, when the yellow tone of a red colour is 
 changed into a shade which borders more on the crimson, or on 
 the colour of roses ; and a colour of a red-yellow is veered, {viree,) 
 when it is made to turn to a more decided red. 
 
 Although the manipulations of dyeing may not be very 
 various, and may appear very simple, they require peculiar care, 
 as well as a skilful eye, to judge of the qualities of the bath, 
 to raise and support the heat at the degree suited to each opera- 
 tion, to remove all the circumstances which might produce in- 
 equality in the colour, to judge with precision of the shades as 
 they come out of the bath, to match those which serve for pat- 
 terns, and to establish the desired relation between a succession 
 of hues. 
 
 • 
 
166 
 
 BERTHOLLET ON DYEING- 
 
 CHAPTER II. 
 
 Of Fuel. 
 
 As fuel is one of tlie chief articles of expense in dyeings it is 
 of great consequence to diminish its consumption as much as 
 possible, and to select the kind which may afford the desired ef- 
 fect with the least cost. It is proper, therefore, to be ac- 
 quainted with the philosophical principles of the production of 
 heat by combustion, the theory of which we owe chiefly to La- 
 voisier, as well as with the laws of its communication, in order 
 to be able to guide ourselves afterwards in their application 
 to the various circumstances that may occur. 
 
 When a body is burned, none of its ponderable principles are 
 destroyed. They previously formed a mere combination with 
 each other, and they are separated at the high temperature to 
 which they are exposed ; thus forming other combinations with 
 the oxygen with which they come into contact. Such of these 
 principles as cannot combine with it, that is to say, earth, certain 
 salts, and metallic ingredients, constitute the ashes. 
 
 The combinations formed, when the reciprocal action of the 
 oxygen gas and of the inflammable principles present in the 
 combustible becomes complete, are carbonic acid and water. 
 The proportion of these products varies, according to that of the 
 carbonaceous particles, and that of the hydrogen or base of in- 
 flammable air which exists in the combustible. Let us take 
 common charcoal for an example : — 
 
 If 100 parts of charcoal be burned in a glass bell, whose ori- 
 fice is plunged under mercury, there is found, after the combus- 
 tion, a weight of carbonic acid, equal to that of the charcoal 
 burned, and of the oxygen, which has now lost its properties. 
 This acid so formed, is composed, in 100 parts, of about 72 of 
 oxygen, and 28 of carbon. A little water is however generated, 
 which is taken up by the carbonic acid, or remains in the liquid 
 state. The unknown quantity of water prevents us from 
 regarding the determination now given as rigidly exact. 
 
 If alcohol or spirit of wine be burned, the result is different. 
 A weight of water is obtained exceeding that of the alcohol, 
 because the combustible principle of alcohol is chiefly hydrogen, 
 
OPERATIONS IN GENERAL. 
 
 167 
 
 which forms water by combining with oxygen. Oil also affords 
 much water, for the same reason. Charcoal and alcohol, or 
 rather ether, may be regarded as the two extremes, of which one 
 yields most carbonic acid, and the other most water ; and the 
 other combustibles may be viewed as mean terms, which approach 
 more or less to one of the two extremes, according to their 
 composition. 
 
 While the hydrogen and the carbon combine with the oxygen, 
 which forms a little less than the fourth part of the atmospheric 
 air, the caloric or principle of heat, which was combined with 
 the oxygen gas, giving it the elastic state, is in a great measure 
 disengaged. A portion of it is also probably disengaged from 
 the carbon, and especially from the hydrogen, but as the heat 
 produced when oxygen passes from one combination into another, 
 appears nearly proportional to the quantity retained, we depart 
 very little from the truth, in ascribing to it the whole heat dis- 
 engaged in combustion. Hence the heat produced in combus- 
 tion must be regarded as proportional to the quantity of water 
 and carbonic acid formed. We must however remark, that the 
 same quantity of oxygen which enters into combination with 
 hydrogen to form water, gives more heat than when it produces 
 carbonic acid with carbon. Hence combustibles which contain 
 much hydrogen, such as the oils, the resins, and pit coal, produce 
 in equal weight, and in circumstances equally favourable, more 
 effect than those w^hich owe their inflammability to carbon. 
 
 If the proportion of oxygen gas w^hich combines be insufficient, 
 (for saturation,) water and carbonic acid are not the sole pro- 
 ducts. A gaseous substance is formed, which may be regarded 
 as intermediate, being convertible into water and carbonic acid, 
 by means of a new proportion of oxygen. It has been named 
 m^carhuretted hydrogen^ in order to denote its composition.* 
 
 Q^tycarburetted hydrogen gas produces the blue flame over 
 furnaces, when its temperature is great enough to burn on 
 'passing into the atmosphere, where it finds the oxygen w^hich 
 was deficient in the furnace. 
 
 The conditions necessary to obtain the greatest effect of com- 
 bustion may be established on the foregoing considerations : 1 . 
 The quantity of oxygen ought to be sufficiently great for the 
 
 * Statique chim. torn. ii. 
 
168 
 
 BERTHOLLET ON DYEING 
 
 whole charcoal and hydrogen to enter into complete combination, 
 without producing di&ycarburetted hydrogen gas, and without 
 the combustibles escaping under the form of soot or smoke. 
 
 2. On the other hand, too great a proportion of air must be 
 avoided, for whatever is useless to the combustion, by abstracting 
 the heat disengaged from the fuel entering into combination, 
 would obstruct the elevation of temperature which is the object 
 of the combination. 
 
 3. The current should be rapid, that the heat may become 
 intense, and the temperature be suiRciently elevated for every 
 thing combustible to undergo the oxygenous combination. 
 
 In order to obtain the greatest effect of a combustible, none 
 of its particles capable of combining with oxygen should escape 
 the operation ; there should be neither soot nor smoke ; a 
 result obtained chiefly by the just proportion between the lower 
 opening of a furnace, its grate and chimmey. 
 
 The current of air which maintains combustion should be 
 easy ; but if the chimney is too large, the carbonic acid formed 
 is carried off with difficulty ; it remains too long in contact with 
 the combustible body, thereby opposing its combustion, while 
 an interior circulation is established, which brings back the cold 
 air towards the boiler, and pushes down the smoke. If the 
 chimney is not high' enough, a portion of the inflammable gas 
 escapes without burning, as well as the carbonaceous particles 
 that form the soot ; whence the effect of the combustible is 
 diminished. A higher column of air, rarefied, and rendered 
 lighter by heat, and next its condensation, as well as that of the 
 steam and carbonic acid, towards the top of the chimmey, would 
 have contributed to establish a more rapid aerial current. These 
 effects are peculiarly observed in reverberatory furnaces, in 
 which it is easy to verify the benefit of a chimney whose open- 
 ing is in due proportion to the size of the furnace, and whose 
 activity is increased by adding to the upper orifice a certain 
 extent of pipe. But too lofty a chimney is another inconveni- 
 ence to be avoided ; because the combustible parts which rise 
 have time to cool below the degree at which their combustion 
 takes place, forming merely a mass, which, with the carbonic 
 acid, opposes the circulation of air. 
 
 When a furnace is intended for a boiler or a series of boilers, 
 it must be so managed that the combustion is completely exe- 
 
OPERATIONS IN GENERAL. 
 
 169 
 
 cuted in front of the space in which the heat should be concen- 
 trated. In order to obtain this effect, it is proper that the 
 grate (hearth) in which the combustion takes place be in front of 
 the boiler, as Curadau recommends,* to whom we owe several 
 interesting observations on the regulation of furnaces. Since 
 the current of air is greatly more rapid when the furnace has a 
 high temperature, it is proper to diminish its column by means 
 of a register (damper) placed in the chimney. This register 
 serves likewise to intercept the current when the combustion is 
 finished, and when we wish to turn the remaining heat to account 
 by preventing it from being hurried off by the air. 
 
 The form of boilers is not unimportant towards obtaining the 
 greatest effect of fuel with the least cost and loss of time. It 
 should be subordinate, however, to the kind of operation that is 
 intended. We shall restrict ourselves to a few observations on 
 this subject. 
 
 The boilers should present the utmost possible surface to 
 the fire, and the heat should be applied to the greater part of 
 their outer surface by making the flame circulate round them. 
 Consequently, when they are intended for evaporation, distilla- 
 tion, or the heating of liquids, as leys for example, their width 
 should be greater than their height. Chaptal recommends, 
 moreover,f to construct them so that the bottom shall be convex 
 within. By this construction, the insoluble parts thrown off 
 upon the sides obstruct less the communication of the heat, 
 while the copper at the bottom is longer preserved. 
 
 It is not enough to pay attention to the combustion, but the 
 resulting heat must be distributed also, so as to produce most 
 advantageously the desired effects. 
 
 There are bodies which afford a ready passage to heat ; such, 
 in particular, are metallic substances. There are others, on the 
 contrary, which conduct it slowly and with difficulty ; such are 
 glass, pottery, bricks, woollen tissues, ashes, and especially char- 
 coal. The latter substances ought therefore to be made use of, 
 either directly or as envelopes, when it is desired to maintain the 
 temperature ; but metallic substances, when the heat is to be 
 diffused. The colours of the surfaces which disseminate or re- 
 ceive heat, may also possess an influence, according to the recent 
 
 * Annal. de chimie, torn. xlvi. 
 
 t Elcmcns de chimic, torn. i. 
 
170 
 
 BERTHOLLET ON DYEING 
 
 ingenious observations of Count Rumford ; but we are not yet 
 acquainted with their applications to the arts. 
 
 When the object is to form a solution, attention ought to be 
 paid to the effect that specific gravity may produce on the solu- 
 tion, or on the communication of the heat. 
 
 Every chemical combination, and that of caloric, which follows 
 its laws, are more speedily effected the more distant the point of 
 saturation. Hence, when a salt is dissolved at the bottom of 
 a liquid, which thus acquires a greater specific gravity by its 
 saturation, the successive layers of liquid are kept in their 
 respective position, and the most saturated remain at the bottom. 
 There is but a slight difference in saturation between each of 
 the layers, and thus the equilibrium of the whole is long of 
 being acquired. But if the salt is placed at the surface, the 
 portion of the liquid which becomes saturated falls to the 
 bottom in consequence of the specific gravity which it has 
 acquired, A current is established which continually brings the 
 least saturated liquid in contact with the salt, whence the solu- 
 tion is more quickly made, even without employing manual 
 agitation, which also acts by approximating the less saturated 
 portions to those which are completely so. 
 
 On these grounds we have recommended, after Welter, to 
 operate at the surface of the water the solution of potash 
 intended for leys. If a gaseous substance is to be dissolved, 
 the solution should, on the contrary, be effected in the lower 
 portion, in order to keep at a distance, by a less specific gravity, 
 the liquid which may be already saturated. 
 
 When water is converted into vapour by ebullition, it con- 
 tains a great deal of caloric in a latent state, which it gives up 
 when restored to the liquid condition. It results from the ex- 
 periments of the celebrated Watt, that this quantity would be 
 sufficient to raise the thermometer of Fahrenheit 900°, or the 
 centigrade thermometer 500° ; whence it follows, that one part 
 of steam at the temperature of ebullition can raise, by losing 
 itself the vaporous state, five parts of water from the tem- 
 perature of zero to the boiling point. 
 
 We thus perceive what advantages might be derived from the 
 steam that issues from boilers ; but the requisite manipulations 
 would seldom permit us to take the full benefit of it. 
 
 The celebrated Rumford, to whom we owe a great many 
 
OPERATIONS IN GENERAL. 
 
 171 
 
 ingenious observations on heat, its distribution, and the econo- 
 mical use of fuel, has pointed out modes of employing the 
 vapour of water for the communication of heat, w^hich may be 
 peculiarly advantageous in the art of dyeing. We shall give 
 some account of them. 
 
 The purpose of the apparatus is to generate steam, to be 
 carried into a vessel filled with any liquor which we may wish to 
 heat by its agency. A boiler must therefore be procured for 
 keeping up the ebullition of water. It ought to be spacious 
 enough to form a sufficient quantity of vapour ; and agreeably 
 to what has been described, it ought to have greater length than 
 height, and be so placed in the furnace as that most part of the 
 circumference shall be exposed to the current of flame. 
 
 This boiler must give origin to a large pipe, which serves as a 
 reservoir of steam. From this reservoir the conductor tubes 
 branch out, which are to transmit the vapour into the receivers 
 to be heated. These tubes should have a slight inclination, that 
 whatever vapour has resumed the liquid state may flow back 
 into the boiler. Into the end of each a vertical tube enters, 
 which carries the steam into the lower part of the receiver, and 
 which may be placed even in the inside of the receiver, or on its 
 outside surface. Above the level of the liquid the latter tube 
 should have an accurate stopcock, to prevent the liquid from 
 rushing back into the boiler when its steam is condensed by 
 cold, or has lost some of its elastic force. To prevent the acci- 
 dents, however, which might be occasioned, either by negligence 
 in shutting the stopcock, or, on the other hand, from so rapid 
 a formation of steam as might burst the apparatus, the boiler 
 ought to be provided with two valves, one intended to permit 
 the introduction of air when a vacuum is formed interiorly, the 
 other to give an outlet to the steam when its force becomes too 
 considerable. 
 
 To supply the steam-boiler with water, a reservoir is needed, 
 which communicates with it by means of a tube. This ought 
 to have a stopcock opening by means of a floater, when the 
 water of the boiler is diminished to a certain point. This tube 
 should be more or less elevated, according to the degree of tem- 
 perature which the steam is to possess ; for without sufficient 
 pressure, the vapour of water could not raise the water which 
 condenses it to the degree of ebullition. This circumstance 
 
173 
 
 BERTHOLLET ON DYEING 
 
 obliges us to give the boiler sufficient thickness to support the 
 expansive action of the steam at a temperature above the boiling 
 point. The w^ater contained in the reservoir may be prepared to 
 produce its effect, by previous heating through the prolongation 
 and distribution of the chimney of the furnace. 
 
 The whole outside of the apparatus must be preserved from 
 the loss of heat, by surrounding it with non-conducting sub- 
 stances. The author recommends to apply, by means of paste, 
 to the surface of the tubes, two or three coats of paper ; and 
 still better, hemp wrapped round in the direction of its fila- 
 ments. He has made curious experiments on the power which 
 this envelope gives. They are next surrounded with a wooden 
 case filled with charcoal dust, or pounded bricks. 
 
 In this way dye- baths may be heated, substituting wood for 
 metals, and heating several by means of a single furnace, which 
 may be at the same time portable. Different degrees of heat 
 are given, according to the dimensions of the tubes which con- 
 duct the vapour into each bath ; and an uniform temperature is 
 obtained. Lastly, the same method may be applied to the con- 
 struction of drying rooms and stoves, the condensed water being 
 reconducted into the boiler. 
 
 This method, which may be varied and multiplied in its appli-^ 
 cations, deserves peuliar attention, since English industry has 
 already turned it to several purposes. (Note U.) 
 
 Having thus given an idea of the phenomena of combustion, 
 and pointed out the means of profiting by the heat, it remains 
 to consider the diflTerent kinds of fuel, in reference to their 
 peculiar advantages. 
 
 To compare the eflfect of diff*erent combustibles, the process 
 described by Lavoisier may be employed.* It consists in burn- 
 ing each species of combustible in the same furnace, over which 
 a boiler is placed. Into this boiler an equal quantity of boiling 
 water is poured, and what has been evaporated is replaced by 
 letting in an equal weight of water at each operation. The 
 quantities of fuel required to evaporate the same quantity of 
 water are afterwards compared. It is obvious, that the qualities 
 of the combustibles are proportional to the quantities necessary 
 to produce the same eflPect. We have to compare, then, merely 
 
 * Mem. dc Tacad. l7ol. 
 
OPERATIONS IN GENERAL. 
 
 173 
 
 the quantities of each combustible employed in the evaporation, 
 with its respective prices, in order to determine what are the 
 most advantageous, and ought to be preferred. For this calcu- 
 lation, the weight or volume of each combustible may be made 
 use of indifferently, provided the price of the measure be known. 
 
 Instead of evaporating the same quantity of water, the desired 
 'result may be equally attained, by burning either the same 
 weight or the same measure of each kind of fuel, and comparing 
 thereafter the quantities of water evaporated. 
 
 As the bulks and weights of fuel should be compared with 
 the price, and as this price varies considerably in each country, 
 nothing of an absolute nature can be established concerning the 
 combustibles whose employment is the most profitable. In one 
 place it will be pit-coal ; in another, it will be wood or turf ; 
 the ratio of the prices may vary even in a short time, either by 
 opening a canal, by working a mine of pit-coal, or by the de- 
 struction of a forest. Several operators retain a prejudice 
 against the use of pit-coal ; but it is enough to observe, that 
 it is at present employed in so great a number of dye-houses, 
 without any inconvenience being experienced, that there can be 
 no doubt of its answering as a substitute for other fuel ; but as 
 in equal weight it yields much more heat, a little practice is 
 required in its management. 
 
 Pit-coal requires in the furnaces a construction somewhat dif- 
 ferent from that of the furnaces in which wood is used. As it 
 kindles with difficulty, it must be burned on a grate, which 
 affords passage to a current of air. Its qualities are moreover 
 very variable ; and the kind useful for one purpose is not fit for 
 another. Even should experience prove, that there is no ad- 
 vantage in our country in preferring pit-coal to wood, the use of 
 it should be begun ; because it is very probable, that the price 
 of wood will progressively increase, while, on the contrary, that 
 of pit-coal will fall, because its mining will be promoted by 
 being made with more intelligence than it has hitherto been in 
 France, and because it is to be hoped that canals for facilitating 
 its carriage will be multiplied. 
 
 Pit-coal is reduced into a true charcoal, by an operation analo- 
 gous to that by which wood is carbonized; an operation to which 
 the name of dessoufrage (cokeing) is given. This charred coal 
 affords a real advantage in the great furnaces, which serve to 
 
174 
 
 BERTHOLLET ON DYEING 
 
 smelt ores of iron, because pit-coal swells and agglutinates when 
 it is highly heated, thereby choking the furnaces ; inconveni- 
 ences which it no longer possesses after being coked. But for 
 other uses, it is preferable in its natural state ; because all the 
 bituminous oil burned off when it is reduced into charcoal is 
 wasted, without producing any effect ; and this operation re- 
 quires labour, which must be paid for. 
 
 Turf (peat) is also reduced to charcoal ; but this operation 
 presents a difficulty not easily overcome. When the recent 
 charcoal of turf is exposed to the air, it takes fire of itself, like 
 a pyrophorous ; an inconvenience which has, however, been 
 eventually obviated. 
 
 What has been said of pit-coal is applicable to turf. When 
 it can be employed in its natural state, it is more profitable to 
 do so than to incur the necessary expense of converting it into 
 charcoal, with the loss at the same time of the whole portion 
 which is consumed in this operation, and which could have 
 served to produce heat. 
 
 CHAPTER III. 
 
 Of the Means of ascertaining the Goodness of a Colour, {Dye.) 
 
 As colours differ greatly from one another, in their manner 
 of resisting the action of air, light, and other agents to which 
 they may be exposed ; and as in this circumstance an important 
 quality consists, of which the eye is no competent judge, 
 methods have been sought after for verifying their goodness by 
 easy and ready tests. 
 
 The purpose of these tests was to condemn the dyes which 
 could not resist them. It is truly important to protect com- 
 merce from the frauds which may impair the confidence of which 
 it stands in need ; and its interests would be promoted were we 
 able to assign the standard of manufactured productions like 
 that of gold and silver. But is it possible to find means suffi- 
 ciently certain, and at the same time expeditious, capable of 
 determining the permanency of a colour as well as its lustre, and 
 the other qualities which it is desired to possess ? Were these 
 means found out, could they be applied with equal success to the 
 
OPERATIONS IN GENERAL. 
 
 175 
 
 processes which an active industry discovers and introduces 
 every day ? 
 
 Much importance has been assigned to those tests formerly 
 called dehouillis, at a time when the processes of the arts were 
 subjected to regulations which sometimes directly counteracted 
 their advancement. By these, the workman in the fugitive dye 
 was punishable for employing certain ingredients capable of 
 giving fast colours. 
 
 These shackles were perhaps necessary to the establishment 
 and early progress of industry; but at the present day, they 
 are irreconcileable with its interests. With regard to goods 
 which are to be exported, it is possibly wrong to depend upon 
 such indications of manufactures as are exacted from the chefs 
 des pieces, (inspectors of dyes.) It is well known how much 
 our commerce has lost in the Levant by fraudulent fabrications 
 and dyes, under known appellations. 
 
 We shall not examine this question ; but we shall recapitu- 
 late what experience has taught concerning the methods which 
 may be employed, among which a dyer may select some profit- 
 able even for his own use. We are peculiarly induced to do this, 
 because the tests at first prescribed have been rectified by the 
 experiments of Dufay, a philosopher possessed of much sagacity. 
 We shall now, before transcribing the instruction founded on 
 his trials, present the history which Hellot has given of them, 
 with his judicious reflections. 
 
 Since it cannot be exactly ascertained, either by informa- 
 tions taken from different dyers, or by the perusal of ancient 
 regulations, what are the precise characteristics of the colours 
 of the good dye, (fast,) or those of the small dye, (fugitive,) it 
 became necessary, in order to acquire this knowledge, to take 
 the longest, the most difficult, but, at the same time, the most 
 secure, or to speak more properly, the only method on which it 
 was possible to depend with certainty. The late M. Dufay, of 
 the Royal Academy of Sciences, whom the government appointed 
 to labour towards the perfection of this art, caused woollens to 
 be dyed, under his eye, of all colours, and with all the ingre- 
 dients which are used in dyeing, both in the great dJ^A. little dye, 
 (in fast and fugitive colours.) He even brought from diflferent 
 provinces articles not employed at Paris. Lastly, he collected 
 most of the materials which he suspected to be made use of m 
 
176 
 
 BERTHOLLET ON DYEING 
 
 dyeing, and he tried a very great number of them, without 
 attending to the prejudices of dyers relative to their good 
 or bad qualities. 
 
 He began his trials on w^oollen yarns, but he found in the 
 sequel, that pieces of white cloth were more convenient for the 
 experiments which he had the intention of making. 
 
 In order to ascertain, among the different colours, those 
 which were solid, and those which were not so, and consequently 
 distinguish the fast from the fugitive dyes, he exposed to the sun 
 and the air during twelve days, patterns dyed by himself of all 
 those colours with whose composition he was acquainted. This 
 period seemed sufficient to prove them ; for good colours are 
 either not at all damaged, or very little, while the spurious are 
 in a great measure effaced. Hence, after twelve days' exposure 
 to the sun in summer, and to the moisture of the air during the 
 night, no doubt could remain about the class to which each 
 colour ought to be assigned, when it was tried in this manner. 
 
 " Nevertheless, one difficulty still remained ; for, not having 
 exposed all these colours to the air precisely at the same time, 
 or in the same season, some of them must have had more sun 
 than others, and must, of consequence, have lost more in the 
 same space of twelve days, than those which had been exposed 
 in gloomy weather, or when the days were shorter. But he ob- 
 viated this inconvenience, so as to leave no more difficulty or 
 doubt of the correctness of the test ; for he selected one of the 
 worst colours, that is to say, one of those on which the sun had 
 taken the most sensible effect during the space of twelve days. This 
 colour served him as a comparison piece for the whole course of 
 his experiments, and every time that he exposed the patterns to 
 the air, he annexed to them a piece of this same stuff. It was 
 now no longer the number of days to which he had respect, but 
 the colour which his comparison specimen assumed, and he kept 
 this exposed till it had lost as much as the piece which had been 
 exposed during twelve days of summer. As he always noted 
 the day on which he exposed his specimens, he had occasion to 
 observe, that in winter it was sufficient to leave them in the open 
 air four or five days longer, for them to lose as much colour as 
 they had done in summer. By pursuing this method, no scruples 
 remained in his mind about the accuracy of his experiments. 
 In this proof, by exposure to air and the rays of the sun, 
 
OPERATIONS IN GENERAL. 
 
 177 
 
 he had still another object, it was to find the delouilUs suitable 
 to each colour. The term dehouilli or debout, denotes the test 
 which is applied in order to learn if a stuff has a fast dye or 
 otherwise. A pattern is boiled with alum^ tartar, soap, vinegar, 
 lemon-juice, &c. ; and from the effect of these drugs on the 
 colour, its quality may be judged of. The dehouilUs practised 
 up to the year 1733 were so insufficient, that they could not 
 serve to M. Dufay as indications for finding out surer ones. 
 Indeed, some good colours were thus carried off, while the bad 
 ones were very little damaged. Hence he was obliged to fix on 
 several tests, each of which serves for a great number of colours. 
 The following is in a few words the path which he pursued in 
 order to find them. 
 
 After having observed the effect of the air on each colour, 
 whether good or bad, he tried on the same stuff different species 
 of dehouiUis, and he^kept by that which had the same effect on 
 this colour as the air had produced. Noting afterwards the 
 weight of the drugs, the quantity of water, the duration of the 
 trial, he was sure to produce on that colour an effect equal to 
 what the air ought to make on it, supposing that it had been 
 dyed in the same manner as his own had been, viz. according to 
 the method either of the fast or fancy dyers. Making thus a 
 survey of all the colours, and of all the ingredients used in 
 dyeing, he discovered a method, which may be regarded as accu- 
 rate, of knowing the good or bad quality of each colour, making 
 by the dehouilli a kind of analysis of its composition. We 
 cannot without injustice fail to acknowledge, that the means 
 which led M. Dufay to the discovery of these debouillis or tests 
 of colours, are very ingeniously imagined ; because the trial by 
 the air and sun cannot be put in practice in cases where it must 
 be decided on the spot, whether a stuff, exposed to sale, in a fair 
 or elsewhere, is of good dye, should its price correspond to this 
 quality. 
 
 " The debouillis of the new instruction, founded on the 
 memoirs of M. Dufay, cause the dye to lose in a few instants, if 
 it be spurious, all that it would lose on being exposed during 
 twelve or fifteen days to the air. But as general rules for similar 
 trials must be subject to many exceptions, which are either not 
 foreseen, or being foreseen, cannot be detailed, without running 
 
 N 
 
178 
 
 BERTHOLLET ON DYEING 
 
 the risk of causing confusion, or numberless subjects of contro- 
 versy, it follows that these rules, advanced perhaps as too general, 
 are also too severe in several cases, where light colours admit of 
 salts, or doses of salts, which will be less active than deeply 
 charged dyes, which may lose a considerable quantity of their 
 colouring ingredients in the active liquor of a particular debouilli, 
 without exhibiting any very sensible change. It would have been 
 requisite, therefore, to have prescribed a debouilli foic almost every 
 shade ; which was impossible, considering their infinite varieties. 
 Hence the air and the sun will be always the true tests ; and 
 whatever colour shall not suffer alteration during a certain time, 
 gr shall thus acquire what the dyers call a body, f fond, J must 
 be reputed of good dye, even though it should change consider- 
 ably in the debouillis prescribed by the new instruction. Scarlet 
 is an example of this. As soap carries off* this colour almost 
 entirely, it was subjected to the proof of alum; and when it is 
 made with cochineal alone, without a mixture of other ingre- 
 dients, it should assume, in a boiling-hot solution of alum, a 
 purple colour. If scarlet be exposed to the sun, however, it 
 loses a part of its vivacity, and becomes deeper ; but this shade 
 is not the one which alum gives it. Hence the debouillis, in 
 certain cases, cannot be substituted for the action of the air and 
 sun, at least with regard to parity of effect. 
 
 I have made with brazil wood, which, like all the other 
 woods charged with colour, is a false dye, a much more beautiful 
 red than the madder reds, and as lively as the reds made with the 
 grain of kermes. This red, from its peculiar preparation, of 
 which we shall speak in its place, remained exposed to the air 
 during the last two months of 1740, which were very rainy, and 
 during the first two of 1741. Notwithstanding the rain and 
 the bad weather, it stood ; and far from losing, it gained body, 
 (fond.) Yet this same red, so solid in the air, does not resist 
 the proof of tartar. Would it be right to proscribe it, be- 
 cause this salt destroys it ; or are the stuffs which we employ 
 for our clothing intended to be boiled with tartar, alum, 
 or soap ? I do not presume, however, to disapprove of the 
 trials by the debouillis. They are useful, because they are 
 speedy. But there are cases where they ought not to serve as 
 rules for pronouncing a sentence of confiscation, especially when 
 
OPERATIONS IN GENERAL. 
 
 179 
 
 they do not demonstrate that a colour, which ought to have 
 been made with drugs of the good dye, has been made with the 
 ingredients of the spurious dye'' 
 
 Instructions concerning the Dehouilli ( chemical trials ) of 
 Wool and Woollen Cloths, 
 
 Since it has been admitted, that the method prescribed for 
 the debouillis of dyes, by Article XXXVII. of the regulations 
 for dyers in the great and good tint, of cloths, serges, and other 
 woollen stuffs, of the month of August 1669, — by the Articles 
 CCXX. and following, of the general instruction for dyeing 
 of wool of all colours, and for the culture of drugs and ingre- 
 dients used in it, of March 1671, — is not sufRcient for judging 
 exactly of the goodness or spuriousness of several colours ; and 
 since this method may even sometimes lead into error, and give 
 rise to disputes, there have been made, by order of his Majesty, 
 different experiments on the wools destined for the fabrication 
 of tapestry, in order to learn the goodness of each colour and 
 its appropriate debouillis, 
 
 " To attain this object, fine wools have been dyed with all 
 kinds of colours, both in the good and little tint, and they have 
 been exposed to the air and the sun during a suitable period. 
 The good colours stood perfectly well, and the spurious were 
 more or less discharged according to the badness of their quality. 
 Since a colour should not be reputed good, unless inasmuch as 
 it resists the action of the air and the sun, this is a test which has 
 served as a rule for deciding on the goodness of the different 
 colours. 
 
 Different proofs by dehouilli have afterwards been made on 
 the same woollens, of which patterns had been exposed to the 
 sun and air. It has been observed at first, that the same ingre- 
 dients could not be employed indifferently in the debouillis of all 
 colours, because sometimes a colour found good by exposure to 
 air, was considerably altered by the debouilli, while a spurious 
 colour resisted the same debouilli. 
 
 "These different experiments have shown the inutility of 
 lemons, vinegar, soured waters, and strong waters, (aquafortis,) 
 from the impossibility of ascertaining the degree of acidity of 
 these liquors. It has therefore appeared, that the surest method 
 
180 
 
 BERTHOLLET ON DYEING 
 
 is to make use of ingredients, whose effect is always equal, along 
 with common water. 
 
 In pursuing this object, it has been judged necessary to 
 separate into three classes all the colours of which woollens can 
 be dyed, both in the fast and fading tint, and to define the in- 
 gredients that should be employed in the dehouillis of the 
 colours comprised in each of the three classes. 
 
 " The colours comprehended in the first class should be tested 
 with Roman alum ; those of the second, with white soap ; and 
 those of the third, with red tartar, (argal.) 
 
 " It is not enough for ascertaining the goodness of a colour 
 by the trial of the dehouilli^ to employ ingredients whose effect 
 may always be equal ; it is requisite, moreover, not only that 
 the duration of this operation be exactly determined, but even 
 that the quantity of the liquid be fixed ; because more or less 
 water diminishes or increases considerably the activity of the 
 ingredients which enter into it : hence the manner of proceeding 
 with the different dehouillis will be prescribed in the following 
 articles. 
 
 Article I. — The debouilli with Roman alum shall be made 
 in the following manner. 
 
 " Into an earthen or stoneware vessel, one pound of water 
 and half an ounce of alum shall be put : the vessel is to be set 
 on the fire, and when the water boils with large bubbles, there 
 shall be put into it the wool whose trial is to "be made, and it 
 shall be allowed to boil there for five minutes, after which it is 
 to be withdrawn and washed in cold water. The weight of the 
 sample ought to be about one gros, (nearly 60 grains troy.) 
 
 Article II. — When there are several samples of wool to be 
 tested together, it will be necessary to double the quantity of 
 water and alum, or even to treble it, which will in no respect 
 change the force and effect of the debouilli^ if the proportion of 
 water and alum be observed. 
 
 " Article III. — In order to make the effect of the debouilli 
 more certain, care must be taken not to test together wools of 
 different colours. 
 
 Article IV. — The debouilli with white soap shall be made in 
 the following manner. 
 
 Into a pound of water there shall be put only 120 grains of 
 white soap cut into small bits. The vessel being then set upon the 
 
OPERATIONS IN GENERAL. 
 
 181 
 
 fire, care shall be had to stir the water with a rod, so as to cause 
 the soap to melt properly. When it is melted, and the water 
 is boiling briskly, the sample of wool shall be introduced, and it 
 shall in like manner be made to boil for five minutes, counting 
 from the instant of its being put in, which shall be only when 
 the water boils with large bubbles. 
 
 Article V. — When several samples of wool are to be tested 
 together, the method prescribed in Article II. shall be observed; 
 that is to say, for every pound of water, 120 grains of soap 
 shall be taken. 
 
 " Article VI. — The dehouilli with red tartar shall be made 
 precisely in the same way, with the same doses, and in the same 
 proportions, as the debouilli with alum, observing to pulverize 
 the tartar well before putting it in the water, that it be entirely 
 dissolved before the samples of wool shall be put into it. 
 
 " Article VII, — The following colours shall be tested with 
 Roman alum ; namely, crimson of every shade, scarlet of 
 Venice, scarlet of a fire colour, scarlet of a cherry colour, and 
 its other shades ; violets and gridelins of every shade, purples, 
 pinks, jujubes^ pomegranate flowers, blues, slate-greys, lavender- 
 greys, violet-greys, wine-greys, and all other similar shades. 
 
 Article VIII. — If, contrary to the articles of regulation 
 concerning dyes, there has been employed, in the dyeing of fine 
 wools crimson, ingredients of the spurious tint, the infringement 
 will be easily recognised by the debouilli with alum, because it 
 renders fine crimson only a little deeper, that is to say, makes 
 it verge a little towards the gridelin hue ; but it destroys the 
 lightest shades of false crimson, rendering them of a very pale 
 flesh colour, and even blanching almost entirely the deep shades 
 of false crimson. Hence this debouilli is a certain means of 
 distinguishing the spurious crimson from the true. 
 
 " Article IX. — The scarlet of kermes or grain, commonly 
 called scarlet of Venice, is in no respect injured by this debouilli. 
 It causes scarlet of a flame colour, or of cochineal, to pass to a 
 purple hue, and strengthens the low shades, so that they get a 
 gridelin tinge ; but it carries off" almost the whole false colour 
 of brazil, and reduces it to an onion-skin hue. It has a still 
 more sensible effect on the deep shades of this false colour. 
 
 ''The same debouilli also carries off" almost entirely the 
 scarlet dyed with bourre and all its shades. 
 
182 
 
 BERTHOLLET ON DYEING 
 
 " Article X. — Although violet is not a simple colour, but is 
 formed of blue and red hues, it is, nevertheless, so important 
 as to merit a particular examination. The same debouilli with 
 Roman alum has almost no effect on the fine violet^ whereas it 
 greatly injures the spurious ; but it will be observed, that its 
 effect is not always to carry off equally a large portion of the 
 false violet hue, because this has sometimes a ground of pastel 
 or indigo. This ground being of good tint, is not carried off by 
 the debouilli ; but the redness is effaced, the brown shades be- 
 coming almost blue, and the pale ones of a disagreeable wine- 
 lees colour. 
 
 *^ Article XI. — With regard to half-fine violets, prohibited by 
 the present regulation, they shall be put in the class of spurious 
 violets ; nor do they stand the debouilli any better. 
 
 Article XII. — The fine gridelins will be distinguished in 
 the same manner from the spurious, but the difference is slight. 
 Gridelin of good tint loses only a little less than that of spurious 
 tint. 
 
 " Article XIII. — Fine purples re&ist the debouilli with alum 
 perfectly ; whereas the spurious lose the greatest part of their 
 colour. 
 
 Article XIV. — The colours of -pinks, jujubes, pomegranate- 
 fiower, will incline towards purple after the debouilli, if they 
 have been made with cochineal ; whereas they will become con- 
 siderably paler if fustet has been employed, the use of which is 
 prohibited. 
 
 " Article XV. — The blues of good tint will lose nothing in 
 the debouilli, whether the colour be pastel or indigo ; but those 
 of spurious tint will lose the greatest part of their colour. 
 
 Article XVI. — Slate-greys, lavender-greys, violet-greys, 
 (reddish greys ?) wine-greys, lose almost their whole colour if 
 they are of spurious tint, whereas they will stand perfectly if 
 they are of good tint. 
 
 Article XVII. — The following colours are to be tested 
 with white soap : namely, yellows, jonquilles, lemons, oranges, 
 and all the shades which are derived from yellow ; all the shades 
 of green, from yellow-green, or nascent green, (pomona-green,) 
 to cabbage or parrot-green ; madder-reds, cinnamon, snuff- 
 colour, and other similar hues. 
 
 Article XVIII. — This debouilli shows perfectly if the yel- 
 
OPERATIONS IN GENERAL. 
 
 183 
 
 lows and their derivative shades are of good or spurious tint ; 
 for it carries off the greatest part of their colour, if they are 
 made with Avignon berries, annotto, turmeric, fustet, or saffron, 
 the use of which is prohibited for the fine dyes ; but it does not 
 affect the yellow made with sarrette, (saw-wort,) genestrolle, 
 (dyer's broom,) fustic, (yellow-wood,) weld, and fenugreek.* 
 
 Article XIX. — The same debouilli will also show perfectly 
 well the goodness of greens; for those of spurious tint lose 
 almost all their colour, or become blue, if they have a ground 
 of pastel or indigo ; but those of good tint lose scarcely any of 
 their hue, and continue green. 
 
 Article XX. — The reds of pure madder lose nothing in the 
 soap debouilli, becoming, in consequence, only more beautiful ; 
 but if brazil wood is mixed with it, they lose some of their 
 colour in proportion to the quantity of the latter which has been 
 introduced. 
 
 Article XXI.^ — Cinnamon, snuff, and other similar colours, 
 are scarcely affected in the debouilli if they are of good tint ; 
 but they lose a great deal if annotto, fustet, or font de bourre 
 have been employed in it. 
 
 Article XXII.- — The debouilli made with alum would be of 
 no utility, and might lead even into error, with regard to several 
 colours of this second class ; for it does not injure fustet or 
 annotto, which do not however withstand the action of the air ; 
 and it carries off a portion of saw-wort, and dyer's broom, which 
 give, however, very good yellows and very good greens. 
 
 Article XXIII.— All the fawns, (duns,) or root colours shall 
 be tested with red tartar. Thus, all those colours are termed 
 which are not derived from the five primitive colours : such colours 
 are made with walnut peel, the root of the walnut tree, alder 
 tree bark, sumach, or roudoul, sanders and soot. Each of these 
 ingredients affords a great number of different shades, which are 
 all comprised under the general name dun, or root colour. 
 
 Article XXIV. — The ingredients enumerated in the pre- 
 ceding article are good, with the exception of sanders-wood and 
 
 * The botanical names of the above vegetable substances are as follows : Rhammis irifec- 
 torius^ (Fiench or Avignon berries ;) hioca orellana^ from which annotto ( rocou ) is made ; 
 curcuma longa^ turmeric ( terra merita ;) rhus cotinus^ fustet ; cracus saiitus^ saffron ; 
 serratula tinctoria^ saw-wort (genet;) genista tinctoria^ dyer's broom; moras tinctoria, 
 fustic; reseda /ew^eofo, weld ; irigonella/cBnugrceoimyfenxxgicQk. — T. 
 
184 
 
 BERTHOLLET ON DYEING 
 
 soot, which are a little less so, and which make woollens harsh 
 when too large a quantity is taken. Hence, all that the dehouilli 
 can teach concerning these kinds of colours is, whether they 
 have been surcharged with sanders-wood or soot, in which 
 case they lose considerably by the debouilli of tartar ; and 
 if they are made with other ingredients, or if there be but a 
 moderate quantity of sanders-wood or soot, they stand much 
 better. 
 
 Article XXV. — As black is the only colour which cannot 
 be comprehended in any of the three classes above stated, and 
 since it is necessary to make use of a debouilli much more active, 
 in order to learn whether wool has had the deep blue ground 
 conformably to regulation, the debouilli shall be made in the 
 following manner : — 
 
 One pound or one pint of water shall be taken : into this 
 shall be put one ounce of Roman alum, and as much pulverized 
 red tartar; the whole shall be made to boil, and a sample of 
 wool shall be introduced, which ought to be kept boiling briskly 
 during a quarter of an hour. It is to be thereafter washed in 
 fresh water, when it will be readily seen whether it has had 
 the proper blue ground ; for in this case the wool will remain of 
 a blue, nearly black ; if that be wanting, it will become con- 
 siderably grey. 
 
 Article XXVI. — As it is the practice to brown colours 
 sometimes with nut-galls and copperas, and as this operation, 
 called browning, {bruniture,) which should be permitted in the 
 good tint, may have a peculiar effect on the debouilli of these 
 colours, it will be observed, that although after the debouilli the 
 bath appears charged with the dye, because the browning has 
 been carried off, the wool will be not the less reputed of good tint, 
 if it has preserved its body. If on the contrary it loses this, it 
 will be declared of spurious tint. 
 
 Article XXVII. — Although the browning given with cop- 
 peras and nut-galls be of good tint, as it usually renders wool 
 harsh, it will be proper, as far as possible, to employ the indigo 
 or pastel vat in preference. 
 
 Article XXVIII. — The ordinary greys made with gall-nuts 
 and copperas should not be subjected to any trial of debouilli, 
 because these colours are of good tint, and are not made other- 
 wise. But it must be observed to gall them first, and to put 
 
OPERATIONS IN GENERAL. 
 
 185 
 
 the copperas into a second bath^ not nearly so hot as the firsts 
 because in this way they are finer and more fixed." 
 
 From the remarks of Hellot, it appears, that there has been 
 heretofore only one certain manner of ascertaining the perma- 
 nence of colours, namely, exposing them to the air, the sun, and 
 moisture for an adequate length of time. The debouillis, what- 
 ever care be taken to make a good choice of them, can be applied 
 only to determinate processes, such as those prescribed by the 
 regulations to which they were to be subjected. One of these 
 debouillis might, however, be excepted, that which is applied to 
 black, with a view of determining whether a blue ground has 
 been given, and whether it be strong enough to inspire confidence 
 in the goodness of the dye. 
 
 The chlorine affords a ready and easy means of determining 
 the degree of permanency of a colour. Hence, when a colour 
 is wished to be examined, a sample of the stuff* has only to be 
 put into the chlorine, along with a sample of a like colour 
 which had been dyed by a good process. The degree of resist- 
 ance which the colours of the two samples oppose, becomes the 
 measure of their goodness ; but as this liquor has a very lively 
 action on the colouring particles, it must be employed in a very 
 dilute state. This proof has the further advantage of making 
 known, pretty nearly, the shades and degradations through which 
 the stuff* is to pass, when it shall be altered by the air ; were it 
 required, however, to examine a stuff* juridically, the action of 
 chlorine could not be entirely trusted to ; nor would it be possi- 
 ble to pronounce with certainty, unless from the results aff*orded 
 by exposure to the air." 
 
 We extract this passage from the first edition of the Elements 
 of Dyeing, because Bancroft has objected to the testing of 
 colours by chlorine, as being entirely illusory and deceitful. We 
 persist in the opinion, that this easy test may be useful, espe- 
 cially in experiments on dyeing ; and that it rarely aff*ords false 
 indications when the precaution is taken which has been prescribed 
 of comparing two samples of the same colour, one of which 
 has a known durability; but we might be led into error, if 
 we wished to make the comparison of diff*erent colours with one 
 another. We should run the risk, for example, of ascribing to 
 yellows and fawns a greater comparative solidity than they 
 
186 
 
 BERTHOLLET ON DYEING 
 
 really possess in the air; because chlorine giving this hue to 
 substances of an animal nature, this effect might be easily con- 
 founded with the preservation of these colours. 
 
 For trying colours on silk, it is usually held satisfactory to 
 expose them to heat in acetic acid or in lemon juice. They are 
 regarded as permanent and fine if they resist this trial ; and in 
 fact, when woods or archil are simply made use of, the colour 
 passes to red by the action of the vegetable acid ; but if the 
 solution of tin has been used in dyeing with these substances, 
 the colour which had been prepared in an acid liquid is not 
 affected by the vegetable acids ; and in this case a colour might 
 be regarded as fine, which had cost much less for its preparation, 
 and which is easily altered. Hence, with regard to silk, chlorine 
 must be had recourse to, or above all, exposure to the air. 
 
 As to cotton and linen goods which are intended to be sub- 
 mitted to soap and leys, they must be tried by the action of 
 soap and alkalies. 
 
 There is another species of test which ought not to be 
 neglected ; the purpose of which is to determine the goodness 
 of colouring substances of the same nature. The look, and 
 some other criteria, are generally trusted to ; but they afford 
 only uncertain estimates, and can furnish no scale of comparative 
 value. Chlorine possesses this property in a degree which leaves 
 nothing to be desired; because, whenever indigo is compared 
 with indigo, the nature of the colouring particles is the same, 
 or nearly the same, and no foreign affinity prevents the action of 
 chlorine from determining the proportional quantity of colouring 
 matter. 
 
 If an inconsiderable difference existed between the nature of 
 the colouring particles that were assumed as the same, it is very 
 probable that the action of chlorine would be, moreover, a 
 measure of their respective goodness. 
 
 Whenever, therefore, it is wished to compare two or several 
 substances which have the same colour, and to determine their 
 quality or value in reference to the purpose for which they are 
 intended, it is necessary merely to compare the quantities of 
 the same chlorine requisite to reduce an equal weight of each of 
 these substances to the same degree of destruction ; then the 
 qualities of these substances, or the quantity of colouring par- 
 ticles which they contain^ are in direct proportion to the measures 
 
OPERATIONS IN GENERAL. 
 
 187 
 
 of liquid which have been necessary to produce the same effect 
 upon each. For making this valuation, the colouring particles 
 of each substance ought to have been dissolved in a proper 
 liquid, and every substance of the comparative operation should 
 be equal. 
 
 If it is desired to compare several species of indigo, for exam- 
 ple, an equal weight of each is taken, and pulverized with care ; 
 they are then put into separate matrasses, with eight times their 
 weight of concentrated sulphuric acid. The matrasses are kept 
 in a heat of from 100° to 120° Fahr. for a few hours. Each 
 solution is afterwards diluted with the same quantity of water. 
 The liquids are filtered ; and the residua collected on the filters 
 being bruised in a glass mortar, with the addition of a little 
 sulphuric acid, they are left again to digest. These last solu- 
 tions are diluted with an equul quantity of water, then filtered, 
 and added each to its correspondent liquor. Lastly, into each 
 solution there is poured the quantity of liquid chlorine which is 
 requisite to destroy its colour, or rather to bring it to the same 
 shade of yellow. The qualities of the different species of indigo 
 are proportional to the measures of chlorine which was needed 
 to destroy their colour. 
 
 The tests for colouring particles soluble in water are much 
 more simple. After exhausting them, equal volumes of the 
 decoctions of the same weight of these substances are taken; 
 and then the quantities of chlorine necessary to bring them to 
 the same tint, are compared. 
 
SECTION V. 
 
 OF THE CHEMICAL AGENTS EMPLOYED IN DYEING. 
 
 In order to form an exact idea of the effects produced by the 
 substances employed in dyeing, their chemical properties must 
 be known, for these effects are merely consequences in par- 
 ticular cases. 
 
 We shall here present a summary view of the history and 
 properties of the substances most commonly used in dyeing, and 
 in the arts immediately related to it, stating, at the same time, 
 the general principles which may serve to explain their action. 
 
 We shall so arrange it, that those persons who have but a 
 limited acquaintance with chemistry, may find in this summary 
 the most useful notions, and that those who are further advanced 
 in the speculations of the science, may perceive the relations 
 connecting the particular phenomena to the general laws of 
 combination. 
 
 CHAPTER I. 
 Of the Jlcids, 
 
 The acids are recognised by their taste, their property of red- 
 dening the blue colour of several vegetables, such as that of litmus, 
 flowers of mallow, and violets, and by the effervescence which 
 they produce when mixed with mild calcareous earth and 
 alkalies. But these characters being merely a consequence of 
 their action, afford no idea of the properties by which they act 
 in the production of these very effects. 
 
 All the chemical properties of a substance depend on its 
 affinities to other substances ; but the effects of an affinity 
 
OF THE CHEMICAL AGENTS. 
 
 189 
 
 differ according to the physical dispositions of the substance 
 which exercises it, and of that on which it exerts its action. 
 The latter acts reciprocally on the former by its affinity, and 
 according to its physical dispositions. 
 
 The affinity by which two substances form a combination, in 
 which their properties have become more or less latent, produces 
 an effect dependent not only on its energy, but also on the 
 quantity of the substance exercising it. 
 
 In proportion as an affinity is satisfied, or as it experiences 
 saturation, its energy diminishes ; and when it is exactly counter- 
 balanced by the action of the substance that produces saturation, 
 the combination is neutral, or affords no farther indication of 
 the action peculiar to each of the elements which compose it. 
 
 The substances which produce in the highest degree the 
 saturation of the characteristic properties of the acids, and 
 which make them entirely disappear, are the alkalies, whose 
 properties experience, on their part, a like saturation. The 
 reciprocal action of these substances is thereby capable of even 
 disclosing the laws of chemical action, or of the tendency to 
 combination. 
 
 The acidity, or the power of combination of the different 
 acids with the alkahes, should therefore be proportional to the 
 quantity of the same alkali which they can saturate, or to their 
 capacity of saturation ; and reciprocally. 
 
 The physical qualities of the substances diversify the effects of 
 affinity. We understand here by physical qualities, all such as 
 do not depend on the tendency of a substance to form with 
 another a combination whose weight results from the two, 
 although some of these qualities be still derived from affinity ; 
 for example, solidity, which is a result of the reciprocal action 
 of the molecules of any one substance, whether simple or com- 
 pound. 
 
 Those physical qualities which change the results of affinity 
 are principally solidity, liquidity^ expansibility, or the disposi- 
 tion to assume or retain these different states. They do not 
 disappear by the action of affinity ; they thence experience no 
 saturation ; but they receive modifications from it, while they 
 themselves act as forces which contribute to the immediate effect 
 of affinity, or which are opposed to it. 
 
 The disposition to solidity determines the combinations which 
 
190 
 
 BERTHOLLET ON DYEING. 
 
 precipitate when an acid is mixed with an alkaline solution, and 
 similarly when several acids and several alkalies exercise a 
 reciprocal action ; whence proceed the precipitates or the salts 
 which separate by crystallization. This disposition is increased 
 by the approximation or condensation which affinity produces ; 
 and the compound which separates in consequence, readily 
 acquires an excess of the element in which this quality predomi- 
 nates. Hence two substances possessing liquidity, may form 
 an insoluble combination, or a salt less soluble ; and the com- 
 pound which separates may preserve an excess of acid or of 
 alkali, according as one or other of these has a greater disposi- 
 tion to solidity. Thus may be explained the precipitations pro- 
 duced by the acids or the alkalies, and the formation of acid or 
 alkaline salts. 
 
 Heat, whose function it is to dilate bodies, and separate their 
 particles, diminishes insolubility, and increases the tendency to 
 the liquid state. It augments especially the disposition to elas- 
 ticity ; and as the latter exercises a force contrary to the 
 tendency to combination of a fixed substance, with a substance 
 possessing the elastic condition, it is obvious, that by increasing 
 it to a sufiicient degree, the whole effect of the tendency to 
 combination may be destroyed. If several acids and several 
 bases exert a reciprocal action by the same means, the most 
 volatile elements will be determined to form a compound, which 
 will separate by volatilization from that contracted by the more 
 fixed elements. 
 
 The acids act, therefore, by their affinity or tendency to com- 
 bination, in the ratio of their capacity of saturation ; and the 
 physical qualities of their compounds depend on those of the 
 elements composing them, and of the modifications produced 
 on them by the condensation due to the combination, or the 
 expansion which is the effect of heat. 
 
 When an acid acts on a neutral combination, the base divides 
 its action in the ratio of the quantity of the two acids, and of 
 the energy of their affinity ; but the result depends principally 
 on the dispositions to the solid, liquid, or elastic state of the 
 elements which are in action. The capacity of saturation of 
 two acids usually differs too little to produce an effect capable 
 of counterbalancing one of the causes just designated. 
 
 Hence, when an acid which has a certain fixity (sulphuric 
 
OF THE CHEMICAL AGENTS. 
 
 191 
 
 acicl for instance) acts on a muriate whose acid is volatile, the 
 latter ought to be expelled, especially by increasing its elasticity 
 with heat, although it has a greater capacity of saturation for 
 soda. 
 
 From the physical qualities of two substances which enter 
 into combination, may therefore be inferred those which subse- 
 quently exist in the compound itself ; and as the same causes 
 act when there is a rivalship of different acids for one base, or 
 of different bases for one acid, or of several acids for several 
 alkalies, there will be found, in considering the qualities of each 
 of these substances, the reason of the peculiar compounds which 
 separate by precipitation or volatilization, or which remain 
 liquid, and of the changes that different temperatures may pro- 
 duce on these combinations. 
 
 The acids and alkalies exercise a pretty powerful action on 
 most of the colouring substances. We have shown that the 
 results of this action are, more soluble compounds with such of 
 these substances as have in themselves greater disposition to 
 solubility. Thus the acids act in general. But we have re- 
 marked, that the crystals of tartar retain the colouring matter 
 of cochineal. Potash, soda, and ammonia, act also as solvents ; 
 while the slightly soluble alkalies, lime, barytes, and strontian, 
 form insoluble compounds. Few experiments have hitherto 
 been made in this point of view. 
 
 Some acids act on colouring substances by the oxygen which 
 enters into combination with them, or with their elements. 
 This subject has been already sufficiently discussed. 
 
 Neutral salts possess but a feeble action on colouring par- 
 ticles ; they change their solubility little ; and they produce but 
 a moderate effect on their shades. Sometimes, however, this 
 effect is taken advantage of when they are employed as alterants. 
 
 I. — Of Sulphuric Acid. 
 
 Pure sulphuric acid is without smell or colour, transparent as 
 water ; and when concentrated it is of an unctuosity approach- 
 ing to that of oil. To denote this unctuosity, it was called oil 
 of vitriol, a designation which may lead to dangerous mistakes 
 concerning its nature. 
 
 This acid was at first extracted from the sulphate of iron, or 
 
192 BERTHOLLET ON DYEING. 
 
 vitriol of iron, whence its old name of vitriolic acid. At the 
 present day, nearly the whole that is employed in the arts is ob- 
 tained from sulphur, by a much less expensive process. It is the 
 result of the combustion of sulphur, which, by burning, com- 
 bines with the oxygen present in the atmospheric air, and in the 
 nitre which is added to a certain quantity of the sulphur before 
 setting it on fire. The latter, however, seems to be especially 
 useful for exciting the high temperature necessary to the formation 
 of sulphuric acid ; for it has to enter into the composition of the 
 sulphate of potash produced. The mixture of sulphur and nitre 
 is kindled, audits vapours are received in a leaden chamber, whose 
 bottom is covered with a stratum of water. The vapours which 
 collect and unite to the water, form the sulphuric acid, which should 
 be considered as sulphur completely burned. (Note V.) 
 
 The sulphuric acid, as it comes out of the leaden chamber, is 
 not in a concentrated state, but is mixed with a certain quantity 
 of redundant water. It retains the odour of sulphurous acid, 
 wh ic differs from sulphuric acid in its composition ; as the 
 former is not sufficiently saturated with oxygen, while this 
 element is less condensed in it. It retains also a little nitrous 
 acid, proceeding from the nitre mixed with the sulphur. If it 
 be left for some time exposed to the air, the smell of sulphurous 
 acid is dissipated. But another method is employed to deprive 
 it of odour, and at the same time of a portion of its redundant 
 water. It is evaporated with heat. 
 
 Only a very small quantity of vegetable or animal substance 
 is required to give this acid a brown colour ; and the acid of 
 commerce has rarely a very clear colour. But this limpidity 
 may be obtained by boiling it for some time in a retort. By 
 this operation it is deprived at once of a portion of nitric acid 
 usually present, and of a portion of water which it had retained. 
 It becomes white and transparent ; the concentration being the 
 greater the more water has been driven over by the distillation. 
 To procure it of thorough purity, we must, after having sepa- 
 rated the first portion, which is impure, and feebly acid, continue 
 the distillation till no more liquid remains in the retort. The 
 residuum consists of a little alkali derived from the nitre, which 
 remains combined with an excess of sulphuric acid ; a combination 
 named acidulous sulphate of potash; sometimes a little sulphate 
 of lead is also left. 
 
OF THE CIIEMTCAL AGENTS. 
 
 193 
 
 For this rectification, there must be selected a retort not very 
 lofty, which is to be well secured in an open furnace, or placed 
 in a sand bath, so that the movements occasioned by the ebulli- 
 tion of the acid may not break it. 
 
 Sulphuric acid powerfully attracts the humidity of the air. 
 To preserve it concentrated, it must therefore be kept in glass 
 vessels carefully stopped. 
 
 When it is mixed with water, a great heat is produced. 
 Hence this mixture should be gradually made, to prevent the 
 fracture of the vessel, an accident which is avoided by making 
 the mixture in a leaden vessel. In order to effect a complete 
 mixture, the liquid must be long stirred with a glass rod ; for 
 notwithstanding the great affinity of this acid for water, the 
 difference of their specific gravities opposes their combination. 
 
 The difference of volatility, and the mutual action of the 
 sulphuric acid and water, explain the effects which arise from 
 this action in different circumstances. * It attracts water, causing 
 the moisture w^hich is held dissolved in the atmospheric air to 
 lose its elasticity ; and it is only by increasing the elastic dispo- 
 sition of the latter by heat, that it can be again separated. But 
 to reduce the water into vapour, a greater heat is required than 
 if it were not retained by the affinity of the acid ; a heat which 
 must be augmented according as the proportion of water dimi- 
 nishes. Lastly, the acid passes over itself in the distillation 
 along with a decreasing proportion of water, which must in its 
 turn promote this effect by reason of its volatility. 
 
 The fixity of this acid, its concentration, the property it has 
 of freezing, show that it must carry into its combinations a 
 great disposition to insolubility, when the base has the same 
 disposition. Hence it produces slightly soluble combinations 
 with lime, barytes, strontian, and several metallic oxydes. 
 
 The condensation of sulphuric acid proves that the combi- 
 nation of oxygen with sulphur is here very intimate, and conse- 
 quently it should not easily part with its oxygen. For this 
 reason, it produces no decomposition of the colouring substances 
 which it dissolves, unless this solution be exposed to a strong 
 heat. Then the hydrogen and the carbon of these substances 
 may combine, particularly with a portion of the oxygen of 
 the acid, which is thereby brought to the state of sulphurous 
 acid, which, being volatile, escapes in the progress of the 
 
 o 
 
194 
 
 BERTII0LL5 T ON DYF.llSG. 
 
 decomposition. As the oxygen is endowed with greater elasticity 
 in the latter acid, it abandons the sulphur more easily, though 
 this substance be in larger proportion than in sulphuric acid. 
 
 Sulphurous acid, therefore, acts on colouring substances, by 
 giving up oxygen to them less easily and less efficaciously than 
 nitric acid, or chlorine ; but in other circumstances, it may 
 carry oft' even oxygen, as it does on being mixed with chlorine. 
 
 Highly concentrated sulphuric acid has a specific gravity, 
 nearly double of that of distilled water. When it is weak, that 
 is, diluted with a great deal of water, the fallacious name of 
 spirit of vitriol has been given to it. 
 
 In order to obtain uniform effects, it is right to employ for 
 the same operations, a sulphuric acid which has always the same 
 degree of concentration. Its specific gravity must be therefore 
 ascertained, which is commonly done by means of the areometer 
 of Baume. For this purpose, the acid is put into a glass cy- 
 linder, and the areometer for salts is plunged into it. The 
 denser the liquid, the less the areometer sinks, and the degree 
 on that part of its scale which rests at the surface of the liquid, 
 indicates its concentration. Sulphuric acid is regarded as highly 
 concentrated when it is at 66° of this areometer. (Sp. gr. 1.848, 
 or 166° Tw.) 
 
 Hitherto sulphuric acid has been used in dyeing, principally 
 for making solutions of indigo ; for which purpose it must be 
 strongly concentrated, and very pure. But a great deal of it is 
 employed for preparing cotton goods intended to be printed, as 
 well as for the bleaching of cloths and yarns, whether by chlo- 
 rine, or by exposure on the grass. 
 
 These latter purposes do not require a concentrated sulphuric 
 acid. If therefore a manufactory of sulphuric acid exist in the 
 neighbourhood, it is more advantageous to purchase it before 
 being concentrated, and thus avoid the cost of this operation. But 
 if such an establishment be at a distance, the diminution of the 
 expense of carriage may render it more profitable to purchase it 
 in a state of concentration, than if it were diluted with a certain 
 quantity of water. 
 
 II. — Of Nitric or Nitrous Acid. 
 Chemists have given different names to this acid, according 
 
OF THE CHEMICAL AGENTS. 
 
 195 
 
 to the processes by which it is extracted from nitre. What is 
 obtained from a mixture of nitre and clay is called aquafortis ; 
 that procured from nitre distilled with sulphate of iron, spirit of 
 nitre ; and the fuming nitrous acid is derived from a mixture of 
 nitre and sulphuric acid. These distinctions are not made in 
 commerce, but the name aquafortis is usually given to this acid, 
 whatever process may have been employed. In fact, it is always 
 the same acid, differing only in the degree of concentration, and 
 in colour. It is sometimes white, sometimes red and fuming. 
 The colour and property of fuming, are owing to the nitrous 
 gas which it holds in solution, as we shall explain hereafter. 
 
 If the reddest acid be exposed to a sufficient heat, the nitrous 
 gas is disengaged, and the acid remains white. In this state it 
 is called nitric acid, while the name nitrous is given to the red 
 acid. 
 
 As there is no great consumption of this acid in dyehouses, 
 and as these are often at a great distance froxn the places where 
 the acid is manufactured, it may often be useful and economical 
 to prepare it one's self. This motive induces us to describe here 
 the process by which it is extracted from nitre by means of 
 sulphuric acid. 
 
 Pure nitre, called nitre of the third boiling, being the result 
 of a third crystallization, is pulverized, and put into a retort 
 with half its weight of concentrated sulphuric acid, or a little 
 more, in such a manner that one-half of the capacity of the 
 retort remains empty, in order that the materials in boiling up 
 shall not pass over into the receiver. To the neck of the retort 
 a bent tube is adapted, whose orifice must be sufficiently large 
 to embrace and receive it. The other end of this tube, which 
 ought to have a much smaller diameter, is introduced, through 
 a cork, into a receiver with a double neck. To the other open- 
 ing of this receiver a tube is also adapted, which terminates in a 
 little water contained in a matrass. The communication of the 
 retort with the first tube, and the openings of the first receiver, 
 must be carefully coated and covered with fat lute, consisting of 
 pulverized white clay, boiled linseed oil, and a little litharge. 
 This lute must be beaten for a long time in a mortar, to render 
 it smooth and ductile. The lutings must be wrapped round 
 with strips of linen cloth soaked with white of egg, and be dusted 
 with powdered quick-lime. It is of advantage to have a tubu- 
 
 o 2 
 
196 
 
 BERTHOLLET ON DYEING. 
 
 lated retort to prepare the whole apparatus, before introducing 
 the sulphuric acid into it by the tubulure, and even to dilute 
 the sulphuric acid previously with a certain quantity of water. 
 
 The second matrass should maintain a free communication 
 with the air, that the vapours incondensable in water may 
 escape. The quantity of water put into the second vessel must 
 bear a proportion to the quantities of materials operated upon. 
 The fire must be nicely tempered at tlie beginning, and be 
 gradually augmented up to the end of the operation. The acid 
 which is obtained in the first receiver is highly concentrated ; 
 that which is in the second is weakened by the water put into it 
 for condensing the vapours. The colour of the latter acid is 
 blue or green ; colours owing to the nitrous gas ; their diversity 
 depending on the proportion of water. Thus, if a little water 
 be added to that which is green, it becomes blue ; and when the 
 gas is expelled by heat, the liquor remains colourless. The 
 acid of the second matrass is always pure, but that of the first 
 contains sometimes a little sulphuric acid, arising from the 
 heat not being rightly regulated at the commencement of the 
 operation. For, when tempered with discretion, a perfectly 
 pure acid may be obtained, if the sulphuric acid does not 
 exceed the half of the weight of the nitre. 
 
 It is of importance to test the nitric acid of commerce, be- 
 cause a considerable quantity of sulphuric acid is frequently 
 present in it, whether it may have come over in a distillation 
 negligently conducted, or have been added to the nitric acid in 
 order to augment its specific gravity. For testing it, we dilute 
 it with an equal weight of distilled water, and then drop in a 
 little of the solution of nitrate of barytes. If the acid which we 
 try contain sulphuric acid, a precipitate takes place, because this 
 acid forms an insoluble salt with barytes. Nitric acid may 
 likewise contain some muriatic acid, proceeding from the sea- 
 salt which might exist in the nitre employed. This mixture 
 cannot be prejudicial to the operation of dyeing. If, however, 
 we desire to discover it, the acid must in like manner be mixed 
 with distilled water, and a nitric solution of silver is to be then 
 poured into it. A precipitate occurs if muriatic acid be present. 
 
 To deprive the nitric acid of the sulphuric, it must be re- 
 distilled from a little nitre, or solution of lead may be added to 
 it, which produces a precipitate that is to be separated. After 
 
OF THE CHEMICAL AGENTS. 
 
 197 
 
 this, the acid is submitted to a new distillation. By this 
 operation the nitric acid is separated, not only from the sul- 
 phuric acid, but also from the muriatic which it may con- 
 tain. To accomplish the latter object entirely, the first portion 
 of liquid that comes over must be removed, because it may 
 contain some chlorine. 
 
 Nitric acid may serve for several metallic solutions, whose 
 use as mordants may be various, but its principal employment 
 is for aqua regia, or nitro-muriatic acid, which shall be treated 
 of in a particular article. It appears that sulphuric acid is in- 
 jurious to it, when it is to serve for the solution of tin ; and 
 the acid prepared in manufactories, by means of the sulphuric, 
 usually contains some ; whence dyers often prefer that extracted 
 by the agency of clay. 
 
 For understanding a great number of phenomena, it is essen- 
 tial to have an exact idea of the nature of the nitric acid, and 
 of the action which it exercises on other substances. 
 
 Nitric acid is composed of two substances, which, when they 
 are insulated, assume the elastic, aeriform, or gaseous state. 
 These substances are oxygen and azote, which also compose our 
 atmosphere. The different action (of these two compounds) 
 depends on the state in which they exist. In the atmosphere 
 they are endowed with elasticity, which is an obstacle to their 
 combination with other substances ; but this obstacle, and the 
 intensity of their action, vary, by reason of their state of expan- 
 sion and their condensation. 
 
 The elastic force of oxygen gas, and azotic gas, like that of 
 other gaseous substances, being diminished by the afSnity which 
 produces their combination, and which reduces their volume, 
 they can act in a greater mass on the other substances, and the 
 energy which they thereby acquire may exceed by much the 
 diminution which results from their reciprocal saturation. 
 
 But these two gases may contract an union, which differs 
 according to their proportions, according to the condensation 
 derived from it, and according to the concurrence of other sub- 
 stances, and particularly of water, which may augment their 
 condensation without acting on them by a great saturation. 
 
 These circumstances determine the different states of com- 
 bination of these two elements, and the properties of these 
 compounds. 
 
198 
 
 BERTHOLLET ON DYEING. 
 
 Nitrous gas must be regarded as the first state of combination. 
 It dissolves in only a small quantity of water ; it does not com- 
 bine with alkalies ; it is easily decomposed by substances which 
 tend to unite with oxygen ; but it unites by mere contact with 
 a greater proportion of oxygen. It thereby passes to another 
 state ; and as its two elements are little condensed, the action of 
 heat alone, or the dilatation which it produces, has but little 
 efficacy to separate them. The proportions that constitute it 
 are nearly 44 parts by weight of azote to 56 of oxygen, (47 
 to 53.) 
 
 When an oxygenable substance deprives the nitrous gas of a 
 portion of its oxygen, such as a sulphite, which thereby passes 
 to the state of a sulphate, another combination is established, in 
 which the elements, by reason of the proportions in which they 
 exist, exert more powerfully their reciprocal action, so that 
 their condensation is greater. This is the gaseous oxyde of 
 azote, whose specific gravity, according to Deivy, is to that of 
 oxygen gas in the ratio of 147 to 100 ; and which contains, by 
 the determinations of the same chemist, 63 parts by weight of 
 azote to 37 of oxygen. 
 
 This greater condensation, which proves a stronger reciprocal 
 action, and the composition, explain the properties which cha- 
 racterize this gas. It dissolves more copiously in water than 
 the nitrous gas, and yet it has no acid taste, but on the contrary 
 a saccharine one. The oxygen present in it, is too strongly 
 saturated by the azote, to produce the acidity which depends on 
 its combinations. It no longer acts on oxygen gas, and is not 
 decomposed at an ordinary temperature, by the substances 
 which operate the decomposition of nitrous gas ; but if the 
 temperature be elevated, the expansive action of the heat, which 
 tends to separate its two condensed elements, determines its 
 decomposition, and the oxygen produces a vivid combustion. 
 
 When nitrous gas acts on pure oxygen gas, or on that pre- 
 sent in the atmosphere, it becomes ruddy, and the new substance 
 designed by the name nitrous vapour, which condenses very 
 little, and preserves a livelier ruddiness, as the temperature is 
 higher, forms another combination when it is placed in contact 
 with water. This decides the formation of nitric acid, of which 
 it is itself an essential part ; for nitric acid resumes the state 
 of nitrous vapour when it is deprived of water, unless it be 
 
OF THE CHEMICAL AGENTS. 
 
 199 
 
 retained in a state of condensation by another base, as in the 
 nitrates. 
 
 Jf nitrous vapour contain too great a proportion of nitrous 
 gas, this excess remains in the gaseous state ; if the oxygen 
 gas be in excess, a portion of it remains gaseous. 
 
 A portion of the nitrous gas may, however, be held in solu- 
 tion by the nitric acid ; but this quantity varies according to 
 the proportion of w^ater, giving the acid an orange, green, or 
 blue colour. This excess of nitrous gas attracts oxygen by 
 degrees from the atmospheric air, passing itself to the state 
 of nitric acid. 
 
 In nitric acid, the proportion of oxygen is to that of azote 
 nearly in the ratio of three to one by w^eight. It is not sur- 
 prising, therefore, that this compound, containing oxygen in so 
 large a proportion, should have the qualities of an energetic 
 acid, v^hilst the gaseous oxyde of azote, where the azote predo- 
 minates, has perceptibly none. But the nitric acid owes its 
 liquid state only to the action which water exerts upon it. 
 
 When it is combined v/ith an alkaline base, and when a more 
 fixed acid, as the sulphuric, divides its action on this base, heat 
 augments its elastic disposition, so as to volatilize it v/ith the water 
 which the sulphuric acid contained. This water is inadequate 
 to make the whole of it preserve the acid condition ; a portion 
 is therefore disengaged in the state of nitrous vapour, and by 
 the condensation of this in the water presented to it, some 
 nitric acid is reproduced. But the acid which has assumed the 
 liquid state, retains nitrous gas, and is more or less ruddy. The 
 corresponding portion of the oxygen gas is disengaged in the 
 elastic state. 
 
 If nitre, or nitrate of potash, be decomposed by means of 
 clay, this seems to retain the water with sufficient strength, so 
 that a quantity of it, capable of maintaining the nitric acid in 
 the liquid condition, may come over even to the end of the 
 operation. Hence, in this case, the acid is not fuming, or is 
 very slightly so. 
 
 The substances which have a great action on oxygen, may 
 decompose nitric acid, according to the energy of this action. 
 Thus the very oxydable metals especially, produce gaseous 
 oxyde of azote, while the oxyde thereby formed dissolves in a 
 portion of the undecomposed acid. But the less oxydable metals 
 
BERTHOLLET ON DYEING. 
 
 give rise only to nitrous gas, whicli retains a greater propor- 
 tion of oxygen. 
 
 The facility with which nitric acid is decomposed, when it is 
 not condensed by a base which gives it stability, renders it little 
 fit for being employed with the colouring particles, which 
 separate the oxygen from it more or less speedily, and thereby 
 suffer destruction. In destroying these particles, it causes them 
 to undergo the changes due to an imperfect combustion, in 
 which the hydrogen enters into combination with the oxygen, 
 in larger proportion than the carbon, making the latter prin- 
 ciple predominate in the residuum. 
 
 In purchasing this acid, we must not let ourselves be im- 
 posed upon by its more or less ruddy colour. It is easy to 
 give it this appearance, by a small ^quantity of iron, or other 
 substance, which generates nitrous gas. It must, indeed, have 
 a certain degree of concentration to be fuming ; but it may be 
 highly concentrated without possessing this appearance. 
 
 The specific gravity may likewise lead to fallacies, because 
 it can be increased by the addition of sulphuric acid. It is 
 only after ascertaining that this cause of ferror does not exists 
 that we can repose confidence in that criterion. 
 
 III. — Of Muriatic Acid. 
 
 Muriatic acid is particularly distinguished by being more 
 volatile, or more disposed to preserve the gaseous state, than the 
 preceding acids, and by having much less affinity for water. 
 Hence, when combined with it, its elastic action needs only be 
 increased by heat for it to quit it, and to resume the state of 
 gas, till little enough remains to make the attraction of the 
 water be equivalent to the elasticity of the acid. 
 
 Although muriatic acid has a greater capacity of saturation 
 for the alkaline bases than sulphuric acid, it is however expelled 
 from its combinations by this acid, especially when its elasticity 
 is augmented by heat. Hence the effect of its elasticity over- 
 comes the excess of affinity, which tends to maintain its combi- 
 nation with the base. 
 
 Muriatic acid gas, combined with water, forms muriatic acid, 
 which was known under the name of marine acid, or spirit of 
 salt. It has a peculiar odour, analogous to that of saffron. 
 
OF THE CHEMICAL AGENTS. 
 
 201 
 
 When concentrated it gives white vapours to the air, which are 
 produced by the combination of this acid with the water present 
 in the atmosphere. It ceases to afford these vapours at the 
 point in which it is saturated with the whole waiter which it can 
 take from the atmosphere. Tt has usually a yellow colour, de- 
 rived from a little iron, or chlorine, for when very pure it is as 
 colourless as water. 
 
 This acid is extracted on the great scale from sea salt, or 
 muriate of soda, distilled along with clay. But by this process 
 it is always weak. It is disengaged from the same salt by means 
 of sulphuric acid. 
 
 This process has much resemblance to that described under 
 nitric acid ; but there are some differences which depend on the 
 greater volatility of the acid. 
 
 A tubulated retort is made use of, or which is preferable, a 
 large matrass, to whose orifice there is adapted a tube bent in 
 its middle, with an enlargement in the lower part of its curva- 
 ture. By this tube the sulphuric acid is introduced, a por- 
 tion of which being retained in the curvature and the swelling, 
 serves to stop the issue of the gas, whose pressure disturbs 
 only the level at which it stands in the two branches of 
 the curvature. The obstacle resulting from the elevation 
 of the column of sulphuric acid, determines the gas, there- 
 fore, to pass off by a conductor tube, w^here it finds less 
 resistance. 
 
 The salt is first introduced into the matrass ; after which there 
 is poured in three-fourths (|) of its weight of sulphuric acid, 
 which should be previously diluted. The rest of the apparatus 
 should have been also arranged beforehand. It consists of two 
 bottles, into which is distributed a weight of water equal to 
 that of the salt employed. But as the vapour which is disen- 
 gaged unites speedily with the water, a vacuum is readily formed, 
 which makes the liquid of the second bottle pass back into the 
 first, and from the first into the retort. To prevent these re-ab- 
 sorptions, the first bottle ought to be furnished with the tube 
 of safety contrived by Welter. This tube is introduced into a 
 particular tubulure, or still better through one of the corks 
 which gives passage to a tube of communication. If a vacuum 
 be formed, the atmospheric air returns into the bottle ; but 
 while the issuing vapour presses on the liquid, this rises in the 
 
202 
 
 BEUTHOLLET ON DYEING. 
 
 tube, till its column counterbalances the compression of the va- 
 pour. It is requisite to lute with much care, because the vapours 
 of muriatic acid are very penetrating ; and when they have once 
 forced a passage through the lute, it is very difficult to repair it. 
 Should this accident, however, happen, the best means of reme- 
 dying it is, to rub the outlet with some alkali, so as to saturate 
 the acid, and immediately after to stop it with the lute. It is 
 necessary to wait till the effervescence produced by the affusion 
 of the sulphuric acid be assuaged, before putting fire under the 
 retort, which should be placed on a sand-bath, and the fire 
 should be nicely tempered, especially at the beginning of the 
 operation. 
 
 The acid obtained in the first bottle is highly concentrated 
 and smoking, especially if it had been kept immersed in cold 
 water, or pounded ice ; but it may contain sulphuric acid, which 
 is discovered by diluting it with distilled water, and pouring into 
 it a little solution of barytes, which produces a precipitate. It 
 may be rectified by distilling it from a little sea salt. 
 
 The acid of the second bottle is much less concentrated. If 
 too weak for the purposes for which it is intended, it may be used 
 instead of water in a second operation. It has, however, the 
 advantage of being pure. 
 
 Muriatic acid is hardly ever employed directly in the processes 
 of dyeing; but it serves to form, metallic solutions fit for making 
 mordants, alone, or in conjunction with nitric acid. Muriate of 
 tin- is the combination which deserves most attention. We owe 
 to Pelletier and Proust very interesting observations on this 
 muriate.* We shall detail such of them as relate to our subject. 
 
 To prepare the solution of tin by muriatic acid, Pelletier 
 directs to put one part of tin, and four parts of concentrated 
 muriatic acid in a matrass, placed in a sand-bath, which is 
 gradually heated to ebullition. The heat of ebullition cannot 
 be favourable to the combination of the muriatic acid, on account 
 of the elastic force which it gives it. It seems therefore that a 
 more moderate degree of heat is suitable ; but ebullition may 
 be afterwards produced, in order to expel the excess of acid, 
 which may be condensed in a second matrass. We then proceed 
 to crystallize. 
 
 * Mem. et obscrvat. do clniiiic dc PcllctitT, torn, i, Proust Joiun. de physique, torn. li. 
 
OF THE CHEMICAL AGENTS. 
 
 203 
 
 The muriate produced by this process contains the tin in the 
 lowest degree of^oxydation requisite for its combination with an 
 acid. In this state it carries off the oxygen, not only from the 
 chlorine and sulphurous acid, but also from the atmospheric air, 
 and from all bodies which do not retain this element with force. 
 Hence, it may obviously be a very proper, guide in researches on 
 the properties of colouring substances ; and since the oxyde of 
 tin combines easily with stuffs and colouring particles, this 
 muriate may be very useful in the processes of dyeing. 
 
 Its effects must vary according to its state of actual oxydation. 
 Pelletier concludes from some trials, that in its most oxydized 
 state it is most advantageous in dyeing. This conclusion is per- 
 haps too general, and we believe that experiments must decide 
 what is proper in this respect for each species of dyeing. 
 
 To obtain muriate of tin in the most oxygenated state^ 
 Pelletier prescribes the transmission of chlorine into a solution 
 of tin in muriatic acid, till this retains the odour of it ; after 
 which the excess of acid must be volatiHzed by heat. The 
 muriate of tin may be oxygenated by leaving its solution simply 
 exposed to the atmospheric air. But the operation is slow. 
 
 It is particularly for cotton and linen that the muriate of tin 
 may be advantageously employed in dyeing, or at least it 
 cannot be used in quantity for substances of an animal nature, 
 because muriatic acid exercises too keen an action on them. 
 This fact is applicable to the other metallic muriates. 
 
 The alkaline muriates are used only as alteratives. In general 
 they give a deeper shade to colours. 
 
 We have discussed at sufficient length the preparation and 
 properties of chlorine in treating of bleaching. We shall con- 
 fine ourselves here to some considerations on the properties 
 which distinguish it from the preceding acids, and on the 
 differences thence resulting as to their preparations. 
 
 Muriatic acid naturally possesses considerable elasticity ; yet 
 the action of water can condense a very large quantity, and give 
 it the liquid state, although it is much less powerful than on 
 nitric and sulphuric acids. It combines with oxygen to form 
 oxygenated muriatic acid, (chlorine,) But this combination is 
 feeble, so that it produces but a slight change on the natural 
 qualities of the oxygen and muriatic gases. Chlorine is much 
 less soluble in water ; hence the apparatus for the preparation 
 
204 
 
 BERTHOLLET ON DYEING. 
 
 of liquid chlorine ought to be so contrived, that the gas may be 
 disengaged in the lower part of the receiver, so as to be retained 
 in contact with the water under a first tub, that that which arrives 
 next may flow out under a second, and lastly under a third tub. 
 Thus, by the length of the contact, the solution requiring 
 longer time as it is effected by a feeble affinity, may have leisure 
 to take place. (Note W.) 
 
 The apparatus which we have described, and which may be 
 modified in different manners, is adapted to maintain the contact 
 of the gas with the water ; but it would be too troublesome 
 and expensive, when chlorine is wanted only for some tests or 
 experiments. In this case, an apparatus similar to what we 
 have pointed out for the preparation of muriatic acid may be 
 substituted. It is necessary to employ merely three successive 
 receivers, or three bottles furnished with their tubes of safety. 
 The conductor tubes, intended to transmit the gas from one 
 bottle into another, must issue from the upper part of the one 
 bottle, and dip into the lower part of the next. If the gas be 
 received into an alkaline solution, two receivers, or even one, 
 may suflSce. 
 
 Instead of the mixture of muriate of soda and sulphuric acid 
 which we have prescribed, muriatic acid may be directly em- 
 ployed. One part of manganese is then necessary for four parts 
 of concentrated muriatic acid, or for an equivalent quantity of 
 weak muriatic acid ; and the latter is preferable on account of 
 the too tumultuous disengagement of gas, produced by the con- 
 centrated acid. The heat can hardly be too slowly conducted. 
 The operation should cease whenever the first tube becomes hot. 
 Chlorine acts diflferently, according to the affinity which the other 
 substances have for the two elements that compose it. If these 
 bodies tend to combine particularly with oxygen, they carry oflT 
 this element from the muriatic acid, which is retained by the 
 water. Thus light disengages the oxygen, restoring it entirely 
 to its elastic state, while the water retains the plain muriatic 
 acid. Thus, also, the colouring substances take possession of 
 the oxygen, which thereafter exerts its action on such of their 
 elements as have most aflSnity for it. 
 
 The alkalies tend to combine with the two elements of the 
 chlorine, although in some circumstances, the action which they 
 exercise on the muriatic acid determines, by the formation of a 
 
OF THE CHEMICAL AGENTS. 
 
 205 
 
 muriate, the separation of a portion of the oxygen, which re- 
 sumes the gaseous state. But, excepting this effect, the action 
 of the alkalies condenses the chlorine, and, by a necessary con- 
 sequence, lessens or represses its odour. 
 
 When the condensation arrives at a certain degree, the action 
 of the alkalies, becoming proportionally more energetic, decides 
 the formation of two new combinations, one of which is a simple 
 muriate, and the other a chlorate. The oxygen accumulated in 
 the latter undergoes on the part of the alkalies so strong an 
 action, that light and colouring substances can no longer disen- 
 gage it. The whole of the chlorine, which contributes to the 
 formation of a chlorate, when we receive the chlorine into an 
 alkaline solution, is therefore lost as to the power of disco- 
 loration. 
 
 The difference of action between nitric acid and chlorine, on 
 colouring substances, and in general on vegetable and animal 
 bodies, depends on the affinity of the oxygen for azote, and 
 for muriatic acid. The first is much the stronger. Hence, 
 nitric acid gives up its oxygen with far greater difficulty ; but 
 when the resistance of this affinity is overcome, the results of 
 the action of both are similar. 
 
 The same difference is observed in the action of the two 
 acids on the metals. Nitric acid is decomposed only in part 
 by the action of the metals ; and while one portion gives up its 
 oxygen, another usually combines with the metallic oxyde with- 
 out changing its nature. But the chlorine is entirely destroyed 
 by the action of the metals. From the metals, merely super- 
 oxydized muriates are obtained ; and only alkaline muriates in 
 the precipitation by the alkalies. Hence the denomination of 
 oxygenated muriate of mercury, for example, might give a false 
 idea of this combination, which is merely a highly oxydized 
 muriate of mercury. Oxygenated muriates of the metals 
 may, however, be formed, by combining the chlorine with a 
 metal already saturated with oxygen, as Chenevix has shown. 
 (Note X.) 
 
 IV. — Of Aqua Regia, or Nitro-muriatic Acid. 
 
 To this compound acid, the name aqua regia has been given, 
 because it has the property of dissolving gold, which was called 
 
206 
 
 BERTHOLLET ON DYEING. 
 
 the king of metals. But it should be regarded as a mixture 
 of muriatic acid and nitric acid, which combine their forces to 
 effect solutions which they could not separately do. 
 
 By the reciprocal action of these two acids, a portion of the 
 nitric acid is decomposed. Hence results a development of 
 chlorine which exhales, diffusing its odour; and nitrous gas is 
 proportionally formed, which remains dissolved in the compound 
 acid, and which colours it progressively, till an equilibrium of 
 combination be effected. But neither the chlorine which is 
 volatilized as it forms, nor the nitrous gas, which is also ex- 
 pelled whenever the acid exerts its action on another substance, 
 contributes to its action on the metals. As its operation only 
 is considered, the name nitro-muriatic acid is retained for it, 
 whatever be its composition. 
 
 Nitro-muriatic acid may be prepared, either by simple mix- 
 ture of the nitric and muriatic acids, or by dissolving muriate 
 of ammonia, or of soda in nitric acid. Other salts might be 
 made use of, for example nitre (nitrate of potash,) which might 
 be dissolved in muriatic acid. Several other processes might be 
 employed, which it is needless to describe. 
 
 It is especially for the solution of tin that nitro-muriatic acid 
 is to be examined, because it is the principal use which is 
 made of it in dyeing. 
 
 Dyers do not prepare in an uniform manner the solution of 
 tin, to which they give the name of composition (spirit.) Every 
 one has his recipe. This solution, however, produces different 
 effects, according to the process made use of. It is essential 
 that the same artisan should prepare it always in the same 
 manner, in order to obtain uniform effects, and to guide him- 
 self by the observations which he may have made in the pre- 
 ceding operations. 
 
 Several dyers make use merely of the aquafortis of com- 
 merce ; and it seems, that when they began to employ the solu- 
 tion of tin, they used no other solvent. This aquafortis is a 
 species of nitro-muriatic acid, because there has been employed 
 for its preparation an impure nitre, which is mixed with a 
 greater or less quantity of marine salt. But this quantity 
 varies ; and the concentration of the aquafortis is likewise sub- 
 ject to many variations. Hence this acid must produce uncertain 
 effects. 
 
OF THE CHEMICAL AGENTS. 
 
 207 
 
 Pure nitric acid dissolves tin only when it is very mucli 
 weakened, and when care is taken to keep the vessel with the 
 materials in cold water. The metal is, in this case, at the 
 lowest degree of oxydation, according to Proust's observation. 
 But it speedily falls down, even at an ordinary temperature. 
 
 Vogler employed a similar solution in dyeing. He prevented 
 the precipitation of the oxyde, by adding muriate of soda or 
 ammonia : but it is better to employ immediately the nitro- 
 muriatic acid, which requires less attention. 
 
 When a more concentrated nitric acid is used, or when heat 
 is applied, the tin passes to the maximum of oxydation, and is 
 entirely precipitated. This process is had recourse to for ascer- 
 taining the weight of tin which exists in an alloy ; the tin 
 having thus taken 40 parts of oxygen for 100 of metal. 
 
 Hellot took 32 parts of nitric acid, which he mixed with an 
 equal quantity of filtered water (distilled water ?) he dissolved in 
 it, by little at a time, two parts of very white muriate of am- 
 monia, and one part of nitrate of potash ; and lastly, two parts 
 of granulated tin. Scheflfer dissolved one part of tin in four 
 parts of nitro-muriatic acid.* Macquer dissolved three parts of 
 tin in eight parts of nitric acid, with which he mixed one part 
 of muriate of ammonia, and six parts of water. Poerner em- 
 ployed other proportions, &c. 
 
 These solutions, so very various, possess undoubtedly difierent 
 properties. In them all, one essential object is wanting, which 
 is a preparation constantly uniform. For this purpose, it is 
 indispensable to make use of a pure nitric acid, and to deter- 
 mine its specific gravity by means of the hydrometer. The 
 process which was resolved upon, after several trials, in the first 
 edition of these Elements, consists in tciking nitric acid at 
 30° B. (1.26 sp. grav.) ; to dissolve in it one-eighth of its weight 
 of muriate of ammonia, to add by small portions at a time one- 
 eighth of its weight of tin, and afterwards to dilute this solution 
 with a fourth of its weight of water. 
 
 A pure tin, such as the Malacca tin, or good English tin, 
 must be selected ; because the common tin (of France) contains 
 copper and lead, metals which would be injurious to the beauty 
 of the colours. Even in the fine tin of England some copper 
 
 * Essai sur I'art dc la teinture. 
 
20S 
 
 BERTHOLLET ON DYEING. 
 
 is found ; but common tin contains occasionally nearly one-half 
 its weight of lead, and antimony and bismuth besides.* The 
 tin must be reduced into granulations, by melting it and pour- 
 ing it into water, which is agitated with a bundle of small rods ; 
 an operation which ought to be cautiously made, to avoid 
 explosions. 
 
 In the solution of tin, there is usually formed a small blackish 
 deposite, from which the liquid should be decanted. 
 
 The solutions which contain a great proportion of tin are 
 brown, and afford deeper and duller colours ; yet occasions may 
 be found where they can be useful. One may be obtained 
 highly charged with tin, which may be advantageous in certain 
 cases, by decomposing in a retort, at a very moderate heat, 
 muriate of ammonia, mixed with an equal weight of oxyde of 
 tin. The residuum is dissolved, filtered, and evaporated so as 
 to crystallize. By this means crystals are procured of a triple 
 salt, composed of muriatic acid, ammonia, and oxyde of tin. 
 To make use of this salt, a little muriatic acid must be added 
 to its solution, which prevents the precipitation of the oxyde 
 of tin. 
 
 The solution of tin in nitric acid is accompanied by a pro- 
 duction of ammonia. We have ascertained that the same pro- 
 duction took place, when the solution was effected with the 
 simple mixture of muriatic acid and nitric acid, although it be 
 made with great slowness and precaution, and although the 
 oxyde of tin be only in the lowest state of oxydation. It thence 
 appears, that there must be less difference than might be thought 
 between the action of simple nitro- muriatic acid, and that of the 
 preparation into which muriate of ammonia is put. 
 
 It is probable that a new quantity of ammonia is produced 
 in the very process of scarlet dyeing, which is performed at a 
 degree of heat approaching to ebullition. 
 
 It has been attempted to explain, by the action of this am- 
 monia, which saturates the muriatic acid, and whose formation 
 contributes at the same time to the destruction of the nitric 
 acid, why the nitric acid does not attack (corrode) wool in dye- 
 ing scarlet, which is done at so high a degree of heat, although 
 this acid be very destructive to it when it is insulated. 
 
 * Rcclierches siir Tetiiin ; par MM. Bayon ct Charlard. By common tin, tlie Author 
 naust mean what we call pewter. — T. 
 
OF THE CHEMICAL AGENTS. 
 
 209 
 
 In this saturating action has been also seen the explanation 
 of an observation of Bancroft. In dyeing scarlet, he wished to 
 substitute muriate of tin* for the nitro-muriate ; but a larger 
 proportion of it was required, and the wool was found to be 
 deteriorated. In this operation no ammonia could be formed, 
 and the muriatic acid, which weakens the woollen fibre, exerts 
 all its action on it. 
 
 Muriate of tin may be more useful for cotton and linen, on 
 which substances muriatic acid has much less action. 
 
 No consideration ought to be neglected for varying the mor- 
 dant best fitted to procure fine colours in dyeing. 
 
 The solution of tin assumes more or less quickly the consist- 
 ence of a jelly. When this occurs, the dyers say that the compo- 
 sition has turned. For avoiding this, it is proper to make the 
 preparation only a short while before it is to be used. When 
 the jelly is merely beginning to form, the solution may be restored, 
 by adding a certain quantity of muriate of soda. This incon- 
 venience proceeds from the tin continuing to get more oxydized 
 by means of the oxygen which it attracts from the atmosphere, 
 or receives from the nitric acid ; and from a greater quantity 
 of ammonia being formxcd, which, rendering the tin insoluble 
 in the acid, causes it to precipitate. Heat promotes this effect ; 
 hence the solution of tin does not keep so long in summer as 
 in winter. 
 
 Uniform observation has taught, that when the solution of tin 
 is briskly made with the copious evolution of vapours, the 
 colours obtained from its employment are less lively and less 
 agreeable, than when the solution is made slowly and without 
 effervescence. Hence, at least for the dyeing of wool, tin should 
 be at the lowest stage of oxydation. It does not remain in this 
 state ; and it seems to pass to a more advanced degree of oxyd- 
 ation in the very operation of dyeing. It would not otherwise 
 afford a white basis to the colour. But this circumstance is 
 undoubtedly advantageous. It is a reason for preferring solu- 
 tions which are recent, and made with slowness, to those which 
 are old, with whatever care they may have been prepared. 
 
 Haussman has recommended, for some purposes, the acetate 
 
 * He prescribed also murio-siilpliate. — T. 
 P 
 
210 
 
 BERTHOLLET ON DYEING. 
 
 of tin obtained by means of a solutioil of tin (muriate) and 
 acetate of lead. 
 
 Other (metallic) solutions are made with nitro-muriatic acid, 
 which may be useful in dyeing. De la Folic has proposed that 
 of bismuth ; and although he begins to dissolve the metal in 
 the nitric acid, it is however a combination with the nitro-muri- 
 atic acid, which is formed in this process by means of the muriate 
 of soda which he adds. The solution in nitric acid alone would 
 not answer, because, whenever it is mixed with water, the me- 
 tallic oxyde falls down, forming an insoluble salt, and thereby 
 separates without being able to unite to the colouring particles. 
 
 According to the description of this process given by Dam- 
 bournay, of which he himself made much use,* one part of 
 bismuth is to be dissolved in four parts of nitric acid. This 
 solution is to be poured into a bath which contains tartar, along 
 with a solution of muriate of soda. 
 
 It has been found, that whether the solution of bismuth had 
 been made directly with nitro-muriatic acid, or whether the 
 solution in nitric acid was mixed with a solution of sea salt and 
 tartar, a considerable precipitate was always formed on contact 
 with water, although less copiously than when the simple solu- 
 tion in nitric acid was mixed with water. It has been remarked, 
 moreover, that the precipitates which this solution occasioned 
 with the decoctions of colouring substances, had an unequal 
 colour, and speedily became brown. 
 
 V. — Of Bitartrate and Binoxalate of Potash, and of 
 Acetic Acid. 
 
 The tartaric acid, which predominates in the bitartrate of 
 potash, owes the properties which distinguish it from other 
 acids, the features of which are traceable in its combinations, 
 to its fixity and disposition to take the solid state, which is so 
 great, that notwithstanding its affinity for water, it separates 
 from it, and crystallizes at ordinary temperatures. 
 
 The effects of this tendency are increased by the condensation 
 which affinity produces ; while, at the same time, the action 
 
 * Recueil de proct^des et d'experiences sur les teintiires solides. 
 
OF THE CHEMICAL AGENTS. 
 
 211 
 
 which it exerts on water, as well as that of its base, is diminished 
 by their mutual saturation. 
 
 These considerations show, that the tartaric acid might pro^ 
 duce, with alkaline bases in themselves very soluble, combin- 
 ations of little solubility, when circumstances permit them to 
 retain an excess of the least soluble element, which is the acid. 
 Thence arise the bitartrates, or salts with excess of tartaric 
 acid, as also the oxalates, the bisulphates, which equally proceed 
 from acids having more disposition to the solid state than their 
 bases. 
 
 For the same reason, this acid produces with the bases that 
 have little solubility insoluble salts, which have no need of an 
 excess of acid to acquire this quality. This same insoluble 
 combination is formed every time that combinations of acid and 
 of bases are brought together, some of which are sparingly 
 soluble, provided there be no excess of acid to oppose this 
 effect by its solvent power. This disposition determines there- 
 fore the precipitates, and the exchanges of base which take 
 place, by means of the tartaric acid, in the reciprocal action of 
 the acids and alkalies, or of their combinations. 
 
 If in an acid and slightly soluble tartrate the proportion of 
 base, which has of itself much solubility, be increased, pro- 
 portions are attained which yield a neutral salt. Such are the 
 tartrates of potash, soda, or ammonia, which by this increase 
 of base have acquired a greater solubility than in the acid 
 state, although they still possess the power of crystallizing. 
 Should an insoluble base abstract their acid, the alkali does 
 not part with it entirely. Thus Vauquelin observed, that on 
 decomposing the bitartrate of potash by quicklime, which 
 forms an insoluble tartrate of lime, the remaining alkali re- 
 tained a portion of tartaric acid. 
 
 If instead of lime we make use of the carbonate of lime, it is 
 only the excess of acid which, by its action on the lime, pro- 
 duces a disengagement of carbonic acid, and forms a propor- 
 tional quantity of tartrate of lime. When the tartrate of potash 
 has thereby attained the neutral state, the tartaric acid has no 
 longer a strong enough action on the lime, to separate its 
 carbonic acid. 
 
 Hitherto tartaric acid has not been employed in the art of 
 
 p 2 
 
212 
 
 BERTHOLLET ON DYEING. 
 
 dyeing. It is the bitartrate of potash which is used. (See 
 Note I.) 
 
 This salt, usually called tartar^ is deposited on the sides of 
 casks, from which it is afterwards detached. In its natural 
 state it is mingled with impurities deposited at the same time. 
 When it is separated from red wine, it retains a great deal of 
 the colouring matter of the wine, whence it is call red tartar. 
 
 Tartar is purified by different processes at Montpellier and 
 Venice. At Montpellier, the tartar is dissolved in hot water, 
 and crystallized by cooling. The crystals are boiled in another 
 copper, and there is added 11 or 13 pounds of the white 
 clay of Murviel for every 22 pounds of the salt. This earth is 
 boiled with it, and by evaporation we obtain the purified tartar, 
 cream of tartar, or bitartrate of potash. 
 
 The process practised at Venice consists, according to the 
 description given of it by Desmaretes,* 1. In drying the tartar in 
 iron boilers ; 2. In bruising and dissolving it in hot water, by 
 the cooling of which purer crystals are obtained ; 3. In redis- 
 solving these crystals, and clarifying the solution with whites of 
 eggs and wood-ashes. 
 
 In the latter process the alkali of the ashes must saturate a 
 portion of the bitartrate : the calcareous earth must also effect a 
 decomposition ; and, towards the end of the evaporation, tartrate 
 of potash should be obtained. 
 
 The bitartrate of potash, or cream of tartar, retains always a 
 little calcareous tartrate. 
 
 Water dissolves less than one-hundredth of this salt at 10° 
 Reaumur (about 55° Fahr. ;) but boiling water dissolves much 
 more of it. 
 
 Much use is made of bitartrate of potash, or tartar, in dyeing. 
 For delicate colours it is indispensable to employ the purified 
 salt, and it is preferable in every case. In some processes red 
 tartar is recommended as proper to contribute by its colour to 
 the colour that is wanted. But the red particles separate from 
 the tartar when the salt is dissolved, and they should be regarded 
 merely as hurtful impurities. 
 
 Of the effects produced by tartar in dyeing, a clear explana- 
 tion cannot yet be given. Experience teaches merely, that it 
 
 * Journ. de physique, 1771. 
 
OF THE CHEMICAL AGENTS. 
 
 213 
 
 moderates the action of alum on woollens, the fibres of which 
 are easily degraded. It is probable that the colouring par- 
 ticles^ in fixing themselves on the stuffs, either alone or with a 
 base, carry a small portion of it into their combination, thereby 
 modifying the colour. 
 
 There is another salt, which has some analogy with tartar, 
 and which may perhaps produce good effects on several occa- 
 sions. This is the binoxalate of potash, or salt of sorrel, ex- 
 tracted from wood-sorrel in several parts of Switzerland and 
 Germany. Scheele has shown, that the acid of this salt is the 
 same as that obtained from sugar, and from several animal and 
 vegetable substances, on treating them with nitric acid, whose 
 oxygen enters into combination with a due proportion of hy- 
 drogen and carbon. But it exists native, combined in excess 
 with potash, in wood-sorrel and some other plants. Oxalate of 
 lime, which is insoluble, is found in several roots. 
 
 The properties which oxalic acid communicates to the differ- 
 ent bases, and the effects which it produces on the other com- 
 binations, are to be explained, like those of the preceding acid, 
 from its insolubility, which causes it in like manner to crystal- 
 lize. Hence it is made use of in chemistry to discover the 
 existence and the quantity of calcareous earth held in solution. 
 But for the complete production of this effect an excess of acid 
 must be avoided, and all its combinations must be nearly in the 
 neutral state. The binoxalate of potash, or salt of sorrel, pro- 
 duces analogous effects. 
 
 This oxalate readily dissolves iron, forming a soluble salt, 
 which renders it useful for removing spots caused by that metal. 
 Oxalic acid produces also an oxalate of iron, which dissolves 
 easily in an excess of acid. This property makes it be employed 
 at present, in some manufactures, for destroying the colours 
 whose basis is oxyde of iron. 
 
 Acetous acid, or the acid of vinegar, was distinguished from 
 acetic acid, or radical vinegar, on a supposition that the latter 
 contained a larger proportion of oxygen, and had thereby a 
 greater acidity. But Adet and Darracq have shown, that be- 
 tween these acids there is no difference which can authorize 
 their being distinguished. Acetic acid is merely more concen- 
 trated, and the processes by which it is prepared serve only to 
 
2U 
 
 BERTHOLLET ON DYEING. 
 
 exclude its water. We shall therefore designate them by the 
 common appellation of acetic acid. 
 
 Acetic acid has qualities opposed, as it were, to those of the 
 preceding acids. It is volatile, but it has a great affinity for 
 water. It ought therefore to form combinations which have in 
 general much solubility. It seems to have a small capacity of 
 saturation ; hence its combination must produce but a feeble 
 condensation. From these causes it retains its bases but weakly, 
 and is easily expelled from them by the action of other sub- 
 stances, as well as by heat. As it is volatile, and can assume 
 the gaseous state, according to the experiments of Priestley, the 
 action of the air promotes its separation. 
 
 This acid is formed, not only by the fermentation which is 
 termed acid (acetous,) but also by putrefaction, as Fourcroy and 
 Vauquelin have 'proved. It would appear that the substances 
 which contain no azote are not capable of yielding this acid ; 
 for they receive no azote from the atmosphere during fer- 
 mentation ; and the experiments of Proust show that this acid 
 contains a certain portion of it. (Note Y.) 
 
 Acetic acid is also formed in the distillation of several sub- 
 stances, and particularly of wood. To acid thus formed the 
 name pyrolignous was given ; but Fourcroy and Vauquelin have 
 proved that it did not differ essentially from the acetic acid, 
 and that it is merely this very acid holding in solution a bitumi- 
 nous oil, which is produced in the same operation, a part of 
 which separates by keeping. It gives up the greater part of it 
 when rectified by a second distillation. It may, however, be 
 distinguished by the name of pyrolignous acid, not in order to 
 indicate any difference of acidity, but its bituminous condition 
 and uses. 
 
 Bosc has shown * that this acid possessed peculiar properties 
 %r black dyes on cotton, which it derived from its carbonized 
 oilT We shall, elsewhere, point out the interesting process, 
 which we owe to him. 
 
 This acid merits much attention, not only for this purpose, 
 but for several others, because it can be obtained at little ex- 
 pense,, and its carbonized oil may be useful, or is at least not 
 
 * Aunalcs clcs arts ct manufactures, torn. v. 
 
OF THE CHEMICAL AGENTS. 
 
 215 
 
 injurious. Guyton,* by distilling in an iron retort chips of 
 very dry beech-wood, and rectifying the first product by a 
 second distillation, extracted a quantity of acid, which exceeded 
 in weight one-third of the wood employed, and the charcoal re- 
 mained. 
 
 CHAPTER II. 
 Of Alum^ or the Sulphate of Alumina, 
 
 Alum is designated in chemistry by the name sulphate of 
 alumina; and although this denomination does not indicate 
 rigorously the elements of which it is composed, it is however 
 useful, and fulfils the usual purpose of nomenclature, because it 
 denotes the ingredients which should fix attention in the greater 
 number of the phenomena that are investigated. 
 
 This combination is of very frequent use in the art of dyeing ; 
 it is also employed in several other arts. Hence, for directing 
 its application, we must be well acquainted with its properties 
 and diversities ; and its preparation becomes an object of con- 
 siderable importance. 
 
 Alum is found in some mineral springs. It effloresces on the 
 surface of schists in coal mines, or on the lavas in the neighbour- 
 hood of volcanoes, and on several rocks. But the greatest part 
 of the alum employed is extracted from peculiar ores, or is 
 fabricated by an artificial combination of alumina and sulphuric 
 acid. 
 
 Alum is mentioned in the works of the ancients, and that 
 from Melos in particular was esteemed among the Greeks ;f 
 but BergmannJ thinks that the alum of the ancients was a 
 substance which is found native, and which differs greatly from 
 the salt to which this name is now given ; that the species of 
 alum of which Dioscorides speaks, was rather a stalactite which 
 might contain alum, but only in small quantity, and blended 
 with other sulphates. In the time of Pliny, § the best alum 
 
 * Encyclop. method, au mot Lignique. f Voyage de jeune Anacharsis. torn. iv. 
 
 X Bergmann, dc Confect. Alum, opiisc. vol. i. This dissertation is of date 1767. 
 Bcckmaim established the same opinion in the Mem. de Gottingen, 1778. 
 
 § Amailhon, mem. de I'instit, beaux arts, torn. iii. 
 
216 
 
 BERTHOLLET ON DYEING. 
 
 came from Cyprus ; and its species was selected according to 
 the colours for which it was intended. But it appears that the 
 kind appropriated to brown colours was very impure, and con- 
 tained much sulphate of iron, since Pliny distinguished it by 
 the name nigrum, stating that it afforded a black colour with 
 gall-nuts, which circumstance cannot apply to any factitious 
 alum. 
 
 It was in the East that factitious alum began to be known. 
 It is not ascertained at what place, or at what period it was 
 first fabricated. One of the most ancient manufactories was 
 that of Rhodes, a city of Syria, called at the present day Edessa. 
 Thence comes the name of roche alum, which, by a confusion 
 of words, is still given to the crystallized masses of alum. This 
 art was carried in the 15th century into Italy, from which it 
 was spread into Germany and the rest of Europe. 
 
 At Solfatara, near Naples, an aluminous ore is found, under 
 the form of a white earth. The alum is formed in this ore by 
 the action exercised on the argillaceous lavas by the sulphurous 
 acid disengaged from the volcano by heat. 
 
 The purest alum ore is that of Tolfa, near Cevita-Vecchia. 
 It is composed, according to Monnet, who first made its analysis, 
 of 40 parts of sulphur, and 50 of clay, consisting of a mixture 
 of argillaceous and siliceous earths : and besides these, a small 
 quantity of carbonate of potash, and a very little iron. Bergmann 
 also analyzed it, and gave nearly the same proportions. Vau- 
 quelin has still further confirmed this analysis, bestowing on it 
 very great precision. 
 
 The other ores from which alum is extrcicted, are schists 
 more or less pyritous and bituminous. Those which are too 
 pyritous ought to be rejected, because they yield an alum which 
 contains much sulphate or vitriol of iron, of which it would be 
 difficult to get rid. 
 
 The operations by which alum is extracted from its ores, 
 when it is not found ready formed in them, as at Solfatara, 
 have for their object the alumation, the extraction of the alum, 
 and its crystallization. 
 
 These ores, exposed to the air and the rain, may be alunied, 
 for the most part, without being prepared ; but those which 
 contain either too much bitumen or too much sulphur, require 
 to be roasted before being exposed to the action of the ciir and 
 
OF THE CHEMICAL AGENTS. 
 
 217 
 
 humidity ; and in all, the torrefaction accelerates the formation 
 of alum. 
 
 The alumation consists in the combination of oxygen which, 
 uniting to the sulphur, changes it into sulphuric acid, as Lavoi- 
 sier has shown. But usually it is the sulphate of iron which is 
 formed, and the iron oxydizing to a rnaximum by exposure to 
 the air is decomposed by the alumina. There is only the mine 
 of Tolfa, among those which are known, where the acid appears 
 to combine immediately with the alumina. ( Note Z.) 
 
 When the alum is forpied, the ore must be lixiviated, and 
 the liquid be afterwards evaporated till it be in a condition to 
 yield crystals. The first crystals are to be washed, redissolved 
 in a small quantity of boiling water, and the solution poured 
 into peculiar casks, whose staves are then unhooped and sepa- 
 rated, in order to get at the mass of alum which is formed. 
 
 The residuum of the crystallizations, mixed with more or less 
 of the lixivium of the mineral, is evaporated till it be in a s^tate 
 to crystallize ; and the process is carried on by adding the re- 
 siduums of the preceding crystallizations to the new solutions. 
 
 This mixture is the principal cause of the impurity of alum, 
 and of the differences which exist among its species. 
 
 In the progress of the chemical arts, the fabrication of alum 
 by the direct combination of sulphuric acid and alumina has 
 been discovered. For this purpose, a clay should be selected 
 as free as may be from iron and calcareous earth ; it must be 
 roasted to prepare it for combining with the sulphuric acid. 
 This combination is either made immediately with the acid, or 
 by exposing balls of baked clay to the vapour of the sulphuric 
 acid, in the leaden chamber in which this acid is itself manu- 
 factured. Chaptal has published the details of this process, 
 which he established at Montpellier.* 
 
 This mode of forming alum requires, as we shall see, an 
 addition of potash, or sulphate of potash ; and the salt obtained 
 by this process appears to be peculiarly liable to have an excess 
 of acid. 
 
 Before prosecuting the examination of the preparation of 
 alum, it is proper to determine the nature of this combination. 
 It was at first imagined, that alum was a Scxlt formed simply 
 
 * Mem. de racadcmitj, .17oG. 
 
218 
 
 BERTHOLLET ON DYEING. 
 
 by the combination of sulphuric acid and alumina; whence 
 Bergmann recommended to saturate the excess of sulphuric 
 acid which is usually found in the lixivium of alumed earth 
 with a pure clay, instead of the potash or putrefied urine 
 (naturally charged with ammonia) which is commonly added. 
 But Chaptal observed,* that if the acid lixivium be boiled 
 with baked or raw clay, the solution is but slowly made, and 
 after a long ebullition. If the lixivium be filtered, when it 
 appears to be saturated, it lets fall, on cooling, a large propor- 
 tion of the clay which it had dissolved ; and if in this state the 
 solution be concentrated, the clay separates, forming a preci- 
 pitate which prevents all crystallization.'* From this observation 
 we may conclude, that potash or ammonia must enter into the 
 composition of alum. Descroizilles asserted, that the potash 
 did not contribute to the crystallization of alum by the satu- 
 ration of the acid, but by its combination ; and he found, on 
 trial, that sulphate of potash could produce the same effect. 
 Chaptal had come to the same result, and established this prac- 
 tice in his factory. Lastly, Vauquelin made an exact analysis 
 of alum, and discovered that it contained, necessarily for its 
 crystallizing, sulphate of potash or ammonia, or both at the 
 same time. He estimated the amount of sulphate (of potash) 
 present in alum, drawing from his observations this inference, 
 that whenever crystals of alum are obtained from an earthy or 
 stony substance, by means of sulphuric acid, that substance 
 contains potash. It has been seen, that the ore of Tolfa natu- 
 rally contains carbonate of potash. Some other ores may be 
 in the same condition. The wood-ashes formed in their roast- 
 ing, supply them likewise with potash and sulphate of potash. 
 Hence it is not surprising that alum may be obtained without 
 the addition of potash, or putrefied urine, to furnish the ammo- 
 nia. Bergmann remarks, that the latter addition gives rise to 
 an alum which alters the colours. It is not known whether it 
 be by too large a proportion of sulphate of ammonia, or by the 
 mixture of some other hurtful substance, that alum may acquire 
 this bad quality. 
 
 It may be remarked, that Bergmann had himself discovered,f 
 after his first work, not only that it was not for the absorption 
 
 * Mem. dc racaderaic, 1 
 
 f De pktina. § Opusc. vol. ii. 
 
OF THE CHEMICAL AGENTS, 
 
 219 
 
 of the excess of acid that potash or ammonia was necessary to 
 the formation of alum, but that they were still efRcacious when 
 in the state of sulphate. 
 
 It ought not, however, to be thence concluded, that the effect 
 is entirely the same, whether potash be employed, or sulphate 
 of potash. By the first, the requisite saturation of the acid, 
 when it is in excess, is greater, and consequently the production 
 of alum ought to be more considerable, if enough of alumina 
 be present. Whenever, therefore, there is an excess of acid, 
 but a defect of potash or alumina, the advice of Bergmann may 
 probably be followed with advantage, namely, to add alumina, 
 and at the same time a sufficient quantity of potash. To accom- 
 plish this twofold object we may employ, as Vauquelin points 
 out, the residuum of the distillation of nitrate of potash by clay, 
 which may be particularly adapted to the fabrication of alum 
 by means of sulphuric acid. 
 
 In the prices of the alums of commerce there is a considerable 
 difference, and that of Rome is generally preferred for colours 
 that are to be lively and clear. By analysis, therefore, must be 
 discovered what are the differences which distinguish alums from 
 one another. 
 
 Vauquelin has brought to the analysis of alum the precision 
 cuid accuracy which characterize his researches.* On decom- 
 posing alum by potash,Jts ammonia is disengaged. On the other 
 hand, by decomposition with ammonia, evaporation of the liquid, 
 and drying the residuum strongly, the sulphate of potash is 
 obtained by itself. By this means Vauquelin has ascertained 
 that alum contains nearly 7 per cent, of the sulphate of potash 
 or of ammonia; and this quantity is usually divided between 
 both of these sulphates. (Note AA.) 
 
 He has recently examined five kinds of alum taken from dif- 
 ferent factories. He determined the proportion of acid which each 
 contained, by precipitating the sulphuric acid with barytes, and 
 comparing the weights of the precipitates. He had previously 
 precipitated the alumina by ammonia, and subjected it to a 
 strong desiccation. 
 
 It results from his experiments, that these five kinds of alum, 
 among which was the alum of Rome, afforded proportions almost 
 
 * Ann. de chimie, torn. xxii. 
 
220 
 
 BERTHOLLET ON DYEING. 
 
 rigorously the same ; and that the quantity of iron which is 
 found, for example, in that of Liege, of good quality, is nearly 
 the same as vdiat he obtained from Roman alum. Hence he is 
 led to believe, that it is only from a prejudice that the last con- 
 tinues to be preferred; and if a proportion of iron which can 
 do harm be present, he recommends to get rid of it by prussiate 
 of potash. 
 
 We shall deviate a little from the consequences to which the 
 experiments of this great analyst seem to lead. 1. We have 
 examined alums, particularly artificial ones, which contained un- 
 doubtedly a pretty considerable excess of acid, for they left, 
 after their crystallization, a very acid liquor. What Vauquelin 
 has found in the five specimens, four of which had been sent by 
 the manufacturers themselves, and were consequently choice 
 samples, does not authorize the conclusion, that all the alums in 
 the market have a like proportion of acid. 
 
 2. We have mixed with a solution of the alum of Liege, 
 which appeared to be very pure, a little gallic acid ; and a simi- 
 lar test was applied to the Roman alum. The first assumed a 
 black hue, and the second did not change. Analysis would pro-" 
 bably have pointed out but a slight difference ; but this slight 
 difference is sufficient to produce an alteration on lively colours, 
 for which, especially, a severe choice is requisite. 
 
 After submitting this alum to crystallization, in which the 
 first formed crystals were taken, the solution of these crystals 
 was no longer effected by the gallic acid, so that it then presented 
 properties completely analogous to those of Roman alum. 
 Bergmann had already observed this efiect of a careful crystalli- 
 zation, which he recommended. 
 
 With regard to the iron present in alum, and which may 
 exist in considerable proportion when it is crystallized with 
 little care, Monnet had formerly observed, that the sulphate 
 of iron could be entirely separated by crystallization ; on the 
 other hand, Leblanc has made mixed crystals of sulphate of 
 iron and sulphate of alumina, {sulfate d'alum.) These facts 
 would seem to be reconcileable, by the consideration of the 
 state in which the iron exists. When highly oxydized, as it 
 undoubtedly is in the lixivia of alum ore, it requires a great 
 excess of acid to be susceptible of solution, and the oxyde must 
 precipitate, as we shall afterwards see, during the evaporation 
 
OF THE CHEMICAL AGENTS. 
 
 221 
 
 and crystallization, or be retained in the uncrystallizable resi- 
 duum. But if a little oxydized sulphate be mixed with the 
 sulphate of alumina, and if crystallization take place immedi- 
 ately, the iron no longer requires in this case an excess of acid. 
 It may thus be placed in circumstances which allow it to form a 
 combination. 
 
 To recapitulate : We conceive that, in the manufacture of 
 alum, matters should be so managed as to leave no excess of 
 acid, and to avoid those additions of uncrystallizable residuums, 
 which it is proper to treat separately, according to Bergmann's 
 advice, whether it be for extracting their salts, or for making an 
 alum out of them, which afterwards requires more care for its 
 purification, or an alum intended for purposes where it is not 
 needed to be pure. In the second place — The crystallization 
 should be so conducted that the purity of the salt shall not be 
 affected. Consequently, it should not be suffered to condense 
 in great masses, but have a residuary liquid that may retain 
 what would affect the qualities required in the combination. To 
 accomplish this object, the crystallizations might be reiterated, 
 and all the residua treated separately. 
 
 It appears to us that this art is improving progressively, as 
 the manufacturers are becoming more enlightened in the conduct 
 of their operations, and that there will soon be no need of having 
 recourse to Roman alum. 
 
 Those who require alum need not make a selection in employ- 
 ing it for sombre hues ; but they should be very nice with regard 
 to lively and clear colours. Instead of analysis, which requires 
 time and practised skill, we propose to them, 1. To crystallize 
 a portion of the alum which they are to use; if the residuum be 
 perceptibly more acid, this alum might modify the colours by its 
 excess of acid : 2. To mix a little of the infusion of gall-nuts 
 with the solution of alum ; although, by its own colour, this 
 infusion may be less proper for this trial than pure gallic acid, it 
 will point out sufficiently well if the alum contains an injurious 
 quantity of iron. In this case, the alum may be purified by 
 one crystallization, leaving sufficient (liquid) residuum. 
 
 When an exact analysis of alum is wished to be made, we must 
 not lose sight of the difference which, according to the means 
 employed, exists in the insoluble precipitate, from which the 
 proportion of alumina is to be determined. 
 
222 
 
 BERTHOLLET ON DYEING. 
 
 If the precipitate be made by means of a carbonate, it retains 
 a considerable proportion of the acid, and even of the alkaline 
 base ; for on dissolving it in nitric or muriatic acid, alum is ob- 
 tained by crystallization. The best agent is ammonia ; but it is 
 difficult to deprive this precipitate sufficiently of sulphuric acid, 
 so as not to produce a precipitate of sulphate of barytes, when 
 its solution in nitric or muriatic acid is mixed with a solution of 
 a barytic salt. 
 
 Another circumstance impairs the precision of these compara- 
 tive determinations. When the solution of alum is very dilute 
 the alumina retains water, which it does not give entirely up at 
 a very strong heat ; but when it is concentrated, the precipitate 
 which it affi)rds abandons the water much more easily, according 
 to the observation of T. de Saussure.* Hence, from the cir- 
 cumstances of the precipitation, and the degree of heat at which 
 the precipitate is dried, there may exist great differences in its 
 valuation. 
 
 According to Bergmann, 100 parts of sulphate of alumina 
 (alum) contain 18 parts of alumina. T. de Saussure reduces this 
 quantity to 0.09, and Vauquelin, in his last analysis, to 0.085. 
 
 Lime and the alkalies, mixed in certain proportions with the 
 solution of alum, cause this salt to take a cubical form. Sieffert 
 appears to have first described this variety of alum.f Leblanc 
 has made interesting observations on the crystallization of this 
 salt, not yet analyzed by chemists. It must have the acid 
 properties in a less degree than ordinary alum, as Vauquelin 
 thinks, and it would appear, that from the stronger action of the 
 alkaline base on the acid, this salt would give up the alumina 
 more readily to the colouring particles, since alkali is commonly 
 added to the solution of alum for precipitating their lakes. 
 
 According to Bergmann, 30 parts of water are required for 
 dissolving one of alum ; 3 parts of hot water are sufficient. 
 
 We have remarked, that in several woollen dyes tartar was 
 added, which had the property of moderating the action of alum 
 on the filaments, without attempting to explain how it impaired 
 
 * Journ. de Phys. torn. lii. 
 
 t SiefFert's Versuclie mit einheimischen Faibe Materieii, &c., 1775. Sieffert quotes a 
 dissertation on cubical alum, which he printed in the " Edinburgh Magazine." For obtain- 
 ing this alum, he prescribes the mixture of 12 parts of alum with one of quicklime slaked 
 in the atmosphere,^dissolving this mixture in boiling water, and evaporating gently. 
 
OF THE CHEMICAL AGENTS. 
 
 223 
 
 its energy. Bancroft observes, that the dyers indeed frequently 
 omit the tartar, diminishing at the same time the usual proportion 
 of alum. 
 
 Linen and cotton have less disposition to combine with alu- 
 mina than animal substances. Hence, a small proportion of soda 
 or potash is commonly added, which must favour, as has been 
 said, the decomposition of the alum. 
 
 This method is not sufficient for qualifying alum to become a 
 mordant on printed goods. The solution which contains the 
 alumina must be concentrated, without having crystals formed in 
 it. The acetate of alumina has not only this advantage, but it 
 possesses likewise another, dependent on the acetic acid, which 
 serves as the solvent. This acid acts only by a weak affinity, 
 and consequently retains the alumina more feebly than the sul- 
 phuric acid; and in the drying, to which goods impregnated 
 with the mordant are subjected, its volatility makes it fly off*, so 
 that these goods do not carry into the bath an acid which might 
 injure the colour. These advantages render the acetate of alu- 
 mina a very fit substitute for the ordinary aluming in several 
 cotton dyes, accommodated to the improved process of calico 
 printing ; but acetic acid scarcely effects a solution of alumina, 
 as it exists in clays. Their force of cohesion is too great an 
 obstacle for the weakness of the acid to overcome. It is by 
 means of the acetate of lead that an exchange of bases is pro- 
 duced, which we shall have occasion to examine. Hence the 
 preparation of acetate of alumina amounts to a price which 
 does not permit its use in several dyes, till a mode be got of 
 preparing this combination less expensively. The properties of 
 acetate of alumina led us to believe, that it might be substituted 
 with success for alum in the dyeing of wool. We have made 
 trials with madder ; but the cloth took a less intense colour, 
 without our being able to point out the cause of this result, 
 dependent probably on some circumstance which we overlooked. 
 (See Note D.) 
 
 Alumina dissolves pretty copiously in potash and soda, espe- 
 cially by calcination. Macquer was much occupied with this 
 solution, in order to employ it in dyeing. But as the alkalies 
 possess the property of dissolving colouring substances, and of 
 abstracting them from the stuffs on which they are fixed, they 
 
224 
 
 BERTHOLLET ON DYEING. 
 
 do not seem fit to serve as solvents of alumina. The experi- 
 ments of Haussmann, however, prove that this mordant may be 
 employed in some circumstances with advantage. (Note BB.) 
 
 CHAPTER III. 
 
 Of the Sulphate and some other combinations of Iron, 
 
 The sulphate, or vitriol of iron^ martial vitriol, green copperas, 
 is not a uniform and identical combination. It varies, not only 
 by the admixtures which may be present, but also by the state 
 of the oxyde of iron, whence very different effects may result 
 from its action. 
 
 The sulphate of iron may be directly made from iron and 
 sulphuric acid diluted with a certain quantity of water ; and a 
 combination may thereby be obtained, possessing determinate 
 qualities. But the low price of this article rarely allows of this 
 manufacture being conjoined with that of sulphuric acid. 
 
 Sulphate of iron is found native in coal-mines, in the cavities 
 of pyritous mines, and in schists. But the most part of what is 
 employed comes from the martial pyrites, or natural sulphurets 
 of iron. 
 
 These substances are composed of iron, sulphur, alumina, 
 siliceous earth, and sometimes calcareous earth, in different pro- 
 portions. The formation of the sulphate of iron in these 
 minerals is effected by exposing them for a long time to the 
 action of air and moisture, or by roasting them in the open air, 
 and leaving them afterwards exposed to its action. This opera- 
 tion must sometimes be reiterated. The sulphate that is formed 
 is extracted by lixivia1:ion and evaporation. 
 
 The iron in the native -sulphurets of pyrites is oxydized, for 
 when they are exposed to the action of fire in a retort, sulphu- 
 rous acid is evolved, which does not happen with the sulphurets 
 with the metal. It is de-oxydized in this operation, and the 
 residuum is a pure sulphuret. 
 
 Sulphate of iron is also formed in the mineral waters which 
 hold copper in solution, after it is precipitated by iron. This 
 solution, which retains a little copper, is thereafter cr} stallized. 
 
 The sulphate of iron of Goslar contains commonly a little 
 
OF THE CHEMICAL AGENTS. 
 
 225 
 
 zinc, and that of Hungary and Saxony a little copper.* The 
 sulphates of England and France are purer. They contain, 
 however, sometimes alum, especially those of France. 
 
 Sulphates free from copper or alum would be formed, if the 
 precaution were taken of keeping fragments of iron in the 
 boiler, which serves for evaporation, as Monnet recommends ;f 
 for iron slightly oxydized has the property of precipitating 
 copper and the base of alum. The superiority of English 
 vitriol seems to be owing to this precaution. The same practice 
 is also observed in two manufactories in the neighbourhood of 
 Alais.J The zinc alone would not be precipitated. But it is 
 rarely found, and only in small quantity, in the sulphates of 
 iron. 
 
 The copper which exists in several kinds of sulphate of iron 
 is not injurious to the black dyes, in which this metallic salt is 
 principally employed ; but for other purposes, it must be got rid 
 of. This is easily effected, by keeping for some hours in a cold 
 solution of this salt, plates of iron, on which the copper preci- 
 pitates. But this operation could not be performed by crystal- 
 lization, because, according to the observation of Monnet, the 
 sulphate of iron and that of copper form a compound salt that 
 cannot be thus separated. 
 
 Alum is probably more injurious to black than copper is ; for 
 when a black stuff is boiled with alum, it destroys the colour by 
 dissolving it. 
 
 The sulphate of iron varies in its properties according to its 
 state of oxydation. 
 
 It is almost colourless when its metal is very slightly oxydized, 
 or in the condition of black oxyde. It assumes a red colour 
 when the iron is much oxydized, constituting a red oxyde. 
 Proust, who directed our attention particularly to the two states 
 of iron, and to their distinctive properties, regards them as two 
 fixed terms of oxydation, between which there is nothing inter- 
 mediate. We cannot adopt, in this respect, the opinion of this 
 chemist, whose delicate and numerous observations have contri- 
 buted so much to the advancement of the science. As the 
 causes, however, which may produce the oxydation or de-oxyda- 
 tion of this iron, make it usually pass from a very advanced 
 
 * Mineralogy of Kirwan. f Traitd de la vitriolisation. 
 
 X El^mens de chimie de Chaptal, torn. iii. 
 Q 
 
226 
 
 BERTHOLLET ON DYEING. 
 
 degree of oxydation to another adjoining the lowest degree, we 
 neglect this consideration, and conform usually in our explana- 
 tions with the opinion of Proust. (Note CG.) 
 
 When the solution of slightly oxydized iron is exposed to the 
 air, it becomes gradually turbid, and lets fall a yellow precipitate. 
 If the effect be complete, crystals are no longer obtainable by 
 evaporation, but an extract is got, which has a great excess of 
 acid. Highly oxydized iron then requires an excess of acid for 
 its solution ; and when it is in this state, the sulphuric acid has 
 much difficulty to dissolve a smaller quantity of it, than if it is 
 in the metallic form. By the decomposition of water which 
 occurs in the latter case, it can take only the state of black 
 oxyde. If the crystals of the sulphate of iron be left exposed 
 to the air, they lose their green colour, becoming dull and yel- 
 lowish. Their solution now yields only a salt with excess of 
 acid, and an insoluble yellow substance remains. It is obvious, - 
 therefore, that in order to preserve the sulphate of iron or its 
 solution in its primitive state, air must be excluded. 
 
 The precipitate now spoken of, is a salt with excess of oxyde. 
 By means of an alkali, the acid may be abstracted, when merely 
 a red oxyde remains. 
 
 If iron be put into a solution of the highly oxydized sulphate, 
 a yellow precipitate is deposited, which is also a salt with excess 
 of oxyde, and the solution resumes the state of green sul- 
 phate. Hence appears the utility of adding iron in the prepa- 
 ration of the sulphate. It is thus obtained in the state for 
 forming crystals, and those uncrystallizable residuums called 
 mother waters are avoided. 
 
 The sulphate which contains the black oxyde is in a much 
 greater state of saturation, and we have seen that gallic acid 
 could not separate and precipitate this oxyde from the sulphuric 
 acid. It is not to be doubted, then, that it exerts a far more 
 energetic action on the acid, than when it is much oxydized. 
 
 In the precipitates produced by the alkalies, from the solu- 
 tions of both sulphates, characters appear which depend on this 
 difference of action. The little oxydized sulphate affords with 
 the alkalies greenish precipitates, which retain a greater pro- 
 portion of acid in like circumstances ; and even when the sul- 
 phate is highly oxydized, its precipitates are red, and do not 
 retain any acid. If we treat with a concentrated alkali the 
 
OF THE CHEMICAL AGENTS. 227 
 
 green precipitate obtained from the slightly oxydized sulphate, 
 its acid is removed, and it becomes grey or black. On exposing 
 it to the air, it continues to oxydize, passing to yellow. It then 
 grows red, by the action of an alkali which seizes its acid. 
 
 What we have now advanced concerning the difference which 
 distinguishes the green sulphate from the red sulphate, must 
 be applied to all the solutions of iron in the acids. The whole 
 of them form a more intimate combination with the black oxyde 
 than with the red. They exhibit, besides, differences depend- 
 ent on the energy of the acid. Thus, muriatic acid dissolves 
 highly oxydized iron more easily than the other acids. It is 
 true, that if it contains an excess of oxygen, a portion of the 
 acid forms chlorine, according to the observation of Fourcroy« 
 Iron produces also in the precipitation of highly oxydized mu- 
 riate, a yellow precipitate, which owes this colour to the acid 
 remaining combined with it. But it may be supposed, that 
 highly oxydized muriate of iron would be less proper for black 
 dyes than the sulphate, because it would retain with more force 
 the oxyde which must enter into the formation of the black 
 molecules. 
 
 Acetate of iron is employed for printed calicoes, and in gene- 
 ral for black colours in linen and cotton, for the same reasons 
 which make acetate of alumina be preferred. But we need not 
 have recourse to so costly a process. Acetic acid dissolves iron 
 directly ; and to have it in the most oxydized state, fragments 
 of the metal must be kept a long time in good vinegar. The 
 object would not, however, be accomplished, were the solution 
 left always over the iron. For we have seen, that in the me- 
 tallic state it precipitates a highly oxydized salt. The liquor, 
 then, is to be decanted, and kept in a vessel where it may have 
 contact of air, so as to pass to the highly oxydized state. This 
 decantation ought to be made whenever the solution is com- 
 pleted. 
 
 For the ordinary black dyes, where there is no need of so 
 concentrated a solution, vinegar is not employed, but a less 
 expensive acid is frequently formed with different vegetable 
 substances, for example, with the bark of the birch tree. To 
 the vessel in which this operation is executed, the name of 
 tonne au noir (black cask) is given. This object would be 
 
 Q 2 
 
228 
 
 BERTHOLLET ON DYEING. 
 
 better accomplished, if the precaution were taken to keep the 
 solution, after it is made, out of contact of iron. (Note DD.) 
 
 In explaining the action of astringents, we have mentioned 
 the observation of Proust, who found that the highly oxydized 
 sulphate was brought back to the state of the little oxydized, 
 by the action of astringents, and even of other colouring sub- 
 stances ; whence he concludes, that it is right to employ in 
 dyeing only the highly oxydized sulphate. This conclusion 
 appears to us just, when black dyes are in question, with the 
 exception, perhaps, of the dyeing of silk. It should even be 
 applied to all solutions of iron used for this purpose. But the 
 same thing does not hold true when solutions of iron are made 
 use of for other colours. For example, in the manufacture of 
 printed goods, in order to obtain the colour called rusf, yellow, 
 sulphate of iron is made use of, or, still better, the little oxydized 
 acetate, formed by the decomposition of acetate of lead with 
 sulphate of iron. The salt with excess of oxyde, which is 
 formed in the cloth, lias an agreeable yellow colour, which, by 
 the contact of alkalies, passes to grey ; after oxydizing in the 
 air, it becomes red. 
 
 The shades of yellow which may be given to cotton by means 
 of iron, with which we shall be elsewhere occupied, prove that 
 it is not the oxyde of iron alone which serves to give colour in 
 this instance, but that the precipitate retains a portion of the 
 acid ; for it is always to an acid that the oxyde of iron owes 
 this colour. 
 
 The changes of colour must never be lost sight of, which 
 result from the different oxydations of iron in the dyes, where 
 it is used for other colours besides black, as Chaptal has shown. 
 Thence the precautions which must be taken, in order that this 
 oxydation shall go on uniformly during the operation itself, and 
 that the stuff be exposed to it in an uniform manner. 
 
 There is one operation for which the iron should be, on the 
 contrary, at the lowest stage of oxydation : this is the solution 
 of indigo, by means of the sulphate of iron, precipitated by an 
 alkali. Slightly oxydized iron gives solubility to the indigo, 
 by carrying off the oxygen, which renders it insoluble. The 
 oxyde of copper produces a contrary effect, affording oxygen to 
 indigo deprived of it. This renders the sulphate and acetate 
 
OF THE CHEMICAL AGENTS. 
 
 229 
 
 of copper proper for the reserves, that is to say, for preserving 
 the parts of the cloths to which they are applied, from the fixa- 
 tion of the indigo, which by resuming oxygen, can no longer 
 combine with the stuff". 
 
 The differences of oxydation of the metallic substances em- 
 ployed in dyeing, and the effects flowing from them, merit the 
 greatest attention ; and by observing them with more care than 
 has hitherto been done, several operations will be rendered 
 methodical {regularisees), whose results are regarded as capri- 
 cious, becoming at the same time more uniform and more 
 advantageous. 
 
 CHAPTER IV. 
 Of Sulphate of Copper. 
 
 The sulphate of copper, blue vitriol, vitriol of Cyprus, blue 
 copperas, is not much employed in dyeing ; but it is of great 
 service for forming ^ the colours used, particularly for painted 
 papers ; and hence its fabrication, and the means of obtaining 
 it pure, have become interesting to the arts. 
 
 Different methods are employed for making sulphate of 
 copper. The native sulphuret, or copper pyrites, or mate, 
 resulting from the fusion of copper ore, which is a combination 
 of copper and sulphur, is calcined, and the product of the cal* 
 cination is left to effloresce. The copper thus deprived of a 
 portion of its sulphur oxydizes, and the sulphur is converted 
 into sulphuric acid. The salt that forms is then extracted, and 
 crystallized. A second process, analogous to the preceding, 
 consists in calcining a mixture of copper and sulphur, in expos- 
 ing the sulphuret in like manner to effloresce, lixiviating the 
 salt, and crystallizing it. 
 
 Since the (modern) fabrication of sulphuric acid has allowed 
 it to be employed for several purposes to which its former price 
 was an obstacle, sulphate of copper has been formed, by dis- 
 solving the metal, or its oxyde, in sulphuric acid. To this sul- 
 phate it is objected, that for some purposes it contains an excess 
 of acid; but it would be difficult to avoid this inconvenience. 
 
 There are some native waters which contain sulphate of 
 copper. 
 
230 
 
 BERTHOLLET ON DYEING. 
 
 The principles to be attended to in purifying the sulphate 
 of copper deserve to fix our attention, because they are appli- 
 cable to all the metallic solutions, and may explain several 
 phenomena observed in the chemical action of different bodies. 
 
 The insolubility of any compound that is formed, should be 
 considered as a cause of its formation, v^henever the elements 
 that can produce it are brought together. Thence may be 
 deduced, as we have said, the cause of the pre.cipitations and 
 changes of base, v^hich occur in the reciprocal action of the acid 
 and alkaline substances. 
 
 The same effect takes place in the reciprocal action of metal- 
 lic oxydes and acids. The oxydes can seldom produce neutral- 
 ization in combining with the acids, when their combination 
 retains solubility ; but these combinations require a greater or 
 less excess of acid, a condition which varies according to the 
 state of oxydation. Thus we have seen, that the highly oxyd- 
 ized sulphate of iron requires a considerable excess of acid, 
 which the lowly oxydized sulphate does not. If the excess of 
 acid be removed, the highly oxydized salt, which is insoluble, 
 precipitates. 
 
 It thence results, that when a metal is in solution, and when 
 it needs an excess of acid in order to preserve this state, the 
 addition of another oxyde, which shall require a less consider- 
 able excess of acid, will cause the first to fall down in the form 
 of an insoluble salt ; and if the second needs an excess of acid, 
 although less considerable, it will be precipitated in its turn 
 by an oxyde which is soluble without excess of acid, or which 
 requires less of it. 
 
 For the same reason, different effects will be obtained, by 
 varying the oxydation of a metal, and thereby the solubility of 
 its combinations. Thus we have seen, that iron precipitated 
 the highly oxydized sulphate, forming a combination which 
 preserves its solubility without excess of acid. In these circum- 
 stances two combinations are produced, one which remains in 
 solution, and another which is insoluble. The action even of 
 the alkalies is usually limited to the production of a similar 
 effect on metallic solutions. 
 
 Gay Lussac, who established this point of theory,* supported 
 
 * Annales de chimie, torn. xlix. 
 
OF THE CHEMICAL AGENTS. 
 
 231 
 
 it by several interesting facts. We shall confine ourselves to 
 an account of the observations v^hich relate to the preparation 
 of the sulphate of copper and the sulphate of iron. 
 
 When the iron is highly oxydized, it is precipitated by the 
 oxyde of copper; when shghtly so, the reverse takes place. 
 Here are two consequences of great importance, because they 
 are susceptible of frequent applications to the arts: the first is, 
 that the whole iron can be separated from a solution of copper ; 
 the second, that the whole copper in a green solution of iron 
 may be removed. 
 
 Several colours are prepared with the sulphate of copper, 
 but the iron which it always contains, and which has not hitherto 
 been completely separated, alters their shade. If, for accom- 
 plishing this object, the iron be strongly oxydized by means 
 of nitric acid, or stiil better, by chlorine, it will be precipitated 
 entirely from the sulphate of copper, by pouring into it a suffi- 
 cient quantity of potash, heating and agitating the liquor very 
 well. 
 
 " The green sulphate of iron is pretty frequently employed in 
 the arts, and in several cases it is of consequence to free it from 
 all the copper. Iron has indeed the property of separating it, 
 but it appears to do so but very imperfectly, and in a long time. 
 It will be undoubtedly more advantageous to employ potash, 
 pouring a little of it into the green sulphate. The precipitate 
 of black oxyde of iron will soon return into solution by agita- 
 tion ; and it will throw down at once the oxyde of copper, and 
 the red oxyde of iron, if either exist in the green sulphate." 
 
 CHAPTER V. 
 
 Of Verdigris, or the Acetate of Copper. 
 
 Formerly verdigris was prepared only in Montpellier and 
 its neighbourhood. The process followed there consisted in 
 causing the stalks of grapes to ferment along with the vinasse 
 (wine-lees), then plates of copper were arranged layer upon 
 layer with these stalks, and the whole was left together for some 
 time. On withdrawing the plates, they were set aside in a 
 corner of the cellar, where they were further sprinkled with 
 
232 
 
 BERTHOLLET ON DYEING. 
 
 wine-lees ; and lastly, the verdigris formed by this operation 
 was scraped off. 
 
 This process has been improved and rendered more economical 
 in these latter times, by substituting for the stalks the squeezed 
 husks of grapes, previously subjected to the acetous ferment- 
 ation, thus suppressing the vinous matter with which they had 
 formerly bedewed the stalks. Chaptal has described the details 
 of this process.* 
 
 At Grenoble, ready-made vinegar is employed, with which 
 the plates of copper are moistened. The verdigris prepared in 
 these two methods differs in some of its properties. 
 
 Chaptal has made a comparison of them.f The first is 
 unctuous, pasty, little soluble in water ; it is preferred for the 
 purposes of painting. The second is drier, of a more decided 
 greenish blue colour, and more soluble in water. It produces 
 better effects in dyeing ; giving more vivacity to the colours, 
 and requiring a smaller quantity to compose the mordants. 
 
 This difference depends upon their composition. The first con- 
 tains, in particular, uncombined oxyde of copper, or carbonate 
 of copper, and the second approaches to the state of an acetate. 
 
 In either preparation of verdigris the copper is reduced to an 
 oxyde by the concurrent actions of atmospheric air, and the 
 acetic acid employed or formed. But as copper vessels are 
 much used, it will be proper to dilate a little further on the 
 manner in which the acids act on this metal. 
 
 For dissolving copper in the acids, it must, like other metals, 
 be combined with oxygen or reduced to an oxyde. Hence it 
 must either attract oxygen from the atmosphere, or obtain it 
 from the acids, or from the decomposition of water by the co- 
 operation of another force ; for it has not this property of itself. 
 
 The vegetable acids cannot yield oxygen to copper ; but the 
 action which they exercise upon it so favours its combination 
 with oxygen, that it attracts it speedily from the atmospheric 
 air, and is reduced to an oxyde so as to become soluble in the 
 acid liquid. This must not be hot, in order that the copper 
 may attract oxygen from the atmosphere. The vegetable acids 
 do not attack copper while they are hot, and the same thing 
 takes place with oils and other substances which act on this 
 
 * Mem. de Pinstit. vol, ii. 
 
 t Mem. de Tinstit. vol. i. 
 
OF THE CHEMICAL AGENTS. 
 
 233 
 
 metal, unless there be a portion of copper already oxydized ; 
 for in this case it dissolves readily, whatever temperature the 
 liquor may have. Hence we perceive the necessity of never 
 allowing liquors that can corrode this metal to cool in copper 
 boilers, and of taking care to keep them always very clean, so 
 that no oxyde is formed on their surface. 
 
 Nitric and nitro-muriatic acids, though diluted with water, 
 afford oxygen to copper, especially at a boiling heat. Hence 
 they must dissolve a portion of this metal in the baths into 
 which, for example, solution of tin enters, unless the boiler be 
 tinned with care. This effect may be diminished, however, in 
 consequence of the nitric acid exerting its action on the vege- 
 table, and more particularly the animal substances present in 
 the bath, and from its being saturated by the ammonia that is 
 generated. 
 
 In verdigris, copper is reduced to the state of oxyde, and is 
 combined with a more or less considerable proportion of acetic 
 acid. When the oxyde is completely saturated with this acid, 
 it is wholly soluble in water, and forms by evaporation rhom- 
 boidal crystals of a blue colour, which attaching themselves to 
 little wooden rods, give origin to those groups called crystal- 
 lized verdigris, or crystals of Venus, There is this difference, 
 then, between this salt and verdigris, that in the first the oxyde 
 of copper is completely saturated with acetic acid, forming an 
 acetate of copper ; while, in verdigris, there is but a variable 
 proportion of the oxyde of copper in the condition of an acetate. 
 This saline portion can be separated by solution in water. 
 There remains, in this case, only an oxyde of copper, or a salt 
 with excess of oxyde, which dissolves readily in acetic acid, and 
 thus is converted to the saline state. Sometimes the verdigris 
 contains but very little acetate ; sometimes, on the contrary, it 
 contains scarcely one-fourth of its weight of oxyde of copper 
 uncombined ; in which circumstances consists, as we have said, 
 the difference which distinguishes the verdigris manufactured 
 at Grenoble from that of Montpellier. (Note EE.) 
 
 Clegg, in attempting to substitute for verdigris in the black 
 dye an ingredient less expensive, says, that he observed that 
 the copper of verdigris threw down, in the state of an oxyde, 
 the iron of the sulphate of iron held in solution along with 
 astringent matters. Regarding verdigris, therefore, as a pre- 
 
234 
 
 BERTHOLLET ON DYEING. 
 
 cipitant of iron, he sought to substitute for it other substances 
 capable of precipitating this metal from its solvents. He first 
 tried the alkalies ; and his experiments, which on the small 
 scale appeared to succeed, had no success on the great. In 
 fact, the alkalies do not precipitate the combination of iron and 
 the astringent principle : but they unite along with it, giving 
 it a reddish hue. He next ascertained, by several trials, that 
 the verdigris might be perfectly replaced by a mixture of sul- 
 phate of copper and potash. He prescribed the dissolving the 
 sulphate of copper, and adding to it solution of potash, till the 
 blue colour disappeared, that is to say, till the whole of the 
 copper was thrown down. For this purpose a nearly equal 
 weight of sulphate of copper and of alkali is required. He 
 asserts, that the weight of the two together is a substitute for 
 an equal weight of verdigris ; and that this process may be put 
 in practice, especially for hats, the dyeing of which consumes a 
 great deal of verdigris. 
 
 We shall remark on this process, that the oxyde of copper 
 produces in reality a precipitate in a solution of iron blackened 
 by an astringent; but this precipitate is not solely oxyde of iron; 
 it is owing to the black molecules which result from the combi- 
 nation of the oxyde with the astringent principle. This preci- 
 pitation, may, indeed be one mode in which oxyde of copper 
 contributes to dyeing of black; but it is probable that the 
 principal way in which it is useful to this dye consists in forming 
 a blue with logwood, which also enters into it, or a shade betwen 
 green and black, which results from its combination with the 
 astringent ; for we have observed, that it was advantageous for 
 deepening the black to derive it from different colours. It is thus 
 obvious how a verdigris which contains much acetate of copper 
 may produce better effects than one which has a larger propor- 
 tion of unsaturated oxyde, or carbonate. 
 
OF THE CHEMICAL AGENTS. 
 
 235 
 
 CHAPTER VI. 
 Of the Acetate of Lead, or Salt of Saturn. 
 
 The acetate of lead is a combination of lead reduced to oxyde, 
 and of acetic acid. It is usually crystallized in slender confused 
 needles. . 
 
 This salt has a sweet taste, mixed with a little astringency, 
 which has caused it to get the improper name of sugar of 
 saturn. 
 
 Acetic acid out of contact of air does not attack lead in the 
 metallic state. But if the air touches its surface, the lead is 
 gradually oxydized by means of the oxygen which it attracts, 
 and thereby becomes soluble in the acid. As this manner of pre- 
 paring the acetate of lead would be disadvantageous, both because 
 it would take much time, and a large portion of the acid would 
 evaporate, other processes are had recourse to. 
 
 White lead is an oxyde of lead combined with carbonic acid. 
 To form it, the metal in plates is suspended over vinegar in 
 earthen vessels, which are covered with horse dung^ to afford 
 heat for evaporating the vinegar, which exhaling, reduces the 
 lead to an oxyde by means of the air, and then dissolves it. 
 Carbonic acid is evolved at the same time, which precipitates 
 the lead as carbonate. This carbonate, pulverized with much 
 care, constitutes white lead. But a portion of the oxyde is 
 retained by the vinegar, forming acetate of lead, which is merely 
 to be evaporated and purified by a second crystallization. 
 
 The greater part of the acetate of lead is prepared with dis- 
 tilled vinegar, obtained from beer or wine, and with white lead, 
 which being reduced to a very subtile powder, is in the most 
 favourable state for dissolving. 
 
 If no acetate of lead be at hand, it is easy to manufacture it 
 one's self, by dissolving an oxyde of lead in distilled vinegar, 
 and evaporating the solution to the proper point of crystalliza- 
 tion. Different oxydes of lead may be employed. White lead 
 dissolves more easily than the others, except ceruse ; but we 
 must avoid the latter, because it is a mixture of white lead and 
 chalk. Litharge, or semi-vitrified oxyde of lead, may be sub- 
 stituted for white lead ; minium dissolves with more difficulty. 
 
 It would probably be sufficient to dissolve the oxyde of lead 
 
236 
 
 BERTHOLLET ON DYEING. 
 
 in white (pale) vinegar, whose extractive part, by which prin- 
 cipally it differs from distilled vinegar, would do no harm ; 
 but it must be remarked, that the acetate of lead is a compound 
 not uniform in its proportions. Thenard has observed, that 
 the ordinary acetate of lead can still dissolve a quantity of 
 oxyde almost equal to what it already contains, and then it 
 assumes a different form of crystallization. But the new crys- 
 tals are decomposed by simple exposure to air, and a portion 
 of the oxyde is converted into carbonate. On being dissolved 
 in water, they likewise abandon a portion of the oxyde, forming 
 an abundant precipitate ; after which the soluble combination 
 is restored to the ordinary state. 
 
 On repeating this experiment, we have observed that the 
 acetate of lead which we used, reddened the vegetable colours, 
 acting on paper stained with turmeric like feeble acids ; but 
 after being surcharged with oxyde of lead, its solution reddened 
 the tincture of turmeric like alkalies, so that there is here an 
 indication of the alkaline properties which the oxydes exercise 
 on the acids. 
 
 The crystals of acetate of lead usually afford a slight preci- 
 pitate when they are dissolved in distilled water ; which pre- 
 cipitate is owing to carbonate of lead formed at their surface. 
 But they produce, with the waters of -rivers and wells, a much 
 more abundant precipitate, arising from the sulphates and the 
 muriates which are present in these waters, the quantity of which 
 is proportional to that of these salts. The chloride of lead, 
 however, has a certain degree of solubility. 
 
 The acetate of lead is not employed directly as a mordant in 
 dyeing, although it produces an abundant precipitate with the 
 greater number of the solutions of colouring matters ; but its 
 precipitates have sombre and dead hues. The chief use that 
 is made of it, is to procure acetate of alumina. Since the 
 force of cohesion of this earth is opposed to its direct solution 
 in the acetic acid, a mixture of sulphate of alumina is made 
 with acetate of lead. Thus (acetate of) alumina is procured in 
 the liquid state. But the elements of these combinations being 
 placed together, and the oxyde of lead possessing the property 
 of affording an insoluble combination with sulphuric acid, this 
 compound is formed and precipitates, while the alumina remains 
 dissolved in the acetic acid. (See Note D.) 
 
 Accident made known this combination, so important in the 
 
OF THE CHEMICAL AGENTS. 
 
 237 
 
 printing of calicoes ; several useless substances indeed were 
 added to it, till chemistry determined the essential ingredients. 
 
 Certain expert manufacturers imagined, that they should 
 preserve among the ingredients a given proportion of chalk and 
 potash, with the view of absorbing an excess of acid ; but this 
 addition does nothing but throw down, uselessly, a portion of 
 the oxyde of lead, and introduce into the acetate of alumina 
 foreign salts, which may injure the effects that it ought to 
 produce. Experience has proved, that without these mixtures 
 a good preparation was obtained ; hence the only thing to be 
 determined is, the proportions which effect the exchange of 
 base most completely. (Note D.) 
 
 Haussman employed an acetate of tin, formed by decompos- 
 ing the acetate of lead by the muriate of tin ; but this prepara- 
 tion has some disadvantages : — 1. It retains a little chloride of 
 lead ; for this salt has a slight solubility. 2. A triple salt is 
 formed, which contains a great proportion of lead, if the neces- 
 sary proportion of acetate of lead be used. 
 
 CHAPTER VIT. 
 Of the Fixed Alkalies. 
 
 Magnesia, lime, barytes, strontian, and glucina, might indeed 
 be regarded as fixed alkalies, since the whole of them, and some 
 more than potash or soda, possess the property of saturating 
 the acids, and forming with them neutral combinations. They 
 are distinguished, however, by the name of earths, or alkaline 
 earths, in consideration of the solidity and pulverulency which 
 give the idea of an earth ; and the name of fixed alkalies is 
 reserved for potash and soda, which being of great use in dyeing, 
 should be well studied. 
 
 As for ammonia, although it be the most powerful of the 
 alkalies, since, in equal quantity, it exercises in a higher degree 
 the alkaline properties on the acids, its volatility is an obstacle 
 to its use in most part of the operations of dyeing. 
 
 1.-0/ Potash. 
 
 Potash, named vegetable alkali y because it is derived from 
 
238 
 
 BERTHOLLET ON DYEING. 
 
 the combustion of vegetables, is an identical substance. But 
 the state of saturation in which it exists, and the mix- 
 tures confounded with it, considerably diversify its effects and 
 value. 
 
 When its whole alkaline power is to be exerted, it must 
 be deprived of the carbonic acid, with which it is combined in 
 greater or less proportion, and which gives it the property of 
 effervescing with such acids as expel its carbonic acid. With 
 this view it is dissolved and treated with quicklime, which, 
 seizing its carbonic acid, precipitates in the form of an insoluble 
 salt. What is called pure or caustic potash, is thus obtained. 
 It still retains, however, a portion of carbonic acid, to free it 
 from which it must be treated with alcohol. In this case two 
 combinations are formed, the one an alcohol (alcoate) of potash, 
 and the other, which remains dissolved in a portion of water, or 
 which separates in crystals, is carbonate of potash. On expell- 
 ing the alcohol from the former combination, we have pure 
 potash. But this preparation is not wanted in dyeing, except 
 for experiments of research. 
 
 The watery solution of ordinary potash contains also foreign 
 salts, which it may be worth while to separate, as is done for 
 the manufacture -of fine glass. For this purpose, the potash is 
 dissolved in as little water as possible, and the solution is allowed 
 to settle. The salts less soluble than potash, separate in a great 
 measure, and fall down. 
 
 Potash, not saturated with carbonic acid, attracts the hu- 
 midity of the air, and thereby dissolves, forming a liquor called 
 oil of tartar, per deliquium. It also attracts carbonic acid, and 
 in a long period of time acquires the property of crystallizing. 
 Bohn and Monnet had observed this crystallization before its 
 cause was known. 
 
 It should be observed, that carbonate of potash has the pro- 
 perty of crystallizing, before getting the quantity of carbonic 
 acid which can combine with it. When this is the case, it 
 attracts moisture from the air. In the solution, the portion 
 which remains liquid, acts sufficiently on the water to permit 
 the other portion to crystallize. When this water is removed, 
 the crystals exert sufficient force on the water of the atmo- 
 sphere, and attract enough to be reduced to a liquid. It would 
 seem, that the carbonate of potash can assume variable quantities 
 
OF THE CHEMICAL AGENTS. 
 
 239 
 
 of carbonic acid, even when it has no longer the property of 
 attracting humidity. 
 
 These different states of saturation of the carbonic acid de- 
 mand attention, when potash is employed in dyes whose colours 
 may be affected by it, or in which the texture of the stuffs can 
 suffer alterations ; for, in the caustic state, the alkali exerts a 
 greater power of combination with other substances. 
 
 Different names have been given to potash, according to the 
 substance from which it is extracted. It is called salt of tartar y 
 when obtained from the bitartrate of potash, or tartar. To 
 make this preparation, the tartar is wrapped up in paper cones, 
 and is thus exposed to combustion. After dissolving the resi- 
 duum in water, the solution is concentrated by heat, the foreign 
 salts are separated in proportion as they fall down, and by 
 desiccation the potash is procured, which retains much carbonic 
 acid, formed by the destruction of the tartaric acid, at a suffici- 
 ently moderate heat for a great deal of it to remain in com- 
 bination. This potash is very rich in alkali ; but it is very 
 costly. 
 
 The cendres gravelees^ which are the product of the combus- 
 tion of wine lees and vine branches, are also rich in alkali, 
 although the potash is here less pure than that obtained from 
 tartar. 
 
 The potash, known by different names in comm^erce, comes 
 chiefly from the North of Europe, and the United States of 
 America. It is the product of combustion in vast forests, for 
 the wood of which no better use can be found. But this opera- 
 tion not being every where made with the same care, is the 
 main cause of the great differences in the product. According 
 to Linnaeus, the birch or alder is burned with a slow fire ; with 
 the ashes and water a kind of paste is made ; with this paste a 
 range of billets of the pine or fir is covered ; over this range 
 another is laid transversely, covered in like manner with the 
 same paste ; and in this manner the layers of wood and paste 
 are continued, till the pile acquires a considerable height. Fire 
 is now put to it, and when the ashes begin to flow, the pile is 
 overturned, and the ashes in semifusion are beat with flexible 
 rods. They are incrusted by this operation on the logs, and 
 become as hard as stone. 
 
 It is obvious, that by this process the potash must contain a 
 
240 
 
 BERTHOLLET ON DYEING. 
 
 great deal of foreign earth ; but it appears that lime is some- 
 times mixed with it. Home found some of it, chiefly in a 
 species of potash called cassoude, much used by the bleachers 
 in Belgium, and the neighbouring departments. 
 
 So defective a process as the above is not followed every 
 where ; but in some places the ashes are lixiviated, by cover- 
 ing them with water in casks. After some hours, the liquid 
 is run off, new water is poured on, and the operation is re- 
 peated, till the water comes off nearly insipid. The last waters 
 are employed for new leys, as in the lixivia of the plaster rub- 
 bish from which saltpetre is extracted. The waters are sub- 
 sequently evaporated ; the result is black and carbonaceous. It 
 is called salin. This substance, calcined in a furnace, becomes 
 white, and yields a good potash. 
 
 Ashes which have undergone no preparation are also made 
 use of, and principally for leys. What has been said of pot- 
 ashes, may be applied to them. 
 
 The vegetables from which potash is extracted differ much 
 from one another, both in the quantity of ashes which they 
 yield on combustion, and in the proportion of potash found in 
 their ashes. We shall give an outline of the observations which 
 have been made on this subject, because they may guide us in 
 the art of preparing potashes, and in their different applications 
 to the arts. 
 
 It results, from the experiments of Pertuis in particular,* 
 that the herbaceous plants furnish in equal weight, after their 
 drying, much more ashes than ligneous (woody) plants, and that 
 the first contain a larger proportion of alkali ; that the trunks of 
 trees yield less than the branches, and the braches less than the 
 leaves ; but on this subject, as well as on several others relating 
 to vegetation, much mora extensive and exact researches than 
 the above are to be found in a work just published by Theodore 
 de Saussure.-j- 
 
 * Ann. de chimie, torn. xix. 
 
 f Recberches chim. sur la vegetation. We find in this excellent work, observations 
 wbicb occasion some modifications in the explanations which we have given on the change 
 produced by the air on the colouring particles, and the vegetable substances which suffer its 
 action. The author has determined in a more positive manner the circumstances of this 
 alteration. 
 
 Saussure, on exposing extracts and other vegetable substances to the action of the air in 
 closed vessels, found that the volume of the air was not diminished, but that its oxygen 
 
OF THE CHEMICAL AGENTS. 241 
 
 His experiments have placed beyond doubt, that potash, and 
 the other salts which are found in the ashes of vegetables, are 
 not a product of vegetation, but that they proceed from the soil 
 from which they are absorbed, and even from the atmosphere. 
 Consequently, the same vegetables which grow in different soils 
 yield in their combustion a different proportion of ashes, which 
 have different proportions of saline or earthy substances, either 
 soluble or insoluble. The parts of vegetables leave more ashes, 
 as they are subject to a greater transpiration ; because these 
 ashes proceed from the substances which were held in solution 
 in the vegetable juice. Thence the leaves afford more than the 
 bark ; this more than the alburnum ; and the alburnum more 
 than the timber. 
 
 For the same reason herbaceous plants yield much more of it 
 than the woody plants. 
 
 The proportions of the alkalies, or rather of the soluble part, 
 vary in these ashes. The seeds contain most ; the leaves come 
 next ; but when they are young they contain more. The bark 
 has the smallest quantity of it. This quantity is seen to dimi- 
 nish, according as the rain water has dissolved and carried it 
 away. 
 
 The phosphates, which the ashes of vegetables contain, form 
 an important consideration. Saussure has found, that all vege- 
 tables contain the following phosphates : Phosphate of potash; 
 phosphate of potash and lime, soluble like the preceding ; and 
 phosphate of lime, insoluble. As they usually contain carbon- 
 ate of lime, changes of combination take place during incinera- 
 tion. The phosphate of potash is decomposed by the carbonate 
 of lime ; and there is found in the ashes only phosphate of lime 
 or a smaller quantity of the first two com^binations, than what 
 existed in the vegetable. If different vegetable parts be inci- 
 
 was changed into carbonic aeid, extracting its carbon, and combining with it. At the same 
 time, a production of water takes place, by the more intimate combination of the hydrogen 
 contained in this substance with the oxygen which was equally contained in it, and, of con- 
 sequence, the substance contains a larger proportion of charcoal. The effect is therefore 
 comparable, in this respect, to that of a slight combustion. 
 
 His observations, however, even prove that the fact is not general; the c ils absorbed 
 some oxygen. It would appear, that the action of oxygen does not produce uniform effects 
 even on the substances which are not oily. But it will be necessary to distinguish, by new 
 observations, the cases different in the mode, but uniform in the result, which is a pre- 
 dominance of carbon. 
 
 R 
 
242 
 
 BERTHOLLET ON DYEING. 
 
 nerated, a result will be obtained, which is not the mean that 
 would have been got by making the incineration separately. 
 Thus the bean contains phosphate of potash, without carbonate 
 of lime, and no phosphate of lime is found in its ashes. But if 
 it be burned along with the stem, which contains carbonate of 
 lime, there is obtained, instead of phosphate of potash, a much 
 larger portion of phosphate of lime than the incineration of the 
 stem alone would have given. 
 
 From these observations, some results may be drawn useful 
 to our subject, which we abridge with regret. 
 
 1 . For the fabrication of potash, it is more advantageous to 
 collect herbaceous plants, leaves, and small sprigs of trees, than 
 to burn the trunks themselves. 
 
 2. When the ashes are boiled into a condensed ley, in order 
 to extract their potash, the alkali must convert a part of the 
 insoluble phosphate of lime into phosphate of lime and potash ; 
 and the portion of the alkali which enters into this combination 
 becomes inactive, by reason of the saturation which it expe- 
 riences. 
 
 We shall not dwell on the other substances which enter into 
 the composition of the ashes, and of ordinary potash ; because 
 the only matter which is useful and of importance to estimate 
 is the alkaline. We have described, in treating of bleaching, 
 the most exact means of arriving easily at this valuation. If 
 there be an intention, however, of employing potash as an alter- 
 ative or auxiliary, it may be proper to ascertain if it contains 
 much carbonic acid, which its effervescence with acids points 
 out. But a solution of it must be previously made to separate 
 the effect of the potash from that of the carbonate of lime. 
 The quantity of carbonic acid which escapes may be ascertained 
 by verifying the loss of weight experienced by the mixture of 
 potash and acid, whose separate weights had been determined 
 beforehand. 
 
 U.— Of Soda. 
 
 Chemists have given the name mineral to this alkali, because 
 it is often found at the surface of the earth, or in subterraneous 
 cavities. Thus a great quantity of it may be gathered in Egypt 
 in the neighbourhood of lakes, called natron ; a name also given 
 
OF THE CHEMICAL AGENTS. 
 
 243 
 
 to the soda obtained from them. In several parts of Barbary, 
 Syria, Persia, in the West Indies, China, and even in our 
 climates, it is likew^ise found. 
 
 The conditions which determine this production, are, judging 
 from the observations made near the natron lakes,* a mixture 
 of muriate of soda and carbonate of lime, in a moist ground, 
 not too clayey, and a pretty hot temperature. In this case, a 
 slight solution of carbonate of lime is effected, and the causes 
 which favour the efflorescence peculiar to corbonate of soda, 
 determine its separation, while a corresponding portion of 
 muriate of lime infiltrates into the earth. 
 
 The soda thus collected in Egypt is not pure, but contains 
 variable proportions of carbonate of soda, muriate of soda, sul- 
 phate of soda, and of earth, mingled, even when different spe- 
 cimens are taken on the same grounds. 
 
 The greatest part of the soda, however, which is made use of, 
 is the product of the combustion of plants which grow on the 
 sea-shores, and particularly of the salsola soda, Linn. 
 
 The most esteemed comes to us from Alicant. Some is also 
 extracted from the same plant on our maritime coasts, as well 
 as on others. To these sodas, according to the countries and 
 plants from which they are got, different names are given ; 
 such as Rochette, Varech, Salicor, Julia has lately given an 
 interesting description of the culture of the salsola, established 
 in the environs of Narbonne, from which a soda comes, known 
 under the name of Salicor.f 
 
 These sodas differ much from one another in the proportion 
 of carbonate of soda. There are ashes of Varech which contain 
 hardly any of it ; but it is useless to dwell on these differences, 
 because confidence can only be put in the chemical proof, which 
 should be the same as for potash. A good soda, or a carbonate 
 of soda, should be assumed for a term of comparison; because 
 a larger proportion of acid is required to saturate a quantity of 
 soda, than an equal weight of potash. 
 
 Soda is in the state of a carbonate, or most part of it at least 
 is in that state, when plants are incinerated. It crystallizes, 
 retaining much water of crystallization ; but it parts with this 
 
 * M^moire sur I'Egypte. f Ann. de cliimie, torn. xlix. 
 
 R 2 
 
244 
 
 B^lRTHOLLET ON DYEING. 
 
 easily to the air, and falls thereby into efflorescence, with the 
 loss of nearly one-half its weight. 
 
 This difference distinguishes it from potash, which naturally 
 retains, after incineration, only a part of the carbonic acid ne- 
 cessary to its crystallization ; and which, till it be saturated 
 with it to this point, attracts, on the contrary, the humidity of 
 the air ; a difference apparently depending on the stronger 
 affinity which soda exercises on the acids, and on the greater 
 condensation which it produces, particularly on those that are 
 naturally elastic. 
 
 Although the native carbonate of soda crystallizes and dries 
 in the air, it retains, however, weak alkaline properties, and 
 greens the colours that characterize them. But it may take a 
 larger proportion of carbonic acid. The celebrated Klaproth 
 has observed in a species of carbonate of soda, or natron, a 
 proportion of carbonic acid, nearly double that obtained from 
 the ordinary carbonate. Hence its alkali is in a different state 
 of saturation. Probably it would not afford marks of alkalinity. 
 It might be found perhaps acidulous. It does not effloresce. 
 
 As soda contains not only a good deal of foreign salts, but a 
 greater or less proportion of sulphtiretj it is right to employ it 
 for certain operations of dyeing in the state of a pure carbonate. 
 It is then called salt of soda (crystals of soda). 
 
 In order to free soda from the foreign substances, it is to be 
 dissolved in water, and the different salts are to be separated 
 as they precipitate or crystallize. The crystals of carbonate 
 of soda form last of all. 
 
 When this salt is used, it is essential to pay attention to the 
 state in which it exists ; for when it is in crystals it contains 
 one-half (fully 3-5ths) its weight of water of crystallization. 
 Hence, when it has effloresced, one part produces as much 
 effect as two parts of crystals. 
 
 Lime acts on this salt in the same manner as on carbonate 
 of potash ; that is to say, it robs it of the greater portion of its 
 carbonic acid, rendering it caustic. In this state it is pure soda, 
 (for the small quantity of carbonic acid which it retains may be 
 neglected), the soda of chemists, the ley of the soap-boiler. 
 
 Sometimes the name of strong water, or strong liquor of the 
 soap-boilers, is given to a solution of caustic soda.* Such a 
 
OF THE CHEMICAL AGENTS. 
 
 245 
 
 denomination may easily lead to mistakes, making this alkaline 
 solution be confounded with nitric acid, called also eau forte, 
 (strong water, or aquafortis). Hellot tells us that he was 
 deceived in this way, in the preparation of a vat of indigo, 
 which had been suggested to him. 
 
 Since soda exerts on acids a stronger action than potash, it 
 may probably produce also a greater effect on colouring sub- 
 stances when it is pure ; but its alkaline action is much more 
 moderate when it is in the state of carbonate, for it is then in 
 a high degree of saturation, and possesses uniform properties. 
 From this circumstance it should therefore be preferred to 
 potash, which has less carbonic acid, containing variable quan- 
 tities of it in the state in which it is extracted. 
 
 CHAPTER VIIL 
 Of Soap. 
 
 Soap is the combination of an alkali with an oil. Alkali 
 deprived of carbonic acid must be employed for its formation ; 
 for this acid may eliminate its oil in combining with the alkali. 
 We must begin, therefore, with stripping it of its combined 
 carbonic acid. In the work-shops the name soap-ley is then 
 given to it. 
 
 To make this ley, the soda which is used for hard soap is 
 treated with a suitable proportion of lime, usually two of lime 
 for one of soda. A succession of waters is passed through the 
 same mixture. The last, which are least charged, are employed 
 the first in the boiling with oil ; because the coagulation which 
 would be formed at first with too strong a ley, would obstruct 
 the uniformity of the combination. 
 
 We have remarked, that the caustic alkali, prepared with 
 quicklime, retained a portion of its carbonic acid; which, on 
 treating the caustic ley with oil, converts a part of the alkali 
 into a carbonate that cannot enter into the compound. When- 
 ever the formation of the soap is advanced, the portion of ley ' 
 converted into carbonate, which may serve anew to make a 
 caustic ley with quicklime, is run off by a stopcock placed in 
 the lower part of the boiler. Strong ley is then added. When 
 
246 
 
 BERTHOLLET ON DYEING. 
 
 it is ascertained from samples that the consistence of the soap 
 is sufficient, it is drawn out and run into a species of wooden 
 moulds, where it cools, and takes the form adapted to commerce. 
 But before this last operation, a certain quantity of muriate of 
 soda is added, which facilitates the separation of the soap from 
 the aqueous liquid (spent ley). 
 
 This preparation may be made in the cold, but it is longer 
 and less easily finished. 
 
 Recent soap contains a great deal of water, which it loses by 
 desiccation. Fraudulent dealers endeavour to sell it with all 
 this weight ; and to preserve it in this state, they keep it in a 
 moist place, even in water saturated with sea-salt. This brine 
 does not dissolve it, but merely confines in it the whole water 
 that it can hold. For separating, by this property, the soap 
 from its solution in the boiler, the muriate of soda was added 
 towards the end, as we have stated. The redundancy of water 
 is discovered by keeping the soap in a dry and warm place, 
 where it soon loses what is superfluous. Starch, or other 
 foreign substances, are sometimes mixed with soap, in order to 
 augment its weight. 
 
 Marbled veins are given to soap by adding, before it has 
 assumed consistency, a little sulphate or red oxyde of iron, 
 which probably forms some metallic soap, that is unequally 
 mixed with the paste. Soap becomes harder by this means, 
 and retains less water. 
 
 The general properties of compounds are recognized in soap. 
 Thus soda, which produces, as we have seen, a greater eflfect 
 with the acids, comports itself in the same way with the oils, 
 thereby forming soaps, harder and less soluble than those which 
 have potash for their base. In consequence of this greater in- 
 solubility, if muriate of soda be added to a solution of soap 
 made with potash, the soda takes the place of the potash, and 
 it is a soap with base of soda which coagulates and separates, 
 as Darcet, Pelletier, and Lelievre observed, to whom we owe a 
 very good description of the preparation of soap.* 
 
 The oils contribute, on the other hand, to the qualities of 
 the combination which they form with the alkalies : thus the 
 fatty substances naturally solid, such as tallow, lard, and butter, 
 
 * Memoires de chimie, loin. xix. (Annales?) 
 
OF THE CHEMICAL AGENTS. 247 
 
 form solid and firm compounds ; olive oil, which has a tendency 
 to become solid whenever its temperature is lowered, affords a 
 hard soap, which makes it be preferred, for this species of soap, 
 (to which, in other respects, it communicates no disagreeable 
 smell or colour), to the other oils, which being less consistent, 
 yield softer soaps, commonly coloured. 
 
 If oils be combined with bases naturally disposed to take the 
 solid state, such as lime, magnesia, barytes, metallic oxydes, 
 insoluble soaps are formed ; but this insolubility is an obstacle 
 that prevents the combination from being directly formed with 
 accuracy. The solution of an alkaline soap must be taken, and 
 lime, barytes, or strontian water poured into it. These alkaline 
 earths take a portion of the oil from the soluble alkalies to 
 form an insoluble soap, which separates. Instead of the aqueous 
 solution of these bases, their solution in an acid may be taken. 
 In this case an exchange of base occurs, and the earthy com- 
 bination is more completely formed. The latter method must 
 be employed for the bases insoluble in water, such as magnesia, 
 and the metallic oxydes. 
 
 The uses for which soap is employed lead sometimes to the 
 preference of a hard, and sometimes of a soft soap. The first 
 is prepared with soda and olive oil. It ought to be white. 
 This soap is used in the ungumming (scouring) of silk. 
 
 To make soft soap, oil of colza, turnip seed, or fish oil, is 
 employed. The cheapest at the place of the manufacture is 
 generally chosen. But as softness is the quality now desired, pot- 
 ash is used instead of soda. Whiteness is of no consequence to 
 this soap ; and the oils made use of commonly impart a greenish 
 or even blackish colour, whence the article is called green or 
 black soap. 
 
 This soap is chiefly used in the bleaching of cloths and raw 
 yarns ; and in the operation of fulling woollens. 
 
 For the latter purpose, a less costly combination may be em- 
 ployed, possessing the detersive properties of soap ; this is the 
 solution of an animal substance in potash. Chaptal observed,* 
 that potash which has been saturated with fragments of wool 
 formed this species of soap, which might be advantageously 
 substituted for ordinary soap. The odour which it communi- 
 cates to cloth is dissipated by washing and exposure to the air. 
 
 * Memoires de Tinstit. torn. i. 
 
248 
 
 BERTHOLLET ON DYEING. 
 
 CHAPTER IX. 
 Of Sulphur. 
 
 Sulphur exposed to a certain heat volatilizes, and then 
 resumes the solid state by the contact of cold bodies. Thus it 
 is reduced to subtile molecules, called flowers of sulphur. This 
 preparation is made in the small apparatus of the laboratory ; 
 or on the great scale, in a kind of chimneys or chambers, where 
 it attaches itself to the cool walls. 
 
 When sulphur is exposed to a more elevated temperature, 
 it combines with oxygen, passing thereby to the state of an 
 acid ; but this acid differs according to the elevation of the 
 temperature, or the vivacity of the combustion. When the 
 temperature is not sufficiently high, sulphurous acid is obtained. 
 
 Sulphurous acid differs from sulphuric, 1. From the oxygen 
 in it being less condensed, so that the combination retains a 
 pretty great elasticity, and dissolves in only a small quantity in 
 water : 2. From the proportion of its oxygen being smaller 
 than in sulphuric acid, but, at the same time, this element 
 experiences a much weaker action on the part of the sulphur ; 
 a circumstance which has great influence on its characteristic 
 properties. 
 
 The oxygen is retained, therefore, much more feebly in sul- 
 phurous than in sulphuric acid. Hence several substances, 
 which do not take oxygen from sulphuric acid, decompose the 
 sulphurous. It inclines, in this respect, to the properties of 
 chlorine, although it does not give up its oxygen so easily, but, 
 on the contrary, carries off" that of the chlorine, in order to pass 
 to the state of sulphuric acid. In like manner, it inclines to 
 the properties of nitric acid. 
 
 Sulphurous acid, or the combination of the sulphurous gas 
 with water, is not employed in the processes of dyeing ; but 
 the vapour formed directly by the combustion of sulphur is 
 used. In this state of gas, it exercises a more lively action, for 
 it whitens the flowers, which, in its liquid state, it reddens like 
 the other acids. It would be wrong, therefore, to substitute 
 liquid sulphurous acid for the fumes of burning sulphur, as has 
 been proposed. There are circumstances, however, where a 
 different or more moderate effect might be wished for, in which 
 
OF THE CHEMICAL AGENTS. 
 
 249 
 
 it would be advantageous to employ it in the liquid state. "We 
 have seen one example of this in the process of Giobert for 
 bleaching raw silk. 
 
 For obtaining it in this state there is a more convenient and 
 easier means than by the combustion of sulphur ; that is, merely 
 to mix with sulphuric acid a vegetable substance containing 
 hydrogen, as sugar, and to distil, receiving the vapour that is 
 disengaged into the bottom of a receiver, by means of a tube. 
 Heat, which tends to produce elastic combinations, determines 
 a formation of water, at the expense of the hydrogen of the 
 sugar, and a production of sulphurous acid, which issues to 
 combine with the cold water. But there is formed at the same 
 time a little carbonic acid, of no importance to the operations 
 for which the liquid acid is intended. Besides, when the sul- 
 phurous acid acquires a certain condensation, it expels the 
 carbonic acid from the water. 
 
 Sulphuring, or exposure to the fumes of burning sulphur, is 
 employed to give the utmost whiteness to silks and woollens 
 intended for white stuffs. 
 
 For the sulphuring process an insulated chamber, having no 
 chimney, is made choice of, through which, on occasion, a 
 current of air may be sent. 
 
 For 110 pounds of silks stretched on perches, placed at a 
 height of rather more than two yards, nearly two pounds of sul- 
 phur, reduced to a coarse powder, are put into an earthen or iron 
 pot, at whose bottom there is a little ashes. This powder is set fire 
 to in several places. The chamber is well closed, to prevent the 
 dissipation of the sulphurous fumes. Next day, the windows 
 are thrown open to let them escape, and to dry the silk. But 
 in winter, after the smell of the sulphur has gone away, the 
 windows are re-shut, and burning charcoal is introduced, in 
 *• chafing-dishes, to make the silk dry. 
 
 This operation gives the silk not merely a great whiteness, 
 but at the same time creakiness or rustling in handling, {du cri 
 ou du maniement,) that is to say, a species of tremulous elas- 
 ticity, which is perceived on pressing it between the fingers. 
 
 As the maniement gives a certain stiffiiess to silks, those must 
 not be sulphured which are to be watered, because they would 
 give too much resistance . to the impressions of the calendar, 
 under which the silks are passed to give them the undulations. 
 
250 
 
 BERTHOLLET ON DYEING. 
 
 In like manner, sulphuring cannot be applied to silks intended 
 for the hat manufactory, because they would corrode the iron 
 and steel of the tools with which they are to be worked, and 
 occasion rust. 
 
 Sulphured silk takes on most colours badly; and, therefore, 
 previously to dyeing, it must be freed from sulphur, by repeated 
 soaking and shaking over in hot water. 
 
 When silk is sulphured, if it be thought not to have sufficient 
 azure for the wished for shade, it must be azured a second time 
 in clear water, without addition of soap, and then again sul- 
 phured. 
 
 These properties of the sulphured silk are owing to the sul- 
 phurous acid which has combined with it, whose presence may 
 be made perceptible by means of sulphuric acid, which imme- 
 diately disengages sulphurous vapours from it. The sulphuring 
 of woollen cloth is executed in nearly the same manner as that 
 of silk ; but it is to be remarked, that if this operation be not 
 performed with precaution, and that if the combustion of the 
 sulphur takes place with too much rapidity, sulphuric acid is 
 formed, which falling down in drops, corrodes the cloth, — an 
 inconvenience not easily avoided. 
 
 CHAPTER X. 
 Of Waters. 
 
 The quality of the waters is an essential object in dyeing; 
 but it is perhaps less important to make known the injurious 
 effects which they may produce, than to destroy the prejudices 
 to which they have often given rise. Thus peculiar properties 
 have been ascribed to the water of the Bievre, which supplies 
 the manufactory of the Gobelins; but Guillaumot remarks, 
 that when this little river is too low, the water is drawn from 
 the Seine, without seeming to render the dyes less beautiful. 
 
 It is superfluous to say, that the waters used in dyeing must 
 not be muddy, or contain putrid substances ; that waters so 
 much charged with foreign matters, as to be ranked among 
 mineral waters, easily distinguishable by the taste, must not be 
 
OF THE CHEMICAL AGENTS. 
 
 251 
 
 employed. With these exceptions, waters act on the colouring 
 particles principally by the earthy salts they contain, which 
 render the colours in general deeper and more dull. 
 
 The carbonates of lime and magnesia have, moreover, the 
 inconvenience of being thrown down during the ebullition, which 
 expels the excess of carbonic acid that held them in solution. 
 Thus these earths applied to the stuffs darken them, and prevent 
 the colouring particles from penetrating. 
 
 It is of importance therefore, to ascertain these species of 
 waters, called hard or crude, in order to avoid them in most 
 dyes. Chemists possess methods, not only of determining the 
 different principles contained in waters, but even of assigning 
 with precision the quantity of each ; but the precautions requi- 
 site for this analysis, in general demand a profound knowledge 
 and experimental dexterity, which persons engaged in dyeing 
 cannot be presumed to possess. Happily a trivial and easy test 
 is sufficient to show whether a water contains an injurious 
 quantity of these salts. This is, the solution of soap. 
 
 All the salts having an earthy base decompose soap by an ex- 
 change of bases. Their earth unites to the oil, while their acid 
 combines with the alkali of the soap ; and from the combination 
 of the oil and the earth, a soap with earthy base results, which 
 being insoluble in water, forms the clots, (or mottling,) which 
 are in that case observable. 
 
 Whenever, therefore, a water is limpid, w^hen its flow is 
 constant, when it has no sensible taste, and dissolves soap well, 
 it may be regarded as very proper for dyeing ; and all such as 
 possess these qualities are equally suitable. 
 
 But since a choice of waters is not always equally at com- 
 mand, methods have been sought for correcting such as were 
 bad, at least to a certain degree, particularly for the purpose of 
 dyeing delicate colours. With this view, water in which bran 
 has been fermented, called sour water, is principally used. 
 
 It appears that sour water acts by decomposing the carbonates 
 of lime and magnesia, its acid expelling the carbonic acid. The 
 earthy sediment which forms during ebullition is thus obviated. 
 
 Mucilaginous plants are also boiled along with the water to 
 be corrected, when a froth forms, that is skimmed off. The 
 mucilage coagulates, carrying with it the earths which separate 
 on the volatilization of the carbonic acid, as well as such as 
 are merely mixed with the water, and which render it turbid. 
 
252 
 
 BERTHOLLET ON DYEING. 
 
 The salts with an earthy base, which are in general injurious 
 to dyeing, may in certain cases be useful, serving to modify the 
 colours when our object is to obtain deep shades. 
 
 As the water of a river may contain more or fewer salts with 
 an earthy base, according as its bed is higher or lower, it happens 
 sometimes that on following exactly the same process the same 
 shade is obtained only at certain periods ; or some modifications 
 are required to be made in the process to obtain the same result, 
 according to the state of the river. 
 
 The waters which decompose soap, and form a soap of lime, 
 are disadvantageous to bleaching, not merely by the waste of 
 the soap uselessly decomposed, but principally because the cal- 
 careous soap, which is insoluble in water, fixes on the stuff*, 
 gives it a greasy feel, renders it at the same time yellow, and 
 shakes off* in small scales. This inconvenience is obviated by 
 decomposing the earthy salts with a little carbonate of soda or 
 potash. 
 
PART 11. 
 
 OF THE PROCESSES OF ART, 
 
 SECTION L 
 
 OF BLACK. 
 
 CHAPTER L 
 Of the Processes for Dyeing Black, 
 
 Very few substances are known which can aftbrd of themselves 
 a sohd black ; and they have been tried only on linen and cotton. 
 The juice of the cashew nut, or anacardium of India, commu- 
 nicates a black colour, which resists, not only washing, but 
 even boiling with soap and alkaline leys. It is used for mark- 
 ing linen. The anacardium occidentale affords also a durable 
 dye, but it is merely brownish. 
 
 The toxicodendron yields a juice which produces nearly the 
 same effect. The juice of the stems of hop affords a very 
 durable brownish-red colour. Sloe juice gives a pale tint bor- 
 dering on brown, which, washed several times with soap, and 
 then moistened with solution of alkali, becomes of a deeper 
 brown. On boiling sloes, their juice becomes red; and the 
 red dye which it imparts to linen, changes, when washed with 
 soap, into a bluish colour, which is permanent.* 
 
 According to Linnseus,f the juice of the berries of the cectea 
 spicata, or cristophoriana, makes a black ink with alum ; and 
 the berries of the impetrum procumbens, or erica baccifera nigra, 
 produce with alum a black colour bordering on purple. 
 
 A tree grows in the Brazils, which the botanists call pomi- 
 
 * Lewis' Exper. Phys. et chym. torn. ii. 
 
 f Amoenit. Academ. 
 
254 
 
 BERTHOLLET ON DYEING. 
 
 fera indica tinctoria, or genipa Americana, whose berries and 
 leaves dye a black-blue, which resists the action of soap. 
 
 The methods just mentioned of obtaining a black colour 
 cannot be employed in dyeing, because the substances from 
 which it is derived cannot be collected in sufhcient quantities 
 for the necessities of the art, and because the black which they 
 afford is not comparable to that formed in the dyehouse. All 
 black dyes are the result, therefore, of an artificial combination. 
 The black molecules which are produced by the union of the 
 astringent principle, or of another colouring substance, and the 
 oxyde of iron, combine with the stuffs. We shall proceed to 
 detail the principal processes by which this operation is per- 
 formed on different kinds of goods. 
 
 According to the process which Hellot describes,* for dyeing 
 woollen cloth black, it must receive the deepest blue, or maza- 
 rine blue, be washed in the river on coming out of the vat, and 
 then cleansed at the fulling-mill. 
 
 For 110 pounds of cloth there are put into a boiler, of middle 
 size, 17| pounds of logwood, with as much Aleppo galls in 
 powder, and the whole being enclosed in a bag, is boiled in a 
 sufficient quantity of water for twelve hours. One-third of this 
 bath is transferred into another boiler with 2 pounds 3 ounces 
 of verdigris; and the stuff is passed through this solution, 
 stirring it continually during two hours, taking care to keep the 
 bath very hot without boiling. The stuff is then lifted out, 
 another third of the bath is added to the boiler, along with 
 9 pounds of sulphate of iron or green vitriol. The fire is to be 
 lowered while the sulphate dissolves, and the bath is allowed to 
 cool for half an hour, after which the stuff is introduced, and 
 well moved about for an hour, after which it is taken out to air. 
 Lastly, the remaining third of the bath is added to the other 
 two, taking care to squeeze the bag well: 17 to 22 pounds of 
 sumach are thrown in ; the whole is just brought to a boil, and 
 then refreshed with a little cold water ; 2 pounds 3 oz, more of 
 sulphate of iron is added, after which the stuff is turned through 
 for an hour. It is thereafter washed, aired, and put again into 
 the bath, stirring it continually for an hour. After this, it is 
 carried to the river, washed well, and then fulled. Whenever 
 
 L'Art de la teinture en laine, &c. 
 
OF BLACK. 
 
 255 
 
 the water runs off clear, a batli is prepared with weld, which is 
 made to boil for an instant ; and after refreshing the bath, the 
 stuff is turned in to soften it, and to render the black more fast. 
 In this manner, a very beautiful black is obtained, without ren- 
 dering the cloth too harsh. 
 
 Commonly more simple processes are employed. Thus the 
 blue cloth is simply turned through a bath of gall-nuts, where it 
 is boiled for two hours. It is next passed through a bath of 
 logwood and sulphate of iron for two hours, without boiling, 
 after which it is washed and fulled. 
 
 Hellot has found that the dyeing might be performed in the 
 following manner: — For 18 metres (yards nearly) of dark blue 
 cloth, a bath is made of 1| pounds of fustic {morus tinctorial) 
 4|- pounds of logwood, and 1 1 pounds of sumach. After boiling 
 the cloth in it for three hours, it is lifted out, 1 1 pounds of sul- 
 phate of iron are thrown into the boiler, and the cloth is then 
 passed through it during two hours. It is now aired, and put 
 again into the bath for an hour. It is lastly washed and scoured. 
 The black is less velvety than that of the preceding process. 
 Experience convinced him, that the maddering prescribed in the 
 ancient regulations only gives a reddish cast to the black, which 
 is obtained finer and more velvety without madder. 
 
 A black may be dyed likewise without having given a blue 
 ground. This method is employed for cloths of little value. In 
 this case they are rooted, that is to say, they receive a dun 
 ground with walnut husks, or the root of the walnut tree, and 
 are afterwards made black in the manner above described, or in 
 some other way ; for it is obvious, that a black may be obtained 
 by several processes. (Note FF.) 
 
 According to Lewis, the proportions which the English dyers 
 most generally adopt are, for 110 pounds of woollen cloth previ- 
 ously dyed of a dark blue, about 5J pounds of sulphate of iron, 
 as much gall-nuts, and 33 pounds of logwood. They begin by 
 galling the cloth, they then pass it through the decoction of 
 logwood, to which the sulphate of iron has been added. 
 
 When the cloth is completely dyed, it is washed in the river, 
 and passed through the fulling-mill till the water runs off clear 
 and colourless. Some persons recommend, for fine cloths, to 
 full them with soap water. This operation requires an expert 
 workman^ who can free the cloth thoroughly from the soap. 
 
256 
 
 BERTHOLLET ON DYEING. 
 
 Several recommend at its coming from the fulling to pass the 
 cloth through a bath of weld, with the view of giving softness 
 and solidity to the black. Lewis says, that passing the cloth 
 through weld, after it has been treated with soap, is absolutely 
 useless, although it may be beneficial when this operation has 
 been neglected. 
 
 We read in the Memoirs of Stockholm for the year 1753, 
 that for nutgalls may be substituted the uva ursi, gathered in 
 autumn, and dried with care so as to keep its leaves green, 
 110 pounds of wool are to be boiled for two hours with 17 
 pounds of sulphate of iron, and as much tartar ; the cloth is 
 rinsed on the following day, as after alluming. 165 pounds of 
 uva ursi are then boiled in water for two hours. After removing 
 it, a little madder is introduced, and the cloth is at the same 
 time immersed in the decoction, in which it is left for an hour 
 and a half, or an hour and three quarters, and thereafter rinsed 
 in water. Lewis remarks, that this manner of dyeing gives a 
 good enough black on blue cloth, but merely a dark brown on 
 white cloth ; and that the madder and tartar are of no use. 
 The uva ursi throws down the iron in coarse black particles, 
 w^hich float through the water. 
 
 Different operations may be distinguished in dyeing silk 
 black ; the boiling of the silk, its galling, the preparation of the 
 bath, the operation of dyeing, the softening of the black. 
 
 Silk, as we have seen. Part 1. p. 101, naturally contains a 
 substance called gum^ which gives it the stiffness and elasticity 
 peculiar to it in its native state ; but this adds nothing to the 
 strength of the silk, which is then styled raw ; it rather renders 
 it, indeed, more apt to wear out by the stiffness which it com- 
 municates ; and although raw silk more readily takes a black 
 colour, yet the black is not so perfect in intensity, nor does it 
 so well resist the reagents capable of dissolving the colouring 
 particles, as silk which has been {decreussee) scoured or deprived 
 of its gum. 
 
 To cleanse silk intended for black, it is usually boiled four or 
 five hours with one-fifth of its weight of white soap, after which 
 it is carefully beetled and washed. 
 
 For the galling, nut-galls equal to nearly three-fourths of the 
 weight of the silk are boiled during three or four hours ; but on 
 account of the price of Aleppo galls, more or less of the white 
 
BLACK. 
 
 257 
 
 gall-nuts, or of even an inferior kind called galon^ berry or 
 apple-galls are used. The proportion commonly employed at 
 Paris is, two parts of Aleppo galls to from eight to ten parts of 
 galon. After the boiling, the galls are allowed to settle for 
 about two hours. The silk is then plunged into the bath, and 
 left in it from twelve to thirty-six hours, after which it is taken 
 out and washed in the river. 
 
 Silk is capable of combining with quantities, more or less 
 considerable, of the astringent principle ; whence results a con- 
 siderable increase of weight, not only from the weight of the 
 astringent principle, but also from that of the colouring par- 
 ticles, which subsequently fix themselves in proportion to 
 the quantity of the astringent principle which had entered into 
 •combination. Consequently, the processes are varied according 
 to the degree of weight which it is wished to communicate to 
 the silk ; a circumstance requiring some illustration. 
 
 The commerce of silk goods is carried on in two ways : they 
 are sold either by the weight or by the surface, that is, by 
 measure. Thus the trade of Tours was formerly distinguished 
 from that of Lyons ; the silks of the former being sold by 
 weight, the latter by measure. Tt was therefore their interest 
 to surcharge the weight at Tours, and, on the contrary, to 
 be sparing of the dyeing ingredients at Lyons; whence came 
 the distinction of light black and heavy black. At present, 
 both methods of dyeing are practised at Lyons, the two modes 
 of sale having been adopted there. 
 
 Silk loses nearly a fourth of its weight by a thorough boiling, 
 and it resumes, in the light black dye, one-half of this loss ; but 
 in the heavy black dye, it takes sometimes upwards of a fifth 
 more than its primitive weight; a surcharge injurious to the 
 beauty of the black, and the durability of the stuff. The sur- 
 charged kind is denominated English black, because it is pre- 
 tended that it came to us. from England. Since silk dyed with 
 a great surcharge has not a beautiful black, it is usually destined 
 for weft, and is covered (blended) with a warp dyed of a fine black. 
 
 The peculiarity of the process for obtaining the heavy black, 
 consists in leaving the silk longer in the gall-liquor, in repeating 
 the galling, in passing the silk a greater number of times through 
 the dye, and even letting it lie in it for some time. The first 
 galling is usually made with galls which have served for a pre* 
 
258 
 
 BERTHOLLET ON DYEING. 
 
 ceding operation, and fresh gall-nuts are employed for the 
 second. But these methods would not be sufficient for giving a 
 great surcharge, such as is found in what is called the English 
 black. To give it this weight, the silk is galled without being 
 ungummed ; and on coming out of the galls, it is rendered 
 supple by being worked on the jack and pin, (cheinllages,) 
 
 The silk-dyers keep a black vat, and its very complex compo- 
 sition varies in different dye-houses. These vats are commonly 
 established for many years ; and when their black dye is ex- 
 hausted it is renovated by what is called a brevet. When the 
 deposite which has accumulated in it is too great it is taken out, 
 so that at the end of a certain time nothing remains of the 
 several ingredients which composed the primitive bath, but 
 which are not employed in the brevet. The description of a 
 bath and brevet of this description may be seen in the work of 
 Macquer.* There entered into it seeds of foenugreek, of 
 psyllium, (fleawort,) cummin, colocynth, the berries of buck- 
 thorn, agaric, nitre, muriate of ammonia, sal gem, litharge, 
 lead ore, orpiment, corrosive muriate of mercury, &c. Macquer 
 acknowledges that there are many useless ingredients in this 
 process ; and in fact several of them are no longer admitted. 
 But the compositions not only of every country, but of every 
 dyehouse differ. 
 
 Iron filings are usually added to the dyeing bath ; but some 
 dyers, particularly at Tours, substitute for them the moulee, or 
 the abraded dust of grindstones ; this moulee probably acts 
 merely by the particles of iron which it contains in a very com- 
 minuted state. 
 
 While the silks are getting the preparatory treatment for 
 dyeing, the bath is heated, taking care to stir it from time to 
 time, in order that the marc (sludge or sediment) at the bottom 
 may not become too hot. This bath should never be raised to 
 ebullition. More or less gum and solution of iron are added, 
 according to the different processes ; and when it is judged that 
 the gum is dissolved, and that the bath has arrived at a degree 
 approaching to ebullition, it is allowed to settle for about an 
 hour ; the silks are then plunged into it, usually divided into 
 three portions, that they may be immersed successively in the 
 bath. Each portion is slightly wrung three times, and each 
 
 * Art de la teintnre en soie. 
 
OF BLACK. 
 
 259 
 
 time hung up to air. The object of this operation is to squeeze 
 out the liquor with which the silk is impregnated, and which is 
 exhausted, and to make fresh liquor penetrate it ; but above all 
 to expose the silk to the atmosphere, which deepens the black. 
 
 After each portion of the silk has experienced three wringings, 
 the bath must be heated anew, putting into it again gum and 
 sulphate of iron, as at first. The operation performed in the 
 interval from one heating to another, is called a fire, {un feu.) 
 Only two fires are given for a light black, but three for a heavy- 
 black ; and the dyers let the silk remain in the bath, even after 
 the last fire, for about twelve hours. Sixty-six pounds are 
 usually dyed in one operation, which is called a heat, {chaudee,) 
 If only the half of this quantity be dyed, there is occasion for 
 no more than one fire for the light black. 
 
 The dyeing operation being finished, a little cold water is put 
 into a tub, in which the silk is washed by turning or shaking it 
 over the rods, {on dishrode la sole en la lisant,) 
 
 The silk, on coming out of the bath, has a great deal of harsh- 
 ness. The operation by which it is freed from this, is termed 
 the softening. Into a large vessel, nearly full of water, a solu- 
 tion of soap is poured, in the proportion of from 4 to 5 pounds 
 of soap for every 110 pounds of silk. The solution of soap is 
 strained through a cloth into the water, and is well mixed with 
 it. The silk is then introduced, and left for about a quarter of 
 an hour, after which it is wrung out and dried. 
 
 For the dyeing of raw silk black, it is galled in the cold with 
 the bath of galls which have already served for the black of 
 boiled silk. For this purpose, silk in its native yellow colour is 
 made choice of. It should be remarked, that when it is desired 
 to preserve a portion of the gum of the silk, which is afterwards 
 made flexible, the galling is given with the hot bath of gall-nuts 
 in the ordinary manner. But here, where the whole gum of the 
 silk, and its concomitant elasticity are to be preserved, the 
 galling is made in the cold. If the infusion of galls be weak, 
 the silk is left in it for several days. 
 
 Silk thus prepared and washed takes very easily the black dye, 
 and the disbrodure, (rinsing in a little water,) to which sulphate 
 of iron may be added, is sufficient to give it. This dye is made 
 in the cold ; but according to the greater or less strength of the 
 rinsings, (disbrodure,) it requires more or less time,. Occasion- 
 
 s 2 
 
260 
 
 BERTHOLLET ON DYEING. 
 
 ally three or four days are necessary ; after which it is washed, 
 beetling it once or twice, and it is then dried without wringing, 
 to avoid softening it. 
 
 Raw silk may be more quickly dyed, by shaking it round the 
 rods in the cold bath after the galling, airing it, and repeating 
 these manipulations several times ; after which it is washed and 
 dried as above. 
 
 Macquer describes a more simple process for the black, with 
 which velvet is dyed at Genoa, and he says that this process, 
 rendered still simpler, has had complete success at Tours. The 
 following is his description. 
 
 For 110 pounds of silk, 22 pounds of Aleppo galls, in powder, 
 are boiled for an hour in a sufficient quantity of water. The 
 bath is allowed to settle till the galls have fallen to the bottom 
 of the boiler, from which they are withdrawn ; after which 33 
 pounds of English vitriol (copperas) are introduced, with 13 
 pounds of iron filings, and 22 of country gum, put into a kind 
 of two-handled colander pierced every where with holes. This 
 kettle is suspended by two rods in the boiler, so as not to reach 
 the bottom. The gum is left to dissolve for about an hour, 
 stirring it from time to time. If after this time some gum 
 remains in the kettle, it is a proof that the bath, which contains 
 two hogsheads, has taken as much of it as is necessary. If, on 
 the contrary, the whole gum is dissolved, from 2 to 4J pounds 
 more may be added. The colander is left constantly suspended in 
 the boiler, from which it is removed only when the dyeing is 
 going on ; and thereafter it is replaced. During all these ope- 
 rations the boiler must be kept hot, but without boiling. The 
 galling of the silk is performed with one-third of Aleppo galls* 
 The silk is left in it for six hours the first time ; then for 
 twelve hours. The rest, secundum artem. 
 
 Lewis states, that he Jias repeated this process in the small 
 way ; and that by adding sulphate of iron progressively, and 
 repeating the immersions of the silk a great number of times, 
 he eventually obtained a fine black. 
 
 The sulphate of iron, indeed, seems to be in too small pro- 
 portion, in the process described by Macquer ; and' some incon- 
 veniences must undoubtedly have been found in it, since its 
 practice has not been retained at Tours. Lewis thinks that the 
 ^um is of no use, and that it is all carried away in the washing 
 
OF BLACK. 
 
 261 
 
 of the silk ; but if he had continued to dye in the same bath, 
 he would probably have perceived that it served to maintain it. 
 It appears, however, that an excess of it had been used in that 
 process. It must assuredly be advantageous, when the quan- 
 tity of gum is diminished, to add the sulphate of iron in por- 
 tions, after each fire ( chaque feu.) Lewis remarks, moreover, 
 that although a good black may be dyed on white silk, without 
 making use of logwood or verdigris, the addition of these two 
 ingredients contributes greatly to improve the colour on silk as 
 well as on wool. 
 
 The process of dyeing black on silk is very expensive, from 
 the quantity of galls, as their price is much raised. It is of 
 consequence, therefore, to try to lessen its quantity. We shall 
 advert to a process extracted from the memoir of Angles, which 
 competed for a prize proposed by the Academy of Lyons in 
 1776, in which this object was attempted. 
 
 The silk, boiled with care and washed in the river, is plunged 
 into a strong decoction of green walnut peels, in which it is 
 left till the colour of the bath be exhausted. It is then with- 
 drawn to be slightly wrung on the pins, dried, and washed in 
 the river. The decoction of the walnut husks is made by boil- 
 ing for a full quarter of an hour ; after which it is taken from 
 the fire, and the froth is allowed to fall before plunging in the 
 silk, which should have been previously soaked in tepid water. 
 The blue ground is given by means of logwood and verdigris, 
 dissolving in cold water one part of verdigris for sixteen of silk. 
 This is allowed to steep in it for two hours, and it is then passed 
 into a strong decoction of logwood. It is gently wrung out and 
 dried, previous to its being washed in the river. For a light 
 black, the galling may be dispensed with ; but for obtaining 
 a heavy black, the silk must be galled with half its weight of 
 gall-nuts. 
 
 To prepare the bath, 2 pounds of nut-galls, and 3 pounds of 
 sumach, are macerated in 22 gallons of water, over a slow fire, 
 for twelve hours. Whenever the bath has become clear, 3 pounds 
 of sulphate of iron, and as much gum arable, are dissolved in it. 
 The solution being made, the silk is plunged in at two successive 
 times, and is allowed to remain each time for two hours, taking 
 care after the first immersion to air and dry it before giving it 
 the second fire ; after which it is aired and dried equably. Two 
 
262 
 
 BERTHOLLET ON DYEING. 
 
 beetlings in the river are now given ; after this it receives the 
 third fire, in the same manner as the two preceding, except that 
 it is left four or even five hours in the bath. When it is drained 
 and dried, two other beetlings are given in the river. Care 
 must be had that during the operation the degree of heat do 
 not exceed the middle term between freezing and boiling water, 
 which corresponds to 40° R. (122° F.) ; and before giving the 
 last two fires, half-a-pound of sulphate of iron, and as much 
 gum arable, must be added. 
 
 To remove the harshness that the black dye imparts to silk. 
 Angles prefers the decoction of weld to the solution of soap. 
 
 He says, that the blue of indigo given to silk before the black 
 dye, allows it to take only a mealy black, but that with logwood 
 and verdigris a velvety black is obtained. He also says, that 
 green walnut peels soften silk. Although a fine black may be 
 formed with walnut peels, and the bath which has been 
 described, he adds to it, however, the logwood and verdigris, 
 in order to save the necessity of employing much sulphate of 
 iron, which weakens the silk too much. Lastly, he thinks that 
 nut'galls serve merely to give weight to the silk, and that 
 sumach is sufficient for this dye. 
 
 Linen and cotton take with difficulty a sufficiently deep black, 
 that will resist soap. Hence we are obliged to employ peculiar 
 processes for dyeing them black ; and hitherto few such dyes 
 have been found to give satisfaction. 
 
 For dyeing cotton and linen black, a solution of iron is made 
 use of, which is kept in a cask called the black cask.* This 
 solution is prepared either with vinegar or small beer, or with 
 the washings of pressed grapes, which is soured with rye-meal 
 or other ingredients, with the view of getting an acid liquor at 
 the lowest price. Old iron is thrown into this liquor, and the 
 solution is set aside, to be used on occasion, taking care not to 
 employ it till six weeks or two months from its preparation. 
 Astringents are often added to this bath, and particularly the 
 decoction of alder bark, which, even alone, has the property of 
 dissolving a considerable quantity of oxyde of iron. 
 
 We remarked, in speaking of the acetate of iron, that this 
 metal should be highly oxydized. It is consequently proper to 
 
 * See Part I. p. 227. 
 
OF BLACK. 
 
 263 
 
 separate the solution after it is made, from the metal below, 
 which opposes its oxygenation. 
 
 Le Pileur d'Apligny describes the process* followed at Rouen, 
 for linen and cotton yarns. They are first dyed sky-blue in the 
 vat, then wrung out, and set to dry. They are galled in the 
 proportion of one part of gall-nuts for four of yarn. They are 
 left twenty -four hours in the gall liquor, then wrung out anew, 
 and set to dry. 
 
 About 2^ gallons of the black cask for every 2 pounds of 
 yarn, are then poured into a tub. In this, the yarn is turned 
 on the sticks, and worked with the hand in portions for about 
 a quarter of an hour ; it is then wrung out and aired. This 
 operation is twice repeated, adding each time a new dose of the 
 black cask, which should be skimmed with care. The yarn is 
 aired once more ; it is then wrung out, and washed in the river 
 to cleanse it well, and dried. 
 
 To complete the dyeing of the yarn, a weight of alder bark, 
 equal to that of the yarn, is boiled for an hour in a copper, 
 along with a sufficient quantity of water. To this are added 
 about one-half of the bath which has served for the galling, and 
 sumach equal to one-half the weight of the alder bark. The 
 whole is made to boil anew for the space of two hours, after 
 which this bath is passed through a scarce. When it is cold, 
 the yarn is turned through it on the sticks, and it is worked in 
 it by portions at a time. It is aired occasionally, then it is let 
 down into the bath, where it is left for twenty-four hours. It 
 is now wrung out and dried. 
 
 In order to soften this yarn after it is dry, it is the practice 
 to steep it, and work it in the residuum of a bath of weld, which 
 has served for other colours, to which a little logwood is added. 
 It is taken out and wrung, and immediately turned through a 
 tub of warm water, into which one part of olive oil for sixteen 
 of yarn has been poured. It is finally wrung out and dried. 
 
 Le Pileur d'Apligny describes a process in which he makes 
 use also of madder, to give linen and cotton yarn a black colour, 
 which he speaks of as very beautiful, and very durable. 
 
 The yarn is first of all scoured in the ordinary way, galled, 
 alumed, then turned through a bath of weld. On coming out 
 
 * L'Art de la teinture dcs fils et etoffes de colon. 
 
264 
 
 BERTHOLLET ON DYEING. 
 
 of this bath, it is dyed in a decoction of logwood, to which one- 
 fourth part of sulphate of copper must be added for one part 
 of yarn. On quitting this bath, it is washed in the river, and 
 wrung repeatedly, without twisting it too strongly. Lastly, it 
 is dyed in a bath made with one part of madder for two of yarn. 
 To render the black not liable to change, the yarn must be 
 turned through a bath of boiling soap water. 
 
 Wilson describes the manner pursued at Manchester, as 
 follows :* a galling is given with nut-galls or sumach, after 
 which the dyeing is performed with the liquor of a bath com- 
 posed of a solution of iron in a vegetable acid, formed not 
 unusually with alder bark and iron ; and then the goods are 
 turned through the decoction of logwood with a little verdigris. 
 The process is repeated till a deep black be obtained. It is 
 necessary to wash and dry between each operation. 
 
 Mr. Bancroft had announced, that the acid of tar was em- 
 ployed at Manchester for black dyes on cotton. Chaptal, in his 
 dyes, used pyrolignous acid ; but to Bosc we owe the details of 
 the operation by which he himself obtained a fine black by 
 means of that acid.f 
 
 " Fill a cast iron boiler with pyrolignous acid ; add to it old 
 iron, well oxydized, and boil. The solution of the oxyde will 
 take place rapidly. When the iron grows clean, and the solu- 
 tion black as ink, throw the whole into a cask, to be employed 
 at need. Prepare your cotton as usual, by giving it a blue 
 ground. Gall ; turn the hanks of cotton through a bath of solu- 
 tion of pyrolignite of iron diluted with tepid water. Renew the 
 gallings, and the turnings through the bath of pyrolignite of iron, 
 till you have obtained a deep and brilliant black. Finish by passing 
 your cotton through olive oil. This operation is simple. Throw 
 on some tepid water a little olive oil ; pass the cotton through 
 this bath ; it absorbs the oil ; but it must be worked for a long 
 time in the bath to diffuse the oil equally. This process softens, 
 and gives suppleness to the cotton, as well as a great deal of 
 brilliancy. Dry in the shade. The cottons are now of a perfect 
 and very durable black. Every time that the bath of pyrolig- 
 
 * An Essay on Light and Colours, and on what the colouring matters are that dye 
 cotton and linen. 
 
 + Anuales des arts ct manufactures, torn. v. 
 
OF BLACK. 
 
 265 
 
 nite of iron has been employed, it must be thrown away as 
 useless, and the old baths are never to be added to the cask." 
 
 Bosc intimates, that the stuffs dyed by means of pyrolignous 
 acid, retain, with much tenacity, the odour of this acid, and 
 that they must be exposed for some time to the air to rid them 
 of it, before folding them up for packing. 
 
 The application of oil, which heightens the black, and imparts 
 softness to the stuffs, is given to those which are woven, for ex- 
 ample, to cotton velvet, by means of brushes, which are slightly 
 imbued with it at their surface. 
 
 Hermstadt* recommends a process of Vogler, which consists 
 in making use for a mordant of a solution of nitrate of lead, in 
 turning the stuff through a solution of glue, and in dyeing it 
 in a bath composed of gall-nuts, logwood, and sulphate of iron, 
 for which last the acetate may be substituted. 
 
 CHAPTER II. 
 
 Observations on the Processes for Dyeing Black. 
 
 We have dwelt at sufficient length on the reciprocal action of 
 astringents and the oxyde of iron, and on the production of the 
 molecules, which, attaching to stuffs, dye them black. But 
 though the theory can lead to satisfactory explanations on this 
 subject in general, it should be advanced with diffidence when it 
 is to be applied to the processes of art. Circumstances unper- 
 ceived, properties apparently slight, may influence the results 
 sufficiently to cause in them some variations, for which no reason 
 can be assigned, and to lead to the preference of practices which 
 are empirical in so far as the trials in the small way differ 
 enough by the rapidity of evaporation, the degree of he^t, and 
 the action of the air, to make us cautious of advising changes, 
 whose success has not been verified by operations on the great 
 scale. 
 
 We shall select, therefore, in the description of processes, 
 those to which experience, or the name of their authors, appears 
 to give authority ; and we shall draw from theory, or even from 
 
 * Giundriss der Paibekunst. 
 
266 
 
 BERTHOLLET ON DYEING. 
 
 our own trials, such counsels as may guide well-informed artisans 
 in the study and successive improvement of the processes which 
 they employ. 
 
 Astringents differ from one another as to the quantity of the 
 principle which enters into combination with the oxyde of 
 iron. Hence the proportion of the sulphate, or of any other 
 salt of iron, and that of the astringents, should vary according 
 to the astringents made use of, and according to their respective 
 quantities. Gall-nut is the substance which contains most astrin- 
 gent ; sumach, which seems second to it in this respect, throws 
 down, (decomposes,) however, only half as much sulphate of 
 iron. 
 
 The most suitable proportion of sulphate of iron, appears to 
 be that which corresponds to the quantity of the astringent 
 matter, so that the whole iron precipi table by the astringent 
 may be thrown down, and the whole astringent may be taken 
 up in combination with the iron. As it is not possible, however, 
 to arrive at such precision, it is better that the sulphate of iron 
 should predominate, because the astringent, when in excess, 
 counteracts the precipitation of the black colouring particles, 
 and has the property of even dissolving them. 
 
 This action of the astringent is such, that if a pattern of 
 black cloth be boiled with gall-nuts it is reducible to grey. An 
 observation of Lewis may thence be explained. If cloth be 
 turned several times through the colouring bath, after it has 
 taken a good black colour, instead of acquiring more body, it is 
 weakened and becomes brownish. Too considerable a quantity 
 of the ingredients produces the same effect ; to which the sul- 
 phuric acid, set at liberty by the precipitation of the oxyde of 
 iron, contributes. 
 
 It is merely the highly oxydized sulphate which is decom- 
 posed by the astringent ; whence it appears, that the sulphate 
 will produce a different effect according to its state of oxydize- 
 ment, and call for other proportions. It is right, therefore, to 
 follow the advice of Proust, employing it in the oxydized state; 
 but in this case it is only partially decomposed, and another 
 part is brought, by the action of the astringent, into the slightly 
 oxydized sulphate. 
 
 The molecules precipitated by the mixture of an astringent 
 and sulphate of iron, have not at first a deep colour ; but they 
 pass to a black by contact of air, while they are moist. 
 
OF BLACK. 
 
 267 
 
 In these phenomena may be found the reason of two methods 
 which are adopted. 1. Black is not given by a single opera- 
 tion. The dyeing is interrupted and divided into different 
 stages. Thus, the iron which has been de-oxydized, can resume 
 a sufBcient quantity of oxygen for the succeeding stage, and the 
 bath which could produce no more effect, acquires anew the 
 property of affording black molecules. 2. The stuffs are aired 
 during the repose of the dyeing ; whence the hue of the mole- 
 cules is deepened. 
 
 We stated in the theoretical part, that the black dye was only 
 a very condensed colour, and that it assumed more intensity 
 from the mixture of different colours likewise deep. It is, for 
 this reason, advantageous to unite several astringents, each com- 
 bination of which produces a different shade. But blue appears 
 the colour most conducive to this effect, and it corrects the ten- 
 dency to dun which is remarked in the black produced on stuffs 
 by the other astringents. 
 
 On this property is founded the practice of giving a blue 
 ground to black cloths, w^hich acquire more beauty and solidity 
 the deeper the blue. Another advantage of this practice, is, to 
 diminish the quantity of sulphuric acid which is necessarily dis- 
 engaged by the precipitation of the black molecules, and which 
 would not only counteract their fixation, but would further 
 weaken the stuff, and give it harshness. 
 
 For common stuffs, a portion of the effect of the blue ground 
 is produced by the rooting. 
 
 The mixture of logwood with astringents contributes to the 
 beauty of the black in a twofold way. It produces molecules of 
 a hue different from what the astringents do, and particularly 
 blue molecules, with the oxyde of copper, commonly employed 
 in the black dyes ; which appears to be more useful, the more 
 acetate the verdigris made use of contains. 
 
 The boil of weld, by which the dye of black cloth is fre- 
 quently finished, may also contribute to its beauty, by the shade 
 peculiar to its combination. It has, moreover, the advantage of 
 giving softness to the stuffs. 
 
 The processes that are employed for wool, yield, according 
 to the observation of Lewis, only a rusty black to silk ; and 
 cotton is hardly dyed by the processes proper for wool and silk. 
 Let us endeavour to ascertain the conditions which these three 
 varieties of dyeing demand. 
 
268 
 
 BERTHOLLET ON DYEING. 
 
 Wool has a great tendency to combine with colouring sub- 
 stances J but its physical nature requires its combinations to 
 be made in general at a high temperature. The combination 
 of the black molecules may therefore be directly effected in a 
 bath, in proportion as they form ; and if the operation be pro- 
 longed by subdividing it, it is only with the view of changing 
 the necessary oxydizement of the sulphate, and augmenting that 
 of the colouring particles themselves. 
 
 Silk has little disposition to unite with the black molecules. 
 It seems to be merely by the agency of the tannin, with which 
 it is previously impregnated, that these molecules can fix them- 
 selves on it, especially after it has been scoured. For this 
 reason, silk baths should be old, and have the colouring par- 
 ticles accumulated in them, but so feebly suspended as to yield 
 to a weak affinity. Their precipitation is counteracted by the 
 addition of gum, or other mucilaginous substances. The obstacle 
 which might arise from the sulphuric acid set at liberty, is 
 destroyed by iron filings, or other bases. Thus, baths of a very 
 different composition, but with the essential condition of age, 
 may be proper for this dye. 
 
 Cotton and linen have a great propensity to combine with 
 the oxyde of iron, so that they withdraw a portion of it even 
 from its solutions in acids. If those processes be considered 
 which are employed in calico printing, and which are capable 
 of guiding us in dyeing cotton and linen, it is apparent that 
 the application of the mordant is the first step, so that the 
 cloth is, first of all, combined with the oxyde of iron ; after 
 which it is turned through the dyeing bath. 
 
 When black, red, and violet are wished for at the same time, 
 a bath of madder is employed, which affords all these three 
 colours at once, according to the base which fixes the colouring 
 molecules on the different portions of the cloth. The black 
 thereby obtained is, in reality, merely a very deep but durable 
 violet. This is the most ordinary process. If yellows or greys 
 be wished for along with the black, sumach is made use of. 
 
 When cloths are to have only black and white colours, a 
 decoction of logwood is employed, which affords a finer and less 
 costly black, but one a little less durable. 
 
 We have ascertained, that by imitating these processes, add- 
 ing a little acetate of copper, making a mixture of different 
 astringents, and substituting the pyrolignous for the ordinary 
 
OF BLACK. 
 
 269 
 
 acid, blacks may readily be produced of a satisfactory beauty, 
 whose vivacity is increased at the same time that the harshness 
 derived from the dye is diminished, by means of the oil with 
 which the stulf is impregnated. 
 
 CHAPTER III. 
 Of Grey, 
 
 The shades of black are grey, from the brownest to the 
 lightest. The greys may be made in two modes. 1. A decoc- 
 tion of pounded gall-nuts is prepared, and the sulphate of iron 
 is separately dissolved. A bath is made corresponding to the 
 quantity of stuff, which is to be dyed of the lightest shade ; and 
 when it is as hot as the hand can bear, the decoction of nut- 
 galls, and the solution of sulphate are poured into it. The 
 wool or stuff is then turned through it. When it has come to 
 the wished-for shade, it is withdrawn ; and some decoction and 
 solution are added to the same bath. A stuff is turned through 
 this^ to give it a deeper shade than the preceding. Thus the 
 operation is continued to the brownest shades, always adding 
 more of the two liquors. But it is better for the black-grey, 
 and the other deep shades, to give previously to the stuff a 
 stronger or weaker blue ground. 
 
 The second mode of making grey, which Hellot found to be 
 preferable to the one just described, because the decoction of 
 galls takes better on stuffs, and because there is more certainty 
 of employing only the proportion of sulphate of iron required 
 for the shade, consists in boiling for two hours the quantity of 
 nut-galls judged proper, having bruised and enclosed them in 
 a thin linen bag. The stuff is then boiled in this bath for an 
 hour, (en palliant,) stirring it up well with the rake, after 
 which it is lifted out. There must now be added to this same 
 bath a little solution of sulphate of iron ; and the stuff being 
 turned through it, thus acquires the lightest shade. More 
 solution of iron is to be progressively added, till the deepest 
 hues be produced. 
 
 In both of these methods the brownest shades may be begun 
 with, when there is no restraint from patterns, of which the 
 
270 
 
 BERTHOLLET ON DYEING. 
 
 precise hue is to be hit. In the latter process each piece of 
 stuff is left in, for a longer or shorter time, till it take the 
 wished-for shade. 
 
 It is not possible to fix beforehand the dose of the ingredients, 
 the quantity of water, and the time necessary for each of these 
 operations. The eye alone mast judge of them. If the bath 
 be strongly charged with colour, the wool need remain a shorter 
 period ; but if the bath begins to get exhausted, it will require 
 more time. When the stuff is found to be not dark enough, 
 it is returned a second, a third time, &c. ; but if the colour be 
 too deep, it becomes necessary to pass the stuff through a fresh 
 tepid bath, into which a little decoction of galls had been put, 
 or even through a bath of soap or alum. If thus, however, we 
 go beyond the mark, it is requisite to re-brown the stuff. 
 Reiterated operations are prejudicial to it ; hence it is proper 
 to attempt to catch the desired shade at once, by withdrawing 
 the cloth occasionally from the bath. 
 
 Care must be had that the bath do not boil, and that it be 
 rather tepid than too hot. In whatever manner the greys are 
 dyed, they should be immediately washed in a great body of 
 water ; and the brown-greys should be even scoured with soap. 
 
 It is frequently desired to mingle with grey the tint of an- 
 other colour, as a reddish, agate, or hazel cast. In this case, 
 after giving a greater or smaller tint of blue, according to the 
 object proposed, the stuffs are turned through a spent cochineal 
 bath, which has served either for scarlet or violet, adding to it 
 gall-nuts, logwood, madder, &c. Thereafter a browning of 
 greater or less depth is given with solution of iron. For hazel, 
 old fustic and logwood are added to the galls, and the dyeing 
 is given on a white ground. All the greys, except black-grey, 
 are applicable on silk without aluming. The bath is composed 
 with fustet, logwood, archil, and sulphate of iron. These in- 
 gredients are varied according to the shade to be given. Thus 
 more archil is employed for greys that are to have a reddish 
 cast ; more fustet for those which ought to incline to a russet or 
 green ; and lastly, more logwood for such as are to have a darker 
 grey. For the iron-grey, logwood and solution of iron are 
 had recourse to. 
 
 The black-grey requires aluming, after which the silks are 
 taken to the river, and then receive a bath of weld. A portion 
 
OF BLACK. 
 
 271 
 
 of this bath is thrown away to substitute for it the extract of 
 logwood. When the silk has been impregnated with this, so- 
 lution of iron is added in sufficient quantity ; and when the 
 desired shade is hit, the silk is washed and wrung. 
 
 If the grey come out deeper than is desired, the silk is turned 
 through a solution of tartar, and then through hot water; and 
 if the colour be too much weakened, a fresh dye-bath is given it. 
 
 For linen and cotton, a blue ground is given to black-grey, 
 iron-grey, and slate-grey, but not to the other greys. All the 
 shades require a galling proportioned to the grey which is 
 wished to be procured. Baths of nut-galls that had been pre- 
 viously used are often employed. 
 
 When the yarn has been galled, wrung, and dried, it is turned 
 over the sticks in a bucket full of cold water, to which a suit- 
 able quantity of the black cask,* and of decoction of logwood, 
 is added. The yarns are worked in it in separate portions, then 
 wrung out, washed, and dried. 
 
 Le Pileur d'Apligny gives two other processes for making 
 grey, of which he pretends the dye to be more fixed. 
 
 1. The yarn is galled, turned through a very weak black hath, 
 and afterwards maddered. 
 
 2. The yarn is turned through a very hot solution of tartar, 
 slightly wrung, and dried. This yarn is then dyed in a decoc- 
 tion of logwood. The dye appears black ; but on turning 
 through and working the yarn with attention in a hot solution 
 of soap, the surplus of the dye is discharged, and there remains 
 an agreeable and solid slate-grey. 
 
 A process, the success of which is known to us, consists in 
 taking a very dilute solution of acetate of iron, (it is sufficient 
 to add a little of this acetate to a quantity of water,) and a 
 decoction of sumach, also very dilute. The cotton is passed in 
 succession from one liquor to the other, till the wished-for shade 
 be attained. The finish is given by passing through a water 
 slightly acidulated by sulphuric acid, otherwise the sumach gives 
 a russet hue. By the same process may be obtained with nut- 
 galls less lively greys ; and the alder bark aflfcrds an agreeable 
 one, which borders on hazel. 
 
 A skilful manufacturer of Rouen has communicated to us the 
 
 * See Part I. p. 227. 
 
^72 
 
 BERTHQLLET ON DYEING. 
 
 following process, which he makes use of successfully for 
 cotton velvets. A galling is given with an equal quantity of 
 gall-nuts and logwood, after which a bath of cold water is admi- 
 nistered, and next another bath of water, in which there has 
 been dissolved a weight of sulphate of iron, equal to the one- 
 half of the preceding ingredients. After working the cotton 
 about a quarter of an hour in this bath, it is rinsed in cold 
 water, and brightened. 
 
 For this purpose a bath of tepid water is used, to which one- 
 eightieth of decoction of weld, and a little alum, are added. 
 The cotton is left about twenty minutes in this bath, after which 
 it is washed in cold water, and dried. 
 
 By modifying the doses of the ingredients, greys from pearl- 
 grey to the deepest grey may be thereby obtained. 
 
 For greys on printed goods, the same mordant is impressed as 
 for a clear violet, and sumach or gall-nuts are employed accord- 
 ing to the shade that is desired. 
 
SECTION II. 
 
 OF BLUE. 
 
 CHAPTER L * 
 Of Indigo. 
 
 Indigo is a blue colouring substance extracted from a plant, 
 which is known under the names of anil^ indigofera, and indigo. 
 
 The plant from which the indigo is obtained, or the indigo- 
 fera^ is cultivated in China, Japan, India, Madagascar, Egypt, 
 and South America. There are several species of it ; but in 
 America, three are particularly distinguished. The indigo franc, 
 or indigofera tinctoria, Linn. : it is the smallest, and produces 
 the indigo of the lowest quality ; but as it yields a larger quan- 
 tity, it is often preferred. The second is the indigofera dis- 
 perma. Linn., the species cultivated in Guatimala. It is taller, 
 and more woody than the preceding. It affords a better indigo. 
 The third is the indigofera argenfea, or bastard indigo, which is 
 still more woodj^ than the last. It furnishes the finest indigo, 
 but in smaller quantities than the others. 
 
 It would appear that this plant absorbs more foreign matters 
 the more herbaceous it is. These are afterwards blended with 
 the colouring particles. 
 
 When the indigofera exhibits the first signs of maturity, it is 
 cut, and carried into vats, where it undergoes a fermentation, to 
 which it is naturally prone. When it is cut down in a state of 
 complete maturity, it affords a finer colour, but in less quantity. 
 If it be cut too late, more of the substance is then lost, and an 
 indigo of worse quality is obtained. 
 
 Three vats are placed one over another, at different heights, 
 near a reservoir of water. The first is termed the steeper, (irem- 
 poir.) Into this, filled with water to a certain height, the plant 
 is put. Here a very brisk kind of fermentation soon begins, 
 and much froth is thrown up. The gas that is disengaged is 
 partly inflammable, 
 
 T 
 
BERTHOLLET ON DYETNG. 
 
 When the indigo maker ascertains that the fermentation is 
 sufficiently advanced, and that the colouring particles have a 
 tendency to separate, he runs off the liquor into the second vat, 
 which is named the beating-vat, {batterie,) in which the liquor 
 is subjected to a beating with instruments constructed on pur- 
 pose. Le Blond, in some observations which he sent to the 
 Academy of Sciences, says, that this operation is intended for 
 dissipating the carbonic acid generated in the fermentation, 
 which hinders the colouring particles from falling down. He 
 states, that the beating is not sufficient to effect the precipitation 
 of all the colouring particles, and that in French Guyana a process 
 has been tried, which, by causing a more copious precipitation, 
 has revived the hopes of the planters, who had given up this 
 kind of manufacture. It consists in mixing a certain quantity of 
 lime water with the liquor, whereby its carbonic acid is absorbed ; 
 but he conceives that the due proportion must not be exceeded, 
 because too much lime water is prejudicial. This method was 
 not unknown. P. Labat makes mention of it. Struve also 
 thought that lime w^ater promoted the precipitation of the 
 indigo, by seizing the carbonic acid which held it in solution.* 
 
 When it is inferred from the blue colour that the beating 
 has been sufficient, the vat is allowed to settle for two hours, 
 that the colouring particles may begin to separate from the 
 liquor, which contains a yellow extractive matter. It is now 
 passed into a third vat, called the diablotin, (settling vat.) Here 
 the colouring particles are suffered to subside ; and the super- 
 natant liquid is run off, in succession, by two stopcocks placed 
 one above the other ; after which the colouring particles them- 
 selves, which have a semi-fluid consistence, are drawn off, by a 
 third stopcock, into conical linen strainers. When they are 
 reduced to the consistence of a paste, they are turned out into 
 square boxes, in the open air, which are placed under shades 
 to shelter them from the sun. 
 
 The indigo produced in these operations differs not only 
 according to the quality of the plant which afforded it, but also 
 according to the pains taken in the preparation. Its colouring 
 part, however, seems to be an uniform substance. Hence the 
 qualities that distinguish it depend particularly on the propor- 
 
 * Bihliot. medico-pbysiqiie du Nord, torn. iii. 
 
OF BLUE. 
 
 275 
 
 tion of the foreign parts blended with it, and on the greater 
 or less consistence which it has taken in drying. 
 
 There is a light variety, called light indigo, or flower indigo, 
 which comes from Guatimala, and is of a beautiful blue. It 
 floats on water, whereas the other kinds fall to the bottom of 
 this fluid. It is the finest and the riiost precious sort. There 
 is another, known under the name of coppery indigo, because 
 its surface assumes the colour of copper when it is rubbed with 
 a hard body. Lastly, there are much less pure kinds, as that 
 from Carolina. 
 
 The blue molecules of indigo, however, independently of 
 foreign substances, owe a part of their properties to the pre- 
 paration itself. 
 
 When the leaf of indigo is bruised, its juice speedily assumes 
 a blue colour in the air. If, after bruising it, the juice be ex- 
 tracted by infusion, on leaving this solution in the air it grows 
 turbid, and a greenish blue fecula falls down, which preserves 
 this green shade, notwithstanding repeated lotions, and a long 
 exposure to the atmosphere. In Egypt, where the arts have 
 made little progress, the plant is merely bruised, infused in. hot 
 water, which is then run off" into a pit of argillaceous earth, in 
 which it is agitated with beaters, to cause the precipitation of 
 its fecula ; but the indigo thus obtained is always greenish, and 
 affords a bad colour. In this state it seems more disposed to 
 dissolve by means of fermentation ; for the dyers require only 
 to mix raw sugar with it, in order to establish the vats which are 
 used for dyeing. A French artisan extracted a fine indigo, by 
 subjecting the plant to the same preparations as in other coun- 
 tries. 
 
 The three parts of the process employed, have each a different 
 object. In the first, a fermentation is excited, in which the 
 action of the atmospheric air does not intervene, since an inflam- 
 mable gas is evolved. There probably results from it some 
 change in the composition of the colouring particles themselves ; 
 but especially the separation or destruction of a yellowish sub- 
 stance, which gave to the indigo a greenish tint, and rendered it 
 susceptible of suffering the chemical action of other substances. 
 This species of fermentation passes into a destructive putrefac- 
 tion, because the indigo, as we shall see, has a composition 
 analogous to that of animal substances. 
 
 T 2 
 
276 
 
 BERTIIOLLET ON DYEING. 
 
 Hitherto the colouring particles have preserved their liquidity. 
 In the second operation, the action of the air is brought into 
 play, which by combining with the colouring particles, deprives 
 them of their solubility, and gives them the blue colour. The 
 beating serves, at the same time, to dissipate the carbonic acid 
 formed in the first operation, whose action is an obstacle to the 
 combination of the oxygen. The separation of' this acid is 
 promoted by the addition of the lime ; but if a redundant 
 quantity be introduced, the excess would act upon the indigo 
 and counteract the free combination of the oxygen. 
 
 The third part of the process has for its objects the deposi- 
 tion of the colouring part, become insoluble by combination 
 with oxygen; its separation from foreign substances; and its 
 desiccation, which gives it more or less hardness, whence its 
 appearance varies. 
 
 Indigo is not only of very extensive use in dyeing,' but its 
 chemical properties are very remarkable. They explain, in a 
 clear and positive manner, those processes of dyeing, in which they 
 are used ; they point out interesting analogies with other pheno- 
 mena. For these reasons, we shall present, at some detail, the 
 observations of the chemists who established this theory. We 
 owe it especially to Bergmann. 
 
 In the experiments of this great chemist,* water dissolved, 
 by means of ebullition, a ninth part of the weight of the indigo. 
 The portion dissolved by the water appeared partly astringent, 
 partly mucilaginous, and partly saponaceous. The solution of 
 alum, and of sulphate of iron and copper, precipitated its 
 istringent parts. 
 
 Quatremeref also separated by means of water the parts 
 which are soluble. He states their quantity to be more con- 
 siderable, the worse the quality of the indigo ; and that, after 
 this operation, the residuum has acquired the qualities of the 
 finest indigo. He therefore proposes to purify what is of inferior 
 quahty, by boiling it in a bag, and renewing the water till it 
 ceases to acquire colour. This operation would undoubtedly be 
 beneficial, since the indigo would thereby be deprived of the 
 
 * Analyse et examen cliimiqne de Tindigo. Mem. des Savans etrang. torn. ix. Opnsc. 
 tom. V. 
 
 t Analyse et examen chimique de Tindigo, tel qu'il est dans le commerce, pour Tusage 
 de la teinture, Mem. des Savans etrang. tom. ix. 
 
OF BLUE. 
 
 277 
 
 yellowish particles which may alter its colour. Yet there are 
 probably differences in the nature of the colouring particles 
 themselves, and in the insoluble earthy matters, which could not 
 in fact injure the colour, but might change the proportions of 
 the colouring particles. 
 
 The powder of indigo, digested in alcohol, gave at first a yel- 
 low tincture, then red, and lastly brown. It lost, by this opera- 
 tion, repeated several times, about one-seventeenth of its weight. 
 Water separates from this tincture a brownish resinous matter. 
 
 Ether acts on indigo nearly like alcohol ; but the oils, both 
 fixed and volatile, have little action on it. 
 
 Bergmann mixed one part of indigo, well pulverized, with eight 
 parts of colourless sulphuric acid, of specific gravity 1.90. The 
 glass bottle in which the mixture was made was slightly corked. 
 The acid speedily attacked the indigo, and excited a great heat. 
 After a digestion of 24 hours, the indigo was dissolved ; but the 
 mixture was opaque and black. On adding water it cleared up, 
 exhibiting successively all the shades of blue, according to the 
 quantity of water. It requires, at least, 22 pounds of water in 
 a cylindrical glass vessel, of 7| inches diameter, to render the 
 smallest drop of this solution imperceptible. 
 
 If sulphuric acid be diluted with water, it attacks only the 
 earthy matter that is blended with the indigo, and some mucila- 
 ginous ingredients. 
 
 Several goblets in which a drop of this solution was mixed 
 with liquids, which contained different substances, such as acids, 
 alkalies, neutral salts, were exposed for some time to a tempera- 
 ture of 15^ or 20° R., (66° or 77° Fahr.) In some the colour 
 was preserved without alteration ; in others it became green, and 
 was destroyed more or less speedily. Bergmann explains the 
 changes which he observed, by the property which some sub- 
 stances possess of carrying off* phlogiston and others of giving 
 it. They are happily explained by the affinities of oxygen, 
 which some substances afford, carry off*, or absorb from the 
 atmosphere. 
 
 The fixed alkalies, saturated with carbonic acid, separate 
 from the solution of indigo a very fine blue powder, which is 
 very slowly deposited. Bergmann distinguishes this blue powder 
 by the name of precipitated indigo. It is also obtained by 
 pouring, drop by drop, the alcoholic solution into saturated 
 
278 
 
 BERTHOLLET ON DYEING. 
 
 solutions of aUim^ of sulphate of soda, or of some other salts 
 which contain sulphuric acid ; but the liquid remains always a 
 little coloured. 
 
 Muriatic acid digested, or even boiled with indigo, takes up 
 the earthy part, the iron, and a little extractive matter, which 
 colours it yellowish brown, but without attacking in any manner 
 the blue colour. If indigo be precipitated from sulphuric acid 
 in this case, muriatic acid dissolves very easily a certain quantity 
 of it, and forms a deep blue liquid. 
 
 The other acids, as the tartaric, formic, acetic, and phosphoric, 
 comport themselves with indigo like muriatic acid. They dis- 
 solve precipitated indigo very well. Sulphuric acid, when too 
 much diluted with water for dissolving indigo, and nitric acid, 
 also too weak for decomposing indigo, only dissolve the earthy 
 portion and the extractive matter, which are foreign to the 
 colouring substance. 
 
 Concentrated nitric acid attacks indigo with such violence as 
 to inflame it. If it be weakened to a due degree, it acts with 
 less vivacity. The colour of the indigo becomes ferruginous, 
 (ochrey.) The residuum, after this operation, has the appearance 
 of the earth of umber, and forms in weight only one-third of 
 the indigo. The fixed alkali precipitates a little oxyde of iron, 
 mixed with barytes and calcareous earth, from the nitric acid 
 which has acted on the indigo ; but if too much alkali be added, 
 a portion of the precipitate is re-dissolved, rendering the colour 
 of the liquor deeper than it was before. 
 
 Haussman, in a very interesting dissertation, describes a con- 
 nected series of observations on the changes which nitric acid 
 produces on indigo.* When the whole indigo seemed destroyed, 
 there was found a coagulum, which, after being deprived of all 
 the nitric acid by washing, formed a brown and viscous mass, 
 which dissolved in alcohol, and was soluble only in a great 
 quantity of water. It possessed considerable bitterness. The 
 water which has served for the lotions, afforded by evaporation 
 small crystals, which were probably oxalic acid. 
 
 Chlorine has little action on indigo in substance. But this 
 inaction depends only on its cohesion, for it easily destroys the 
 colour, and changes the composition of indigo when in solution. 
 
 * Jouin. de physique, 1788. 
 
OF BLUE. 
 
 279 
 
 If the liquid be evaporated after this destruction is effected, 
 there is found a blackish substance analogous to what results 
 from the decomposition by nitric acid. 
 
 The decomposition by nitric acid and by chlorine is reciprocal, 
 and the effects depend on the passage of the oxygen of one of 
 these acids, into a more intimate combination with the hydrogen 
 and carbon, especially with the hydrogen. A combination is 
 formed in which the carbon predominates, but in proportions 
 determined by circumstances. 
 
 Sulphuric acid is, therefore, the only one which dissolves 
 indigo ; but we shall see that it produces this effect only by 
 means of a change of composition, which alters very little the 
 colour of the indigo, but renders it soluble in the other acids 
 and the alkalies. 
 
 Fixed alkali dissolves some substances distinct from the co- 
 louring part of indigo ; but it attacks slightly the colouring 
 particles themselves. Ammonia, or the caustic volatile alkali, 
 acts nearly in the same manner. Precipitated indigo dissolves 
 readily, and in the cold, in the alkalies, whether fixed or vola- 
 tile, if they be pure or caustic. Their blue colour changes 
 gradually to green, and is eventually destroyed. But if the 
 alkalies be combined with carbonic acid, they do not produce 
 this effect. Lime water has little action on indigo, but it dis- 
 solves what has been precipitated. It alters and finally destroys 
 its colour, nearly like the caustic alkalies. 
 
 Indigo exposed to the action of fire in an open crucible, or 
 under a muffle, smokes, swells up, reddens, and sometimes even 
 takes fire, evolving a white flame. One hundred parts of indigo 
 leave thirty-three or thirty -four parts of ashes. 
 
 These ashes do not afford fixed alkali, when they are lixiviated 
 with distilled water. Muriatic acid dissolves the greater part 
 of them with effervescence. The residuum, which is insoluble, 
 forms an eleventh part, and has the characters of siliceous earth. 
 
 The solution made in muriatic acid produces prussian blue, 
 on mixing it with prussiate of potash; but the iron thereby 
 separated is not to be confounded with that which enters only 
 into the colouring particles. 
 
 Besides iron and siliceous earth, the ashes contain calcareous 
 earth and barytes. 
 
 Indigo detonates strongly with nitre. It afforded by distil- 
 
280 
 
 BERTHOLLET ON DYEING. 
 
 lation carbonic acid, a liquor which contained a little volatile 
 alkali, and an oil similar to the empyreumatic oil of tobacco, 
 which dissolved very well in alcohol. 
 
 Bergmann concludes from his analysis, that 100 parts of good 
 
 indigo contain — 
 
 Mucilaginous parts separable by water . . . .12 
 Resinous parts soluble in alcohol ..... 6 
 Earthy parts soluble in acetic acid, which does not attack 
 
 the iron here in the state of an oxyde . . , .22 
 Oxyde of iron dissolved by muriatic acid . . . .13 
 47 parts remain, which are colouring molecules almost 
 
 pure, and which when distilled afforded — 
 Carbonic acid . . . . .2 
 
 Alkaline liquor .... 8 
 
 Empyreumatic oil . . . .9 
 
 Charcoal ... . . 23 
 
 The charcoal, when burned in the open air, yielded four parts 
 of earth, of which about one-half was oxyde of iron, and the 
 remainder a very subtile siliceous powder. 
 
 It results from this analysis, that pure indigo contains nearly 
 the same elements as animal substances, and it is to be supposed 
 that some phosphate will be discovered in the ashes ; but what 
 distinguishes it from animal bodies, is the large quantity of 
 charcoal which must give to its composition a greater stability 
 than ordinary animal substances possess. We have, however, 
 already seen that if its preparations have not been made with 
 skill, it might experience the effects of putrefaction. It is 
 thereby altered or destroyed. That whose fermentation is 
 pushed too far becomes black ; it is termed burned indigo. 
 (Note GG.) 
 
 Bergmann ascribes its colour to iron, comparing it to the 
 prussiate of iron,' and to the black molecules formed by the 
 combination of an astringent with the oxyde of iron. This 
 comparison does not appear to us exact. The iron present in 
 the colouring particles of indigo, constitutes seldom more than 
 the thirtieth part of their weight. The modifications which 
 they receive from the combination of oxygen, or its expulsion^ 
 which we shall presently examine, do not correspond to the 
 effects of the oxydation of this metal. It seems therefore more 
 
OF BLUE. 
 
 281 
 
 proper to consider the colour of indigo as a result of the reci- 
 procal action of all its elements, than as a property derived 
 from one of them. 
 
 It has been seen that the alkalies and lime do not dissolve 
 indigo ; but in the processes made use of,- it becomes soluble 
 in these substances, from which it is afterwards precipitated on 
 the matters that are dyed. The solution of indigo in alkali or 
 lime is greenish ; it becomes blue at its surface, because the 
 indigo is precipitated from it under its natural form. Bergmann 
 remarks, that this green colour is not produced by the alkalies, 
 as happens with several other vegetable substances. For these 
 blue parts which have become green, recover their colour when- 
 ever the alkali is saturated with an acid, which itself would give 
 them a red colour. But the particles of the indigo must have 
 undergone a change, so as to become soluble in the alkalies ; 
 and the acids have not the property of making them red. Our 
 object is now to examine what change the particles of indigo 
 suffer in order to be dissolved in the alkalies. 
 
 Bergmann examines two processes, with the view of ascertain- 
 ing the cause of the changes experienced by indigo. We shall 
 enter into further details on these processes, when we come to 
 examine them as dyeing operations. It is enough at present 
 to indicate them. If sulphate of iron, dissolved in water, be 
 mixed with its own weight of indigo, and double its weight of 
 lime, the indigo is soon dissolved. But Bergmann has observed, 
 that if the sulphate of iron be kept boiling in a great deal of 
 water for several hours, and if this water be reduced by evapor- 
 ation to a proper quantity, the solution can no longer take 
 place. If to a solution of pure or caustic fixed alkali, indigo 
 and sulphuret of arsenic or orpiment be added, the bath soon 
 becomes green, and the solution of indigo is accomplished. If, 
 for the sulphuret of arsenic, be substituted the proportion of 
 arsenic which it contains, the bath will never be fit for dyeing ; 
 but on adding to it the proper quantity of sulphur, symptoms 
 of solution will soon be seen. 
 
 Bergmann ascribed these effects to the phlogiston communi- 
 cated to the indigo, in the first case, by the precipitate of iron ; 
 and in the second, by the sulphuret of arsenic, through the 
 agency of which it has become soluble in the alkali and lime. 
 Hence, when the precipitate of iron has been deprived of its 
 
2S2 
 
 BERTHOLLET ON DYEING. 
 
 phlogiston by a long ebullition, it ceases to be able to dissolve 
 indigo. 
 
 For this hypothesis, ^vhich might enable us sufficiently to 
 foresee the results, we have merely to substitute the explana- 
 tion founded on the positive effects of oxydation and deoxy- 
 dation. 
 
 When indigo has assumed a blue colour, it contains a certain 
 proportion of oxygen, which renders it insoluble. It may be 
 compared to a metal, which, at a certain degree of oxydation, 
 becomes insoluble in the acids, and which resumes its insolu- 
 bility by the action of substances which can diminish its oxy- 
 dation. Indigo is rendered soluble by the substances which can 
 deprive it of a variable quantity of this element. The recent 
 precipitate of sulphate of iron attracts oxygen powerfully from 
 the atmospheric air, as Priestley has shown. It must exercise 
 a similar action on indigo, and render it soluble. When the 
 alkali acts on the sulphuret of arsenic, it precipitates from it 
 the arsenic which is in the metallic state, robbing it of a portion 
 of its oxygen. In this case, it acts on oxygen like the preci- 
 pitate of iron, and in the same way renders the indigo soluble ; 
 but the co-operation of the oxydable metal is required. Oxyde 
 of arsenic produces no effect. 
 
 The deoxydation, however, would not alone suffice, nor would 
 it give a great enough solubility in water. The action of a 
 substance possessing the property of uniting with the deoxy- 
 dized indigo, and increasing its solubility, must be joined, in 
 order to prepare it for dyeing. This is the function of the 
 fixed alkalies and the lime, in the different processes employed. 
 It results from this twofold action, that, on one hand, the indigo 
 is deoxydized, while, on the other, it enters into a liquid com- 
 bination with the alkali or the lime. 
 
 That this double action is essential, is evident ; because the 
 sulphuret of potash, or of soda, does not effect the solution of 
 indigo, although it strongly attracts the oxygen, in order to be 
 converted into a sulphate. The incompetency of its action 
 must be ascribed especially to the resistance offered by the 
 cohesive force of the indigo. 
 
 Some experiments of Haussman serve to confirm this theory. 
 He put a solution of indigo, made by means of alkali and orpi- 
 ment, in contact with the gas extracted from nitre by distilla- 
 
OF BLUE. 
 
 283 
 
 tion with heat, which is oxygen gas with a small proportion 
 of azote. The whole of the oxygen was absorbed, while the 
 indigo separated, resuming its blue colour, and the insolubility 
 belonging to it in this state. The metal was reduced to an 
 oxyde. The sulphur formed a sulphate with the alkali, and 
 the excess of the alkali could not retain in solution the indigo 
 restored to its natural condition.* 
 
 To Haussman we owe several other interesting observations. 
 The sulphuret of antimony determines the solution of indigo 
 equally with the sulphuret of arsenic ; but this solution cannot 
 be employed like that of the sulphuret of arsenic, because the 
 metal forms a red precipitate, which is probably a sulphuretted 
 oxyde of antimony. This oxyde, mixed with the sulphur, does 
 not produce solution. Iron, in the metallic state, put into a 
 concentrated alkaline liquor, along with indigo ground in water, 
 did not, any more than zinc, determine its solution. Their 
 force of cohesion, undoubtedly, counteracts this effect, while 
 antimony, in the metallic state, was able to occasion the solution. 
 
 The precipitate of copper, far from contributing to the solu- 
 tion of indigo, produced a contrary effect. It caused its rege- 
 neration in solutions made by means of sulphuret of arsenic or 
 of antimony, as well as in that occasioned by the precipitate 
 of iron. The solution of copper in ammonia acted in the same 
 way. Haussman says, that the dyers take advantage of this 
 property of copper, to exhaust more speedily the blue vats, 
 which, when they have served too long, or are naturally little 
 loaded with indigo, would furnish only very weak shades ; while 
 deeper ones are obtained by passing the pieces, before dyeing 
 them, through a water slightly impregnated with sulphate of 
 copper, or other cupreous solution, acid or alkaline. But the 
 dyers of whom he speaks are in a mistake. When a solution of 
 copper is poured into a transparent solution of indigo, the latter 
 becomes of a deep blue, and the regenerated indigo is precipit- 
 ated. In like manner, cloth impregnated with a solution of 
 
 * All the effects which we explain by the oxydation and deoxydation of the indigo, 
 might be accounted for by supposing that the indigo is rendered soluble by an excess of 
 hydrogen, and that the means which restore it to its blue colour, carry off from it this 
 hydrogen. But this second explanation requires the admission of decompositions of water 
 by causes of small energy, and it is not supported by the analogy of the oxydations of the 
 metals, sulphur, phosphoius, &c. Hence, the one we adopt appears to have at least much 
 more probability. 
 
284 BERTHOLLET ON DYEING. 
 
 copper, on being plunged into a vat^ comes out of it instantly of 
 a deep blue, but washing removes this completely. This is, 
 therefore, a means of quickly exhausting the vats, to the detri- 
 ment of what the stuffs could take from it ; for the regenerated 
 indigo contracts no union with them. We shall see, that ad- 
 vantage is taken of this property of copper, to reserve (protect) 
 the parts of a stuff in an indigo bath. 
 
 The oxyde of copper produces these effects by the facility 
 with which it gives up its oxygen to indigo that has been de- 
 prived of it. The oxyde of tin, which has a contrary disposi- 
 tion, ought to act differently. 
 
 Bancroft found that tin, slightly oxydized, when mixed with 
 an alkaline solution of indigo, speedily effected a solution of the 
 latter, thereby forming, as is said, a good vat. 
 
 Tin, oxydized with a strong heat, or by the detonation of 
 nitre, not only did not effect the solution of indigo, but it even 
 counteracted it, on being mixed with the sulphuref of arsenic or 
 antimony, or the precipitate of iron, so that in this state it gave 
 up a portion of its oxygen. 
 
 Tin, slightly oxydized, may be dissolved directly in potash, 
 and this solution acts on indigo. It quickly produces a vat, in 
 which cloths are dyed of a very intense blue. 
 
 In all the processes employed for establishing the solutions 
 of indigo, called vats, which we shall describe, there is present, 
 conformably to the theory, several substances which, by an 
 action more or less slow, serve to carry off the oxygen, while 
 the lime, fixed alkali, or even the ammonia, unite to the deoxy- 
 dized indigo, and give it more solubility. 
 
 It appears that indigo passes by these means through different 
 degrees of deoxydation, so that its solution assumes different 
 shades- In the most advanced state its solution is colourless ; 
 with less oxydation it passes to a yellow, and finally to a green- 
 ish hue. 
 
 While indigo is in solution, the portion of it in contact with 
 the air absorbs oxygen, which combines with the indigo, and re- 
 generates it, saturating, at the same time, the substance which 
 tended to seize it, so that the surface becomes blue. Thence the 
 froth, green at first, and then blue, is called fleuree, which is 
 formed in well constituted vats, when they are agitated. 
 
 Indigo, when in the liquid state, easily forms combinations. 
 
OF BLUE. 285 
 
 It then unites to stuffs, and abandons the alkalies, which have 
 but a feeble action on it. Notwithstanding the more intimate 
 combination which it thus forms, it attracts oxygen, when the 
 stuff is exposed to the contact of air, so that from yellow or 
 green it passes speedily to blue. The same effect is produced, 
 if on coming out of the bath it be dipped in very weak chlorine 
 solution. It thereby appears, that if cloth cannot combine 
 directly with indigo, it is only in consequence of the counteract- 
 ing force of cohesion. 
 
 Some vats are prepared and used in the cold, others are em- 
 ployed hot. The same difference is remarked here, in reference 
 to stuffs, as in the most part of other dyes. Wool combines 
 with a great deal of indigo. Its combination is very durable, 
 but it requires heat, which disposes it to be formed. Silk takes 
 a deep blue with more difficulty. Cold vats are proper for 
 cotton and linen. 
 
 When indigo is dissolved by sulphuric acid, it gives a lively 
 colour to stuffs. We shall examine this process ; but the 
 colour is much less solid than that produced by the ordinary 
 vats ; and we have seen, by the experiments of Bergmann, that 
 the precipitate obtained from this solution is different in some 
 of its properties from native indigo, and that it is soluble in 
 the other acids, and in the alkalies. The indigo must there- 
 fore have suffered some alteration in its composition. 
 
 It would seem that the observations which have been made 
 on sugar, and other vegetable and animal substances,* may be 
 applied to the action of sulphuric acid on indigo, and that it 
 determines the formation of a little v^ater, by the intimate com^ 
 bination of a portion of the oxygen and the hydrogen, which 
 enter into the composition of the indigo. Thus, we may ex- 
 plain the great heat which is produced without any sulphurous 
 acid being formed, the state of concentration in which the sul- 
 phuric acid must be, and why other acids, although powerful 
 and concentrated, cannot effect this solution. 
 
 This alteration is, in our opinion, capable of being formed 
 in different degrees ; and when the heat has been rightly tem- 
 pered, we hardly find in it the properties described by Berg- 
 mann, whose accuracy cannot be called in question. 
 
 * Essai dc statique chimie, torn. iv. 530. 
 
286 
 
 BERTHOLLET ON DYEING. 
 
 If sulphuretted hydrogen water be poured into a solution of 
 indigo, diluted with so much water that it has but a faint colour, 
 this is soon seen to disappear, and a little chlorine restores it. 
 
 A hydrosulphuret produces this effect with a much more con- 
 centrated solution. If cotton be immersed in the liquid, it 
 comes out colourless, but soon becomes green, and then passes 
 to blue. A deep colour may be given to it by this means. 
 Here the indigo did not offer any obstacle by its cohesive force ; 
 and the sulphuretted hydrogen, which is condensed, acts power- 
 fully upon it. 
 
 The observations made by Bergmann, on the effects that dif- 
 ferent substances produce on solution of indigo in sulphuric 
 acid, are all easily explained by the property which they may 
 or may not have of seizing its oxygen. 
 
 CHAPTER II. 
 Of Pastel and Woad. 
 
 Pastel is a plant of the cruciform family, whose distinctive 
 character is derived from the form of its silique, which is flat- 
 tened like the fruit of the ash, is edged with a thin membrane, 
 and contains two oblong seeds. Two species of it are distin- 
 guished, of which there are varieties ; the cultivated pastel, 
 isatis tinctoi^ia, Linn., and the pastel of Portugal, isatis lusita- 
 nica, Linn,, which differs from the first in being smaller, and in 
 having narrower leaves. The first species sends out stems a 
 metre high, (a yard,) of the thickness of the finger, which are 
 divided into a number of branches, loaded with many large 
 leaves, which are lanceolate, furnished at their edges with small 
 smooth indentations, and of bluish-green colour. The flowers 
 are yellow, disposed in pannicles at the summits of the stems. 
 The root is thick, woody, and penetrates deeply into the earth. 
 
 This plant requires a good black mould, light, and well im- 
 proved. It is sown in spring, after a double tillage in autumn. 
 Three or four crops are obtained in a year. The first when the 
 stems begin to grow yellow, and the flowers are about to ap- 
 pear ; the others at successive intervals of six weeks or more, 
 according to the climate and heat of the season. 
 
OF BLUE. 
 
 287 
 
 The plant is mown with a scythe, washed in the river, and 
 dried in the sun. Its desiccation must be rapidly performed ; 
 as, if the season be unfavourable, or if it rains, the plant runs a 
 risk of being spoiled, A single night is sometimes sufficient 
 to turn it black. 
 
 The plant is thereafter carried to the mill to be ground and 
 reduced into a paste. This is formed into heaps, which must 
 be covered to protect them from the rain. After fifteen days 
 the pastel mass is opened up and bruised, mixing the in- 
 terior with the crust that has formed upon its surface. It is 
 then formed into balls, which are carried into a place exposed 
 to the wind and the sun, in order to expel the humidity which 
 might cause them to putrefy. These balls, piled one over 
 another, become hot imperceptibly, and exhale an odour of 
 ammonia, which is stronger in proportion as the quantity is 
 larger, and the season more hot. The heat thus begun, is 
 increased by a slight sprinkling of water, till the pastel be 
 reduced to a fine powder. It is now in the state in which it 
 is found in commerce. 
 
 Pastel is cultivated and prepared in several parts of France. 
 That of the southern departments is most esteemed. The name 
 of vouede (woad) is given it, in the departments of the north. 
 Woad differs from ordinary pastel, merely in requiring a larger 
 quantity of it to produce a like effect, as Hellot has proved. 
 
 Pastel afibrds, without indigo, a blue colour which has no 
 brilliancy, but is very durable. As it yields much less colour- 
 ing matter than indigo, and as its colour is inferior in beauty, 
 the discovery of indigo has considerably diminished the culture 
 and sale of pastel. 
 
 Astruc relates, in his memoirs on the natural history of Lan- 
 guedoc, that having treated pastel in the small way as the anil 
 is treated to obtain its indigo, he procured a powder which pro- 
 duced the same effects as indigo. Hellot thence concluded, that 
 the deep green of several plants is owing to yellow and blue 
 particles, and that, if by fermentation the yellow could be de- 
 stroyed the blue would remain. But Lewis says,* that having 
 made different species of plants putrefy in water, he obtained no 
 blue fecula. This mixture of blue and yellow molecules to form 
 
 * The chemical works of Gaspar Neumann, hy William Lewis. 
 
288 
 
 BERTHOLLET ON DYEING. 
 
 the green of plants, is a supposition void of foundation. But 
 some plants of different species appear to contain likewise 
 colouring molecules analogous to indigo ; and the pulp of the 
 fruit of the genippa Americana, Linn,, contains enough of it, 
 according to Bancroft, for dyeing directly a deep blue — a cir- 
 cumstance already mentioned. 
 
 Several attempts have been made in different places to ex- 
 tract an indigo from pastel. It appears that the product is too 
 small, for the colouring substance to enter into competition w^ith 
 ordinary indigo. 
 
 In some parts of Africa, they content themselves with giving 
 the leaves of indigo a preparation similar to what pastel is sub- 
 jected to ; but for extracting the blue fecula of pastel, they 
 imitate the preparation of indigo. We shall now give a de- 
 scription of the operations followed in a manufactory, according 
 to the account of it published by Gren.^ The fresh leaves of 
 pastel are taken, which are washed, to separate the impurities 
 and the earth, in a tub of an oblong form, nearly three-fourths 
 full. To prevent the water from buoying them up, pieces of 
 wood are fixed across. On these leaves enough of pure water is 
 poured to cover them entirely, and the vessel is set in a mode- 
 rate heat. There is formed, according to the temperature of 
 the atmosphere, in a longer or shorter time, a copious froth on 
 the surface of the water, which indicates the commencement of 
 the fermentation. The surface becomes wholly covered by de- 
 grees with a 'blue skin, which presents to the eye shades of 
 copper colour, "Whenever there is a certain quantity of this 
 froth, the liquor, which is of a deep green tint, is drawn off into 
 another oblong vat by a stopcock placed immediately above its 
 bottom, or otherwise the water is lailed out to put it into the 
 other vat. In both cases it is necessary to run the water through 
 a cloth into the other vessel, in order to separate the impurities, 
 or the fragments of leaves which might pass over. The leaves 
 are washed with a little cold water, to detach the portions of 
 coloured skin which may adhere to them ; and this washing is 
 mixed with what had been drawn off. When this is done, lime 
 water is poured into the liquor of the fermented pastel, in the 
 proportion of two or three pounds for every ten pounds of 
 
 * Crell ; Neiieste Entdeckungen. A translation of it is to be found in the Biblioth^qiie 
 medico-physique du Nord, torn. iii. 
 
OF BLUE, 
 
 289 
 
 leaves, and the mixture is strongly agitated for some time, to 
 facilitate the separation of the indigo, which falls down on re- 
 pose. To ascertain if the agitation has been continued long 
 enough, a portion of the clear yellowish liquor is put into a 
 common bottle, on shaking which, it will be seen whether blue 
 be still separated, and in this case the liquor must be agitated 
 anewo When the whole of the indigo is finally separated and 
 deposited, the clear water is drawn off by a stopcock, placed at 
 some distance above the bottom of the tub, or by means of a 
 syphon, which ought to be done without loss of time. In order 
 to facilitate the separation of the water, the tub may be inclined 
 to the side of the stopcock, as soon as the stirring is over. The 
 blue colour which remains is poured into conical filters of linen 
 cloth, or into large filtering bags, {cJiausses d'Hippocrate^ 
 Hippocrates's sleeves. But as, at the beginning, a little colour 
 always passes over, it should be received in a vessel placed 
 beneath, and returned into the filter till the water comes off 
 clear. The indigo contained in the filters is edulcorated with a 
 sufficient quantity of water, and dried in the shade, or by a 
 gentle artificial heat, taking care to cover it up. 
 
 The indigo may be procured without the addition of the lime 
 water, but much less abundantly. If a larger quantity of lime 
 water be added, the amount of indigo is indeed greater, but it 
 is of inferior quality ; because the surplus of the calcareous earth 
 unites to the indigo. The alkaline salts, likewise, facilitate 
 this separation of the blue colour ; but it is not advantageous 
 to employ them, because they afterwards dissolve a portion of 
 it. With the addition of an acid, no precipitate takes place. 
 
 A certain time must elapse before it is proper to draw off the 
 water which has fermented with the pastel leaves. If it be run 
 off too soon, but little indigo is obtained ; if, on the contrary, 
 the leaves be left too long in infusion with the water, they enter 
 easily into putrefaction, diffusing a fetid and peculiar volatile 
 odour. Thenceforth no more precipitate can be separated, and 
 the water remains permanently green. The same thing happens 
 with the water drawn off, if it be neglected ; and, even when 
 the indigo is already separatad from the liquor, care should be 
 taken that this do not putrefy, otherwise the indigo will be 
 entirely, or at least partially spoiled. 
 
 We must not, however, be too hasty in turning the water 
 
 u 
 
290 
 
 BERTHOLLET ON DYEING. 
 
 into the vat in which it is to be agitated, on the first appear- 
 ance of the skin of changing blue, {peau hleue chatoyante,) since 
 it is at this moment that the water takes up most indigo. 
 
 When the degree of the atmospheric heat is considerable, the 
 fermentation is very speedily established, and fifteen or eighteen 
 hours may be sufficient. It is especially requisite, then, to be 
 very attentive, not to let it run into total putrefaction. If the 
 heat of the atmosphere be too low, neither much froth, nor 
 blue pellicle, is to be perceived, but the liquor inclines gradually 
 to putrefaction, without presenting any marked phenomena 
 before its commencement. 
 
 The plants piled up, or their juices, enter more rapidly into 
 fermentation, but they afford only a dirty blue. 
 
 The indigo extracted from the pastel must be dried in the 
 shade, because the sun destroys its colour. 
 
 D'Ambourney, who seems to have had no knowledge of the 
 preceding experiments, was also occupied with the means of 
 forming indigo from pastel.* He succeeded by letting the fresh 
 leaves of pastel ferment in a certain quantity of water ; he took 
 out the leaves, and poured solution of caustic alkali into the 
 liquor, after which he filtered it. A fecula remained on the 
 filter, which he compared to the indigo of Carolina. The fresh 
 and ripe leaves afforded l-70th of fecula. (Note HH.) 
 
 CHAPTER III. 
 
 Of Dyeing Blue with the Indigo and Pastel Vat. 
 
 Different processes are employed for dyeing blue by means 
 of indigo. We shall take a survey of these processes, without 
 entering into the details, which are well known in the dye-house, 
 and which are to be found described with much care in the 
 work of Hellot. 
 
 The preparation for dyeing blue is not made in boilers, as for 
 the other colours, but in large wooden vessels, to which the 
 name vats is given. The vats are let down into the ground,' so 
 as to rise above it only to a man's standing height. As it is 
 
 * Supplement au recueil des proc^d^s d'exp^riences, &c. 
 
OF BLUE. 
 
 291 
 
 important to maintain the heat of the vats, they are not put 
 in the same place with the boilers, for which a free circulation 
 of air is needed, but in an adjoining apartment, constructed in 
 a manner adapted to preserve the heat. The name of guesdres 
 is given to this arrangement, and the workmen are called guesdrons, 
 who should be skilled by long experience to prevent the acci- 
 dents to which the vats are liable. 
 
 Blue may be dyed with pastel or woad. A durable blue 
 would be made, but it would not be deep, and only a small 
 quantity of colour would be obtained, as has been said in treat- 
 ing of these substances. But by mixing them with indigo, vats 
 are formed, very rich in colour, which are almost the only ones 
 in use for wool and woollen stuffs. They are distinguished by the 
 name of pastel vats. 
 
 Hellot has not designated with precision the proportion of 
 the substances which are employed in the pastel vat. We shall 
 borrow from the memoir of Quatremere the description of a vat 
 of this kind. It is, however, to be remarked, that the quanti- 
 ties vary, not only in the different dye-houses, but also according 
 to the shades wished to be obtained. 
 
 For a vat which is nearly 8 feet in depth, and 5 feet in dia- 
 meter, two bales of pastel are thrown into the bottom, weighing 
 together 440 pounds, but they are previously broken down. 
 
 Thirty -three pounds of weld are to be boiled in a copper 
 for three hours, in a quantity of water sufficient to fill the 
 vat. When this decoction is made, 33 pounds of madder 
 are added to it, and a basket of bran. The mixture is boiled 
 for half an hour longer, and then refreshed (cooled) with 70 
 gallons of water. The bath is left to settle ; the weld is with- 
 drawn ; this bath is transferred into the vat ; and this is finally 
 stirred up with a rake during the whole period of the transva- 
 sion, and even a quarter of an hour longer. 
 
 All these operations being over, the vat is covered up very 
 warmly, and left six hours in this state, after which it is un- 
 covered, and raked during half an hour. The same thing is 
 repeated every three hours. 
 
 When blue veins are perceived on the surface of the vat, its 
 ground^ {pied,) as it is called, is given ; that is to say, 8 pounds 
 of quicklime. Whenever this substance is introduced, new 
 characters make their appearance. The colour of the vat be- 
 
 u 2 
 
292 
 
 BERTHOLLET ON DYEING. 
 
 comes of a blacker and deeper blue, and its exhalations grow 
 much more acrid. 
 
 Immediately after introducing the lime, or at the same time, 
 the indigo is put into the vat, after having ground it in a mill with 
 the smallest possible quantity of water. When it has been 
 diluted into the consistence of a thick pap, it is drawn off 
 through a stopcock placed at the lower part of the mill, and it 
 is thrown, without any other preparation, into the vat. The 
 quantity of indigo which must be put into a vat, is determined 
 by the shade to which the cloth or wool is to be brought. For 
 a vat composed in the above proportions, from 11 to 33 pounds 
 of indigo may be employed without inconvenience. 
 
 When, on striking the vat with the rake, a beautiful blue 
 froth called fleuree is obtained, nothing more is needed pre- 
 vious to dyeing, except to work with the rake twice in the space 
 of six hours, so as to mingle the materials perfectly. It is 
 sometimes necessary to add also a little lime. 
 
 The bath, when first poured on the pastel, was boiling hot ; 
 and care must be taken not to leave the vat exposed to the open 
 air longer than is necessary for raking. As soon as that opera- 
 tion is finished, the opening is closed by a large wooden lid, on 
 which thick coverings are spread ; and every method is had 
 recourse to for keeping up the heat of the vat without the in- 
 tervention of fire. But notwithstanding these precautions, 
 however favoured by the arrangement of the guesdres, the heat 
 can be kept up for only a certain time. At the end of eight or 
 ten days it is found to be much reduced, and would be entirely 
 dissipated if the liquor were not heated again. 
 
 This operation consists in transferring the greater part of the 
 vat bath into the boiler, under which a strong fire is kindled. 
 When this bath has received a sufficient heat, it is turned back 
 into the vat in the same manner, and again covered with care. 
 
 The pastel vat is liable chiefly to two accidents : the first 
 occurs when it gets stiff* or thrown back, according to the lan- 
 guage of the vat-men. This accident is perceived, when, on 
 uncovering a vat which had already afforded fine blue shades, it 
 is found to be black, without any appearance of blue veins, and 
 without fleuree, {froth.) If it be raked up, only a black colour^ 
 more or less deep, is remarked : and the odour of the bath, instead 
 of having in it something sweetish, as when the vat is in good 
 
OF BLUE. 
 
 293 
 
 condition, affects the nose, on the contrary, in a very pungent 
 manner. If dyeing be attempted in a vat exhibiting these charac- 
 ters, the stuff takes no colour, or only a dirty grey. These bad 
 qualities depend on an excess of lime ; and Quatremere states, 
 that he has communicated them to a vat by overdosing it with 
 lime. 
 
 The vat-men employ different means to restore a repelled vat. 
 Some put tartar into it, others bran, urine, madder; and others 
 content themselves with re-heating it. According to Hellot, the 
 best remedy is to put into it bran and madder at discretion ; 
 and if it be only a little too much dosed with lime, it is suffi- 
 cient to let it rest five or six hours at farthest, putting into it 
 only a certain quantity of bran, and three or four pounds of 
 madder, which are diffused through the vat. If it be thrown 
 back to the degree of affording blue, only when it is cold, it 
 must be allowed to recover without disturbing it, and sometimes 
 be left whole days without being stirred with a rake. When it 
 begins to make a tolerable pattern, the bath must be re-heated, 
 in which case the fermentation usually revives. It may be ex- 
 cited with bran and madder, and even with a basket or two of 
 fresh pastel. 
 
 Hecquet d'Orval and Ribacourt advise to rest satisfied with- 
 out raking up, if the bath be but slightly thrown back ; but if 
 the evil has made more progress, to put into it some pounds of 
 bran enclosed in a bag, and to diffuse through it at the same 
 time three or four pounds of tartar in powder. The bag, after 
 five or six hours, begins to float and is withdrawn, and the rake 
 is used. If the vat be not yet restored, the same operation 
 is repeated. 
 
 Quatremere says, that he has re-established a vat which he 
 had thrown back by an excess of lime ; and that for this effect 
 he contented himself with heating twice, and leaving it then 
 in repose for two days, after which it afforded a well character- 
 ized Jleuree, He left it again in repose for three days ; and 
 lastly, heating it for the third time, he found it to*be restored. 
 
 The second accident to which the pastel vat is subject, is 
 putrefaction. When this accident occurs, the veins and the 
 fleuree disappear, its colour becomes russet, (rousse,) the paste 
 which is at the bottom rises up, the smell becomes fetid. 
 
 Quatremere asserts, that if a pattern of a dark blue be 
 
294 
 
 BERTHOLLET ON DYEING. 
 
 plunged into a vat thus deteriorated, its colour becomes several 
 shades lighter. Putrefaction takes place in a vat, because it has 
 not been sufficiently furnished with lime. Whenever the marks 
 of putrefaction appear, we must hasten to correct it, by adding 
 lime and raking up. This operation is reiterated till the vat be 
 restored ; but we must beware of passing to the opposite excess. 
 
 It appears, that a just distribution of lime is the object which 
 demands most attention in the conduct of a pastel vat. It mo- 
 derates the fermentation of the pastel, and of the other sub- 
 stances that serve to de-oxydise the indigo ; for this effect, 
 pushed too far, destroys the colouring particles. But too strong an 
 action of the lime becomes too great an obstacle. It is therefore 
 proper to wait till the excess of lime disappears, undoubtedly 
 by the successive formation of carbonic acid, or the source of the 
 fermentation must be increased, or a portion of the lime be satu- 
 rated by a vegetable acid. Another use of the lime is to hold in 
 solution the colouring particles of indigo and of the pastel, which 
 are de-oxydised. Woad is employed as well as pastel, but it 
 appears that the preliminary preparation which both are sub- 
 jected to, is not essential. We have seen a skilful dyer of Rouen 
 employ for his vat the plant of woad simply dried ; and assert 
 that he derived more advantage from it than from ordinary woad. 
 
 The vat is raked up two hours before dyeing ; and to prevent 
 the sediment which settles at the bottom, and which is called 
 paste, from producing inequalities in the colour, there is intro- 
 duced into the vat a species of trellis (lattice work) formed of 
 thick ropes, which is called champagne ; and when wool is to be 
 dyed in the fleece, there is even placed over the lattice a net 
 with close meshes. The wools or stuffs are to be well moistened 
 in clear water somewhat hot ; they are to be squeezed and then 
 plunged into the vat, where they are moved about longer or 
 shorter, according as a colour of greater or less depth is wanted, 
 airing them from time to time. The green colour which the 
 bath communicates, changes into blue by the action of the air. 
 It is difficult to give an equable light blue tone in a rich bath. 
 The best method of obtaining these shades, is to use vats which 
 are already exhausted and l3eginning to cool. 
 
 Wools and stuffs dyed blue ought to be washed with much 
 care, to carry off the particles that are not fixed on the wool ; 
 and even the stuffs which are of a somewhat deep blue ought to 
 
OF BLUE. 
 
 295 
 
 be cleansed carefully at the fulling-mill, with a little soap, which 
 does not affect the colour. Those intended to be dyed black 
 must be treated in the same way; but this operation is less 
 necessary for such as are to be turned green. 
 
 The name of indigo vat ( cuve d'lnde ) is given to the vat 
 into which no pastel or woad enters. The vessel which serves 
 for this operation* is a boiler, which, by its conical form, leaves 
 between it and the masonry which surrounds it, and on which 
 its brim rests, a sufficient vacuity for introducing a fire. Into 
 this copper are poured 140 gallons of water, more or less, accord- 
 ing to its capacity. In this are dissolved 6^ pounds of cendres 
 gravelees, (alkaline ashes of the vine,) as much bran, and 13 
 ounces of madder, which are all made to boil. Into the vats, 
 even the sediments of these materials are put. There is now 
 poured in 6J pounds of indigo ground with water. Careful rak- 
 ing follows. The vat is shut up ; a slow fire is placed round it ; 
 a second raking is given 12 hours after it is mounted, and thus 
 in succession, from \2 hours to 12 hours, till it has come to blue, 
 which will take place at the end of 48 hours. If well managed, 
 the bath will be of a fine green, covered with coppery flakes and 
 scum, or blue fleuree. 
 
 This vat is much easier to conduct than that of pastel ; but as 
 its whole blue is derived from indigo, it is dearer. The alkali 
 which serves as solvent being more soluble than lime, the dyeing 
 bath is much richer in colour; lastly, the cloths retain more 
 softness in it, than in the pastel vat, where lime is the solvent. 
 When the above vat is in the suitable state, it is employed for 
 dyeing in the manner which has been indicated for the pastel 
 one. 
 
 Hellot describes two vats in which indigo is dissolved by means 
 of urine. Madder is added, and to one, vinegar, and to the 
 other tartar and alum, each equal in weight to the indigo. The 
 quantity of urine should be considerable. The solution of in- 
 digo, deprived of its oxygen by urine and madder in fermenta- 
 tion, is due to the ammonia formed in the urine, either by the 
 action of heat or fermentation. Hellot remarks, that an effer- 
 vescence occurs when the solution of alum and tartar are poured 
 in, substances which serve probably to hinder the progress of 
 
 * Memoire sur riiidigo, par Hecquet trOrval et Ribacoiut. 
 
296 
 
 BERTHOLLET ON DYEING, 
 
 putrefaction. But these vats are not comparable to the vat of 
 pastel and the vat of indigo, by means of which much more 
 work is dispatched ; they can only answer in small dyehouses. 
 
 For dyeing silk blue, the indigo vat above described is em- 
 ployed. More indigo is usually put in than the dose which has 
 been indicated; but the proportions of bran and madder are 
 nearly the same. Macquer states,* that if a weight of madder 
 equal to one-fourth of the cendres gravelees be introduced, the 
 vat becomes green, and its colour is surer on silk, without having 
 a less agreeable cast. The pastel vat and the others spoken of 
 are not fit for dyeing silk, because they do not colour with 
 sufficient promptitude. 
 
 When the vat is in working condition, there is given it what 
 is called a brevet, with about two pounds of cendres gravelees^ 
 and four ounces of madder. It is raked up ; and after four 
 hours it may serve for dyeing. The heat should be then sufi[i- 
 ciently reduced^ so that the hand may be held in it without 
 pain. 
 
 The silk, previously boiled with soap in the proportion of 30 
 per cent, of its weight, and then well cleared of its soap by two 
 beetlings, or even more, in running water, is plunged into the 
 vat. As it is very liable to take the colour unevenly, it must be 
 dyed in small portions. The workman, therefore, immerses the 
 hanks, one after another, passing them round a cylinder of wood; 
 and when he has turned them several times in the bath, he 
 wrings them forcibly over the bath, and airs them to make the 
 green become blue. When they appear perfectly ungreened, he 
 throws them into pure water, and then wrings them several 
 times with the espart, (pin.) 
 
 We must take care that the silk just dyed should be very 
 speedily dried. During winter and damp weather, it is dried in 
 a chamber heated by a stove, exposing it on a kind of frame 
 which is kept in constant agitation. 
 
 When the bath grows weak, and its green colour diminishes, 
 a brevet is given it, into which there enter one pound of cendres 
 gravelees, a little madder, and a handful of well washed bran. 
 When the indigo is found to be exhausted, more of it must also 
 be restored to the bath, along with the due proportions of cen- 
 dre gravelee, madder, and bran. 
 
 * Art de la teinture en soie. 
 
OF BLUE. 
 
 297 
 
 Some dyers turn to advantage the weakened vats for dyeing 
 light shades ; but the blue obtained in this case is less beautiful 
 and less permanent, than if for these shades fresh vats were 
 used, into which a smaller quantity of indigo entered. 
 
 Indigo alone cannot give a deep blue to silk. For this pur- 
 pose it is necessary to prepare it, by giving it another colour or 
 ground. For turkey-blue, which is the deepest, a very strong 
 bath of archil is first given, and one a little weaker for king's 
 blue. It is then turned through a fresh and well furnished vat. 
 The other blues are made without any ground. 
 
 A blue as deep as king's blue is also made, for the ground of 
 which cochineal is used instead of archil, with the view of giving 
 it more solidity, which occasions it to be called fine blue. 
 
 By means of verdigris and logwood, a blue which possesses 
 very little solidity is given to silk. But its durability may be much 
 increased, by giving it first of all, by this means, a lighter shade 
 than what is wished for, next passing it through the archil bath^ 
 and finally through the vat. 
 
 To dye raw silks blue, such must be chosen as are naturally 
 white; they must be well soaked in water, and then turned 
 through the vats in separate hanks, like the scoured silks. Raw 
 silks take the dye generally with more facility and activity than 
 those which have been boiled. The boiled should, if possible, 
 be passed through the vat before the raw. If raw silk require 
 archil, or the other ingredients above mentioned, it is to be 
 treated like the boiled silks. 
 
 According to Le Pileur d'Apligny, the vat for dyeing linen 
 and cotton is a cask capable of holding nearly 109 gallons. The 
 quantity of indigo employed is usually from 6 J to 8 J pounds. 
 This indigo, after being ground, is boiled in a ley, run off clear 
 from double its weight of potash, and lime equal to the weight 
 of the indigo. The boiling is continued till the indigo is well 
 penetrated with the ley, stirring the mixture with care, and 
 taking pains to prevent the indigo from sticking to the bottom, 
 and burning. 
 
 During the boiling of the indigo, an equal weight of quick- 
 lime is to be slaked ; to this about four gallons of hot water are 
 added, and sulphate of iron is dissolved in it to the amount of 
 double the lime. When the solution is finished, the liquor is 
 poured into the vat, which should be previously half filled, or 
 
298 
 
 BERTHOLLET ON DYEING. 
 
 nearly so, with water. There is afterwards poured over it the 
 solution of the indigo, and the remainder of the ley which had 
 not been employed in the boiling is added. When the whole 
 has been poured into the vat, it must be filled up with water, 
 to within two or three finger-breadths of the edge. It is stirred 
 vdtli the rake two or three times a-day, till it be in a condition 
 for dyeing, which takes place at the end of 48 hours, often 
 sooner, according to the warmth of the air, which accelerates, 
 more or less, the formation of this vat. 
 
 Some persons add to a vat, composed nearly like the preced- 
 ing, a little bran, madder, and pastel.* 
 
 At Rouen another process is followed, which Quatremere 
 has described. The vats are constructed of a species of gun 
 flint ; the inside and outside are covered with a kind of coating, 
 made with a fine cement. A certain number of these are placed 
 in one dyehouse, arranged in one or several parallel lines. 
 
 A vat may contain four hogsheads of water, and there may 
 be put into it from 20 to 22 pounds of indigo, previously ma- 
 cerated, during eight days, in a caustic ley, strong enough to 
 float an egg. This indigo is then ground in a mill, in which, 
 indeed, the maceration frequently takes place. The vat is then 
 flUed, with the exception of a small space, and 22 pounds of 
 lime are introduced into it. When it is well slaked, the vat is 
 raked, and 40 poimds of sulphate of iron are put in. When- 
 ever the solution is completed, the mill-ground indigo is poured 
 in through a sieve. The vat is raked seven or eight times the 
 same day ; and, after a repose of 36 hours, it may be used for 
 dyeing. 
 
 There must be vats established at different periods. They 
 begin by passing the cotton or yarn through the most exhausted 
 vat, and they continue thereafter to proceed from vat to vat 
 till they come to the strongest, unless before reaching it the 
 wished-for hue is obtained. The cotton or yarn must be wetted 
 before entering the first vat. It should not be left more than 
 five or six minutes in the bath, because it takes up in this time 
 nearly the whole blue with which it can charge itself. 
 
 When the dyeing in one vat is over, it must be raked up, 
 and no longer worked upon, till it settle at least 24 hours. If 
 it is recently set, however, it does not need to stand so long. 
 
 * Proems- verbal dcs operations do teirit faitcs a Yvctot par Francois Goniu. 
 
OF BLUE. 
 
 299 
 
 When a vat has been dyed with three or four times, it begins 
 to be altered. When raked, no more blue veins are perceived 
 at its surface, where it becomes black. In this case, it must 
 be replenished, for which purpose, 4J pounds of sulphate of 
 iron, and two of quicklime, are added, and it is twice raked. 
 The vat may be replenished three or four times, diminishing 
 its ingredients in proportion as it declines in strength and 
 quality. 
 
 In the vats just mentioned, it is the potash and lime which 
 give solubility to the indigo deoxydized by the action of the 
 precipitated iron. It may be thence inferred, that the sulphate 
 of iron employed should be little oxydized, for in a state of 
 high oxydation it produces no effect. 
 
 Lime may be used alone for precipitating the sulphate of iron, 
 and dissolving the indigo. In this case, the solution of indigo 
 is less concentrated, and we cannot succeed, or at least we 
 cannot succeed so quickly, in giving to cotton or thread so in- 
 tense a blue by means of that vat, as by the preceding. But 
 this circumstance is even frequently of advantage. Some 
 persons increase the concentration of this vat, by adding to it 
 a little orpiment and potash. 
 
 Bergmann and Haussman have given particular descriptions 
 of this vat, with proportions a little different. The latter re- 
 marks on this occasion, that the sulphate of iron must not con- 
 tain copper, for the oxyde of copper restores the indigo, which 
 it is our interest to keep in a state of deoxydation till it be 
 combined with the stuff. This observation is applicable to all 
 the cases in which sulphate of iron is used along with indigo. 
 He further remarks, that cotton cloth passed through water 
 acidulated with sulphuric acid, on its quitting this vat, assumes 
 a finer blue than if it be merely washed in the river, or set 
 to dry. 
 
 We shall now point out a vat of this kind, the good consti- 
 tution of which is confirmed by experience ; as also the differ- 
 ent uses that may be made of it. 
 
 The proportions employed for this vat are one part of indigo, 
 two of sulphate of iron, and two of lime. After raking it for 
 several hours in succession, when we set it, it is allowed to 
 settle two days ; we then dye with it. 
 
 Before dyeing, the froth is removed ; and every evening, 
 
300 
 
 BERTHOLLET ON DYEING. 
 
 after the day's work is over, the replenishment is given to the 
 vat, by putting into it some liquor [bouillon) from a little vat 
 prepared for this purpose, v^ith a much smaller proportion of 
 v^ater than there is in the dyeing vat, to which the froth of the 
 latter is added. It is raked, covered up, and left at rest till 
 the work be resumed. When the vat is weakened, a little 
 power is communicated to it by the addition of some lime, and 
 sulphate of iron. 
 
 For the dyeing of cloths, they must be stretched upon frames, 
 fixing their selvages to little hooks (pins) with which the cross- 
 bars of the frames are provided. By means of a rope, running 
 over a pulley, the frame is dipped into the vat. A slight agita- 
 tion is given to it for a little while, to moisten the cloth more 
 equably ; the frame being so suspended that the whole breadth 
 of the piece may be in the vat, without allowing the bottom of 
 the frame to touch the sediment. After letting it become blue, 
 (in the air,) it is washed with care, especially if preserves (resist 
 pastes) be printed upon it, In order to dye two blues along 
 with white, (spots,) the reserve is impressed, which should cover 
 the white and the pale blue. It is dyed, washed, and the reserve 
 is a second time applied to the places which are to remain white : 
 such as have been reserved at the first dyeing, not being so at 
 the second, take a lighter hue than the ground of the cloth. 
 When the reserved places are to be dyed after the blue dye, the 
 mordant is mixed with the reserve. 
 
 The property which the oxyde of copper possesses of giving 
 up its oxygen to indigo, and thereby depriving it of its power 
 of fixing on stuffs, is made use of for reserves. 
 
 The reserves are usually composed of verdigris, pipe-clay, and 
 several substances, which vary in different receipts. The verdi- 
 gris is the only active one : the pipe-clay kept in suspension by 
 the mucilage, which serves to thicken the reserves, may have 
 the advantage of lessening the quantity of mucilage necessary 
 for the thickening, and rendering the reserve more easy of appli- 
 cation. To the verdigris, sulphate of copper is usually joined, 
 and sulphuric acid is added, undoubtedly with the view of 
 rendering this salt more soluble. The composition of a good 
 reserve resolves itself into the employment of the most soluble 
 solution of copper ; 1. For applying more oxyde to the stuff; 
 and 2. That its crystallization may not make it difficult to print 
 
OF BLUE. 
 
 301 
 
 on. For very deep blues, however, which require a long 
 continuance of the cloths in the vat, some substance must be 
 added to the reserve that may prevent it from dissolving in the 
 vats. With this view, tallow or wax is intermixed, while the 
 reserve is heating so as to thicken it. The compositions formerly 
 used for reserves, owed much of their effect to the wax. It was 
 kept in solution, (fusion ?) in order to be applied on the cloth, 
 where it formed a kind of varnish that was removed by hot 
 water after the dyeing. 
 
 If it be wished to give cloth blue figures on a white ground, 
 a style of work called China blue, or English blue, this process 
 is divided into different stages. The ground indigo, mixed with 
 sulphate of iron, is printed on the cloth, which is stretched on 
 a frame similar to that above described, and passed through a 
 vat containing lime. Here it remains for some time. It is 
 then plunged into a vat which contains a solution of sulphate 
 of iron, marking from 3^° to 4° of the areometer of Baume, 
 1.025 sp. gravity. It is now returned into the quicklime vat, 
 passing thus alternately four times from one of these vats to the 
 other. When it quits for the fourth time the vat of sulphate of 
 iron, it is plunged into a vat containing a feeble alkaline solu- 
 tion, in which it remains an hour, and lastly, into a fourth vat 
 holding sulphuric acid diluted with water. 
 
 What occurs in a vat, takes place here on those parts of the 
 cloth to which the indigo and sulphate of iron has been applied. 
 The sulphuric acid dissolves away the oxyde of iron with which 
 the cloth is covered. To remove it completely, the cloth must 
 be turned through this acid kept hot in a leaden boiler. 
 
 To have patterns in china blue, bearing different shades, it is 
 sufficient to put into the colour printed on, different quantities 
 of indigo. 
 
 Befgmann describes another vat, very convenient and expe- 
 ditious, for thread (yarn) and cotton, which is described also 
 by Scheffer.* A very strong solution of alkali is taken; 186 
 grains of well-ground indigo are added to it for every 1| pints 
 of liquid. After some minutes, when the indigo is thoroughly 
 penetrated with it, 372 grains of powdered orpiment are put 
 into the liquor, the bath must be well raked, when, in a few 
 
 * Essai Bur Tart de la teinture. 
 
302 
 
 BERTHOLLET ON DYEING. 
 
 minutes, it becomes green, forms a blue froth, and shows a 
 pellicle. The fire should now be extinguished, and the dyeing 
 may be commenced. 
 
 This vat does not differ from the preparation applied to cotton 
 cloths, which is called pencil-blue, except in the proportions of 
 orpiment, and especially of indigo, which are much larger than 
 in the latter. For this preparation there is employed, according 
 to Haussman, for 220 pounds of water, 33 of potash, 13 of 
 quicklime, as much orpiment, and 17 J of indigo. Oberkampf, 
 the whole of whose processes have been improved with so much 
 care, employs a still greater portion of indigo. In the process 
 of Bergmann, the indigo constitutes nearly the 24th part of the 
 water; still less in that of Scheffer ; l-12th in that of Hauss- 
 man, and l-9th in that of Oberkampf. The proportions of the 
 other ingredients vary in these different processes. It would 
 seem, that these preparations may succeed within a scale very 
 extensive as to the proportions ; nor would it be easy to deter- 
 mine what are the most advantageous ones for the object pro- 
 posed. 
 
 Three processes are employed for giving blue in the art of 
 calico-printing. 
 
 The first of these processes is used for dyeing cloth whose 
 ground is to be blue or green ; and whenever they bear colours 
 which are to be kept from varying in the vat, these are covered 
 with the white reserve. 
 
 If the cloth is to retain a white ground, and bear blue figures, 
 of one shade or of several, the second of these processes is had 
 recourse to. Sometimes one or two colours are joined to the 
 blue thus made ; but in this case, they must be applied after 
 the blue dyeing, because there is not a colour which may not be 
 either destroyed, or powerfully altered, in the operations which 
 it requires. 
 
 Lastly, in other circumstances, a blue is to be put on cloth 
 covered with a pattern, all of whose parts are already coloured, 
 and which leaves merely small spaces to colour blue. For this 
 purpose, the blue is used which is applied with the pencil. 
 
 This blue of application is thickened with gum, and put upon 
 the pencil. It may be printed on, by covering with canvass the 
 frame which contains the thickened colour, and removing the 
 regenerated indigo with a^scraper before applying the plate ; but 
 
OF BLUE. 
 
 303 
 
 only small objects of a slightly intense blue, which rarely suc- 
 ceeds, can be thus applied. 
 
 Bancroft says, that he has substituted sugar for the sulphuret 
 of arsenic with success ; which would be advantageous, on 
 account of the price and poisonous qualities of this substance. 
 The experiment did not succeed with us. 
 
 The blue of application has been attempted to be prepared 
 by means of the oxyde of tin ; but the degree 'of concentration 
 of the alkaline solution adequate to the solution of the oxyde 
 and the indigo has not been hitherto ascertained, so as to be 
 susceptible of thickening with the gums. This point once 
 determined, a pencil blue will be had, which will possess the 
 very great advantage of not occasioning a bulky deposite, which 
 always embarrasses the vessels where this blue is made in the 
 ordinary processes, and which, however well washed, causes a 
 considerable waste of the indigo. 
 
 In printing on cloth, ground indigo with oxyde of tin, and 
 passing the cloth through a solution of oxyde of tin in potash, 
 china blues may be made in a single vat. We have been able 
 to make in this way only light blues. Were this process brought 
 to the point of producing more substantial blues, it would afford 
 great advantages. 
 
 CHAPTER IV. 
 
 Of Saxon Blue. 
 
 The name of Saxon blue is given to the dye for which solu- 
 tion of indigo in sulphuric acid is employed, because it was 
 discovered at Grossenhayn, in Saxony, by Counsellor Barthe, 
 about the year 1740. This discovery was kept secret for some 
 time, but it gradually spread abroad. At first the solution was 
 not made with indigo alone, but alumina and antimony were 
 added, and other mineral substances besides, which were previ- 
 ously digested with the sulphuric acid. Indigo was afterwards 
 added, and when the solution was complete, it was used for 
 dyeing. 
 
 Bergmann performed many experiments on this solution of 
 
304 
 
 BERTHOLLET ON PYEING. 
 
 indigo, which have thrown a great light, not only on its proper- 
 ties, but also on the general cause of the fixation of the colour- 
 ing particles on stuffs. 
 
 He employs, as has been stated before, one part of indigo well 
 pulverized with eight parts of sulphuric or vitriolic acid, so con- 
 centrated that its specific gravity is to that of distilled water as 
 1.90 to 1.00. The mixture being made in a glass bottle, loosely 
 stopped, a great heat is excited. After a digestion of 24 hours, 
 at a temperature of 77° or 100"^ Fahr., the indigo is dissolved, 
 but the mixture is entirely black and opaque. On adding water 
 it grows clear, and yields successively every shade of blue, 
 according to the quantity of water. In a great number of ex- 
 periments which this illustrious chemist describes, he kept in 
 boiling water for 24 hours the stuff intended to be dyed : he then 
 put a determinate weight of it into a bath of greater or less 
 strength, till the bath was deprived of colour. It follows from 
 his experiments, 1. That one part of indigo by this process can 
 produce a black blue on 260 parts of stuff, which seems to be 
 then saturated, for it could take no more indigo in a permanent 
 manner. 2. That the cold bath acts as well as the hot. 3. 
 That the operation may be made without waste of indigo, for 
 the bath can be entirely blanched, and if it has been too much 
 charged, unsaturated stuff may be added, which absorbs all ^the 
 remaining colour. 4. That the bath saturated with salt of soda 
 (crystallized carbonate) yields only a very pale colour : and with 
 the sulphate of soda it gives a bright blue, but much less feeble, 
 so that these salts unite more or less with this dye. 
 
 Similar experiments have been made on silk, which had, in like 
 manner, been soaked in hot water, and which had been with- 
 drawn from the bath after 144 hours. The indigo dye forms a 
 blue on silk as on (w^oollen) stuff; but the affinity which precipi- 
 tates the blue molecules is weaker. Although the patterns of 
 silk resist water alone very well, they cannot bear the action of 
 soap. 
 
 Threads and cotton took but very pale shades with this dye. 
 
 The deepest shades obtained by this process with the employ- 
 ment of concentrated sulphuric acid are not liable to change, 
 according to the statement of Bergmann. He says, that having 
 exposed to the sun all the patterns during two months, the Per- 
 sian and Turkey blues (Coventry blues) were scarcely impaired ; 
 
OF BLUE, 
 
 305 
 
 but that the light shades suffered much more, growing dead and 
 greenish, 
 
 Quatremere says, that among several dye-houses, he was 
 acquainted with only two where the method of making the in- 
 digo dye, by sulphuric acid, penetrate into the interior of the 
 stuff, or what is called pierce or cut, {percer ou trancker,) 
 was understood ; and that he gave it this property by introduc- 
 ing fixed alkali into it, in the proportion of one part to one of 
 indigo, with six of sulphuric acid. He has dyed with this pre- 
 paration a sample of blue of the liveliest and deepest shade, and 
 the section was as dark as the surface. 
 
 Poerner, who was much occupied with this preparation, re- 
 commends likewise the addition of alkali.* He says, that by 
 this means the colours are more agreeable, and penetrate deeper. 
 He further prescribes to take only four parts of sulphuric acid 
 to one of indigo. In the process which he describes, four parts 
 of concentrated sulphuric acid are poured on one part of indigo 
 reduced to a fine powder. This mixture is stirred for some time, 
 and then left at rest for twenty-four hours. One part of good 
 dry potash in fine powder is now added to it. The whole is 
 well mixed, and left at rest for twenty-four hours, after which a 
 greater or less quantity of water is added to it. 
 
 The same author announces, that he has found a preparation 
 of indigo in a dry form, which is more advantageous, and of 
 more easy and convenient use than the preceding, but that he 
 cannot communicate it yet to the public. 
 
 Bancroft adopts the proportion of sulphuric acid and indigo, 
 as also the addition of alkali, recommended by Poerner. He 
 says, that the sulphuric acid may be even diluted to a certain 
 degree. He remarks, that the indigo of Guatimala is fitter for 
 this solution than the others, ascribing this peculiarity to its 
 being more oxydized, because lime water was probably not em- 
 ployed in its preparation ; on which account it was necessary to 
 subject it to longer beating to effect its precipitation. The dif- 
 ference presented in this respect by Guatimala might, however, 
 be owing only to its affording less yellow extractive matter, and 
 to its molecules offering in their cohesion less resistance to the 
 sulphuric acid. 
 
 * Instruction siir Tart de la teinture, 
 X 
 
306 
 
 BERTHOLLET ON DYEING. 
 
 Bancroft states, that by precipitating the solution of indigo 
 with carbonate of lime a blue precipitate may be had, which can 
 serve for dyeing directly. This might possibly be the pre- 
 paration announced by Poerner. 
 
 Bergmann conceived, that the Saxon blue owed its little per- 
 manence merely to the too feeble concentration of the acid 
 which he employed for dissolving it. But his trials must have 
 led him into a mistake in this respect. 
 
 For regulating the preparation and employment of solution 
 of indigo, what we have formerly laid down must be borne in 
 mind. 
 
 The indigo suffers in this solution an alteration which cannot 
 be avoided ; but it should be so managed as to make it as small 
 as possible. Consequently the heat should be tempered as 
 nicely as may be, as well as the concentration and quantity of 
 the sulphuric acid. When the solution is made, it is proper to 
 dilute it with water, in order to preserve it, and to prevent the 
 degradation making progress. 
 
 A small quantity of alkali may have good effects, but a greater 
 would be injurious, since the alkali possesses the property of 
 dissolving the blue molecules precipitated from the sulphuric 
 acid. Thus, as Haussman observes, soap and alkalies render 
 stuffs dyed in Saxon blue yellow, and water alone is sufficient 
 to separate the colouring particles fixed on cotton. 
 
 In the process commonly made use of for dyeing Saxon blue, 
 the cloth is prepared with alum and tartar. A smaller or greater 
 proportion of the indigo solution is put into the bath, according 
 to the lightness or depth of the shade wished to be obtained. 
 The name composition is given in the workshops to this solu- 
 tion, and occasionally that of hleu de Prusse^ or Saxon blue. 
 The clear shades may be made in the sequel of the deep shades, 
 but they have more lustre when made in a fresh bath. For the 
 deep shades, it is advantageous to pour in the solution of indigo 
 by portions, lifting up the cloth on the reel. 
 
 Other details will be given on this dye, and particularly on 
 the English blue, which is a modification of it, when treating of 
 green in the Sixth Section. 
 
OF BLUE. 
 
 307 
 
 CHAPTER V. 
 
 Of Dyeing Blue by means of the Prussiate of Iron. 
 
 As the prussiate of iron, or prussian blue, furnishes a beauti- 
 ful and permanent colour to painting, attempts have been made 
 to extend its use to dyeing. It was Macquer who sought to 
 render this substance useful to the art, after giving important 
 observations on its nature. 
 
 The chemical properties of the principle which forms prussian 
 blue with the oxyde of iron, occasion very varied combinations 
 and phenomena, of which we shall give merely such an idea as 
 may be proper for regulating the operations in which it is em- 
 ployed. 
 
 This principle is derived from a combination which is formed 
 when any charcoal containing azote, as that of animal sub- 
 stances, is calcined along with alkali, and then moistened. The 
 water is decomposed ; its hydrogen, on the one hand, forms 
 ammonia with the azote, and, on the other, forms the co- 
 louring principle of prussian blue with azote and carbon, whilst 
 its oxygen produces carbonic acid. If the charcoal has been 
 exposed to too strong a heat, it is deprived of its azote, as Gay 
 Lussac observed, and then it can no more produce either am- 
 monia, or the colouring principle of prussian blue. 
 
 The name of acid is given to this colouring principle. It has 
 not, however, of itself this property, but acquires it by com- 
 bining with a metallic oxyde, particularly the oxyde of iron ; 
 for it then saturates the alkaline properties. As it is in this 
 state that it exists in the alkaline prussiates, we shall call it by 
 this name, without regard to its complex composition. 
 
 Whenever an alkali is made to act on the prussiate of iron, 
 the prussic acid, which retains some oxyde of iron, saturates 
 the alkali, and thus the prussiates of alkali are obtained. The 
 oxyde of iron meanwhile retains a certain proportion of prussic 
 acid. This latter compound has a yellow colour. In this state 
 an acid makes a partition o/ the oxyde of iron, till the yellow 
 prussiate be brought to the state of blue prussiate. At this 
 term the acids can no farther destroy the combination, unless 
 heat be employed. 
 
 The acids cannot all equally decompose the prussiates of 
 
 x 2 
 
308 
 
 BERTHOLLET ON DYEING. 
 
 alkali without an elevation of temperature, or without the agency 
 of %ht. In this case a portion of the prussic acid assumes the 
 elastic state, and volatilizes, whilst another falls down with the 
 oxyde in blue prussiate. 
 
 If a solution of iron be mixed with a prussiate of alkali, the 
 oxyde combines with the prussic acid, and precipitates ; but it 
 retains a portion of the alkali in its composition, so that the 
 prussiate of alkali and prussiate of iron must be considered, 
 both the one and the other, as triple combinations. In the one 
 it is the oxyde which predominates ; in the other it is the alkaK. 
 Let us examine the methods by which we can fix this first com- 
 bination upon stuffs. 
 
 Macquer's first attempt was to soak cotton yarn, wool, and 
 silk, in a solution of alum and sulphate of iron ; next in an 
 alkaline solution, which was in part saturated with prussic acid ; 
 then in water soured with sulphuric acid, so as to dissolve the 
 portion of the oxyde of iron combined with the prussic acid, 
 which had been precipitated by the alkali uncombined with this 
 acid. He repeated the immersions successively, and obtained a 
 fine blue, but very unequable. Wool and silk became rough 
 to the touch, by the action of the alkali, as well as by that of 
 the sulphuric acid. 
 
 It is easy to see that this process ought not to have been 
 successful ; for as an alkali not saturated with prussic acid was 
 used in a second immersion, the portion of unsaturated alkali 
 must have dissolved more or less of the blue fixed in the 
 first. If these experiments were therefore to be resumed, it 
 would be requisite to employ an alkali saturated with prussic 
 acid or lime water, and particularly magnesia, which have like- 
 wise the property of combining with this acid. 
 
 In a second process this able chemist boiled his patterns in 
 a solution of alum and tartar, and turned them afterwards 
 through a bath, in which he had mechanically diffused prussian 
 blue. They were now died evenly, and were soft to the touch, 
 but the shade was faint ; nor was it possible to make it deeper. 
 
 Menon proposed another process for thread and cotton. It 
 consists in dyeing the stuff" at first black, and then letting it 
 steep some minutes in a solution of prussiate of alkali. It is 
 thereafter boiled in a solution of alum, where it takes a very 
 deep blue. A blue combination is formed, and the alum dis- 
 
OF BLUE. 
 
 309 
 
 solves the remaining black particles ; but the effect must be 
 very irregular, according to circumstances. 
 
 Several attempts have been made to derive advantage from 
 these experiments, and especially from the first method; but 
 whatever pains may have been taken, the colour v^as alv^ays 
 faint, dull, and unevenly. This was given up in favour of a 
 process which has a considerable relation to the second one of 
 Macquer. The prussian blue is merely diffused in muriatic acid, 
 which does not make a true solution, but attenuates it enough, 
 by its affinity, to cause it to penetrate cotton goods more copi- 
 ously. We shall now literally transcribe the description given 
 of it by Roland de la Platiere,* which agrees with the practice 
 of certain dyers. 
 
 On fine prussian blue powdered, passed through a very close 
 sieve, and put into an earthenware vessel, in an indeterminate 
 quantity, but in the proportion of half a kilogramme (about a 
 pound) for every piece of goods, pour muriatic acid till the 
 materials assume the consistence of syrup ; stir continually while 
 it is in fermentation (chemical action) for about half an hour ; 
 dilute well, and stir again from hour to hour, during a day, till 
 finally no more fermentation is perceived. Thus the division of 
 the particles will be very great, and their union with the acid 
 intimate. 
 
 Into a trough narrower than the ordinary ones, and more 
 .widened out above, two feet and a half high, two feet in dia- 
 meter at the bottom, and two feet and a half at the top, put from 
 seven to eight gallons of water for one piece of velvet ; add to it 
 some of the composition, previously well diluted with water in 
 a separate vessel. Pour this into the bath through a very fine 
 sieve ; and as soon as the piece is arranged on the winch placed 
 over the trough, rake the bath well, and let down the velvet 
 quickly, working with the utmost possible activity, for one, two, 
 or three hours, passing the piece in succession from the winch to 
 the horse or board, f planche,) and from the board to the winch. 
 
 As the prussian blue is not really dissolved, but only much 
 attenuated, and as it is heavy, it falls down rapidly on the stuff, 
 (rnatiere,) and always in larger quantity on the first that presents 
 itself. It thus happens, that the colour is at first wavy, and 
 
 * L*Art du fabriquant de velours de cotori. 
 
310 
 
 BERTHOLLET ON DYEING. 
 
 often in patches, {placardee,) whatever pains be bestowed. This 
 should excite no surprise. Such accidents must, however, be 
 avoided as much as possible, by w^orking the stuff over and over 
 again, washing with the bath itself the portions most stained, 
 working over again, sometimes one end first, sometimes the other, 
 and then drying ; lastly, working anew, always as equally and 
 quickly as possible. It may now be dried a second time, if 
 necessary, and worked once more till the wished-for shade ap- 
 pear, and the colour be very even. This dye requires the most 
 expert of v/orkmen. Between each drying the stuff is washed 
 and beetled. In all kinds of baths the stuffs must always be 
 previously moistened. Were it dry, the bath would penetrate 
 with difficulty and great inequality. The last time they do not 
 wash, but dry on the pole, in the open air, either in sunshine or 
 shade, provided the piece be well stretched. 
 
 This colour, one of the most beautiful that art can produce, 
 is unalterable in the air, and in all weathers, when it is well 
 done. Roland de la Platiere exposed several patterns of it for 
 six months consecutively ; the colour heightened (raomente) for 
 some time, and finally lost somewhat. The acids are not inju- 
 rious to it ; even boiling in alum affects it slightly ; dust, how- 
 ever, and friction on the creases of it, soon makes it fade. 
 
 The methods heretofore pointed out for fixing the beautiful 
 colour of Prussian blue on stuffs, have not accomplished this 
 object. The first, which form a combination, yield only a weak 
 or very unequal colour ; the last afford but a mechanical fixa- 
 tion of blue molecules, which a slight friction can separate. It 
 has been attempted to give more eftect to the method of com- 
 bination.* 
 
 A combination can be produced between the prussiate of iron 
 and a stuff, only when the oxyde of iron is previously combined 
 with the stuff, so as to receive the prussic acid, because it (the 
 compound) is insoluble, resembling indigo in this respect ; but 
 on impregnating a stuff directly with a solution of iron, in order 
 to combine it with the oxyde of this metal, inequalities are in- 
 evitable, which become very obvious when they are changed into 
 prussiate. This inconvenience is obviated in dyeing the stuff 
 first grey or a deeper shade, according to the blue wished to be 
 
 * Anmiles de chimie, torn, xxi. 
 
OF BLUE. 
 
 311 
 
 obtained ; for in this primary dye, a more uniform combination 
 is made of oxyde of iron and of astringent matter with the stuff. 
 
 An alkaline prussiate would not give up the prussic acid to 
 the stuff ; but on adding an acid, as the sulphuric, the action 
 which this exerts on the base of the alkaline prussiate deter- 
 mines the separation of the prussic acid, which now enters into 
 combination with the oxyde of iron united to the stuff, expels 
 the astringent from it, and takes its place, forming a fine blue 
 colour. All the alkaline prussiates may be employed with this 
 view. 
 
 The process which has been pursued, consists in diffusing, in 
 three or four parts of water, the prussiate of lime, or in dissolv- 
 ing a corresponding quantity of the prussiate of alkali in the 
 water; in keeping the liquor at a heat of 77° to 100° Fahr. 
 and plunging into it for some time the stuff previously 
 dyed, of a shade more or less deep, from grey to black. It is 
 proper to begin with soaking it in hot water, and on taking it 
 out of the liquor, to turn it through cold water. Sulphuric acid 
 answered better than the muriatic. This method may be espe- 
 cially useful for procuring fine greens. We shall treat of it 
 elsewhere. 
 
 The trials were only made on cotton and silk. Bancroft has 
 found the process equally successful with wool. 
 
 The property possessed by the prussiates, of forming blue by 
 giving up the prussic acid to the oxyde of iron, may render 
 them useful on employing them in the same manner to restore 
 the colour of black stuffs, whose astringent has been destroyed 
 by age, and in which the oxyde of iron, grown predominant, 
 produces a russet hue. They may also deepen the imperfect 
 blacks. Thus a mixture of blue and black is made, which in- 
 creases, as we have seen, the intensity of the latter. 
 
 The products of the prussic acid process, which we have just 
 now detailed, have the great inconvenience of being destroyed 
 by the action of alkalies and soap, because the alkalies decom- 
 pose the prussiate which is formed. This is a serious disadvan- 
 tage, particularly for cotton stuffs. If it be used, therefore, on 
 such stuffs, bran or other detergents should be employed, instead 
 of soap, for cleansing them. 
 
 Bancroft has made several interesting experiments, with the 
 view of applying the other metallic prussiates to stuffs. He 
 
312 
 
 BERTHOLLET ON DYEING. 
 
 obtained, in particular, a fine copper-red colour, by using solu- 
 tions of copper. We have got this colour by impregnating 
 cotton with a solution of copper, and following, in other respects, 
 the process just described. Hatchet also made use of solutions 
 of copper for forming, by means of the alkaline prussiates, a 
 prussiate of copper, of a red bordering on brown, which pre- 
 sented interesting properties when employed as a colour, (pig- 
 ment.)* 
 
 The celadon green was formerly given by means of sulphate 
 of copper ; but this colour, which approaches very near to blue, 
 is not permanent, and is no longer in use. The processes em- 
 ployed in it may, however, be pointed out. The cloth, washed 
 in the fulling-mill, and moistened with hot water, is turned 
 through a well saturated solution of soap, for about an hour, 
 when it is passed for half or three quarters of an hour through 
 a solution of sulphate of copper or blue vitriol : by means of a 
 net, the cloth is prevented from being made dull with the sedi- 
 ment of the soap and the sulphate of copper, Occasionally, for 
 obtaining a more decided green, a solution of copper was mixed 
 with the weld bath ; sometimes verdigris was substituted for 
 sulphate of copper. 
 
 Hellot describes a somewhat different process, by which the 
 Dutch produced this colour in perfection. He says that they 
 mixed equal parts of lime and sulphate of copper in a bag ; and 
 that they turned the cloth out of the boiler which contained the 
 solution of soap into another adjoining one, where the particles 
 of copper which escaped through the bag made it green. 
 
 The blue colours procured by means of logwood, of which we 
 shall speak more particularly when treating of the properties of 
 this colouring substance, cannot be compared, in point of dura- 
 bility, to those given by indigo and prussiate of iron. 
 
 * Bibliot. Britann. vol. xxii. 
 
 In the trials of the metallic prussiates, it must not be forgotten that the alkaline prussi- 
 ates contain prussiate of iron, which falls down in tlie operation ; whose colour may make 
 that of the other prussiate to vary. If this be soluble, a result may be ascribed to it, which 
 is in reality owing merely to the prussiate of iron. 
 
SECTION III. 
 
 OF RED. 
 
 CHAPTER I. 
 
 Of Madder. 
 
 Madder, a substance very extensively used in dyeing, is the 
 root of a plant, of which two species are distinguished by Lin- 
 naeus. The first, the rubia tinctorum foUis senis ; the second, 
 rubia peregrina foUis quaternis. The first has two varieties, 
 the cultivated and the wild madder, also named rubia silvestris 
 monspessulana major. 
 
 Although madder can grow both in a stiff clayey soil and in 
 sand, it succeeds better in a rich, soft, moist, and very slightly 
 sandy soil. It is cultivated in several of our departments. That 
 of Zealand was generally regarded as the best which grew in 
 Europe ; but the madder cultivated in the lower departments of 
 the Rhine is not inferior. 
 
 Madder, prepared for the purpose of dyeing, is distinguished 
 into different qualities. That which comes from the parent roots 
 {meres racines) is called garance grape ; and non grape is the 
 produce of the stems that sink into the earth, where they are 
 transformed into roots, to which the name coucMs (layers) is 
 given. Each of these species is subdivided into garance-robee^ 
 mi-robee, non-robee, short or male, (courte ou male,) 
 
 When the roots of the madder are plucked up, the couchis 
 are separated to form the madder non grape, to which are joined 
 the fibres that have not attained a certain size, as well as the 
 roots which are too large, and contain much heart or ligneous 
 substance. The best roots are those which have the size of a 
 writing quill, or at most of one's little finger. They are semi- 
 transparent and reddish, have a strong odour, and a smooth 
 bark. 
 
314 
 
 BERTHOLLET ON DYEING. 
 
 The madder, taken from the ground and picked, should be 
 dried in order to be ground and preserved. It is dried in warm 
 climates in the open air; but elsewhere stoves must be employed. 
 
 It results from this difference of preparation, or perhaps also 
 from a variety in the plant, that two kinds of madder are distin- 
 guished, which differ in their dyeing properties. 
 
 The first, which is cultivated at Smyrna, in the island of 
 Cyprus, and in the Levant, is known under the name of lizari. 
 Its culture is established in our southern departments, where it 
 is by no means of worse quality. We shall now take a summary 
 view of the preparation to which it is subjected in our depart- 
 ments of the south, agreeably to notes given us by Chaptal. 
 We shall afterwards speak of the ordinary madder. 
 
 The roots are dried in the air, on a paved floor, or on a hurdle. 
 They are stirred about with a fork, and slightly beat, in order to 
 separate the epidermis (outer skin) and the earth. What remains 
 on the ground, composed of earth, epidermis, and small roots, is 
 sifted, and that left on the sieve forms what is called billoUy 
 common madder, which is fit for only dull colours. The roots 
 of madder thus picked, are ground, either under a stone mill, or 
 uiider knives similar to those of a bark mill (tan mill.) By means 
 of fanners or a boulter, there is separated, after a first milling, 
 the madder called non-robee. It is composed of a residuum of 
 earth, epidermis, and bark. After a second milling, what is 
 separated is called mi-robee. Finally, after a third milling, the 
 madder robee is obtained, which is of the best quality. The mi- 
 robee is preferable, however, when it comes from somewhat thick 
 roots. When milling is performed for one's own use, only one 
 quality is made ; or if a very brilliant colour be wanted, the 
 worst quality is separated by a first grinding, and the product of 
 the second is employed. This is called in the south, grappier. 
 
 The roots of good quality are of middling size, little branchy, 
 {peu rameuses,) and their fracture is of a lively reddish yellow. 
 Such as grow wrinkled in the course of drying are not good. 
 For the madder to be properly ripened, it should have reached 
 its third year, and be plucked in the fourth. 
 
 The preparation of madders is carried on in the departments 
 of the Rhine by more numerous operations. 
 
 The roots are dried in a stove, heated by means of a furnace, 
 from which the air is allowed to issue only at intervals, at the 
 
OF RED. 
 
 315 
 
 moment when it is judged to be saturated with moisture. The 
 furnace (flue) occupies a great portion of the floor ; above, are 
 three open floors, on which the roots are distributed in layers of 
 about two decimeters (nearly 8 inches.) At the end of 24 
 hours, those which are on the first stage (or floor) directly above 
 the stove are dry, when they are taken away and replaced by 
 those of the superior floors. This operation is repeated when- 
 ever the roots over the stove are dry. The dry roots are thrashed 
 with a flail, passed through a talard similar to that employed for 
 corn, and then passed through a very coarse sieve. What passes 
 through is farther thrashed, talarde^ and sifted through a finer 
 sieve than the first, These operations are repeated five times, 
 proceeding successively to sieves still finer and finer, and setting 
 aside every time what remains on the sieve. What passes through 
 the fifth sieve is rejected as sand and dust. After these opera- 
 tions, the whole roots remaining on the sieve are cleaned with 
 common fanners^ and women separate all the foreign matters 
 which had not been removed before. For dividing the roots, 
 thereafter, in different qualities, a brass sieve is made use of, 
 whose meshes are from six to three millimetres in diameter, 
 (from l-4th to 1-8 inch, E.) What passes through the finest is 
 rejected ; and what passes through the coarsest is regarded as of 
 the best quality. These roots, thus separated, are carried into 
 a stove, of a construction somewhat different from the first. 
 They are spread out in layers of about a decimeter in thickness, 
 (nearly 4 inches E.) on large lattice-work frames, and the drying 
 is known to be complete, when on taking up a handful and 
 squeezing it, the roots break easily. On quitting the stove, the 
 madder is carried, still hot, into a macliine, where it is rasped, 
 and a sieve separates the portion of the bark reduced to powdei:. 
 This operation is repeated three or four times, then the boulter 
 is had recourse to. What passes through the sieve, or the brass 
 meshes of the boulter, is regarded as common madder, and what 
 issues at the extremity of the boulter is called the flour. Lastly, 
 the madder which passes through the boulter is ground in a mill 
 with vertical stones, and then passed through sieves of different 
 sizes. What remains above is always better than what goes 
 through. 
 
 The madder of Alsace is reduced to an extremely fine pow- 
 der, and its colouring matter is extracted by a much longer 
 
316 
 
 BERTHOLLET ON DYEING. 
 
 ebullition than is necessary for the lizari. The prepared mad- 
 ders ought to be carefully preserved from humidity, because they 
 easily imbibe moisture, in which case fermentation spoils their 
 colour. 
 
 D*Ambourney and Beckman have asserted, that it is more 
 advantageous to employ the fresh root of madder than v^hat has 
 been submitted to desiccation, especially by means of stoves. 
 But in its state of freshness, its volume becomes troublesome in 
 the dyeing bath, and uniform observation seems to prove that it 
 ameliorates by age. Besides, it must be rendered susceptible 
 of keeping and carrying easily. 
 
 The celebrated Watt made experiments on a very choice 
 madder from Zealand, v^hich are v^ell adapted to display the 
 properties of its colouring particles. We shall detail them. 
 
 A. This madder is of a brow^nish orange colour, and of the 
 consistence of a coarse powder, possessing a slight degree of 
 cohesion : it attracts moisture, in which case it loses its proper- 
 ties, so as to become unfit for the purposes of dyeing. 
 
 B. With water it affords an infusion of a brownish orange 
 colour ; its colour cannot be extracted without a copious addition 
 of water. Margraff directs three quarts of water for two ounces 
 of madder. Its colouring particles may be extracted either by 
 hot or cold water ; to the latter it appears to give a more beauti- 
 ful colour ; its decoction is brownish. 
 
 C. When an infusion or decoction of this drug is slowly 
 evaporated in an open vessel, a pellicle is formed on the surface, 
 which gradually falls to the bottom ; after which fresh pellicles 
 are successively formed until the evaporation is finished. 
 
 D. The extract thus prepared is of a dark brown ; it partly 
 dissolves in water, to which it communicates a lightish brown 
 colour. 
 
 E. The infusion set to digest for some days in an open vessel, 
 which should be of such a height that the liquor reduced to the 
 form of vapour may fall back again, deposits dark brown pelli- 
 cles. The liquor remains of a brownish colour, and the pellicles 
 are soluble in water, but with difficulty. 
 
 F. Alum forms in the infusion B a deep brownish red preci- 
 pitate, composed of pellicles, and the supernatant liquor is of a 
 yellow colour, inclining to brown. 
 
 G. Fixed alkalies precipitate from this last liquor a lake of a 
 
OF RED. 
 
 317 
 
 blood-red colour, which has greater or less intensity, according 
 to the quantity of alum that has been dissolved in it. In this 
 way, a blood-red lake may be obtained ; but we cannot, by any 
 means hitherto known, give it the brightness of cochineal lake ; 
 in oil it is transparent, but in water it is opaque, and without 
 beauty. 
 
 H. If a superabundant quantity of alkali be employed, the 
 precipitate is re-dissolved, and the liquor becomes red. 
 
 I. The lake precipitated by potash is of a more beautiful 
 colour than that by soda. 
 
 K. Calcareous earth precipitates a more dark and brown 
 coloured lake than alkalies, particularly if it form lime-water. 
 
 L. If a few drops of alkali be added to the water employed 
 in making the infusion B, the infusion extracts many colouring 
 particles of a deep red bordering on brown. 1. Alum precipi- 
 tates a deep brown lake from this infusion. 2, Acids added in 
 small quantity change it to a. yellowish colour, and in greater 
 quantity render it a brown yellow ; but they precipitate nothing 
 from it, 3, This infusion, evaporated to dryness, forms a gum- 
 my extract, which easily dissolves in water. 
 
 M. If the infusion B be made with water very slightly acidu- 
 lated with a mineral acid, it is yellowish. 1. This liquor, hj 
 long digestion, becomes of a greenish-brown, and the yellow 
 appears to be destroyed. 2. The addition of an alkali restores 
 the red colour ; and the infusion then affords, on evaporation, an 
 extract, which readily dissolves in water. 
 
 N. If carbonate of magnesia be added to the water used for 
 the infusion B, the infusion is of a clear blood-red, and on eva- 
 poration forms a blood-red extract, which readily dissolves in 
 water. 1 . A solution of this extract, which is employed as a red 
 ink, when exposed to the light of the sun, becomes yellow. 
 2. Alum precipitates from this infusion a small quantity of an 
 ill-coloured lake. 3. Alkalies give it a redder and more fixed 
 colour. 
 
 O. If the infusion be made with a solution of alum, it is of an 
 orange yellow. This infusion, precipitated by an alkali^ affords 
 a lake resembling that of F, but its colour is not so good. 
 
 P. A solution of sugar of lead, added to the infusion B, forms 
 a brownish-red precipitate. 1. A solution of mercury in the 
 nitric acid, gives a purple-brown precipitate. 2, A solution of 
 
318 
 
 BERTHOLLET ON DYEING. 
 
 sulphate of iron, a fine bright brown precipitate. 3. A solution 
 of sulphate of zinc has not been tried, 4. A solution of sul- 
 phate of manganese, a purple brown precipitate, 5. A solution 
 of iron in aqua regia has not been tried, 
 
 Q. The infusion B being mixed, while hot, with the infusion 
 of cochineal, a brownish-red precipitate, bordering on a deep 
 purple, was formed, of difficult solubility in water. By con- 
 tinuing the digestion, a greater quantity of this precipitate 
 appeared. 1. A pattern soaked in the preparation which the 
 linen printers use, having been dyed in this mixture, took 
 a brownish-red colour ; and after having been boiled in a solution 
 of soap, the colour appeared pretty good. 2. The solution of 
 soap became very red, but communicated a very indifferent 
 colour to paper. 
 
 M. Merime, a painter, who seeks to render physical science 
 subservient to his art, has made some interesting experiments 
 on madder, the object of which was to procure a lake uniting 
 durability to lustre. The results of these experiments, which 
 he has communicated to us, may possibly be useful in dyeing. 
 
 The pellicle, which serves as a bark to the madder root, was 
 separated from its pulpy and ligneous part, and he obtained 
 from both a lake whose lustre approaches to that of carmine, but 
 which is much more durable when he previously submitted them 
 to immersions and lotions, so as to remove a dun colouring sub- 
 stance. The bark, however, yielded less than the ligneous por- 
 tion. After the preliminary immersions, he digested them in a 
 feeble solution of sulphate of alumina ; after which he precipi- 
 tated by alkali this solution, which varied in the depth of the 
 shade. 
 
 It appears then that madder may be considered as composed 
 of two colouring substances, one of which is dun, (tawny,) and 
 the other is red. Both of these substances may combine with 
 the stuff. It is of consequence, however, to fix only the red 
 part. The dun portion appears to be more soluble, but its 
 fixity on stuffs may possibly be increased by the affinity which it 
 has for the red portion. 
 
 The different additions made to madder, and the multi- 
 plied processes to which its dye is sometimes exposed, have 
 probably this separation for their chief object. 
 
 The red portion of madder is soluble, but in small quantity, 
 
OF RED. 
 
 319 
 
 in water. Hence, a limited concentration can be given to its 
 solution. If the proportion of this substance be too much in- 
 creased, so far from obtaining a greater effect, we merely augment 
 the proportion of the dun part, which is the more soluble of the 
 two. 
 
 The red part appears to be especially apt to form the pellicles 
 observed by Watt. De Saussure has shown, that during the 
 formation of these pellicles in the extracts of vegetable sub- 
 stances, for which the contact of air is required, the oxygen gas 
 is changed into carbonic acid ; that water is at the same time 
 formed by the more intimate union of the oxygen and hydrogen 
 contained in the substance, and that the residuum thereby gets 
 an excess of carbon ; so that in the experiments of Watt these 
 pellicles dissolved but partially, and their solution was brown. 
 The red particles, therefore, lose their solubility, and become 
 brown by ebullition, without the influence of atmospheric air. 
 The cause of this last alteration is not hitherto determined by 
 experiment. 
 
 Potash, and carbonate of potash, augment the solubility of 
 the two colouring parts, without accelerating the effect of oxy- 
 dation ; thus, it would seem to be advantageous to add a small 
 quantity of alkali to the madder baths. 
 
 The solution of tin affords lakes devoid of lustre, probably 
 because the two species of colouring matters are precipitated 
 together. This mordant, of so great advantage in a great 
 number of dyes, can hardly be useful in those of madder. We 
 shall see, however, that it is capable of heightening the brilliancy 
 of the Adrian ople red; but at a period of the operation when 
 the dun part has been removed. 
 
 The considerations which we have just now presented, are, in 
 part, nothing but conjectures towards explaining the properties 
 observed in the different processes to which madder is subjected. 
 We suppose, for example, the existence of two species of colour- 
 ing particles ; but these may possibly be derived from a single 
 one, which, by the successive operations that it undergoes, is 
 resolved into two. 
 
320 BERTHOLLET ON DYEING. 
 
 CHAPTER II. 
 
 0/ the Processes used in dyeing with Madder. 
 
 Wool would take with madder only a weak and perishable 
 dye, were not the colouring particles fixed by a base, which 
 combines them more intimately with the stuff, and which screens 
 them in part from the destructive action of the air. For the 
 accomplishment of this object, the stuft' is, first of all, boiled 
 with alum and tartar, for two or three hours ; after which it is 
 drained, slightly wrung, then enclosed in a bag, which is carried 
 into a cool place, and let alone for some days. 
 
 The dose of alum and tartar, as also their relative proportions, 
 vary much in different dye-houses. For one pound of wool, 
 Hellot adopts a little less than the third of alum and tartar. If 
 the proportion of tartar be increased to a certain degree, instead 
 of a red, there would be obtained merely a deep, but durable 
 cinnamon colour ; because the acids tend, as we have seen, to 
 give a yellow hue to the colouring portion of madder. Poerner 
 diminishes somewhat the proportion of the tartar ; of which he 
 prescribes only one-seventh of the alum. Scheffer, on the other 
 hand, prescribes a quantity of tartar double that of alum. But 
 it has been ascertained, that by employing one- half of tartar, the 
 colour inclined more to the cinnamon than when it had been 
 reduced to one -fourth of the alum. 
 
 Ebullition must be avoided for the dyeing bath into which 
 merely madder has been put, because at this degree of heat the 
 colouring substance is easily spoiled, and assumes a deeper hue. 
 
 When the water is no hotter than the hand can endure, Hellot 
 directs to throw into it one part of the finest grape madder for 
 two parts of the wool to be dyed, and to rake well before intro- 
 ducing the wool, which must be kept an hour in it without 
 making the bath to boil ; but to render the dye faster, it may 
 be boiled towards the end of the operation for three or four 
 minutes at most. Beckman recommends to add a little alkali 
 to the madder bath. 
 
 By this process, reds are obtained which are never so beautiful 
 as those of kermes, and much less so than the lac and cochineal 
 
OF RED. 
 
 321 
 
 ones; but as they cost little, they are employed for common 
 stuffs, which could not l3ear the expense of a dearer dye. The 
 madder reds are occasionally rosed with archil and brazil wood, 
 to make them more beautiful and velvety ; but the lustre lent 
 by this means is not lasting. 
 
 Poerner, Scheffer, Bergmann, have employed solution of tin 
 in different modes ; but our own multiplied experiments do not 
 confirm the advantages of these processes. 
 
 Madder does not afford a colour of sufficient brilliancy for 
 dyeing silk, and we conceive it useless to detail the processes 
 which Lafolie, Scheffer, and Giobert have given on this subject. 
 
 Madder is employed for dyeing linen and cotton red, and 
 even for giving them several other colours, by means of different 
 mixtures. It is the colouring drug most useful for this kind of 
 dyeing. It is proper, therefore, to show in sufficient detail the 
 different methods by which this dye may be rendered more per- 
 manent, beautiful, and diversified in its effects. Linen takes the 
 colour of madder with more difficulty than cotton ; but the 
 processes which succeed best with the one, are also preferable 
 for the other. 
 
 Two species of madder red on cotton are distinguished ; the 
 one called simply madder red, the other, possessing far more 
 lustre, is called Turkey red, or Adrianople red, because it was 
 for a long time obtained from the Levant. 
 
 We may also regard as a distinct dye, that employed in calico 
 printing. These three kinds of processes now to be described, 
 may mutually throw light on one another, and serve to deter- 
 mine the most proper means for accomplishing the object of 
 each. 
 
 Vogler has tried the effect of a great number of the substances 
 employed as mordants, or in the dyeing bath, and he found that 
 those which produced the best effect were glue, ox-gall, and 
 other animal matters, as sheep's dung. Muriate of soda ren- 
 dered the colour faster, but more dull. Galling, likewise, pro- 
 cured a richer colour. Other astringents, sumach, and pome- 
 granate rind, for instance, produced a similar effect. A little 
 alkali added to alum improves it. A small quantity of tartar 
 has been useful, but too great a proportion of tartar, as well as 
 of other acids, makes the colour pass to yellow. Different me- 
 tallic salts produced some variations in the shades and solidity, 
 
 Y 
 
322 
 
 BERTHOLLET ON DYEING. 
 
 but not remarkable enough to deserve notice. In speaking of 
 black, we have detailed the process v^hich Vogler indicates for 
 dyeing cotton black by means of madder. He justly remarks, 
 that drying is useful between each operation, after rincing the 
 cotton on its quitting the bath. This diying ought to be per- 
 formed in the shade, especially when alum is employed, because 
 when too much of this is thrown down on the stuff, it crystal- 
 lizes on its surface. He further remarks, that an ebullition of 
 too long continuance in the madder bath destroys the colour 
 with which the stuff is charged. 
 
 In the experiments of Vogler, cotton took the colour always 
 better than thread (linen) ; the difference, however, was not very 
 great, when the subject was a hempen or woollen cloth, a little 
 worn, and become soft to the touch ; and when its texture was 
 very loose, or the yarn was slightly twisted. 
 
 Le Pileur d'Apligny gives a very detailed description of the 
 process followed at Rouen, for dyeing cotton red. "We shall 
 copy it. 
 
 The cotton must be scoured, then galled in the proportion of 
 one part of nut-galls for four of cotton, and lastly alumed at the 
 rate of one of Roman alum for four of cotton, and the same pro- 
 portion of water. To the solution of alum there is added one- 
 twentieth of a solution of soda, made with half a pound of 
 ordinary soda per If pints. 
 
 Some persons put in one-half less soda, and diminish the 
 water by a sixth, replacing the difference by a solution of tartar 
 and arsenic. Le Pileur d'Apligny considers the last ingredients 
 to be hurtful. 
 
 When the cotton has been withdrawn from the mordant, it is 
 gently wrung with the pin, and dried. The more slowly the 
 drying takes place, the more beautiful is the colour. Usually 
 only 22 pounds of cotton are dyed at a time, and it is even more 
 advantageous to dye no more than one half ; because, when too 
 many hanks are worked in the copper, it is more difficult to dye 
 them uniformly. 
 
 The boiler in which this latter quantity of cotton is dyed, 
 should contain about 52^ gallons of water. It is to be heated ; 
 and when the hand can hardly be sufferd in it, 6| pounds of 
 good grape madder of Holland are to be put in, and carefully 
 distributed through the bath. Whenever it is well mingled, the 
 
OF RED. 
 
 323 
 
 cotton is to be plunged into it, hank by hank, previously passed 
 over the sticks, and allowed to rest on the edge of the boiler. 
 The whole cotton having been plunged in the bath, the hanks 
 are worked and turned in succession round every stick, during 
 three quarters of an hour, preserving the bath always at the 
 same degree of heat, without letting it boil. On the expiration 
 of this time, the cotton is lifted up, and withdrawn on the edge 
 of the boiler. About a pint of the soda ley above mentioned, is 
 now poured into the bath. The cotton is again let down into 
 the copper, and is boiled in it for twelve or fifteen minutes. 
 Lastly, it is lifted out, drained, wrung, washed in the river, and 
 wrung a second time on the pin. 
 
 After two days a second maddering is given to this cotton, at 
 the rate of one-half its weight of madder, working it in the same 
 way as for the first maddering, only no ley is added, and pit-well 
 water is used for the bath. This maddering being finished, the 
 cotton is allowed to cool, washed, wrung, and dried. 
 
 Le Pileur d'Apligny thinks that this method of dyeing at two 
 baths is not beneficial, because it wastes more time and fuel, and 
 because the second maddering cannot afford much dye, the salts 
 of the mordant having been exhausted by the first. He pro- 
 poses another method, already pursued, he says, with success, 
 by several dyers. It consists in giving two alumings to the 
 cotton, and then dyeing it in a single bath. 
 
 To brighten this red, a quantity of tepid water, sufficient to 
 soak the cotton, is put into a boiler or a tub. About a pint of 
 ley is poured over it. The cotton is dipped in this bath, by 
 portions, left there an instant, lifted out, wrung, and dried. 
 According to Le Pileur d'Apligny, this brightening is a useless 
 operation. As the red cotton (yarn) is intended for making 
 cloth, from which the dressing must be partially removed after 
 it is woven, the colour of the cotton is brightened at the same 
 time, by being turned through hot water, quickened with a little 
 ley. On taking them out of this water, these cloths are washed 
 in the river, spread out on the grass, where the red brightens 
 much better than it could do by any other operation. 
 
 Wilson rightly prescribes the use of the mordant, known by 
 the name of calico-printers' mordant, which will come under our 
 consideration in dyeing cotton red. By his process, it is requi- 
 
 y2 
 
324 
 
 BERTHOLLET ON DYEING. 
 
 site to gall, dry, impregnate with a mordant diluted with hot 
 water, dry again, madder, wash, and dry. 
 
 The mordant employed for producing reds on printed goods, 
 is the acetate of alumina, prepared by the processes already 
 described, and more or less concentrated, according to the inten- 
 sity of the shade wished to be obtained. 
 
 When the goods have undergone the desiccation, which ought 
 always to follow the printing on (of the mordant), they are turned 
 through a boiler, which contains cow dung diffused through 
 water. For the mordants intended for light shades, it is proper 
 not to leave the cloth in it more than five or six minutes, at a 
 gentle heat, not exceeding 133° Fahr. The heat may be in- 
 creased, and the duration of the dunging, for mordants which are 
 to produce deep colours ; but, in all cases, it is to be conducted 
 with great circumspection, because, by pushing it too far, the 
 mordant is removed from the cloth, and by doing it too little, 
 the mordant not combined with the stuff*, which lies loosely on 
 it, afterwards impoverishes the dyeing bath, and fixes on the 
 portions of the cloth, which are to remain white, some of the 
 colouring matter that cannot be completely destroyed, without 
 affecting the colour very considerably. 
 
 For maddering, the madder is carefully mixed with the hot 
 water of the boiler, immediately after kindling the fire beneath 
 it, and the cloths being attached to each other at their ends, are 
 introduced. They are kept in motion during the whole time 
 that the maddering lasts, so as to be evenly dyed, with which 
 view they are passed round a winch that may be turned by a 
 child. The fire is to be gradually raised, so that the bath be 
 brought into ebullition in three-quarters of an hour, or an hour 
 at farthest. At this period the operation should be stopped the 
 instant that the colours on the cloth have assumed the suitable 
 shade; but if the shades be deep, the maddering may, without 
 inconvenience, be prolonged till the bath becomes dirty, and 
 changes to a tawny hue. In this case, even two madderings 
 should be given to the cloths, dividing between them the quantity 
 of madder requisite for giving the colour all its intensity ; for 
 the colouring matter of the madder is spoiled by ebullition ; and 
 by thus prolonging it, as would be necessary were the whole 
 madder employed in a single bath, we should not only fail in 
 
OF RED. 
 
 325 
 
 raising the colour, on account of the alteration which the co- 
 louring matter experiences, but at a certain term even what had 
 been already fixed on the cloth would be degraded, and thus we 
 should obtain colours which are neither sufliciently deep (strong) 
 nor bright. 
 
 By adding a little potash to the madder the moment it is put 
 into the boiler, the solution of the colouring matter is facilitated, 
 and the colours are more speedily raised. The addition of a 
 certain quantity of chalk appears to brighten the colours a little, 
 especially when they are faint : bran is much more efficacious, 
 and ought not to be neglected when light and brilliant hues are 
 wanted. If the maddering have been well managed, the white 
 ground may be afterwards restored, by passing a single time 
 through bran, and then exposing on the grass. 
 
 Immediately after the maddering, the goods are washed and 
 passed into coppers, in which bran is boiled in water ; they are 
 laid out on the grass ; and these two operations are alternately 
 repeated, till the unprinted parts of the cloth have recovered 
 their whiteness. 
 
 The maddering of printed goods requires pains and precau- 
 tions, which long practice alone can teach. The causes which 
 make their effects to vary, are too numerous for us to point them 
 all out here. The quantity of madder employed, the duration 
 of the maddering, the manner of managing the fire, are, along 
 with the dunging, the circumstances which have most influence ; 
 and they cannot be subjected to any rule, because they must 
 differ more or less in almost every process. 
 
 It is plain, that all these operations have for their objects ; 
 1st, to remove the mordant uncombined with the cloth ; 2d, to 
 fix the colouring matter ; 3d, to carry off*, by the action of the 
 air and bran, the dun colouring matter which is mixed with the 
 madder, as well as the colour which covers the parts of the cloth 
 not impregnated with mordant. 
 
 The cloths intended for printing ought to be very carefully 
 bleached. The more perfect the white is, the more lustre do 
 the colours take, and the more easy is the unmaddering. The 
 fine whites on sale, are not even sufficient ; and it is right to 
 give them, at least, one ley, one exposure on the grass, or one 
 immersion in chlorine acid, and to let them also soak some hours 
 
326 
 
 BERTHOLLET ON DYEING. 
 
 in water acidulated with sulphuric acid. Very frequently, seve- 
 ral leys and several immersions must be given. Thus the dressing 
 (paste) is completely removed, the remaining colouring matter 
 of the cloth is destroyed, which, by fixing in a very durable 
 manner that of the madder, might render the unmaddering a 
 difficult operation ; and thus also the greater number of the 
 stains formed during the maddering, to which the name of mad- 
 der spots is given, are prevented. 
 
 These stains, almost indelible, very common on certain kinds 
 of cotton cloth, and of a colour perfectly similar to what madder 
 gives to those parts of the cloth impregnated with oil, seem to 
 arise from a combination with grease or oil, analogous to what 
 takes place in the preparations of Turkey red. It is very pro- 
 bable that they are produced by the grease employed in the 
 parou, or by the soap which must be employed in bleaching. 
 The combination which in that case may be formed on the stufi", 
 resists the subsequent operations well ; and it will be seen, in 
 the process for the Adrianople red, that the action of alkaline 
 solutions, even pretty concentrated, is insufficient to destroy the 
 combination of the oil with the cotton. 
 
 A strong ley, run off very hot, does not afford a complete 
 guarantee against these spots, although it may be the surest 
 means of avoiding them. It v^ould be of great consequence for 
 calico printers to be able to exclude from weaving and bleaching 
 both grease and soap. 
 
 The Adrianople red has a lustre, which it is difficult to imi- 
 tate by all the processes hitherto described. It has, besides, 
 the property of resisting more completely the action of the 
 different re-agents, as alkalies, soap, alum, acids. Vogler acknow- 
 ledges, that by his numerous processes he has not been able to 
 obtain a red possessing a durability equal to that of Adrianople, 
 although he formed one much more permanent than the false 
 Adrianople reds, which are often used for the siamoises (coarse 
 cotton cloths) and other red goods. 
 
 Aquafortis (dilute nitric acid) is, according to the same author, 
 the surest and most expeditious means for distinguishing the 
 true red of Adrianople from the spurious. It is sufficient to 
 plunge a thread of the latter into it. It is soon seen to grow 
 pale, and in less than a quarter of an hour it becomes white, 
 
OF RED. 
 
 327 
 
 whilst the true Adrianople red remains an hour without being 
 affected, and it never loses the colour entirely, which only turns 
 orange. 
 
 The Adrianople red, which for a long time came to us through 
 our Levant trade only, stimulated the industry of our artisans ; 
 but the attempts were for a long time fruitless, or success was 
 confined to a small number of dyehouses. Abbe Mazaes pub- 
 lished experiments which threw much light on this dye ; and 
 the government promulgated in 1765, from information that it 
 had procured, an instruction, under the title of Memoir^ con- 
 taining the process for the incarnate cotton red dye of Adrianople 
 on cotton yarn. The same description is found in the treatise 
 of Le Pileur d'ApHgny; but this process has not completely 
 succeeded. It appears that the fault consisted principally in the 
 too great concentration of the alkaline solutions. A mystery 
 is made in the different dyehouses of the changes introduced 
 into the process, by means of which more or less success has 
 been obtained. We shall now give the description which Clerc, 
 who conducted with success a manufacture of this kind at Vaud- 
 reuil, communicated to the author of these Elements, and which 
 appears to differ very little from the most usual practice. 
 
 Process of the Adrianople, or Turkey Red. 
 
 Let there be 110 pounds of cotton to dye. We must begin 
 by scouring it well. This operation is performed by boiling the 
 cotton in a copper with a soda ley, at one degree of the areo- 
 meter of Baume, Tw. ;) and there is usually added the 
 remainder of the bath which has served for passing the cottons 
 through in the white preparation, {en Vappret hlanc,) which is 
 called sickiou. 
 
 For scouring the cotton properly, and preventing it from 
 entangling, a cord is passed round three hanks, (the hank is com- 
 posed of four skeins or knots, {pe7ites,) which weigh altogether 
 one pound.) It is thrown into the copper when the ley begins 
 to boil. It is carefully immersed, so that it may not be burned 
 upon the sides of the boiler, which should hold about 131 gal- 
 lons for 110 pounds of cotton. The cotton is perfectly cleansed 
 when it sinks of itself in the copper. It is then taken out and 
 
328 
 
 BERTHOLLET ON DYEING. 
 
 washed knot by knot in the river. Lastly, it is wrung and 
 stretched out to dry. 
 
 Second Operation, — Dung Bath. 
 
 Put into a tub 110 pounds of Alicant barilla, reduced to 
 coarse powder. This tub must be pierced with a hole near its 
 bottom, that the liquid may run from it into another tub placed 
 beneath. The barilla being in the upper tub, about 65^ gallons 
 of ley water are poured over it. When the water which is let 
 off into the inferior tub marks two degrees on the hydrometer of 
 the soap boiler, it is fit for the dung bath, which is made in the 
 following way. 
 
 From 26 to 33 pounds of sheep's-dung are set to steep in a 
 large earthen vessel, in the ley of two degrees, and it is broken 
 down with a wooden pestle. It is then passed through a hair 
 sieve placed over the vat in which the bath is to be prepared, 
 into this vat 13J pounds olive oil of Provence are poured, 
 stirring well with a rake, in order to mix the oil with the soda 
 ley and the dung. Some of the soda ley is poured over it. 
 There are usually required 32 gallons of water to soak 110 
 pounds of cotton. When the bath is thus prepared, the cotton 
 is to be passed through it. 
 
 For this purpose some of the bath is lifted in a wooden bowl, 
 and poured into an earthen vessel, built at a convenient height 
 for working easily, A hank of cotton yarn is taken and worked 
 well with the hands. It is lifted up several times, turning it 
 about in the vessel, and afterwards hung up on a wooden hook 
 attached to the wall. It is slightly wrung out, and thrown on a 
 table. The same operation is repeated on each hank. The 
 table on which the cotton is thrown should be raised two or 
 three decimetres (about 10 inches) from the ground. A work- 
 man takes a hank in each hand, and strikes it on the table to 
 extend the threads. He changes the side (turns it over) three 
 times, afterwards makes a small twist to form a head to the hank, 
 and lays it flat on the table. Not more than three hanks should 
 be put on one another, because too great a load would squeeze 
 the bath out of the under hanks. The cotton must remain on 
 the table 10 or 12 hours ; after which it is carried to the stretch- 
 ing, (frames,) in order to be dried. 
 
OF RED. 
 
 32d 
 
 Third Operation. — Bath of Oil, ot White Bath, 
 
 The ley of soda of two degrees of the hydrometer is taken ; 
 and after cleaning thoroughly the tub in which the dung bath 
 stood, there is put into it Hi pounds of olive oil, and the soda 
 ley is poured over it, stirring with the rake, (paddle,) in order to 
 incorporate the oil. This bath should resemble thick milk ; and 
 when good, the oil must not separate at its surface. Some of 
 this bath is next put into the earthen vessel, and the cotton is 
 turned through it hank by hank, as in the preceding operation. 
 It is thrown upon a table and creped, (that is, beat on the table,) 
 and thereafter left upon the table till next day, when it is taken 
 to the stretching to be dried. 
 
 N,B, About 28 gallons of ley are required for this bath. 
 
 Fourth Operation. — First Salt. 
 
 On the soda sediment in the tub, fresh soda is put, if the 
 water poured over the former has not three degrees. For this 
 operation 28 gallons of soda ley must then be taken, which are 
 poured into the tub over the remainder of the white bath ; and 
 the cotton is passed through it as above. This operation is called 
 giving the Jirst salt. The soda ley has three degrees. 
 
 Fifth Operation. — Second Salt. 
 
 The cotton is passed through a soda ley of four degrees, with 
 the same mode of working as above. 
 
 Sixth Operation. — Third Salt. 
 
 The cotton is passed through a soda ley of five degrees. 
 
 Seventh Operatio7i. — Fourth Salt. 
 
 The cotton is passed through a soda ley of six degrees ; and 
 after being worked with the same pains, it is carried to the 
 stretching to be dried on well-smoothed poles. When the cotton 
 is dry, it is taken to the river to be washed in the following 
 manner. 
 
 Eighth Operation. 
 
 The cotton is to be steeped in water, then withdrawn, and 
 allowed to drain on the horse, {bayard.) Water is thrown on it 
 repeatedly, and at the end of an hour it is washed, knot by knot, 
 
330 
 
 BERTHOLLET ON DYEING. 
 
 to free it thoroughly from the loose oil, a circumstance very 
 essential for its taking the galling well. It is now wrung with 
 the jack and pin, and stretched on the poles to dry. The cotton, 
 when thus washed, should be of a beautiful white. 
 
 Ninth Operation. — Galling. 
 
 For the galling, good nut-galls in sorts (a name known in 
 commerce, the galls in sorts being one-half black galls, and one- 
 half white) should be chosen, and after having bruised them, for 
 110 pounds of cotton pounds are to be put into a copper, 
 and boiled with 21 gallons of pure river water. Three hours 
 are commonly required for boiling them well. The decoction is 
 perceived to be properly done when the galls are easily crushed 
 under the fingers like pap. Ten and a half gallons of fresh 
 water are now to be poured in, and the decoction is then to be 
 passed through a very close hair sieve, kneading the pulp in the 
 hands to extract all the resinous substance. When the water is 
 settled and clear, the galling is to be performed in the^ following 
 manner. 
 
 Into an earthen vessel, fixed in the wall at a convenient 
 height for working, from 2 to 2^ gallons of the nut-gall liquor 
 are poured, and the cotton is passed through it hank by hank, 
 squeezing it well with the fists, then wringing it with the pin ; 
 and in proportion as this is gone through it is immediately carried 
 to be stretched and dried, an essential precaution, which prevents 
 the cotton from blackening. When the cotton is dry, the alum- 
 ing is to be performed in the following manner. 
 
 Tenth Operation. — Aluming. 
 
 After thoroughly cleaning the copper, in which the decoction 
 of galls was made, 28 gallons of river water, and 42 pounds of 
 Roman alum are introduced, and dissolved without boiling. 
 When the solution is complete, 1} gallons of soda ley of five 
 degrees are poured in ; and through this, the cotton is passed 
 hank by hank as for the galling. It is afterwards stretched out 
 to dry. It is washed from the alum as follows. 
 
 Eleventh Operation. — Washing from the Alum. 
 
 After having allowed the cotton to steep, and drained it on 
 the horse (hayardy) each hank is to be three times separately 
 
OF RED. 
 
 washed, then wrung with the pin, and taken to the tenter 
 ground. 
 
 Twelfth Operation. — Remounting on the Galls, 
 {Remonter stir Galle,) 
 
 This operation consists in a repetition of the preceding ones, 
 A white bath is prepared like that described in Article 3 ; 13f 
 pounds of good fat oil of Provence are put into a tub, and 28 
 gallons of soda ley are poured over it, of two degrees of the 
 {pese-liquer) hydrometer of the soap boilers. Care is taken to 
 stir the bath well, and the cotton is passed through it, as has 
 been described in the 3rd Article. 
 
 Thirteenth Operation. — First Salt. 
 
 The cotton, after being well dried, is passed through a soda 
 ley of three degrees. 
 
 Fourteenth Operation. — Second Salt. 
 
 The cotton being dried, is passed through a soda ley of four 
 degrees. 
 
 Fifteenth Operation. — Third Salt. 
 
 The cotton is passed, when dry, through a soda ley of five 
 degrees, when all the dips are finished. It is now dried, washed, 
 galled, and alumed with the sam$ doses and the same attentions 
 described in Articles 9, 10, and 11. The cotton has then all the 
 necessary preparations for taking the dye well. The cotton, on 
 quitting these preparations, should be of the colour of the bark of 
 a tree. A very essential point to be observed, is to submit the 
 cotton to no dip till it be perfectly dry, without which there 
 would be a risk of the dye being mottled. When the cotton is 
 stretched on the poles, it must be carefully shaken and turned 
 over to dry it uniformly. 
 
 Sixteeiith Operation. — Dyeing. 
 
 A copper of an oblong square form is usually employed. It 
 should hold about 87 gallons of water, and at this rate 27 pounds 
 of cotton may be dyed in it at a time. To commence the opera- 
 tion of dyeing, the boiler is to be filled with water to within 
 four or five inches of the top ; there is next poured into it a 
 pailful of ox-blood, or sheep's blood, which is better when it 
 
332 
 
 BEIITHOLLET ON DYEING. 
 
 can be had, containing about 5| gallons of blood. The lizari 
 fine madder is now introduced. When a fine lively striking 
 colour with much body is wanted, several lizaris are mixed to- 
 gether ; for instance, pounds of lizari of Provence and 
 I" pound lizari of Cyprus ; or if there be none of Cyprus, equal 
 parts of the lizari of Provence, Tripoli, or Smyrna. The dose 
 is always two parts to one of cotton. When the lizari is in the 
 copper, it is stirred with a rake to break down any lumps ; and 
 whenever the bath is tepid, the cotton stretched on skein sticks, 
 called lisoirs, is plunged into it. Two hanks are usually put on 
 each stick. Care should be taken to immerse it well, and that 
 the cotton be turned round the lisoirs, end for end, by means of 
 a pointed stick passing between the hanks and the lisoirs that 
 the cotton rests upon. This operation lasts an hour ; and when 
 the copper begins to boil, the cotton is taken off the lisoirs, and 
 plunged into the copper, each hank being suspended by means 
 of a cord passed through its sticks suspended over the copper. 
 The cotton should be kept boiling for about an hour, in order to 
 extract the whole colouring substance of the madder. There is 
 a method besides, of ascertaining when the colour is extracted ; 
 for a white froth then forms on the copper. The cotton is now 
 tossed out of the boiler, and washed skein by skein in the river ; 
 then it is wrung with the pin, and hung up to dry. 
 
 Seventeenth Operation. — Brightening. 
 
 Into the boiler employed for the scouring, which should be 
 capable of holding 131 gallons of water, soda ley of 2° of density 
 is poured, with which it is filled to within 10 or 12 inches of the 
 top. There is next poured in from 4 to 5^ pounds of oil of 
 olives, and 6|- pounds of white Marseilles soap sliced very fine. 
 The whole is well stirred till the soap be melted ; and when the 
 copper begins to boil, the cotton is introduced, a cord being pre- 
 viously passed through it to prevent its entanglement. The 
 copper is covered up, its lid is stuffed with old linen, loaded, and 
 made to boil with a small fire for four or five hours. The cop- 
 per is then uncovered, when the cotton should appear finished, 
 and of a beautiful red. The cotton should not be withdrawn 
 from the copper till the end of ten or twelve hours, because it 
 becomes richer in the brightening, and takes more lustre. 
 
 It must thereafter be well washed, skein by skein, and dried, 
 when the operation is complete. 
 
OF RED. 
 
 333 
 
 I am in the habit of giving my cottons one dip after they are 
 well dried. It consists in making a solution of tin in nitric acid, 
 with 1-1 6th of sal ammoniac. I dilute this solution with 28 
 gallons of water, and 1 pass my cotton through it. It must be 
 afterwards washed. This dip gives a very fine lustre to the 
 cotton. 
 
 N.B. — Into the sickiou tub only the remainder of the first 
 preparations {apprets) is put. What remains after the cotton 
 has been galled is good for nothing and must be thrown away, 
 
 Chaptal, whose researches and enlightened zeal for the 
 advancement of the arts have contributed so much to their pro- 
 gress, has had the kindness to communicate to us the notes 
 which he had collected in his dye-houses, near Montpellier. We 
 have extracted from them the following processes for dyeing 
 Adrianople red, which he has long practised himself with much 
 success. 
 
 The first precautions to be taken in this dye, consist in the 
 good choice of materials. The fittest oil for this operation is 
 what comes from the river of Genes, under the name of dyeing 
 oil. Some is also brought from the south of France. To try 
 these oils, some drops are poured into a glass so as to cover its 
 bottom, and it is filled up with soda ley, marking from 1° to 2° 
 on the areometer of Baume, (1^° to 3° Tw.) The mixture 
 becomes milky ; this soapy liquid is transferred several times 
 from one glass to another, in order to mix it well. It is then 
 left at rest for several hours. The liquor should remain uni- 
 formly milky, provided the oil be good ; if it separates in little 
 drops, or if the bottom of the liquor assumes the appearance of 
 ill clarified whey, while on the top a pasty zone {bourlet) forms, 
 the oil is of bad quality. 
 
 The sodas (barillas) of Spain, Alicant, or Carthagena are to 
 be preferred. In the absence of these, that of Narbonne may 
 be used. Good soda should be very hard, grey outside, blackish 
 in its fracture, difficult to pulverize, and soluble. Such as have 
 effloresced in the air, and in which muriate of soda abounds, 
 cannot be employed for fine colours. 
 
 In the operations about to be described, the proportions are 
 given for one portion of cotton weighing 220 pounds. 
 
 The cotton is scoured by boiling it in a soda ley, which marks 
 from 1° to 3° on the areometer of Baume, (U° to 4^ Tw.) For 
 
33i 
 
 BERTHOLLET ON DYEING. 
 
 this purpose, the residues of the sodas employed for the sapo- 
 naceous emulsions are used. The cotton is known to be com- 
 pletely scoured when it sinks well, and when no hank comes 
 floating up ; it is then washed and dried. 
 
 To give cotton the first preparations, we prepare a soda ley at 
 1° in a great earthen jar, with about 33 gallons of water. We 
 try if it cuts the oil w^ell, that is to say, if on pouring in a few 
 drops of oil, it mixes well, growing milky, without leaving any 
 little drops at the surface. In a jar of the above size, we mix 
 22 pounds of oil with one-third of this ley, agitating carefully. 
 Along with the second third, we mix from 26 i to 29 pounds of 
 the liquor found in the stomach of ruminating animals. This 
 mixture is to be poured into the jar where that of the oil was 
 made, and after adding to it the last third of the ley, we stir 
 again with very great care. For passing the cottons through this 
 saponaceous liquor, some of it is put into smaller jars, and after 
 impregnating the cotton well with it, this is strongly wrung out. 
 In proportion as we drain the jar, we agitate to prevent any 
 separation taking place in the liquor. 
 
 The cotton passed through the oil remains piled up in a heap 
 till next day, when it is taken to the tenter poles. As soon 
 as it is dry, it is passed through a weak ley of soda, which has 
 been mixed with the small residue of the soapy liquid ; and it is 
 in like manner left in a heap till it be carried next day to the 
 drying. It is passed, when dry, through a second ley a little 
 stronger than the preceding. 
 
 The second soapy liquor is prepared with the same precautions 
 as the first. There is employed for it the same quantity of ley, 
 marking from V to 2°, and about 17| pounds of oil, but no ani- 
 mal liquor is mixed with it. When the cotton is passed through 
 this second oil, 44 pounds of soda are added to the 33 pounds 
 previously used. The cotton is passed three or four times 
 through the leys of this soda, taking the precaution of increasing 
 each time the strength of the ley by half a degree, so that the 
 last shall mark nearly 3"" or 4° of Baume. (5° to 6^° Tw.) 
 
 In this operation potash may be substituted for soda. The 
 cotton takes in fact a wine colour, but it loses this hue in the 
 brightenings. 
 
 To prepare the cotton well for the galling and the aluming, it 
 must be washed and dried. The galling bath is prepared, by 
 
OF RED. 
 
 335 
 
 boiling 22 pounds of sorted galls in powder with about 22 gal- 
 lons of water, in which 33 pounds of sumach have been pre- 
 viously boiled. After half an hour's boiling, 1 1 gallons of cold 
 water are poured into the copper, that the bath may be large 
 enough for all the cotton to be passed through it. The cotton 
 is dipped in as soon as the heat of the bath permits, and in the 
 same manner as in the soapy liquor. It is then taken to the 
 tenter poles. 
 
 The galling is one of the most delicate operations. It is of 
 consequence to impregnate, wring out, and dry the cotton very 
 equally, as well as to dry it neither too slowly, nor in too moist 
 an air, because the parts of the cotton that suffer the action of 
 the air most, blacken, while the others remain of a white-grey. 
 This produces inequalities. 
 
 As soon as the galling is dry, the cotton is alumed. "With 
 this view, 33 pounds of reddish Levantine alum, or 27i of 
 Roman alum, are dissolved in 22 gallons of water. Whenever 
 the solution is completed, about 1 1 gallons of cold water are 
 poured into the copper, and as soon as the solution acquires a 
 gentle warmth, much below that of the galls, the cottons are 
 passed through it, and dried. 
 
 The alumed cotton should be thoroughly washed before pro- 
 ceeding to the other operations. Whenever it is well washed 
 and dry, it is passed through one oil and three leys. The sapo- 
 naceous liquor is prepared with 15 to 17^ pounds of oil, and the 
 ley of the remainder of the sodas, which have served for the 
 first preparations, which marks, as in the first, only from 1 to 2 
 degrees. 
 
 Thirty-three pounds of soda are now added to the jar, and the 
 first ley is given at 3 degrees, raising each of the succeeding ones 
 by half a degree, so that the strongest shall stand at from 4 to 5 
 degrees. After the third ley, it is washed and galled in a bath 
 of 16i pounds of galls, without sumach. The aluming is made 
 with 22 pounds of Roman alum ; after which it is powerfully 
 washed and dried. All these operations must be conducted with 
 the same pains as the first. 
 
 In order to have a very uniform colour, 4 pounds of madder 
 must be employed for every 2 pounds of cotton. With this 
 madder 1 pound of sheep's blood is mixed for every 2 pounds of 
 cotton, and it is put into the bath whenever it is tepid. The 
 
336 
 
 BERTHOLLET ON DYEING. 
 
 cotton is turned in for an hour. When it is boiled for an equal 
 time, it is withdrawn, and washed. It is now of a deep red, or 
 bullock's blood colour. If the blood have not been intermingled, 
 the colour is not so lively, nor so rich, although it be durable ; 
 and by substituting for it glue and other animal products, no 
 such agreeable colour is obtained. 
 
 The colour of the cotton, after the maddering, is so dull and 
 dark, that it could not be employed in this condition. It is 
 cleared up, or lustre is given it by the hrighteningy and by solu- 
 tion of tin, which the workmen call the secret. 
 
 The brightening consists in boiling the cotton, for 6 or 7 hours, 
 in the ley of 66 pounds of soda, marking 2°, to which 17 to 20 
 pounds of soap are added. The cotton is not put into the copper 
 till the liquid be boiling hot. The copper is carefully covered, 
 leaving but a small outlet for the steam, and the lid is strongly 
 fastened down, that it may not be lifted up by the compressed 
 vapour. The duration of the ebullition varies according to the 
 intensity of the colour of the cotton, and the strength of the 
 ley employed. When the cotton is thought to be sufficiently 
 brightened, the fire is stopped, the brightening (copper) is unco- 
 vered, and a hank is pulled out with an iron hook. If, after 
 washing it well, the colour appears brilliant, and has not any 
 black tint, or if some parts of the cotton begin to be impover- 
 ished, the copper is filled up with fresh water, and a stopcock is 
 opened to run it off*. Thus the cotton is washed, and is then 
 left in the boiler till next day. It is now washed and dried. 
 
 In this condition, the cotton is of a fine colour; but it receives 
 more lustre by the secret. 
 
 The solution of tin is prepared with pure nitric acid, marking 
 32°. 465 grs. of sal ammoniac are dissolved in the cold, in every 
 pound of acid. When the solution is made, the tin is introduced 
 in small rods, in the proportion of 465 grs. to the pound. It 
 dissolves readily, and the liquor becomes opalescent. Tin is 
 added even till this hue is perceived, which indicates that the 
 acid can dissolve no more. 16^ pounds of this solution are 
 poured on a solution, somewhat tepid, of 6^ pounds of Roman 
 alum, put into a large jar. In proportion as the solution of tin 
 is poured into that of alum, the mixture grows turbid and white ; 
 at this time the cotton is passed through it with pressure, as 
 usual. It is washed as it passes through. 
 
OF RED. 
 
 837 
 
 The mixture of the two solutions should be capable of causing 
 effervescence with calcareous earth, otherwise it will not brighten 
 the colour properly. More or less solution of tin is employed, 
 as the colour is to be more or less deep. 
 
 The lustre of the cotton may be further increased, by reviving 
 it with an ebullition of 4 or 6 hours in a solution of from 17^ to 
 22 pounds of soap. 
 
 Linen yarn takes a colour almost as brilliant as that of cotton, 
 but it must be passed through a double number of oils and 
 leys. The latter must be even very strong, otherwise the oil 
 flows out on the surface. The greatest attention must be be- 
 stowed on the scouring at first ; for the yarn mingles and en- 
 tangles by the heat, to such a degree that it can be neither 
 dipped nor unravelled. 
 
 A very beautiful red is also obtained by limiting the galling 
 and aluming to a single time, after the three oilings ; and by 
 observing to increase the doses of gall-nuts and alum a little. 
 
 By the following method we procure red colours, beautiful 
 and permanent, without employing ley, oil, or galls. 
 
 Lime slaked in the air is to be dissolved in cold acetic acid. 
 The solution marks from 5^ to 6^ ; and it is reduced to 2° by 
 the addition of water. Equal parts of this solution and acetate 
 of alumina are mixed. The latter is prepared by pouring 1 1 
 pounds of acetate of lead into a solution of 44 pounds of alum 
 for 38 gallons of water. The above mixture is made tepid, and 
 the cottons, merely scoured with care, are passed through it. 
 They are dried, thoroughly washed, dried and maddered with 
 1| pound of madder for 2 pounds of cotton. They are bright- 
 ened with ley and soap, then passed through a solution of tin, 
 and revived with soap alone, in the proportion of 26 pounds of 
 soap for 220 pounds of cotton. 
 
 Very durable reds may be had by passing the cotton through 
 this mordant, after having submitted it to oiling without galling. 
 They are even very deep. But on passing the cotton which has 
 received a single oil and four leys, through a mixture of acetate 
 of alumina, with l-4th, 1-1 2th or 1-18 of lime, various very 
 lively shades are obtained. 
 
 For making a dead red without lustre, termed in some places, 
 burned red, or Indian red, on account of its resemblance to that 
 of Indian handkerchiefs, the cotton is scoured, boiled for half 
 
 z 
 
338 
 
 BERTHOLLET ON DYEING. 
 
 an hour in lime water, passed through an oil mixed with some 
 intestinal liquor, and through three leys. It is washed well and 
 turned through a mordant composed of a tepid solution of 27i 
 pounds of alum, to which 9 pounds of acetate of lead have been 
 added; and a moment afterwards, 1 pound of soda in powder 
 and half a pound of sal ammoniac. It is washed with care, and 
 maddered with its own weight of madder. If the colour be 
 poor, it is passed once more through an oil, two leys, the same 
 mordant, and a maddering. It may be brightened with soda 
 and soap. The lime alone produces the difference between this 
 colour and the preceding. It renders the colours more per- 
 manent, but duller. 
 
 The durable rose (colour) is produced by taking cotton passed 
 through the oils, and which has received more numerous but 
 weaker leys. It is galled with a ley of sumach, in which 5^ 
 pounds of gall-nuts have been boiled; and alumed with 38^ 
 pounds of alum. It is now washed, dyed with madder of the 
 best quality, the madder bath being whitened (blanchi) with 
 4 pounds of the oxyde of tin, that precipitates from the solution 
 of this metal in nitric acid. It is brightened with weak ley and 
 soap, dried, passed through a liquor formed of a solution of tin 
 (in nitric acid at 32^, diluted with an equal volume of water), 
 reduced to 4^. It is now washed and brightened In a solution 
 of 33 pounds of soap, till the colour be rosed in perfection. 
 
 On passing the cotton through soap of wool made with soda, 
 taking the same pains as with the soapy liquor prepared for the 
 red, and using very weak leys in the interval, then washing the 
 cotton, and treating it by the same process as for dyeing wool 
 scarlet, it assumes a scarlet tint, paler than that of wool, but 
 pretty brilliant. 
 
 Cotton died red may, moreover, be made to pass through all 
 the shades, down to the palest orange. For this purpose, pure 
 nitric acid is diluted with 3-5ths of water; chips of tin are 
 oxydized in it till the liquor grows opalescent, and the solution 
 is employed, at different strengths, from 2^ to 20^. The colour 
 varies according to the concentration of this solution. When it 
 is from 16° to 20, shades are obtained which have some relation 
 to those of scarlet. 
 
 In general, when brilliant colours are desired, we must not 
 charge them too much with oil ; we must give feeble leys long 
 
OF RED. 
 
 339 
 
 repeated, charge little with alum, employ the best madders, and, 
 at last, brighten powerfully, without sparing the soap. 
 
 Chaptal * has expounded the principles on which are founded 
 the multiplied operations of the Adrianople red dye, one of great 
 importance in itself, and whose processes may have to a certain 
 extent several useful applications. 
 
 He shows, that all these . operations have for their object a 
 triple combination ; the first, that of the oil with the stuff ; the 
 second, that of the tanning with the former ; the third, that of 
 the alumina with the preceding two. To this triple combination 
 there is lastly added, that of the colouring substance of the 
 madder. Its dun portion is separated by the brightening, and 
 the lustre of the red portion is increased by a judicious applica- 
 tion of the solution of tin. 
 
 The oil must be brought into a disposition to combine with 
 the stuff. For this purpose, solubility in water is communicated 
 to it by means of soda ; but the oil must be slightly retained by 
 the alkali. Hence, merely a weak solution of soda should be 
 employed, leaving the oil predominant, in order that the alkali 
 may not seize it, and separate it from the stuff. 
 
 The oil, to be fit for combining with the stuff, must not be a 
 fine oil ; but it should have a tendency to form a solid combina- 
 tion ; which is undoubtedly indicated, when it is said, it should 
 contain a strong ^portion of extractive principle^ 
 
 Gall-nuts have an advantage over the other astringents, be- 
 cause the gallic acid, tending to combine with the alkali retained 
 by the stuff, favours the more intimate combination of the oil 
 with the stuff and the tannin. 
 
 Chaptal observes, on this occasion, that we may observe a 
 combination of oil with tannin, on mixing a decoction of nut- 
 galls with a solution of soap. It is of consequence to make this 
 combination in due proportions ; for if the • astringent predomi- 
 nates it grows black ; if it be in too small quantity, the colour 
 becomes too weak. 
 
 When sulphate of iron, or acetate of alumina, is mixed with 
 a decoction of gall-nuts, a greyish precipitate is formed ; in like 
 manner, galled cotton becomes grey the instant that it is plunged 
 into an aluminous solution. Too hot a solution must be avoided, 
 
 * M^moires de I'instit. vol. ii. 
 
 z 2 
 
340 
 
 BERTHOLLET ON DYEING. 
 
 because a portion of the astringent is dissolved, which would 
 impoverish the colour. 
 
 Haussman* employed^, with success, solution of alumina in 
 alkali. To obtain this solution, he precipitated the alumina of 
 sulphate of alumina by caustic potash, of which he added such a 
 quantity, that all the precipitate first formed was redissolved ; 
 to this solution he added l-33d of linseed oil, which formed a 
 liquor having the appearance of milk. As the oil separates with 
 standing some time, the liquor must be agitated before using it. 
 The hanks of cotton, as also those of linen yarn, should be suc- 
 cessively steeped in it, evenly wrung out, and dried in the shade 
 for 24 hours. After this they are washed, and the operation is 
 renewed. Two impregnations are sufficient for obtaining a fine 
 red, but by means of a third and a fourth, very brilliant colours 
 may be produced. 
 
 The intensity of the red depends on the quantity of madder 
 employed in the dye ; with a weight equal to the hanks, the 
 colour becomes rose by brightening ; with four times the weight 
 the finest red is produced. The author prescribes the addition 
 of carbonate of lime to the madder, always when the water made 
 use of naturally contains none. Its effect is to decompose the 
 sulphate of magnesia, which Bertholdi found in madder ; pro- 
 vided the carbonate of lime can decompose the sulphate of mag- 
 nesia, and if it be more advantageous to have sulphate of lime 
 than sulphate of magnesia present. 
 
 He employs for the brightening, water alone, containing a 
 small bag of bran, keeping up the ebullition for eight hours, and 
 replacing what evaporates. 
 
 A great variety of different shades may be procured, by giving 
 another colour to cotton before passing it through the oil bath. 
 
 Pallas relates, in the Journal of Petersburg for 1776, that the 
 Armenians, whom the troubles of Persia obliged to retire to 
 Astracan, dye Turkey red by impregnating cotton with fish oil, 
 and drying it alternately during seven days ; that they have re- 
 marked that the other oils would not succeed ; that they did 
 not take indifferently the oil of every fish, but chose that of 
 certain fish, which becomes milky whenever an alkaline solution 
 is mixed with it. After these repeated impregnations and de- 
 
 * Annal. de chim. torn. xli. 
 
OF RED. 
 
 341 
 
 siccations, they wash the cotton, and dry it. They give it then 
 an astringent bath, into which they put a little alum. They 
 dye it in a bath of madder, with^ the addition of calf's blood. 
 Lastly, they digest it for 24 hours in a solution of soda. 
 
 If cotton dyed with madder, by any process whatsoever, be 
 boiled for some minutes in soap water, it assumes a rose colour. 
 If it be then squeezed, a fat matter is expressed from it, which 
 has the colour of Adrianople red, and which fixes itself on white 
 cotton. CEtinger observed, in 1764,* that oil had the property 
 of dissolving the colouring part of the Adrianople red, so that, 
 if it be moistened with oil, its colour is communicable to white 
 cotton when rubbed with it for some time. He thence con- 
 cluded, that oil must enter into the preparation of the Adrianople 
 red ; and the Abbe Mazeas had proved long ago, that oil was 
 indispensable to this dye.f 
 
 The species of madder employed has a great influence on 
 the colour obtained. It appears indispensible, for procuring 
 a colour equal to the Adrianople red, to employ the kind called 
 lizari. 
 
 We should distinguish, in madder-dyed cotton, between the 
 faculty of resisting, for a long time, the action of air, and that 
 of resisting alkalies and soap. The last can only be obtained by 
 means of oils and fats ; but the first depends chiefly on the 
 mordants that are used, and the other manipulations. Thus, 
 the reds on printed stufls may be very permanent, without sup- 
 porting the action of leys, as the red of A drianople does. 
 
 It is therefore right, independently of the beauty of the 
 colour, to employ processes analogous to that of Adrianople, for 
 such stufls as are to be exposed to leying, and to frequent 
 washing with soap. (Note II.) 
 
 * Dissertatio de viribus radicis rubise tinctorum antiarchiticis a virtute ossa animaliiim 
 vivorum tingendi non pindendibus. 
 
 t Recherches sur la cause physique de Tadhereiice de la couleur rouge, &c, Mem. des 
 savans etiangers, torn. iv. 
 
342 
 
 BERTHOLLET ON DYEING. 
 
 CHAPTER III. 
 Of Cochineal. 
 
 Cochineal was taken at first for a grain, but the observations 
 of Lewinhoek showed that it was an insect. It is brought to us 
 from Mexico. This insect lives there on different species of 
 opuntia. The female has the body flattened on the side of the 
 belly, and hemispherical on the back, which is marked with 
 transverse wrinkles. Its skin is of a dull brown. Its mouth 
 is an awl-shaped point which issues from the cavity of the thorax. 
 It has six very short brown feet, and no wings. The male has 
 the body much elongated, of a deep red colour, covered with 
 two wings, extending horizontally, and crossing a little on the 
 back. It has two small antennae at the head, and six feet, 
 larger than those of the female. Its flight is not continuous, 
 but it flutters about, hopping very rarely. Its life is only one 
 month in duration, and ends with its amours. The fecundated 
 female lives a month longer, dying after parturition. It is some- 
 times oviparous, and sometimes viviparous. After their birth 
 the young females disperse themselves on the joints of the 
 opuntia, where they fix themselves by their proboscis till the 
 end of their lives. 
 
 Two sorts of cochineal are gathered in Mexico. The wild 
 cochineal, called by the Spanish name grana silvestra, and the 
 fine cochineal, or grana Jina^ termed also mesteque, from the 
 name of a province of Mexico, and which is bred on the nopal. 
 The first is smaller, and covered with a cottony down, which 
 increases its weight with a matter useless in dyeing ; it yields, 
 therefore, in equal weight, less colour, and is of inferior price to 
 that of the fine cochineal. But these disadvantages are perhaps 
 compensated by its being reared more easily, and less expen- 
 sively ; and by the effects of its down, which enables it better to 
 resist rain and storms. 
 
 The wild cochineal, when it is bred on the nopal, loses in part 
 the tenacity and quantity of its cotton, and acquires a size 
 double of what it has on the other opuntias. It may therefore 
 be hoped, that it will be improved by persevering care in the 
 
OF RED. 
 
 343 
 
 rearing of it, when it will approach more and more to fine 
 cochineal. 
 
 Thieri de Menonville exposed himself to the greatest dangers 
 in going to observe the breeding of the cochineal at Mexico, in 
 order to carry away this precious production, and enrich the 
 colony of St. Domingo with it. He brought back with him 
 some of the fine cochineal, of the wild cochineal, and of the 
 nopals, which are the species of opuntia best adapted for 
 nourishing these insects. 
 
 On his return, he occupied himself with the cultivation of the 
 nopal, the different species of opuntia, and the rearing of the 
 two cochineals ; but death suddenly cut him off, and the fine 
 cochineal soon perished. On his return he had observed 
 the wild cochineal on a species of opuntia named peres- 
 cilia, or patte de torUie, which is found at St. Domingo. This 
 discovery did not remain unproductive. Bruley engaged with 
 success in the rearing of this cochineal. The circle des Phila" 
 delphes employed themselves on it, and published a posthumous 
 work of Thieri de Menonville, in which very detailed instruc- 
 tions are given relative to the cultivation of the nopal, and the 
 other opuntias which may be substituted for it with more or less 
 success ; as also the rearing of the cochineal, and its prepara- 
 tion,* 
 
 Two months after the mothers kept in reserve have been sown 
 on the nopal, some young cochineals are seen to issue from them. 
 This is the moment when the crop should be gathered. They 
 are killed in boiling water. The plates of hot iron, and the 
 stoves occasionally employed, may deteriorate the cochineals by 
 too great a heat. After they are taken out of the water, they 
 are carefully dried in open sunshine. They lose nearly two- 
 thirds of their weight in the desiccation. 
 
 When the fine cochineal is dry, it is to be passed through a 
 sieve large enough to let it go through, but capable of stopping 
 the passage of the bourres (downs) and cotton of the larvae of 
 the males. The bourres (coarse downs) are put by themselves, 
 and sold separately, or along with the wild cochineal. 
 
 The fine cochineal, when well dried and well preserved, should 
 
 * Traitd de la culture du nopal, et de Teducatioii de la cochenille dans les colonies 
 Fran^aises de TAm^rique, precede d'un voyage a Guaxaca, par M. Thieri de Menonville. 
 Ann, de cliim. torn. v. 
 
344 
 
 BERTHOLLET ON DYEING. 
 
 have a grey colour, bordering on purple. The grey is owing to 
 the powder, which naturally covers it, and of which a little ad- 
 heres. The purple shade arises from the colour extracted by 
 the water in which they were killed. 
 
 Cochineal keeps for a long time in a dry place. Hellot says 
 that he has tried some 130 years old, which produced the same 
 effect as new cochineal. 
 
 It has been pretty generally believed, that cochineal owed its 
 colour to the nopal on w^hich it lives, the fruits of which are red. 
 But Thieri de Menonville observes, that the juice which serves 
 for its nourishment is greenish; and that it can live and breed on 
 a species of opuntia whose fruit is not red. 
 
 The decoction of cochineal is of a crimson hue, inclining to 
 violet. 
 
 A small quantity of sulphuric acid caused this liquor to assume 
 a red colour verging on yellow ; and a little precipitate, of a fine 
 red colour, was formed. . 
 
 The solution of tartar changed the liquor to a yellowish-red. 
 A slight pale red precipitate is slowly formed. The supernatant 
 liquid remained yellow ; on pouring into it a little alkali, it took 
 a purple hue. The alkali quickly dissolved the small precipi- 
 tate, and the solution was purple. Solution of tin formed a rose 
 precipitate with the yellow liquor. 
 
 Solution of alum cleared up the colour of the infusion, giving 
 it a redder tint. A crimson precipitate fell, and the superna- 
 tant liquid retained a crimson colour, slightly reddish. 
 
 The mixture of alum and tartar produced a brighter colour, 
 more lively, inclining to yellowish-red. A much less abundant 
 precipitate was formed, and much paler than in the preceding 
 experiment. 
 
 The solution of tin formed a copious deposite, of a beautiful 
 red. The supernatant liquid was clear, and did not change 
 colour on the affusion of alkali. 
 
 Having poured in the solution of tartar, and afterwards the 
 solution of tin, there was formed, more speedily than in the 
 preceding experiment, a rose deposite, verging on lilac; and 
 although a superabundance of the tin solution was added, the 
 supernatant liquor remained a little yellow. 
 
 The solution of muriate of soda rendered the colour a little 
 deeper, without making the liquor turbid. 
 
OF RED. 
 
 345 
 
 Muriate of ammonia gave a shade of purple without causing 
 a precipitate. 
 
 Sulphate of soda produced no sensible change in the liquor. 
 
 Having boiled a little cochineal with half its weight of tartar, 
 the liquor inclined more to the red, and had a much deeper 
 colour than that proceeding from an equal quantity of cochineal 
 without tartar; but the first yielded, with the solution of tin, a 
 much more abundant precipitate, which had a more intense 
 colour, so that the tartar promotes the solution of the colouring 
 particles of the cochineal. Although the colour of the solution 
 be less deep, the precipitate derived from it by the solution of 
 tin has a livelier hue. 
 
 Sulphate of iron formed a brown-violet precipitate, and the 
 supernatant liquor remained clear, with a dead-leaf cast {feuille 
 morte). 
 
 •Sulphate of zinc caused a precipitate of a deep violet ; the 
 supernatant liquor remained clear and colourless. 
 
 Acetate of lead afforded a purple-violet precipitate, not 
 so deep as the preceding ; the supernatant liquor remained 
 clear. 
 
 Sulphate of copper produced a violet deposite, which formed 
 slowly ; the supernatant liquor continued clear and violet. 
 
 If alcohol be digested on the extract which the decoction of 
 'cochineal yields by evaporation, the colouring particles dissolve, 
 leaving a residuum, which retains merely a colour of wine lees, 
 not removable by fresh alcohol. This portion affords, in the 
 analysis by fire, the products of animal substances. 
 
 The alcoholic tincture of cochineal leaves, on evaporation, a 
 transparent residuum of a deep red, which, when dry, has the 
 appearance of a resin. It yields also, by distillation, the pro- 
 ducts of animal substances. Hence the colouring matter is an 
 animal substance. 
 
 The cochineal mesteque was compared to the wild cochineal of 
 Mexico, and that reared in St. Domingo, and transmitted by 
 Bruley. 
 
 The decoction of the wild cochineal has the same hue as that of 
 the cochineal of St. Domingo. This shade borders more on the 
 crimson than that of the cochineal mesteque ; but the precipi- 
 tates that are obtained, whether by solution of tin or of alum, are 
 ^ of a colour perfectly equal to those of the mesteque cochineal ; 
 
346 
 
 BERTHOLLET ON DYEING. 
 
 and it is these precipitates which colour stuffs by combining with 
 them. ^ 
 
 Chlorine was had recourse to for determining the proportion 
 of the colouring particles which the decoctions of the different 
 cochineals contained. An equal weight of each of the three cochi- 
 neals was boiled for an hour, rendering all the circumstances as 
 equal as possible. These three decoctions being filtered, were 
 poured each into a graduated glass cylinder, and some of the 
 same chlorine was mixed with them, till they were all brought 
 to the same shade of yellow. The quantities of acid, which 
 represent the proportions of the colouring parts, were found to 
 be nearly in the ratios of the following numbers : eight for the 
 cochineal of St. Domingo ; eleven for the wild cochineal of 
 commerce ; eighteen for the mesteque cochineal. 
 
 We therefore perceive, that the cochineal of St. Domingo is 
 not only very inferior to the mesteque cochineal, but to even the 
 wild cochineal of Mexico ; and in fact it is much more cottony, 
 and smaller; but these disadvantages should not diminish the 
 zeal of those who are engaged in rearing it. 
 
 The observations of Thieri de Menonville have already proved, 
 that the wild cochineal lost its cotton, and became larger by a 
 succession of well nursed generations; and, at the beginning, 
 nopals which had not attained the requisite size, were necessarily 
 employed. 
 
 In reference to the quality of the colour, it has been seen that 
 the cochineal of St. Domingo did not yield to the mesteque 
 cochineal ; but if the cotton with which it is covered should, in 
 the operations on the great scale, injure the beauty of the scar- 
 let, whose lustre is so easily affected, a more advantageous em- 
 ployment could be found for it, either for half scarlets, or for 
 crimsons, and the other shades which are less delicate than that 
 most lively of colours. Wild cochineal is found in several parts 
 of North America; Dr. Garden observed it in South Carolina 
 and in Georgia. It exists also in Jamaica, and some might pos- 
 sibly be found equal to that of Mexico. Bancroft examined 
 some of it that came from the Brazils, and obtained a colour 
 equal in beauty to that of the mesteque cochineal. It yielded 
 half the quantity. 
 
 Anderson imagined, that he had found wild cochineal at Ma- 
 dras ; but the hopes which he excited have not been realized. 
 
OF RED. 
 
 347 
 
 The insect which he mistook for the cochineal, seems, according 
 to Bancroft, to approach to the kermes ; and the trials which he 
 made on a sample sent to him, showed" that this insect could 
 give stuffs only a chocolate brown colour, but one indeed very 
 durable. 
 
 A distinctive character may be observed between cochineal 
 and madder, in their mode of comporting themselves with re- 
 agents : both receive a yellow colour from the acids ; but if the 
 colouring particles of the cochineal be separated by a substance 
 that precipitates them from the acid liquor, they reappear with 
 their natural colour little changed ; whereas those of madder 
 retain a yellow or tawny hue. Hence the mordants which pos- 
 sess a redundant acid, such as the solution of tin, are employed 
 much more successfully with cochineal than with madder. This 
 effect is probably owing to the combination of the colouring part 
 of the madder with the oxyde of tin retaining a portion of 
 acid, while that of the colouring part of cochineal retains none, 
 or much less. (Note KK.) 
 
 Carmine is the lake obtained from cochineal, by means of 
 alum ; but with the cochineal is blended a certain proportion of 
 autour^ a bark which comes from the Levant, of a paler colour 
 than cinnamon. Chouan is also commonly added. It is a yel- 
 lowish-green seed of an unknown plant, which also comes from 
 the Levant. It would seem that these two substances furnish, 
 along with alum, a yellow precipitate, which serves to brighten 
 up the colour of the cochineal lake in the same way as a yellow 
 colouring matter serves to give scarlet a flame colour. A supe- 
 rior carmine is at present made by a process which is not pro- 
 mulgated. Carmine was formerly prepared with kermes, whence 
 it. takes its name. (Note LL.) 
 
 CHAPTER IV. 
 Of Dyeing Scarlet. 
 
 Scarlet is the most beautiful and the most brilliant colour 
 among dyes. Taste fluctuates with regard to the shade in de- 
 mand. Sometimes scarlet is sought for of a perfect and deeper 
 red ; more frequently inclining more or less to the colour of flame. 
 
348 
 
 BERTHOLLET ON DYEING. 
 
 We cannot expect to obtain the desired shade from the pre- 
 cise doses prescribed in the processes, from variations in the 
 quantity of the colouring particles contained in the different 
 kinds of fine cochineal, and particularly from the solutions of 
 tin thatt are used differing considerably from each other ; but the 
 just proportions of the ingredients to be employed may be 
 readily determined by trials in the small way, so as to obtain the 
 shade called for ; and if the pieces which are dyed be above or 
 below this shade, it is not difliicult to find the suitable pro- 
 portions. 
 
 The dyeing of scarlet is performed at two operations ; the first 
 is called the boiling (bouillon), the second the reddening. 
 
 For a boiling intended to dye 110 pounds of cloth, 6^ pounds 
 of tartar are thrown into water, a little more than lukewarm. 
 The bath is strongly raked up, and when it is a little hotter, 
 H pound of cochineal in powder is thrown in, and very well 
 mixed. An instant afterwards, 5^ pounds of a very clear solu- 
 tion of tin are poured in, which are carefully mingled; and 
 whenever the bath begins to boil, the cloth is introduced, and 
 made to circulate rapidly round for two or three turns ; the mo- 
 tion is then slackened. After two hours of ebullition, it is 
 lifted, aired, and carried to the river to be well washed. 
 
 For preparing the second bath, which is the reddening, the 
 boiler is emptied. When this bath of water is about to boil, 
 6 pounds of powdered and sifted cochineal are put into it. This 
 is mixed with care, and the stirring being over, when the crust, 
 which spontaneously forms on its surface, opens of itself in se- 
 veral places, about fifteen pounds of solution of tin are poured 
 in. If, after this, the bath rises above the edge of the boiler, it 
 is refreshed (cooled down) by putting in some cold water. 
 
 When the solution is well mixed through the bath, the cloth 
 is thrown in, with the precaution of whirling it rapidly for 
 the first two or three turns. It is boiled for an hour, pressing 
 it down into the bath with rods whenever the agitation raises it 
 up. It is now taken out, aired, cooled, then washed in the 
 river, and dried. ^ 
 
 The proportions of cochineal and solution of tin which enter 
 either into the bouillon or reddening, are not uniform. There 
 are dyers who, from Hellot's account, succeed very well by 
 putting two-thirds of the composition and one-fourth of the 
 
OP RED. 
 
 349 
 
 cochineal in the bouillon^ and the other third of the composition 
 and the three-fourths of the cochineal into the reddening. Hellot 
 asserts also, that it is not injurious to employ tartar in the red- 
 dening, provided no more of it be used than one-half the weight 
 of the cochineal ; and it appeared to him to render the colour 
 even more durable. This is actually the practice of some dyers. 
 It has been seen to promote the solution of the colouring parti- 
 cles, an effect w^hich particularly takes place w^hen it is ground 
 along w^ith the cochineal ; and by this means the residuum is 
 found to be better exhausted. This consideration has less 
 w^eight when the work is consecutive, because then the colouring 
 particles present in the residuum are employed in the subsequent 
 operations ; but it is proper not to neglect the influence of the 
 tartar on the quality of the colour, which we shall determine 
 more particularly. 
 
 There are some dyers who do not lift the cloth out of the 
 bouillon^ but only refresh this, in order to make the reddening 
 in the same bath, by pouring in the infusion of the cochineal pre- 
 pared by itself, and to which they have added the proper quan- 
 tity of the composition. Time and fuel are thereby saved, and 
 a good scarlet may be obtained. 
 
 As it is usually desired that the scarlet should have much 
 vivacity, approaching to a flame colour, a yellowish tint is given 
 it, by boiling fustet in the first bath, or indeed by adding a little 
 curcuma to the cochineal. The employment of these ingredi- 
 ents may be discovered on cutting the scarlet cloth, its interior 
 being in this case dyed yellow ; for, by the ordinary process, the 
 cochineal does not penetrate into the inside of the scarlet, but 
 leaves it white, when it is said to cut. 
 
 In the scarlet dye, it is advantageous to use a boiler of tin, 
 because the acid employed attacks copper, whose solution might 
 injure the beauty of the colour. However, as these boilers are 
 difiicult to make of a certain size, and as they are liable to be 
 melted, if the fire be not withdrawn before they are emptied, 
 several dyers use copper boilers. But care must be taken to 
 keep them very clean, not to let the acid liquor remain in them, 
 and to prevent the cloth touching the metal, either by means of 
 a network, or an open wicker-work basket.* 
 
 * A piece of tin lying in the boiler, and in contact with it, will render the copper 
 negatively electrical, and thus prevent the copper from being attacked. — T. 
 
350 
 
 BERTHOLLET ON DYEING. 
 
 Scheffer prescribes for the bouillon^ one part of solution of 
 tin, for ten parts by weight of cloth, with an equal quantity of 
 starch and tartar as of solution. He remarks, that the starch 
 tends to make the colour more uniform, and he recommends to 
 throw into the water, when it boils, l-128th of cochineal; to 
 agitate well ; to let the wool boil in it for an hour, and then to 
 .wash it. He prescribes next, the boiling for half-an-hour in the 
 bath, which serves for the reddening, with l-32d of starch? 
 l-24th of solution of tin, l-32d of tartar, and 1-1 8th of cochi- 
 neal. 
 
 It appears, that Scheffer employs a much smaller quantity ' 
 of solution of tin than Hellot ; but what he does employ con- 
 tains much more tin. 
 
 Poerner describes three principal processes, according as the 
 shade is to be more or less deep, or more or less of an orange 
 hue, which he wishes to give to the scarlet. He varies the pro- 
 portions of the solution of tin, of cochineal, and tartar, or omits 
 the last ingredient. 
 
 For conducting the process of the scarlet dye in the most 
 beneficial manner, and for varying its results, according to the 
 end in view, the effect of each of the ingredients employed in it 
 must be ascertained. 
 
 In the first edition of these Elements, the property of giving 
 a deeper and more rosy hue to the colouring particles of the 
 cochineal had been attributed to the tartar. This opinion might 
 be regarded even as the general one ; but Bancroft has justly 
 called it in question. He states that if the tartar be left out, 
 the colour is a crimson ; that the tartar gives rise to an insoluble 
 tartrate of tin, which forms with cochineal a yellow colour; 
 that the ordinary scarlet is a mixture of one-fourth of this yellow 
 colour, and three-fourths, or a little more, of the crimson colour, 
 which cochineal gives with the solution of tin. Consequently, 
 he proposes to substitute for the tartar, a preliminary dye, with 
 quercitron, which, by its yellow, produces the same effect, and to 
 dye afterwards with solution of tin and cochineal, of which, in 
 this case, no more than four-fifths of the ordinary proportion 
 are required. 
 
 We have dyed scarlet, by employing the proportions of solutions 
 of tin and tartar which have been pointed out, in the first place ; in 
 another pattern, we doubled the proportions of tartar ; and in a 
 
OF RED. 
 
 351 
 
 third, we left out this ingredient. The first took a beautiful 
 scarlet colour ; the second inclined more to yellow ; and the third 
 had a vinous colour, and was less lively, although not exactly 
 crimson. 
 
 It is true, therefore, that tartar causes the colour of cochineal 
 to incline to yellow, and that it produces more of this effect, the 
 greater its proportion. We have not determined, whether this 
 effect may be entirely supplied by a yellow produced by other 
 means. If the proportion of the solution of tin is too great, it 
 becomes prejudicial, and impoverishes the colour, because a por- 
 tion of the colouring matter is retained in solution. But the 
 different proportions of tin which this solution contains have 
 also some influence. It has appeared to us, in general, that the 
 larger the proportion of tin, the deeper was the colour. We 
 have been sufficiently diffuse on the preparation of the solution 
 of tin. Part I., Section V. 
 
 Bancroft recommends a solution of one part of tin, made in a 
 mixture of a little more than two parts of sulphuric acid, and of 
 three of muriatic. He relates several other attempts which he 
 has made, both by dissolving tin in different acids, and by sub- 
 stituting other salts of an earthy and metallic base for the solu- 
 tion of tin. But these attempts do not point out applications 
 sufficiently useful to the art for us to detail their results. 
 
 Experience shows, that scarlet may be dyed by a single ope- 
 ration ; but an uniform dye is better ensured by dividing it into 
 two operations, when the dyeing is on the large scale. This is not 
 the case with the lighter shades. 
 
 If the scarlet just dyed be too much of an orange cast, this 
 may be weakened by washing it in hot water, especially if the 
 water contains some salt with an earthy base. 
 
 The reddening (bath) which has served for dyeing the scarlet, 
 is not exhausted of its colouring particles, but contains still a 
 quantity, which varies, in proportion as the cochineal has been 
 reduced to a powder of greater or less fineness, and according 
 to the length of ebullition which it has suffered. This bath 
 contains, moreover, a portion of the mordants put into it ; but 
 as the nature of this residuum is not uniform, it would be illu- 
 sory to prescribe the precise doses of the ingredients that should 
 be added for obtaining the shades that may be sought from it. 
 Practice in the same process, and experience, easily guide an 
 
352 
 
 BERTHOLLRT ON DYEING. 
 
 intelligent dyer. We shall therefore confine ourselves to some 
 general considerations. 
 
 If much cloth is to be dyed scarlet, we may use for the 
 bouillon a reddening which has been just employed for dyeing, 
 subtracting from the ordinary quantity of cochineal what may 
 be supposed to remain in the bath^ and diminishing likewise the 
 amount of solution of tin. But if a flame colour be wanted, 
 we should begin by boiling a bag of fustet, withdrawing it 
 before we add the other ingredients. 
 
 This bath may then be used, as soon as the cloth is taken out, 
 for making pomegranate colour, by boiling a bag of fustet in it. 
 That (the fustet) which has already passed through a bath, is 
 fitter for this shade than what is fresh. After withdrawing it, 
 some tartar and composition are thrown into the bath. It is to 
 be well stirred with the rake, and the cloth must be treated as 
 for the scarlet dye. 
 
 In the sequel of this colour the bath may serve for capuchin 
 colours, {les capucines,) by boiling fustet in it, with the addition 
 of tartar, and solution of tin. 
 
 The preceding houillon may likewise be used for lobster- 
 red, orange, gooseberry, golden, and jonquille colours, by boiling 
 fustet in it, adding a little cochineal, and more or less solution 
 of tin and tartar. 
 
 When the houillon has been given to all the cloths that are to be 
 dyed, proceeding from the deepest to the lightest colour, they 
 are passed through the reddening ^ advancing, contrariwise, from 
 the lightest to the deepest colour, adding always more and more 
 cochineal and solution of tin, till the pomegranate and flame 
 colours be attained. When it is come to the turn of the golden 
 and jonquille hues, fustet is added, unless these colours have 
 been finished in the first bath, as we shall see may be done for 
 certain shades. For gold and gooseberry colour, a little madder 
 is added. 
 
 The colours of gold, gooseberry, jonquille, and chamois, m,ay 
 be made after the scarlet houillon^ by adding for the first two, 
 fustet, solution of tin, and a little madder ; and a little more 
 fustet, and a little less solution of tin, for the gold colour than 
 for the gooseberry. Much less solution of tin is needed for the 
 chamois (buff*). Hind colour {couleur de biche) may be made in 
 the sequel of a scarlet bouillon without any addition. The coffee 
 
OF RED. 
 
 853 
 
 with milk colour {cafe au lait) requires a little fustet and solu- 
 tion of tin, with a very small quantity of madder. To the last 
 ingredients, a little cochineal and tartar are added for the cho- 
 colate with milk colour. 
 
 A fresh bath is usually had recourse to for the bouillon of the 
 cherry colours ; and it is composed of tartar and solution of tin. 
 For dyeing them, thereafter, a reddening is employed which has 
 served for scarlet, adding to it tartar, solution of tin, and a little 
 cochineal. For the houillon and the reddening only half the 
 time is taken that is employed in the operations for the scarlet 
 dye ; and, in general, the time is shortened in proportion to the 
 delicacy of the shades. For the houillon of rose, the cherry 
 reddening may be used ; and its reddening is composed of a small 
 quantity of solution of tin, tartar, and very little cochineal. 
 The colour may be deepened, by passing the cloth through hot 
 water on its coming out of the bath. 
 
 Flesh colour is made in the sequel of a reddening, by throw- 
 ing away a little of the bath, and refreshing it with cold water. 
 It may likewise be made in the sequel of the violets, by adding 
 a little solution of tin. The boiling must continue but a very 
 short time. 
 
 Lastly, the reddening from which the scarlet cloth has been 
 withdrawn may serve for the greys that are to have a vinous 
 cast, by refreshing the bath, adding to it gall-nuts, and then 
 a little sulphate of iron, or green vitriol. 
 
 It must be observed, that the weak and delicate shades, such 
 as the pinks and the oranges, as well as the lilacs, mallows, 
 cherries, roses, have more lustre and freshness when they are 
 prepared in a single bath, than when they are subjected to both 
 the houillon and the reddening. On this account it is sufficient 
 to introduce into this bath the necessary ingredients. The 
 cloth, when merely moistened, and unimpregnated with mor- 
 dant, becomes charged with the colouring particles less readily, 
 but in a more evenly manner. There is also in this mode of 
 operating a saving of time and fuel. 
 
 2 A 
 
354 
 
 BERTHOLLET ON DYEING. 
 
 CHAPTER V. 
 Of the Crimson Dye. 
 
 All the processes employed for obtaining the different shades 
 of crimson, from the lightest to the deepest, may be referred to 
 two. The desired crimson hue is given either to cloth already 
 dyed scarlet, or the crimson is given at first. 
 
 Alum, the salts in general v^ith earthy base, the fixed alkalies 
 and the volatile, possess the property of changing the colour of 
 scarlet into crimson, which is the natural colour of cochineal. 
 The cloth dyed scarlet has only to be boiled, therefore, during 
 about an hour, in a solution more or less charged with alum, 
 according as a deeper or lighter crimson is wanted ; but as the 
 other salts with earthy base have the same property, and as 
 common waters contain more or less of these salts, it happens 
 that they rose to a greater or smaller degree the scarlet shades 
 passed through them, especially when they are heated. The 
 quantity of alum necessary to obtain the crimson varies accord- 
 ing to the nature of the waters employed ; and when they are 
 well charged with these salts, they may even suffice without the 
 addition of alum. When a piece of scarlet has any defects, it 
 is set apart for crimson. 
 
 Hellot says that he has tried soap, soda, potash, and the cen- 
 dres gravelees (crude potash) ; that all these substances pro- 
 duced the crimson wanted, but that they deadened it, or gave it 
 less lustre than alum. Ammonia, on the contrary, produces 
 a very good effect ; but as it evaporated speedily, a considerable 
 quantity of it had to be put into the bath, which increased the 
 price of the dye. He therefore thought of putting into the 
 bath, somewhat more than tepid, a little muriate of ammonia, 
 or sal ammoniac, and an equal quantity of common potash. 
 The cloth assumed immediately a very rosy and very brilliant 
 colour. He even thinks, that by this means, which heightens 
 the colour, the quantity of the cochineal may be somewhat dimi- 
 nished. Poerner, who gives this very process, prescribes the 
 leaving the scarlet for 24 hours in the cold solution of the am- 
 moniacal muriate and potash. 
 
OF RED. 
 
 355 
 
 To dye crimson directly, a solution of 5 ounces of alum, and 
 3 ounces of tartar, with 2 ounces of cochineal, are made use of 
 in the bouillon for every 2 pounds 3 ounces of cloth ; but solu- 
 tion of tin is commonly added, although in smaller proportion 
 than for scarlet. The processes that are pursued vary much, 
 according to the depth of the shade desired, or as it is more or 
 less removed from the colour of scarlet. Some persons make 
 use of the muriate of soda for the bouillon. 
 
 Archil and potash are often employed to brov^n crimsons, and 
 give them more lustre; but this showy lustre {bloom) soon 
 vanishes. 
 
 The bouillon for the crimson is made sometimes in the sequel 
 of the reddening bath of scarlet, by adding to it tartar and alum ; 
 and it is asserted, that even the soupe au vin, (literally, wine- 
 soup colour,) of which both the bouillon and the reddening are 
 made in the sequel of scarlet, has more lustre than when it is 
 formed from a fresh bath. For these colours, the wild cochineal 
 may be substituted for the fine ; but as it contains fewer colour- 
 ing particles, its quantity must be augmented. 
 
 The reddening which has served for crimson may be employed 
 for purples, and other compound colours, of which we shall treat 
 hereafter. 
 
 Half scarlets and half crimsons, (half grain scarlets,) are made • 
 by replacing the half of the cochineal with madder, giving, 
 moreover, the same bouillon as for scarlet, and following, as to 
 the rest, the process of the reddening of scarlet or crimson. 
 Instead of a half, other proportions of madder may be employed, 
 according to the effect wanted. More lustre is also given to the 
 ordinary madder red, by forming its bouillon in the sequel of the 
 reddening of scarlet. 
 
 On silk, the fine crimson due to cochineal is distinguished 
 from the false crimson obtained from brazil wood. 
 
 Silks intended to be dyed cochineal crimson, should be boiled 
 only at the rate of 20 parts of soap for 100 of silk, because the 
 slightest yellow cast which remains on the silk, when it is scoured 
 only to this degree, is favourable to this colour. 
 
 Silks well cleansed in the river, are put into an aluming of the 
 greatest possible strength; there they are usually left from the 
 evening till next morning, after which they are washed and 
 subjected to two beetlings in the river. 
 
 2 a2 
 
356 
 
 T5ERTII0LLET ON DYEING. 
 
 For preparing the bath^ an oblong boiler is filled with water, 
 to about one-half or two-thirds; and when this water boils, 
 pounded white nut-galls are thrown in to about a 6th or an 8th 
 of the weight of the silk ; and after boiling a few seconds, there 
 is put into the bath bruised and sifted cochineal, from an eighth 
 to a fifth for each quantity of silk, according to the shade that is 
 wanted. To the bath is afterwards added a sixteenth of tartar 
 for one part of cochineal, and, w^hen the tartar is dissolved, as 
 much solution of tin. This solution should contain much more 
 tin than that made use of for scarlet, otherwise the colour 
 would be too bright. Macquer directs it to be made with six- 
 teen parts of nitric acid, two of ammoniacal. muriate, as much 
 fine grain tin, and twelve of water. 
 
 The ingredients are mingled, and the boiler is filled up with 
 cold water ; the proportion of the bath being about 4 or 4^ 
 gallons of water for every 2 pounds three ounces of silk. The 
 silks are immediately plunged, turning them round the skein 
 sticks till they appear very uniform. The fire is then increased, 
 and the bath is kept boiling for two hours, turning round the 
 silks from time to time ; after which the fire is withdraw^n, and 
 the silks are plunged into the bath. Here they are kept for 
 some hours. They are then washed in the river, giving them 
 two beetlings, when they are wrung and dried. 
 
 If it be wished to brown the crimsons, they are passed, after 
 washing them, through a solution more or less charged with 
 sulphate of iron,^ according to the shade wanted. If the silk is 
 to retain a shade of yellow, more or less of the decoction of the 
 fustet wood is added to this solution. 
 
 White gall-nuts are preferable, because black ones deaden the 
 colour of crimson ; and if even too large a quantity of the 
 former be introduced, the colour becomes duller. Macquer says 
 that the galls serve merely to increase the weight of the silk ; 
 their general effect, however, is to render the colours more 
 durable. They are indispensable, at least for the crimsons 
 intended to be browned, '(saddened.) 
 
 The test of vinegar, often used for distinguishing the cochi- 
 neal crimson from the spurious, is deceitful, because it cannot 
 distinguish the colours obtained from (brazil) wood, when they 
 are fixed by means of the solution of tin ; for in this case they 
 resist the vinegar as well as those made with cochineal. 
 
OF RED. 
 
 357 
 
 Macquer gives the description of the crimson silk dye of 
 Damascus and Diarbekir, which was communicated by Granger ; 
 as also of the process followed at Genoa. 
 
 We have seen that a very small quantity of solution of tin 
 was put into the bath for dyeing silk crimson. Were it wished 
 to employ the same process by which wool is dyed scarlet, tlie 
 silk would lose its lustre, (bloom,) and acquire but a faint colour ; 
 but Macquer and SchefFer have both published a process, differ- 
 ing only in some circumstances, for dyeing silk rose and po7iceau, 
 (deep red,) by means of solution of tin, employed cold, in order 
 to avoid its too lively action on the silk. 
 
 In the process which Macquer published in 1768, the solution 
 of tin is prepared by throwing three parts of tin very gradually 
 into a mixture of four parts of nitric acid, and two of muriatic. 
 When the solution is finished, six parts of silk are introduced, 
 which has had previously a bath of anno t to ; there it is left for 
 half-an-hour, when it is wrung out and washed, till the water 
 ceases to be foul. For dyeing one pound of silk, l-4th of 
 cochineal, with 1-I6tli of tartar is employed. The liquor is 
 made to boil ; it is diluted with cold water, so that the hand can 
 bear its heat : into this the silk is immersed, the fire is raised, 
 and after a minute's ebullition it is taken out and washed. The 
 silk receives, by this process, an augmentation of weight amount- 
 ing to a fourth ; its colour resists soap, and is much more dura- 
 ble than that given by carthamus, (safflower.) 
 
 In 1751, Scheffer published in Swedish the fallowing process. 
 One part of tin is dissolved in four parts of nitric acid, and one 
 of muriate of soda ; and the solution is diluted with a double 
 quantity of water. In this the silk is left to macerate for 24 
 hours ; when it is taken out and washed in clear water till this 
 is no longer milky. The silk is then dyed, by boiling it for a 
 quarter-of-an-hour with 5-6ths of its weight of cochineal, in a 
 bath not much diluted : the remaining liquor contains still a 
 good deal of colouring matter, v/hich may serve to dye silk of a 
 lighter shade, or indeed to dye it crimson by the ordinary pro- 
 cess ; it may serve likewise for wool. 
 
 Scheffer describes some variations of his process for obtaining 
 different shades, of which we shall now recapitulate the principal. 
 On wringing silk out of the solution of tin, letting it lie all 
 night in a cold solution of one part of alum to thirty-two of 
 
358 
 
 BERTHOLLET ON DYEING. 
 
 water, wringing it in order that it may be dried, washing it, and 
 then passing it through a bath of cochineal, it takes merely a 
 pale poppy-red colour. If after diluting one part of solution of 
 tin with eight parts of water, the silk be set to macerate in it 
 for \2 hours ; be afterwards kept all the night in the solution of 
 alum ; be then washed, dried, and passed through two baths of 
 cochineal as above, adding to the second bath a little sulphuric 
 acid, a beautiful poppy-red will be obtained. 
 
 The chief difference between the processes of Macquer and 
 Scheffer, consists in the yellow ground which Macquer gives the 
 silk. Scheffer employs a larger proportion of cochineal in the 
 dyeing bath ; but, from the report of the very persons who co- 
 operated at Macquer's experiments in the manufactory of the 
 Gobelins, it must be acknowledged, that the silk dyed by his 
 process had never reached the scarlet hue. This colour, so 
 much desired, has, however, induced dyers to multiply their 
 attempts. Those who appear to have approached nearest to 
 their object, begin by dyeing the silk crimson ; they then cover 
 this dye with that of carthamus, by the process hereafter de- 
 scribed; and they give it finally a yellow dye in the cold. Thereby 
 a beautiful colour is obtained. But the carthamus dye is de- 
 stroyed by the action of the air, and the colour grows pretty 
 speedily brown. 
 
 Cochineal is little used for dyeing cotton and linen, because a 
 beautiful and permanent red can be given, them by means of 
 madder. Scheffer, however, describes a process which may be 
 tried. The linen or cotton is steeped for 24} hours in a cold 
 solution of tin ; after which it is wrung, washed, and made to 
 boil for a quarter-of-an-hour with 4-6ths its weight of cochineal. 
 The cotton takes a light red. These colours bear the action of 
 the sun, but not of soap. Berkenhout also gave, in England, a 
 process, which, by Bancroft's description, differs little from that 
 which we have given for silk ; but it is said to produce merely a 
 crimson, because there is no yellow in it. 
 
 The difference between the processes to which recourse must 
 be had for giving silk and cotton the colour of scarlet, appears 
 to depend on these substances having a much smaller disposition 
 to unite with the colouring matter of cochineal, or with the 
 combination of this colouring matter and tin ; whence it results, 
 that this combination separates, reunites in two considerable 
 
OF RED. 
 
 359 
 
 masses, and precipitates before its union can be effected with the 
 stuff. But this inconvenience is obviated by first impregnating 
 the stuff with solution of tin, because the oxyde of tin, being 
 combined with it, the colouring molecules of the cochineal come 
 and fix themselves in it, in which case this compound can no 
 more be precipitated. It therefore appears to us, that, in order 
 to succeed in this process, our views must be directed towards 
 the fittest means for producing, at first, a combination of the 
 oxyde of tin with the stuff, without altering the latter ; and then 
 to give it a due alloy of the red of cochineal, and of yellow, 
 either by the means of tartar, or by the admixture of a yellow 
 colour. 
 
 CHAPTER VL 
 Of Kermes. 
 
 The kermes, {coccus ilicis, Linn.,) is an insect, found in several 
 parts of Asia and the South of Europe. It was known to the 
 ancients by the name of coccum squarlatinum, coccus haficus^ 
 infectorius, granum tinctorium. That collected in Galatia and 
 Armenia was preferred ; at the present day it is gathered chiefly 
 in Languedoc, Spain, and Portugal. 
 
 The kermes lives on a small oak, {quercus coccifera, Linn.) 
 The females grow big, {massives,) and finally remain motionless, 
 when they have nearly the form and size of a pea, and are of a 
 reddish-brown colour. Their shape caused them to be long mis- 
 taken for the seeds of the tree on which they live ; whence they 
 were called grains of kermes. They have been also called ver- 
 milion. 
 
 The first person who spoke of them with tolerable accuracy, 
 was Pierre de Quiqueran, bishop of Senez, in 1550, de laudibus 
 provincice. 
 
 The history of this insect is found in a memoir of Nissole, 
 Acad, des sciences," 1714; and particularly in Reaumur's 
 Memoires pour servir a I'histoire des insectes," tom. iv. 
 
 It is thought that the kermes takes its name from an Arabic 
 
360 
 
 BERTHOLLET ON DYEING. 
 
 word, which signifies a little worm, vermiculus, from which 
 comes the name vermilion also given it. Astruc derives the 
 term from two Celtic words, of which one signifies oak, and the 
 other acorn. Memoire pour servir a I'histoire naturelle de 
 Languedoc." 
 
 The kermes is fixed to the bark of the shrub by a white 
 cottony down, furnished by the insect. Chaptal has observed 
 that this down, as well as that which all the insects of this kind 
 afford, has several of the characters of caoutchouc ; that it was 
 insoluble in alcohol, that it melted at the heat of boiling water, 
 and burned with flame on red-hot cinders. To him we owe the 
 following description of the method pursued at Languedoc to 
 make the harvest of kermes. 
 
 Towards the middle of the month of May, they begin to 
 gather the kermes, which has then acquired its ordinary size ; 
 it resembles in its colour and form a little sloe. This harvest usu- 
 ally lasts till the middle of the month of June, and sometimes 
 longer, if the great heats be retarded, or if violent rains do not 
 come on ; for one storm of rain is sufficient to put an end to the 
 crop for a year. Women are commonly employed in this har- 
 vest. They go out early in the morning with a lantern in their 
 hands, and a glazed earthen pot, and thus proceed before day- 
 break to detach the kermes from the branches with their fingers. 
 This time is the most favourable ; 1st. because the leaves which 
 are furnished with prickles give them less annoyance, being- 
 softened by the morning dew ; 2d, because the kermes weighs 
 more, either from its not being dried by the sun, or from fewer 
 young ones making their escape, which are hatched by the heat. 
 Persons are, however, to be seen sufficiently intrepid to gather 
 it during the day-time, but this is rare. 
 
 One individual can gather from one to two pounds in a day. 
 
 In the first season of the harvest, the kermes weighs more ; 
 hence it sells for less than towards the conclusion, when it is 
 drier and lighter. 
 
 The price of fresh kermes varies, moreover, according to 
 the demand of purchasers and its scarceness. It commonly 
 fetches from 15 to 20 sous (halfpennies) per pound at the com- 
 mencement, and from 30 to 40 towards the conclusion of the 
 harvest. 
 
 *^ Those who purchase it are obliged as soon as possible to put 
 
OF RED. 
 
 361 
 
 a stop to the development of the eggs, so as to prevent the 
 escape of the young contained in the coque. This coque (shell) 
 is merely the body of the mother, which has enlarged by the 
 formation of the eggs. The female has no v^ings. It fixes and 
 takes up its abode on a leaf. The male comes to impregnate 
 her, and she then enlarges merely by the development of the 
 eggs. In order to kill the young contained in the eggs, the 
 kermes is steeped in vinegar for 10 or 12 hours, or it is exposed 
 to the fumes of vinegar, which takes less time, for half an hour 
 is enough. It is then dried on cloths. This operation gives 
 it a wine-red colour," 
 
 When the living insect is crushed it affords a red colour. It 
 has a pretty agreeable smell, and a taste somewhat bitter, harsh, 
 and pungent ; when dry it communicates the same odour and 
 taste to water and alcohol, which thereby acquire a deep red 
 colour. The extract procured from its infusion retains this 
 colour. (Note MM.) 
 
 To dye spun worsted with kermes, it is first boiled in water 
 along with bran for half an hour ; next for two hours in a fresh 
 bath, with a fifth of its weight of Roman alum, and a tenth of 
 tartar. Sour water is usually added to it. It is taken out after 
 this ebullition and enclosed in a bag, which is carried to a cool 
 place, and left there for some days. To form a saturated colour, 
 there is put into a tepid bath three-fourths of kermes, or even 
 a weight equal to that of the wool introduced into the bath at 
 the first bouillon. As the density of cloth is more considerable 
 than of spun worsted or wool in the fleece, it requires a fourth 
 less salts in the bouillon, and of kermes in the bath. With 
 smaller proportions of kermes, lighter and paler colours are 
 obtained. When a series of shades is to be made, it is neces- 
 sary to begin, as usual, with the deepest. 
 
 Hellot directs us to throw into the boiler containing the kermes 
 a small handful of the refuse wool, (or cot,) before immersing 
 what is to be dyed in it, and to let it boil there for an instant. 
 It removes a species of black fecula, and the wool dipped after- 
 wards assumes a finer colour. 
 
 Before carrying the newly dyed wool to the river, it may be 
 passed through a water bath slightly tepid, in which a small 
 quantity of soap has been dissolved. The colour thus takes 
 some lustre, but it is a little rosed, that is to say, it gets a cast 
 bordering on crimson. 
 
362 
 
 BERTHOLLET ON DYEING. 
 
 By employing kermes with tartar, without alum, and as much 
 solution of tin as for cochineal scarlet, Hellot has procured from 
 a single bath an extremely lively cinnamon. The cloth having 
 been macerated in a solution of sulphate of potash, it took with 
 the kermes an agate-grey colour of considerable beauty and 
 solidity ; after maceration with sulphate of soda, a dirty grey of 
 little permanence ; with sulphate of iron and tartar, a fine grey ; 
 with tartar and sulphate of copper, an olive colour, and the 
 same with nitrate of copper. The solution of bismuth, poured 
 drop by drop into the kermes bath, produced a violet. All the 
 acids turn it into a cinnamon bordering more or less on red, 
 according as the acids are weaker, or in smaller quantity. The 
 alkalies rose the colour, and render it dull. 
 
 The red colour which kermes communicates to wool, has much 
 less lustre than the scarlet made with cochineal, which came to 
 be preferred as soon as the art of heightening the peculiar colour 
 of cochineal by means of the solution of tin became known ; but 
 the former has much more permanence, and spots of grease can 
 be effaced from it without its colour being affected. It is the 
 blood-red, preserved without alteration in the old tapestries. To 
 the scarlet of kermes, the name of grain scarlet was given, be- 
 cause this insect was mistaken for a seed, {graine.) They gave 
 it likewise the name of scarlet of Venice, because its principal 
 manufactory was in that city. 
 
 The solution of tin was not omitted to be employed for kermes, 
 as well as for cochineal ; and Scheffer describes several processes 
 for dyeing by this method with kermes; but its colour then 
 verges on yellow or cinnamon, because the combination formed 
 with the colouring matter and oxyde of tin retains from the 
 impression of the acid a yellow colour, as happens to the colour- 
 ing matter of madder. 
 
 The durability of the colour of kermes has often excited 
 a regret that our dyers should have abandoned its use, for they 
 employ very little of it at present. Some mixed a small quan- 
 tity of it with the cochineal. It is observed, that this mixture 
 contributed to give body to the colour, but it dimmed its lustre. 
 The greater part of the kermes comes from the Levant. 
 
 Only a dull reddish colour has been hitherto given to silk, by 
 means of kermes. 
 
 The scarlet, for which one-half of kermes and one-half madder 
 
OF RED. 
 
 363 
 
 are employed, is called half grain. This mixture gives a very 
 permanent colour, but not lively, bordering a little on blood 
 colour. It is said that the turbans fabricated for the Levant, are 
 dyed in this way at Orleans. A little brazil wood is probably 
 added. 
 
 The coccus polonicus is a small round insect, found adhering 
 to the roots of a species of polygonum, {sclerantus perennis,) It 
 is collected towards the end of June, in some provinces of Poland. 
 It appears to have properties similar to those of the kermes; 
 but no use is made of it in Europe. It is sold to the Turkish 
 and Armenian merchants. It is used in Turkey for dyeing wool, 
 silk, and horse-hair ; and women employ it for dyeing their nails. 
 
 There are several other insects which might equally afford 
 a red colour ; some even have been employed ; but the advan- 
 tages presented by cochineal have made their use be abandoned 
 or neglected. 
 
 CHAPTER VII. 
 Of Lac, or Gum Lac, 
 
 Lac is a substance of a more or less deep red colour, which is 
 brought to us from India, under different forms. This substance 
 is a production analogous to that of bee-hives, constructed by a 
 species of coccus, which Kerr and Roxburgh have described.* 
 It lives, and forms cells, on different species of shrubs. Geoffroy, 
 who has given some interesting observations concerning this sub- 
 stance,'!' regards it as a true wax, which owes its colour only to 
 the embryos of insects that have formed alveoli; (little holes in it 
 of a nearly round form ;) hence the name of gum is improper. 
 
 Several species of lac are distinguished, the principal being, 
 L Stick lac, the production which the ants have constructed 
 round small branches. This species is the richest in colour, 
 through there is some of it in Madagascar nearly colourless. 
 
 2. Grain, or seed lac. It is less coloured than the preceding. 
 
 3. Lac in tables (shell lac). It is imported in small plates of 
 
 * Pliilos. Trans. 1781, 17.91. f Mem. dc racademic. 1714. 
 
 « 
 
364 
 
 BERTHOLLET ON DYEING. 
 
 variable size and transparency. It has usually a dirty colour, 
 and is mixed with some wood and earth. It would seem that 
 the Indians have already extracted the colouring matter from it. 
 These two latter kinds are employed for sealing wax; colour- 
 ing them with minium (or vermilion) for red wax ; with lamp- 
 black for black wax ; with orpiment for the wax of an aven- 
 turine colour, &c. Geoffroy says, that the lac, separated from 
 the small bodies that it contains, afforded him, on distillation, 
 the same products as wax ; and that the small bodies, which may 
 be ground into a fine red powder, afforded him the products of 
 animal substances. The colouring particles, which are owing to 
 these small bodies, which he takes for chrysalids, dissolve in 
 water and alcohol, giving these liquids a fine red colour. 
 (Note NN.) 
 
 For dyeing, stick lac must be chosen of the deepest colour. 
 It is freed from the twigs, and reduced to powder. 
 
 The colour obtained from lac has not the lustre of the scarlet 
 made with cochineal, but it has the advantage of possessing more 
 permanence. It may be used profitably by mixing a certain 
 quantity of it with cochineal ; and if too great a proportion be 
 not taken, the scarlet is no less beautiful, and it is more durable. 
 
 In order to separate the portion soluble in water, and to esti- 
 mate its proportion to the wax or resin, Hellot was accustomed 
 to extract it by means of water and mucilage of comfrey, to 
 throw down its colouring matter with alum, to collect and dry it. 
 He obtained by this process a precipitate which formed one- 
 fifth of the weight of the lac, and it was this precipitate which 
 he used for dyeing. But this precipitate is a combination of 
 the colouring particles with alumina, or the base of alum. 
 
 Lac may be employed in a simpler manner : the only precau- 
 tion is to boil the cochineal and the solution of tin for the proper 
 time ; after which the bath is refreshed, and the lac in powder is 
 introduced. It requires a very moderate heat, otherwise it 
 dyes in an unevenly manner, and also a still more considerable 
 quantity of the tin solution than cochineal. The cloth should 
 be washed very hot on coming out of the boiler, because the 
 resinous particles attached 'o it are difficult to separate when 
 cold. Lac may be employed with success for the soupe au via 
 colour, by putting it in the bouillon; into which, in this case, no 
 alum must enter, because it would precipitate the colouring 
 
or Rl^D. 
 
 365 
 
 matter too rapidly. Cochineal is used in the reddening bath, and 
 it is saddened in the ordinary way. 
 
 According to Hellot, fixed alkali, or lime water, changes the 
 lively red produced by lac into a wine-lees colour ; and sal-am- 
 moniac affords cinnamon, or bright chestnut colours, according 
 as there is more or less salt. 
 
 Geoffroy conjectures, that lac is used for dyeing red morocco 
 leather in the Levant, after being subjected to suitable prepara- 
 tions. In fact, lac appears to be employed along with cochineal 
 for this purpose at Diarbekir ; and at Nicosie kermes is used. 
 Quemiset says, that kermes, cochineal, or lac, may be employed 
 indifferently.* 
 
 An advantageous distinction of lac over kermes appears to be, 
 its bearing the action of solution of tin, and experiencing its 
 good effects, without having its colour changed to yellow; and 
 we have seen, that it requries even a larger proportion of it than 
 cochineal does. 
 
 CHAPTER Vni. 
 Of Archil 
 
 The archil used in dyeing, is in the form of a violet-red paste. 
 Two kinds of it are chiefly distinguished, the archil plant of the 
 Canaries, and the ground archil, {de terre), or that of Auvergne, 
 called also perelle. The first is by far the most esteemed. It 
 is prepared from a specie^ of lichen {lichen roccelld) which grows 
 on rocks adjoining the sea, in the Canary and Cape de Verd 
 Islands. The second species is prepared from a lichen [lichen 
 parellus) which grows on the rocks of Auvergne. 
 
 Micheli, as quoted by Hellot, says, that the workmen who 
 prepare the archil at Florence, reduce the plant to a fine powder, 
 w^hich they pass through a sieve ; that they then sprinkle it 
 gently with stale urine ; that they stir the mixture once a day, 
 adding to it each time a certain proportion of soda in powder, 
 till the materials have assumed a columbine (dove) colour. The 
 
 * KArt d'appretcr et de teindre toutes sortes de peaiix. 
 
366 
 
 BERTHOLLET ON DYEING. 
 
 substance is now put into a wooden cask, and urine is added to 
 it, or lime water, or solution of gypsum, till its surface be 
 covered, in which state it is preserved. In a description to be 
 found in the work of Plictho, sal ammoniac, sal gem, and salt- 
 petre are added to this preparation ; but Hellot convinced him- 
 self by experiments, that lime and urine were the sole ingre- 
 dients necessary; and that it was requisite to stir up the mixture 
 frequently, adding at the same time new doses of lime and urine. 
 It is proper to let the volatile alkali, which is formed, evaporate 
 at the end of the process, in order that the archil may assume 
 the odour of violets, which characterizes the well-prepared ar- 
 ticle. To preserve it long, however, it must be kept moistened 
 with urine. 
 
 Kalm says, in an appendix to a Memoir of Linnaeus, in the 
 Stockholm Transactions for 1745, that in some parts of Sweden 
 two lichens, which he describes, are used for dyeing red. In the 
 same Transactions for 1744, there is said to be found, likewise 
 in Sweden, a species of lichen, {lichen foliaceus umbilicatus sub- 
 tus lacunosus, Linn, Flor. Suec.,) which, being prepared with 
 urine, dyes wool and silk of a beautiful and permanent red or 
 violet. 
 
 There are several other species of moss and lichen which 
 might be employed in dyeing, were they prepared like the archil. 
 Hellot gives the following method for discovering if they possess 
 this property. A little of the plant is to be put into a glass 
 vessel ; it is moistened with ammonia and lime water in equal 
 parts; a little muriate of ammonia (sal ammoniac) is added; and 
 the small vessel is corked. If the plant be of a nature to afford 
 red, after three or four days, the small portion of liquid, which 
 will run off on inclining the vessel, now opened, will be tinged 
 of a crimson red, and the plant itself will have assumed this 
 colour. If the liquor or the plant does not take this colour, 
 nothing need be hoped for ; and it is useless to attempt its pre- 
 paration on the great scale. Lewis says, however, that he has. 
 tested in this way a great many mosses, and that most of them 
 afforded him a yellow or reddish-brown colour; but that he 
 obtained from only a small nvimber a liquor of a deep red, which 
 communicated to cloth merely a yellowish-red* colour. 
 
 * The Chemical Works of Gaspard Neumaii, 
 
OF RED. 
 
 367 
 
 Prepared archil gives out its colour very readily to water, 
 ammonia, and alcohol. Its solution in alcohol is used for filling 
 spirit of v^ine thermometers ; and when these thermometers are 
 well freed from air, the liquor loses its colour in some years, as 
 Abbe Nollet observed.* The contact of air restores the colour, 
 which is destroyed anew in vacuo in process of time. The 
 watery infusion loses its colour by the privation of air in a few 
 days ; a singular phenomenon, which merits new researches. 
 
 The infusion of archil is of a crimson bordering on violet. As 
 it contains ammonia, which has already modified its natural 
 colour, the fixed alkalies can produce little change on it, only 
 deepening the colour a little, and making it more violet. Alum 
 forms in it a precipitate of a brown-red : and the supernatant 
 liquid retains a yellowish-red colour. The solution of tin afibrds 
 a reddish precipitate, which falls down slowly ; the supernatant 
 liquid retains a feeble red colour. The other metallic salts pro- 
 duce precipitates that offer nothing remarkable. 
 
 The watery solution of archil applied to cold marble penetrates 
 it, communicating a beautiful violet colour, or a blue bordering 
 on purple, which resists the air much longer than the archil 
 colours applied to other substances. Dufay says, that he has 
 seen marble tinged with this colour, preserve it without altera- 
 tion at the end of two years. 
 
 To dye with archil, the quantity of this substance deemed 
 necessary, according to the quantity of wool or stuff to be dyed, 
 and according to the shade to which they are to be brought, is 
 diffused in a bath of water as soon as it begins to grow warm. 
 The bath is then heated till it be ready to boil, and the wool or 
 stuff is passed through it without any other preparation, except 
 keeping that longest in, which is to have the deepest shade. A 
 fine gridelin, bordering on violet, is thereby obtained ; but this 
 colour has no permanence. Hence archil is rarely employed 
 ' with any other view than to modify, heighten, and give lustre to 
 the other colours. Hellot s^s, that having employed archil on 
 wool boiled with tartar and alum, the colour resisted the air no 
 more than what had received no preparation. But he obtained 
 from herb archil (rorseille d'herbe) a much more durable colour, 
 by putting in the bath some solution of tin. The archil thereby 
 
 * Mern. de I'acad. 1742. 
 
368 
 
 BERTHOLLET ON DYEING. 
 
 loses its natural colour, and assumes one approaching more or 
 less to scarlet, according to the quantity of solution of tin em- 
 ployed. This process must be executed in nearly the same 
 manner as that of scarlet, except that the dyeing may be per- 
 formed in a single bath. 
 
 Archil is frequently had recourse to for varying the different 
 shades and giving them lustre; hence it is used for violets, lilacs, 
 mallows, and rosemary flowers. To obtain a deeper tone, as for 
 the deep soupes au vin, sometimes a little alkali or milk of lime 
 is mixed with it. The sequel of this browning may also afford 
 agates, rosemary flowers, and other delicate colours, which cannot 
 be obtained so beautiful by other processes. Alum cannot be 
 substituted for this purpose ; it not only does not give this lustre, 
 but it degrades the deep colours. 
 
 The herb-archil is preferable to the archil of Auvergne, from 
 the greater bloom which it communicates to the colours, and 
 from the larger quantity of colouring matter. It has, besides, 
 the advantage of bearing ebullition. The latter, moreover, does 
 not answer with alum, which destroys the colour ; but the herb- 
 archil has the inconvenience of dyeing in an irregular manner, 
 unless attention be given to pass the cloth through hot water as 
 soon as it comes out of the dye. 
 
 Archil alone is not used for dyeing silk, unless for lilacs ; but 
 silk is frequently passed through a bath of archil, either before 
 dyeing it in other baths, or after it has been dyed, in order to 
 modify different colours, or to give them lustre. Examples of 
 this will be given in treating of the compound colours. It is 
 sufficient here to point out how white silks are passed through 
 the archil bath. The same process is performed with a bath 
 more or less charged with this colour, for silks already dyed. 
 
 Archil, in a quantity proportioned to the colour desired, is to 
 be boiled in a copper. The clear liquid is to be run off quite 
 hot from the archil bath, leaving the sediment at the bottom, 
 into a tub of proper size, in which the silks newly scoured with 
 soap, are to be turned' round on the skein sticks with much ex- 
 actness, till they have attained the wished-for shade. After this, 
 they must receive one beetling at the river. 
 
 Archil is in general a very useful ingredient in dyeing ; but as 
 it is rich in colour, and communicates an alluring bloom, dyers 
 are often tempted to abuse it, and to exceed the proportions that 
 
OF RED. 
 
 369 
 
 can add to the beauty, without, at the same time, injuring in a 
 dangerous manner the permanence of the colours. Nevertheless, 
 the colour obtained when solution of tin is employed, is less 
 fugitive than without this addition. It is red, approaching to 
 scarlet. It appears to be the only ingredient which can increase 
 its durability. The solution of tin may be employed, not only 
 in the dyeing bath, but for the preparation of the silk. In this 
 case, by mixing the archil with other colouring substances, dyes 
 may be obtained which have lustre with sufficient durability. 
 
 We have spoken of the colour of the archil, as if it were 
 natural to it, but it is really due to an alkaline combination. 
 The acids make it pass to red, either by saturating the alkali, or 
 by substituting themselves for the alkali. 
 
 The lichen which produces archil is subjected to another pre- 
 paration, to make turnsole {litmus,) This preparation is made 
 in Holland. The lichen comes from the Canary Islands, and 
 also from Sweden. It is reduced to a fine powder by means of 
 a mill, and a certain proportion of potash is mixed with it. 
 The mixture is watered with urine, and allowed to suffer a 
 species of fermentation. When this has arrived at a certain 
 degree, carbonate of lime in powder is added, to give consist- 
 ence and weight to the paste, which is thereafter reduced into 
 small parallelopipeds, that are carefully dried.* 
 
 CHAPTER IX. 
 Of Carthamus. 
 
 Carthamus or safflower {carthamus tinctorius), the flower of 
 which alone is used in dyeing, is an annual plant cultivated in 
 Spain, Egypt, and the Levant. There are two varieties of it, 
 one which has large leaves, and the other smaller ones. It is 
 the last which is cultivated in Egypt, where it forms a con- 
 siderable article of commerce. 
 
 Formerly carthamus was cultivated in Thuringia and Alsace ; 
 but the preference given to that of the Levant has caused its 
 
 * Journal des artes et manufactures, torn, ii, 
 2 B 
 
370 
 
 BERTHOLLET ON DYEING. 
 
 culture to be almost entirely abandoned in our climates. The 
 celebrated Beckman, who has given a very interesting disserta- 
 tion on carthamus,* has sought to discover the difference 
 between that raised in our climate, and that imported from the 
 Levant ; but before availing ourselves of his observations, it is 
 proper to describe the properties of this substance, such as it is 
 employed in dyeing. 
 
 Carthamus contains two colouring matters, one yellow and 
 the other red. The first, alone, is soluble in water ; its solution 
 is always turbid : with reagents, it exhibits the characters 
 usually remarked in yellow colouring matters ; the alkalies 
 render it lighter, the acids deepen it, giving it more of an 
 orange hue ; both produce a small dun precipitate, in conse- 
 quence of which it becomes clearer. Alum forms a precipitate 
 of a deep yellow in small quantity. The solution of tin and the 
 other metallic solutions cause precipitates, which have nothing 
 in them remarkable. 
 
 Alcohol takes but a slight dye from these flowers, out of 
 which all the yellow substance had been extracted by sufficient 
 washings (with water). If such flowers be put into a solution 
 of caustic alkali, they become yellow, and the liquor expressed 
 from them is of a deep yellow. On saturating the alkali with 
 an acid, the liquor becomes turbid, reddish, and deposites a 
 reddish-yellow precipitate in small quantity. A yellow precipi- 
 tate is formed, with solutions of alum, zinc, and tin ; and a 
 precipitate bordering on green, with solutions of iron and cop- 
 per. If a carbonate of an alkali has been used, the acids 
 produce an abundant and a redder precipitate ; but the shade 
 differs according to the acid employed. Alum produces also 
 with the latter alkaline solution a red precipitate, which is so 
 light that it usually floats on the surface of the liquor. This 
 colouring matter is so delicate, so easily affected, that if heat be 
 employed for dissolving it, the precipitates by the acids have no 
 longer the same beautiful colour. 
 
 Beckman has observed, that the carthamus of Thuringia con- 
 tains far more yellow matter than that of the Levant; that in 
 other respects the red matter of the former did not yield in 
 beauty to that obtained from the latter ; but that in order to 
 
 * Comment societ. Gotting. torn. iv. 1774. 
 
OF RED. 
 
 371 
 
 obtain an equal effect, one-half more of the one was required 
 than of the other. He inquired if this difference depended on 
 climate, or only on the preparation. 
 
 Hasselquist relates, in his Voyage d'Egypte, "that when 
 the flowers of carthamus are gathered, they are squeezed 
 between two stones to express their juice ; that they are there- 
 after washed several times with pit-well water, which in Egypt 
 is naturally saltish ; that, on coming out of the water, they are 
 pressed between the hands, and then spread out on mats upon 
 terraces ; that they are covered during the day, to hinder the 
 sun from drying them too much ; but that they are exposed to 
 the dew during the night ; that they are turned over from time 
 to time ; and that when they are found to be dried to the proper 
 point, they are taken up, and preserved for the market, under 
 the name of saffranon (safllower). 
 
 If the carthamus of the Levant, as found in commerce, be 
 compared with that of Thuringia, the former is observed to be 
 purer, a little damp, and in compressed masses ; while the latter 
 is drier and more elastic. These differences depend on the pre- 
 paration. The authors on agriculture, misled by the false 
 denomination of bastard saffron, given to carthamus, have 
 thought it should be treated like saffron. They consequently 
 direct to gather it in a dry season, and also to dry it with much 
 care. Beckman conceives that we should, on the contrary, imi- 
 tate the method adopted in Egypt : he recommends to add even 
 a little salt to the water used in the preparation, that it may 
 have the same quality as in Egypt. 
 
 The flower of carthamus has a fine flame colour ; it should be 
 gathered only when it begins to fade, and it is better when it 
 has received rain in this state, although there be a prejudice to 
 the contrary. The rain may be supplied by an artificial water- 
 ing of the flowers morning and evening. The seeds may still be 
 left to ripen after the blossom is cropped. 
 
 These directions are given with the view of separating the 
 yellow substance, a redundance of which may constitute the dif- 
 ference between the carthamus of our climate and that of the 
 Levant. It is proper to keep the carthamus in a moist place, 
 for too strong desiccation might injure it. 
 
 Many motives should induce us to enrich our agriculture with 
 this production. The seeds of carthamus serve as a very good 
 
 2 B 2 
 
372 
 
 BERTHOLLET ON DYEING. 
 
 nourishment to poultry, but particularly to parrots, whence 
 they have got the name of parrot seeds. A useful oil may be 
 expressed from them, and the residue may be given to cattle. 
 The dry leaves and twigs may serve as fodder to sheep and goats 
 during winter ; and the stronger stems, which the animals have 
 stripped, may be used for fuel. Beckman has proved, that car- 
 thamus ripened well at Gottingen, where the soil is sandy. The 
 ground should be dunged in moderation, and the plant must 
 be neither watered nor transplanted. We have seen some of it 
 grown at Amiens by the care of LapostoUe, which was of good 
 quality. 
 
 The yellow matter of carthamus is not employed ; but in 
 order to extract this portion, the carthamus is put into a bag, 
 which is trodden underwater, till no more colour can be pressed 
 out. The flowers, which were yellow, become reddish, and 
 lose in this operation nearly one half of their weight. In this 
 state they are used. 
 
 The yellow colouring substance might however be employed. 
 Poenor has made several experiments on this subject. Their 
 principal result is, that wool takes without preparation a yellow 
 hue which is not durable, but that which it takes after alum 
 and tartar is better, although it is not very permanent. Beck- 
 man says, that cloth prepared with tartar, or with tartar and 
 alum, takes a good yellow colour, and that, in equal weight, 
 carthamus contains more yellow colouring matter than yellow 
 wood (old fustic) itself. 
 
 For extracting the red part of carthamus, and thereafter 
 applying it to stuff*, the property which alkalies possess of dis- 
 solving it is had recourse' to, and it is afterwards precipitated by 
 an acid. Beckman says, that next to citric acid (acid of lemons), 
 sulphuric acid has the best effect, provided only the due propor- 
 tion be employed ; otherwise it alters and destroys the colour. 
 According to Scheffer, we may substitute for lemon juice the 
 juice of the berries of the mountain-ask {sorbus aucupatorius), 
 which is to be thus prepared. These berries are to be beat in 
 a mortar with a wooden pestle, and the juice is to be strained 
 off*, and allowed to ferment. It is then put into bottles ; and the 
 clear portion, which is sourest, is better fitted for this process 
 the older it is. This preparation requires some months, and 
 should be undertaken only in summer. 
 
OF RED. 
 
 373 
 
 The process of dyeing consists, therefore, in extracting the 
 red colouring matter by means of an alkali, and precipitating it 
 on the stuff by means of an acid. It is this fecula which serves 
 for making the rouge employed by ladies. 
 
 As to this rouge, the solution of carthamus is prepared with 
 crystallized carbonate of soda, and it is precipitated by lemon 
 juice. It has been remarked, that lemons beginning to spoil 
 were fitter for this operation, than those that were less ripe, 
 whose juice retained much mucilage. After squeezing out the 
 lemon juice, it is left to settle for some days. The precipitate 
 of carthamus is dried at a gentle heat, on plates of stone-ware ; 
 from which it is detached and very carefully ground with talc, 
 which has been reduced to a very subtile powder, by means of 
 the leaves of shave grass, (presle,) and successively passed 
 through sieves of increasing fineness. It is the fineness of the 
 talc, and the greater or less proportion which it bears to the 
 carthamus precipitate, which constitute the difference between 
 the high and low-priced rouges. 
 
 Wool may be dyed red by means of carthamus, as Beckman 
 has ascertained. This dye passes, however, very readily to 
 orange, and the power of obtaining from cochineal the finest 
 and most varied reds, which are at the same time much more 
 permanent than those of carthamus, makes the latter be rejected 
 for wool. 
 
 Carthamus is used for dyeing silk, poppy, nacarat, (a bright 
 orange-red,) cherry, rose colour, and flesh colour. The process 
 differs, according to the intensity of the colour, and the greater 
 or less tendency to flame colour that is wanted. But the car- 
 thamus bath, whose application may be varied, is prepared as 
 follows. 
 
 The carthamus, from which the yellow matter has been ex- 
 tracted, and whose lumps have been broken down, is put into a 
 trough. It is repeatedly sprinkled with cendres gravelees (crude 
 pearl ashes,) or soda (barilla) well powdered and sifted, at the 
 rate of 6^ pounds for 110 pounds of carthamus : but soda is 
 preferred ; mixing carefully as the alkali is introduced. This 
 operation is called amestrer. The amestred carthamus is put 
 into a small trough with a grated bottom, first lining this trough 
 with a closely woven cloth. When it is about half filled, it is 
 placed over the large trough, and cold water is poured into the 
 
374 
 
 BERTHOLLET ON DYEING. 
 
 upper one, till the lower becomes full. The carthamus is then 
 set over another trough, till the water comes from it almost co- 
 lourless. A little more alkali is now mixed with it, and fresh 
 water is passed through it. These operations are repeated till 
 the carthamus be exhausted, when it turns yellow. 
 
 After distributing the silk in hanks on the rods, lemon juice, 
 brought in casks from Provence, is poured into the bath, till it 
 becomes of a fine cherry colour ; this is called turning the bath, 
 {virer le bain.) It is well stirred ; and the silk is immersed, and 
 turned round the skein sticks in the bath, as long as it is per- 
 ceived to take up the colour. For ponceau (poppy colour) it is 
 withdrawn, the liquor is wrung out of it on the peg, and it is 
 turned through a new bath, where it is treated as in the first. 
 After this it is dried and passed through fresh baths, continuing 
 to wash and dry it between each operation, till it has acquired the 
 depth of colour that is desired. When it has reached the proper 
 point, a brightening is given it, by turning it round the sticks 
 seven or eight times in a bath of hot water, to which about half 
 a pint of lemon juice for each pailful of water has been added. 
 
 When silk is to be dyed poppy or flame colour, it must be 
 previously boiled as for white ; it must then receive a slight 
 foundation of annotto, as will be explained in treating of this 
 substance. The silk should not be alumed. 
 
 Nacarats, (orange-reds,) and deep cherry colours, are given 
 precisely like the poppy-reds, only they receive no annotto 
 ground ; and baths may be employed which have served for the 
 poppy-red, so as to complete their exhaustion. Fresh baths are 
 not made for the latter colours, unless there be no occasion for 
 the poppy. 
 
 With regard to the lighter cherry-reds, rose colours of all 
 shades, and flesh colours, they are made with the second and 
 last runnings of the carthamus, which are weaker. The deepest 
 shades are passed through first. 
 
 The lightest of all these shades, which is an extremely deli- 
 cate flesh colour, requires a little soap to be put into the bath. 
 This soap lightens the colour, and prevents it from taking too 
 speedily, and becoming unevenly. The silk is then washed, and 
 a little brightening is given it, in a bath which has served for 
 the deeper colours. 
 
 All these baths ctre employed the moment they are made, or 
 
OF RED. 
 
 375 
 
 as speedily as possible, because they lose much of their colour 
 on keeping, by which they are even entirely destroyed at the 
 end of a certain time. They are, moreover, u.sed cold, to 
 prevent the colour from being injured. It must have been 
 remarked, in the experiments just described, that the pure 
 alkahes attack the extremely delicate colour of carthamus, 
 making it pass to yellow. This is the reason why crystals of 
 soda are preferred to the other alkaline matters. Those at 
 least should be selected which contain most carbonic acid, as 
 salt of tartar. 
 
 In order to diminish the expense of the carthamus, it is the 
 practice, for the deeper shades, to mingle with the first and the 
 second bath about l-5th of the bath of archil. 
 
 For dyeing on raw silks, such as are very white should be 
 chosen, and be treated like boiled silks, with this single differ- 
 ence, that the poppies, the orange-reds, the cherries, should be 
 commonly passed through the baths which have already served 
 to make the same colours with boiled silk, because raw silk is, 
 in general, more easily dyed than boiled. 
 
 The poppy having been prepared in an acid liquid, resists the 
 proof by vinegar ; but it is speedily altered and destroyed in the 
 air. Scheffer says, that the colour for which mountain-ash berry 
 juice has been used instead of lemon juice, resists for a longer 
 period. 
 
 Beckman made experiments on the application of the red 
 colour of the carthamus to cotton.* He macerated cotton for 
 two hours in melted hog's lard ; he washed it w^ell, and after 
 this dyed it, in the ordinary way, with carthamus deprived of its 
 yellow matter. This cotton took a deeper colour than that 
 which had received no preparation. Soap succeeded equally 
 well, olive oil still better. Beckman next passed cotton several 
 times through oil, drying it alternately. After the last drying, 
 he washed and dried it. He passed it through the yellow bath 
 of carthamus, to which he added nut-galls and alum ; and, lastly, 
 he dyed it with the alkaline solution of carthamus and lemon 
 juice. He thus obtained a beautiful and saturated red colour. 
 The cotton treated without being irtipregnated with oil, took a 
 colour of the same kind, but it was less saturated, and withstood 
 
 * Experimenta Lina xylina tingendi flor. earth, tiuct. commeiitationes, Soc. Reg. Got- 
 ting, vol, iii. 1780. 
 
376 
 
 BERTHOLLET ON DYEING. 
 
 less the action of the air. The author, from these experiments, , 
 imagines that it would be necessary to give cotton that is to be 
 dyed with carthamus, preparations analogous to what it receives 
 in the Adrianople red dye. 
 
 To dye cotton, poppy, Wilson directs us to put the carthamus 
 well freed from its yellow colouring matter, into a vessel having 
 a hair sieve near its bottom, and to pour over it a solution of 
 pearl ashes, to mix well, and let the whole stand for a night. 
 Next morning the liquid is drawn off by a stopcock at the 
 bottom of the vessel. The piece of cotton to be dyed is plunged 
 in, and turned through it by means of a winch. A solution of 
 tartar is prepared, allowed to settle, and while it is still hot 
 some of it is to be poured into the solution of carthamus till 
 this liquid becomes a little sour. The cotton is to be perpetu- 
 ally turned about through this mixture, till it has assumed the 
 wished-for shade. It is then to be slightly washed and dried in 
 a stove. By this process it takes a very fine colour. 
 
 If it be desired to give a scarlet colour to cotton, it must first 
 be dyed yellow by the process described in the chapter on 
 annotto, and while still moist, it is to be dyed with carthamus, 
 as above. It takes a colour as beautiful as scarlet, but one of 
 little durability, which does not bear washing with water. 
 
 In Egypt, there is given to cotton, and even linen, a very 
 saturated and somewhat permanent colour, by means of car- 
 thamus. The carthamus is subjected to two successive mace- 
 rations, each of twenty-four hours, in pit-well water slightly 
 alkaline. After this it is mixed with l-5th of its weight of 
 (alkaline) ashes, purchased from the Arabs, which contain a little 
 carbonate of soda. This mixture is ground in a mill ; and some 
 water of the Nile is then filtered through it. By this means, 
 a liquid strongly charged with colouring matter is obtained. 
 They commence dyeing with the portion last filtered, which is 
 feebly charged ; they pour into it a little lemon juice ; then mix 
 in a boiler the first portion of the liquid, with a considerable 
 quantity of lemon juice, and dye at a heat of 122°, or 14^5"" 
 Fahr. They finish, by passing the stuff* through an acidulous 
 water, and drying it.* 
 
 * Mcmoires sur TEgypte. 
 
OF RED. ♦ 
 
 377 
 
 CHAPTER X. 
 Of Brazil Wood. 
 
 This wood/ which is much used in dyeing, derives its name 
 from the part of America whence it was first imported. It has 
 also the name of Fernambucca, wood of Saint Martha, or of 
 Sapan, according to the places which produce it. At present it 
 is cultivated in the Isle of France, where it has been natu- 
 ralized. That of the Antilles, called bresillet braziletto^ is least 
 esteemed. 
 
 Linnaeus distinguishes the tree which furnishes the brazil 
 wood, by the name of ccesalpinia crista ; that of Japan, or the 
 wood of Sapan, distinguished into large and little Sapan wood, 
 by the name ccesalpinia sapan ; and, lastly, he denominates the 
 bresillet, ccesalpinia vesicaria* 
 
 This tree commonly grows in dry places, and amid rocks. Its 
 trunk is very large, crooked, and full of knots. The flowers of 
 the wood of Sapan, and the bresillet, have 10 stamina; those of 
 the genuine brazil wood have only five. That which comes from 
 Fernambucca is most valued. 
 
 Brazil wood is very hard, susceptible of a fine polish, and 
 sinks in water. It is pale when newly cleft, but becomes red on 
 exposure to air. It has different shades of red and orange. 
 Its goodness is determined particularly by its density. When 
 chewed, a saccharine taste is perceived. It may be distinguished 
 from red saunders wood, as the latter does not yield its colour 
 to water. 
 
 Boiling water extracts the whole colouring matter of brazil 
 wood. If the ebullition be long enough continued, it assumes 
 a fine red colour. The residuum appears black. In this case, 
 an alkali may still extract much colouring matter. The solution 
 in alcohol or ammonia is still deeper than the preceding.' Ac- 
 cording to Dufay, a red colour, passing into violet, may be given 
 by the alcohol of brazil wood to heated marble. If the heat be 
 increased while the stained marbles are coated with wax, the 
 colour runs through all the shades of brown, and settles into a 
 chocolate. 
 
378 
 
 BERTIIOLLET ON DYEING. 
 
 The recent decoction of brazil wood affords, with sulphuric 
 acid, a scanty red precipitate, bordering on dun ; the liquor re- 
 mains transparent, and of a yellow colour. Nitric acid makes 
 the tincture pass at first to yellow ; but if more of it be added, 
 the liquor takes a deep orange-yellow colour, and becomes 
 transparent, after depositing a precipitate nearly similar to the 
 preceding, and more abundant. Muriatic acid comports itself 
 like the sulphuric. Oxalic acid gives a precipitate of an 
 orange-red, almost russet, and nearly as abundant as that of 
 nitric acid. The liquor remains transparent, and of the same 
 colour as the preceding. Distilled vinegar gives a very little 
 precipitate of the same colour ; the liquor remains transparent^ 
 and a little more of an orange hue. Tartar furnishes still less 
 precipitate ; the liquor remains turbid, and redder than the 
 last. Fixed alkali brings down the decoction to crimson, or 
 deep violet bordering on brown, and affords an almost impercep- 
 tible precipitate of the same colour. Ammonia gives a lighter 
 violet or purple, and a fine purple precipitate in small quantity. 
 Alum occasions a red precipitate verging on crimson, copious 
 and slow of falling. The liquor floating over it retains a fine 
 red colour, similar to that of the fresh decoction. This liquor 
 affords, moreover, an abundant precipitate, if the acid of the 
 alum be saturated with an alkali. Thus a species of carmine 
 inferior to ordinary carmine, and a liquid lake for miniatures, 
 may be prepared. Alum along with tartar forms a scanty 
 brownish-red precipitate ; the liquor remains very clear, and of 
 an orange-red hue. The sulphate of iron causes the tincture to 
 take a black colour bordering on violet ; the precipitate is abun- 
 dant, and of the same colour, as well as the supernatant liquor. 
 The sulphate of copper gives, in like manner, abundance of 
 precipitate, but it is much duller; the liquid remains trans- 
 parent, and of a russet-brown. Sulphate of zinc affords a scanty 
 brown precipitate ; the transparent liquor which stands over it 
 is of the colour of pale beer. Solution of acetate of lead causes 
 an abundant precipitate of a tolerably beautiful dark red ; the 
 transparent liquid is orange-red. The solution of tin in nitro- 
 muriatic acid affords a very abundant precipitate of a fine rose 
 colour; the liquor remains transparent, and quite colourless. 
 Lastly, with corrossive muriate of mercury a light precipitate, 
 
OF RED, 
 
 379 
 
 of a brown colour, is obtained ; the liquor remains transparent, 
 and of a fine yellow hue. 
 
 In the Journal de Physique,* very curious experiments are 
 to be found on the action which the acids exercise on brazil 
 wood. If, after having changed it to yellow by means of 
 tartar and acetic acid, solution of nitro-muriate of tin be 
 poured into it, there is immediately formed a very abundant 
 rose precipitate. If to the solution made yellow by an acid, a 
 larger quantity of this acid, or of a stronger acid, be added, 
 the red colour is restored. Sulphuric acid is best adapted 
 to produce this effect. Some salts, also, make the red colour 
 of brazil reappear, after it has disappeared by the action of 
 acids. (Note 00.) 
 
 The decoction of brazil wood, called juice of brazil, is ob- 
 served to be less fit for dyeing when recent, than when old or 
 even fermented. By age it takes a yellowish-red colour. For 
 making this decoction, Hellot recommends to use the hardest 
 water ; but it should be remarked that this water deepens the 
 colour in proportion to the earthy salts which it contains. After 
 boiling this wood reduced to chips^ or what is preferable, to pow- 
 der, for three hours, this first decoction is poured into a cask. 
 Fresh water is poured on the wood, which is then made to boil 
 for three hours, and mixed with the former. When brazil wood is 
 employed in a dyeing bath, it is proper to enclose it in a thin 
 linen bag, as well as all the dye-woods in general. 
 
 Wool immersed in the juice of brazil takes but a feeble 
 tint, which is speedily destroyed'. It must receive some pre- 
 parations. 
 
 The wool is to be boiled in a solution of alum, to which a 
 fourth or even less of tartar is added, for a larger proportion of 
 tartar would make the colour yellower. The wool is kept im- 
 pregnated with it for at least eight days, in a cool place. After 
 this, it is dyed in the brazil juice with a slight boiling. But 
 the first colouring particles that are deposited afford a less beauti- 
 ful colour ; hence it is proper to pass a coarser stuff previously 
 through the bath. In this manner a lively red is procured, 
 which resists pretty well the action of the air. 
 
 If the red colour of brazil be destroyed by means of any acid 
 
 * February, 1783. 
 
380 BERTHOLLET ON DYEING. 
 
 whatsoever, it will give to woollen stuffs a fawn colour of greater 
 or less depth, which is very durable in the air, 
 
 Poerner prepares the cloth with a bouillon composed of 
 solution of tin, alum, and a little tartar ; and he makes his bath 
 with fernambucca, and a considerable proportion of alum. In 
 the residuum of this bath he dyes a second piece, which has 
 received a similar preparation. The first piece takes a fine brick 
 colour, and the second a colour approaching to scarlet.* The 
 shades may be greatly varied by changing the proportions of the 
 ingredients. 
 
 By these means sufficient permanence may be given to the 
 colours derived from brazil wood ; they cannot, however, be 
 compared, in this respect, to those obtained from cochineal or 
 madder. Bloom is sometimes given to the colour derived from 
 the last substance, by passing the cloth dyed with it through 
 juice of brazil; but this lustre soon goes off. 
 
 Guhliche gives a process by which he says that more beauti- 
 ful and permanent colours may be obtained than by those now 
 in use. He directs us to pour on the fernambucca, reduced to 
 powder or in thin chips, pure vinegar, or aceto-citric acid,f or 
 nitro-muriatic acid, till it be covered, and the liquor floats over 
 it at a certain height; to agitate the mixture well, to let it 
 settle for 24 hours, then to decant the liquor, filter, and preserve 
 for use. A vegetable acid, or mere water, is poured upon the 
 residuum. It is suffered to settle one or two days ; it is filtered, 
 and this practice is continued till the extraction of the colouring 
 
 * lastruction sur Tart de la teinture. 
 
 t We call aceto-citric acid, an acid liquor of which Guhliche makes a great use in 
 dyeing, under the name of vegetable acid spirit, and which he prepares in the following 
 manner : — He takes lemons, such as have even the rind rotten may serve for this purpose ; 
 he separates the rind and adhering skin : he cuts them in slices, in a vessel which must not 
 be of wood ; he sprinkles them with a quantity of good vinegar, which he considers as ap- 
 proaching to that of lemons ; he squeezes this mixture through flannel with a press, and 
 filters the expressed juice through paper. In this state this liquor may be employed with 
 success ; but it has the inconvenience of growing mouldy, and the acid is very watery. He 
 recommends us, in order to preserve it for use, and to have it in a more concentrated state, 
 so that it may not dilute the baths into which it enters, to purify and concentrate it as 
 follows : — The liquor is left exposed to the sun till it becomes clear, and till the deposite be 
 formed. It is filtered and distilled on a sand bath. The receiver is to be changed when 
 the drops become acid, and the distillation is continued till oily striae be perceived on the 
 neck of the retort. The acid found in the receiver is to be kept for use. 
 
OF RED. 
 
 381 
 
 substance be completed. The wood is then black. The whole 
 liquors are to be mixed together. 
 
 The stuff was first prepared by a feeble galling with sumach 
 or white gall-nuts. After this a slight aluming is given. It is 
 merely rinced in water, and put quite moist into the bath, which 
 is prepared as follows : — 
 
 The acid solution (infusion) of fernambucca is taken and 
 diluted with a certain quantity of water, proportioned to the 
 quantity of stulf, and to the force of the colour wished to be 
 given. It is heated as high as the hand can bear. Solution of 
 tin is now poured in, till the whole takes a flame colour; it is 
 stirred, and the stuff is immersed and kept there for half an 
 hour, when it is taken out and washed. The remainder of the 
 bath may serve for the lighter shades. For these shades, the 
 stuff should not be galled. 
 
 Brazil wood is made use of for dyeing silk what is called 
 false crimson, to distinguish it from the crimson made by means 
 of cochineal, which is much more permanent. 
 
 The silk should be boiled at the rate of 20 parts of soap per 
 cent., and then alumed. The aluming need not be so strong as 
 for the fine crimson. The silk is refreshed at the river, and 
 passed through a bath more or less charged with brazil juice, 
 according to the shade to be given. When water free from 
 earthy salts is employed, the colour is too red to imitate crimson : 
 this quality is given it by passing the silk through a slight alka- 
 line solution, or by adding a little alkali to the bath. It might, 
 indeed, be washed in a hard water till it had taken the desired 
 shade. 
 
 To make deeper false crimsons of a dark red, juice of logwood 
 is put into the brazil bath, after the silk has been impregnated 
 with it. A little alkali may be added, according to the shade 
 that is wanted. 
 
 To imitate poppy, or flame colour, an annotto ground is given 
 to the silk, deeper even than when it is dyed with carthamus. 
 It is washed, alumed, and dyed with juice of brazil, to which 
 a little soap is usually added. 
 
 The solution of tin cannot be employed with brazil juice for 
 dyeing of silk, in the same way as with cochineal, the reason of 
 which is the same. The colouring particles separate too readily 
 to be capable of fixing on the silk, which has not so efficacious 
 
382 
 
 BERTHOLLET ON DYKING. 
 
 an attraction for them as wool has. But as Bergmann remarks, 
 in his notes on the work of Scheffer,* it is possible, by mace- 
 rating the silk in a cold solution of tin, to improve greatly the 
 colour of the dye-woods. A strong decoction of brazil, says he, 
 gives to yellow silk a colour of scarlet, inferior, indeed, to that 
 of cochineal, but more beautiful and more permanent than by 
 the maceration of alum alone ; and it can resist the proof by 
 vinegar, like true crimson and poppy. Instead of employing 
 raw silk, a yellow ground should be given to boiled silk, or a 
 yellow substance may be mixed with the juice of brazil. Several 
 dyers have been employed on this process more lately, and they 
 have produced very diversified effects, by applying it to different 
 colouring substances, which, of themselves, afford merely colours 
 of little permanence, either by using them alone, or by forming 
 different mixtures. 
 
 Poerner made a great many researches on the methods which 
 may be employed to dye cotton by means of brazil, employing 
 different mordants, as alum, solution of tin, sal ammoniac, pot- 
 ash. Sec, in the bath, or in the preparation of the stuff; but he 
 did not obtain colours which could resist the action of soap, 
 although some of them stood pretty well the action of the air 
 and washing with water. He recommends us to dry in the 
 shade the cottons which have received these colours.f 
 
 To Brown, who is engaged with much zeal in the arts, we 
 are indebted for a process which is used for a crimson on cotton 
 in some mianufactories. 
 
 A solution of tin is prepared in the following proportions : 
 Nitric acid, four parts; muriatic acid, two parts; tin, one part; 
 water, two parts. The liquids are to be mixed, and the tin dis- 
 solved in them, by adding it in small bits at a time. 
 
 For a piece of cotton velvet, weighing from 15 to 17^ pounds, 
 we begin by preparing a bath composed of four parts of boiling 
 water, and two parts of a strong decoction of nut-galls. The 
 bath is raked up, the piece is let down into it, worked there for 
 half an hour, and allowed to remain for two hours more ; at 
 the end of this time it is taken out, and set t'o drain. Another 
 bath is prepared with three pailfuls of boiling water, and one 
 pailful of decoction of wood of Fernambucca, also boiling. It 
 
 * Essai siir Vart de la teinture. 
 
 t Versuche und bemerkungen zum nutzen der Farbekunst zweitcr Theil. 
 
OF RED. 
 
 383 
 
 is raked, and the piece is worked in it for an hour. This bath 
 is emptied, and the vat washed out, and then filled with a clean 
 boiling-hot decoction of wood. The piece is worked in this for 
 half an hour, and lifted up on a winch. A bath of very clear 
 river water is now got ready, into which nearly a quart of solu- 
 tion of tin is poured. After the bath is raked, the piece is 
 worked in it for a quarter of an hour. It is then lifted on the 
 winch, carried back above the vat containing the bath of decoc- 
 tion of fernambucca wood, one-sixth of which is taken out and 
 replaced by an equal quantity, of boiling solution. After raking 
 up, the piece is worked in this bath for half an hoar. It is 
 raised upon the winch, and then transferred to the vat contain- 
 ing the solution of tin. This alternate working is repeated six 
 or eight times, observing to withdraw each time one-sixth of the 
 bath of fernambucca wood, and to replace it by an equal quan- 
 tity of the boiling decoction of the same wood ; to stir the bath 
 of the composition every time with the rake ; and to finish the 
 dye by leaving it in the last bath. The piece is washed in a 
 stream of water, and it is carefully dried in a dark place. 
 
 An analogous process is used for making the chocolates. After 
 galling the cotton, it is alumed and maddered with an inter- 
 mediate drying ; it is next passed through the fernambucca, and 
 the solution of tin. Some persons substitute muriate of tin for 
 this solution. 
 
 In investigating the means best adapted to procure more per- 
 manence to the beautiful and varied colours that are obtained at 
 little expense from brazil wood, it is proper to recapitulate 
 some of its properties. 
 
 The colouring particles of brazil wood are easily affected, and 
 made yellow by the action of acids. They thus become per- 
 manent colours. But what distinguishes them from madder 
 and kermes, and approximates them to cochineal, is their re- 
 appearing in their natural colour, when they are thrown down in 
 a state of combination with alumina, or with oxyde of tin. 
 These two combinations seem to be the fittest for rendering them 
 durable. It is requisite, therefore, . to inquire what circum- 
 stances are best calculated to promote the formation of these 
 combinations, according to the nature of the stuff. 
 
 The astringent principle, likewise, seems to contribute to the 
 
384 
 
 BERTHOLLET ON DYEING. 
 
 permanence of the colouring matter of brazil wood ; but it 
 deepens its hue, and can only be employed for light shades. 
 
 The colouring particles of brazil wood are very sensible to 
 the action of alkalies, which give them a purple hue ; and there 
 are several processes in which the alkalies, either fixed or vola- 
 tile, are used for forming violets and purples. But the colours 
 obtained by these methods, which may be easily varied according 
 to the purpose, are perishable, and possess but a transient bloom. 
 The alkalies appear not to injure the colours derived from mad- 
 der, but they accelerate the destruction of most other colours. 
 
 In England and Holland the dye-woods are reduced to powder 
 by means of mills erected for the purpose. It appears, from 
 the statement of Wilson, that they are kept moistened with 
 urine, or, if this be not used, a little alkali is added when they 
 are to be boiled. 
 
 The practice of reducing these woods to powder is of advan- 
 tage, and ought to be generally adopted. In the Journal of 
 Arts and Manufactures, (French,) volume first, is a description 
 of the mills employed in Holland, and of the operations to 
 which the dye-woods are subjected. When the woods are 
 employed, and especially if they be in powder, it is proper to 
 put them into a bag, before introducing them into the dyeing- 
 baths. Putrefied urine and alkali, by promoting the extraction 
 of the colouring particles, and increasing the tone of their 
 colour, may frequently be hurtful to the effect wished to be 
 obtained, or may accelerate their destruction, (Note PP.) 
 
 CHAPTER XI. 
 
 Of Logwood. 
 
 Logwood, {hois d'Inde,) wood of Campeachy, or of Jamaica, 
 has received these different names from the places where it 
 grows most plentifully. It is very common in Jamaica, and on 
 the eastern shore of the Bay of Campeachy. It is found also at 
 Santa Cruz, Martinique, and Grenada. 
 
OF RED. 
 
 385 
 
 Linnaeus calls the tree hcematoxylum campechianum. It 
 grows to a great height and thickness in a favourable soil. Its 
 bark is thin, smooth, of a brilliant grey, and sometimes yel- 
 lowish. Its trunk is straight, furnished with thorns : its leaves 
 have some resemblance to those of the laurel, to which they also 
 approach in their aromatic quality, whence the tree has got the 
 name of the aromatic or Indian (bay) laurel. As its seeds have 
 the taste of cloves, they have improperly got the name of clove- 
 seeds {graines de girojle.) The English call them Jamaica pepper^ 
 or all-spice. 
 
 Logwood is so heavy as to sink in water. It is hard, com- 
 pact, of a fine grain, capable of being polished, and scarcely 
 susceptible of decay. Its predominant colour is red, with orange, 
 yellow, and black tints. 
 
 For use, its juice is usually extracted like that of brazil wood. 
 It yields its colour to both spirituous and watery menstrua. 
 Alcohol extracts it more readily and abundantly than water. 
 The colour of its tincture is a fine red, bordering a little on 
 violet or purple, which is principally observable in its watery 
 decoction. This left to itself becomes in time )^ellowish, and 
 finally black. Acids change it to yellow, and the alkalies 
 deepen its colour, bringing it to a purple or violet. Sulphuric, 
 nitric, and muriatic acid occasion in it a slight precipitate, long 
 in falling ; which is of a dark red with sulphuric acid, a dead 
 leaf {feuille-morte) colour with the nitric, and a lighter red 
 colour with the muriatic. The supernatant liquor is trans- 
 parent, of a deep red colour with the sulphuric and muriatic 
 acids, and yellowish with the nitric. Oxalic acid forms a bright 
 chestnut precipitate : the liquor remains transparent, -of a yel - 
 lowish red. Acetic acid comports itself in nearly the same way, 
 only the colour of the precipitate is a little deeper. Tartar 
 gives a precipitate like vinegar ; but the liquor remains turbid^ 
 and inclines more to yellow. Fixed alkali forms no precipitate, 
 but causes the solution to pass to deep violet, which eventually 
 becomes almost brown. Alum occasions a pretty abundant preci- 
 pitate, of a light violet hue : the liquor remains violet, and 
 nearly transparent. Alum and tartar together produce a pretty co- 
 pious red' brown precipitate, and of a yellowish red. Sulphate of 
 iron gives immediately a blueish-black colour, like that of ink, 
 a precipitate is formed of the same colour, and the liquor re- 
 
 2 c 
 
386 
 
 BERTIIOLLET ON DYEING. 
 
 mains long turbid ; but if it be sufficiently diluted, and especi- 
 ally if there be a slight excess of sulphate, the whole black 
 matter finally falls down. Sulphate of copper produces a very 
 copious precipitate, of a browner and less brilliant black than 
 the preceding. The liquid remains transparent, of a very deep 
 yellowish or brownish red. Acetate of lead causes immediately 
 a black precipitate, with a slight reddish tint. The liquid 
 remains transparent, of a pale beer colour, and very bright. 
 Lastly, tin dissolved in nitro -muriatic acid instantly forms a 
 precipitate of a very fine violet colour, or purple, almost frune 
 de monsieur. The supernatant liquor is very clear and totally 
 colourless. 
 
 Stuff's would take in the decoction of logwood but a feeble 
 and fugitive colour, were they not previously prepared with 
 alum and tartar. A little alum is also added to the bath. By 
 this means they take a pretty fine violet. 
 
 A blue colour may be obtained from logwood, by mingling 
 verdigris with the bath, and passing the cloth through it till it 
 has taken the desired shade. 
 
 These uses of logwood have obtained for it the names of 
 violet wood and blue wood. When treating of the compound 
 colours, these hues will be more fully considered. 
 
 The main employment of logwood is for blacks, to which it 
 gives lustre and velvetiness ; and for greys of certain shades. It 
 is very extensively used also for different compound colours, 
 which it would be difficult to obtain as beautiful and as diversi- 
 fied by the ingredients of a more permanent dye. 
 
 The juice of logwood is often mixed with that of brazil 
 wood, to render the colours of a variable depth, according to 
 the proportions in which this mixture is made. 
 
 Logwood is used for dyeing silk violet, prior to which the 
 silk must be scoured, alumed, and washed, because without 
 aluming it would take only a reddish tint, which would not 
 bear wetting. This dye must be performed by turning the 
 silks cold round their skein sticks, in the decoction of logwood, 
 till they have acquired the colour that is wanted, because with 
 heat there is obtained merely a speckled and uneven colour. 
 
 Bergmann long ago remarked, that a more beautiful and per- 
 manent violet might be formed from logwood, by impregnating 
 the silk with a solution of tin, as has been stated in the pre- 
 
OF RED. 
 
 387 
 
 ceding chapter. There is thus obtained, indeed, especially by 
 mixing the logwood with brazil wood in different proportions, a 
 great many beaiitiful shades, bordering more or less on red, 
 from lilac to violet. 
 
 If decoction of logwood be employed for that of brazil wood 
 in the process communicated by Brown, a fine violet colour is 
 obtained ; and if the two decoctions be mixed together, shades 
 of puce and prune de mo7isieu7^ will be got, inclining more or less 
 to red. 
 
 The observations which have been given on brazil wood are 
 applicable to logwood, whose colouring matter presents analo- 
 gous properties. We shall only add, that in order to determine 
 the differences resulting from the state of oxydation of the tin, 
 when its solutions are used, we precipitated a decoction of 
 fernambucca, and a decoction of logwood, with the proto-mu- 
 riate of tin, and with the highly oxydized muriate. The 
 lakes thrown down by the former had at first less lustre ; but 
 on exposure to air they soon acquired the same tone as those 
 proceeding from a highly oxydized salt. We have, in like 
 manner, impregnated silk with the solution of the same salts, 
 and then dyed them with brazil wood and with logwood, when 
 the superiority of colour was in favour of the patterns which 
 had received the least oxydized salt. 
 
 When logwood has been employed in a process without so- 
 lution of tin, it may be recognized by the red colour which 
 the dyed stuff receives from an acid. (Note QQ.) 
 
 2 c 2 
 
SECTION IV. 
 
 OF YELLOW. 
 
 CHAPTER L 
 Of Weld. 
 
 Weld, or woald {la goude or vaude, in French, reseda 
 luteola^ Linn.)^ is a very common plant in the neighbourhood 
 of Paris, in the greater number of our departments, and a great 
 portion of the rest of Europe. 
 
 This plant puts forth long narrow leaves of a lively green. 
 From the midst of these leaves the stem rises to about the height 
 of a yard. It is often branchy, furnished with narrow leaves 
 like the radical ones, but shorter as they approach the flowers, 
 which are disposed in long spikes. The whole plant, except 
 the root, serves for dyeing yellow. 
 
 Two kinds of weld are distinguished, — the wild or bastard 
 weld, which grows naturally in the fields, — and the cultivated 
 weld, which pushes forth stems of less height and thickness. 
 The latter is preferred for dyeing ; it abounds much more in 
 colouring matter. It is esteemed in proportion to the slender- 
 ness of the stalks. 
 
 When the weld is ripe it is plucked up, allowed to dry, and 
 put up in bundles. In this state it is employed. 
 
 When the decoction of weld is highly charged, it has a yellow 
 colour bordering on brown ; when much diluted with water, its 
 yellow is more or less pale, and inclines a little to green. 
 
 If a little alkali be added to this decoction, its colour deepens, 
 and there takes place after a certain time a slight ash-coloured 
 precipitate insoluble in the alkalies. 
 
 The acids in general render its colour paler, and occasion a 
 small precipitate, which alkalies dissolve, with the assumption 
 of a yellow colour verging on brown. 
 
 Alum forms with it a yellowish precipitate : the supernatant 
 liquid retains a fine lemon colour. If a solution of alkali be 
 
OF YELLOW. 
 
 389 
 
 poured into this liquid, a precipitate forms of a whiteish-yellow, 
 soluble in alkalies, but the liquid remains always coloured. 
 
 The solution of muriate of soda, and that of muriate of 
 ammonia, make the liquor turbid, and at first of a somewhat 
 deeper hue. By degrees a precipitate falls of a deep yellow, 
 and the supernatant liquid retains a pale yellow colour, inclin- 
 ing a little to green. 
 
 The solution of tin produces an abundant precipitate of a 
 bright yellow ; the liquor continues long turbid, but little 
 coloured. 
 
 Sulphate of iron produces a copious grey-black precipitate ; 
 the supernatant liquid retains a brownish colour. 
 
 Sulphate of copper causes a brownish-green precipitate ; the 
 liquor preserves a pale green colour. 
 
 The yellow colour which weld communicates to wool has little 
 permanence, if the wool has not been previously prepared with 
 some mordants. Alum and tartar are employed ; and by this 
 means the plant affords the purest yellow, — a colour which 
 possesses the advantage of being durable. 
 
 For the bouillon, which is performed in the usual manner, 
 Hellot prescribes four parts of alum for sixteen of wool, and 
 only one of tartar. Several dyers, however, employ half as 
 much tartar as alum. The tartar renders the colour lighter, 
 but more lively. 
 
 For the welding {gaudage), that is to say, dyeing with weld, 
 the plant, enclosed in a thin bag, is boiled in a fresh bath, 
 which is loaded with a heavy wooden cross, that it may not rise 
 to the surface of the bath. Some dyers let it boil till it falls to 
 the bottom of the copper, after which they lay on it a champagne 
 (a weight to keep it down.) Others rake it out when it is 
 boiled, and throw it away. 
 
 Hellot prescribes from five to six parts of weld for one part 
 of cloth ; but so considerable a quantity is seldom employed, 
 dyers contenting themselves with three or four parts, or even 
 much less. It is true that several dyers add to the weld a little 
 quick lime and ashes, which favour the extraction of the colour- 
 ing matter, and heighten its colour, but render it at the same 
 time liable to change by the action of acids. The quantity of 
 weld, however, should be proportioned to the depth of shade 
 wanted. 
 
390 
 
 BERTHOLLET ON DYEING, 
 
 It is possible to dye in the sequel of the first dippings, in 
 order to obtain progressively paler shades, by adding water at 
 each dipping (mise,) and keeping the bath boiling ; but the light 
 shades obtained by this means have not so much vivacity as 
 when fresh baths are used, proportioning the quantity of weld to 
 the shade desired. 
 
 If muriate of soda be added to the weld bath, its colour 
 becomes richer and deeper. Sulphate of lime or gypsum ren- 
 ders it also deeper ; but alum makes it lighter and brighter, and 
 tartar paler. Sulphate of iron, or vitriol, causes it to draw 
 towards brown. The hues obtained from weld may be modified 
 by similar additions, by the proportions of the weld, by the 
 duration of the operation, and by the mordants employed for 
 the preparation of the stuff. Thus Scheifer says, that by boil- 
 ing the wool for two hours with one-fourth of solution of 
 tin, and one-fourth of tartar, washing it, and boiling it 15 
 minutes with an equal quantity of weld, it takes a beautiful 
 colour, but one which does not penetrate into the interior. 
 Poerner directs us also to prepare the cloth as for the scarlet 
 dye. By this means, more lustre and permanence are given to 
 the colour, which, ccsteris paribus, is also brighter. 
 
 The colour may be farther modified by passing the cloth, on 
 its coming out of the dye, through another bath. Thus, to 
 make a golden yellow, the cloth, on its leaving the welding, is to 
 be turned through a slight bath of madder ; and to give it a tan 
 colour, it is to be passed through a bath made with a little 
 soot. These methods will be spoken of in treating of sadden- 
 ings (brunitures). 
 
 To dye silk of a plain yellow {jaune franc,) no other ingre- 
 dient is commonly used except weld. The silk must be scoured 
 at the rate of 20 pounds of soap to the 100; afterwards alumed 
 and refreshed, that is to say, washed after the aluming. 
 
 A bath is made with two parts of weld for one of silk, and 
 after a full quarter of an hour's ebullition, it is filtered through 
 a sieve, or cloth, into a vat. When this bath is sufficiently 
 cooled to allow the hand to be plunged into it, the silk is 
 immersed and turned round the sticks till it be uniform. 
 During this operation, the weld is boiled a second time in fresh 
 water. About one half of the first bath is thrown out, and it 
 is replaced by the second bouillon. This fresh bath may be 
 
OF YELLOW. 
 
 391 
 
 employed a little hotter than the first ; too great a heat, how- 
 ev^er, must be avoided, by which a portion of the colour already 
 attached would be dissolved. It is to be turned as before, and 
 meanwhile, some crude pearl ash is to be dissolved in a portion 
 of the second bouillon. The silk is to be taken out of the bath, 
 in order to add to it more or less of this solution, according to 
 the shade that is wanted. After some turnings, a hank is wrung 
 with the pin, to see if the colour be sufiiciently full and golden. 
 If it be not enough so, a little more of the alkaline solution is 
 added, the property of which is to deepen the colour, and give 
 a golden hue. The process is continued, as before, till the silk 
 has attained to the wished-for shade. The alkaline solution 
 may be added also, at the same time, with the second bouillon 
 of weld, always taking care that the bath be not too hot. 
 
 If more golden-yellows be wanted, bordering^on jonquille, it is 
 necessary, when the ashes are put into the bath, to add some 
 annotto, in proportion to the shade desired. 
 
 For the light yellow shades, as pale lemon and canary, the 
 silk must be scoured as for blue, because these shades are more 
 beautiful and transparent the whiter the ground is on which 
 they are placed. The strength of the bath is proportioned to 
 the shade sought for. If the yellow be wished to have a cast 
 verging on green, more or less of the (indigo) vat is added, if 
 the silk has been scoured without azure. To prevent these 
 shades from being too deep, a slighter aluming than usual maybe 
 given to the silk. 
 
 Scheffer directs us to soak the silk for 24 hours in a solution 
 of tin, prepared with four parts of nitric acid, one of muriate 
 of soda, and one of tin, the solution being saturated with 
 tartar ; to wash it, and boil it for half an hour with its own 
 weight of flowers of weld. He says that a fine straw colour is 
 thereby obtained, which has the advantage of resisting the 
 acids. In adopting this process, very little tin must remain 
 in the solution, because the tartaric acid throws it down. The 
 observations which we have previously made on the use of tin, 
 may be applied here. 
 
 For dyeing cotton yellow, the first thing is to scour it in a 
 bath prepared with a lixivium of the ashes of green wood, then 
 to wash and dry it. It is alumed with the fourth of its weight 
 of alum. After twenty-four hours it is taken out of the alum- 
 
392 
 
 BERTHOLLET ON DYEING, 
 
 iiig and dried, without washing. A weld batli is thereafter 
 prepared, at the rate of one part and a quarter of weld for one 
 of cotton. In this the cotton is dyed, by turning it round the 
 sticks, and working it with the hands, till it has acquired the 
 wished-for shade. It is taken out of this bath to be macerated 
 for an hour and a half in a solution of sulphate of copper or 
 blue vitriol, in the proportion of one-fourth of this salt to one 
 part of cotton. It is next thrown, without washing it, into a boil- 
 ing solution of white soap, made in the same proportions. After 
 being well stirred, it is to be boiled for nearly an hour, after 
 which it must be well washed and dried. 
 
 If a deeper yellow, bordering on jonquille, be wanted, the 
 cotton is not passed through the aluming, but two parts and a 
 half of weld are employed to one of cotton, with the addition of 
 a little verdigris dissolved in a portion of the bath. The cotton 
 is plunged into it, and worked, till it has taken an uniform 
 colour. It is lifted out of the bath that a little soda ley may 
 be poured in, when it is again immersed and turned through the 
 bath for a full quarter of an hour. It is then withdrawn^ 
 wrung, and dried. 
 
 Lemon yellow is made by the same process, except that only 
 one part of weld is used (for one of cotton,) while the quantity 
 of verdigris can be diminished in proportion, or even entirely 
 omitted, and aluming put in its place. Thus the shades of 
 yellow may be varied in many ways. The operations on linen 
 yarn are the same. 
 
 For the yellow colours on printed cotton goods, these are im- 
 pregnated, by means of engraved plates, with the mordant 
 described in treating of madder, formed by the mixture of acetate 
 of lead and alum : the yellow colour induced on the parts not 
 impregnated with the acetate of alumina, is to be afterwards 
 destroyed by the action of bran, and exposure on the grass. 
 The same mordant may be successfully employed for cotton and 
 linen which is to be dyed yellow. 
 
 In order to obtain from weld the whole colour that it can 
 yield, it must be boiled for three quarters of an hour ; the 
 bundles of weld are now taken out of the bath, after which the 
 cloths are passed through it, at a temperature a little below 
 ebullition. They should not remain in it more than twenty 
 minutes. 
 
OF YELLOW. 
 
 393 
 
 When the same piece of cloth is to exhibit the colours pro- 
 duced by both madder and weld, it is necessary to begin with 
 the maddering, and not to print on the mordant intended for 
 the weld till the operations of the madder are finished. This 
 rule is founded on the property which madder possesses of 
 fixing itself in the room of the yellow of weld ; so that if the 
 maddering be long continued after dyeing with weld, the colour 
 of the latter entirely disappears. Weld, on the contrary, does 
 not affect the colour produced by madder, provided the mordant 
 has been saturated with the latter, for otherwise a mixed colour 
 would be produced. 
 
 The operations required for restoring the white are much 
 longer, and demand much nicer management, after welding 
 than after maddering. 
 
 CHAPTER IL 
 Of Fustic {Bois Jaune,) 
 
 This is the wood of a large tree (niorus tinctoria,) which 
 grows in the Antilles, and principally at Tobago. It is of a 
 yellow colour, as its name denotes, and it has orange veins. Its 
 medullary prolongations are very thin. It is neither very hard 
 nor heavy. 
 
 The use of this wood for dyeing has only become general of 
 late years. It abounds much in colouring matter, affording a 
 colour which is permanent, especially on woollen stuffs. It 
 unites well with indigo ; has a moderate price ; and its quali- 
 ties entitle it to rank among the most valuable ingredients in 
 dyeing. 
 
 A strong decoction of this wood has a deep yellow-red colour ; 
 when diluted with water, it becomes orange-yellow. The acids 
 make this liquid turbid, with some inconsiderable differences ; a 
 slight greenish-yellow precipitate falls, and the supernatant 
 liquid is of a pale yellow. The alkalies redissolve the preci- 
 pitate, and give the liquor a deep reddish colour. 
 
 This is the colour which alkalies give to the decoction of 
 fustic ; they render it deeper and almost red. There is formed, 
 
394 
 
 BERTHOLLET ON DYEING. 
 
 with time, a deposite of a yellowish substance, which iidheres to 
 the vessel, and sometimes floats on the top. 
 
 Alum forms a small quantity of a yellow precipitate; the 
 liquor remains transparent, and of a less deep yellow. 
 
 Alum and tartar together, afford a precipitate which has the 
 same colour, but it is slower in falling. The liquor retains a 
 still deeper hue. 
 
 The muriate of soda makes the colour a little deeper, without 
 occasioning turbidity. 
 
 Sulphate of iron forms a precipitate at first yellow, but 
 which grows more and more brown ; the liquor continues brown, 
 and without transparency. 
 
 Sulphate of copper affords an abundant precipitate of a 
 brown-yellow ; the supernatant liquor retains a feeble greenish 
 colour. 
 
 Sulphate of zinc yields a greenish-brown precipitate ; the 
 liquor retains a reddish-yellow colour. 
 
 Acetate of lead forms an abundant orange-yellow precipitate ; 
 the liquor is transparent, and of a very faint greenish-yellow. 
 
 The solution of tin gives a very copious precipitate of a fine 
 yellow, a little brighter than the preceding ; the liquor retains a 
 faint yellow colour. 
 
 For use, yellow wood is cleaved into splinters, or, what is 
 better, reduced into chips or powder ; it is then enclosed in a 
 bag, to prevent some portions of it from fixing on the stuff* and 
 tearing it. 
 
 Weld gives to cloth which has received no preparation, only 
 a pale yellow, which does not long resist the action of the air ; 
 but yellow wood produces, without the aid of mordants, a 
 yellow colour, bordering on brown, which, though dull, resists 
 the air better. Vivacity is given to its colour, and its perma- 
 nence is augmented, by the mordants employed for weld, which 
 exercise on it an action altogether analogous : thus alum, 
 tartar, and solution of tin, render its colour brighter ; sea 
 salt and sulphate of lime dfeepen its hue. The processes which 
 have been pointed out for weld, may therefore be applied to 
 fustic, with this difference, that in order to obtain the same 
 shade, much less yellow wood must be employed. Thus, from 
 5 to 6 parts of this wood are sufficient to give a lemon 
 colour to 16 parts of cloth. The colours, however, obtained 
 
OF YELLOW. 
 
 395 
 
 by these processes, incline more to orange, and are duller than 
 those of weld. Occasionally, the two are mixed, according to 
 the effect wished to be obtained. 
 
 To Chaptal we owe an easy means of procuring from fustic 
 a livelier colour. Having remarked that the decoction of this 
 wood gave a precipitate with gelatin, and that a fine yellow 
 colour was then obtained from it, he prescribes, to boil in 
 the bath of yellow wood, parings of skins, glue, or other 
 animal matters ; and then, without filtering, the stuff is to be 
 worked in it, which will thus take ^ the most beautiful and 
 intense colour."* 
 
 CHAPTER III. 
 Of Quercitron. 
 
 To Bancroft we are indebted for this dye-stuff. He has 
 given an ample description of its properties, and of the uses 
 to which it is adapted. We shall here exhibit a summary 
 account of them. 
 
 Quercitron is the bark of the Quercus nigra of Linnaeus. The 
 epidermis, which yields a brownish colour, must be separated 
 carefully from the bark ; after which this is reduced to powder 
 in a mill. 
 
 This powder affords as much colouring matter as 8 or 10 
 parts of weld, and 4 of fustic. Its colour possesses a great 
 analogy to that of weld, but it is much cheaper. 
 
 Quercitron readily yields its colouring matter to water merely 
 tepid. An extract is obtained from it, amounting to l-12th the 
 weight of the bark ; but it is difficult to employ this in dyeing, 
 because if a boiling heat be used, its colour becomes brownish ; 
 and if the evaporation takes place slowly, it suffers another kind 
 of alteration. 
 
 The decoction of quercitron is of a brownish-yellow colour. 
 The alkalies deepen, and the acids brighten it. The solution 
 of alum separates a very small portion of its colouring matter, 
 which forms a deep yellow precipitate. The solutions of tin 
 
 * Mem. dc Pinstit. torn. i. 
 
396 
 
 BERTHOLLET ON DYEING. 
 
 produce a more copious precipitate of a lively yellow. Sulphate 
 of iron affords a plentiful precipitate of a deep olive colour; the 
 supernatant liquor is clear, and of a light olive-green. 
 
 For dyeing v^ool, it is sufficient to boil the quercitron with its 
 own weight, or one-third more than its weight, of alum, for two 
 minutes. The stuff is then introduced, and the deepest shades 
 are given at first, ending with straw colour. These colours may 
 be brightened, by passing the stuff on quitting the bath through 
 hot water, whitened with a little washed chalk. But the colour 
 obtained by this process ''is not so permanent as when the stuff 
 is subjected to a bouillon before passing it through the dyeing 
 bath. In this second method, the stuff is boiled for an hour, or 
 an hour and a quarter, in a solution of alum, containing one- 
 sixth or one-eighth of the weight of the wool. No tartar 
 should be used. It is next dyed in a bath prepared with a 
 weight of quercitron equal to that of the alum employed, till 
 the colour be sufficiently raised. Chalk being now introduced 
 into the bath to brighten the colour, the stuff is let down anew 
 for 8 or 10 minutes. 
 
 A brighter colour is obtained by means of solution of tin. 
 Bancroft directs us to employ for the bath an equal weight of 
 quercitron and solution of tin in nitro-muriatic acid, (or rather 
 in the mixture of nitric and sulphuric acids, of which we have 
 spoken in treating of scarlet.) When a brilliant golden-yellow 
 colour is wanted, verging on orange, only 7 or 8 parts of solu- 
 tion of tin are employed for 10 of quercitron and 5 of alum. 
 A little tartar added to these ingredients gives a lemon colour, 
 bordering on green, which has hitherto been thought to be ob- 
 tainable only by weld. 
 
 Quercitron may be substituted for weld, for the different 
 shades given to silk, which should first be alumed. The dose is 
 from 1 to 2 parts of quercitron for 12 of silk. The colour may 
 be brightened by adding a little chalk or potash towards the 
 end of the operation. The solution of tin may also be used 
 along with alum, which should be in larger proportion. 
 
 In the substitution of quercitron for weld in calico printing, 
 Bancroft prescribes, after the preliminary operations of printing, 
 to diffuse the powdered quercitron in cold water, to introduce 
 the pieces to be dyed, and to heat the bath by degrees, turning 
 the cloth slowly round the winch. The colour is livelier and 
 
OF YELLOW. 
 
 397 
 
 more durable, if the heat be raised only a little above the tem- 
 perature of the human body, than when it approaches nearer to 
 ebullition. The intensity of the yellow may be varied, either 
 by increasing the proportion of quercitron, or by prolonging 
 the immersion. One advantage of this article over weld, is its 
 scarcely colouring the white grounds when the heat of the bath 
 has not been too much raised. Hence washing with cold water, 
 and especially with hot water, suffices, without its passage 
 through bran, and without exposure on the grass. From the 
 difference between the temperatures which quercitron and weld 
 require, the mixture of these two articles can produce no good 
 effect. The addition of tartar increases the property possessed 
 by quercitron, of not altering the white grounds. It makes the 
 colour verge towards that green shade which causes weld to be 
 sought after ; but in this case the heat of the bath must be 
 raised a little higher. 
 
 Bancroft describes a topical colour, which is obtained from 
 quercitron. A strong decoction of quercitron is made^ filtered, 
 and evaporated at a gentle heat, and when it is redjiiced to less 
 than one-half, it is allowed to cool to the temperature of the 
 living body. After this, one-fourth of acetate of alumina is 
 mixed with this liquid. The mixture is thickened with as much 
 gum as is necessary to prevent its running during the impres- 
 sion, but not so much as to obstruct its penetrating the stuff. 
 The colour obtained by this application has neither as much 
 intensity, nor as much permanence, as that procured by pre- 
 viously im pregnating the stuff with the mordant. Both qualities 
 may however be increased by a mixture of nitrate of coppei 
 and nitrate of lime. 
 
 Quercitron ought undoubtedly to be considered as a very use- 
 ful substance in dyeing ; yet the attempts which we know to 
 have been made, with the precautions prescribed by Bancroft, 
 especially in reference to the temperature of the bath, seem to 
 us to prove, that the colour derived from it is inferior in per- 
 manence to that producible from weld. A purer and more 
 lively colour may be obtained from quercitron, by adopting the 
 process which Chaptal has given for fustic, (yellow wood). 
 
398 
 
 BERTHOLLET ON DYEING. 
 
 CHAPTER IV. 
 Of Aniiotto (Rocou.) 
 
 Annotto (in French rocou or roucou^ is a somewhat dry and 
 hard paste, brown without, and red within. It is usually im- 
 ported in cakes (of two or three pounds' weight,) wrapped up 
 in leaves of large reeds, packed in casks, from America, where 
 it is prepared from the seeds of a certain tree, the hixa orellana 
 of Linnaeus. 
 
 We are indebted to Leblond for some accurate observations 
 concerning the cultivation of the tree whose seed serves for 
 making annotto, the preparations to which these are subjected, 
 and the means of improving this process.* 
 
 The pods of the tree being gathered, their seeds are taken 
 out and bruised. They are then transferred to a vat, (which is 
 called the steeper,) where they are mixed with as much water as 
 covers them. Here the substance is left for several weeks, or 
 even months ; it is now squeezed through sieves placed above 
 the steeper, that the water containing the colouring matter in 
 suspension may return into the vat. The residuum is preserved 
 under the leaves of the banana (pine apple) tree, till it becomes 
 hot by fermentation. It is again subjected to the same opera- 
 tion, and this treatment is continued till no more colour remains. 
 
 The substance thus extracted is passed through sieves, in 
 order to separate the remainder of the seeds, and the colour is 
 allowed to subside. The precipitate is boiled in coppers till it 
 be reduced to a consistent paste ; it is then suffered to cool, and 
 dried in the shade. 
 
 Instead of this long and painful labour, which occasions dis- 
 eases by the putrefaction induced, and which affords a spoiled 
 product, Leblond proposes, simply to wash the seeds of annotto 
 till they be entirely deprived of their colour, which lies wholly 
 on their surface, to precipitate the colour by means of vinegar, 
 or lemon juice, and to boil up in the ordinary manner, or to 
 drain in bags, as is practised with indigo. 
 
 The experiments which Vauquelin made on the seeds of 
 annotto imported by Leblond, confirmed the efficacy of the pro- 
 
 * Ann. do cliimie, torn, xlvii. 
 
OF YELLOW. 
 
 399 
 
 cess which he proposed, and the dyers have ascertained, that the 
 annotto obtained in this manner was worth at least four times 
 more than that of commerce ; that, moreover, it was more easily 
 employed ; that it required less solvent ; that it gave less trou- 
 ble in the copper, and furnished a purer colour. 
 
 Annotto dissolves better and more readily in alcohol than in 
 water; whence it is introduced into the yellow varnishes for 
 communicating an orange tint. 
 
 The decoction of annotto in water has a strong peculiar odour, 
 and a disagreeable taste. Its colour is yellowish-red, and it 
 remains a little turbid. An alkaline solution renders it orange- 
 yellow, clearer, and more agreeable ; while a small quantity of 
 a whiteish substance is separated from it, which remains sus- 
 pended in the liquid. If annotto be boiled in water along with 
 an alkali, it dissolves much better than when alone, and the 
 liquid has an orange hue. 
 
 The acids form with this liquor an orange -coloured precipi- 
 tate, soluble in alkalies, which communicate to it a deep orange 
 colour. The supernatant liquor retains only a pale yellow 
 colour. 
 
 Solution of muriate of soda and muriate of ammonia produce 
 no sensible change. 
 
 Solution of alum causes a considerable precipitate of a deeper 
 orange hue than the deposite formed by the acids ; the liquid 
 retains an agreeable lemon colour, verging a little towards 
 green. 
 
 Sulphate of iron forms an orange-brown precipitate ; the 
 liquor retains a very pale yellow colour. 
 
 Sulphat^ of copper affords a precipitate of a yellowish brown ; 
 a little brighter than the preceding; the liquor preserves a 
 greenish-yellow colour. 
 
 Solution of tin produces a lemon-yellow precipitate, which 
 falls slowly. 
 
 When annotto is used, it is always mixed with alkali, which 
 facilitates its solution, and gives it a colour inclining less to red. 
 The annotto is cut in pieces, and boiled for some instants in a 
 copper with its own weight of crude pearl ashes, provided the 
 shade wanted do not require less alkali. The cloths may be 
 thereafter dyed in this bath, either by these ingredients alone, 
 or by adding others to modify the colour ; but annotto is sel- 
 
400 
 
 BERTHOLLET ON DYEING. 
 
 dom used for woollen, because the colours which it gives are 
 too fugitive, and may be obtained by more permanent dyes. 
 Hellot employed it to dye a stuff prepared with alum and 
 tartar; but the colour acquired had little permanence. It is 
 almost solely used for silks. 
 
 For silks intended to become aurora and orange, it is sufficient 
 to scour them at the rate of 20 per cent of soap. When they 
 have been well cleansed, they are immersed in a bath prepared 
 with water, to which is added a quantity of alkaline solution of 
 annotto, more or less considerable, according to the shade that 
 may be wanted. This bath should have a mean temperature, 
 between that of tepid and boiling water. 
 
 When the silk has become uniform, one of the hanks is taken 
 out, washed, and wrung, to see if the colour be sufficiently full ; 
 if it be not so, more solution of annotto is added, and the silk 
 is turned again round the sticks. The solution keeps without 
 alteration. 
 
 When the desired shade is obtained, nothing remains but to 
 wash the silk, and give it two beetlings at the river, in order to 
 free it from the redundant annotto, which M'ould injure the 
 lustre of the colour. 
 
 When raw silks are to be dyed, those naturally white are 
 chosen, and dyed in the annotto bath, which should not be more 
 than tepid, or even cold, in order that the alkali may not attack 
 the gum of the silk, and deprive it of the elasticity which it is 
 desirable for it to preserve. 
 
 What has been now said regards the silks to which the aurora 
 shades are to be given ; but to make an orange hue, which 
 contains more red than aurora, it is requisite, after ^yeing with 
 annotto, to redden the silks with vinegar, alum, or lemon juice. 
 The acid, by saturating the alkali employed for dissolving the 
 annotto, destroys the shade of yellow that the alkali had given, 
 and restores it to its natural colour, which inclines a good deal 
 to red. 
 
 For the deep shades, the practice at Paris, as Macquer 
 informs us, is to pass the silks through alum ; and if the colour 
 be not red enough, they are passed through a faint bath of 
 brazil wood. At Lyons, the dyers who use carthamus some- 
 times employ old baths of this ingredient for dipping the deep 
 oranges. 
 
OF YELLOW. 
 
 401 
 
 When the orange hues have been reddened by alum, they 
 must be washed at the river ; but it is not necessary to beetle 
 them, unless the colour turns out too red. 
 
 Shades may be obtained also by a single operation, which 
 retain a reddish tint, employing for the annotto bath a less 
 proportion of alkali than has been pointed out. 
 
 Guhliche recommends to avoid heat in the preparation of 
 annotto. He directs it to be placed in a glass vessel, or in a 
 glazed earthen one, to cover it with a solution of pure alkali, 
 to leave the mixture at rest for 24 hours, to decant the liquor, 
 filter it, and add water repeatedly to the residuum, leaving 
 the mixture, each time, at rest for two or three days, till the 
 water is no longer coloured ; to mix all these liquors, and pre- 
 serve the whole for use in a well-stopped vessel. 
 
 He macerates the silk for 12 hours in a solution of alum, at 
 the rate of an eighth of this salt for one part of silk, or in 
 a water rendered acidulous by the aceto-citric acid above 
 described; and he wrings it well on its coming out of this 
 bath. 
 
 Silk thus prepared is put into the annotto bath, quite cold. 
 It is kept in agitation there till it has taken the shade sought 
 for ; or the liquor may be maintained at a heat far below ebulli- 
 tion. On being taken out of the bath, the silk is to be washed, 
 and dried in the shade. 
 
 For clearer hues, a liquor less charged with colour is taken ; 
 and a little of the acid liquid which has served for the mordant 
 may be added, or the dyed silk may be passed through the 
 acidulous water. 
 
 If the last shades are to have less of the orange, and to 
 approach the colour of nankeen, a little of the solution of nut- 
 galls, in white wine, is to be added. 
 
 To give an orange colour to cotton, Wilson directs us to 
 bruise the annotto when it is moistened, to boil it in water 
 with double its weight of alkali, to let it settle for half an hour, 
 to pass the clear liquor into a heated vessel, and to immerse the 
 cotton in it, when it will take an orange colour, A hot solution 
 of tartar is to be then poured into the bath, so as to make it 
 feebly acid; the cotton hanks are turned through it on the 
 skein-sticks, or wound on the winch when in the piece. The 
 colour becomes thereby more lively, and fixes better. A slight 
 
 2 D 
 
402 
 
 BERTHOLLET ON DYEING. 
 
 washing is afterwards given to the cotton, and it is dried in a 
 stove. 
 
 We have seen the following preparation employed for cotton 
 velvet. One part of quicklime, one of potash, two of soda. Of 
 these a ley is formed, in which one part of annotto is dis- 
 solved ; and the mixture is boiled for an hour and a half. This 
 bath affords the liveliest and most brilliant auroras. The buff 
 (chamois) fugitive dye is also obtained with this solution. For 
 this purpose only a little is wanted ; but we must never forget 
 that the colours arising from annotto are all fugitive. (Note RR.) 
 
 CHAPTER V. 
 
 Of Saw-wort (Sarette), Serratula Tinctoria^ and several other 
 Articles capable of dyeing Yellow. 
 
 The serratula tinctoria, saw-wort, is a plant which grows 
 abundantly in woods and meadows. It affords, without mor- 
 dants, a greenish yellow colour, which wants permanence ; but 
 by means of alum employed in a particular bouillon, or put into 
 the bath with the saw-wort itself, this plant gives a permanent 
 and agreeable colour. According to Poerner, the mordants that 
 suit it best are alum and sulphate of lime. It is needless to 
 state, that the last article forms a deeper shade, and that the hue 
 may be varied also by the proportion of mordant and of saw- 
 wort. Scheffer directs us to prepare the wool with alum and a 
 12th of tartar ; and adds, that if prepared with 3-16ths of 
 solution of tin, and as much tartar, it takes a much livelier 
 colour than the preceding. 
 
 Dyer's broom, or dyer's weed, {genista tinctoria, the genestrole 
 of the French,) which grows abundantly in dry and hilly 
 grounds, yields a yellow colour, which cannot be compared in 
 beauty with that of weld and saw-wort, but it acquires sufficient 
 permanence by means of mordants. Those which may be 
 employed with most advantage, either for the preparation of 
 the cloth or in the bath, are tartar, alum, and sulphate of 
 lime. 
 
 Chamomile, {camomilla matricaria,) a plant well enough 
 
OF YELLOW. 
 
 403 
 
 known^ afibrds a pretty agreeable faint yellow colour, but it is not 
 fast. Tlie mordants fix it a little ; of which the most useful are 
 alum, tartar, and sulphate of lime. 
 
 According to Scheffer, a beautiful yellow is given to silk 
 with the decoction of this plant, in which some solution of tin, 
 saturated with tartar, is poured, drop by drop, till the colour 
 shall become sufficiently yellow. For dyeing the silk, this is 
 kept hot without boiling. He recommends the employment of 
 pure water, which does not precipitate the solution of tin. 
 
 Fenugreek {trigonella foenugrcecum) produces seeds, which, 
 when ground, are capable of dyeing a pretty fast pale yellow. 
 The mordants which succeed best with this substance, are alum, 
 and muriate of soda. 
 
 The turmeric {curcuma longa, terra merita of the French) 
 is a root imported from the East Indies. It has been cultivated 
 at Tobago ; aud some of it sent thence was superior to that of 
 commerce, both in the thickness of its roots and the abundance 
 of its colouring matter. This substance is very rich in colour, 
 and no other affords so brilliant an orange-yellow. But it has 
 no permanence, nor can mordants give a sufficient degree of it. 
 Muriate of soda, and muriate of ammonia, are the substances 
 which best fix this colour, but they deepen it, and make it incline 
 to brown. Some persons recommend a small quantity of muriatic 
 acid. For employing this root, it must be reduced to powder. 
 It is sometimes used for giving yellows made with weld a gold 
 cast, as also for giving an orange hue to scarlet; but the shade 
 arising from the turmeric is not long of disappearing in the air. 
 
 Fustet Venus's sumach {rhus cotinus) is a wood possessing a 
 mixed colour of orange and green. Its fibres have a play of 
 colours. 
 
 This wood affords a fine orange colour which has no per- 
 manence ; hence it is not employed alone, but is used by 
 mixing it with other colouring substances, and particularly 
 with cochineal, to give the scarlet a flame colour, and for pome- 
 granates, jujubes, lobster-reds, oranges, jonquilles, golden co- 
 lours, buffs, and, in general, for all the colours with which we 
 wish to associate more or less of an orange hue. The advantage 
 to be found in the use of this substance, consists in its colour 
 becoming pale without change of shade; but when it is joined, 
 with other colours^ it is more durable than when aloncc 
 
 2 J) 2 
 
404 
 
 BERTHOLLET ON DYEING. 
 
 The grain of Avignon, French berries, (the berry of the rham- 
 nus infectorius, epine cormier in French,) which is gathered 
 before it is ripe, affords a pretty fine yellow, but it has no per- 
 manence. It may be used by preparing the cloth in the same 
 way as for dyeing with weld. As this berry is rich in colour, 
 it is often substituted for weld in calico-printing, although it is 
 inferior in quality. 
 
 The leaves of willow are mentioned by Scheffer as capable 
 of yielding a fine yellow colour to wool, silk, and linen. Berg- 
 mann says, that the leaves of the laurel willow should be 
 preferred, {salix peiitendra,) and that the leaves of common 
 willow afford a colour, most part of which is soon discharged by 
 the sun. 
 
 Scheffer directs the wool to be left for a night in a cold solu- 
 tion of one-fifth of alum, and one-sixteenth of tartar. The 
 houillon is made from the leaves picked up towards the end of 
 August or the beginning of • September, which have been dried 
 in a shady, but well-aired situation. Of these a suitable quantity 
 is to be taken, and boiled for half an hour, 1 -256th part of white 
 potash is added to it, to render the colour livelier and deeper, 
 after which the bath is passed through a sieve. It is kept in a 
 state approaching to ebullition, and the wool is died in it, till it 
 has assumed the wished-for colour. He prescribes the same 
 process for silk and linen, augmenting merely the proportion of 
 alum by a sixteenth. According to Bergmann's account, Al- 
 stroemer observed, that the colour was rendered richer by 
 macerating the flax with a larger quantity of alum, and wring- 
 ing and drying it before dyeing ; and that for the complete 
 extraction of the colouring matter, it was requisite to increase 
 the quantity of potash. 
 
 The bark, and particularly the young branches (shoots) of the 
 Italian poplar, and some other species of poplar, give to wool, 
 according to d'Ambourney, a fine durable yellow colour, espe- 
 cially when the wool has been prepared with solution of tin. 
 Nearly ^even parts in weight of this wood . are required to dye 
 one of wool. 
 
 The seeds of purple trefoil {trifolium pratense purpureum 
 niajus Raii) are employed in Switzerland and in England for 
 dyeing. Vogler has tried to determine what colours can be pro- 
 cured from it, and he found, that the bath of this seed, with 
 
OF YELLOW. 
 
 405 
 
 solution of potash, afforded a very deep yellow ; with sulphuric 
 acid, a clear yellow ; with solutions of alum and tin, a lemon 
 yellow; with sulphate of copper, a greenish-yellow. Woods 
 impregnated with these mordants, and boiled for some minutes 
 in the bath of purple trefoil seed, are found to be dyed very 
 durably different shades of the colours just enumerated. The 
 yellows form a fine green with indigo. Luzern {medicago sativa) 
 afforded the same results.* 
 
 Dize made comparative experiments with the trefoil and 
 weld.f It thence follows, that the trefoil seed gives to wool a 
 beautiful orange-yellow, and to silk a greenish-yellow ; that 
 solution of tin cannot be employed for this dye, because it 
 requires an aluming ; and, lastly, that blue applied to the yellow 
 derived from trefoil seed, forms a less beautiful and duller green 
 than that for which weld had been used. 
 
 Common Canada golden rod (solidago canadensis) had already 
 been recommended by Hellot. Gaad said, in the Memoirs of 
 Stockholm, that this plant afforded a yellow colour, superior 
 even to weld, and that it was far preferable to dyer's broom. 
 As no use has been made of it, however, and as it is a plant 
 easily cultivated, Succow subjected it to new trials. J As his 
 experiments with re-agents presented nothing peculiar, they may 
 be omitted. A decoction of the stalks of this plant, to which 
 the author added a considerable proportion of alum, gave to a 
 pattern of cloth, which had received no preparation, a very 
 lively straw-yellow colour : to another pattern, prepared with 
 sulphate of iron, a greenish-yellow colour ; and to a third pat- 
 tern, which had been prepared with alum, a very pure and lively 
 lemon-yellow Iiue. 
 
 The flowers of French Marygold {tagetes patula) separated 
 from their calyx, were submitted to the same trials. The cloth, 
 without preparation, took in the decoction of these flowers a 
 deep yellow colour; prepared with sulphate of iron, a greenish 
 colour, which, by continued ebullition, became very deep ; and, 
 lastly, cloth prepared with alum assumed a very lively yellow 
 colour, inclining a little to green. If a little alum be added to 
 the bath before immersing the stuff in it, a very beautiful and 
 
 * Annales de chimie, torn. iii. -j- Journ. de physique, \7( 0. 
 
 t Crell. Ann. chcm. 1787. 
 
406 
 
 PERTHOLLET ON DYEING. 
 
 lively yellow is obtained. It has more lustre than even the 
 colour procured from the Canada golden rod. 
 
 There are many other substances which may be employed for 
 dyeing yellow, and which afford shades of greater or less perma- 
 nence and beauty ; such are the bark of the barberry, the flower 
 of wild chervil or cow-weed, the common stinging nettle, the root 
 of patience-dock, the bark of the ash, the leaves of the almond 
 tree, of the peach tree, pear tree, the flowers of the common 
 furze, &c. In Part I. it was shown that nitric acid could also 
 be employed for giving a yellow colour. 
 
 White flowers, according to the observation of Lewis, give 
 the water with which they are boiled a somewhat deep yellow 
 colour. The acids, alkalies, and the salts, act upon this colour as 
 those of other vegetable substances.* 
 
 It appears that the substances which may be used for dyeing 
 yellow are very numerous. They differ from each other in the 
 quantity of colouring matter, in their dye being more or less plain, 
 lively, or of an orange or greenish cast, in their degree of perma- 
 nence,, and in their price. By comparing these particulars, a de- 
 termination is to be made as to their choice, according to the 
 quality of the stuff*, the colour that is wanted, and the concomit- 
 ant circumstances. 
 
 In general, the alkalies render the colour of these substances 
 deeper and more of an orange cast ; they facilitate the extraction 
 of the colouring matter ; and it is only by their means that it is 
 obtained from annotto ; but they also favour its destruction. 
 Sulphate of lime, muriate of soda, muriate of ammonia, deepen 
 the colour of yellow substances ; the acids brighten them, and 
 make them more permanent. Alum and the solution of tin 
 render them clearer, and at the same time more brilliant and 
 durable. 
 
 Few of the yellows produced from vegetable substances can 
 acquire upon cotton permanence comparable to that of the 
 colours producible from madder; and they never acquire this 
 quality without losing their lustre. When a colour rather fast 
 than brilliant is wanted, the cotton is coloured with oxyde of 
 iron, by impregnating it with any of the various solutions of this 
 
 * The Clicmical Works of Caspar Ncuman. 
 
OF YELLOW. 
 
 407 
 
 metal. The processes employed for this dye are very nmnerous, 
 and their shades may obviously be greatly multiplied, by varying 
 the state of oxydation of the metal, or the nature of the acid 
 which holds it in solution ; as also by slight changes in the pro- 
 portions of the materials, and in the manipulations. 
 
 In order to obtain a deep colour, Chaptal treads the cotton in 
 a solution of sulphate of iron, marking from 17° to 23° Twad- 
 del. He squeezes it very slightly, but equably. As soon as 
 the whole portion (lot) is dipped, it is repassed, hank by hank, 
 through the same solution, and immediately afterwards through 
 a solution of potash, marking the same number of degrees. The 
 colour of the cotton becomes of a dirty blue-green, which changes 
 in a few minutes to an agreeable golden yellow. At each dip- 
 ping the vessel into which the cottons are plunged must be 
 emptied, in order that the colour may be equal and uniform. 
 
 For a pale and very soft yellow, he treads the cotton in a solu- 
 tion of sulphate of iron, marking three degrees, and repasses it 
 as in the preceding process. On the other hand, he prepares a 
 liquor with solution of potash, marking from two to three 
 degrees, to which he adds solution of alum till he observes that 
 the flocks are no longer dissolved. He impregnates the cotton 
 with this liquid, and renews it for each dip. The cotton is 
 dyed of a very agreeable yellow. 
 
 When the colours are not sufficiently deep, the cotton may be 
 repassed through stronger solutions. 
 
 Chaptal recommends for making the colours evenly, to pass 
 at once no more than half a pound of cotton, to employ weak 
 solutions of sulphate of iron, to dip the cotton first in a solution 
 of potash, then in one of sulphate of iron, repeating these alter- 
 nate dips as often as shall be requisite to arrive at the desired 
 shade, and to use the greatest care in impregnating and squeez- 
 ing the cotton equably. 
 
 A fresh-butter yellow is produced, by passing the cotton 
 through slightly oxydized acetate of iron, mixed with nitrate of 
 iron, which may be made to incline more to red, the greater the 
 proportion of the latter salt. 
 
 With nitrate of iron alone diluted with water, a pretty clear 
 yellow may be had, which rises quickly. If the cotton be 
 impregnated with nitrate of iron a little diluted, allowed to dry, 
 
408 
 
 BERTHOLLET ON DYEING. 
 
 and then washed, it remains a very deep tint, similar to that 
 of rust. 
 
 The rust-yellow, which is printed on cloth, is made with 
 two parts of sulphate of iron, and one part of acetate of lead. 
 By mixing with this, different proportions of highly oxydized 
 oxyde of iron, shades bordering on red may be procured. 
 
 Cotton dyed by these processes takes very different colours in 
 the dye-baths. That which received a faint yellow colour by the 
 process of Chaptal, becomes of a walnut hue in the decoction of 
 galls. When the colour is deeper, it becomes mouse-grey ; 
 with tan or quercitron, it affords a yellow. When passed 
 through a decoction of equal parts of nut-galls, sumach, log- 
 wood, and weld, the cotton becomes of a dirty grey-white. 
 When dried, and passed through a strong solution of sulphate 
 of iron, it assumes the blueish grey colour, which is called ceit 
 de roL Note SS. 
 
SECTION V. 
 
 OF DUN, ROOT, OR FAWN COLOUR, (fAUVE.) 
 
 On LY some of the substances employed for producing dun 
 colours will be treated of, because their number is too great to 
 be examined in detail; and they resemble one another suffi- 
 ciently in their characters to render the observations made on a 
 few applicable to the whole. 
 
 CHAPTER I. 
 Of Wal'nui Peels, 
 
 It is known that walnut peels are white interiorly, but when 
 exposed to the air, they become brown, and then black. Hence, 
 if the skin has been impregnated with its juice, it soon assumes 
 a brown, and almost black colour. 
 
 If the internal part of fresh walnut peels be plunged into 
 chlorine, it becomes brown in like manner. 
 
 The filtered decoction takes a deep brown colour in the air ; 
 it yields pellicles on evaporation, which when separated, well 
 washed, and dried, are nearly black. The liquor freed from 
 these pellicles yields a brown extract, which may be completely 
 redissolved in water ; but by a new evaporation it still affords 
 pellicles similar to the first. 
 
 These pellicles, which are formed in several other evapora- 
 tions, are derived from the colouring substance, whose pro- 
 perties have been changed from an increase in the proportion of 
 carbon, by an agency which has been elsewhere explained. 
 
 Alcohol precipitates the colouring matter of the decoction of 
 walnut peels in the form of a brown substance, which may be 
 redissolved in water. 
 
 The solution of potash produces at first no sensible change in 
 
410 
 
 BERTHOLLET ON DYEING. 
 
 the decoction of walnut peels ; but by degrees it becomes a little 
 turbid, and its colour deepens. 
 
 Muriatic acid brightens up its colour, turning it yellow ; there 
 is formed a small quantity of a brown precipitate, and the liquor 
 remains of a clear yellow. 
 
 Solution of tin produces an abundant precipitate in the decoc- 
 tion of a dun ash-colour ; the liquor retains only a faint yellow 
 hue. 
 
 Solution of alum disturbed the liquor slightly ; a very small 
 deposite was formed of a dun brown. The liquor preserved a 
 clearer colour, but still dun. 
 
 Solution of sulphate of copper disturbed the liquor but very 
 slowly; a scanty green-brown precipitate was formed. The 
 supernatant liquid remained green. 
 
 Acetate of lead speedily formed an abundant deposite of a deep 
 dun colour. 
 
 Solution of sulphate of iron rendered the colour much deeper, 
 and even black. On diluting it with water, it passed through 
 brown to greenish-dun, but it let fall no deposite. 
 
 Solution of pure sulphate of zinc disturbed the liquor but 
 slightly, rendering the colour thereby deeper. 
 
 The decoction of walnut root presented nearly the same pro- 
 perties. On separating the bark from the ligneous substance of 
 this root, the former yielded in equal weight a liquor much 
 more charged with colour. The bark of the wood of walnut 
 also exhibited properties approaching to those of walnut peels, 
 but its decoction formed a blackish precipitate with sulphate 
 of iron. 
 
 Walnut peels exercise a lively action on oxyde of iron, dis- 
 solving it, and forming a liquor as black as ink. If boiled 
 along with clean filings, they do not attack them, but if 
 left exposed to the action of the air, the liquor becomes soon 
 black. 
 
 The colouring matter of walnut peels has a great disposition 
 to combine with wool. It gives it a very durable walnut or dun 
 colour, and mordants appear to add little to its permanence, but 
 they may vary its shades, and give them more lustre. By pre- 
 paring the stuff with alum, a richer and livelier colour may be 
 obtained. 
 
 Walnut peels are of excellent use, because they give agree- 
 
OF DUN. 
 
 411 
 
 able and very durable shades ; and being employed without any 
 mordant, they preserve the softness of the v^ool, and require but 
 one simple and not expensive operation. Walnut peels are 
 gathered when the nuts are entirely ripe. Large casks or tubs 
 are filled with them, and a sufficiency of water is poured on 
 them to cover their surface. In this state they may be kept a 
 year and upwards. At the Gobelins, where a very extensive 
 and varied use is made of this ingredient, it is kept for two 
 years before it is employed. It is found then to furnish much 
 more colour. It has a very unpleasant putrid odour. 
 
 The peels may also be used which are taken from the nuts 
 before they are ripe ; but they do not keep so long. 
 
 When it is wished to dye with walnut peels, they are boiled 
 for a full quarter of an hour in a copper, in quantity propor- 
 tioned to the amount of stuff*, and to the depth of shade that is 
 desired. For cloths, the deepest shades are usually begun with, 
 finishing with the lighter ones ; but for woollen yarn, it is com- 
 monly the clearest shades that we begin with, and the deepest 
 shades are made at the end, with the addition of husks for each 
 parcel. The woollen cloth and yarn ought to be simply moist- 
 ened with tepid water, before being plunged in the copper, in 
 which they are turned about with care till they have assumed 
 the desired shade, unless a preliminary aluming be given. 
 
 The root of walnut gives the same shades, but for this effect 
 the quantity must be increased. It must be reduced to chips ; 
 and it is proper to enclose it in a bag, to prevent the little chips 
 from sticking to the stuff*. The colour becomes often unevenly 
 with the formation of spots. To obviate this inconvenience, 
 the fire must be tempered at the beginning, that the colouring 
 particles may be equally distributed through the bath, in pro- 
 portion as they are extracted from the root. If some parts be 
 unequally dyed, as the colour is fast, there is no method of 
 remedying this accident except to reserve the stuff* for deeper 
 colours. 
 
412 
 
 BERTllOLLET ON DYEING. 
 
 CHAPTER II. 
 
 Of Sumach, and some other Substances capable of affording 
 a Dun Colour, 
 
 Common sumach (rhus coriaria) is a shrub which grows 
 naturally in Syria, Palestine, Spain, and Portugal. 
 
 It is diligently cultivated in Spain and Portugal. The shoots 
 are cut down to the root every year, then dried that they may be 
 ground to powder in a mill. This powder is employed by dyers 
 and tanners. The name of redoul or roudou is given to the 
 sumach cultivated in the neighbourhood of Montpellier. 
 
 The infusion of sumach is of a dun colour, bordering on 
 green. It speedily becomes green in the air. When it is 
 recent, the solution of potash produces little change on it. The 
 acids clear up its colour, and render it yellow. Solution of alum 
 makes it turbid, producing a scanty yellow precipitate, while the 
 liquor remains yellow. 
 
 Acetate of lead forms instantly an abundant yellowish pre- 
 cipitate, which takes a brown colour on its surface ; the liquor 
 remains of a clear yellow. 
 
 Sulphate of copper affords a copious yellowish-green precipi- 
 tate, which, after some hours, changes to a brown-green. The 
 liquor remained clear, and a little yellow. 
 
 Sulphate of zinc of commerce rendered the liquor turbid, 
 blackening it, and forming a deep blue precipitate. 
 
 Pure sulphate of zinc deepened the colour much less ; only a 
 slight dun deposite verging on brown took place. 
 
 Muriate of soda produced no sensible change at first; but 
 after some hours, the liquor was a little turbid, and its colour 
 had become somewhat clearer. 
 
 Sumach acts like nut-galls on solution of silver, whose metal 
 it reduces ; a result promoted by the action of light. We have 
 already dwelt at sufficient length on the explanation of this 
 phenomenon, as well as the general properties of astringents. 
 
 Sumach affords, of itself, a dun colour bordering on green ; 
 but it communicates to cotton stuffs several very permanent 
 colours when they are combined with mordants. 
 
OF DUN. 
 
 413 
 
 Thus, as we have already stated, it yields a black with acetate 
 of iron, if this has been printed on it in a state of concentration, 
 but shades of grey if it has been diluted with water. With 
 acetate of alumina it gives a durable yelloW, which retains some- 
 what of a greenish shade ; hence, if into the same pattern, 
 yellow, grey, and black colours are to be introduced, they may 
 all three be given by sumach. 
 
 To dye with this substance, the water must be heated to 
 about 145° Fahr., the sumach is then to be thrown in, and the 
 cloths immediately introduced, leaving them immersed only 15 
 or 20 minutes, with a slight elevation of the heat of the bath. 
 If the heat be too much raised, and if the cloths be left too long 
 in the boiler, the colours will become weaker instead of stronger ; 
 and even, in a little time, those that have iron for their mordant 
 disappear almost altogether. This effect, which occurs in a less 
 remarkable degree with many other dyes, requires us to catch 
 the v-ery instant for withdrawing the cloths when the colours are 
 sufficiently raised. To procure an evenly colour, only a small 
 number of pieces should be dyed at a time. 
 
 Cloths dyed with sumach resume a fine white with difficulty, 
 and are little improved by exposure on the grass. More effect 
 is produced by passing them through water sharpened with so 
 little sulphuric acid as to make it just perceptibly sour. By this 
 means the greys lose the russet tint which they have on coming 
 out of the boiler, and become agreeable. Blacks thereby acquire 
 a great deal of lustre. 
 
 We have said, in treating of greys, that by. alternately passing 
 the cotton through a decoction of sumach, much diluted with 
 water, and an equally dilute solution of iron, very agreeable 
 shades of grey are obtained, whose intensity depends on the con- 
 centration of the bath, and the number of times that the opera- 
 tions are repeated. In general, to dye equably in this way, 
 the colours must be slowly brought up, beginning with very 
 feeble baths, passing repeatedly through each of them, and gra- 
 dually increasing their strength when deep shades are wanted. 
 
 By finishing with the solution of sulphate of iron, the cotton 
 has not that russet hue which it takes when sumach is last 
 used, which it becomes necessary to remove with the acidulated 
 water. 
 
 With concentrated solutions of sumach and sulphate of iron. 
 
414 
 
 BERTHOLLET ON DYEING. 
 
 the cotton assumes a black colour when it has been turned 
 three or four times through each of them ; and if, on issuing for 
 the last time from the sulphate of iron, it be passed through a 
 tepid decoction of logwood, to which a little acetate of copper is 
 added, the black becomes brilliant and sufficiently fast. The 
 cotton is softened and the black heightened, by passing it 
 through hot water into which a little oil has been poured. 
 
 If, in dyeing grey, the decoction of logwood be mixed 'with 
 that of sumach, the grey becomes slate coloured ; if after this it 
 be passed through a very dilute decoction of weld, mingled with 
 alum, it inclines towards pearl-grey. 
 
 By substituting nut-galls for sumach, other shades are 
 obtained. 
 
 Cotton thus treated with the decoction of logwood and with 
 sulphate of iron, affords slate-greys of little permanence. 
 
 Decoction of quercitron produces American grey ; and if a 
 little alum and muriate of tin be mixed with it, instead of that 
 colour, an American green is produced. 
 
 With yellow wood, (fustic,) alder bark, &c. other colours are 
 obtained. By thus varying the colouring matters, and making- 
 use of sulphate of iron and alum, or muriate of tin, and com- 
 bining variously the order and number of the operations, as well 
 as the concentration of the baths, a great many shades may be 
 obtained on cotton, which are generally pretty fast. 
 
 This manner of dyeing, by passing alternately through the 
 mordant and colouring matter, is of advantage for procuring 
 uniform colours ; and it further presents great facilities for 
 attaining the wished-for shade, and for diversifying those 
 produced. 
 
 Birch tree bark, betula alha^ {Vaune of BerthoUet,) affords a 
 decoction of a clear dun hue, which becomes speedily turbid, 
 and brown in the air. It forms with solution of alum a pretty 
 copious yellow precipitate ; and with solution of tin, an abun- 
 dant precipitate of a clear yellow. It blackens the solutions of 
 iron, forming with them a tolerably copious precipitate ; hence 
 it contains much of the astringent principle. It dissolves a large 
 quantity of the oxyde of iron ; thence the use made of it in the 
 black vats, destined for dyeing (linen) yarns. It does not, how- 
 ever, possess the property of dissolving the oxyde of iron in the 
 same degree with the decoction of walnut peels. 
 
OF DUN. 
 
 415 
 
 Much use is made for ordinary stuffs in the East, of the 
 leaves of a shrub called Henna, {Hhenne,) which is of the 
 family of Salicaria. It was known to the ancients by the name 
 of Ciprus, and was employed for dyeing the envelopes of mum- 
 mies, in which its colour is still observable. 
 
 The leaves of this shrub, now cultivated in Egypt, are 
 bruised, after' being hastily dried. A paste is then made of 
 them, which is used for dyeing the nails and the palms of the 
 hands of a reddish dun, (a tawny hue.) 
 
 The powder of these leaves has an olive colour ; it yields by 
 boiling with water a very deep orange dun, very rich in colour- 
 ing matter. 
 
 Almost all vegetables contain, especially in their bark, more 
 or less colouring matter, capable of affording dun hues, inclining 
 to yellow, brown, red, or green. These colouring matters pre- 
 sent greater or less differences among each other, in reference to 
 their quantity and quality ; they further vary according to cli- 
 mate and the age of the vegetable. A great diversity of shades, 
 therefore, may be procured, by modifying the dun natural to 
 the vegetables, by means of different mordants. This has been 
 accomplished by Siefferts,*" and particularly by D'Ambourney.f 
 Thus in a great many experiments which the latter made? 
 employing the parts of different vegetables, and using different 
 mordants, the colours which he produced were, for the most 
 part, between yellow and brown, such as carmelites, olives, 
 cinnamons, and chestnuts. 
 
 The decoction of the greater part of vegetables, and especially 
 of barks, affords a colour, differing only in shade, and exhibits 
 with re-agents nearly the same characters : it forms a yellow 
 precipitate more or less deep with alum, and a clearer colour 
 with solution of tin. It acts on solutions of iron as an astrin- 
 gent. The decoction of walnut peels, however, produces a 
 peculiar effect with solutions of iron ; it assumes a very deep 
 colour, but no precipitate is formed even after two or three 
 days. Their decoction, as well as that of walnut tree bark, has 
 a powerful action on oxyde of iron ; it saturates it, forming a 
 black liquor ; and even if filings of iron be put into this decoc- 
 
 * Versucli^ mit einheinmischen Farbe Materien. 
 
 f Recueil des precedes et d'exp^riences sur les teintures solides, que nos vegetaux in- 
 digenes communiquent aux laines et aux lainages. 
 
416 
 
 BERTHOLLET ON DYEING. 
 
 tion exposed to the air, in two or three days it forms a black 
 liquor by means of the oxygen which it attracts from the atmo- 
 sphere. But if a decoction to which solution of sulphate of 
 iron has been added, be boiled, an abundant black deposite 
 instantly falls. It is only, therefore, in a trifling circumstance 
 that walnut peels, as well as walnut tree bark, differ from the 
 other substances which yield a dun colour ; yet its extractive 
 matter possesses in particular the property of becoming black 
 by the action of the air, and the pellicles formed when it is 
 evaporated, assume in a very marked degree the appearances of 
 a carbonized substance. 
 
 If the yellow colour produced by several vegetable substances 
 be compared with the dun which most of them afford, a close 
 relation will be found between these colours. There are even 
 some which may be referred equally to yellow and to dun. 
 There are duns which, by means of alum and solution of tin, 
 pass to yellow, and the yellow is very fast. The following dis- 
 tinction m.ay be laid down. The yellows are in general more 
 changeable, more apt to yield fugitive colours ; for which reason 
 the yellow colours must be fixed by means of mordants, whereas 
 the most part of dun coloured substances afford by themselves a 
 pretty permanent colour. 
 
 As the dun shades obtained from difierent substances vary to 
 a great extent, sometimes several of these substances are blended 
 in order to obtain a peculiar colour, and that in different pro- 
 portions. Other ingredients are also mixed with them, to modify 
 their colour and to render it faster. 
 
 Among these substances, there is still one which deserves 
 attention ; this is, sandal or sanders wood. 
 
 Three kinds of sandal wood are distinguished ; the white 
 sandal, the yellow, and the red. The last alone is employed in 
 dyeing. It is a solid, compact, heavy wood, imported from the 
 coast of Coromandel, which becomes brown on remaining ex- 
 posed to the air. It is usually employed in the state of a very 
 fine powder. It affords a colour dun, brown, and verging on 
 red. By itself it furnishes little colour, and it is said to harden 
 the wool. But its colouring matter dissolves better when mixed 
 with other substances, such as walnut peels, sumach, nut-galls. 
 Besides, the colour which it gives is permanent, and modifies ad- 
 vantageously the colours of the substances with which it is mixed. 
 
OF DUN. 
 
 417 
 
 Vogler, having observed that dilute alcohol or proof spirit 
 dissolved the colouring matter of sandal wood much better than 
 water, made use of this solution, either by itself or mixed with 
 from 7 to 8 parts of water, for dyeing patterns of wool, silk, 
 cotton, and linen, which he had prepared beforehand, by im- 
 pregnating them with solution of tin, washing and drying 
 them. These patterns took all a poppy-red colour. Patterns 
 prepared likewise with alum, took a saturated scarlet colour ; 
 prepared with sulphate of copper, a beautiful clear crimson hue ; 
 prepared with sulphate of iron, a fine deep violet colour.* He 
 dyed cold with the spirituous liquor; but employed a slight 
 ebullition for that which was mixed with water. This mixture 
 takes place without the transparency being disturbed. 
 
 Soot is also employed for giving to wool a dun or brown 
 colour, of greater or less depth according to the proportions of 
 this ingredient ; but soot gives only a fugitive colour, because 
 it simply adheres to the wool, instead of combining with it. It 
 hardens it, and leaves a bad smell. Tt is employed, however, 
 in some respectable manufactori-es, for browning certain colours ; 
 undoubtedly, because shades are thereby obtained, which could 
 be got with, difficulty by other means. 
 
 * Crell's Anuals, 1790. 
 
 2 E 
 
SECTION VL 
 
 OF COMPOUND COLOURS. 
 
 Simple colours form, by their mixture, compound colours ; 
 and, if the effects of the colouring particles did not vary, accord- 
 ing to the combinations which they form, and the actions exer- 
 cised on thpm by the different substances present in a dyeing 
 bath, we might determine with precision the shade that ought 
 to result from the mixture of two other colours, or of the 
 ingredients which afford these colours separately : but the che- 
 mical action of the mordants, and of the liquor of the dye bath, 
 often changes the results. Theory, however, may always predict 
 these effects to a certain degree. 
 
 It is not the colour peculiar to the colouring matters which 
 is to be considered as the constituent part of compound colours, 
 but that which they must assume with a certain mordant, and 
 in a certain dye bath. Hence, our attention ought to be prin- 
 cipally fixed on the effects of the chemical agents employed. 
 
 It is in this department of dyeing that the intelligence of the 
 operator may be most useful, by enabling him to vary his 
 processes, and to arrive at the proposed end by the simplest, 
 shortest, and least expensive way. 
 
 The processes for compound colours are very numerous. We 
 shall mention only those which most merit attention, and shall 
 establish the principle on which they ought to be conducted 
 by particular examples. Several of the processes described 
 in the course of this work afford compound colours. We 
 shall now consider, in an especial manner, this part of the art 
 of dyeing. 
 
COMPOUND COLOURS. 
 
 419 
 
 CHAPTER I. 
 
 Of the Mixture of Blue and Yellow, or Green, 
 
 Many different plants are capable of affording green colours ; 
 such as the field broom grass {bromus secalinus) ; the green 
 berries of the berry-bearing alder {rhamnus franguld)\ wild 
 chervil {chcerophyllum silvestre) ; purple clover {trifolium pra- 
 tense) common reed {arundo phragmites)\ but these colours 
 have no permanence, 
 
 D'Ambourney says, however, that he has extracted a durable 
 green from the fermented juice of the berries of the rhamnus 
 frangula : he prepared the cloth with tartar, nitric solution of 
 bismuth, and muriate of soda ; and he added to the fermented 
 and tepid juice of these berries a little acetate of lead. The 
 cloth took, in this bath, an intermediate shade between parrot- 
 green and grass-green. 
 
 Poivre, and some other writers, had announced, that there 
 existed in different parts of India a green fecula, or a kind of 
 green indigo, which would be precious to the dyer ; but some 
 trials of Bancroft seem to prove, that it was merely common 
 indigo united to a yellow substance. 
 
 By mixture of blue and yellow, dyers form green, which 
 is distinguished by a great number of shades. Address and 
 experience are required for obtaining this colour uniform, and 
 without spots, especially in the light shades. 
 
 The green*may be formed by beginning the dyeing either 
 with yellow or blue ; but the first method has some disadvantages ; 
 for the blue soils the linen, and a portion of the yellow, dissolv- 
 ing in the vat, alters, or makes it green. The second method is 
 preferred for woollen stuffs. 
 
 The pastel vat is usually employed ; but, for some kinds of 
 green, solution of indigo in sulphuric acid is used; in which 
 case, the blue and yellow are separately dyed, or indeed all the 
 ingredients may be mixed for dyeing at one operation. Finally, 
 solutions of copper, with yellow substances, are had recourse to. 
 We shall take a view of these different processes. 
 
 The blue ground which is given by the vat should be propor- 
 
 2 e2 
 
420 
 
 BERTHOLLET ON DYEING. 
 
 tioned to the kind of green that is wanted. Thus, for verd 
 canard, the green like that of drake's neck, a deep blue is 
 required; for parrot-green, a sky-blue ground; for verd nais- 
 ^ant, nascent green, one of white-blue {bleu hlanchi.) 
 
 When the cloths have undergone this operation, they are 
 washed at the fulling-mill, and a bouillon is given them as in 
 ordinary welding; but, for the lighter shades, the proportion of 
 salts is diminished. More frequently the bouillon for cloths 
 intended for light shades is first given ; and, after taking them 
 out, some tartar and alum are added : and this practice is pur- 
 sued until we come to the cloths destined for the deepest shades, 
 by the progressive addition of more tartar and alum. 
 
 The welding is conducted as for yellow ; but a greater quan- 
 tity of weld is employed, unless light colours alone are to be 
 dyed, for which the proportion ought, on the contrary, to be 
 ■ less. Usually a succession of shades is dyed at the same time, 
 from the deepest to the lightest ; beginning with the deepest, 
 and proceeding to the lightest. Between each dip, which lasts 
 half an hour, or three quarters, water is added to the bath. 
 KSome dyers pass each parcel twice through each bath. They 
 begin the first time with the deep shades, and the second with 
 the light ones. In this case, each parcel should remain a shorter 
 time in the bath. Care must be taken not to boil the bath for 
 very light shades. 
 
 A browning is given to the very deep greens, with logwood 
 and a little sulphate of iron. 
 
 It is still more difficult in silk than in cloth to prevent the 
 green from being spotted and variegated. Silk intended for 
 greens is boiled as for the ordinary colours; for- light shades, 
 however, it should be boiled thoroughly, as for blue. 
 
 Silk is not first dyed blue, like cloth ; but, after a strong 
 aluming, it is washed slightly in the river, and distributed into 
 small hanks, that it may take the dye equably ; after which it 
 is turned carefully round the sticks, through a bath of weld. 
 When it is thought that the ground is sufficiently deep, a pat- 
 tern is tried in the vat, to see if. the colour has the wished-for 
 tone. If it has not ground enough, decoction of weld is added ; 
 and, when it is' ascertained that the yellow has reached the proper 
 degree, the silk is withdrawn from the bath, and passed through 
 the vat, as for blue. 
 
COMPOUND COLOURS. 
 
 421 
 
 To render the colour deeper, and at the same time to vary its 
 tone, there are added to the yellow bath, when the w^eld has been 
 taken out, juice of brazil wood, decoction of fustet, and annotto. 
 For the very light shades, such as apple-green and celadon- 
 green, a much weaker ground is given than for the other colours. 
 For the light shades, if not for sea-green, it is preferable to dye 
 yellow in baths which have already been used, but in which 
 there is no brazil wood or fustet, because the silk, perfectly 
 alumed, dyes too rapidly in fresh baths, and is thence subject to 
 take an unevenly colour. 
 
 For dyeing green in raw silks, those naturally white are * 
 selected, as for yellow ; and, after being well soaked, they are 
 alumed, and treated in the same way as the other silks. 
 
 When the blue vat is used for dyeing green, saw-wort may 
 be employed instead of weld It is even preferable, because the 
 colour which it gives naturally inclines to green. Dyers' broom 
 is also employed; and sometimes these two ingredients are 
 mingled. Other substances which dye yellow may also be used ; 
 and a variety of shades may thus be procured. 
 
 The green obtained by means of solution of indigo in sul- 
 phuric acid, is known by the name of Saxon green. It has 
 more brightness, but less permanence, than that just described. 
 This process was first practised in Saxony, and government 
 caused a description of it to be published in 1750.* According 
 to this description, the cloth must be boiled with alum and tartar 
 for half an hour ; it is then to be withdrawn, and aired, without 
 washing. The bath is refreshed (with cold water), the solution 
 of indigo is well mixed with it, pouring in at first only the half; 
 the cloth is then let down, and turned rapidly through it, with- 
 out boiling, for five or six minutes. It is lifted out, that 
 the remainder of the solution may be poured in, which should be 
 mixed with great care. The cloth, being slightly boiled for 
 seven or eight minutes, is taken out and cooled. The bath is 
 emptied to about 3-4ths, more or less, according to the shade of 
 green that is wanted, and filled up with a decoction of fustic ; 
 and, when this bath is very hot, the cloth which had been dyed 
 blue, and cooled, is passed through it, till it has acquired the 
 wished-for shade. Cloth dyed blue in the bath with alum and 
 
 * Mani^re de teindie im drap blanc en vert, nomme vert de Saxe, 
 
422 
 
 BERTHOLLET ON DYEING. 
 
 tartar, has a less brilliant but more durable colour than when it 
 is made blue without this mixture. 
 
 Experience has taught that this process may be executed in a 
 more expeditious, and even more certain manner. The cloth is 
 boiled as for welding, and then washed. Some fustic, reduced 
 into chips, and enclosed in a bag, is put into the same bath. It 
 is boiled an hour and a half ; it is lifted up, and the bath is 
 refreshed, so that the hand can be kept in it; about li pound of 
 solution of indigo is poured in for every piece of cloth 24 yards 
 long which is to be dyed ; this is to be turned through quickly 
 at first, and afterwards slowly, and the cloth is lifted out before 
 the bath boils. 
 
 It is a proper practice to pour in, at first, only 2-3ds of the 
 solution, to lift up the cloth after two or three turns, and then 
 to add the remaining third. The colour is thus rendered more 
 uniform. If the colour seems not to take well, a little calcined 
 alum, reduced to powder, is added. Saxon apple-green is dyed 
 in the bath which has served for Saxon green, after a third or a 
 half of it has been thrown out, and after it has been refreshed. 
 The cloth is turned through it, till it approaches to ebullition. 
 
 It is easy to see that a great variety of greens may be pro- 
 duced, not only according to the proportions of the indigo and 
 yellow dyes employed, but according to the nature of the yellow 
 substance. For obtaining a decided green, however, fustic is 
 preferred to the other colouring substances, because its colour is 
 less affected by sulphuric acid, which clears up and impairs con- 
 siderably that of the other substances. 
 
 In order to avoid this effect with the quercitron, Bancroft 
 directs us to dye the stuff at first blue, to rinse it well in water, 
 and give it afterwards a bouillon composed of three parts of 
 washed chalk, and 10 or 12 of alum, for 100 of cloth. It is to 
 be boiled for an hour. Then, without changing the bath, 10 or 
 12 parts of quercitron are introduced, and the dyeing is con- 
 tinued. At the end of a quarter of an hour, one part of chalk 
 is added ; and this addition is repeated at intervals of six or 
 eight minutes, till a fine green colour is brought out. 
 
 Bancroft recommends, on several occasions, and other authors 
 do the same, to add carbonate of lime to the sulphate of alumina 
 (alum), for saturating the excess of acid in the latter ; but it is 
 merely the decomposition of a portion of the alum which is 
 
COMPOUND COLOURS. 423 
 
 thereby produced, and this decomposition is complete, if the 
 proportion of carbonate of lime be sufficient. The carbonic acid 
 is expelled ; the alumina precipitates, retaining a little sulphuric 
 acid ; and the sulphate of lime falls down in part, and is in part 
 held in solution, according to the quantity of water. The effect 
 which lime, or carbonate of lime, produces on alum must not 
 be confounded with that occasioned by potash or soda. 
 
 If a solution of alkali, deprived of carbonic acid, or even in 
 the state of a carbonate, be poured, by portions, into a solution 
 of alum, the small precipitate which occurs on the contact of 
 the (alkaline) liquid is immediately redissolved ; and it is only 
 when the acidity is nearly saturated by the alkali, that the pre- 
 cipitate ceases to disappear. But the combination, even when 
 neutral, retains a portion of alumina ; and, when the precipitate 
 has become permanent, it may be redissolved by a superabun- 
 dance of alkali. It is obvious, therefore, that alkali can enter 
 into combination with the sulphate of alumina (alum), and that 
 a change may thus be introduced into it favourable to the 
 operations of dyeing; whereas lime, and carbonate of lime, 
 produce the immediate separation and precipitation of the 
 alumina. 
 
 The sulphuric acid may be abstracted, in the process under 
 discussion, by boiling the stuff that has been dyed Saxon blue, 
 with carbonate of lime, before subjecting it to the bouillon of 
 alum. 
 
 It is mentioned, as a fault in Saxon blue, that it has a greenish 
 cast, proceeding probably from the slight alteration that sul- 
 phuric acid produces on the particles of indigo : it likewise, as 
 well as Saxon green, is said to have less durability than the 
 blues and greens obtained by means of the vat. It has been 
 attempted in England to procure the lustre characteristic of 
 Saxon blues and greens, by obviating the defects which accom- 
 pany them, and by combining the advantages of the blue vat 
 with those of the sulphuric solution of indigo. Guhliche de- 
 scribes a process for giving silk the English blue and green. 
 These two objects are here united, to serve as examples of the 
 different processes which may be practised. 
 
 He uses a cold vat for dyeing blue ; and he extols it highly 
 in respect of convenience, price, and beauty of colour. 
 
 This vat is composed of one part of indigo, three parts of 
 
424 BERTHOLLET ON DYEING. 
 
 good quicklime, or lime slaked in the air, three parts of English 
 vitriol, and one part and a half of orpiment. The indigo 
 ought to be ground with care, and diffused in water, then put 
 into a wooden vat, in which it is diluted with water to the 
 proper degree, according to the intensity of colour that is 
 wished for ; the lime is now added to it ; the mixture is well 
 agitated, covered up, and left at rest for some hours. The 
 vitriol, reduced to powder, is thereafter added ; the vat is stirred 
 well, and then covered up. After some hours, the orpiment, in 
 powder, is thrown in ; it is again left at rest for some hours ; 
 the mixture is now stirred, and then allowed to repose till the 
 supernatant liquid appears clear, when the froth that covers its 
 surface is put aside. The silk is now dyed in it hank by hank ; 
 but it must be previously passed through hot water. On com- 
 ing out of the bath, it is washed in running water, and dried. 
 When the bath becomes turbid, it is allowed to settle till it 
 grows clear ; an essential precaution for the light shades. When 
 it begins to be exhausted, one-third of the ingredients is added 
 to it, proceeding as at first. In proportion as the vat gets ex- 
 hausted, the shades become lighter. This vat serves equally 
 well for silk, linen, and cotton. Guhliche thinks that those 
 persons who have not succeeded in dyeing silk with the cold 
 vats, or who complain that only feeble hues are obtained, have 
 been led into an error by employing too small a quantity of 
 orpiment.* 
 
 For English blue, a light blue must be first given to the silk. 
 On being taken out of this bath, it is passed through hot water, 
 washed in running water, and put into a bath composed of 
 the sulphuric solution of indigo, to which a little solution of 
 tin has been added, till it has assumed the desired shade, or has 
 exhausted the bath. Before introducing it into this bath, it 
 may be passed through a solution of alum, in which it must not be 
 suffered to remain long. Silk dyed by this process has neither the 
 reddish cast of the indigo vat, nor the greenish cast of Saxon blue. 
 
 To make English green, which is more beautiful than ordi- 
 nary green, and more durable than Saxon green, Guhliche gives 
 
 * Guhliche uses for wool, a vat composed of one part of indigo, four parts of potash, 
 one part of quicklime, and a part and a half of orpiment. He follows the ordinary process, 
 only he keeps this last bath at a moderate heat. He uses it also, in the same manner, for 
 giving to cloth an English blue and green. 
 
COMPOUND COLOURS. 
 
 425 
 
 the siik, first of all, a clear blue in the cold vat; he steeps it 
 in hot water; washes it in running water; passes it through 
 a weak solution of alum ; prepares a bath with the sulphuric 
 solution of indigo, a little of the solution of tin, and a tincture 
 . of Avignon berry, made with a vegetable acid. ^ He keeps 
 the silk in this bath till it has assumed the wished-for shade ; 
 he then washes and dries in the shade. The lighter hues 
 may be dyed in the sequel. The shades may be varied with 
 more or less blue, more or less yellow, by the proportions of the 
 indigo solution, and of the yellow, substance. When it is 
 wished to give a gosling-green {verd d'oie) to silk, a light blue 
 is communicated to it, either in the hot vat or in the cold ; it is 
 passed through hot water, washed in running water, and, while 
 moist, it is passed through a bath of annotto. 
 
 To give a green colour to linen and cotton yarns, it is proper 
 to begin with scouring them well ; then they must be dyed in 
 the blue vat, cleansed in water, and passed through the welJ 
 process. 
 
 The strength of the blue and the yellow is proportioned to the 
 colour that is wanted. As it is difiicult to give uniformity to 
 the cotton velvets in the ordinary blue vat, they are usually 
 dyed yellow with curcuma (turmeric), and the green is produced 
 with solution of indigo in sulphuric acid. It is of no conse- 
 quence whether the blue or yellow be first given. 
 
 Le Pileur d'Apligny describes a process for dyeing of a water- 
 green, or apple-green, by a single bath, cotton velvet as well as 
 cotton hanks. 
 
 Verdigris is to be mixed with vinegar. The mixture is to be 
 kept well corked for 15 days in a stove. Four hours before 
 using it, there is added a solution of a quantity of crude pearl 
 ashes, equal to that of the verdigris ; and the mixture is kept 
 warm. The yarn or the velvet is prepared by soaking in a hot 
 solution of alum, at the rate of an ounce of this salt and 8^ pints 
 of water to one pound. The stuff is lifted out, the verdigris 
 liquor is added to the bath, and it is immersed again in order to 
 be dyed. 
 
 All the shades of olive and drake's-neck green are made by 
 giving to the yarns a blue ground, galling them, and passing 
 them through the bath from the black cask,* of greater or less 
 
 * See page 227. 
 
426 
 
 BERTHOLLET ON DYEING. 
 
 strength, then through the bath of weld with verdigris, and after 
 this through a bath of sulphate of copper. Lastly, the colour 
 is brightened by means of soap.- 
 
 Chaptal obtains beautiful greens on cotton by the following 
 processes. 1. He passes the cotton, dyed sky-blue, through a 
 strong decoction of sumach, leaving it in it till the decoction be 
 well cooled. He dries it, passes it through the mordant of 
 acetate of alumina, dries again, washes, and works the cotton 
 for two hours in a tepid bath, in which about 26 i pounds 
 of quercitron have been infused for 110 pounds of cotton. 
 
 2. For 220 pounds of cotton, he mixes 110 pounds of alum, 
 22 of sulphate of copper, 22 of sulphate of iron, 16 J of acetate 
 of lead, 3 of soda, and as much chalk. He passes the cotton 
 dyed blue through this, then through lime water, and afterwards 
 through a bath of quercitron. 
 
 Chaptal has remarked, that the yellow of weld unites ill with 
 that of sumach, and that the mixture of their colours gives a 
 bad tint to blue ; but that, on passing the cotton afterwards 
 through a ley marking 12 degrees, the colour becomes uniform, 
 and is pretty fast. The colour of weld unites perfectly to that 
 of tan. He prefers, however, to dye cottons intended for green 
 in a blue vat, mounted with sulphuret of arsenic (orpiment), 
 because it is difficult to obtain a fine green if there be in the 
 vat too large a proportion of sulphate of iron. 
 
 When a green ground is wished for upon cloth, acetate of 
 alumina is printed on, and a reserve is applied to the parts that 
 are to remain white, or to those already covered with alu- 
 mina, which are to take only a yellow colour. The piece is dyed 
 blue, washed with great care to remove all the reserve, and then 
 dyed in weld. It often happens, that the parts of the design 
 which should remain white, take colour in the welding, because 
 the salts of copper and the pipeclay, which constitute the 
 reserve, enter into combination with the cloth. It might be 
 first dyed yellow, but it then becomes impossible to restore the 
 reserve exactly. When there is but little white in the design, 
 the reserve is applied with the pencil. 
 
 If with yellow, green, and blue colours, others produced by 
 madder are to be mixed, these should be finished before giving 
 the blue dye. 
 
 When the objects to be dyed green are small, or of an irre- 
 
COMPOUND COLOURS. 
 
 427 
 
 gular form, like leaves or flowers, the blue is put on with the 
 pencil, after finishing all the colours. The green is often made 
 on common cloths, by applying the blue over the rust-yellow, or 
 this over the blue. Thus a sombre green, inclining to yellowish- 
 green, is formed, which is seldom evenly. The difficulty with 
 which the two colours combine prevents this method, other- 
 wise economical, from being employed for dyeing cotton in 
 hanks. 
 
 Cotton, which has received, a blue with prussian blue, may be 
 dyed green, according to the process described in Sect. II. 
 Chap, V, of the Second Part. The piece, while still moist with 
 the blue, is alumed,* and passed through a bath of weld, of 
 greater or less strength, according to the shade. Weld causes a 
 livelier colour than old fustic, which deepens more, but deadens 
 a little the vivacity of the blue. If a green, inclining to olive, 
 be wanted, yellow wood (fustic) is preferable. It is dried in the 
 open air, as for blue. 
 
 We have described in the same place, the process by which a 
 beautiful blue may be obtained from the combination of prus- 
 siate of iron with the stuff". This process applied to cotton, 
 previously dyed olive, by means of alumina and oxyde of iron 
 used as mordants, and a yellow colouring substance, affords a 
 more beautiful green than what can be procured by any other 
 method. In this operation, the iron combines with the prussic 
 acid, forming blue, while the alumina constitutes a yellow with 
 the colouring substance. Bancroft was correct in combating the 
 explanation given of this formation of green, in which the co- 
 operation of alumina was not introduced.f 
 
 This green, which resists well the action of light and air, is 
 destroyed by alkalies ; and the observations made on blue must 
 be applied to it. 
 
 The green obtained by giving a yellow colour to a stuff* which 
 has been previously dyed blue, and afterwards washed, presents 
 nothing obscure. The colour inclines more or less to yellow, 
 or to blue, according to the tint of blue given, and the strength 
 of the yellow bath. The intensity of the yellow is increased 
 by alkalies, by sulphate of lime, by ammoniacal salts. It is 
 diminished by acids, alum, and solution of tin. The shades 
 
 * L'art du fabriquant de velours de colon. 
 
 f Annal. dc chim. torn. xiii. 
 
428 BERTHOLLET ON DYEING. 
 
 vary likewise from the nature of the yellow substance em- 
 ployed. 
 
 These different effects will be obtained with the same ingre- 
 dients in the formation of the Saxon green, according to the 
 process adopted. If the Saxon blue be first dyed, and the 
 yellow colour be next given separately, the effects will be ana- 
 logous to those just mentioned ; but, if solution of indigo be 
 mixed with the yellow ingredients, the results are not the same, 
 because the sulphuric acid acts in this case on the colouring 
 particles, impairing the intensity of the yellow. 
 
 It has been formerly remarked, that the sulphuric acid re- 
 tained by the stuff in the Saxon blue, produced this effect always 
 to a small extent: which makes fustic be preferred to other 
 articles for this species of dyeing. 
 
 When a suite of shades is to be dyed in a bath composed of 
 yellow and solution of indigo, the latter incline more and more 
 to yellow, because the molecules of the indigo attach themselves 
 to the stuff, in preference to the yellow, which thereby becomes 
 predominant in the bath. 
 
 Although the sulphate of copper, and even the verdigris, 
 sometimes used, principally for dyeing linen and cotton, possess 
 in themselves a blue colour, they give, however, to the stuff a 
 greenish shade, because the oxyde of copper which fixes on it, 
 assumes this colour in several circumstances, and particularly 
 when exposed to the atmosphere. This colour is changed to an 
 olive hue, by means of a yellow substance. 
 
 CHAPTER 11. 
 
 Of the Mixture of Red and Blue. 
 
 From this mixture are obtained violet, purple (columbine), 
 dove-colour, pansy, amaranth, lilac, mallow, and a great many 
 other shades, determined by the nature of the substances 
 whose red colour is combined wath a blue colour, of which one 
 becomes more or less predominant over the other, according to 
 the proportions of the ingredients, and the other circumstances 
 of the process. 
 
COMPOUND COLOURS. 
 
 429 
 
 Stuff dyed scarlet, takes, according to the observations of 
 Hellot, an unequal colour, when blue is to be united with it. 
 It is proper, therefore, to begin with the blue ground, which, 
 even for violet and purple, ought not to be deeper than the 
 shade denominated sky-blue. A bouillon is given with alum, 
 mixed with two-fifths of tartar ; the stuff is next passed through 
 a bath composed of nearly two-thirds as much cochineal as for 
 scarlet, to which tartar is always added. The purple process 
 is distinguished from the violet one, because, for the first, a 
 lighter blue ground is given, and a somewhat greater proportion 
 of cochineal is employed. These colours are often dyed in the 
 sequel of the reddening bath of scarlet, by adding the quantities 
 of cochineal and tartar deemed necessary. The operation is 
 conducted in the same manner as for scarlet. 
 
 Lilacs, pigeon-necks, mallows, &c., are passed usually through 
 the bouillon that has served for violet, with the addition of alum 
 and tartar. The blue ground is proportioned to the shade 
 wanted, as well as the quantity of cochineal. For some reddish 
 shades, as peach-blossom, a little solution of tin is added. It 
 may be remarked, that, although the quantity of cochineal is 
 diminished when a light shade is wished for, yet the quantity 
 of tartar is not ; so that its relative proportion to the cochineal 
 is greater, the lighter the colour. is to be. 
 
 Poerner conceives, that, in order to obtain the colours which 
 result from red and blue, there is an advantage in using solu- 
 tion of indigo in sulphuric acid, because a great variety of 
 shades may more easily be procured, and because the process is 
 not so long or expensive. But the colours thereby obtained 
 are less durable than when the blue vat is employed. He says, 
 however, that they have sufficient permanence, if a solution of 
 indigo be used to which some alkali has been added. 
 
 The effects may be easily varied, by giving a preparation to 
 the stuff with different proportions of alum and tartar, or with 
 solution of tin ; and by dyeing with different proportions of 
 cochineal and solution of indigo. 
 
 In silks, two kinds of violets are distinguished ; the fine 
 violet and the spurious. The last is made either with archil 
 or brazil wood. 
 
 For fine violet, the cochineal dye is first given, and the vat is 
 then used. The silk is prepared, and receives the cochineal as 
 
430 
 
 BERTHOLLET ON DYEING. 
 
 for crimson, — with this difference, that neither tartar nor soki- 
 tion of tin, which serve to heighten the colour, is put into the 
 bath. More or less cochineal is introduced, according to the 
 intensity of the shade that is wanted. The ordinary dose for a 
 fine violet is an eighth of cochineal to one of silk. When the 
 silk is dyed, it is washed, with two beetlings, in the river ; it is 
 next passed through a vat of greater or less strength, according 
 to the depth which the violet is to have ; and lastly, it is washed 
 and dried with the precautions proper for all colours that are 
 dyed in the vat. In order to give more strength and beauty to 
 the violet, it is usually passed through the archil bath ; and this 
 practice, frequently abused, is indispensable for the light shades, 
 because the colour would otherwise be too dull. 
 
 When silk has been dyed with cochineal, as above directed, a 
 very light shade of blue must- be given it for purple. Only 
 the deepest shades are passed through a weak vat. For those 
 which are less so, cold water is had recourse to, into which 
 a little of the blue vat is put, because they would take too much 
 blue in the vat itself, however weak it may be. The light shades 
 of this colour, such as pink, gridelin, and peach-blossom, are 
 made in the same manner, with a diminution of the proportion 
 of cochineal. 
 
 The spurious violets are given to silk in various ways. The 
 most beautiful, and those most in use, are prepared with archil. 
 The strength of the archil bath is proportioned to the colour 
 wished for : the silk, to which a beetling in the river has been 
 given on its coming out of the soap, is turned through it round 
 the skein sticks. When the colour is thought to be deep enough, 
 a trial is made on a pattern in the vat, to see if it takes the 
 violet that is wanted. If it is found to be at the proper pitch, a 
 beetling is given to the silk at the river, and it is passed 
 through the vat as for fine violets. Less blue, or less archil, is 
 given, according as the violet is wished to incline to red or 
 to blue. 
 
 Beautiful violets may be produced on silk by means of solu- 
 tion of indigo ; but they have little permanence, and become 
 reddish, because the colour of indigo fades first. 
 
 A violet is made on silk by passing it through water in which 
 verdigris has been dissolved, instead of the aluming; after 
 which a bath of logwood is given. It here takes a blue colour. 
 
COMPOUND COLOURS. 
 
 431 ' 
 
 which IS converted into violet, either by adding alum to the 
 bath, or by passing it thrdugh a solution more or less charged 
 with alum, which serves to give a red colour to the particles of 
 the logwood. It is needless to observe, that this violet is very 
 fugitive, and of but moderate beauty. One is made possessing 
 more beauty, and to which much intensity can be given, by 
 passing the alumed silk through a bath of brazil wood, and, after 
 washing it in the river, through a bath of archil. 
 
 Madder also is had recourse to for dyeing cloth after giving 
 it a blue ground. By this means are obtained couleur du roi, 
 minime, and dull amaranth. Nut-galls are usually joined to the 
 madder, and for light shades brazil wood. A browning to a 
 greater or less degree is given to the deep shades with solution 
 of sulphate of iron. These colours are more beautiful when 
 kermes, and particularly cochineal, are mixed with the madder. 
 
 By employing solution of indigo with madder, in the same 
 way as with cochineal, brown colours may be formed, according 
 to Poerner, which incline more to red the less solution of indigo 
 is employed. Alum and tartar may serve for the preparation, 
 but alum should not be put into the bath. 
 
 Poerner employs brazil wood, and solution of indigo, for 
 obtaining different colours, which incline more or less to blue 
 and red, by a process similar to that pointed out for cochineal 
 and madder. These colours are beautiful ; but it is needless to 
 expect durable colours by this method. The ingredients which 
 procure the greatest fixity to them are sulphate of lime, sulphate 
 of zinc (white vitriol), acetate of copper (crystals of verdigris), 
 which must be added to the bath. 
 
 Logwood is, moreover, had recourse to for obtaining sloe, 
 damascene, purple, as well as other shades. This wood, joined 
 to nut-galls, communicates all these colours with much facility 
 to wool previously dyed blue. When it is wished to brown 
 them, they are let down again with a little sulphate of iron, by 
 which means shades are obtained which are more difficult to hit by 
 more durable ingredients, but they have little permanence. Fast 
 colours, which have been much esteemed, have, however, been 
 obtained from logwood and fernambucca. To Descroizilles, 
 who is engaged in the arts with the intelligence of a skilful 
 chemist, we owe the following details on the process employed, 
 of which incorrect descriptions have been given. 
 
432 
 
 BERTHOLLET ON DYEING. 
 
 Giros de Gentilly," wrote he to the author of the former 
 edition, is the first who gave success in France to the durable 
 dye with violet wood fixed by solution of tin. He made the 
 first trials at Louviers with MM. Petou (the nephew) and Fri- 
 gard, about twelve years ago. From what he suffered to 
 transpire concerning the ingredients of his mordant, I suc- 
 ceeded in a tolerable imitation. I made a solution of tin in 
 sulphuric acid, then added muriate of soda, red acidulous tar- 
 tarate of potash, and sulphate of copper. My success was 
 sufficiently great to induce Giros to propose a partnership with 
 me in the very lucrative business which he carried on at Lou- 
 viers, Elbeuf, Abbeville, Sedan, and in the Pays de Liege. 
 Giros then taught me a much more convenient method of effect- 
 ing this combination. It consists in making a solution of tin in 
 a mixture of sulphuric acid, muriate of soda, and water. To 
 this solution the tartarate and the sulphate were added in pow- 
 der. We made no less than 375 gallons of this mordant in 24 
 hours, in a single vessel of lead moderately heated. We con- 
 tinued this very profitable trade at the rate of 15 pence per 
 pound for three years, after which it went on declining, till we 
 lost it altogether. The following was the cause of this : Giros 
 having allowed his secret to transpire, we had imitators, who 
 made it at first worse, afterwards better, than we did. In a 
 composition so complex as this, in an operation so obscure as 
 the fixation of colouring matters, it is almost impossible to 
 attain perfection otherwise than by groping our way {tatonne- 
 ments) amid trials which may be indefinitely varied by the 
 respective doses, and especially by the modus agetidi ; and this 
 much more than could at first be imagined by chemists who 
 have not been so long occupied with this object as myself. I 
 do not blush, therefore, to acknowledge, that I was forced to 
 abandon this trade, whilst I saw, and still see, persons who are 
 in no respect chemists deriving a creditable profit from it. 
 What led me to give it up entirely was the invention of the new 
 process of bleaching goods, to whose improvement I have almost 
 entirely devoted myself. 
 
 " After thus giving you the history of the mordant of the 
 prune de monsieur, I present you with the following account of 
 its employment and effects : — 
 
 If it be wool in the fleece which is to be dyed, one-third 
 
COMPOUND COLOURS. 
 
 433 
 
 of its weight of mordant is required ; if it be a woven stuff, only a 
 fifth is necessary. A bath is prepared at a temperature which 
 the hand can bear ; the mordant is well mixed with it ; and 
 the wool or ^tuff is then immersed. It is to be properly agitated, 
 and the same degree of heat is to be kept up for two hours, 
 which may be even increased a little towards the end. It is 
 then lifted out, aired, and very well washed. A new bath of 
 pure water at the same heat is prepared ; a sufficient quantity 
 of violet wood is added to it ; the stuff is then let down, and 
 agitated; and the heat is urged to the boiling point, at which it 
 is maintained for a quarter of an hour. The stuff is then lifted 
 out, aired, and carefully rinsed. The dye is now completed. 
 If a decoction of one pound of logwood has been used for three 
 pounds of wool, (and proportionately for the stuffs which require 
 a smaller dose,) a beautiful violet is obtained, to which a suffi- 
 cient quantity of brazil wood gives the shade known by the name 
 o? prune de monsieur, 
 
 " The colouring matters succeptible of being fixed with advan- 
 tage on wool by this mordant are those of violet and red woods, 
 as also the wood of fustet. Yellow wood (fustic) affords likewise 
 tolerable colours. The colours thus given by the violet and red 
 woods may be afterwards affected by soap or urine in the ful- 
 ling ; and this change, always produced by alkaline substances, 
 may be remedied by a bath very slightly acid, and a little more 
 than lukewarm, called the brightening {avivage,) Sulphuric 
 acid is preferred. The colour comes out as deep, and often more 
 brilliant than before this alteration. Wools dyed with this mor- 
 dant are capable of being spun into more beautiful and finer 
 thread than when alum has been used. By omitting the sulphate 
 of copper, we obtain from fustet and fustic, as well as from weld, 
 more beautiful colours. Madder gives in this case a red-orange 
 colour, but not so deep as with an equal dose of alum. The 
 omission of the sulphate of copper renders the wools much 
 harsher; and besides, the mordant so prepared affords only 
 paltry colours with logwood, and particularly with red wood. 
 One of the great defects of this mordant, before it had been 
 improved, was, and occasionally still is, to make the colours 
 unevenly ; whenever they are uniform, they are very beautiful, 
 very harmless, and very soft. This process succeeds equally 
 well on silk. By substituting acetate of lead for sulphate of 
 
 2 F 
 
43i 
 
 -BERTHOLLET ON DYEING. 
 
 copper, it succeeds tolerably well with cotton and linen yarn pre- 
 viously galled. The employment and carriage of this mordant 
 are inconvenient, on account of the dense deposite, which half 
 fills the vessel under a corrosive liquid, which can be kept only 
 in hard stoneware. I possess, however, a method of obviating 
 these inconveniences, by omitting entirely the water in the 
 receipt ; by which means I have merely a kind of paste, of a 
 much more commodious employment, and two-fifths cheaper 
 in the carriage. Now that the muriate of soda is low-priced, 
 it may happen that I shall recommence furnishing our dyers 
 with this mordant, which is better, in my opinion, than what 
 they are at present getting, and especially much cheaper. But 
 before doing so, I must devote myself for some time, still, to the 
 composition and employment of your lixivium." 
 
 For fixing on silk the colour of brazil and logwood, Fabroni 
 has given a process which we shall copy from Hermstadt. It 
 has a good deal of resemblance to that of Descroizilles. It con- 
 sists in employing as a mordant, a mixture of muriate of tin, 
 sulphate of copper and tartar. Infusion of nut-galls or alder- 
 wood bark is added to the bath. The proportions of these sub- 
 stances are varied according to the shade that is wanted. For 
 light shades, a little muriatic acid is added. 
 
 When the sulphuric solution of indigo is employed, the sul- 
 phuric acid acts differently according to the red substance that 
 is used. It changes very little the colour of cochineal, which 
 had, indeed, a tendency to take a crimson colour by the pre- 
 paration with alum ; but it must give a dun colour to madder, 
 on which the acids readily produce this effect ; and it is impro- 
 bable that this substance could be successfully employed in 
 this process. It would be better to have recourse to it for 
 dyeing stuff* to which a blue ground had been previously given. 
 Brazil wood and logwood must also be ill qualified to afford 
 beautiful colours with the sulphuric solution of indigo, because 
 the acids make them turn yellow, although in a less decided 
 manner ; but they retain, as we have already remarked, their 
 red colour, when their colouring particles are precipitated by 
 oxyde of tin. 
 
 If we may venture an opinion, without having made direct 
 experiments on a complicated process, such as that communi- 
 cated by Descroizilles, and which is still employed advantage- 
 
COMPOUND COLOURS. 
 
 435 
 
 ously in some manufactories with modiJfieations which ^e do 
 not know, we would suggest the following explanation. 
 
 The muriate of soda is decomposed by the sulphuric acid, 
 and the muriatic acid set at liberty dissolves the tin. 
 
 A portion of the tin is precipitated by the tartaric acid, 
 whence the deposite is occasioned. But a portion which remains 
 in solution serves to modify the effect, as we have seen with 
 regard to cochineal. The oxyde of copper present in this pre- 
 paration, forms blue with the colouring particles of the indigo ; 
 the oxyde of tin with the same wood gives violet, and red with 
 the colouring matter of brazil wood. Descroizilles observed, 
 that a preparation capable of accomplishing this object could 
 easily be obtained, by trying different mixtures, and different 
 proportions, with the muriate of tin : this is what Fabroni has 
 done. 
 
 This direct mixture of the blue and red colours gives to 
 cotton yarn and cloth only a sombre hue without lustre, approach- 
 ing to black, provided these colours be somewhat deep. But if, 
 after giving a light blue to cotton stuff, we dye it of a rose 
 colour with carthamus, a brilliant deep blue is produced, which 
 fades pretty quickly, from the little permanence of the colour 
 of carthamus. 
 
 Chaptal has, however, obtained a tolerably agreeable violet, 
 by dyeing^ red cottons blue, in the preparation of which he 
 diminished the quantities of oils and nut-galls, and, on the 
 other hand, increased that of alum, as well as the brightening 
 process. He attempted, by a great many experiments, to give 
 cotton a violet colour, which would yield neither in durability 
 nor in lustre to the red made in his dyehouses ; and after 
 having been led by his researches to a great variety of pro- 
 cesses, which afforded with more or less facility the colour 
 which he wished, he preferred the following, as being the 
 simplest and most certain in the execution. 
 
 The mordant for 220 pounds of cotton, is prepared with 55 
 pounds of sulphate of iron, and 13 pounds of acetate of lead. 
 The clear liquid is to be separated from the deposite that is 
 formed ; and the cotton is passed through it with the greatest 
 care, after receiving three oils, as for the Adrianople red, as hot 
 as possible. On taking it out of the bath, it is wrung and well 
 
 2 F 2 
 
436 BERTHOLLET ON DYEING. 
 
 worked : whenever it has assumed, on cooling, the buff shade, 
 it is well washed, wrung out, and dried with accurate stretching. 
 
 Its own weight of madder is employed for dyeing : as soon 
 as the bath becomes tepid, the cotton is plunged in, and 
 turned about, with gradual increase of the heat, but without 
 boiling. When the cotton has become blueish-black, it is taken 
 out, and washed. It is thereafter brightened in soap, during 
 fifteen or twenty minutes. 
 
 For deep violet, he takes cotton which has received only two 
 oils ; he passes it through the same mordant with the same care. 
 He adds a pailful of blood to the madder bath, and takes out 
 the cotton when it is about to boil, washes it, and madders 
 a second time with double its weight of madder, and a pailful of 
 blood. He lets the bath boil for a quarter of an hour ; and after 
 washing the cotton, he brightens it with 88 pounds of soap, 
 causing the brightening process to boil for a quarter of an hour, 
 and sometimes more than an hour, as he perceives the colour to 
 be impoverished, or to take lustre. 
 
 By adding 1 1 pounds of alum to the preceding mordant, the 
 violet is more brilliant. H^ used with advantage the solution 
 of iron in pyrolignous acid. 
 
 For procuring uniform colours which penetrate thoroughly, 
 he recommends us to employ the mordant very limpid, and as 
 hot as possible ; to wash it on taking it out of the mordant ; to 
 dry quickly and equally; but not to let the madder bath boil, 
 when it is wished to preserve the lustre of the dye. Lastly, he 
 observes, that soda makes the colour turn red, and that soap 
 gives predominance to the blue ; hence, by employing different 
 proportions of these substances, the shades of the cotton may 
 be varied in the brightening, and blackish cottons may, for 
 instance, be restored to violet by using leys only, whilst if they 
 incline to red, soap alone ought to be used. 
 
 To produce violets on printed calicoes, the acetate of iron 
 diluted with water is impressed, and they are maddered. This 
 colour is less easily degraded in the dyeing bath than the reds. 
 It may also be kept boiling for a longer time, so as to raise the 
 deep shades. The bath becomes very foul ; the colour comes 
 out of it very dull, and assumes lustre only by exposure on the 
 grass, and ebullition with bran water ; it is even rare for the 
 
COMPOUND COLOURS. 437 
 
 white to become beautiful again. But these inconveniences are 
 obviated by dunging with a strong heat, which acts less upon 
 this moi'dant than upon that employed for the reds. 
 
 For lilac, a mordant is printed on, composed of very dilute 
 acetate of iron, mixed with a small quantity of acetate of alu- 
 mina. 
 
 Cotton in hanks dyed by the same processes, with difficulty 
 takes an agreeable shade ; and the colour never has the pernia« 
 nence of that produced by the processes of Chaptal. The most 
 ordinary method of dyeing linen yarn and cotton violet, consists 
 in giving first a blue ground in the vat, proportioned to the 
 shade wanted, and then to dry it. It is next galled at the rate 
 of 3 parts of nut-galls for 16 parts of the matter ; it is left for 
 twelve or fifteen hours in the bath of galls ; after which it is 
 WTung out, and dried. The linen yarn and cotton are thereafter 
 passed through a decoction of logwood, and when it is well 
 soaked, it is lifted out, and there are added to this bath l-60th 
 of alum, and 1 -128th of verdigris, both in solution. The hanks 
 passed over the sticks are re-immersed, and they are turned 
 round them for a full quarter of an hour. They are now taken 
 out to let them be aired ; they are then replunged completely 
 into the bath for a quarter of an hour ; after which they are 
 lifted out and wrung. Lastly, the vat which has served for this 
 dye is emptied ; there is poured into it one-half of the decoction 
 of logwood, which was reserved; as much alum is added as in 
 the first operation ; and the yarn is once more passed through, 
 till it be of the suitable shade. The decoction of logwood 
 should be more or less rich, according to the depth of shade 
 wanted. This violet resists the air tolerably well, but it cannot 
 be compared in durability to the dyes above described, or even 
 to the following: — 
 
 The cotton or linen yarn is scoured as usual ; a mordant is 
 prepared, composed of seven pints of acetate of iron, and nearly 
 two gallons of water for every two pounds. This is boiled, and 
 the scum which rises is removed. When no more froth appears, 
 the liquor is poured into a vat, and whenever it is merely tepid, 
 4i ounces of sulphate of copper, and about an ounce of salt- 
 petre, are dissolved in it. After this, the hanks are allowed to 
 soak in it during ten or twelve hours, when they are wrung 
 out and dried. When it is wished to madder them, they aro 
 
438 
 
 BERTHOLLET ON DYEING. 
 
 washed with care, and passed through a madder bath. If the 
 violet is to be deep, two ounces of verdigris are added to the 
 mordant. The colour may be still further deepened by galling 
 the yarn more or less before passing it through the mordant, 
 and by leaving out the saltpetre. If the dose of the latter 
 substance be increased, and that of the sulphate of copper be 
 diminished, the violet inclines more towards the lilac. The 
 mordants may be still modified in different manners, so as to 
 produce a great many shades. 
 
 CHAPTER III. 
 
 Of the mixture of Red and Yellow, 
 
 In treating of cochineal, we thought it improper to separate 
 the operations which usually succeed one another in the dye- 
 houses, and therefore the principal shades obtainable by the 
 mixture of the red of cochineal with yellow have been already 
 described. The shades may receive an infinity of modifications 
 from the different proportions of the ingredients ; from the 
 yellow substances made choice of, from the preparations given 
 to the cloth, and from the mordants added to the dye-baths. 
 Thus Poerner describes a great many varieties which he obtained 
 by employing weld, saw-wort, dyers'- broom, and some other 
 yellow substances ; as also by introducing into the preparation 
 of the cloth, or into the bath, tartar, alum, sulphate of zinc, or 
 sulphate of copper. 
 
 Different colours may in like manner be procured from 
 the madder which is associated with yellow substances. It is 
 thus that the chocolates and the cinnamons are dyed; colours 
 commonly formed in two baths. The maddering is first given, 
 preceded by a bouillon of alum and tartar as for ordinary mad- 
 dering ; and then a bath of weld is employed. 
 
 For cinnamon a weaker maddering is given, and commonly a 
 bath is used which had served for the chocolate. The propor- 
 tions are varied according as the red or the yellow is wished to 
 predominate. Sometimes nut-galls are added, and sometimes 
 the colour is deepened by a browning. 
 
COMPOUND COLOURS. 
 
 439 
 
 Occasionally the sole object is to give a reddish tone to 
 the yellow ; the stuff just dyed yellow may, in this case, be 
 passed through a bath of madder, more or less charged according 
 to the intention. 
 
 Brazil wood is likewise employed along with the yellow sub- 
 stances, and sometimes it is associated with cochineal and 
 madder. 
 
 When, instead of weld or other yellow substances, root of 
 walnut, walnut peels, or sumach, are used, tobacco, snuff, chest- 
 nut, musk colours, &c. are produced. 
 
 The chestnuts, the cinnamons, and all the intermediate shades, 
 are formed upon silk by means of logwood, brazil wood, and 
 fustet. 
 
 The silk is boiled as usual, then alumed, and a bath is prepared 
 by mixing the decoctions of the above three woods, which have 
 been separately made. The proportion of each is varied accord- 
 ing to the desired shade ; that of fustet ought, however, to pre- 
 dominate. The bath should be of a moderate temperature. The 
 silk is turned round the skein sticks, and when its colour is uni- 
 form, it is wrung out, and passed through a second bath of the 
 three ingredients, so proportioned to the effect of the first bath 
 as to obtain the shade wanted. 
 
 The mixture of red and yellow requires no peculiar observa- 
 tions in addition to those which have been detailed in the two 
 preceding chapters. 
 
 For some colours, blue is blended with red and yellow ; thus 
 olives are made. A blue ground is given, then the yellow bath 
 is used, and lastly, a slight maddering is employed. The shade 
 resulting from this operation depends on the proportion of the 
 three colours of which it is composed ; for the deep shades, 
 a browning is given with a stronger or weaker solution of sul- 
 phate of iron. 
 
 The blue vat is not used for producing the olives on silk ; but 
 after the aluming, the silk is passed through a very strong bath 
 of weld : some logwood is then added to this bath, and whenever 
 the silk is turned through it, a little alkaline solution is poured 
 in, which turns it green, and makes the cloth take an olive hue. 
 The silk is passed again through this bath, till it has taken the 
 proper shade. For the colour termed russet olive, or rotten olive, 
 fustet and logwood, without alkali, are added to the bath after 
 
440 
 
 BERTHOLLET ON DYEING. 
 
 the welding. If a more reddish colour be wished for, only log- 
 wood is added. A kind of reddish olive is also made by dyeing 
 the silk in a bath of fustet, to which more or less sulphate of 
 iron and logwood are added. 
 
 According to Le Pileur d'Apligny, a fine olive is formed on 
 linen yarn and cotton, by boiling, in a sufficient quantity of 
 water, four parts of weld with one of potash ; brazil wood, 
 soaked the evening before, is boiled apart with a little verdigris : 
 the two solutions are mixed in different proportions, according 
 to the shades wanted, and the thread or cotton is passed through 
 the mixture. 
 
 The colours which result from the mixture of yellow with 
 red, as coquelicot, (poppy-red,) brick, capuchin, &c., are obtained 
 in calico printing by means of weld and madder. Acetate of 
 alumina is printed on as the mordant ; and a slight maddering, 
 with a welding finish, is given. 
 
 To vary the shades, it is sufficient to increase or diminish 
 the duration of one of the two dyeing operations, or the pro- 
 portion of the materials employed. These processes are appli- 
 cable to the dyeing of cotton in hanks, (cotton yarns.) 
 
 CHAPTER IV. 
 
 Of the Colours resulting from the mixture of Black with other 
 Colours^ and of Brownings. 
 
 The processes by which the degradations of black are obtained 
 that form the different shades of grey, have been already de- 
 scribed. It has been shown, that dissimilar {etrangeres) shades 
 might be blended with them, so as to cause them to incline 
 towards certain colours ; but the black is often employed for cer- 
 tain colours which are to remain predominant, and which should 
 be merely browned. At the same time they become more durable. 
 In the course of this work it has been frequently stated that a 
 browning was imparted to certain colours; but this chapter 
 is destined to treat peculiarly of this operation, and of the 
 resources which it presents- to the art, sometimes for the imitat- 
 
COMPOUND COLOURS. 
 
 441 
 
 mg colours that can be obtained by other means, and sometimes 
 for producing new colours. 
 
 To give a browning, the stuff just dyed is passed through a 
 solution of sulphate of iron with which an astringent is mixed, 
 and which consequently forms a black bath. More frequently 
 there is added to a water bath a small quantity of solution of 
 iron ; and just so much is introduced as to make the dyed stuff 
 attain the wished-for shade. More rarely, some sulphate of 
 iron is added to the dyeing bath. But the desired effect is 
 obtained with more precision by passing the coloured stuff 
 through solution of sulphate of iron. Poerner often macerates 
 the stuff in a solution of sulphate of iron, to which other ingre- 
 dients are sometimes added ; and on its quitting this mordant, 
 he passes it through a dyeing bath. 
 
 The first method is employed for chestnuts, coffees, damas- 
 cenes, and other brown shades of the common dye ; greater or 
 less depth of colour is given, according to the colour wished to 
 be obtained by the browning ; a bath' is next made with nut- 
 galls, sumach, and alder bark, to which sulphate of iron is 
 added. The stuffs which are to be lightest coloured are first 
 passed through ; and when they are finished, those that are to 
 be browned are dipped, adding at each operation a quantity of 
 sulphate of iron proportioned to the purpose in view. 
 
 The other brownings offer nothing peculiar in the operation. 
 We shall select some examples of the effects that are obtained, 
 and point out some particular processes. 
 
 It has been stated in the first Section of this Second Part, 
 that for several kinds of grey a slight blue ground is given. 
 Poerner makes blueish-greys by employing sulphuric solution of 
 indigo, which he adds to a decoction of gall-nuts with sulphate 
 of iron ; and he varies the shades by the different proportions of 
 these three ingredients. He procures other shades by adding 
 sulphate of iron to a bath composed of cochineal, fustic, and 
 gall-nuts. 
 
 For couleur du roi, a sky-blue ground is given with pastel ; 
 the dyeing is performed with weld and a sixth of gall-nuts, 
 and a browning is imparted with the solution of sulphate of 
 iron. 
 
 Chestnut, and the colours approaching it, are made with 
 sandal-wood, gall-nuts, and a browning; sometimes fernam- 
 
442 
 
 BERTHOLLET ON DYEING. 
 
 bucca (brazil-wood) is added. To these colours a cast of purple 
 and crimson is given, by dyeing them in the remains of a cochi- 
 neal bath, with the addition of a little madder and cochineal 
 to the bath. The colour is rendered lighter by means of a 
 little tartar. 
 
 For the hazel colours, gall-nuts, fustic, and logwood are 
 blended, to which more or less madder, and a little alum, 
 are added. 
 
 Logwood and brazil wood, being employed in equal parts, or 
 in other proportions, afford different browHr colours of tolerable 
 durability, when more or less solution of iron is mixed with 
 their decoction, and when the wool, previously alumed and 
 galled, is dyed in it. These colours cannot be compared, how- 
 ever, with the preceding, in respect to permanence. 
 
 To the above colours, different shades of mordores and capu- 
 cine may be given, by passing them through a bath of annotto 
 on their coming out of the dye. 
 
 A great variety of shades are obtained by the mixture of 
 brazil-wood, logwood, archil, gall-nuts, and by browning with 
 sulphate of iron ; but these shades are all more or less fugitive, 
 although they possess an alluring lustre. 
 
 When a stuff which has received a colour is passed through 
 a black bath more or less dilute, the effect obtained is simple ; 
 a black shade, more or less deep, is blended with the first 
 colour. 
 
 This is not the case when the coloured stuff is passed through 
 a solution of sulphate of iron : here the colouring particles that 
 are fixed on the stuff act on the sulphate of iron, seize a portion 
 of its oxyde, combining it with them and with the stuff. The 
 colour that results from this combination is more or less deep, 
 not according to the colour peculiar to the colouring particles, 
 but principally according to the action which they exercise on 
 the metallic oxyde, agreeably to the principles laid down in the 
 First Part. Thus the brazil wood and logwood, which enter 
 into the composition of a colour, will produce a much more ^ 
 marked effect in the browning than madder and cochineal-, nut- 
 galls and sumach will occasion a still more considerable one, 
 although they had affected the primitive colour only by a dun- 
 coloured shade. 
 
 If a black bath be prepared, or a black dye be formed, 
 
COMPOUND COLOURS. 
 
 443 
 
 either in the mordant, or in the dyeing bath, the ingredients 
 which are mixed with the colouring substances modify the result 
 of the operation, by the action which they exercise on the black 
 molecules : thus alum, solution of tin, solution of indigo, will 
 impair the effect that the black molecules would have produced. 
 All the acids act in the same way, excepting acetic acid, and some 
 analogous vegetable acids, which do not possess the property of 
 dissolving the black molecules. It appears that nitre can dis- 
 solve them, since it renders the colours for which it is employed 
 lighter. 
 
 As the best colours that can be given to linen and cotton are 
 derived from madder^ attention must be paid to the methods 
 described, in treating of madder, for rendering this dye more 
 durable, and its colour may be deepened by different black 
 baths. 
 
 For some hazels and snuff-colours, a browning is given, after 
 the welding and the madder bath, with soot, to which gall-nuts 
 and fustic are joined. Soot is sometimes mixed with this bath, 
 and a browning is moreover given with solution of sulphate 
 of iron. 
 
 Walnut peels are occasionally substituted for solutions of 
 iron, in browning colours. They have a great advantage for the 
 wools intended for tapestry. The colour does not become yel- 
 low by long exposure to the air, as happens to the brownings 
 from iron ; but it keeps long without alteration. It has, indeed, 
 a dull tone, suitable for shadows, and for representing the flesh 
 in old figures, which would produce merely gloomy colours, 
 without lustre, on cloths. The goodness of this colour, however, 
 and its cheapness, ought to extend its use for the sombre colours 
 which are sometimes in fashion, at least on common stuffs. 
 
 A great number of shades are made at the Gobelins by means 
 of this browning. To procure an assortment of them, a houillon 
 is first given to the woollen yarns with tartar and alum, of 
 different degrees of strength, according to the shades required ; 
 they are then successively dyed red, yellow, or some other 
 colour, recurring to the bath from which most effect is wished 
 to be obtained. When the colour is found to be of the desired 
 shade, it is passed, for a shorter or longer time, through the 
 bath of walnut peels, of a strength adjusted to its purpose. 
 This browning is likewise had recourse to for silk ; but the 
 
444 
 
 BERTHOLLET ON DYEING. 
 
 bath must be hardly tepid, in order to avoid the inequalities to 
 which it is so liable. 
 
 For the different shades of chestnut, the cotton is galled, 
 passed with the ordinary manipulation through water into which 
 a greater or less quantity of acetate of iron has been poured. 
 It is next worked in a bath in which verdigris has been dis- 
 solved ; and a welding is given it. It is dyed in a bath of fustic, 
 to which solution of soda and alum are sometimes added. When 
 the cotton which has received these preparations has been well 
 washed, a good maddering is given it. It is then passed through 
 a weak solution of sulphate of copper, and lastly through soap 
 water. 
 
 The cinnamon and chocolate colours are given to linen and 
 cotton, by commencing the dyeing with verdigris and weld ; they 
 are next passed through a solution of sulphate of iron, which is 
 called the security bath, {bain d'assurage,) and they are wrung 
 out and dried. When dry they are galled in the proportion of 
 two ounces of gall-nuts per pound ; they are once more dried, 
 alumed as for red, and maddered. When they are dyed and 
 washed, they are passed through very hot soap water, in which 
 they are turned round the sticks till they are sufficiently 
 brightened. Decoction of fustic is sometimes added to the 
 aluming. 
 
 By taking cotton which had received the requisite prepara- 
 tions for the Adrianople red, and had been galled, then pass- 
 ing it through nitrate of iron, galling it anew and aluming, 
 Chaptal obtained a pretty nacarat. He prepares the nitrate of 
 iron with the aquafortis of commerce, diluted with half its 
 weight of water, into which he plunges fragments of iron, which 
 he removes whenever he perceives the solution slackening. The 
 liquor is now of a yellowish-red, strongly acid, and marks from 
 76^ to 108° Twaddell. 
 
 If, after galling the cotton that has passed through the oils, 
 it be alumed in a bath to which one-eighth of this solution 
 of iron, for one of cotton, is added, the cotton comes out 
 black, and takes a violet sloe colour by the maddering and 
 brightening. 
 
 Chaptal obtains a succession of shades by passing the cotton, 
 which has received two or three oils, through a mordant com- 
 posed of alum, sulphate of iron, and acetate of lead, and by 
 
COMPOUND COLOURS. 
 
 445 
 
 varying the proportion of the salts which enter into its compo- 
 sition. Thus, with three parts of alum, two of acetate of lead, 
 and one of sulphate of iron, maddering twice, and brightening 
 with 55 pounds of soap, he produces a sloe colour, inclining 
 towards red. He had, on the other hand, a sloe verging towards 
 violet, by galling with nut-galls and sumach, passing through a 
 mordant prepared with 4 ounces of sulphate of iron, 4 ounces 
 of alum, 2 ounces of acetate of lead, 1 ounce of muriate of 
 ammonia, and as much soda dissolved in 4 pounds six ounces 
 of water, maddering, passing through a boiling ley which 
 marked 2^, and brightening with soap. 
 
 He took advantage of the difficulty with which alumed and 
 dried cotton is impregnated with water, for dyeing it at once of 
 two colours, which produce the effect of small cliinures (veins ?) 
 very close together, and very irregular. With this view, after 
 having galled, alumed, and dried the cotton which had been 
 treated with the oils, he washed it and dried it anew ; then he 
 passed it slightly through one of the above mordants. The 
 down alone (on the surface) is coloured black, and the thread 
 remains grey : after the maddering and brightening, the latter is 
 red, and the dow^n has assumed a violet colour. Cottons dyed 
 in this manner have a very agreeable appearance. Employed 
 in weaving, they produce cloths whose reflections vary, and take 
 different tints, according to their relative position, and that of 
 the dye. 
 
 In the manufacture of printed calicoes, colours are obtained 
 from madder, which result from the mixture of red and black. 
 For mordants, mixtures, in different proportions, of acetate of 
 iron and acetate of alumina, are employed. 
 
 By printing on a mordant composed of equal parts of 
 oxydized acetate of iron (black bouillon) and acetate of alumina, 
 both concentrated, a deep chocolate is obtained with madder. 
 One part of acetate of iron, and two of acetate of alumina, 
 afford a less sombre chocolate, inclining towards puce-coloured. 
 On augmenting the quantity of acetate of alumina, the shade 
 approaches more and more to red ; and on introducing, at last, 
 only 1-1 2th of acetate of iron, an amaranth colour is obtained. 
 If, on the contrary, the .proportion of acetate of iron be increased, 
 browns are produced. • 
 
 This colour is that which requires most madder. It may be 
 
446 
 
 BERTHOLLET ON DYEING. 
 
 boiled longer than for the reds, but not so long as for the violets, 
 because, as the portion of the colouring matter which is com- 
 bined with the alumina does not stand a prolonged ebullition 
 so well as that which has the oxyde of iron for a mordant, the 
 shade is degraded, and there is obtained only a poor and un- 
 equal colour, instead of a substantial and well raised one. 
 Great care should also be taken to put into the bath a suf- 
 ficient quantity of madder, so as to saturate all the mordant ; 
 otherwise a uniform colour can never be obtained, for the 
 bath becomes exhausted, and some parts of the cloth would 
 be saturated before other parts had been able to assume 
 the proper shade. For conducting the operation properly, and 
 for completely saturating the mordant, the madder ing should 
 be given at two times. The bath is scarcely suffered to boil 
 the first time, and from the hue that the cloth has taken, the 
 quantity of madder to be employed at the second maddering 
 may be determined. When the cloth is to have, besides choco- 
 late, fainter colours, they should not be printed on till after the 
 first maddering, because the heat of the bath in the double mad- 
 dering would degrade them. 
 
 The chocolates have a more agreeable hue, when, previous to 
 maddering, they have been dyed with nearly half the quantity 
 of weld or quercitron which would have been used had they been 
 dyed with these substances alone. The mordants for chocolate 
 and puce afford, with both these substances, the shades of olive, 
 bronze, terre d'Egypte, &c. In this case, it is sufficient for 
 restoring the white, to pass through bran on their quitting the 
 boiler, and to expose them for about eight days on the grass, 
 lifting them once in this interval in order to wash and beetle 
 them. The colour has more lustre when, before drying the 
 cloth, we pass it through water acidulated so slightly with sul- 
 phuric acid, as to be hardly perceptible to the taste. 
 
 These processes may be employed for dyeing cotton in hanks. 
 The greatest precaution should then be taken to impregnate and 
 dry the cotton very equably ; for many difficulties are encoun- 
 tered in preventing some parts from being unequably charged 
 with the one mordant or the other. 
 
NOTES, 
 
 ILLUSTRATIVE AND SUPPLEMENTARY, 
 BY THE TRANSLATOR. 
 
NOTES. 
 
 Note A. p. 33. 
 
 The green of plants, whose colour Mr. Bertholet regards as simple, is a 
 substance which has been lately examined, under the name of Chlorophile, 
 by MM. Pelletier and Caventou. They obtained it by pressing, and then 
 washing in water, the substance of many leaves, and afterwards treating it 
 with alcohol. A matter was dissolved, which, when separated by evapora- 
 tion, and purified by washing in hot water, appeared as a deep green 
 resinous substance. It dissolves entirely in alcohol, ether, oils, or alkalies; 
 it is not altered by exposure to air ; it is softened by heat, but does not 
 melt ; it burns with flame, and leaves a bulky coal. Hot water slightly 
 dissolves it. Acetic acid is the only acid that dissolves it in great 
 quantity. If an earthy or metallic salt be mixed with the alcoholic solu- 
 tion, and then alkali or alkaline subcarbonate be added, the oxyde or 
 earth is thrown down in combination with much of the green sub- 
 stance, forming a lake. These lakes appear moderately permanent when 
 exposed to the air. Chlorophile is supposed to be a peculiar proximate 
 principle. 
 
 Note B. p. 45. 
 
 Messrs. Thenard and Roard published, in the Annales de Chimie, vol. lix., 
 a very interesting memoir on mordants, in which the effects of alum, acetate 
 of alumina, tartar, and the solutions of tin, upon vegetable and animal sub- 
 stances, are examined and analyzed. This memoir is translated into the 
 39th vol. of Tilloch's Magazine. 
 
 Prior to their experiments, it had been generally supposed that, in the 
 process of aluming, the alum was decomposed, and that the alumina com- 
 bined with the stuff, thereby causing it more readily to take the colour 
 when plunged into the dyeing bath ; but Messrs. Thenard and Roard came 
 to a different conclusion. 
 
 2 G 
 
450 
 
 NOTES. 
 
 Analysis of the Aluming of Silk, 
 
 One thousand four hundred and seventy-five grains of silk, well cleaned, 
 and perfectly purified, were infused in a glass vessel during six days, at 
 the common temperature of the atmosphere, with four quarts of distilled 
 water, containing 1550 grains of pure alum, which had been previously 
 dissolved in it. After standing this time, the silk was taken out of the 
 liquid, drained completely over the bath, and washed several times with 
 distilled water, to separate that part of the mordant which had not com- 
 bined with it. The alum bath and the washings were then evaporated 
 with the greatest care, and they afforded very transparent crystals of 
 alum. These first products indicated pretty clearly the nature of the 
 combination which had been formed with the silk during the steeping, and 
 that the alum had not been decomposed. The alumed silk was then 
 boiled in a matrass with six quarts of distilled water, the boiling liquor 
 was poured off from it ; and in this manner it was treated twelve times. 
 The 72 quarts proceeding from these operations being evaporated, we 
 obtained well formed crystals of alum, the quantity of which, added to 
 that obtained from the bath, amounted to about 3 grains of the 1475 
 grains originally employed, forming a loss of part only. If after 
 each of the twelve washings we attempt to dye the silk, the colour is less 
 deep in proportion to the number of washings, so that after the twelfth the 
 silk is not at all coloured. If the silk, after having thus been washed, 
 is again impregnated with alum, it reacquires the same property of retain- 
 ing the colour which it liad before the washing commenced. Hence 
 results a very natural explanation of the reason why alumed silks take a 
 deeper colour when the dyeing is commenced at a low temperature, than 
 when they are plunged into boiling baths ; it is because, in the one case, 
 the action of the boiling water upon the mordant is so speedy that there 
 is not time for the colouring matter to fix upon it and render the combina- 
 tion insoluble ; whilst, in the other case, no such effect takes place. 
 
 Analysis of the Impregnation of Wool with Alum, 
 
 After having thus ascertained the phenomena which take place in the 
 aluming of silk, it was necessary to continue the trials upon wool, and to 
 employ for these experiments only perfectly pure materials, completely 
 deprived of the carbonate of lime, which is generally contained in con- 
 siderable quantity. To separate the whole of this, we boiled the wool 
 several successive times, in a matrass with weak muriatic acid ; but in 
 order to take up the last portions of this acid, we were obliged to make 
 use of such large quantities of distilled water, that we were on the point 
 
NOTES. 
 
 451 
 
 of abandoning such tedious experiments, requiring so much time and pa- 
 tience, as well as the greatest care. The separation of all the muriatic acid 
 from the first seven ounces of wool which w^e purified, required 200 quarts 
 of distilled water, at 212° Fahr., divided into twenty successive operations, 
 each occupying from seven to eight hours. When calcined and properly 
 tried, it afforded neither lime nor muriatic acid. 
 
 Three ounces and a half of this wool were alumed with the same care 
 which had been taken with the silk. It was afterwards washed twenty 
 times, employing six quarts of distilled water, heated to 212°, for each 
 washing. Immediately after the aluming, this wool took a very deep 
 colour, whilst after the last washing, it would not take any more colour in 
 the dyeing bath, than some of the same wool which had never been 
 alumed. These experiments convinced us, that the substance which had 
 been fixed in the wool by aluming, and had caused it to receive so deep a 
 colour in the first dyeing, had now been carried off by the water. The 
 alum bath, when evaporated, afforded us, in the state of crystals, two- 
 thirds of the quantity of alum we had originally employed ; very nearly 
 the whole of the remaining third part was obtained from the residue of the 
 bath, in an uncrystallized state, and from the washings of the wool. This 
 experiment was repeated several times, and always with the same result ; 
 but as this did not appear to us so decisive as the experiment upon silk, 
 on account of the difficulty of separating the animal matter from the last 
 portions of the alum bath, we alumed some wool in the cold as we had 
 done with the silk, and we obtained from the bath and the washings the 
 alum employed in the operation, with a loss only of 40 o part : we were 
 therefore assured, that in the aluming of all animal substances, the alum 
 combines entirely with them, without undergoing any decomposition, and 
 that it forms with them combinations more or less soluble, which have a 
 great affinity for the colouring matters. 
 
 Analysis of the Impregnation of Cotton and {Linen) Thread with Alum. 
 
 Having freed some cotton, by the methods already mentioned, from all 
 foreign matters, we macerated it for two days in a lukewarm solution of a 
 given quantity of alum. After this operation, the stuff took the dye re- 
 markably well ; but being treated with boiling distilled water, it lost the 
 property of taking the colour in the dye bath. The alum bath and wash- 
 ings, when evaporated, afforded us all the alum we had employed. We 
 separated this alum from the vegetable matter which it had dissolved in 
 its different crystallizations. To do this, did not require such a number of 
 washings as were employed for the wool or the silk, because the com- 
 bination of alum with vegetable substances is so weak, that soaking the 
 
 2 G 2 
 
452 
 
 NOTES. 
 
 alumed cotton in boiling water for a few minutes, is sufficient to carry off 
 the greatest part of the mordant. Cotton, therefore, ought to be dyed at a 
 low temperature, since it is only after tlie colouring matter has rendered 
 the combination insoluble, that it can support a great heat without being 
 attacked. Thread treated in the same manner as cotton, afforded us the 
 same results. 
 
 Analysis of the Impregnation of common Wool, 
 
 The analyses we have already related most decidedly demonstrate, 
 that in the aluming of all animal and vegetable substances, the alum com- 
 bines with them without undergoing any decomposition ; but we thought 
 it was necessary to repeat the same experiments upon these substances, in 
 the state in which they are commonly met with in commerce, as we had 
 done in their purified state. Wool, when impregnated with alum alone, 
 always renders the bath turbid, which, upon cooling, throws down an 
 abundant white precipitate, as has been observed by several chemists. 
 Several analyses of this sediment, after being well washed, have constantly 
 afforded us some sulphate of lime, saturated sulphate of alumina, and some- 
 times a little alumina. The bath contained a remarkable quantity of alum, 
 of acidulated sulphate of potash, combined with a small proportion of 
 animal matter. Upon the wool we found alum, and a very minute pro- 
 portion of the precipitate. These experiments upon the sediment formed 
 in the alum bath, do not differ from those made by M. Berthollet j but 
 this learned chemist not having examined the mother waters, nor the 
 alumed wool, has not given, as he himself says, a clear and precise ex- 
 planation of the effects produced by alum and tartar in the operation of 
 dyeing. These precipitates, obtained by treating common wool with alum, 
 never take place with purified wool ; and as these only differ from each 
 other by the former containing some carbonate of lime, it was natural in 
 this case to attribute to this substance the decomposition of a part of the 
 alum. 
 
 We satisfied ourselves of this, by mixing in glass vessels solutions of 
 alum in boiling water, with different proportions of pure carbonate of lime. 
 We always found the alum was decomposed by the carbonate of lime, and 
 that if a sufficient quantity was added, there remained no part of the alu- 
 minous salt in solution. The mother waters contained very acid sulphate 
 of potash, and the sediment was formed of sulphate of lime and acidulate 
 sulphate of alumina and potash ; whence it follows, that the property pos- 
 sessed by common wool, of forming a precipitate in the alum bath, and 
 rendering the fluid very acid, is in reality owing to the carbonate of lime 
 it contains. The same result was obtained by aluming common wool five 
 or six successive times in the same bath. But in order to arrive at a 
 
NOTES. 
 
 453 
 
 general solution of this question, it was necessary to ascertain the nature 
 of the precipitates formed in the solution of alum, by dilFerent alkaline and 
 earthy substances. We took, therefore, alums with base of potash, and 
 with base of ammonia, which we treated with ammonia and carbonate of 
 potash, so as to leave in the solution but a slight excess of alum. The 
 mother waters evaporated, contained very acid sulphates of ammonia, of 
 potash and ammonia, and of potash, according to the nature of the alum 
 and of the precipitate employed. The sediment, which was acid sulphate 
 of alumina and potash, or ammonia, treated with sulphuric acid, afforded 
 alum and acidulated sulphate of alumina ; boiled afterwards a great num- 
 ber of times with distilled water, it was converted into alum, sulphate of 
 potash, and pure alumina. There was always a greater quantity of acidu- 
 lated sulphate of potash than of alum, even in the last washings. 
 
 Solutions of alum, treated at a boiling heat with pure alumina, were 
 converted into a very acid sulphate of potash, and into acidulated sul- 
 phate of alumina and potash. These results do not at all correspond with 
 those obtained by M. Vauquelin in his experiments upon the alums of 
 commerce, for we have never been able to obtain the saturated sulphate' 
 of alumina and potash, spoken of by that celebrated chemist. 
 
 Thus all the alkaline and earthy substances mixed in suitable propor- 
 tions with solutions of alum, converted that salt into acidulated sulphate 
 of potash or ammonia, and into insoluble acid sulphate of alumina and 
 potash, or ammonia, for which reason we have named it the acidulated 
 sulphate, instead of the saturated sulphate, the name it has borne until 
 now. It is evident, that if too great a quantity of carbonate of lime be 
 employed, and the same holds good with the carbonates of barytes and 
 strontian, we shall only obtain alumina and the sulphates of potash, lime, 
 barytes, or strontian. There remains no doubt, therefore, of the nature 
 of the changes produced in the alum baths by the common wools, and of 
 the prejudicial effects of alkalies in the baths intended for cottons ; for 
 the addition of these substances dim.inishes the quantity of alum, and 
 even increases the acidity of the bath. 
 
 On the Impregnation of Vegetable and Animal Matters ivith Acetate 
 
 of Alumina, 
 
 Wool, silk, cotton, and thread, in the different states in which these 
 substances are employed for dyeing, were treated with acetate of alumina, 
 which combined entirely with them. But as in exposing them to the air, 
 or to a temperature a little elevated, the mordant always loses a small 
 quantity of acid, it follows that the combination formed upon the stuff 
 is an acetate with excess of base : thus, by treating it with boiling water 
 
454 
 
 NOTES. 
 
 it is converted into acidulated acetate of alumina, which is dissolved, and 
 into alumina which cannot be carried off by the water. 
 
 Of the action of Acidulated Tartrate of Potash on WooL 
 
 Purified wool was treated, as in the former experiments, with very pure 
 cream of tartar, free from tartrate of lime, and formed directly by the tar- 
 taric acid and potash. This wool was washed a great number of times, 
 until the last washing did not contain any of the principles which had 
 been combined with it. The bath afforded, by evaporation, three-fourths 
 of the cream of tartar employed, or rather neutral tartrate of potash. The 
 washings were very acid, and we obtained from them a small quantity of 
 cream of tartar, and a very acid composition, formed of tartaric acid and 
 wool. These facts may be thought sufficient to explain the phenomena 
 which take place in impregnating wool with alum and tartar, since we 
 already know, from the experiments of M. Berthollet, that these two salts 
 are not decomposed ; and as we have shown that the wool combines com- 
 pletely with the alum, and that it acts upon the cream of tartar by sepa- 
 rating the tartaric acid, with which it unites in the most intimate manner. 
 But in order to have these facts rigorously demonstrated, we repeated this 
 experiment, although a very tedious one, in the method already pointed 
 out in the preceding chapters. 
 
 Of the action of Alum and Tartar upon WooL 
 
 Before treating the wool with alum and cream of tartar, we made some 
 trials of the reciprocal action of these two salts. We ascertained that 
 water, at the temperature of 12° or 14° (65 F.°), holds in solution only 
 rko part of its weight of cream of tartar ; that boiling water dissolves ^ 
 of its weight, and that a mixture of equal parts of alum and cream of 
 tartar dissolves in f the quantity of water required to dissolve the salts 
 separately at the same temperature. These results do not differ from 
 those already obtained by M. Berthollet, who has shown that alum has 
 the property of increasing the solubility of cream of tartar. 
 
 If wool is alumed in the ordinary proportions, which are \ of the weight 
 of the stuff of alum, and of cream of tartar, all the substances being 
 perfectly pure, we obtain from the bath, when evaporated, alum, cream of 
 tartar, and a residue difficultly crystallizable, composed of tartrate of pot- 
 ash and an animal matter : the washings of the wool will give alum, a 
 small quantity, scarcely appreciable, of cream of tartar, and a very acid 
 combination, formed of a large quantity of tartaric acid, alum, and animal 
 matter. 
 
NOTES. 
 
 455 
 
 These experiments remove all uncertainty concerning many practical 
 facts, which at present are only noticed by the dyer in a vague way, and 
 point out to him the precise method of applying the mordants, according 
 to the nature of the colour he wishes to obtain. Indeed, since by making 
 use of alum and tartar, the wool is impregnated with alum and a large 
 quantity of tartaric acid, these two salts should never be employed toge- 
 ther, except where the colour is susceptible of being heightened and ren- 
 dered brighter by acids, as is the case with cochineal, madder, and kermes. 
 On the contrary, alum should never be employed for wools intended to be 
 dyed with woad or brazil wood, the colour of which is easily altered or 
 destroyed by acids. Among all the vegetable and animal substances, we 
 have made choice of wool only for trial with alum, and alum and tartar, 
 because it is only with this substance these mordants are made use of 
 in dyeing. 
 
 On the action of Acids, and of some Salts employed as Mordants upon 
 
 Wool 
 
 Although all researches hitherto made have been ineffectual to find a 
 substitute for alum, we have nevertheless made trial of a great number of 
 substances with wool ; less, however, for the purpose of discovering the 
 best mordants, than for determining the action of several substances very 
 soluble, and at the same time endowed with great powers. We boiled 
 wool for two hours in water, in which were put small quantities of sul- 
 phuric, nitric, muriatic, and tartaric acids. In each instance, the wool, 
 especially when combined with sulphuric acid, struck with cochineal and 
 madder deeper colours than when impregnated with alum and tartar. No 
 doubt, therefore, can be entertained of their superiority in similar cases ; 
 but of all the mordants we tried, there is not one which gives such bright 
 colours as what are obtained by means of the acid tartrate of alumina, 
 (notwithstanding the opinion of M. Haussman to the contrary.) This 
 salt would, in a great number of cases, be preferable to tartar and alum, 
 if its price was not so much higher than theirs. Whilst we were occupied 
 in inquiring with the greatest care into every thing relative to the nature 
 and mode of combination of mordants with various stuffs, we did not 
 forget to examine the several methods which have been adopted in the 
 workshops for a long time past, in order to ascertain if the proportions 
 of alum and tartar, the most generally employed, were those the most 
 suitable for the purpose ; if the time employed for the alum bath was 
 sufficient properly to impregnate the wool ; and if the exposure to the 
 cool air afterwards, for several days, which is so generally thought neces* 
 sary, is attended with the expected advantages. 
 
456 
 
 NOTES. 
 
 Equal parts of the mordants, that is, half the weight of the stuff, pro- 
 duced no better effect than one-fourth ; but between this quantity and 
 one-twentieth part, the colours of cochineal, kermes, and madder, were 
 weaker in proportion to the diminution of the quantity of the salts ; whilst, 
 on the contrary, the effects were reversed with woad and brazil wood, .so 
 that in these last substances the colour was deeper the more the salts 
 were diminished. No difference could be observed in the colour, whether 
 the wools had been in the alum bath for two, four, or six hours ; it is, 
 therefore, useless to continue stuffs in the bath longer than two hours. 
 Our experiments did not discover that there was any difference in the 
 colour, whether the dyeing took place immediately after the aluming, or 
 was protracted for some time, except only that wool impregnated with 
 alum alone, produced a deeper colour with woad, after having been ex- 
 posed some time to a cool air, which we attributed to the separation of 
 the acidulated sulphate of potash, this being carried off with the uncom- 
 bined mordant in drying. 
 
 Of the Scarlet Colour, 
 
 Scarlet is that bright and shining colour which is produced in wool, by 
 treating it with tartar, cochineal, and a highly oxydized solution of tin. 
 Before the discovery of this method, for which we are entirely indebted to 
 Drebbel, those colours were called scarlet which are produced in woollen 
 stuffs by kermes or cochineal, when alum and tartar were employed as 
 mordants. These processes for obtaining the colour have long been 
 known in the dyeing houses, yet no theoretic investigations have been 
 made into the phenomena which take place when a solution of tin is used 
 with cream of tartar and cochineal. Dr. Bancroft attempted to explain 
 what passes in the formation of this colour ; but as his opinion does not 
 appear to be founded on any experiments, we considered the question as 
 not at all determined by his labours. We propose, therefore, to deter- 
 mine the chemical nature of the combination formed upon wool by cochi- 
 neal, tartar, and a solution of tin, and to make known the result of our 
 inquiries upon the colour of scarlet. 
 
 Examination of the Precipitate formed by the Solution of Tin, and the 
 Bitartrate of Potash, 
 
 All the substances employed by us in our experiments were perfectly 
 pure, and we constantly made use of glass vessels and distilled water. 
 1240 grains of bitartrate of potash, dissolved in six pints of distilled water, 
 were macerated for two hours, at 212° F. of heat, with 1 25 grains of a 
 solution of peroxyde of tin. The precipitate which we obtained was 
 
NOTES. 
 
 457 
 
 washed several times, and distilled in a small curved retort, the beak of 
 which being plunged into lime water, there was disengaged a sensible 
 quantity of carbonic acid. Proper re-agents indicated, in other portions 
 of it, the presence of a great deal of tin and muriatic acid. Thus the 
 cream of tartar and solution of tin are decomposed, and produce a preci- 
 pitate, consisting of tartaric acid, and a great quantity of muriatic acid and 
 tin. The mother water contains tartrate of potash, bitartrate, very acid 
 muriate of tin, and a considerable proportion of precipitate, held in solution 
 by excess of muriatic acid. 
 
 Very pure white wool, treated with the ordinary proportions of solution 
 of tin and cream of tartar employed in dyeing scarlet, was washed a great 
 number of times in boiling water, which carried off all the substances 
 combined with it. These washings, collected and evaporated, afforded us 
 the same principles we had before obtained from the precipitate formed 
 by the solution of tin and cream of tartar : we also examined, in the same 
 way, the action of cochineal, and found no difference in the results. 
 From these facts we are, to a certainty, convinced, that the fine scarlet 
 colour is produced by the wool being combined with colouring matter, 
 tartaric acid, muriatic acid, and peroxyde of tin. But we shall mistake, 
 if we think the bath has no influence on the colour ; for wool, combined 
 with the mordants we shall presently mention, and dyed with cochineal, 
 never takes the scarlet hue unless some acid be added, which causes the 
 colour to pass from yellowish to red, and at length to a bright colour. 
 This last experiment, and some others which we shall relate towards the 
 close of this memoir, proved to us, that the wool is not coloured yellow 
 by the combination it forms with the nitric acid in excess in the solution 
 of tin, for this wool comes out perfectly white from all the boilings it 
 undergoes with the tin, when no colouring matter is employed. 
 
 Of Tartrate of Tin, and some other Metallic Solutions. 
 
 The proofs we have already given of the formation of scarlet, appear 
 to us so decisive, that we should not have thought of increasing the 
 number, had not the importance of the question induced us to extend 
 further our labours on this subject. 
 
 We tried upon wool, in the usual proportions for dyeing scarlet, all 
 the sulphates and muriates of antimony, bismuth, zinc, arsenic. Some of 
 these solutions afforded very agreeable colours, but very different from 
 what we were seeking to obtain. We were more fortunate in our attempts 
 with the tartrate of tin, obtained from tartrate of potash and soda, and a 
 highly oxydized muriate of tin. This salt, dissolved in muriatic acid, 
 and used in the operation of dyeing, afforded us a scarlet colour, as beau- 
 
458 
 
 NOTES. 
 
 tiful and bright as those obtained by cream of tartar and a solution of tin. 
 The tartrate of tin, also, dissolved in an excess of its own acid, produced 
 very good effects : however, as this method would be more costly than 
 the ordinary processes, it is best to employ the solution of this salt in 
 muriatic acid. But before recommending this mordant to be used in the 
 dye-houses, we intend to make trial of it in the large way, so as to deter- 
 mine precisely the expense of it, and what advantages will be obtained 
 by its employment. 
 
 Experiments on the Colour of Scarlet and the Oxydes of Tin, 
 
 Scarlet, as we have already seen, is obtained by treating wool with 
 determined proportions of cochineal, bitartrate of potash, and a highly 
 oxydized solution of tin. The operation of dyeing is divided into two 
 parts ; the first taking up an hour and a half, the latter half an hour : this 
 division is necessary to produce a good colour, which would be weaker 
 and more yellow if all the substances were mixed in the first operation, 
 and applied to the wool for two hours. This circumstance is owing to 
 the very acid state of the bath, which holds in solution a great part of the 
 mordant and of the colouring matter. We obtain the contrary effect 
 when the mordants only are employed in the first operation, and the 
 cochineal reserved for the second. 
 
 Pieces of very beautiful scarlet cloth, macerated in distilled water, at a 
 boiling heat, gave out to the water a portion of their colour, and when 
 the operation was finished, appeared only of a light flesh-colour. The 
 washings, collected and evaporated, were very acid, and contained, besides 
 the colouring substance and animal matter, tartaric acid, muriatic acid, 
 and oxyde of tin. Scarlet, therefore, as we have already shown, is a 
 combination in some measure soluble, which, in parting with a small 
 quantity of acid, changes its shade, and may, by repeated washings at 
 elevated temperatures, and with a large bulk of fluid, be rendered com- 
 pletely colourless. 
 
 It results from the experiments related in this memoir, — 
 
 1 . That in aluming all vegetable and animal substances, it is not the 
 alumina which combines with them, but the entire alum ; and that, when 
 these matters are not purified, the lime which they contain occasions a 
 decomposition of a part of this mordant. 
 
 2. That all the alkaline and earthy bases, mixed with a solution of 
 alum, decompose it, and convert it into acid sulphate of potash, and into 
 an insoluble salt, less acid than alum, which may, by repeated washings, 
 be converted into pure alumina, sulphate of potash, and alum. 
 
 3. That the acetate of alumina combines also in its entire state with 
 
NOTES. 
 
 459 
 
 silk, wool, cotton, and thread ; that this compound retains its acid but 
 feebly, and loses a portion of it by simple exposure to the air ; and that 
 it is then changed into acid acetate of alumina, whicli is carried off by 
 water, and into alumina which remains upon the stuffs. 
 
 4. That alum and tartar are not decomposed, but that the solubility of 
 the latter is increased by the mixture ; and that in impregnating wools 
 either with tartar, or alum and tartar, the tartar alone is decomposed ; 
 that the tartaric acid and ialum combine with the stuff, and tartrate of 
 potash remains in the bath. 
 
 5. That the most powerful acids have the property, when combined 
 with wool, of fixing the colouring matters : a property possessed in a high 
 degree by the acid tartrate of alumina. 
 
 6. That alum and tartar cannot be employed indifferently for all 
 colours, and that their proportions must depend upon the nature of the 
 colouring matter ; that the time of aluming should not be more than two 
 hours, and that the exposure of the stuffs in a moist place, after the 
 mordants are applied, is of no utility in augmenting the intensity of their 
 colour. 
 
 7. That highly oxydized tartrate of tin, dissolved in muriatic acid, may 
 supply the place of cream of tartar and the solution of tin in dyeing 
 scarlet. 
 
 8. Lastly, that these experiments furnish some useful hints for com- 
 bining mordants with the stuffs to be dyed, and for improving several of 
 the processes of dyeing. 
 
 To complete these researches relative to the action of mordants, it 
 would without doubt be necessary to determine, in the most accurate 
 manner, the changes produced in these combinations by the colouring 
 matters, when applied to the different stuffs. 
 
 Note C. p. 46. 
 
 Some fraudulent chemical manufacturers take advantage of the analo- 
 gous properties of oxyde of zinc to that of tin, to prepare a permuriate 
 of tin containing a considerable quantity of zinc, which is only about the 
 sixth of the value of tin. The adulteration is the more complete and 
 secure, inasmuch as the oxyde of zinc dissolves equally as well as the 
 oxyde of tin in an excess of caustic alkali, which is the chief test it has 
 to undergo, as the calico-printer is generally satisfied if the precipi- 
 tate thrown down by caustic alkali dissolves in an excess. If, how- 
 ever, from the colours obtained, or otherwise, there is reason to suspect 
 the purity of the permuriate of tin solution, a stream of sulphuretted hy- 
 drogen should be sent through a small quantity of it until all the tin be 
 
460 
 
 NOTES. 
 
 precipitated. If the acid solution from which the tin has been precipi- 
 tated give a white precipitate when it is neutralized with ammonia and a 
 current of sulphuretted hydrogen sent through it, we may be sure it 
 contains zinc. The above method may be used in estimating the quantity 
 of zinc, using, of course, weighed quantities. 
 
 It is, however, only due to the chemical manufacturers to state that 
 they themselves are sometimes deceived. I once had occasion to ana- 
 lyse an alloy of zinc and tin containing one part of the former to 
 two of the latter. This alloy had been sold to a chemical manufacturer 
 as tin, and had been used as such to mal^e solutions of muriate and 
 permuriate, before he was aware of the fraud practised upon him. 
 
 Note D. p. 49. 
 
 Acetate of alumina is now most frequently made for the calico print- 
 ers, by dissolving alum in a solution of crude acetate of lime, (pyrolig- 
 nite :) a gallon of the acetate, of specific gravity 1.050, or, 1.060, being 
 used with 2f lbs. of alum. A sulphate of lime is formed, which precipi- 
 tates, while an acetate of alumina, mixed with some alum, floats above. The 
 specific gravity of this liquid is usually about 1 .080. The acetate of 
 alumina employed as a mordant for good colours, is made by the calico 
 printers in Lancashire from 
 
 100 pounds of alum, 
 75 „ acetate of lead, 
 
 40 gallons water. 
 
 The alum is dissolved in the water, and when the solution is at from 
 150° to 170° Fahr., the acetate of lead is added. The whole, after being 
 properly stirred, is allowed to settle. The mordant is now decanted from 
 the sulphate of lead, and laid aside for use. With these proportions there 
 is not enough of acetate of lead to decompose all the sulphate of alumina 
 in the alum ; but the results of a great many experiments warrant me in 
 saying that these proportions are the best, and that the mordant containing 
 an excess of alum is not only as rich, but that it gives a much brighter 
 colour than one in which the alum is completely decomposed. I am aware 
 that it is generally supposed by chemists, that all the alumina is usekss 
 which does not exist as acetate in the mordant. This, however, is an 
 erroneous opinion, for a mordant made with 75 parts of acetate of lead, is 
 as powerful as one made with 125 parts to 100 parts of alum, although it 
 requires 125 parts to decompose all the sulphate of alumina, and 164 
 parts acetate of lead, if we wish at the same time to decompose the sul- 
 phate of potash of that quantity of alum. 
 
NOTES. 
 
 461 
 
 Berthollet recommends the addition of soda and chalk to the alum to 
 saturate its free acid, but printers in general object to the use of either, the 
 soda doing no good, and the chalk positive harm, by the resulting sul- 
 phate of lime, which is partially soluble, acting as a mordant, to the 
 prejudice of the colours. 
 
 Note E. p. 50. 
 
 See the figure and description of the padding or blotching machine, in 
 the Appendix. 
 
 The action of cow-dung in the process of calico printing, has not been 
 hitherto completely analyzed. It probably seizes that portion of the mor- 
 dant which is not intimately combined with the cloth, thus depriving it of 
 the power of applying to the rest of the surface, when diffused through the 
 water of the cleansing bath. Thus some animal principle in the dung, 
 by neutralizing the excess of mordant, and possibly precipitating it in an 
 insoluble or inert state, protects the unmordanted spaces from being 
 stained or coloured. 
 
 Note F. p. 51. 
 
 See the figure, and explanation of the wash wheels, at the end of the 
 volume. This mode of washing is by much the most economical and 
 effective. Several other mechanical modes of washing are used in the 
 linen trade. 
 
 Note G. p. 51. 
 
 Bran acts in some peculiar way on the colouring matter, but scarcely 
 on the mordants. It seems to loosen and remove the colouring matter ; 
 as also to alter its hue in some cases, an effect obvious in the bran pinks. 
 
 Note H. p. 51. 
 
 The strength of the solution of chloride of lime for clearing calico 
 grounds, varies according to the goodness of the white to be cleared, and 
 the capability of the colour to bear it. From half a pound to a pound 
 of the dry commercial chloride, for 100 gallons of water at 180° Fahren- 
 heit, may be considered as an average proportion. 
 
 Note I. p. 53. 
 
 James Thomson, Esq., of Primrose Hill, obtained, in the years 1813 
 and 1815, two patents for certain improvements in calico printing. His 
 processes, which are very elegant, have since been extensively ^nd advan- 
 tageously employed. The following is an outline of his specifications. 
 That for 1813 is thus stated 
 
 First, Mix or combine with the acid called oxymuriatic acid (or dephlo- 
 
462 
 
 NOTEwS. 
 
 gisticated acid of sea salt) and water, some of the alkaline salts or earths 
 hereinafter named, which shall weaken or suspend the power of the said 
 acid in such proportion, that it shall not, in such mixed or combined state, 
 of itself, and without any farther operation, be able to remove the turkey- 
 red colour from the cloth, or materially to impair it, within the moderate 
 space of time taken up in the performance of the process hereinafter 
 described. 
 
 Secondly, Print, stamp, pencil, or otherwise apply to those parts of the 
 said cloth, which are intended to be either wholly, or in a greater or less 
 degree, deprived of their red colour, some other acid or metallic oxyde, 
 or calx, which has a greater affinity or attraction for the alkaline salt or 
 earth with which the oxymuriatic acid is mixed or combined, than that 
 acid itself possesses : and if any one of the stronger or more powerful 
 acids be employed, which is either of a corrosive nature, and cannot be 
 safely used, or of a volatile nature, and cannot be used conveniently, such 
 acid must be combined with alkalies, earths, metals, or metallic oxydes or 
 calces, so as to form neutral salts, acid salts, or metallic salts, which shall 
 not be too corrosive or too volatile ; and such alkalies, earths, metals, or 
 metallic oxydes, or calces only, must be employed, as have a weaker 
 affinity or attraction for the same acid than that acid has for the alkaline 
 salt or earth with which the oxymuriatic acid has been mixed or combined. 
 
 Thirdly, After the said acids, oxydes, neutral salts, acid salts, or metal- 
 lic salts, so directed to be printed, stamped, pencilled, or otherwise applied 
 to the cloth as aforesaid, are sufficiently dry, immerse the cloth in the 
 solution of the said oxymuriatic acid, so mixed or combined with some 
 of the alkaline salts or earths hereinafter named as aforesaid. When the 
 acid or oxyde, either in its simple or combined state, has been applied to 
 parts of the cloth, it immediately seizes upon and combines with the alka- 
 line salt or earth with which the oxymuriatic acid has been mixed or 
 combined, and disengages that acid, which almost instantaneously deprives 
 of their colour those parts of the cloth to which the said acids or oxydes, 
 in their simple or combined state, have been so printed, stamped, pencilled, 
 or otherwise applied as aforesaid. 
 
 Lastly, Wash or otherwise remove all the said acids, oxydes, or salts, 
 by the usual processes. For the more fully explaining and illustrating 
 the invention hereinbefore described, I add the following remarks : — The 
 alkaline salts or earths which I mix or combine with the oxymuriatic acid, 
 in order to suspend or prevent its action on those parts of the red cloth 
 which are intended to retain their colour, are the alkaline salts of potash 
 and soda, or the calcareous, magnesian, barytic, or strontitic earths, of 
 which I prefer the calcareous earth. 
 
 The acids which I apply to the parts intended to be made white, or to 
 
NOTES. 
 
 463 
 
 those places on the cloth intended to be deprived of their red colour, in a 
 greater or less degree, are any of the vegetable, mineral, or animal acids, 
 v^hich have a stronger attraction for the alkaline salt or earth with which 
 the oxymuriatic acid has been mixed or combined, than that acid itself 
 has ; such, for instance, are the citric, oxalic, tartaric, malic, benzoic, sul- 
 phuric, sulphurous, phosphoric, fluoric, boracic, nitric, muriatic, arsenic, 
 tungstic, succinic, and carbonic acids. 
 
 The stronger acids, or such as might corrode the cloth, I saturate more 
 or less with some alkaline salt, earth, or metallic oxyde or calx, for which 
 they have a weaker affinity or attraction than they have for the alkali or 
 earth with which I have combined the oxymuriatic acid : for instance, I 
 unite the sulphuric acid with potash, so as to form the acid sulphate of 
 potash, (or acid vitriolated tartar,) or with aluminous earth, to form alum. 
 The muriatic acid I combine with tin, or copper, or zinc, forming muriate of 
 tin, muriate of copper, or muriate of zinc. In like manner, the nitric acid 
 may be combined with the aluminous earth, or with the volatile alkali, or 
 with the metals, or oxydes of copper, or zinc, or iron, or mercury ; and I 
 take care, when I use acidulous compounds of such corrosive acids, not to 
 suffer the acid so far to predominate as to render the compound injurious. 
 In like manner, I combine the volatile acids, or such as might evaporate 
 too speedily, with some alkaline salt or earth, or metallic pxyde or calx, 
 for which they have a weaker affinity or attraction than they have for the 
 alkali or earth with which I have combined the oxymuriatic acid : for 
 instance, I combine the acetic acid with the earth of alum, so as to form 
 acetate of alumina,— or with copper, forming acetate of copper, — or with 
 zinc, forming acetate of zinc. The carbonic acid may also be fixed and 
 combined with an alkali, as with soda, for example, forming carbonate of 
 soda, which may be used, though with less advantage than the preceding 
 combinations. Those acids which are not corrosive nor volatile, and which 
 consequently are used with most advantage in their simple or combined 
 state, may, however, be united, like the preceding, to the alkalies, earths, 
 metals, or metallic oxydes or calces, for which they have a weaker affinity 
 or attraction than they have for the alkali or earth with which the oxy- 
 muriatic acid has been united. Thus the tartaric acid may be combined 
 with potash, to form cream of tartar, — and the oxalic acid with potash, to 
 form salt of sorrel, — and these two salts may be employed in the process, 
 though it is not necessary so to combine the two acids ; but, on the con- 
 trary, the acids may be used alone. 
 
 The combinations which I prefer as uniting the greatest number of 
 advantages upon the whole, are, the super-sulphate of potash, (or acid 
 vitriolated tartar,) the sulphate of copper or blue vitriol, the muriate of 
 tin, or sal jovis, the nitrate of copper, and the muriate of copper. But I 
 
464 
 
 NOTES. 
 
 prefer to any single combination a mixture of the supersulphate of potash, 
 with the tartaric or citric acids. 
 
 Lastly, I employ, uncombined, such metallic oxydes or calces as approach 
 in their properties to the nature of acids, and are capable of combining 
 either with the alkaline salts of potash or soda, or with the calcareous, 
 magnesian, or strontitic earths, or of disengaging them, or any of them, 
 from their combination with oxymuriatic acid : such, for instance, is the 
 oxyde of arsenic, or common white arsenic, and the oxydes of tin and 
 tungsten. 
 
 It is evident, from what I have set forth in the preceding part of this 
 specification, that this process admits of great variety in its application, 
 according to the combinations I make use of ; since, not only the various 
 acids, oxydes, and salts I have enumerated, may be employed, but also 
 various mixtures of them, and in various proportions ; but I prefer and 
 generally use the following process : — 
 
 First, I take one gallon of good vinegar, or rectified pyrolignous acid, 
 which I thicken with starch or flour in the way practised by calico printers, 
 in preparing the mordants or colours for printing. Whilst boiling hot, I 
 add to it five pounds of crystallized tartaric acid, and incorporate the 
 whole very well by stirring. 
 
 Or, I take one gallon of strong concentrated lime-juice or lemon-juice, 
 or one gallon of water, in which I have dissolved two pounds and a half 
 of crystallized citric acid, which I thicken with starch or flour in the 
 manner directed above, and to which, whilst hot, I add two pounds of 
 supersulphate of potash, and incorporate the whole very well by stirring. 
 I prefer starch to any other thickening, though others may be used with 
 more or less advantage. 
 
 Secondly, The paste so prepared I print, stamp, pencil, or otherwise 
 apply to the cloth previously dyed turkey red, in the mode and with the 
 precautions generally used in the printing or stamping of linens or cottons. 
 
 Thirdly, I prepare a solution of oxymuriate of lime, either by dissolving 
 the dry oxymuriate of lime (commonly called bleaching powder, or bleach- 
 ing salts) in water, or by passing the oxymuriatic acid gas into a vat, 
 vessel, or cistern, in which, by agitation or otherwise, I keep suspended 
 such quantity of quicklime as will more than saturate fully and completely 
 the said oxymuriatic acid gas. In either way, I obtain a solution of 
 oxymuriate of lime, with excess of lime. That which I use and prefer 
 is of the specific gravity 1050, and I seldom employ it lower than 1030, 
 (water being considered as 1000.) The vat, vessel, or cistern, which 
 contains the solution of oxymuriate of lime, in which I immerse the 
 cloths, may be of any size or form best adapted to the purpose or situation. 
 I use and prefer vessels of stone of from six to eight feet deep, six to 
 
NOTES. 
 
 465 
 
 seven feet long, and three and a half to four feet broad ; but larger or 
 smaller vessels will answer very well. 
 
 Fourthly, When the cloths are ready for immersion, which they are as 
 soon as the paste is dry, I hook them on a frame, such as is used in 
 dyeing indigo or china blues, commonly called a dipping frame, on which 
 the cloth should be so disposed that no two folds can touch each other. 
 I then plunge the frame with the cloth so attached into the vat contain- 
 ing the solution of oxymuriate of lime, and keep it gently in motion 
 during the time of immersion, which should not be prolonged more than 
 ten minutes, and which rarely need exceed five minutes. The object 
 being either wholly or partially to remove the turkey red dye from certain 
 parts or places, as soon as that is done the cloth should be withdrawn 
 from the solution of the oxymuriate of lime, and plunged or rinsed in 
 clean water. I practise and approve the aforesaid plan of immersion ; 
 but any other plan or plans by which the cloth can be exposed a greater 
 or less time to the action of the oxymuriate of lime, without bringing one 
 part of the said cloth into contact with another, will answer very well. 
 
 Lastly, After having, as before directed, rinsed or washed the cloths in 
 clean water, I free them from all remains of the different agents or sub- 
 stances employed, by the ordinary means of washing, branning, or soaping, 
 as practised by calico printers ; and if those parts of the cloth that are 
 intended to be made white should still retain any red, or other tinge or 
 stain injurious to the effect, in order to render the white complete, I clear 
 it by the usual process of exposure to the air, or by passing the cloth 
 through hot water, to which I have added as much of the solution of 
 oxymuriate of lime as will remove the said stains or tinge, without mate- 
 rial injury to those parts from which the red dye is not intended to be 
 removed. 
 
 I then proceed, if other colours are to be applied, to finish the cloths 
 by the ordinary and well known methods of calico printers ; but these 
 not being necessarily connected with, nor forming any part of the peculiar 
 process or invention herein intended to be described, I purposely make no 
 mention of here. 
 
 The above particulars and examples are given for the more full explana- 
 tion of the said invention, and the manner in which the same is to be 
 performed. But the invention, whereof I claim the so^e and exclusive 
 use, consists in printing, stamping, pencilling, or otherwise applying to 
 those parts of the cloth which are intended to be either wholly, or in a 
 greater or less degree, deprived of their red colour, an acid, oxyde, neutral 
 salt, acid salt, or metallic salt, such as is hereinbefore for that purpose 
 directed, and immersing the whole cloth in such mixture or combination 
 
 2 H 
 
466 
 
 NOTES. 
 
 of oxymuriatic acid and water, with some of the alkaline salts or eartlie, 
 as is herein directed for that purpose. 
 
 Mr. Thomson's patent for 181 5, is specified as follows : — 
 
 The ordinary practice of calico printers is to apply, with the block or 
 pencil, what are termed after-colours, to certain spaces, originally left in 
 their patterns, and intended to receive the said after-colours ; or to cer- 
 tain spaces on the cloth, from which parts of the original pattern have been 
 discharged, in order to admit, by a subsequent operation, the application of 
 the said after-colours. Now the object of my invention is, by one appli- 
 cation of the block, cylinder, roller, plate, pencil, or other mode, to remove 
 parts of the original pattern or colour from the cloth, and at the same time 
 to deposit a metallic oxyde, or earthy base, which shall of itself be a 
 colour, or shall serve as a mordant to some colour to be produced, as 
 hereinafter described. 
 
 First, Mix or combine with the acid called oxymuriatic acid (or dephlo- 
 gisticated acid of sea salt) and water, the alkaline salts of potash or soda, 
 or, which is still better^ calcareous earth or quicklime, in such proportion 
 as will weaken or suspend the power of the said acid, so that it shall not 
 in such mixed or combined state, of itself, and without any further opera- 
 tion, be able to remove, or materially to improve the colours, within the 
 moderate space of time taken up in the performance of the process. 
 
 Secondly, Print; stamp, pencil, or otherwise apply to those parts of the 
 cloth which are intended to be deprived of one colour and to receive an- 
 other, a solution of some earthy or metallic salt ; the acid of which having 
 a greater affinity or attraction for the alkaline salt or earth with which the 
 oxymuriatic acid is mixed or combined than that acid itself possesses, will 
 disengage it, and the metallic or earthy base of which being deposited in 
 the cloth, will either of itself be a colour, or serve as a mordant to some 
 other colour, to be produced as hereinafter described. 
 
 Thirdly, After the metallic or earthy solution aforesaid has been printed, 
 stamped, pencilled, or otherwise applied to the cloth, as before directed, 
 and is sufficiently dry, immerse the cloth in the solution of oxymuriatic 
 acid, combined with the alkaline salt of potash or soda, or, which I greatly 
 prefer, with calcareous earth or lime, when the acid of the metallic or 
 earthy solution which has been applied to parts of the cloth, will immedi- 
 ately seize upon ^d combine with the alkaline salt or earth with which 
 the oxymuriatic acid has been mixed or combined, and disengage that 
 acid, which will almost instantaneously deprive of their colour those parts 
 of the cloth to which the said earthy or metallic salt has been applied. 
 
 Fourthly, Wash or otherwise remove the said acids or salts by the usual 
 processes, and when the earthy or metallic base, deposited in the cloth, is 
 
NOTES, 
 
 467 
 
 intended to receive another colour, proceed to raise it by the usual opera- 
 tions of dyeing, as will be further illustrated in the examples hereafter given 
 of particular applications of this invention. The earthy solutions which I 
 apply to the parts intended to be deprived of their colour, and to receive 
 another, are the solutions of alumina, or earth of alum in acids ; such, for 
 example, as the sulphate of alumina, or common alum, the acetate of 
 alumina, or the nitrate or muriate of alumina. The metallic solutions 
 which I employ are, the sulphate of iron or copperas ; the nitrate, or mu- 
 riate, or acetate of iron ; the muriate of tin, or nitro-muriate of tin ; the 
 sulphate of copper or blue vitriol, or the nitrate, muriate, or acetate of 
 copper. All acids that form soluble compounds with the before-named 
 metals, or the earth of alum, may be employed ; but those only which 
 form the most soluble compounds, such, for example, as those enumerated 
 above, can be employed with advantage. For the more full and complete 
 understanding of the principle laid down in the preceding part of this spe- 
 cification, I subjoin the following practical illustration of its application to 
 various kinds of work. If I desire to have a yellow figure or stripe on the 
 cloth, upon which a madder-red ground or pattern has been printed, after 
 having, by the ordinary processes of calico printing, produced the red 
 ground or pattern, I first print, stamp, pencil, or otherwise apply to those 
 parts intended to be yellow, a strong aluminous mordant, composed of 
 three pounds of sugar of lead, and six pounds of alum, dissolved in a gallon 
 of water, and thickened with a due proportion of calcined starch, in the 
 manner usually practised by calico printers. 
 
 Secondly, I prepare a solution of oxymuriate of lime, either by dissolving 
 the dry oxymuriate of lime (commonly called bleaching powder, or bleach- 
 ing salts) in water, or by passing the oxymuriatic gas into a vat, vessel, or 
 cistern, in which, by agitation or otherwise, I keep suspended such quan- 
 tity of quicklime as will more than saturate fully and completely the said 
 oxymuriatic gas. In either way, I obtain a solution of oxymuriate of lime, 
 with excess of lime. That which I use and prefer is of the specific gravity 
 1050, and I seldom employ it lower than 1030 (water being considered as 
 1000.) The vat, vessel, or cistern, which contains the solution of oxymu- 
 riate of lime in which I immerse the cloth, may be of any size or form 
 best adapted to the purpose or situation. I use and prefer vessels of stone, 
 of from six to eight feet deep, six to seven feet long, and three and a half 
 to four feet broad ; but larger or smaller vessels will answer very well. 
 
 Thirdly, When the cloth is ready for immersion, which it is as soon as 
 the paste is dry, I hook it on a frame, such as is used in dyeing indigo or 
 china blues, commonly called a dipping frame, on which the cloth should 
 be so disposed that no two folds can touch each other. I then plunge 
 the frame, with the cloth so attached, into the vat containing the solution of 
 
 2 H 2 
 
468 
 
 NOTES. 
 
 oxymuriate of lime, and keep it gently in motion during the time of im- 
 mersion, which rarely need exceed five minutes. The object being to re- 
 move the red dye from certain parts or places, as soon as that is done the 
 cloth should be withdrawn from the solution of the oxymuriate of lime, 
 and plunged into or rinsed in cold water. I practise and approve the afore- 
 said plan of immersion ; but any other plan, or plans, by which the cloth 
 can be exposed a greater or less time to the action of the oxymuriate of 
 lime, without bringing one part of the said cloth into contact with another, 
 will answer very well. 
 
 Lastly, After having, as before directed, rinsed or washed the cloth in 
 clean water, I free it from all superfluous remains of the different substances 
 employed, by the ordinary means of washing, dunging, and cleaning, as 
 practised by calico printers ; after which I dye the cloth and raise the yel- 
 low in the usual way, with quercitron bark, or any other yellow dye. 
 
 If, instead of yellow, it is proposed to have a buff pattern or figure, I 
 add to the aluminous mordant, prepared and thickened as above, one- 
 fourth or one-sixth, or some intermediate proportion, of a solution of nitrate 
 of iron, and proceed to print and immerse in oxymuriate of lime, as in the 
 former case. 
 
 The red dye will be removed as before, and its place be occupied by a 
 bufi^. If the buff be raised in quercitron bark, an olive will be obtained. 
 By printing at separate times, and on different parts of the cloth, each of 
 the above-mentioned mordants, both yellow and olive figures on a red 
 ground may be obtained. Similar effects, with trifiing variations, take 
 place, when, instead of red grounds, purple or chocolate grounds are em- 
 ployed ; but it must be observed, that these colours being produced from 
 mordants consisting vv^holly, or in part, of solutions of iron, and the oxyde 
 of that metal not being removable by the process detailed in this specifi- 
 cation, the after-colours produced vv^ill be modified more or less by the 
 said oxyde of iron. The foregoing examples are given for the more full 
 explanation of the said invention, and the manner in which the same is to 
 be performed ; but the invention, whereof I claim the sole and exclusive 
 use, consists in printing, stamping, pencilling, or otherwise applying to 
 cloth, previously printed and dyed, or dyed any other colour than turkey 
 red, any of the earthy or metallic solutions hereinbefore for that purpose 
 directed, and immersing the whole cloth in such mixture or combination of 
 oxymuriatic acid and water, with some of the alkaline salts or earth, as is 
 herein directed for that purpose, so as to remove the colour or pattern from 
 the part so printed, stamped, pencilled, or receiving such application, and 
 by the same process, fix on such parts either a new colour or a mordant 
 for a new colour. 
 
NOTES. 
 
 469 
 
 Note K. p. 114. 
 
 James Lee, Esq., of Mertoii Abbey Flax-Mills, obtained a patent, in 
 1812, for preparing hemp and flax without the process of steeping and 
 dew-retting. He maintains, that, when the hemp or flax plants are ripe, 
 the farmer has nothing more to do than to pull them, as heretofore prac- 
 tised ; to spread and dry them in the sun, as he would his hay or grain, 
 taking care only in the ridges to lay the roots in one direction, so as to 
 prevent as much as possible the breaking or entanglement of the stems ; 
 and when sufiiciently dry, to carry and lay them in store, either in ricks 
 or barns. No preparation of a canal and running water ; no loss of time ; 
 no hinderance from harvest, or other business, is necessary. Mr. Lee 
 seems not to have been happy in what relates to the machinery for break- 
 ing and manufacturing the flax and hemp prepared by his dry method. 
 For an account of his mechanical contrivances, see some excellent papers 
 on the manufacture of hemp and flax, by John Mittington, Esq., inserted in 
 the Quarterly Journal of Science, Literature, and the Arts, vol. iv. p. 321 ; 
 vol. V. p. 32 ; vol. vi. p. 14]. 
 
 Note L. p. 120. 
 
 In a foot-note to page 38, I have adverted briefly to the mode of action 
 by which chlorine destroys vegetable colours. Sir IL Davy first showed 
 that dry chlorine does not blanch dry litmus paper, but that when moisture 
 intervenes the discoloration immediately takes place. When vegetable 
 colouring matter, which consists of hydrogen, oxygen, carbon, and occa- 
 sionally azote, (as in indigo,) is placed in contact with chlorine and water, 
 the elements react on one another ; the greater part of the chlorine seizes 
 the hydrogen to form muriatic acid, while some of it probably unites with 
 the carbon, hydrogen, and azote of the colouring matter, so as to constitute 
 a peculiar compound. The oxygen liberated from the water combines with 
 the carbon, rendering it soluble in alkaline leys. The yellow-coloured 
 substance resulting from the action of chlorine on moist vegetable colouring 
 matter, has not, I believe, been subjected to any rigid ultimate anal} sis. 
 Till this be done, the theory of bleaching by chlorine must be regarded 
 as imperfect. Of late years, quicklime has been very extensively and 
 profitably employed by the Lancashire bleachers as an alkaline agent. 
 They boil the unbleached cloth in a milk of lime for some time ; then 
 wash, and boil in a very weak solution of soda. 
 
 Note M. p. 123. 
 
 In the Quarterly Journal of Science and the Arts for July, 1822, I 
 published a paper on the composition and manufacture of chloride of 
 
470 
 
 NOTES. 
 
 liine, where the proper proportions of the ingredients employed in its 
 formation are investigated. " When a mixture of sulphuric acid, common 
 salt, and black oxyde of manganese are the ingredients used, the absolute 
 proportions are, 
 
 
 7.50 
 
 29.70 
 
 inn nn 
 
 1 atom of peroxyde of manganese . . 
 
 6.50 
 
 21.78 
 
 73.30 
 
 2 atoms of oil of vitriol, (1.346 sp.gr.) 
 
 12.25 
 
 48.52 
 
 163.30 
 
 
 25.25 
 
 100.00 
 
 336.60 
 
 And the products ought to be, 
 
 
 
 
 
 1 atom, 4.5 
 
 17.82 
 
 
 1 „ 
 
 9.0 
 
 35.64 
 
 Protosulphate of manganese . 
 
 I „ 
 
 9.5 
 
 37.62 
 
 
 2 „ 
 
 2.25 
 
 8.92 
 
 
 
 25.25 
 
 100.00 
 
 " These proportions are, hovs^ever, very different from those employed 
 by many, nay, I believe, by all manufacturers ; and they ought to be so, 
 on account of the impurity of their oxyde of manganese : yet, making 
 allowance for this, I am afraid that many of them commit great errors in 
 the relative quantities of their materials. 
 
 " From the preceding computation, it is evident that one ton of salt, 
 with one ton of the above native (impure) oxyde of manganese, properly 
 treated, would yield 0.59 of a ton of chlorine, which would impregnate 
 1.41 ton of slacked lime, producing two tons of bleaching powder, stronger 
 than the average of the commerial specimens ; or, allowing for a little 
 loss, which is unavoidable, would afford two tons of ordinary powder, with 
 a little more slacked lime," 
 
 I have lately analyzed two samples of recently made bleaching powder, 
 made by two eminent manufacturers, one in Scotland, the other in Eng- 
 land, and found the composition as follows : — 
 
 Chlorine . . . 18.00 . 16.7 
 Lime .... 37.00 . 31.3 
 Muriate of lime . . 28.50 . 29.0 
 Water .... 16.50 . 100.0 
 
 100.00 100.0 
 The above quantity of lime is associated or mixed with the chlorine. 
 The muriate of lime (chloride of calcium) is formed in the process, and is 
 a product very disadvantageous to the manufacturer, since it takes up about 
 one-half of his chlorine unprofitably, and adds a compound to his powder 
 probably injurious to the bleacher. Bleaching powder may be formed 
 which contains no appreciable proportion of the muriate of lime, as I have 
 
NOTES. 
 
 471 
 
 shown in the above memoir. By proper management, the manufacturer of 
 chloride of lime might therefore double his useful product at scarcely any 
 additional expense. 
 
 I may state that a much surer test of the value of chloride of lime, 
 than its power of decolourizing indigo in sulphuric acid, which cannot be 
 depended on, is to see how much chlorine it contains by its action upon 
 protosulphate of iron. For this purpose, dissolve 50 grains of the chloride 
 of lime in tepid water, and make the solution to fill the alkalimeter. Have 
 1 00 grains of sulphate of iron dissolved in a tumbler ; add the chloride 
 of lime to the iron solution until it ceases to give prussian blue, with drops 
 of prussiate of potash, on a cheese-plate. 
 
 The sulphate of iron (100 grains) always requires 12.81 grains of chlo- 
 rine, which, of course, is the quantity of chlorine in the measures of chloride 
 of lime used. Let the number of measures of chloride used be M, and the 
 whole number of the measures of the alkalimeter 100, then, 
 
 M : 12.8 : : 50 ; the whole chlorine in 50 grains chloride, twice 
 which is the per cent, of chlorine. 
 
 Note N. p. 126. 
 
 For a description of a convenient apparatus for preparing dry chloride 
 of lime, see the Quarterly Journal of Science and the Arts, for July, 1822. 
 In making the solution of chloride of lime or potash, the same arrange- 
 ment of alembics may be adopted, but the chlorine disengaged must be 
 conducted by lead pipes into large wooden vessels lined with lead, or 
 constructed of masonry, whieh contain the mixture of lime or potash 
 with water. The contents of this vessel or condenser are kept con- 
 stantly agitated by means of wooden or iron vanes coated with lead, 
 revolving on a vertical axis. 
 
 One of the most convenient modes of ascertaining the amount of real 
 alkali in an alkaline solution or substance, is described by Faraday in his 
 work on chemical manipulation. " Into a tube sealed at one end, 9i 
 inches long, | of an inch in diameter, and as cylindrical as possible in its 
 whole length, pour 1000 grains of water, and scratch the place where its 
 surface reaches, and divide the space occupied by the water into 100 
 equal parts. Opposite to the numbers 2Si, 49, 541, and 65, draw a 
 line, and at the first write soda, at the second, potash, at the third, car- 
 bonate of soda, and at the fourth, carbonate of potash. Then prepare a 
 dilute acid having the specific gravity of 1.127^ (25i Tw.) at 60^ F., 
 which may be made by mixing one measure of concentrated sulphuric acid 
 with four measures of pure water. This is the standard acid to be 
 used in all the experiments, being of such a strength that, when poured 
 into the tube till it reaches either of the four marks just mentioned, we 
 
472 
 
 NOTES. 
 
 shall obtain the exact quantity which is necessary for neutrahzing 100 
 grains of the alkali written opposite to it. If, when the acid reaches the 
 word carb. potash, and when, consequently, we have the exact quantity 
 which will neutralize 100 grains of that carbonate, pure water be added 
 until it reaches 1, or the beginning of the scale, each division of this mix- 
 ture will neutralize one grain of carbonate of potash. All that is now 
 required in order to ascertain the quantity of real carbonate in any speci- 
 men of pearlash, is to dissolve 100 grains of the sample in warm water, 
 filter, and add the dilute acid in successive small quantities, until, by the 
 test of litmus paper, the solution is exactly neutralized. Each division 
 of the mixture indicates a grain of pure carbonate. Soda ash may be 
 tested in the same way, using, of course, its proportion of acid.'* 
 
 This, it will be perceived, gives the amount of alkali only contained in 
 the sample ; but it is sometimes necessary to know the amount of each 
 of the foreign salts accompanying the soda ash. These salts are invariably 
 muriate and sulphate of soda. To test the amount of these without the 
 trouble of drying and weighing precipitates, we may use the following 
 methods : — For the muriate of soda, dissolve 58 grains of nitrate of silver 
 for every such quantity of water as will make 100 measures of the alkali- 
 meter, the tube described above : 5 grains of muriate of soda dissolved 
 should just precipitate 25 measures of such a solution. It follows, that, 
 operating upon 20 grains, acidifying with pure nitric acid, heating to about 
 170° F., and adding so long as a precipitate is obtained, the per-centage 
 of muriate of soda in the sample is given. 
 
 To test the amount of sulphate of soda, dissolve 2Si grains of nitrate 
 of lead in every 100 measures : 20 grains of sulphate of soda would preci- 
 pitate 200 such measures. Using then 20 grains, and halving them, we 
 have the per-centage. 
 
 To obtain the whole analysis of a soda ash, take 40 grains, dissolve, 
 filter, and nniltiply the insoluble matter by 22, to get the per-centage ; 
 neutralize with pure nitric acid at 8° Tw.,* to get the soda ; then halve 
 the solution, after supersaturating with nitric acid, and test with the nitrates 
 of silver and lead, for the muriate and sulphate of soda. 
 
 Note P. p. 132. 
 
 SuLPHuiiET of lime, as proposed by Mr. Higgins, was extensively em- 
 ployed for one or two years by the linen bleachers of Ireland. Their goods 
 
 * This acid sboultl, on 100 measures of the alkalimetcr being taken, saturate 64.6 grains 
 of carbonate of lime, or 68.25 dried carbonate of soda. Either of these quantities is just 
 equal to 40 grains oxyde of sodium. So that the per-centage is obtained by weighing 40 
 grains of any alkaline solution, and ascertaining how many measures are required to saturate 
 it. For potash, use 61 grains. 
 
NOTES. 
 
 473 
 
 were, however, much injured by this article, whether from its injudicious 
 use, or otherwise, I do not know. I have been told, however, that this 
 compound has been recently tried in some establishments with advantage. 
 
 Note Q. p. 135. 
 
 The form of bucking tub (see plate at the end of the volume) now 
 used in this country, is a simplification of Widmer's. It is found to answer 
 perfectly well. 
 
 Note R. p. 140. 
 
 The introduction of the wash, dash, or splash wheel, of which a repre- 
 sentation is given at the end of the volume, may be regarded as a very 
 great improvement in the cotton manufacture of this country. Its velocity 
 must be nicely regulated. When it is too slow, the pieces of goods merely 
 slide down the inclined planes of the partitions ; and if too rapid, they are 
 held stationary at the circumference by the excess of centrifugal force. 
 The proper speed is stated in the explanation of the plate. 
 
 Note S. p. 150. 
 
 Mr. Welter, a practical chemist of deserved celebrity, states that a given 
 quantity of chlorine condensed in lime water destroys the colour of as much 
 test solution of indigo, as if it had been condensed in pure water. Hence, 
 it would appear that only chloride of lime is formed, and no muriate or 
 chlorate, for the two latter salts possess no bleaching power; and had any 
 of the chlorine been transformed into them, the discolouring force would 
 have been proportionally impaired. Yet M. Chenevix, in his memoir on 
 the hyperoxymuriates, or chlorates, obtained chlorates of lime and barytes 
 by transmitting chlorine through solutions of these earths in water. Of 
 these conflicting opinions it is difficult to decide which to adopt. The ana- 
 logy of solution of potash in its action with chlorine, is certainly favourable 
 to the views of M. Chenevix, If the affinity of chloric acid for the bases be 
 greater than that of acetic acid, then it would be possible to determine this 
 point by pouring vinegar on a determinate quantity of liquid chlorate of 
 lime slightly heated. On M. Welter's theory, nearly the whole bulk of 
 condensed chlorine would be recovered ; but on M. Chenevix's there 
 would be a very considerable deficiency, corresponding to the quantity of 
 muriate and chlorate formed. A mixture of chlorate and muriate of lime, 
 or of potash, neither of which has any bleaching power, would yield by 
 heat as much oxygen as a pure chloride of lime, in whose formation a like 
 quantity of chlorine had been expended as in that of the above mixtures. 
 Hence this mode of research, which has been recommended on respectable 
 
474 
 
 NOTES. 
 
 authority, is illusory, either for estimating the discolouring power of 
 liquors, or for analyzing these compounds.* 
 
 Note U. p. 172. 
 
 In Robertson Buchanan's Treatise on the Management of Fuel, some 
 useful directions will be found for applying steam to different processes of 
 dyeing. 
 
 Note V. p. 192. 
 
 The just explanation of the phenomena which occur in the manufacture 
 of sulphuric acid from the combustion of sulphur along with nitre, was first 
 developed by MM. Clement and Desormes ; and Sir H. Davy made some 
 important observations on the subject. An outline of their view of this 
 process is given m my Dictionary of Chemistry, article Acid (Sulphuric.) 
 It is a curious fact, that M. Berthollet was the only chemist of eminence 
 who resisted the mass of evidence adduced by MM. Clement and Desormes 
 in favour of their theory, which constitutes one of the most beautiful spe- 
 cimens of chemical research. 
 
 Note W. p. 204. 
 
 The reasoning in this paragraph about the union of muriatic acid with 
 oxygen, to form oxymuriatic acid, is quite erroneous, and has been long 
 since refuted by Sir H. Davy. A copious abstract of his experiments and 
 investigations will be found in the article Chlorine of my Dictionary of 
 Chemistry. 
 
 Note X. p. 205. 
 
 It is now known that the dry metallic muriates contain no oxygen, and 
 no muriatic acid, but that they are compounds of chlorine with a metal ; 
 hence properly called chlorides. M. Berthollet's highly oxydized muriate 
 (such as corrosive sublimate) contains no oxygen, but is a compound of 
 two proportions of chlorine with one of mercury, M. Chenevix's oxygen- 
 ated muriates are the chlorates of the present day, being compounds of 
 chloric acid with a metallic oxyde, or with ammonia. 
 
 Note Y. p. 214. 
 Th IS is a mistake. Acetic acid contains no azote. 
 
 * See latter part of note M. 
 
NOTES. 
 
 475 
 
 Note Z. p. 217. 
 By Klaproth's analysis, the aluin ore of Tolfa consists of 
 
 Silica 36.50 
 
 Alumina 19.00 
 
 Sulphuric acid .... 16.50 
 
 Potash 4.00 
 
 Water 3.00 
 
 99 00 
 
 Note A A. p. 219. 
 
 Alum is composed of 
 
 Sulphuric acid .... 33.00 
 
 Alumina . . . . . 11.00 
 
 Potash . . . . . 10.00 
 
 Water . . . . . 46.00 
 
 100.00 
 
 The common alum of commerce, the potash-sulphate of alumina, re- 
 quires about sixteen parts of water, at 60° Fah. to dissolve one of it ; but 
 there is another species, the soda-sulphate of alumina, soluble in less than 
 its own weight of water, which on this account may become valuable in 
 some processes of dyeing. 
 
 The small quantity of iron which is sufficient to deteriorate alum as a 
 mordant, renders it of consequence to be able to test the alum, especially 
 since it may appear pure enough to the eye when it contains a hurtful, 
 although small quantity of iron. All that is necessary for this purpose is 
 to dissolve a few grains of the alum in hot water, and add a solution of 
 caustic potash, until the white precipitate which is at first formed, entirely 
 disappears. If the alum contain iron, brown flakes will remain in the 
 liquor ; if not, the mixture will be colourless, and have no precipitate. 
 
 Note BB. p. 224. 
 
 A process in calico printing, of peculiar elegance, with an alkaline so- 
 lution of alumina, was invented by James Thomson, Esq., of Primrose Hill, 
 near Clithero. Its effect was to produce a fast green, by the mixture of a 
 yellow mordant with the common solution of indigo in caustic potash, 
 through the intervention of orpiment. This, as is obvious, could not be 
 done with any acid solution of alumina. Mr. Thomson first formed a solution 
 of that earthen potash, mixed this with the solution of indigo, and applied 
 the mixture, properly thickened, to the cloth. But as, in the ordinaiy dung- 
 ing operation, the alkali would naturally wash away with it the greater part 
 
476 
 
 NOTES. 
 
 of the alumina, the goods before being dunged were passed through a 
 solution of sal ammoniac. It is easy to perceive the rationale of what 
 takes place. The potash on the cloth combines with the muriatic acid of 
 the sal ammoniac, and as the two substances set free (the alumina and am- 
 monia) have no tendency to combine, the former remains precipitated on 
 the cloth at its points of application. 
 
 It obtained currently, but very improperly, the name of Warwick's green, 
 because Dr. Warwick made and sold the solution of aluminated potash to 
 the printers. 
 
 Note CC. p. 226. 
 
 There is no proposition better established in chemistry, than that the 
 different oxydes of the same metal are compounds of oxygen and the 
 metal in definite proportions, of which the series is regulated by the pro- 
 portion in the lowest term of oxydizement. The successive oxydes con- 
 tain oxygen amounting to two, three, or four multiples of that in the pro- 
 toxide. M. Berthollet was very unfortunate in adopting the notion of 
 indefinite combination, and scarcely pardonrible for resisting with such 
 obstinacy the great body of evidence incompatible with his hypothesis. 
 
 Note DD. p. 289. 
 
 Owing to the length of time necessary to saturate pyroligneous acid 
 with iron, some manfacturers make their acetate of iron by the decompo- 
 sition of sulphate of iron and acetate of lime. This preparation of iron 
 liquor always contains sulphate of lime, and neVer affords so good colours 
 as that made directly from acid and iron. It is therefore advisable for the 
 printer to test the method by which his acetate has been prepared, which 
 is very simple ; for when double decomposition has been resorted to, a con- 
 siderable excess of sulphate of iron is used to make the precipitate of 
 sulphate of lime settle down. All, then, that is required as a test, is to 
 add to the acetate of iron a few drops of a solution of acetate of barytes ; 
 if there be a precipitate, it is sulphate of barytes, and we may be sure that 
 the iron liquor has been made from acetate of lime, and is consequently 
 bad. Acetate of iron gives no precipitate with acetate of barytes, but it 
 does with acetate of lead, which should not be used as a test as the pre- 
 cipitate is apt to be mistaken for sulphate of lead. 
 
 Note EE. p. 233. 
 
 Before verdigris is pressed into cakes, it is in the form of light blue 
 acicular crystals of a silky lustre, which, by the action of water, are re- 
 solved into a soluble acetate and an insoluble subacetate of copper, the 
 latter being decomposed by the action of cold water, which gradually 
 
NOTES. 
 
 477 
 
 changes it into a brown powder ; whether it is thus totally resolved into 
 oxyde of copper, or whether it remains a sub-salt, has not been ascertained. 
 Mr. R. Phillips states the composition of the silky blue crystals as follows ■ 
 
 Acetic acid . . . 28.30 1 atom. 
 Peroxyde of copper . . 43.25 1 „ 
 Water .... 28.45 5 „ 
 
 The green decomposable powder obtained by acting on the silky crystals 
 with water, or the subacetate, consists of 50 acid -f IGO peroxyde of cop<. 
 per. There remains in solution a binacetate. 
 
 The following is Mr. Phillips's analysis of French and English verdigris. 
 
 French. English . 
 
 Acetic acid . . . 29.3 29.62 
 
 Peroxyde of copper . . 43.5 44.25 
 
 Water . . . . . 25.2 25.51 
 
 Impurity .... 2.0 0.62 
 
 100.0 100.00 
 Phillips's Annals^ No. 21. 
 
 Note FF. p. 255. 
 
 Mr. Braconnot pubhshed in the Annales de chimie, vol. Ixxxiv,, a 
 chemical examination of the husks of walnuts. The juice of the husks, 
 examined by re-agents, exhibited the following effects : It strongly red- 
 dened infusion of litmus. Solution of gelatin formed in it a slight preci- 
 pitate, which he ascribed to tannin. Sulphate of iron gave the juice so 
 deep a green, that it appeared black. No precipitation took place, even on 
 standing some time, in consequence of the free acid found in the mixture, 
 which is capable of imparting a fine grey to wool or silk. Oxalate of am- 
 monia indicated the presence of lime. Nitrate of barytes produced no 
 signs of any sulphate. Nitrate of silver acts on it in a manner well adapted 
 to reveal the presence of the alterable hydrocarburet radical, for it produces 
 a pretty copious precipitate, which quickly becomes coloured, while the 
 silver resumes its metallic lustre from the action of the vegetable substance 
 on the oxygen of the oxyde. The precipitate is then no longer soluble, 
 but in part, in nitric acid, and leaves charcoal as a residuum. Alkalies 
 change the juice to a deep red, and form in it precipitates that contain 
 lime. Acetate of lead occasioned in the juice a whitish, flocculent, very 
 copious precipitate, which dissolved entirely in distilled vinegar. From this 
 precipitate, malic and citric acids were obtained. Subacetate of lead pro- 
 duced a new precipitate with the preceding liquid, and rendered the whole 
 nearly colourless. This sediment yielded malic acid, colouring matter. 
 
478 
 
 NOTES. 
 
 and tannin. The magma left after expression of the juice, after having 
 been treated with alcohol, which extracted from it some green resinous 
 matter, was heated with water till it boiled, to free it from the starch and 
 the coloured matter it retained. When thus exhausted, it was digested 
 with dilute nitric acid, which separated some phosphate and oxalate of 
 lime, that had been precipitated from the acid liquor by ammonia. The 
 means employed to separate these two earthy salts, which are very fre- 
 quently associated in vegetables, are founded on the property which dis- 
 tilled vinegar diluted with water has of dissolving phosphate of lime 
 without sensibly affecting the calcareous oxalate. 
 
 Though the husk has a peculiar smell, it afforded nothing remarkable 
 by distillation in a water bath. 
 
 The incinerated ashes of the husk yielded potash, carbonate of lime, 
 phosphate of lime, and oxyde of iron. 
 
 From the above examination it appears, that the fleshy covering of the 
 walnut contains : — 
 
 1st, Starch ; 2nd, An acid and bitter substance, very alterable, which 
 appears to approach to the state of charcoal by the contact of air ; 3rd, 
 Malic and citric acids ; 4 th, Tannin ; 5th, Phosphate of lime ; 6th, Oxalate 
 of lime ; 7th, Potash. • 
 
 GuATiMALA indigo, treated first with water, then with alcohol, and 
 lastly with muriatic acid, afforded to M. Chevreul (Ann. de chimie, vol. 
 Ixvi. p. 20,) the following products: — 
 
 Note GG. p. 280. 
 
 P)y water 
 
 By alcohol 
 
 A little indigo 
 ''Red resin 
 
 6 
 
 2 
 
 2 
 
 3 
 
 A residuum 
 
 45 
 
 3 
 
 100 
 
 This process might therefore be adopted in the laboratory, for procuring 
 
NOTES. 
 
 479 
 
 indigo nearly pure. But when we wish to obtain this colouring substauce 
 exempt from all foreign matters, it is better to employ the following 
 method, which we owe to M. Chevreul. About 8 grains of common 
 indigo, in powder, are to be put into a crucible of platinum or silver, which 
 is to be carefully closed, and placed over ignited charcoal. The indigo 
 sublimes, and attaches itself in crystals to the middle portion of the cru- 
 cible. Another method is, to take the solution of deoxydized indigo, 
 made with a solution of sulphate of iron and lime, or alkali, to decant the 
 clear solution, and expose it to the air. The indigo speedily absorbs 
 oxygen, and becomes insoluble. When it is separated from the liquid, it 
 must be washed first with dilute muriatic acid, then with water, and lastly 
 with alcohol. M. Roard used in this way muriatic acid and water, for 
 purifying on the great scale the very impure indigoes obtained from pastil. 
 
 In my paper on the ultimate analysis of vegetable and animal sub- 
 stances, which the Royal Society honoured with a place in their Trans- 
 actions for 1822, the following are stated as the constituents of 100 parts 
 of indigo : Carbon 71.37, hydrogen 4.38, oxygen 14.25, azote 10. Or, 
 carbon 71.37, water (or its elements) 16, azote 10. But the examination 
 of indigo having been undertaken about the same time by my ingenious 
 friend, Mr. Walter Crum, I relinquished the subject. His paper on indigo 
 drawn up 1822, and published in the Annals of Philosophy for January^ 
 1823, must be regarded as the most elaborate and accurate analysis yet 
 given of this interesting vegetable product. ** For procuring indigo per- 
 fectly pure, I used," says he, " the covers of two platina crucibles, nearly 
 three inches in diameter, of such a form, that, when placed with their 
 concave sides inwards, they were about three-eighths of an inch distant in 
 the middle. I placed thinly about the centre of the lower one ten grains 
 of precipitated indigo, not in powder, but in small lumps of about a grain 
 in weight ; then, having put on the cover, I applied the flame of a spirit- 
 lamp beneath the indigo. In a short time this substance, partially decom- 
 posed, begins to melt, and the purple vapour to be disengaged, which is 
 known by the hissing noise that accompanies it. The heat is continued 
 till this noise nearly ceases, when the lamp is withdrawn, and the appara- 
 tus allowed to cool. Then, on removing the cover, the sublimed indigo 
 will be found planted upon its inner surface, with sometimes a few long 
 needles upon the bottom of the apparatus, which are easily removed from 
 the button of coaly matter that remains. In this way I have generally 
 obtained eighteen to twenty per cent, of the indigo employed ; a small 
 quantity unavoidably escapes, but I am persuaded that very little more can 
 by any means of this kind, be obtained. 
 
 " Those who cannot readily procure precipitated indigo for the purpose 
 of subliming, may find it convenient to combine with my method one lately 
 
480 
 
 NOTES. 
 
 gi\^n ill the Journal de Pharmacie, by MMw Le Royer and Dumas. It 
 consists in spreading about 30 grains of common indigo in coarse powder 
 upon an open silver capsule, and applying the heat of a spirit-lamp till all 
 the sublimed indigo is formed upon the surface of the ashes. On repeat- 
 ing this process, I find that ten parts of common indigo yield one of sub- 
 limed indigo, which is, however, far from being pure. By resublimation in 
 my apparatus, it is again reduced one-half from the loss of its impurities, 
 and some vapour. 
 
 " I shall here describe what else takes place during the sublimation. 
 Ten grains of precipitated indigo, in the apparatus I have described, yielded 
 
 1.88 grains of sublimed indigo. 
 
 C.44 grains of cinder remained, and consequently 
 
 1.68 grains of volatile matter escaped. 
 
 10.00 
 
 *' Thirteen grains of the same indigo, kept a quarter of an hour at a 
 strong red heat in a small platina crucible, firmly, though not exactly 
 closed, left 7.9 grains of cinder, which is equal to 61 per cent. 
 
 In order to ascertain what gases were evolved during this destruction 
 of the indigo, 1 introduced 5,28 grains into a small glass tube connected 
 with a mercurial trough. On applying the heat of a spirit-lamp, the va- 
 pour of indigo was formed, and condensed in the colder part of the tube, 
 but was at last destroyed by repeated applications of heat. A quantity of 
 water appeared in the tube, and 0.96 cubic inch of gas was found in the 
 receiver. On removing the tube, it was found to have lost in weight 0.71 
 grains, or 13.5 per cent, of the indigo employed. The water that was formed 
 had a disagreeable burnt ammoniacal smell. I found, on analyzing the gas 
 in the receiver, (making allowance for the common air of the apparatus, 
 and a small portion of gas remaining in the tube,) that it consisted, for 100 
 of indigo, of 
 
 Carbonic acid , , . . .... 2.8 
 
 Carburetted hydrogen and carbonic oxyde . . . 0.8 
 Azote . . . . , , . , , 1,9 
 
 The difference between the sum of these and the loss 13.5 
 
 was water, with a little ammonia .... 8.0 
 
 13.5 
 
 Sublimed Indigo, 
 
 " Indigo sublimes in long flat needles, which readily split, when they 
 ^^re bruised, into four-sided prisms. 
 
NOTES. 
 
 481 
 
 " Viewed at a particular angle, they have the most brilliant and intense 
 copper colour ; but when lying in heaps, they have a rich chestnut brown 
 colour, one that would be produced by mixing a very little yellow with 
 a bright but deep reddish purple. 
 
 " Besides these needles, this substance is found in the form of plates, 
 much broader than the needles, and extremely thin ; twisted sometimes 
 almost into tubes. These appear to the naked eye perfectly opaque. I 
 was not a little pleased, however, with their unexpected appearance, whe^ 
 seen through the microscope. Viewed obliquely, they appear still opaque, 
 and copper-coloured like the needles ; but when held perpendicularly to 
 the rays of light, they are seen to be transparent, and of a beautiful blue 
 colour, exactly similar to a dilute solution of indigo which has been acted 
 upon by sulphuric acid. Their intensity varies, according to the thickness 
 of the plate, from a blue just distinguishable from white, to one almost 
 black. The bronze colour which these crystals assume when in heaps, 
 is obviously a mixture of the copper colour with this blue, 
 
 " The vapour of indigo is transparent, and of a most beautiful reddish 
 violet colour, resembling a good deal the vapour of iodine, but sufficiently 
 distinguished from it by the shade of red. The sublimation takes place at 
 the heat of about 550° Fahrenheit ; for the vapour rises at a heat lower 
 than that of melting lead, and requires more than the melting heat of bis- 
 muth. Upon the rough bright surface of the lead, I observed some of the 
 crystals melt while the vapour was risuig ; but I have in no other circum- 
 stances remarked any thing like fusion, till the substance was decomposed. 
 Hence the melting point of indigo, its point of volatilization, and that at 
 which it is decomposed, are remarkably near each other. 
 
 " The specific gravity of sublimed indigo is 1.35. 
 
 " These crystals sublime when heated in open vessels, leaving no re= 
 sidue. In close vessels, the vapour is at first reddish-violet, as in the open 
 air : but as the heat advances, it acquires a tinge of scarlet ; and before it 
 is entirely decomposed, becomes deep scarlet, and then orange-coloured : 
 a quantity of charcoal is at the same time deposited. 
 
 " Action of Oils, — Of the essential oils, oil of turpentine dissolves at 
 its boiling heat as much indigo as gives it the fine violet colour of the 
 vapour of indigo ; but a slight reduction of temperature is sufficient to 
 precipitate the whole of it. The fixed oils and fatty substances, as they 
 may be heated to a higher degree, exert a more powerful action upon 
 indigo. None of them that I have tried act upon it at the heat of boiling 
 water ; but when the heat is increased, they gradually dissolve it, acquiring 
 the colour of its vapour much more deep than oil of turpentine does. If 
 the solution be cooled at this period, the indigo precipitates blue. As the 
 heat is continued, more of the indigo is dissolved ; but the colour of the 
 
 2 I 
 
482 
 
 NOTES. 
 
 solution begins to change ; it gradually inclines to crimson, and has then 
 begun to be destroyed. It is now green when cooled. Heated still more, 
 the solution is of a strong crimson ; then becomes orange ; and at last 
 when entirely decomposed, it is yellow, which colour it retains when cold. 
 
 Determination of the Ultimate Constituents of Indigo, 
 
 Carbon ...... 73.22 
 
 Azote 11.26 
 
 Oxygen . . . . .. . 12.60 
 
 Hydrogen 2.92 
 
 100.00 
 
 These numbers correspond very nearly to 
 
 1 atom of azote . . . 1.75 or 10.77 
 
 2 atoms of oxygen . . 2.00 12.31 
 4 atoms of hydrogen . • 0.50 3.08 
 
 1 6 atoms of carbon . . 12.00 73.84 
 
 16.25 100.00 
 
 " I have also made several analyses of v/ell-dried precipitated indigo ; 
 and allowing for a minute portion of lime which it contained, I got results 
 which agreed perfectly with the analyses of sublimed indigo. I find, too, 
 that both these substances are acted upon in the same manner by other 
 bodies. The different effect of heat depends obviously upon some dif- 
 ference in the mechanical arrangement of their particles. 
 
 " I made several attempts to amalgamate sublimed indigo, as well by 
 the process of Dobereiner, as by others which I thought more likely to 
 succeed, but in vain. I could in no case perceive the least alteration in 
 the fluidity of the quicksilver. 
 
 Action of Sulphuric Acid upon Indigo, 
 
 " When indigo is digested in concentrated sulphuric acid, it is well 
 known to suffer a remarkable change, being converted into a peculiar blue 
 substance, entirely different from indigo, with which the Saxon blue is 
 dyed. 
 
 " This substance has been so little attended to by chemists, that no one 
 has yet thought of giving it a separate name. I shall venture to propose 
 for it that of cerulin, from the colour of its solution. 
 
 " The mixture of the blue substance with sulphuric acid is a semifluid 
 which requires a considerable quantity of water to dissolve it. When 
 
NOTES. 
 
 483 
 
 potash is added to this sohition, previously filtered, a deep blue precipitate 
 is formed. I was surprised, however, when making the experiment, to find 
 the precipitate as plentiful before one-fourth of the acid was saturated, as 
 when the solution was made altogether neutral. To another portion, I 
 added potash previously saturated with sulphuric acid, and found the same 
 precipitate formed as with potash alone.* I threw the precipitate upon a 
 filter, and washed it with water, in order to examine whether it was the 
 pure colouring matter that had separated. The first washing did not 
 take away much of the precipitate ; the next, however, sensibly diminished 
 it ; but with the third portion of water it almost wholly disappeared. 
 
 " In order to discover the cause of this increased solubihty, I made a 
 saturated solution of sulphate of potash in water, and putting into it a 
 little of the blue pulpy substance that remained upon the filter, I agitated 
 it thoroughly. The solution remained altogether colourless. I found the 
 same to be the case when the muriate, the acetate, or any other salt of 
 potash, was employed. Alcohol, also, and ether, refused to dissolve this 
 substance. Put into pure water, however, it immediately dissolved, 
 forming the same deep blue solution that had passed through the filter. 
 
 " It seemed then only necessary to dissolve in water some salt of pot- 
 ash, to enable it to wash this substance without dissolving it. I found the 
 acetate to answer extremely well ; and this salt possesses the advantage 
 over the muriate or sulphate of not being precipitated by alcohol from a 
 weak solution in water, as they are. It may consequently be afterwards 
 removed by washings with alcohol. 
 
 " Such edulcorations with acetate of potash I repeated so often upon a 
 quantity of precipitate, taking it every time off the filter and agitating it 
 well in a phial with the liquid, that not 50V0 th of a grain of the original 
 soluble matter could be left in it. I then washed away the w^eak solution 
 of acetate of potash as well as possible by means of alcohol, without, 
 however, being able to remove all traces of that salt, although I used the 
 alcohol somewhat dilute. The small quantity that remained could not 
 materially all'ect the experiments I made upon it. 
 
 " A portion of the substance thus prepared, when burnt in a large 
 platina crucible, left a considerable quantity of ashes, slightly reddish 
 coloured, which dissolved almost enthely in water. What remained was 
 
 * That the solution of indigo in sulphuric acid is precipitated by neutral salts, is not a 
 new fact. Berthollet, (Art of Dyeing, ii. 277.) says, that the " fixed allialies saturated 
 with carbonic acid," as well as " alcohol, saturated solutions of alum, sulphate of soda, or 
 other salts containing sulphuric acid," form precipitates in this solution. My experiments 
 show, I think, that the effect does not depend upon the presence of sulphuric acid in the 
 precipitant ; that some sulphates have no such effect ; and that alcohol does not precipi- 
 tate the original solution at all. 
 
 2 I 2 
 
484 
 
 NOTES. 
 
 of a deep red, or rather brown colour, and was principally oxyde of iron. 
 The solution of the ashes was not at all alkaline : it gave a dense white 
 precipitate with muriate of barytes ; a very slight one with oxalate of 
 ammonifi ; and with sulphate of alumina large crystals of alum were 
 formed in a few hours. It was sulphate of potash. 
 
 " From these facts, I have no hesitation in concluding, that this precipi- 
 tate is a combination of cerulin with sulphate of potash. That salt forms 
 more than a fourth of its weight. It may, therefore, be called ceruleo- 
 sulphate of potash, 
 
 " The salts of soda also form precipitates in the solution of cerulin 
 with sulphuric acid, and these are likewise insoluble in solutions of potash 
 or soda, though soluble to a certain extent in pure water. When heated, 
 these ceruleo-sulphates dissolve even in solutions of their salts. On 
 cooling, the greater part falls down again in blackish grains ; a portion, 
 however, remaining in solution. The soda compound is evidently more 
 soluble than that of potash. The washings of the former precipitate, 
 with a cold solution of its acetate, are a little more coloured than those of 
 the potash precipitate, with its acetate of the same strength. This last 
 substance is totally insoluble in water containing one per cent, of acetate 
 of potash, or even a half per cent, after two or three edulcorations. I 
 have generally employed a solution of two parts dry acetate of soda in a 
 hundred of water ; and any quantity of such a liquid may be used with- 
 out the quantity of the substance being materially diminished. 
 
 " The salts of ammonia likewise form precipitates in the sulphuric solu- 
 tion of cerulin, when not much diluted. The precipitate dissolves readily 
 in hot solutions of ammoniacal salts, and again separates when cold, the 
 whole mass becoming curdy. I believe this substance to be a combina- 
 tion of cerulin with sulphate of ammonia, from the quantity of that salt 
 which I found in it, when as well washed as possible. It is much more 
 soluble, however, than the ceruleo-sulphates of potash and soda, and there- 
 fore cannot be washed so freely as these fixed alkaline compounds. Potash 
 and soda and their salts decompose it. It dissolves in great quantity in 
 boiling pure water, and in 40 or 50 parts of cold water. It has the 
 same general properties with the more insoluble compounds. 
 
 " A corresponding combination with barytes may be formed by decom- 
 posing ceruleo-sulphate of potash by muriate of barytes. The compourid 
 formed is extremely insoluble. An abundant blue precipitate is thus 
 formed in solutions of ceruleo-sulphate of potash, containing so little sul- 
 phuric acid, that they are not troubled in the slightest degree by a 
 barytic salt, when the cerulin has been previously destroyed by nitric 
 acid. 
 
 " Similar compounds may be formed with other bases, whose sulphates 
 
NOTES. 
 
 485 
 
 are difficultly soluble in water; but these I have not particularly exa- 
 mined. 
 
 ** The salts of magnesia have no power of precipitating cerulin from its 
 solution. The whole of the sulphuric acid in the original solution may be 
 saturated with magnesia, without any precipitate being formed. 
 
 Ceruleo-sulpliate of Potash, 
 
 " This substance is of so deep a blue, when wet with water, as to 
 appear absolutely black. When dry, it has a shining strong copper-red 
 colour. By transmitted light it is blue. It attracts water from the air 
 with great rapidity. In two hours, a portion which had been dried at- 
 tracted a tenth of its weight. 
 
 " It is soluble to a considerable extent in hot water. Cold water takes 
 np TToth of its weight of this substance, and forms a solution so deeply 
 coloured, that when diluted with 20 parts of water in a phial of an inch in 
 diameter, it may just be seen to be transparent. Water in a wine glass 
 containing - ^^'^^^ th of its weight of this substance is distinctly blue co- 
 loured. 
 
 " The saturated solution is precipitated by spring water, and by every 
 • liquid that I have tried, except distilled water. From this it appears, that 
 the mere presence of any foreign substance in pure water greatly dimi- 
 nishes its solubility. 
 
 " If the solution be diluted with 20 parts of pure water, it is still pre- 
 cipitated by solutions of the salts of potash and soda, lime, barytes, stron- 
 tian, lead, and mercury. An addition of sulphuric or muriatic acid does 
 not re-dissolve them. But neither ammonia nor any of its salts precipitate 
 this weak solution. None of the salts of magnesia, zinc, or copper, nor 
 the solutions of alum, sulphate of manganese, permuriate of tin, protosul- 
 phate or persulphate of iron, or nitrate of silver, precipitate it. It is not 
 precipitated by any of the acids, by infusion of galls, or by pure gelatin. 
 Alcohol and ether do not precipitate the weak aqueous solution, though 
 they do not dissolve any of the dry substance. Ceruleo-sulphate of pot- 
 ash dissolves readily in concentrated sulphuric acid, but not in concentrated 
 muriatic acid. 
 
 " When chloride of tin is mixed with the solution of this substance, its 
 colour is immediately changed to yellow. This yellow product is not very 
 soluble in water ; it becomes blue again on the addition of any substance, 
 as a salt of copper, capable of imparting oxygen to it. 
 
 " When heat is applied to the blue substance, it does not melt ; no 
 purple vapour is given off, and in consequence of its being defended by the 
 saUne matter, a strong heat long applied is necessary for its being reduced 
 to ashes. 
 
486 
 
 NOTES. 
 
 " When luminous objects, as the sun or moon, or the flame of a candle, 
 are viewed through the blue solution of this substance, of the proper de- 
 gree of intensity, they appear of a fine rich scarlet colour. It is worthy 
 of remark, that a single drop of nitrate or sulphate of copper, mixed with a 
 quantity of this solution, makes the same objects appear blue through it, 
 although the general appearance of the liquid is not in the least degree 
 altered. Zinc produces the same effect, though not so powerfully. Any 
 acid restores to these mixtures the property of making luminous objects 
 appear red, unless when a large quantUy of copper has been added, which 
 makes the liquid itself green. 
 
 " Sir H. Davy was the first to discover that a vegetable substance had 
 the power of precipitating in combination with certain neutral salts, which 
 are themselves abundantly soluble in water. The carbonates of potash, 
 soda, and ammonia, and the chlorides of tin and of iron, are among the 
 substances which that philosopher found undecomposed in combination 
 with tannin, in the precipitates formed by these salts in an infusion of galls. 
 It appears that cerulin acts a similar part, at least with the sulphuric salts. 
 I am not aware, however, that any substance has been hitherto described 
 by chemists which possesses the property I have found in the one here 
 treated of, that of dissolving in pure water, and refusing to do so in neutral 
 saline solutions which produce- no change upon it. But in common life, 
 some idea of this singular fact seems to have been long acted upon. Those 
 who are in the habit of washing printed gowns, particularly dark ones, of 
 colours not very permanent, always rinse them in a solution of common 
 salt, or at least in very hard water, before they hang them up to dry. The 
 salt, they say, fixes the colour, and prevents it from spreading out into the 
 white, which it always does when they are suffered to dry in a cool place, 
 without such immersion. 
 
 On the Phenomena which are exhibited during the Formation of Cerulin, 
 
 " Some of the phenomena which attend the action of sulphuric acid 
 upon indigo, have been noticed by different chemists. Bergmann, in 1776, 
 observed, that when indigo in powder was sprinkled upon sulphuric acid, 
 greenish clouds were produced, which became blue by the addition of a 
 drop of water. He added, that the same effect was produced, but more 
 slowly, without water, Hausmann, of Colmar, observed, that the acid in 
 contact with indigo became at first greenish-yellow, then deep green, and 
 at last blue. That gentleman remarked also, that the * effervescence and 
 disengagement of sulphurous vapours, always observed in making the blue 
 compound, leave no room to doubt that the acid exerts an action upon the 
 particles of indigo, and that we should be wrong in considering this as a 
 mere solution of indigo unaltered.' Berthollet, in his excellent work on 
 
NOTES. 
 
 487 
 
 dyeing, considers the change that takes place a species of combustion ; the 
 sulphuric acid furnishing the indigo with oxygen, and thereby being con- 
 verted into sulphurous acid. Dr. Bancroft, whose work appeared soon after 
 that of Berthollet, conceived the solution to be oxygenated indigo com- 
 bined with sulphuric acid. Hence he gave it the name of sulphate of 
 indigo. 
 
 ** Such, as far as my information goes, is the extent of our knowledge, 
 or rather our opinions, upon this subject. I shall state what appearances 
 I have myself observed during this process. 
 
 *' When indigo is put into sulphuric acid, it is dissolved, and the acid 
 assumes a yellow colour. When this solution is dropped into water, it 
 becomes instantly blue ; but the substance so produced is by no means the 
 same as that which is formed after some time, without the assistance of 
 water. It is indigo altogether unchanged, which precipitates, and leaves 
 the sulphuric acid perfectly colourless. If the yellow solution be exposed 
 to the open air in a watch-glass for a short time, the blue colour is restored 
 in the same manner, and the indigo falls down. This effect is produced, 
 not by the action of the air, but merely by the absorption of moisture. 
 
 " A considerable increase of heat takes place when the two substances 
 are put together. There can be little doubt that this is caused by the 
 sulphuric acid abstracting and combining with the 14.2 per cent, of water 
 contained in the indigo. 
 
 " If the yellow solution above mentioned be allowed to remain without 
 dilution, it becomes blue in a few hours ; and this is effected without the 
 assistance of air, as I found by making the experiment in a small phial, the 
 mouth of which was sealed up as soon as the materials were put together. 
 In consequence of the darkness of the liquid, these changes of colour can 
 only be observed in the thin film which wets the empty part of the phial, 
 when it is agitated. 
 
 " All the chemists who have treated of this process, mention the forma- 
 tion of sulphurous acid during the solution of indigo, and, attributing this 
 to the action of the indigo itself upon the acid, they naturally concluded 
 that that substance became oxydated at the expense of the acid. But these 
 chemists employed only the indigo of commerce in their experiments ; a 
 substance which contains more than half its weight of impurities, and great 
 part of these vegetable matter. I have found that it is these impurities 
 alone which decompose the acid ; for during the solution of sublimed 
 indigo not a trace of sulphurous acid can be detected, though the heat of 
 boiling water be applied for hours. Neither is there any production of hy- 
 posulphuric acid ; for, if there were, it would be decomposed by the heat 
 to which the hquid was exposed, or even by the presence alone of concen- 
 trated sulphuric acid, in which case sulphurous acid gas would be given off. 
 
488 
 
 NOTES. 
 
 " In less than twenty-four hours, if a slight degree of heat be applied, 
 the indigo is entirely converted into cerulin ; and, when mixed with water, 
 it passes through the filter, leaving no residue whatever. 
 
 On the Constitution of Cerulin, 
 
 " Since there is no production of sulphurous acid, nor absorption of air^ 
 during the formation of cerulin, it is clear that there can be no oxydation 
 either of the carbon or hydrogen previously existing in the indigo. No 
 carbon being deposited, and no gas evolved, during this process, prove also 
 that the azote exists in the new substance, in the same proportion to the 
 carbon that it does in indigo. That sulphuric acid does not enter into its 
 composition is evident from its precipitating with almost any sulphuric 
 salt, and carrying down no additional sulphuric acid of its own. It is only 
 in the amount of combined water, then, that any alteration can possibly 
 have taken place ; and to ascertain whether in this case there has been an 
 abstraction or an addition of w^ater to the indigo, it were only necessary to 
 convert a given weight of that substance into cerulin, and to weigh the 
 product, as M. de Saussure has done in the case of starch sugar. There 
 are difficulties, however, which prevent such an experiment from being 
 performed with any precision ; principally the large quantity of sulphuric 
 acid necessarily mixed with the product, and the solubility of the sub- 
 stance in water. I have contented myself with analyzing, by means of 
 peroxide of copper, the ceruleo-sulphate of potash, after having ascertained 
 as nearly as possible, by incineration, how much saline matter it contained. 
 But as this cannot be done with absolute precision, owing to the dissipa- 
 tion of a small portion of acid along with the vegetable matter, my results, 
 particularly with regard to the hydrogen, were by no means so uniform as 
 those which I obtained when operating upon indigo. All that is really 
 necessary in this case, is to determine the quantity of carbon, which may 
 be done with very little risk of error. The^ deficiency, after adding to the 
 carbon the proportion of azote, and of free hydrogen found in indigo, is 
 water. 
 
 " The ultimate composition of the substance is : 
 
 Carbon . . , . 57.18 
 
 Azote . . , . 8.79 
 
 Oxygen .... 29.32 
 
 Hydrogen . . . .4.71 
 
 100.00 
 
 This approaches so near to hidujo + ^ ivatcrj that there can be little 
 doubt such is its constitution. 
 
NOTES. 
 
 489 
 
 1 atom azote , , . 1.75 or 8.43 
 
 6 atoms oxygen . . , 6.00 28.92 
 
 8 atoms hydrogen . . 1.00 4.82 
 
 10 atoms carbon . . 12.00 57.83 
 
 20.75 100.00 
 
 " There is not the slightest proof that any combination exists between 
 cerulin and sulphuric acid in the original liquid. Alkalies, it is true, pre- 
 cipitate it from the solution ; and this has been supposed to be the effect 
 of a superior attraction on the part of the acid for the alkali, by which the 
 vegetable substance was left at liberty ; but such a theory falls to the 
 ground as soon as it becomes known that neutral salts produce exactly the 
 same effect ; that magnesia does not precipitate it at all, though it neutral- 
 izes the acid ; and that cerulin is itself soluble in water. Cerulin dis- 
 solves, indeed, in sulphuric acid, and that more abundantly than in water ; 
 but this does not argue the formation of a compound which we are entitled 
 to call sulphate of indigo. Such a solution differs in no respect from that 
 of resins and other organic bodies in the same acid, or even from the solu- 
 tion of these substances in alcohol or ether. 
 
 " Those who are fond of speculating upon the manner in which the ele- 
 ments of water are arranged in organic bodies, may find it curious that 
 sulphuric acid should abstract water from indigo, and not from cerulin, a 
 substance which contains three times as much oxygen and hydrogen ; or 
 that the same acid which robs indigo of its water, should immediately 
 restore three times as much. 
 
 On a new Substance produced from Indigo by means of Sulphuric Acid, 
 
 " While engaged with these experiments, I discovered, that if the action 
 of sulphuric acid upon indigo be stopped at a certain point, a new sub- 
 stance, altogether different from cerulin, is produced, possessing rather sin- 
 gular properties. It is formed at the instant that indigo changes from 
 yellow to blue by the action of sulphuric acid. 
 
 By the following process, it is obtained of greater purity than by any 
 other method I have been able to discover. Prepare a quantity of indigo 
 by boiling it in sulphuric acid diluted with three parts of water, and drying, 
 after it is well washed. By such treatment, it is deprived of more than a 
 third of its weight of impurities. Mix one part of this purified indigo with 
 seven or eight parts of concentrated sulphuric acid in a stoppered phial, 
 and agitate the mixture occasionally, till it becomes of a bottle-green 
 colour. Then mix it with a large quantity of distilled water, and throw it 
 
490 
 
 NOTES. 
 
 upon a filter. By continuing to wash the ^Iter with distilled water, the 
 liquid which at first passes through colourless becomes more and more 
 blue, and after some time all the indigo which has been changed passes 
 through. The colourless washings must be thrown away. The blue liquid 
 contains the new substance in solution, and does not differ in appearance 
 from a solution of cerulin. On the addition of muriate of potash, the new 
 substance precipitates of a most beautiful reddish-purple colour, exactly 
 similar to the colour of the vapour of indigo. Let this precipitate be 
 thrown upon a filter, and washed with distilled water, till the liquid which 
 passes through forms no longer a whitish, but a red precipitate with nitrate 
 of silver. It may then be dried. 
 
 " From the property possessed by this substance of becoming purple- 
 coloured on the addition of a salt, 1 have called it phenicin, from the 
 Greek word (poTvi^, purple ; and, to prevent circumlocution, I shall here- 
 after make use of this term. 
 
 " This substance, prepared with muriate of potash, is, when dry, of a 
 brownish black colour. Heated in a crucible, it gives off a little vapour of 
 indigo. I was at first uncertain whether this might not proceed from indigo 
 formed by the decomposition of part of the phenicin by the heat ; but I 
 shall state a fact which shows that the indigo may have another source, and 
 that it may exist in a small quantity in the purple substance. After the 
 filter is washed till the washings are very slightly blue-coloured, the liquid 
 that passes through is precipitated blue, instead of red, by muriate of pot- 
 ash, and the precipitate consists of indigo with a little phenicin. Thus it 
 appears that even indigo is, in certain circumstances, capable of dissolving 
 in water. By drying the phenicin, prepared as I have stated, and redis- 
 solving it, a small quantity of indigo remains ; but still the phenicin yields 
 a little purple vapour when heated. 
 
 " When the purple substance is burnt, it leaves about fifteen per cent, 
 of ashes, which dissolve in water, and consist of sulphate and muriate of 
 potash. 
 
 " Phenicin dissolves both in water and alcohol, and the solution in both 
 cases is blue. It is precipitated again of its original purple colour by all 
 saline substances whatever. Different salts, however, possess different 
 powers of precipitation. Thus muriate of ammonia, chlorate and prussiate 
 of potash, and muriate of soda, precipitate the phenicin entirely from about 
 sixty times their weight of any aqueous solution ; and nitrate, muriate, 
 and sulphate of potash, from about 100 times their weight. But the sul- 
 phates of magnesia, zinc, and copper, precipitate 2000 times their weight of 
 a solution of phenicin ; sulphate of iron about 3000 times, and alum and 
 muriate of lime as much as 8000 times. 
 
 The phenicin being previously combined with a salt of potash, is not 
 
NOTES. 
 
 491 
 
 altered by being again precipitated by any alkaline salt. These salts do 
 nothing more then saturate the water to such a degree that the substance 
 is no longer capable of dissolving in it. But the earthy and metallic salts 
 combine with this substance, and displace the salt of potash previously 
 united with it ; and I have observed very little difference in the quantities 
 necessary to precipitate solutions of different strengths. The precipitates 
 formed by lime, barytes, alum, and copper, are totally insoluble in pure 
 water, however well they may be washed. Those formed by iron and 
 magnesia dissolve to a small extent, when freed from their former menstrua 
 by filtration. Their solution is purple-coloured. 
 
 " Acids have no effect in preventing the precipitation of phenicin by 
 saline bodies ; and the precipitates once formed are not redissolved in the 
 same liquid by the assistance of heat. 
 
 " The method which I have given for preparing the new substance is 
 tedious. As only a small part of the indigo is converted into phenicin, the 
 quantity "obtained each time is very small, and requires a great quantity of 
 distilled water, and a long time to filter. But if we allow the indigo to be 
 wholly converted into phenicin, its solution cannot be made to pass 
 through any filter, however porous, or however well washed it may have 
 been with water or ammonia. It was by accident that I discovered the 
 possibility of filtering it when only a small portion of the indigo had had 
 time to be changed ; and it was only by preparing it in this manner that I 
 found the purple colour to be owing to the presence of saline matter, and 
 its own colour to be like that of cerulin. 
 
 " The following is a method of preparing this substance in greater quan- 
 tities, though not so pure. Mix together one part of indigo in powder, and 
 ten parts of concentrated sulphuric acid, in a phial, and agitate from time 
 to time, till the blue colour, which the indigo loses at first, is completely 
 restored. This, at the ordinary heat of summer, requires nearly three 
 hours. At lOO^'Fahr. it is effected in about twenty minutes ; and indigo 
 mixed with sulphuric acid, at the heat of boiling water, becomes blue the 
 instant the mixture is made. At 45'' Fahr. ten or twelve hours are neces- 
 sary ; and at lower degrees of heat, a still longer time, supposing always 
 the quantity of materials small enough to cool very soon after mixture to 
 the stated point. Pour this mixture into a large quantity of distilled 
 water, and filter. Take the precipitate off the filter, wash it well with 
 distilled water containing the proportion of muriate of ammonia necessary 
 to prevent the substance from dissolving in it, and filter again. Dissolve 
 anew the precipitate in a large quantity of distilled water ; heat the solu- 
 tion to drive off any particles of air which might prevent the impurities 
 from subsiding, and let it stand two or three days in a tall vessel. Then 
 draw off with a syphon as much as may be thought perfectly clear, leaving 
 
492 
 
 NOTES. 
 
 the remainder to be washed with more distilled water. Add to the solu- 
 tion any alkaline salt, till the substance be precipitated ; then throw it 
 upon a filter, and wash with distilled water till the liquid refuses to pass 
 through. 
 
 " When a solution of phenicin is precipitated, the liquid that remains 
 is always more or less coloured with cerulin ; and however often this be 
 repeated upon the same material, a little cerulin is always left. If it has 
 been heated, more cerulin is formed. It follows from this that phenicin is 
 changed into cerulin by the action of water alone. 
 
 " Phenicin dissolves in the water of liquid ammonia without injury ; 
 but the fixed alkalies destroy it, though not very readily. Chloride of 
 tin precipitates the solution, but gradually redissolves the precipitate, 
 forming a yellow solution ; and the phenicin is thrown down again of its 
 own colour, by the salts of copper. 
 
 Phenicin dissolves readily in concentrated sulphuric acid, forming a 
 blue solution ; and if this be poured immediately into water, the greater 
 part of it is precipitated again, the impurities of the acid being sufiicient 
 to prevent its solution in water. A portion is converted into cerulin, which 
 remains in solution. When allowed to remain dissolved in sulphuric acid, 
 it is soon entirely converted into cerulin ; consequently, in preparing phe- 
 nicin by the second process, it is impossible to prevent the formation of a 
 certain portion of cerulin. 
 
 Constitution of Phenicin, 
 " The facts which I have stated, to prove that cerulin differs from indigo 
 only containing more or less water, equally apply to this substance. 
 
 " One grain of pure phenicin produced 5.085 cubic inches of dry car- 
 bonic acid gas, which contain 0.6462 grains of carbon. Hence, calculating 
 as in the case of cerulin, the substance consists of 
 
 Carbon . . . . . 64.62 
 
 Azote 9.91 
 
 Oxygen . . . . . 21.49 
 Hydrogen , . . . 3.98 
 
 100.00 
 
 This is very nearly indigo + 2 water, and its atomic proportions may 
 be thus stated : — 
 
 1 atom azote . . 1.75 or 9.46 
 4 atoms oxygen . . 4.00 21.62 
 6 atoms hydrogen . 0.75 4.05 
 16 atoms carbon . . 12.00 64.87 
 
 18.50 100.00 
 
NOTES. 
 
 493 
 
 " The experiments of Mr. Smithson, related in the Philosophical 
 Transactions, have given us very correct ideas on the nature and numher of 
 the vegetable colouring matters. It is sufficiently obvious thatphenicin is 
 not the principle which colours any of the purple or blue vegetables exa- 
 mined by that chemist. I collected a number more of such purple flowers 
 as are most commonly met with, and dipped them separately in concentrated 
 julphuric acid ; but instead of becoming blue, they were uniformly changed 
 to red, and formed red-coloured solutions on the addition of water. Future 
 inquiries, therefore, must determine whether phenicin exists ready formed 
 in nature, either in the blue or in the purple state. 
 
 " Alcohol modifies remarkably the action of sulphuric acid upon indigo. 
 A mixture of three parts of alcohol of specific gravity 0.84, and two parts 
 of acid, dissolves indigo without rendering it yellow, and the solution may 
 even be filtered through strong paper. Probably a larger quantity of pure 
 alcohol might be employed. On the addition of water, the indigo is pre- 
 cipitated without alteration ; and if common indigo has been used, resin 
 precipitates along with it. It may remain dissolved in this mixture any 
 length of time without conversion into phenicin. A solution of phenicin 
 in sulphuric acid may also be mixed with alcohol without precipitation, and 
 the acid is rendered incapable of converting it into cerulin." 
 
 Mr. Holt states that the solution of indigo in sulphuric acid is com- 
 pletely deprived of colour by adding to it fiHngs of zinc or iron. When- 
 ever the colourless, or slightly grey-coloured solution, suffers the contact 
 of air, the blue colour reappears. It was previously well known that sul- 
 phuretted hydrogen blanched the above solution of indigo. 
 
 Note HH. p. 290. 
 
 A VALUABLE paper on the cultivation of woad in England was pub- 
 lished by Mr. John Parrish in the 12th volume of the Letters of the 
 Bath Agricultural Society. It is reprinted in Tilloch's Magazine, vol. 
 xxxviii. p. 43. 
 
 Note II. p. 341. 
 
 The first person who established in this country a factory for dyeing Adri- 
 anople madder-red, was M. Papillon, who in the year 1790 obtained a pre- 
 mium from the Commissioners and Trustees for Manufactures in Scotland, for 
 communicating the details of it to Dr. Black, on condition that it should not 
 be divulged for a certain term of years, during which M. Papillon was to 
 have the sole use of his own secret. The term being expired, the process 
 was published. • It resembles pretty closely the method described in the 
 text by M. Berthollet. Those who wish to compare them, will find M. Pa- 
 pillon's in the 18th volume of Tilloch'^ Magazine, p. 43. 
 
494 
 
 NOTES. 
 
 M. Vitalis, in his valuable treatise on dyeing, published in 1823, 
 (^Cours Elementaire de Teinture^ has entered at considerable length into 
 the description of the Turkey-red dye, with which his situation at Rouen 
 had made him familiar. I shall here note those points in which he appears 
 to differ from M. Berthollet, or is more precise. 
 
 In the second operation, he states, that from 25 to 30 pounds of sheep's 
 dung are commonly used for 100 pounds of cotton yarn. The dung is 
 first steeped for some days in a ley of soda, of 12° or 14° Tw. This is 
 afterwards diluted with about 1 25 gallons of a weaker ley, and at the 
 same time bruised with the hand in a copper basin, whose bottom is pierced 
 with small holes. The liquor is then poured into a vat containing five or 
 six pounds of fat oil, {Gallipoli^ and the whole are well mixed. The 
 cotton is washed in this, as prescribed by M. Berthollet. The hanks of 
 cotton yarn are then stretched on perches in the open air, and turned from 
 time to time, so as to make it dry equally. After receiving thus a certain 
 degree of desiccation, it is carried into the drying house, which is heated 
 to 50° Reaumur, (144° Fahrenheit,) where it loses the remainder of its 
 moisture, which would have prevented it from combining with the other 
 mordants, which it is afterwards to receive. What is left of the bath is called 
 avancesy and is added to the following bath. Two, or even three dung 
 baths are given to the cotton, when it is wished to have very rich colours. 
 When the cotton has received the dung baths, care must be taken not to 
 leave it lying in heaps for any length of time, lest it should take fire ; an 
 accident which has occasionally happened. 
 
 Third Operation, — Oil or White Bath, 
 
 This bath is prepared by pouring in six pounds of fat oil, 12 J gallons 
 of soda ley, at i° or sometimes less, according as, by a preliminary trial, 
 the oil requires. This bath ought to be repeated two, three, or even a 
 greater number of times, as more or less body is to be given to the 
 colour. 
 
 Fourth Operation. — Salts, 
 
 To what remain^ of the white bath, and which is also styled avances, 
 about 25 gallons of soda ley, of two or three degrees, are added. Through 
 this the cotton is passed as usual. Formerly, it was the practice to give 
 two, three, or even four salts. Now two are found to be sufficient. 
 
 Fifth Operation. — Degraissage, 
 
 The cotton is steeped for five or six hours in a tepid solution of soda, 
 of 1° at most ; it is set to drain, is then sprinkled with water, and at the 
 end of an hour is washed, hank by hank, to purge it entirely from the oil. 
 
NOTES. 
 
 495 
 
 What remains of the water of degraissage, serves for the scouring, or first 
 operation. 
 
 Six til Operation, — Galling, 
 
 For 100 pounds of cotton, from 20 to 25 pounds of galls in sorts must 
 be taken, which are bruised and boiled in about 25 gallons of water, till 
 they crumble easily between the fingers. The galling may be done at 
 two operations, dividing the above quantity of galls between them, which 
 is thought to give a richer and more uniform colour. 
 
 Seventh Operation, — Aluming, 
 
 The aluming of 100 pounds of cotton requires from 25 to 30 pounds 
 of pure alum, that is, alum entirely free from ferruginous salts. The alum 
 should be dissolved without boiling, in about 25 gallons of river or rain 
 water. When the alum is dissolved, there is to be poured in a solution 
 of soda, made with the sixteenth part of the weight of the alum. A 
 second portion of the alkaline solution must not be poured in till the 
 effervescence caused by the first portion has entirely ceased, — and so in 
 succession. The bath of saturated alum, being merely tepid, the cotton 
 is passed through it, as in the gall bath, so as to impregnate it well, and 
 it is dried with the precautions recommended above. The dyers who gall 
 at two times, alum also twice, for like reasons. 
 
 Eighth Operation, — Washing away the Alum, 
 
 Ninth Operation, — Maddering, 
 
 For twenty-five pounds of cotton, 6i gallons of blood are prescribed 
 and 100 gallons of water. Whenever the bath begins to warm, fifty 
 pounds of madder are diffused through the bath. Sometimes the mad- 
 dering is given at two operations, dividing the madder into two portions. 
 
 Tenth Operation, — Brightening, 
 
 The brightening bath is prepared always for 100 pounds of cotton, with 
 from four to five pounds of rich oil, six pounds of Marseilles white soap, 
 and 150 gallons of soda ley at 2°. 
 
 Eleventh Operation, — Rosing, 
 
 This is done with solution of tin, mixed with soap water. 
 
 Two systems for Turkey red are known at Rouen. The first is 
 called the grey course, the second the yellow ; (marche en gris, and 
 ynarche en jaune?) 
 
 The grey course takes its name from the cotton being subjected to the 
 
496 
 
 NOTES, 
 
 maddering immediately after it has received the oily preparations, and the 
 mordants of galls and alum, which give it a grey colour. 
 
 The yellow course is so called, because in this system the cotton, after 
 having received a first time the oily preparations, as well as the mordants 
 of galls and alum, is not exposed to the maddering till it has passed a , 
 second time through the same preparations and the same mordants, which 
 give it a yellow colour. It is this second manner of working the Turkey red, 
 which is called, in the phraseology of the dye-house, remounting on the galls. 
 
 The following table exhibits the difference which exists between these 
 two courses : — 
 
 Grey Course. 
 
 Yellow Coarse. 
 
 Boiling 
 
 Boiling 
 
 T\ 1 1.1 
 
 Dung baths 
 
 Dung baths 
 
 White baths 
 
 White baths 
 
 Salts 
 
 Salts 
 
 Degraissage 
 
 Degraissage 
 
 Galling 
 
 Galling 
 
 Aluming 
 
 Aluming 
 
 Washing off the alum 
 
 Washing off the alum 
 
 Maddering 
 
 White baths 
 
 Brightening 
 
 Salt 
 
 Rosing 
 
 Degraissage 
 
 
 Galling 
 
 
 Aluming 
 
 
 Washing off the alum 
 
 
 Maddering 
 
 
 Brightening 
 
 
 Rosing 
 
 The grey course, as well as the yellow, is susceptible of a great many 
 combinations and varieties, both in the order and number of the operations 
 relative to each. The following are some examples with developments, 
 which cannot fail to interest dyers. 
 
 Grey Course for 100 Pounds of Cotton, 
 
 Scouring in a soda liquor at 2^°, or with the waters of degrais- 
 sage at 2^. 
 
 Dung hath, with 25 pounds of dung, and six pounds of oil— stove- 
 drying. 
 
 Dung bath, — idem —drying— idem. 
 
 White bath, with five pounds of oil, and soda liquor, at \\ or 2*'— 
 drying. 
 
 White bath, — idem — drying. 
 
NOTES. 
 
 497 
 
 One or two salts^ the first at 2"", the second at 3" — drying. 
 
 Degraissoge in pure water of a temperature equal to that of the atmo- 
 sphere in summer, and between 15** and 18° Reaumur (66 and 72'' Fahr.) 
 in winter. The cotton is kept in the water for an hour or two. It is then 
 taken out, wrung at the jack, and dried. 
 
 White bath, as above. 
 
 White bathi idem. 
 
 White bathf idem. 
 
 Degraissage, as above, with this difference, that it is washed well before 
 wringing, and then dried. 
 
 First galling, with seven pounds of galls in sorts, or galls of Istria — 
 drying. 
 
 Second galling, with 14 pounds of sumach, which is just brought to 
 boil ; it is then refreshed (with cold water), passed through a sieve, and 
 the cotton is turned through as hot as possible— drying. 
 
 First aluming, with 13 pounds of purified alum ; it gets next a slight 
 washing, but is not dried. 
 
 Second aluming, with 12 pounds of the same alum — thorough washing 
 — wringing — no drying. 
 
 Maddering y with seven quarters of a pound of Provence lizari for every 
 pound of cotton. Only 25' pounds are dyed at a time, which must be 
 allowed to cool after coming out of the boiler before it is washed ; then it 
 is to be wrung, but not dried. 
 
 Brightening, with soda liquor at 1^^ or with what remains of the water 
 of degraissage ; to which three or four pounds of white soap may be 
 added. The cotton must be boiled for four or five hours in a copper 
 closed with a cover, but not so tight as to hinder the steam from escaping. 
 The ebullition is to be kept up, till a pattern, which has been observed 
 from time to time, has reached the proper point. The cotton is allowed 
 to cool in the boiler, is then well squeezed, washed in the river, 
 wrung at the jack and pin, and, without drying, subjected to the next 
 operation. 
 
 Rosing^ with 1 2 pounds of white soap dissolved in a sufficient quantity 
 of water. When the soap is dissolved, there is poured into the copper a 
 solution of a pound or a pound and a half of salt of tin in two quarts of 
 lukewarm water, to which about a third of a bottle (bouteille) of nitric acid 
 at 36"^ of the areometer has been added. It is made to boil for four or 
 five hours, and the cotton is withdrawn whenever a pattern has attained 
 the proper hue. 
 
 If the first rosing do not bring the cotton to the desired tint, a second, 
 similar to the preceding, may be given ; but only eight pounds of soap 
 should be employed. 
 
 2 K 
 
498 
 
 NOTES. 
 
 Yellow Course, in like maimer y for 100 Pounds of Cotton, 
 Scouring, as in the grey course. 
 
 Two baths of sheep's dung, each along with five or six pounds of oil — 
 drying. 
 
 Two white baths ^ each with six or eight pounds of oil — drying. 
 Two salts, each at 2° of the hydrometer of Baume, (2i'' Tw.) 
 Degraissage, as usual — washing — then drying. 
 First galling, with eight pounds of nut-galls — drying. 
 First aluming, with thirteen pounds of pure alum — washing without 
 drying— wringing, and drying. 
 
 Three white baths, each with six pounds of oil — drying. 
 Two salts, each at 2° — drying. 
 
 Second galling, with four pounds of galls, and twelve pounds of sumach 
 — drying. 
 
 Second aluming, with thirteen pounds of pure alum — drying. 
 Washing off the alum very carefully — wringing — drying or not, at 
 pleasure. 
 
 Maddering, with two pounds of lizari of Provence per pound of 
 cotton. 
 
 Brightening, as in the grey course. 
 First rosing, as in the grey course. 
 Second rosing (if wanted) as in the grey course. 
 
 The system of operations indicated in either of the above courses, appears 
 to M. Vitalis so preferable to every other, that he wishes dyers to follow 
 them, leaving them always at liberty to give baths a little more charged 
 with oil, more of them, or some additional salts, &c. 
 
 The grey course is usually followed for making the ordinary Adrianople 
 reds ; and the yellow course is reserved for reds of the first quality in pomt 
 of lustre and durability. 
 
 It is also by the yellow course that linen or hemp must be treated. 
 
 M. Vitalis states, in his Manuel du Teinturier, that the bisulphate of potash 
 may be used instead of the salt of tin for rosing, and that it gives to the 
 red a peculiar shade very agreeable to the eye. In vain, he observes, 
 should we attempt to give a fine red with only 25 pounds of oil for 100 of 
 cotton. No less that 40 pounds are employed, and very commonly 50, or 
 even more. Nor will sumach replace the galls ; nor will a lower heat 
 answer in the drying-stove. 
 
 The avances (residuary liquors) in which the cotton has been worked 
 after the galling are good for nothing, and must be thrown away. When 
 the Adrianople red is finished, the colour is much improved by preserving 
 the cotton for one or two months shut up pretty tight in hempen bags. 
 
NOTES. 
 
 499 
 
 This seems to show that the mordants have not completely exhausted 
 their action in the operation itself, and that the affinities between them 
 and the colouring matter require a certain time to produce their whole 
 effect. 
 
 A good Adrianople red supports for ten minutes the action of nitric acid 
 at 28° Tw., without suffering any sensible change. By letting it remain 
 longer in the acid, or by employing a stronger one, the cotton becomes 
 more and more orange, and finally loses its colour. The simple madder 
 reds, exposed to the same test, disappear in less than three minutes. 
 
 Cottons which have not been suitably worked in the preparations, come 
 out of the maddering with a thin colour, sometimes of a brick hue. Before 
 brightening these cottons, they ought to get new oil baths, and the opera- 
 tions should be repeated as if they had not been dyed. The brightening 
 and rosing will have a little less power than in ordinary cases. Cotton 
 dyed Turkey red is sometimes too much charged with oil, and the excess 
 rises in time to the surface of the cotton, or of the stuffs made from them. 
 The surface is then sprinkled with small white points, which alter the 
 beauty of the colour. This inconvenience is remedied by dipping the 
 cotton for some time in, or by passing it or the stuffs through, a hot 
 bath of soap. Ten or twelve pounds are sufficient for 100 pounds of 
 materials. 
 
 Cotton yarns for warp being more twisted than those for woof, require 
 more manipulation to give them an equally good colour. 
 
 The object of the scouring, or first operation in the Turkey red process* 
 is to free the stuff to be dyed from an oily or resinous matter which enve- 
 lopes their fibres, and fills the interstices between their filaments. It is 
 this oily or resinous matter which renders these substances less white, and 
 which weakens their affinity for water, and for the colouring matters which 
 they are to receive. The baths of sheep's dung have been supposed to 
 make the cotton or linen fibres approach more to the nature of animal sub- 
 stances. This albumino-gelatinous matter, dissolved in the alkaline ley of 
 soda, is in the most favourable state for entering into combination with the 
 cotton. 
 
 The white baths, which follow those of dung, co-operate with the latter, 
 giving to the cotton the oily principle, for which cotton is known to have a 
 great affinity, and which, moreover, enjoys the property of combining with 
 the colouring matter. 
 
 But the superfluous quantity of oil, diffused merely on the surface of 
 the fibres, would obstruct the assumption of the dye, and is therefore to 
 be removed by the degraissage ; an operation much more important than is 
 commonly imagined, and which therefore requires to be conducted with 
 every possible care. 
 
 2 K 2 
 
500 
 
 NOTES. 
 
 The washings have in general the same object as the chgraissage, and 
 require the same attention. 
 
 As to the desiccation, which must be performed after the greater part of 
 the operation?, its necessity will readily be recognized, by considering that 
 the moisture introduced into the cotton by the application of a first mor- 
 dant, would necessarily become an obstacle to the introduction and com- 
 bination of a subsequent mordant. For this reason, it is not sufficient 
 always to dry in the air, but the desiccation must be completed in a stove 
 heated to 50° or 55° Reaumur, (144° to 156° Fahr.,) especially during 
 winter, and when the weather is moist. 
 
 It will be impossible to give a good explanation of the process of 
 galling till the principles furnished by the nut-galls be more exactly 
 known. It appears certain that they contain a peculiar acid, named from 
 them the gallic. But what is the nature of the tannin which always 
 accompanies that acid ? The galls probably form not only an energetic 
 mordant, by operating directly on the cotton which has received the oily 
 preparations, but also act by attracting the alumina. 
 
 The alum plays a very important part in Turkey red dyeing, but its 
 functions are not altogether explained. Some drops of the decoction of 
 galls poured into a solution of alum determine, according to the late Mr, 
 Henry, a precipitate of a white colour, which appears to be alumina 
 separated from the sulphuric acid. When galled cotton is passed through 
 a solution of alum, it may therefore be supposed that a portion of the 
 alumina is attracted to the cloth by the agency of the galls. The tem- 
 perature of aluming ought to be rather low, viz. 18° or 20° Reaumur, (about 
 75° Fahr.,) since, at a greater heat, the alumina might be too rapidly and 
 abundantly thrown down, and much of what is so hastily deposited might 
 not combine with the galls. This compound of galls and alumina forms a 
 complex mordant, which unites with the mordants that the oily principle 
 and the dung have already furnished. 
 
 We may also remark, that it is not without reason that, in the aluming 
 for Turkey red, the precaution is taken of adding to the ordinary alum a 
 certain quantity of alkali (an ounce of soda to a pound of alum.) Perhaps 
 the oily baths contribute to the fixation of the alumina, forming with this 
 earth a species of aluminous soap, so much the more permanent, as it is 
 altogether insoluble in water. But the alkali must not be caustic, as 
 Macquer had conjectured; for alumina, dissolved from alum in a caustic 
 ley, will not answer for furnishing a mordant to the Adrianople madder- 
 red. The blood adds no colouring matter to the madder in the dyeing 
 operation. The dull and dark red which the cotton takes in the mad- 
 dering is by no means an agreeable shade. This sombre hue must be 
 removed from it, and a bright decided red brought out. This effect is 
 
NOTES. 
 
 501 
 
 obtained by the brightening, which lays bare the red tint that had been 
 masked by the brown colouring matter, which is dissolved and carried off 
 by the brightening bath. 
 
 By the rosing the cotton acquires a lustre and vivacity far superior to 
 what the brightening can give. To obtain this effect, the cotton is set to 
 boil for four or five hours, as has been stated, in a solution of white soap, 
 to which a solution of salt of tin (muriate) is added, along with a certain 
 quantity of nitric acid, at 66° Twaddell. It would seem that in this 
 operation the soap and the salt of tin mutually decompose one another, — 
 that the muriatic, as well as the nitric, which are added, seize the soda 
 constituent of the soap, — that the oil separated from the alkali unites to the 
 oxyde of tin to form an acid metallic soap, whereby the red is finally 
 brightened, acquiring that lustre so pleasing to the eye. 
 
 The following process is that followed by a practical dyer of Turkey red 
 in Scotland, for 1 cwt. of cloth or yarn : — 
 
 First, Boil the goods with white soap and pearl ash, or soda ley. Twelve 
 pounds of white soap are dissolved in water, in a copper, along with six gal- 
 lons of the ley, pretty strong. The boiling is continued for five or six hours. 
 
 Second, The sheep's dung liquor. To make this, take twelve gallons 
 of soda liquor, 3° Tw. (sp. gr. 1.015,) two gallons Gallipoli oil, six 
 gallons of sheep's dung, twenty-four gallons of soda liquor, 5° Tw. 
 (sp.gr. 1.025.) 
 
 Tramp the cloth or yarn well in this liquor, then hang it in the air to 
 dry, and next in the stove. 
 
 The dunging is repeated a second and a third time, as above, drying the 
 goods after each repetition. 
 
 The yarn or cloth is to be steeped all night in warm water, at 100° Fahr. 
 with four gallons of soda liquor, 12° Tw. (sp. gr. 1.060.) Out of this it is to 
 be well wrung next morning, hung in the air, and, lastly, dried in the stove. 
 
 Take now twelve gallons of weak soda liquor, 3° Tw. (sp.gr. 1.015,) 
 Gallipoli oil, two gallons, soda liquor, 5° Tw. (sp. gr. 1.025,) thirty 
 gallons. Tramp the cloth or yarn in this mixture three or four times; then 
 put in the air, and finish in the stove every time. 
 
 Steep for cleaning away the OiL 
 
 Steep the goods in warm water at 140° Fahr., with four gallons of soda 
 liquor for each cwt. Wring it out next morning, wash well and dry it, 
 when it is ready for the galls. 
 
 Gall Liquor, 
 
 Take twenty-four or twenty-five pounds of nut-galls, and boil them for 
 eight hours. Take the clear liquor, and tramp the cloth or yarn as warm 
 
502 
 
 NOTES. 
 
 through this liquor as the skin can bear ; wring, put in the air, and then in 
 the stove. 
 
 Alum Liquor. 
 
 Take 25 pounds of alum, — dissolve in warm water ; add 4 gallons of 
 soda, 12° Tw. (sp. gr. 1.060.) Next morning take the clear liquor, put it 
 into a copper, and warm it as hot as the hands can bear. Tramp the stuff 
 through this liquor, wring, and put in the stove to dry. 
 
 Second aluming as above. 
 
 Steep the alumed goods in lukewarm water all night, next day wash 
 them well in the river, then they are ready for drying. 
 
 To dye twelve dozen of Cloths, (^Pieces,) 
 
 Allow 2 pounds of madder to each pound of cloth, bring to the boiling 
 point in an hour, and keep boiling for half an hour. Then enter the goods 
 into the copper, adding 2 gallons of blood well mixed. (The blood 
 should surely be added to the cool, or merely tepid water.) Let the 
 goods be now well washed and dried. For the cue, take half soda and half 
 pearl ashes, half a gallon of oil, add as much water as will bring the liquor 
 to No. 6 of the hydrometer, (sp. gr. 1.030.) But the oil must have been 
 previously mixed with twelve gallons of soda liquor, 3° Tw. (sp. gr. 1.015.) 
 Put the goods through this liquor as through the white bath ; wring and 
 stove-dry. 
 
 For Clearing, 
 
 Fill a copper with clean water ; dissolve 4 or 5 pounds of white soap 
 in it, and half a pound of pearl ashes. Boil slowly from six to eight hours ; 
 then wash and wring the goods. Lastly, *fill a copper with clean water, 
 adding a pound or two of white soap, and boil the goods an hour or two. 
 
 They are now finished. 
 
 Mr. John Thomson of Glasgow published in the Annals of Philosophy, 
 vol. viii. p. 463, some ingenious ideas on the theory of the Turkey red 
 process. " Silk and worsted," says he, *' have a natural varnish which 
 cotton does not possess." To supply this defect, the repeated immersions, 
 followed by exposure to the atmosphere, and to the heated air of a stove, 
 may give the oil the proper consistency, by the absorption of oxygen, for 
 forming a varnish, with which the colouring matter unites, and through 
 which it may be said to shine, which causes that superior brilliancy which 
 the goods attain when they are cleared, or, as it may be called, polished. 
 I therefore presume, that the fixedness and brilliancy of the colour will 
 depend on the quantity of oil imbibed, as every repetition of drying pre- 
 
NOTES. 
 
 503 
 
 sents new fibres to be varnished with an additional quantity ; for 1 have 
 always found, that the permanency was in proportion to the number of 
 manipulations in the saponaceous liquor, and a proportionable freedom 
 could also be used in reducing or clearing. The white immersions, omit- 
 ting the sheep's dung, are just applying successive coats of varnish. Clear- 
 ing is never attempted from the madder copper, without immersing the 
 goods again in soda and oil, and drying them in a stove, which I consider 
 to be also supplying them with an additional coat.* 
 
 The alkaline ley occasions a greater separation in the particles of the 
 oil, by which it combines more closely with the fabric of the cloth. The 
 sheep's dung in the first immersions may serve as a covering or great coat, 
 to keep the goods moist for a considerable time, that they may more fully 
 imbibe the liquor, by preventing the evaporation from being too quick in 
 the great heat to which they are exposed. 
 
 After the frequent immersions the cloth feels like leather, no doubt from 
 a superfluity of liquor. It is then steeped in a ley of carbonate of soda, 
 and afterwards well washed and dried, as a preparation for the galling and 
 aluming. The astringent principle has been long known for darkening and 
 fixing common red colours on cotton, by uniting with the earth of alum, 
 and strengthening the basis. To the use of blood in the madder copper 
 I attribute nothing ; as in the rancid and putrid state in which I have seen 
 it used, were it not for the prejudice of the operator, it might be safely 
 dispensed with. 
 
 In proof of the above idea, that it is only the oil uniting with the earth 
 of alum that is of use, I m.ay refer to the mode of dyeing that colour in 
 the East, quoted by Dr. Bancroft, viz. soaking their cotton in oil, (no 
 matter of what description,f) during the night, and exposing it to the 
 sun and air during the day, for seven successive days, rinsing it only in 
 running water, and then immersing it in a decoction of galls and the leaves 
 of sumach previous to aluming. 
 
 I would therefore request the practical dyer, who wishes to arrive at a 
 knowledge of this unaccountable process, to give up the idea of ani- 
 malization, if by it be meant impregnating the cloth with an animal matter, 
 and by the power of the microscope, or any better method, look for the 
 whole truth from some other source than chemical analysis. I am at 
 present inclined to believe that it is a mechanical operation united to a 
 chemical, and that the frequent immersions in the imperfect soap are equi- 
 valent to laying on the first, second, third, &c, coats, preparatory to finish- 
 ing a fine painting in oil. 
 
 * In the French processes given above, the brightening follows the maddering without 
 any immediate oil steep. — Translator, 
 
 t Olive oil, hog's lard melted, oil of sessamum, &c. have all been used with success. 
 
504 
 
 NOTES. 
 
 A very eminent calico manufacturer, whom I consulted on the Turkey 
 red process, assured me, that the only essential mordants are oil and alu- 
 mina : and that bright and fast reds, equal to any produced by the usual 
 complicated process with sheep's dung, galls, and blood, may be obtained 
 without these articles. 
 
 Dyeing Cotton of a Smoke-red (rouge enfume.) 
 
 Smoke-red is a name given to a dull red without lustre, which resem- 
 bles the burned red (rouge hrule) of the India handkerchiefs. To dye this 
 colour, the following method will answer. 
 
 1. Preparations of the Adrianople red, according to the grey course ^ 
 above prescribed, down to the maddering, inclusive. 
 
 2. The cotton, when washed and dried, receives a strong mordant of 
 acetate of alumina ; that is to say, at 6° of the areometer of Baume (8° 
 Tw.) and at a temperature of about 70*^ Fahr. After this it is dried, and 
 then it receives a good washing. 
 
 3. It is passed through a bath of quercitron of greater or less strength. 
 
 4. After being dried and washed, it is brightened in a soda liquor with 
 soap. 
 
 Dyeing Cotton of a Cherry and Rose-red, 
 
 The cherry-red is pretty certainly obtained by following the process 
 which we shall point out. 
 Boiling. 
 
 Bath of sheep's dung. 
 
 Three white baths, each with 6 or 8 pounds of oil. 
 A salt at 2° Baume, (2|° Tw.) 
 A careful degraissage. 
 
 Galling^with a decoction of 5lbs. of nut-galls, to which the infusion of 
 20lbs. of sumach is added. 
 
 Aluming with 36lbs. of very pure alum. 
 Careful washing away of the alum. 
 
 Maddering with the madder of Cyprus or Smyrna, in the proportion of 
 a pound or pound and a half for every pound of cotton. There may, 
 however, be mixed in a third of Provence madder, with two-thirds of the 
 above madders. Brightening, by boiling the cotton for five or six hours 
 in a ley of soda, at l^" Baume (2° Tw.,) in which from 8 to 10 pounds of 
 soap have been dissolved. The cotton is allowed to cool in the bath, 
 and then washed. (The brightening may be also very simply effected, by 
 passing the cotton through a weak solution of chloride of potash or lime.) 
 
 Rosing. The cotton is boiled during half an hour in 150 gallons of 
 water, in which has been dissolved a pound and a half of salt of tin, pour- 
 
NOTEf. 
 
 505 
 
 ing in afterwards a bottle (quart) of sulphuric acid, at 30° Baume. (52^ 
 Tw.) On coming out of the boiler it is washed with care, then boiled 
 anew, for three quarters of an hour, in a solution containing from 15 to 
 16 pounds of white soap. 
 
 For procuring the rose colour, the strength of the brightening is a little 
 increased, and there is employed in rosing somewhat more sulphuric acid 
 at first, than there is white soap in the succeeding bath. 
 
 The brightening in the liquor of Javelle (blacking liquor) suits well 
 here. The rose may also be given, by using oily preparations not so highly 
 charged, less mordant, and consequently less madder, in the dyeing bath. 
 
 A little experience will remove all obstacles. — Vitalis. 
 
 Note KK. p. 347. 
 
 We are indebted to MM. Pelletier and Caventou for a chemical investi- 
 gation of cochineal, in which its colouring matter was skilfully eliminated; 
 Their principal researches were directed to the mesteque cochineal (coccu& 
 cacti), though a few experiments were also made on some other kinds. 
 
 Purified sulphuric ether acquired by digestion with it a golden yellow 
 colour. This infusion left, on evaporation, a fatty matter of the same 
 colour. 
 
 Cochineal, exhausted by ether, was treated with alcohol at 40°. After 
 thirty digestions in the apparatus of M. Chevreul, the cochineal continued 
 to retain colour, although the alcohol had ceased to have any effect on it. 
 The first alcoholic liquors were of a red verging on yellow. On cooling, 
 they let fall a granular matter. By spontaneous evaporation, this matter, 
 of a fine red colour, separated, assuming more of the crystalline appearance. 
 These species of crystals dissolved entirely in water, which they tinged of 
 a yellowish-red. Treated with very strong alcohol in the cold, they re- 
 dissolved, leaving a very animalized brownish matter, to which we shall 
 afterwards return, since we shall find this matter in greater abundance in 
 the watery decoctions of cochineal previously exhausted by ether and 
 alcohol. 
 
 The alcoholic solution of these crystals, thus deprived of its animahzed 
 matter, is still susceptible of affording the above crystalline sediment. In 
 this state, although free from animalized matter, especially when they have 
 been re-dissolved and recovered anew, these crystals do not, however, pre- 
 sent the colouring matter pure, as was at first believed. If this matter be 
 treated with sulphuric ether, one portion is dissolved and colours the ether 
 orange-yellow ; and it is only after the ether has ceased to have any action 
 on the mass, and when it comes off colourless, that thfe substance which 
 will not dissolve in the ether may be regarded as the colouring principle, 
 if not absolutely pure, at least very nearly so. The colouring principle 
 
506 
 
 NOTES. 
 
 of cochineal, insoluble by itself in ether, may, however, be dissolved in 
 small quantity in this liquid, through the intervention of the fat crystal- 
 lizable matter, while the latter becomes less soluble in ether, as it is 
 enveloped and protected by a quantity proportionally greater of the colour- 
 ing principle. These considerations led MM. Pelletier and Caventou to 
 make the following experiment, in the hope of stripping the colouring 
 matter of every particle of the fat substance. They dissolved a certain 
 quantity of their coloured crystals in very strong alcohol, and added a 
 quantity of sulphuric ether equal to that of the alcohol employed. The 
 mixture became turbid, but at the end of some days it had grown perfectly 
 clear. It was of a red colour inclining considerably to yellow. A good 
 deal of the colouring matter had, however, fallen down on the bottom of 
 the vessel, forming an incrustation of a magnificent purple-red. This 
 matter, treated with ether, no longer yielded any principle ; and the pro- 
 perties to be presently detailed lead to the belief, that it may be regarded 
 as the colouring matter of cochineal in a state of purity. By adding 
 new portions of ether to the decanted liquor, a certain quantity of co- 
 louring matter may again be thrown down. The alcoholic tinctures in 
 which the first crystals were formed, were evaporated to dryness on the 
 water-bath ; and the colouring matter obtained, treated by methods analo- 
 gous to the preceding, afforded likewise fat crystallizable matter and co- 
 louring principle. 
 
 Of the Colouring Principle of Cochineal, 
 
 This matter has a very brilliant purple-red colour ; it adheres strongly to 
 the sides of tlie vessels ; it has a granular and somewhat crystalline 
 aspect, very different, however, from those compound crystals alluded to 
 above ; it is not altered by the air, nor does it sensibly attract moisture. 
 Exposed to the action of heat, it melts at about the fiftieth degree Centi- 
 grade (122° Fahr.) At a higher temperature it swells up, and is decom- 
 posed with the production of carburetted hydrogen, much oil, and a small 
 quantity of water, very slightly acidulous. No trace of ammonia was 
 found in these products. 
 
 The colouring principle of cochineal is very soluble in water. By 
 evaporation, the liquid assumes the appearance of syrup, but never yields 
 crystals. It requires of this matter a portion almost imponderable to give 
 a perceptible tinge of bright purplish red to a large body of water. 
 Alcohol dissolves this colouring substance ; but, as we have already stated, 
 the more highly it is rectified, the less of it does, it dissolve. Sulphuric 
 ether does not (^ssolve the colouring principle of cochineal, but weak 
 acids do, possibly owing to their water of dilution. No acid precipitates 
 it in its pure state. This colouring principle, however, appears to be 
 
<9 
 
 NOTES. 
 
 507 
 
 precipitable by all the acids when it is accompanied by the animal matter 
 of the cochineal. 
 
 Acids, however, change the colour of this substance, converting it into 
 a bright red, then a yellowish-red, and lastly, a yellow. When the acids 
 have not been too concentrated, its proper colour may be restored by sa- 
 turation with alkali. Chlorine changes the colour of this principle to 
 yellow, and then destroys it altogether. It produces no precipitate in its 
 solution, unless it contains animal matter. Hence chlorine becomes a 
 useful re-agent for trying the purity of this colouring substance. Iodine 
 acts like chlorine, but more slowly. The alkalies, poured into a solution 
 of the colouring principle of cochineal, change its hue to crimson violet. 
 If the alkali be immediately saturated, the original colour is restored, and 
 the colouring matter may be recovered without any remarkable alteration 
 in its principal properties. If the action of the alkali has been longer 
 continued, or aided by heat, the violet shade disappears, and the colour 
 passes back to red, and then yellow. In this case, the colouring matter is 
 totally altered, for by putting it into contact with those metallic salts which 
 form with it insoluble combinations, we obtain precipitates entirely differ- 
 ent from those which the pure colouring matter produces with the same 
 salts. 
 
 Lime-water produces a violet precipitate with the colouring matter of 
 cochineal. Barytes and strontites do not occasion any precipitate in a 
 solution of the colouring matter ; but they change the hue to violet like 
 alkalies. The affinity of alumina for the colouring matter is very remark- 
 able. When that earth, newly precipitated, is put into a watery solution 
 of the colouring principle, this is immediately seized by the alumina. The 
 water becomes colourless, and a fine red lake is obtained, if we operate at 
 the temperature of the atmosphere ; but if the liquor has been hot, the 
 colour passes to crimson, and the shade becomes more and more violet, 
 according to the elevation of the temperature, and the continuance of the 
 ebullition. 
 
 If, before adding alumina to the watery solution of the colouring prin- 
 ciple, some drops of an acid be poured into this, the lake obtained is at 
 first of a brilliant red ; but the slightest heat changes it to a violet hue. 
 The same effect is produced by putting into the solution of the colouring 
 principle some grains of an aluminous salt. But, on the contrary, if we 
 add to the colouring principle a small quantity of alkali, potash, soda, am- 
 monia, or their subcarbonates, and if we then diffuse through the solution 
 some gelatinous alumina, the liquor rendered violet by the alkalies returns 
 instantly to the red, by the formation of a lake which readily precipitates. 
 In this case, we may keep the mixture boiling for a long time, without 
 making the lake perceptibly violet. This property cannot, however, be 
 
508 
 
 NOTES. 
 
 quite restored by alkaline saturation, especially if the action of the alkali 
 has been some time continued. These facts may serve to explain several 
 phenomena which have been observed in the operations of the scarlet or 
 crimson dye. 
 
 Most salts exercise on the colouring matter of cochineal an action cha- 
 racterized by changes in the hue ; but only a small number are capable of 
 precipitating it, when it is in a state of perfect purity. 
 
 Nitrate of silver has no action on it. The soluble neutral salts of lead 
 change the red colouring matter to violet ; and the acetate of lead deter- 
 mines immediately an abundant precipitate. This precipitate keeps its 
 tint, though there be an excess of acetic acid. By passing a stream of 
 sulphuretted hydrogen gas through the combination, it is decomposed, and 
 the colouring matter is then obtained in a state of purity. Protonitrate of 
 mercury produces a violet precipitate in the solution of the colouring 
 matter ; the deutonitrate precipitates less easily the colouring matter ; 
 what falls is of a scarlet hue. Corrosive sublimate has no action on it. 
 The salts of copper cause no precipitate, but change the colour to violet ; 
 and the salts of iron give a brownish tint, without producing any precipi- 
 tate. The salts of tin exercise on the colouring matter of cochineal a 
 remarkable action. The protomuriate of tin forms a very abundant violet 
 precipitate in the liquid. This precipitate verges on crimson, if the salt 
 contains an excess of acid. The permuriate of tin produces no precipi- 
 tate, but changes the colour to scarlet red. If gelatinous alumina be 
 now added, we obtain a fine red precipitate, which does not pass to crimson 
 by boiling. 
 
 The salts of lime, barytes, and strontian, perfectly neutral, equally 
 change the colouring principle to violet ; but no precipitate can be 
 obtained, except with sulphate of lime. 
 
 The aluminous salts, even slightly acidulous, make the colour pass to 
 crimson, especially with the aid of heat ; none of them produce any 
 precipitation : they even counteract the precipitation of the colouring 
 matter by alumina, of which, in that case, a great excess is required to 
 deprive of colour a liquor tinged with cochineal. Crimson, or even violet 
 lakes, are then obtained. 
 
 The neutral salts of potash, soda, and ammonia, occasion a violet tinge, 
 but no precipitate. The salts, with excess of acid, as the binoxalate and 
 bitartrate of potash, change the colour to scarlet, but still without precipi- 
 tation. 
 
 It appears, therefore, to MM. Pelletier and Caventou, that the metals 
 susceptible of several degrees of oxydizement act like the acids when they 
 are oxydized to a maximum, and like alkalies when they are in the lower 
 stage of oxydizement ; and that this alkaline influence of certain oxydes 
 
NOTES. 
 
 509 
 
 may be exerted in the midst of an acid liquid, when these oxydes are 
 capable of forming with the colouring principle an insoluble compound, 
 while it is totally destroyed by the excess of acid, if the oxyde can pro- 
 duce only soluble combinations* as is the case with soda and potash. 
 
 Tannin and astringent vegetable matters form no precipitates with the 
 colouring principle of cochineal. This pure colouring principle was 
 ignited with deutoxyde of copper, and yielded a gas composed of ninety- 
 eight parts of carbonic acid and two of hydrogen. No appreciable por- 
 tion of azote was obtained. 
 
 To this colouring principle the name Carminium has been given, be- 
 cause it forms the basis of the pigment called carmine. 
 
 The cochineal, after having undergone the action of ether and alcohol ^ 
 was treated in the digester with water, till it ceased to give out colour. 
 There then remained a translucid, gelatinous, brownish matter, of which 
 some portions were whjte, insoluble in cold water, giving up to boiling 
 water merely a portion of their substance, without any trace of colouring 
 principle. The first watery decoctions were much coloured ; the last 
 were colourless. The water acts on cochineal, so as to carry off the last 
 portions of the colouring matter, and the fat substance, and to dissolve a 
 portion of the animal matter, which constitute, as it were, the basis or 
 skeleton of this insect. 
 
 This white or brownish translucent animal matter, when exposed to a 
 moderate heat, dries, takes a horny appearance, and jcan then be kept for 
 a long time ; but when, on the contrary, it is left in the moist state, it is 
 spontaneously decomposed with the diffusion of a nauseous smell. At a 
 higher heat, it furnishes all the products of animal matters, and particu- 
 larly carbonate of ammonia. Boiling water slowly dissolves a little of the 
 animal matter ; and it putrefies with great readiness. It differs from gela- 
 tin, in not being thrown down from water by alcohol, and in being preci- 
 pitable in whiteish flocks by all the acids. 
 
 Chlorine precipitates the animal matter of cochineal, but iodine produces 
 no sensible effect on its solution. Potash and soda communicate to 
 water the power of dissolving this animal matter in abundance. When 
 they are neutralized by acid, the matter is recovered ; but if the acid is 
 in excess, it forms an insoluble compound with an animal matter. All 
 the salts with excess of acid precipitate the animal matter, and are brought 
 to the neutral state. Thus the precipitate seems formed of the animal 
 matter and of the acid that is in excess. But several of the neutral salts 
 are decomposed by the animal matter, and precipitates are obtained con- 
 taining it, the metallic oxyde and the acid. In this way, the salts of lead, 
 copper, and tin, act. The nitrate of silver also possesses this property ; 
 and since this salt does not precipitate the colouring matter of cochineal, 
 
510 
 
 NOTES. 
 
 while it is very sensible in regard to the animal matter, it forms a good 
 re-agent of the purity of carminium. 
 
 The fat matter obtained by the evaporation of the ethereous tinctures 
 is of an orange-yellow colour. The first tinctures afforded a fat matter 
 more coloured and reddish, proceeding from a certain quantity of car- 
 minium, which the fat matter had taken up. This fat matter has the 
 smell of decoctions of cochineal. By dissolving it in hot absolute alco- 
 hol, there was obtained, on cooling, a large quantity of a pearly crystalline 
 matter, of a rose-white colour, sprinkled with red points. By repeated 
 solutions and crystallizations, it was rendered colourless ; nor did it retain 
 either taste or smell. Insoluble in water and cold alcohol, it dissolved in 
 ether, fused at a heat of 40'' Cent. (104'' Fahr.) and formed with alkalies 
 well characterized soaps. This substance is therefore a fat, translucent, 
 crystallizable, similar to what M. Chevreul has found in the fats of mam- 
 miferae, and which he has called stearine. In cochineal, a little elaine is 
 associated with it, which is obtained by evaporating off the alcohol. 
 
 The pretended yellow colouring matter of cochineal, of which mention 
 is made in some books, does liot exist. Fat matter, loaded with car- 
 minium, has been mistaken for it ; for carminium affords yellow solutions, 
 when it contains a fat matter in a pretty large proportion. Carminium 
 even possesses the property of rendering the fat matter soluble in water. 
 In fact, if we treat cochineal with boiling alcohol, without having exposed 
 it previously to ether, we obtain a kind of crystals similar to what are 
 mentioned in the beginning of this memoir, but much more loaded with 
 fat matter. These crystals do not readily dissolve in water, and the solu- 
 tion is of an orange yellow approaching to red. When treated by the 
 methods above pointed out, they are found to be composed of carminium 
 and fat matter in a very large proportion ; and though entirely soluble in 
 water, they retain still a little animal matter. 
 
 By incinerating cochineal, certain salts were found in the residue. 
 Hence the general products are as follows : — 
 
 1. Carminium. 2. A peculiar animal matter. 3. A fat matter, containing 
 stearine, elaine, and odorant principle, 4. Salts, phosphate of lime, carbon- 
 ate of lime, muriate of potash, phosphate of potash, potash united to an 
 organic acid. 
 
 Second Part. — Of Cochineal in reference to its employment in the Arts, 
 
 All the acids form precipitates in the watery decoction of cochineal, but 
 these precipitates are stronger in proportion to the abundance of the ani- 
 mal matter ; hence they do not appear, or only after a certain time, when 
 the boiling is slight, or the decoction too much diluted. The precipitates 
 are generally of a pretty fine colour; but the shade varies according to 
 
NOTES. 
 
 511 
 
 the acid employed, and its quantity. The acidulous salts, such as the 
 bitartrate and bioxalate of potash, also produce precipitates in the decoc- 
 tion of cochineal. The alkalies change the colour to crimson without 
 causing any precipitate ; they even redissolve the precipitates occasioned 
 by the acids. 
 
 If we add to water in which cochineal is to be boiled a certain quantity 
 of alkali, there is then dissolved a much larger quantity of the animal 
 matter ; and when we thereafter add some acid, a much more abundant 
 precipitate takes place. These precipitates are commonly of a beautiful 
 red. By drying they take so deep a colour as to appear brown ; but on 
 diffusion through water, they recover their brightness. The alkali appears 
 to act in the decoction, not only as a solvent of the animal matter, but 
 likewise by modifying the colouring matter. These precipitates are per- 
 fectly pure carmines. The neutral alkaline salts, and most of the metal- 
 lic, act on this decoction as on the solution of carmine. 
 
 It has been remarked, that the decoction of cochineal can be kept a 
 long time without alteration. It is known that carminium cannot pass 
 into a putrid fermentation, but the animal matter is very easily decom- * 
 posed. This, however, in the decoction of cochineal, seems to be preserved 
 from change by its union with the colouring matter. 
 
 On Carmine and Carminated Lakes, 
 
 The process followed in Germany for making carmine, which consists in 
 pouring a certain quantity of solution of alum into a decoction of cochineal, 
 is the most simple of all, and affords an explanation of the formation of 
 carmine, which is merely the carminium and the animal matter precipitated 
 by the excess of acid in the salt, which has taken down with it a small 
 quantity of alumina ; but it appears that alumina ought not to be regarded 
 as essential to the formation of carmine. In fact, by another process, called 
 by the name of Madame Cenette, of Amsterdam, the carmine is thrown 
 down by pouring into the decoction of cochineal a certain quantity of 
 binoxalate of potash. When carbonate of soda is added, then carminated 
 lake also falls down. That carmine is a triple compound of animal mat- 
 ter, carminium, and an acid, appears from the circumstance that liquors 
 which have afforded their carmine, when a somewhat strong acid is poured 
 into them, yield a new formation of carmine by the precipitation of the 
 last portions of the animal matter. But whenever the whole animal mat- 
 ter is thrown down, the decoctions, although still much charged with the 
 colouring principle, can afford no more carmine. Such decoctions may be 
 usefully employed to make carminated lakes, saturating the acid with a 
 slight excess of alkali, and adding gelatinous alumina. The precipitates 
 obtained on adding acids to the alkaline decoctions of cochineal, are there- 
 
512 
 
 NOTES. 
 
 fore true carmines, since they do not contain alumina ; but the small 
 quantity of alumina which is thrown down by alum in the manufacture of 
 carmine, augments its bulk and weight. It gives besides a greater lustre 
 to the colour, even from diluting and weakening it a little. 
 
 The carmines found in the shops of Paris were analyzed, and yielded 
 the same products. They decomposed by the action of heat, with the 
 diffusion at first of a very strong smell of burning animal matter, and then 
 of sulphur. A white powder remained, amounting to about one-tenth of 
 the matter employed, and which was found to be alumina. Other quanti- 
 ties of carmine were treated with a solution of caustic potash, which com- 
 pletely dissolved them, with the exception of a beautiful red powder, not 
 acted on by potash and concentrated acids, and which Vx^as recognized to 
 be red sulphuret of mercury, or vermilion. This matter, evidently foreign to 
 the carmine, appears to have been added, in order to increase its weight. 
 
 The preceding observations and experiments seem calculated to throw 
 some light on the art of dyeing scarlet and crimson. The former is 
 effected by employing a cochineal bath, to which there have been added 
 in determinate proportions, bi tartrate of potash and permuriate of tin. 
 The effect of these two salts is now well known. The former, in conse- 
 quence of its excess of acid, tends to redden the colour, and to precipitate 
 it along with the animal matter : the latter acts in the same manner, at 
 first by its excess of acid, then by the oxyde of tin which falls down also 
 with the carmine and animal matter, and is fixed on the wool, with which 
 it has of itself a strong tendency to combine, MM. Pelletier and Caven- 
 tou remark, that *' to obtain a beautiful shade, the muriate of tin ought to 
 be entirely at the maximum of oxydizement ; and it is in reality in 
 this state that it must exist in the solution of tin prepared according to 
 the proportions prescribed in M. Berthollet's treatise on dyeing." 
 
 We hence see why, in dyeing scarlet, the employment of alum is care- 
 fully avoided, as this salt tends to convert the shade to crimson. The 
 presence of an alkali would seem less to be feared. The alkali would 
 occasion, no doubt, a crimson-coloured bath ; but it would be easy in this 
 case to restore the colour by using a larger quantity of tartar. We should, 
 therefore, procure the advantage of having a bath better charged with 
 colouring matter and animal substance. It is for experience on the large 
 scale to determine this point. As to the earthy salts, they must be care- 
 fully avoided ; and if the waters be selenitish, it would be a reason for 
 adding a little alkali. 
 
 To obtain crimson, it is sufficient, as we know, to add alum to the cochi- 
 neal bath, or to boil the scarlet cloth in alum water. It is also proper to 
 diminish the dose of the salt of tin, since it is found to counteract the 
 action of the alum. 
 
NOTES. 
 
 513 
 
 The alkalies ought to be rejected as a means of changing scailet to 
 crimson. In fact, crimsons prepared by this process cannot be peimanent 
 colours, as they pass into reds by the action of acids. 
 
 Note LL. p. 347. 
 
 According to M. Von Grotthuss, carmine may be deprived of its golden 
 shade by ammonia, and subsequent treatment with acetic acid and alcohol. 
 Since this fact was made known, M. Herschell, colour-maker, at Halle, has 
 prepared a most beautiful carmine. 
 
 Note MM. p. 861, 
 Chemical examination of Kermes (cocus illicis) by J. L. Lassaigne. 
 
 On applying to these insects the processes employed by MM. Pelletier 
 and Caventou in the analysis of cochineal, M. Lassaigne obtained anal- 
 ogous results. 
 
 Kermes, treated with boiling sulphuric ether, yielded a yellow fat matter, 
 which may be obtained in an insulated state by evaporation of the solvent ; 
 and a little of its red colouring matter may be carried .off by digesting it in 
 cold alcohol of 30'' Baume (sp. gr. 868.) This fat substance is inodorous, 
 of a slightly styptic taste, without action on litmus infusion, fusible at 45° 
 Cent. (113^ Fahr.,) and easily saponified by alkalies. 
 
 Kermes, exhausted by ether, yields to alcohol, by means of heat, a 
 colouring matter and a brown animal matter. On cooling, the latter is 
 precipitated in reddish flocks, mingled with the colouring matter carried off 
 by the alcohol. The alcoholic solutions, when evaporated in a glass 
 retort, leave the colouring matter of kermes ; but to procure it perfectly 
 pure, it must be several times redissolved in alcohol. 
 
 This matter has a very deep purple red colour. It has a granular aspect 
 and crystalline fracture. The air has no action on it. Its powder pos- 
 sesses a beautiful vermilion hue. 
 
 Sulphuric ether does not affect its solution ; but water and alcohol dis- 
 solve it in any proportion. The more concentrated the latter is, however, 
 the less is its solvent faculty. Reagents affect this matter like carminium, 
 to which it bears a close resemblance. 
 
 Kermes, after having been treated successively by ether and alcohol, 
 remains a little coloured. On boiling it with water, the last portions of 
 colouring matter may be removed, and there remains a brownish animal 
 matter, in semitransparent scales, very slightly soluble in water, and pos- 
 sessing all the properties of the animal matter of the cochineal. 
 
 It hence appears, that kermes has -a chemical composition, very analogous 
 to that of cochineal. — Annates de cliimie et physique, xii, 102, 
 
 2 L 
 
514 
 
 NOTES. 
 
 Note NN. p. 364. 
 
 Seed-lac is obtained in the following mannerc When the lac has been 
 separated from the stems (sticks) to which it naturally adheres, and is 
 reduced to a coarse powder, the silk and cotton dyers extract its colours 
 as much as they can by means of water ; and to the hard and yellowish 
 resinous powder which remains, and which resembles in some measure 
 mustard-seed, the name of seed-lac is given. 
 
 Shell-lac is procured by melting seed-lac in a cotton bag, above a glow- 
 ing charcoal fire : when the lac is melted, it is forced through the bag by 
 twisting it, and is received on the smooth trunk of a tree. The resin 
 being the most fusible portion of the lac, passes through the bag in a 
 state of great purity. 
 
 The lac-lake contains, besides the colouring matter of the lac, about a 
 third of its weight of resin, a sixth of alumina, and much earthy matter. 
 
 Mr. Bancroft has given a full account of the mode of preparing lac-lake. 
 Lac-lake is prepared in India, from stick -lac reduced to powder, by re- 
 peated affusions of boiling water containing a large quantity of soda ; but 
 this addition of soda, although it disposes the water to extract the colour- 
 ing portion of the lac much more copiously, occasions a considerable solu- 
 tion of resin, which is afterwards precipitated, intimately combined with 
 the colouring principle, by the alum employed in its precipitation. Hence 
 the lac-lake, besides its colouring matter, contains, as previously stated, 
 different proportions of resin and alumina. The proportion of resin may 
 be estimated at one-third of its weight, and that of alumina at one-sixth. 
 It contains, likewise, a portion of vegetable matter derived from the muci- 
 laginous bark of an Indian tree called /ocfw, which is supposed to be useful 
 in several respects. But this point has not been hitherto decided. Con- 
 siderable but variable proportions of sand, and other earthy matters, are 
 usually added to the lac-lake by the manufacturers to increase its weight. 
 
 The lac- lake, after being ground to a fine powder in proper mills, is 
 put into wooden troughs with water, where it settles, and the colourless 
 supernatant liquor is drawn off. The sediment or moistened powder must 
 then be put into a leaden cistern, where it is diffused through dilute sul- 
 phuric acid, whereby a limpid solution of the colouring matter is obtained. 
 Thus it is separated from the foreign substances, resinous or earthy, and ren- 
 dered capable of application to stuffs. Sulphuric acid possesses the property of 
 destroying the bad effects of the resin much better than the muriatic. 
 
 For dissolving the colouring matter in this way, three pounds of oil of 
 vitriol, specific gravity 1.845, (169° Tw.) are required for every four 
 pounds of the dry lac-lake before it was milled. The ground and moist 
 lac-lake should not contain more than twice its weight of water. The 
 sulphuric acid is in that case added, and perfectly mixed with the moist 
 
NOTES. 
 
 powder, stirring up and agitating with a strong rod or ladle of glass or 
 lead. But if the lac-lake has been ground without being moistened, it 
 will be proper, before adding the acid, to dilute this with twice its weight 
 of water. When the preceding mixture is made, it must be left in repose 
 for twenty-four hours in summer, and forty-eight in winter. Then a gallon 
 of boiling water must be added for every pound of lac-lake (weighed dry,) 
 and the whole must be well mixed. After leaving the mixture at rest 
 for twenty-four hours, the limpid coloured solution ought to be drawn off 
 into another leaden vessel, and the same quantity of boiling water poured 
 upon the residuum. This mixture, after being well stirred, is to be left 
 at rest for twelve hours as before, and then the clear liquor may be drawn 
 off. The same quantity of boiling water may be again thrown on the 
 residuum, which after repose is to be separated. This treatment is to be 
 repeated as long as boiling water acquires colour. When this ceases, a 
 little of the residuum is to be mixed with one-half its weight of carbonate 
 of soda dissolved in a little water, and if the whole colouring matter has 
 not been extracted, it will become red, and will deepen in colour. If 
 after this trial there should seem to remain a quantity of colour worthy 
 the trouble of extraction, the residuum should be mixed with from one- 
 sixth to one-fourth of the quantity of sulphuric acid primitively employed, 
 and after leaving the mixture at rest for twelve hours, boiling water is to 
 be poured on it as above directed. This operation may be resumed till 
 the whole of the colouring matter has been extracted. 
 
 The coloured liquid being now all collected in the same vessel, there 
 must be very exactly mixed into it two pounds of pure lime, well calcined 
 and reduced to a fine powder, for every five pounds of sulphuric acid 
 contained in the liquor. This quantity of lime will be sufficient to neu- 
 tralize four-fifths of the acid, and to carry it down (in the form of sulphate 
 of lime) without any colouring matter. The supernatant liquid is then to 
 be decanted, and the remaining fifth of acid which it contains disposes 
 the colouring matter contained in the liquor better to penetrate and im- 
 pregnate the stuff. This liquor or solution of lac colour, may be called 
 No. 1. This may be employed without any difficulty in ^dyeing, as if it 
 were a weak decoction of cochineal, along with the mordants and other 
 acids to be presently described. We shall merely observe at present 
 that two-thirds of the sulphuric acid prescribed for the lac-lake will be 
 sufficient for extracting the colour of the lac-dye ; but although neither 
 the labour nor the expense of extracting the colouring matter of either of 
 these substances be considerable, it is probable that the greater number 
 of dyers will deem it sufficient to subject the lac-lake or the lac-dye to 
 the action of sulphuric acid, so as to deprive the resinous portions of their 
 adhesive property ; in this case, the colouring matter becomes soluble in 
 the dyeing liquor, and may be applied to the stuff, without any previous 
 
 2 L 2 
 
516 
 
 NOTES. 
 
 separation of the resinous and other matters soluble in these preparations. 
 For this purpose, one pound of sulphuric acid at most, should be employed 
 for every two pounds of lac-lake weighed in its dry condition ; two-thirds 
 of a pound will be sufficient for two pounds of the lac-dye. Each of these 
 substances being moistened and milled, as we have already explained, 
 ought to be mixed in a leaden vessel with the determinate proportion of 
 sulphuric acid. After having stirred them well at different times, the 
 mixture must be left at rest for at least twenty-four hours in summer, and 
 thrice this time in winter. After this, it will be proper to employ it 
 immediately in the manner to be presently pointed out. The cost of the 
 preparation may be estimated at 20 per cent, independent of the expense of 
 grinding. This preparation of lac-lake or the lac dye, may be called No. 2. 
 
 From two to three pounds of lac-lake, according to the quality, and 
 perhaps a little less of the lac dye, can produce the effect of a pound of 
 cochineal ; but to give the greatest vivacity to the colour, a sixth or an 
 eighth of nitromuriate or other solution of tin, must be used in the dyeing 
 more than is employed with cochineal, because the alumina, by which the 
 colour of the lac was at first precipitated, and of which a portion has been 
 redissolved and retained by the sulphuric acid, and in the operation just 
 described, would give to the colour a crimson tint, unless the oxyde of 
 tin be employed in such quantity as to repel, by its superior attraction, 
 (affinity), the alumina, and prevent it from becoming attached to the stuff 
 and to the colouring matter. 
 
 It is admitted that the colour extracted from the lac resists the action 
 of acids much better than cochineal. Besides this advantage, the scarlet 
 colour may be obtained better and cheaper with this substance at a single 
 operation. For this purpose, we must put into a vessel of block tin a 
 sufficient quantity of clear soft water, to which we add one pound of 
 tartar, or, which is better, powdered cream of tartar, for every ten pounds 
 of stuff, with as much either of quercitron bark in powder, contained in a 
 bag, or otherwise fustet (^rJius cotinus) in chips, also enclosed in a bag. 
 These ingredients will produce abundance of the yellow colour. Having 
 raised this composition to the boiling point, we must add nitro-muriate of 
 tin, or any other solution of this metal, with a suitable quantity of the 
 colour of lac-lake No. 1. or of that of No. 2. This mixture being 
 thoroughly made, the stuff, previously cleaned and moistened, is to be 
 thrown into the bath, and turned through it by a wanch, as is usually 
 practised, till it has acquired sufficient body and brilliancy of colour. 
 This commonly takes place in an hour, if the liquor be kept constantly 
 boiling. To prevent any chance of imperfection in the dye, a little more 
 lac colour should be used for each operation, since the superfluity will 
 serve, wUhout any loss, for the other pieces of stuff which are to be dyed 
 in the sequel. 
 
NOTES. 
 
 517 
 
 If it be judged proper to neutralize a portion of the sulphuric acid 
 employed in preparing No. 2, to prevent the harshness which the acids 
 are supposed to give to goods, this may be done by the addition from time 
 to time of carbonate of soda, not exceeding a pound, or a pound and a 
 half, for every pound of sulphuric acid that was employed. 
 
 If one-fourth part of the solution No. 1, or of the preparation No. 2, 
 be kept out, and there be added, towards the end of the process, a quarter 
 of an ounce of cochineal for every pound of stuff to be dyed, we shall 
 obtain a colour equal in vivacity and beauty to scarlet dyed entirely with 
 cochineal. 
 
 When a stuff is dyed with the lac-lake on purpose to change its shade 
 afterwards to a bright rose, to a crimson or purple, neither quercitron nor 
 fustet should be used, nor more than half the quantity of tartar. The 
 stuff dyed without these ingredients is to be thereafter washed, and put 
 into a clean vessel, along with warm water, containing a moderate portion 
 of carbonate of soda in solution of ammonia. If a more decided purple 
 be wanted, we must add a little archil to the bath, or alkaline liquor, and 
 then proceed as usual. But as the colour of archil is not sufficiently 
 permanent, dyes partaking more or less of the purple, moderately beau- 
 tiful and fast, may be obtained directly, by adding to the bath composed 
 of No. 1. or No. 2, a suitable proportion of a decoction of logwood. This 
 addition need not, however, be made before the end of the operation , 
 and when logwood is to be used, neither fustet nor quercitron are needed ; 
 but as tartar renders the colour of logwood more durable, it becomes 
 necessary, and the solution of tin is indispensable. We must, however, 
 beware of turning the stuff with the winch in the bath, before the logwood 
 be added, and thoroughly mixed with the liquor. 
 
 If a stuff be dyed with one of the preparations No. 1 or No 2 ; if pul- 
 verized quicklime in sufficient quantity to neutralize the acid be added to 
 the bath ; and if the boiling be Jiept up for a quarter of an hour, a good 
 crimson may be obtained without any solution of tin, or other ingredients, 
 that are required for scarlet. In this case, the alumina re-dissolved by the 
 sulphuric acid, and the sulphate of lime, serve for mordants. 
 
 Mr. Hatchett, in his admirable memoir on lac, published in the Philoso- 
 phical Transactions for 1804, states the composition of stick-lac to be. 
 Colouring extract ..... 20 
 Resin , , . , , . . \3G 
 Vegetable gluten . . , . . 11 
 Wax, with a little colouring extract , . 12 
 Extraneous substances . . . . 13 
 
 192 
 
 Loss . 8 
 
 200 
 
518 
 
 NOTES. 
 
 200 grains of seed-lac yielded him only , 
 500 „ shell-lac 
 
 5 of colouring matter. 
 2,5 ff 
 454.5 resin. 
 
 Mr. Hatchett in that memoir states, that the colouring extract of lac is 
 insoluble in ether, scarcely soluble in alcohol, and slightly so in water, 
 but readily in sulphuric acid, forming a deep brownish-red solution, which 
 being diluted with water, and saturated with potash, soda, or ammonia, 
 becomes changed to a deep reddish purple. Strong acetic acid dissolves 
 it with great ease, and forms a deep brownish-red solution. The lixivia of 
 potash, soda, and ammonia, act powerfully on this substance, and almost 
 immediately form perfect solutions, of a beautiful deep purple colour. 
 Pure alumina put into the aqueous solution does not immediately produce 
 any effect ; but upon the addition of a few drops of muriatic acid, the 
 colouring matter speedily combines with the alumina, and a beautiful lake 
 is formed. Mr. Bancroft states, that muriatic acid does not answer so well 
 as sulphuric, in preparing the lac dye. 
 
 Muriate of tin, says Mr. Hatchett, produces a fine crimson precipitate, 
 when added to the aqueous solution. A similar coloured precipitate is 
 also formed by the addition of solution of isinglass. Probably the tannin 
 thus indicated was afforded by the small portions of vegetable bodies, from 
 which the stick-lac can seldom be completely separated. 
 
 Twenty grains of borax, dissolved in 4 ounces of water, form a liquid . 
 capable of dissolving 100 grains of shell-lac. This solution of lac in water, 
 mixed with various colours, as vermilion, fine lake, indigo, prussian blue, 
 sap-green, or gamboge, forms an excellent vehicle for their application to 
 paper, since, when it dries, the colour cannot be removed with a moistened 
 sponge. The Indians make an ink by mixing the above vehicle with 
 lamp-black. 
 
 M. P. A. de Bonsdorff has pointed out several new applications of brazil 
 wood as a chemical re-agent. It may enable us to distinguish one acid 
 from another. Sulphuric acid concentrated, or diluted with three parts of 
 water, instantly gives to paper stained with brazil wood a bright rose co- 
 lour, which, attracting humidity from the air, gradually passes to orange. 
 More dilute it gives a dirty yellow. Nitric and muriatic acids act like the 
 sulphuric. Sulphurous acid gas blanches the colour. Concentrated dydriodic 
 acid yields a rose colour, which becomes first yellow on the edges, and 
 finally throughout. Diluted acid gives a fading yellow. Fluoric acid, or 
 fiuosilicic, causes a clear red colour. Diluted, it instantly produces a fine 
 lemon-yellow colour, which in the space of a minute disappears, and soon 
 leaves a tint of greenish-grey, which, observed by transmitted light, is of 
 an olive-green. When exposed to the gaseous acid, the paper passes 
 
 Note 00. p. 379. 
 
NOTES. 
 
 519 
 
 through these transitions of colour, a phenomenon whicli does not occur 
 with the other acid vapours. Fluboric acid has the same habitudes. Bo- 
 raic acid does not act at first, but by and by the colour of the paper be- 
 comes pale, and ends in a white, bordering a very little on red. If boracic 
 contain traces of the sulphuric, a marked yellowish colour is formed, which 
 soon disappears. Concentrated phosphoric acid gives a rose colour, which, 
 in the air, slowly changes to orange. Dilute, it yields a permanent yellow. 
 Hypophosphorous gives a red, which passes through yellow to white. Con- 
 centrated arsenic acid produces a pretty durable rose colour ; diluted, a 
 fugitive yellow. Arsenious acid has no sensible effect. Concentrated acetic 
 acid gives instantly a sombre yellowish colour, which immediately disap- 
 pears, and is succeeded by a pale violet colour, which, viewed by trans- 
 mitted light, is a very deep violet-red ; diluted, a yellowish colour, 
 becoming violet-red. When this acid is mixed with the sulphuric, a yellow- 
 ish colour appears, instead of violet red. Acetic acid, containing no more 
 than ^io part of sulphuric, affords a very perceptible yellowish colour. Citric 
 acid, a beautiful permanent yellow. Tartaric and malic acids, a yellow 
 becoming dirty. Concentrated oxalic acid, an orange colour, becoming 
 slowly yellow ; diluted, a durable yellow. 
 
 Woollen cloth, plunged into a boiling bath of brazil wood, then drained, 
 and dipped for some minutes in a dilute phosphoric or citric acid, or what 
 is cheaper and equally good, in a dilute bisulphate of lime, takes a very 
 lively yellow dye, which resists washing with soap. Silk may be dyed by 
 the same process, but cotton or linen cannot. 
 
 The bright fugitive red, called fancy-red, is given to cotton by Nicara- 
 gua, or peach wood, a cheap kind of brazil wood. 
 
 The cotton being scoured and bleached, is boiled with sumach. It is 
 then impregnated with a solution of tin (at 5° Baume, 6f° Tw., according 
 to Vitalis.) It should now be washed slightly in a weak bath of the 
 dyeing wood, and lastly worked in a somewhat stale infusion of the peach 
 or brazil wood. When the temperature of this is lukewarm, the dye is said 
 to take better. Sometimes two successive immersions in the bath are given. 
 It is now wrung out, aired, washed in water, and dried. 
 
 M. Vitalis says, that his solution of tin is prepared with two ounces of 
 tin, and a pound of aqua regia made with two parts of nitric acid at 24° 
 Baume, (40° Tw.) and three parts of muriatic acid at 22° (36° Tw.) 
 
 For a rose colour, the cotton is alumed as usual, and washed from the 
 alum. It then gets the tin mordant, and is again washed. It is now 
 turned through the dye-bath — an operation which is repeated if necessary. 
 
 ¥ ox purple, a little alum is added to the brazil bath. 
 
 For amaranth, the cotton is strongly galled, dried, and washed. 2. It 
 is passed through acetate of iron, till it has taken a strong grey .shade. 
 
520 
 
 NOTES. 
 
 3. it receives a bath of lime-wate. 4. Mordant of tin. 5. Dyeing in the 
 brazil wood bath. C. The two last operations are repeated. 
 
 The following example of a spirit red, directly applied in calico printing, 
 is given in Rees* Cyclopaedia, article Colour : — 
 
 Prepare an aqua regia, by dissolving two ounces of sal ammoniac in one 
 pound of nitrous acid, sp. gravity 1. 25. (25° Tw.) To this add two ounces 
 of fine grain tin ; decant it carefully off the sediment, and dilute it with 
 one-fourth its weight of pure or distilled water. 
 
 To one gallon of water add one pound of cochineal, ground as fine as 
 flour ; boil half an hour ; then add two ounces of finely pulverized gum 
 dragon {tragacanth^ and two ounces of cream of tartar, and stir the whole 
 till it is dissolved. When the liquor is cool, add one measure of the pre- 
 ceding solution of tin to two of the cochineal liquor, and incorporate well 
 by stirring. Apply this with the pencil or block ; suffer it to remain on 
 the cloth six or eight hours ; then rinse off in spring water. This colour 
 will be a bright and beautiful scarlet. 
 
 2. Boil twelve pounds of brazil chips during an hour, in as much 
 water as will cover them. Draw off the decoction, pour on fresh water, 
 and boil as before. Add the two liquors together, and evaporate slowly 
 down to one gallon. To the decoction, while warm, add four ounces of 
 sal ammoniac, and as much gum dragon, or Senegal, as will thicken it 
 for the work required. When cool, add one of the solution of tin above 
 described to four, six, or eight of the brazil liquor, according to the colour 
 wanted. Suffer it to remain for eighteen or twenty hours on the cloth ; then 
 rinse off in spring water as before. The colour will be a pale and de- 
 licate pink. If it be required deeper, the decoction must be made stronger, 
 and used in the proportion of three or four to one of the solution of tin. 
 Nicaragua or peach wood, though not so rich in colouring matter as brazil, 
 yields a colour, however, which is, if possible, more delicate and beautiful. 
 
 Note PP. p. 384. 
 
 Dr. Dingler, manufacturing chemist at Augsburg, gives the following 
 prescription for dyeing with brazil woods of inferior qualities, and clearing 
 these dyes of their tawny pigment. The watery infusions of these poorer 
 dyewoods are to be evaporated till from four parts of wood by weight there 
 remain only 12 or 15 of liquid. When this liquid has cooled, we must 
 pour into it, after twelve or eighteen hours, two parts of skimmed milk. 
 After stirring this mixtures well, we boil it for a few minutes ; then pass it 
 through a thick piece of flannel. The tawny colour will be then seen to at- 
 tach itself to the caseous part of the milk, which spontaneously precipitates 
 from this decoction, without occasioning the least loss in the quantity of 
 red colour. The remaining red is of a pure tint. Perhaps this process 
 
NOTES. 
 
 521 
 
 might be useful with madders, which are supposed to consist of the same 
 two colours. Two pounds of milk are sufficient for six or eight pounds of 
 young woods. 
 
 Note QQ. p. 387, 
 
 The colouring principle of logwood was discovered by M. Chevreul, 
 and called Hematin. 
 
 Ground logwood is to be digested in water at a temperature of from 
 120° to 130° Fahr. After a few hours the liquor is filtered and eva- 
 porated to dryness. The residuum is put into alcohol of 36° Baume, 
 (sp. gr. 837) for a day. After this he filters the new liquor, concen- 
 trates it till it thickens, pours into it a little water, exposes it anew to 
 a gentle evaporation, and then leaves it to itself. By this means he ob- 
 tains a pretty large quantity of crystals of hematin, which, to be rendered 
 pure, need only be washed in alcohol and dried. 
 
 This substance is crystalline of a rosy-white, very brilliant when viewed 
 through a lens, having a taste slightly astringent, bitter, and acrid. 
 
 Exposed to the action of fire in a retort, hematin affords all the pro- 
 ducts of animal substances, and, besides, a small quantity of ammonia, 
 which proves that it contains azote. 
 
 Boiling water dissolves it easily, taking an orange-red colour, which 
 passes to yellow by cooling, but which may be restored by heating the 
 solution anew. When this is evaporated, crystals of hematin are formed. 
 On adding to it some acid very gradually, it changes to yellow and then 
 to red. Sulphurous acid yellows and then blanches the colour. 
 
 Potash and ammonia cause the solution of hematin to take a purple 
 red ; if a great excess of these alkalies be added, the colour becomes 
 violet-blue, then brown-red, and finally yellow-brown. The hematin is now 
 decomposed ; it cannot be recovered by acids. 
 
 If a current of sulphuretted hydrogen gas be passed through water 
 charged with hematin it takes a yellow colour, which vanishes after a few 
 days. The sulphuretted hydrogen appears to act by combining with the 
 hematin, and not by deoxydizing it. This is easily verified by putting into 
 a small jar, filled with mercury, a certain quantity of the blanched solution, 
 and then introducing a bit of pure potash. This melts, combines with 
 the sulphuretted hydrogen, and the colour of the hematin immediately 
 reappears. 
 
 Protoxide of lead, protoxyde of tin, hydrate of tritoxyde of iron, hydrate 
 of copper, hydrate of nickel, oxyde of zinc and its hydrate, flowers of anti- 
 mony, oxyde of bismuth, combine with hematin, and give it a blue colour, 
 with a loss of the violet shade. The deutoxyde of tin acts on it in the 
 manner of the mineral acids. 
 
 Hematin precipitates glue from its solution, under the form of reddish 
 flocks. 
 
522 NOTES. 
 
 M. Chevreul proposes it as a good re-agent for acids. — Annales de 
 Chimie, vol. Ixxxi. p. 128. 
 
 Note RR. p. 402. 
 
 Dr. John, of Berlin, gives the following as the results of his examination 
 of annotto. The grains of Rocou contain an aroma, an acid, resin com- 
 bined with the colouring matter, vegetable mucilage, fibrin, coloured 
 extractive, and a peculiar matter which approaches to mucilage and 
 extractive. This analysis explains the reason why an alkali is added to 
 annotto when it is employed in dyeing. The alkali combines with he 
 resin, and forms a soap which dissolves in water. The alkali acts likewise 
 on the colouring matter, and renders it more lively. 
 
 Note SS. p. 408. 
 
 The application to stuffs of colours derived from the mineral kingdom, 
 is one of the most marked improvements in modern dyeing. Mr. Ray- 
 mond received from the French government, in 1811, 8000 francs, as a 
 reward for communicating to the public his process for dyeing silk of a 
 uniform, fast, and bright prussian blue colour. 
 
 By a gentle calcination till sulphurous acid fumes begin to appear, he 
 first converts copperas into the red sulphate of iron. This he dissolves in six- 
 teen times its weight of warm water, and filters, when he has a clear solu- 
 tion of a lively yellow colour, bordering on red. The silk, prepared as for 
 the indigo dye, is to be put into the solution of iron, and left there a 
 shorter or longer time, according to the shade of blue that is wanted. It 
 is then taken out of the vat, and wrung very dry over a pole placed over 
 the vat. The silk is next carried to the stream, to be thoroughly cleansed, 
 which is effected by twice beetling it, and plunging and agitating it each 
 time in the running water. The water now wrung out of the silk should 
 not be able to affect solution of ferroprussiate of potash. An ounce of 
 green copperas will furnish red sulphate sufficient for a pound of water. 
 Dissolve in pure water, heated to G0° Reaumur, (167° Fahr.,) and put into 
 a deal vat, or tub, one ounce of ferroprussiate of potash for every twelve 
 ounces of silk to be dyed. When the prussiate is entirely dissolved, add 
 one ounce, or even rather more, of muriatic acid, at about 21°Baume, 
 (34° Tw.,) stirring the mixture well. When the liquor has acquired a 
 greenish colour, the silk must be immediately plunged in it, and stirred 
 about for some minutes, after it has been well wrung and disposed upon 
 poles, in the same manner as for the iron mordant. 
 
 The silk having received in an equal manner the dye of prussian blue, it 
 is taken out of the prussiate vat, and after being well wrung on a pole 
 above the vat, it is taken to the river, where it must receive two or three 
 beetlings, and must be plunged and agitated each time in the water, (in 
 
NOTES. 
 
 523 
 
 the same manner as for dyeing black,) in order to free it entirely from 
 any portion of prussiate of iron that is not truly combined in it, and 
 which, by remaining partly interposed in the silk, would cause it to dye 
 the water blue, and also to produce stains of blue on any white body on 
 which it is rubbed. 50"" Reaumur (144"* Fahr.) is the most suitable tem- 
 perature for the prussiate bath. Should the bath of prussiate of potash 
 become of a blue colour, when the silk is dipped into it, it is an indication 
 that it contains either too much prussiate or muriatic acid, or that the silk, 
 after passing through the mordant of oxyde of iron, had not been suffi- 
 ciently cleansed in the river. 
 
 Lastly, the silk being well washed in the stream, and thoroughly wrung 
 with the hands, is to be placed loosely on the poles, as in the preceding 
 operations ; after which it must be well stirred and agitated in a large ves- 
 sel, three-fourths filled with cold water, and to which must be added, for a 
 hundred pounds of silk, two pounds of ammonia, (water of,) marking 
 21° of Baume's spirit hydrometer (sp. gr. 92'2.) The blue colour will im- 
 mediately become at least three shades deeper, taking a much richer and 
 brighter tint, at the same time fixing more perfectly in the silk. This 
 change is effected in a few minutes. The silk must then be wrung by 
 hand, and rinsed in running water without beating. After this it is dried 
 on the poles, in the same manner as other dyed silks. It need be left on 
 the poles only twenty hours, to give the colour time to come out well ; 
 for it is observed, that this colour, far from fading in the drying, as is the 
 case with many other colours, is improved, and acquires a greater richness 
 of tint. The solution of a little soap added cold to the ammonia bath 
 improves it, giving also softness to the silk, and rendering it more easy to 
 separate. The soap must be uniformly dissolved. 
 
 Woollen cloth takes the above dye, but it must be left longer than silk 
 in the iron mordant. 
 
 In 1819, M. Braconnot, of Nancy, applied sulphuret of arsenic (opi- 
 ment) to stuffs, so as to give them a yellow dye. He mixed one part of 
 sulphur, two parts of arsenious acid, and five parts of potash of commerce. 
 This mixture is fused in a crucible, at a heat approaching to redness. The 
 resulting ,yellow mass is to be dissolved in hot water ; and the liquor is 
 filtered to separate it from a sediment formed in a great measure of metal- 
 lic arsenic in brilliant scales, and of a small quantity of a flocky chocolate- 
 coloured matter, apparently a subsulphuret of arsenic. Into the filtered 
 liquor, diluted with water,'^ weak sulphuric acid is to be poured, which 
 causes a flocky precipitate of a superb yellow colour. This precipitate, 
 washed in a cloth, dissolves with extreme readiness in water of ammonia, 
 constituting a yellowish liquid, into which an excess of ammonia is poured 
 to deprive it entirely of colour. In this liquor, the wool, silk, cotton, or 
 linen to be dyed, is plunged ; and it may be diluted to any degree, cor- 
 
524 
 
 NOTES. 
 
 responding to the depth of shade wanted. The washed sulphuret of arsenic 
 should be dissolved in ammonia only when it is wanted ; and metallic 
 vessels or utensils should be carefully avoided. When the stuffs are taken 
 out of this bath, they are colourless ; but they imperceptibly assume a 
 yellow colour on the dissipation of the ammonia. They are, therefore, 
 freely exposed to the air, so that it may play over their surfaces ; and as 
 soon as the colour has taken its utmost intensity of shade, they may be 
 washed and dried. 
 
 Wool should be tramped in the ammoniacal bath till it is uniformly im- 
 pregnated with it ; it is then to be squeezed or wrung out very slightly 
 and uniformly, or it may be even allowed simply to drain. Silk, cotton, 
 hemp, linen, require merely to be dipped in the dyeing liquor. They are 
 very easily impregnated, and must be well wrung out. This colour is 
 affected only by alkahes. It may be had of every shade, from golden 
 yellows to the palest. — Annales de Chirn, ei de Phys, xii. 398. 
 
 M. J. L. Lassaigne, in 1820, published, in the Annales de Chimie et de 
 Physique, a process for fixing chromate of lead on cloths, which has since 
 become pretty common in this country. Alter immersing for a quarter of 
 an hour, at the ordinary temperature, hanks of scoured silk in a weak 
 solution of acetate of lead, he took them out and washed them with a 
 great deal of water. Thus prepared, they were dipped into a weak solution 
 of chromate of potash. They immediately took a fine yellow colour, and 
 at the end of ten minutes the effect was completed. From this colour 
 being decomposed in part by soap water, M. Lassaigne conceives that it 
 will be chiefly applicable to silks. But by applying a mordant of acetate 
 or nitrate of lead, and passing the goods through bichromate of potash, a 
 very beautiful and sufficiently fast yellow is now given to cotton goods 
 in this country. The bichromate acts instantly the mordant, and does 
 not require that duration of immersion which M. Lassaigne found to be 
 necessary with the neutral chromate. 
 
 The application of the chromate of lead on Turkey red cloth forms a 
 brilliant style of calico printing, now carried on to high perfection at the 
 estabhshment of Messrs. Monteith, at Glasgow. Nitrate of lead is dis- 
 solved in liquid tartaric acid, of a specific gravity about 1.250 ; this solu- 
 tion is thickened with gum, and apphed with the block to cloth previously 
 dyed Turkey red. Whenever the paste is dried, the cloth is slowly 
 passed through an aqueous solution, nearly saturated, of chloride of lime, 
 kept at the temperature of about 100° in a stone trough. The tartaric 
 acid disengaging the chlorine, discharges the colour of the Turkey red at 
 points of application, while the nitrate of lead, or rather, perhaps, the oxyde 
 of lead, remains attached to the cloth. This is immediately washed, and 
 then passed through a solution of bichromate of potash, by means of the 
 padding machine^ 
 
NOTES. 
 
 525 
 
 An orange colour was some time ago given to goods, in calico printing, 
 by means of the crystals of hydrosulphuret of soda and antimony, which 
 are hence called orange crystals. But the use of the alkaline solution of 
 sulphuret of antimony had been long known and practised by the Lanca- 
 shire printers. It was invented by Mr. John Mercer, at Messrs. Fort's. 
 The salt is formed by boiling finely ground sulphuret of antimony in 
 caustic soda ley, and crystallizing. 
 
 The thickened solution of the hydrosulphet is applied to the cloth, and 
 it is either washed off in weak sulphuric acid, or in water, after being left 
 some days on the cloth. This dye is bright and pleasing, but very fugitive, 
 and has hence gone into disuse. 
 
 For the following observations on calico printing, I am indebted to a 
 much esteemed friend, who unites scientific knowledge to practical skill. 
 
 Bleaching. — To bleach cloth for printing, it is first of all to be singed, 
 and then steeped in warm water (sometimes with an addition of spent 
 ley) for a day or two. It is then well washed and boiled in potash ley 
 five different times. 
 
 For 20001bs. (original weight) of cloth, 1000 gallons of water, and 
 40 to 45lbs. of potash are employed each time. The boiling is continued 
 eight or ten hours. 
 
 Betwixt each operation the cloth must be well washed, and after the 
 third and fourth boil it must be spread upon the grass, or steeped for a 
 night in a weak solution of chloride of lime. After this, it is winced a 
 few minutes in a warm dilute sulphuric acid, v/ell washed and dried. 
 
 The principal processes, or rather styles of work, as they are called, 
 are the following : — 
 
 1. Single coloured plates. 
 
 2. Ditto ditto grounded. 
 
 3. Light or dark chintzes. 
 
 4. Dark grounds, with a white discharge. 
 
 5. Blue grounds, with a white resist. 
 
 6. Blue grounds, with a red and white resist together. 
 
 7. Chemical or spirit colours. 
 
 1. Single Colours. — Called plates, from their being generally printed 
 with the copper-plate. This process consists generally in printing a mor- 
 dant upon the cloth ; which mordant attracts a colouring matter when 
 the cloth is dyed. The mordant is different, according to the colour that 
 is wanted. 
 
 For black. An acetate of iron is used of the sp. gr. 1.04 0. 
 
 For 'purple. An acetate of iron, sp. gr. 1.12, with six, eight, or twelve 
 times its volumxe of water, according to the shade of colour required, and 
 the mass to be printed. 
 
526 
 
 NOTES. 
 
 For red, A solution of three pounds alum in a gallon of water, one- 
 half of which is decomposed by acetate of lime or lead. 
 
 For chocolate. Mixtures of acetate of iron, sp. gr. 1,12, with red 
 mordant, in the proportions of one to two, four, six, according to the shade. 
 
 Each of these mordants is thickened with flour, or, in some cases, with 
 gum, and printed upon the bleached cloth. 
 
 After being exposed to the air for a few days in a warm room, the 
 goods are taken down and passed through the dung copper, at a heat of 
 from 150° to that of boiling water. They are then washed, and winced 
 in another clean dung copper, at a lower degree of heat than before, and 
 then washed again. They are now ready to be dyed. 
 
 All the colours last mentioned, viz. black, purple, red, and chocolate, 
 are dyed with madder and sumach, except purple, in which the sumach 
 is omitted. Different quantities of madder are used, according to the 
 quantity of colour on the cloth, from one pound per piece of 21 square 
 yards, to three and even three and a half pounds ; the sumach about 
 one-eighth of the madder. The goods are entered when the copper is 
 cool, and the heat is brought up gradually during two or three hours, and 
 sometimes the ebuUition is kept up for a quarter of an hour ; the pieces 
 all the while being turned over a wince, from the one side of the copper 
 vessel to the other. They are then washed, and boiled in bran and water 
 ten or fifteen minutes. 
 
 If they have much white, they must be hranned a second and a third 
 time, washing between each operation. 
 
 To complete the whitening, they are spread upon the grass for a few 
 days ; or what is more expeditious, and more generally practised now^ 
 they are winced a short time in a warm but weak solution of chloride of 
 lime. 
 
 For indigo blue, A strong solution of caustic potash is made, in every 
 gallon of which, by* the aid of as much orpiment, twelve or sixteen ounces 
 of good indigo is dissolved. The solution, when clear, is thickened with 
 gum. This being printed upon the cloth, nothing more is necessary than 
 to wash it when dry. 
 
 For Prussian blue. The same mordant is used as for black ; but after 
 cleansing, the piece is winced in a solution of prussiate of potash, in which 
 the prussic acid has been set free by means of sulphuric acid. 
 
 For gold. Five pounds sulphate of iron, and one and a half pounds 
 acetate of lead are dissolved in a gallon of water : the solution, thickened 
 with gum, is printed on the cloth ; and, after eight or ten days' age, is 
 winced in a solution of potash made thick with lime. As soon as the 
 black oxyde of iron, which is precipitated, commences to redden, the 
 piece is removed to a vessel of water, and then washed. 
 
 2. Single colours grounded, — A second, and sometimes third colour, is 
 
NOTES. 
 
 527 
 
 grounded or printed in with a small block, generally after the first has 
 been dyed. 
 
 Bark yellow, A mordant is used, the same as for red. The piece, 
 when slightly dunged, is dyed about an hour with one pound of quer- 
 citron bark, the infusion being gradually heated during that time to 130° 
 or 160° 
 
 Berry yellow, A decoction of French, or Turkey, or Persian berries, 
 with half a pound of alum per gallon, is thickened with flour or gum ; 
 and the piece, when dry, is passed through a weak alkaline carbonate, or 
 lime water. 
 
 Verdigris green, A solution of sulphate and acetate of copper is put 
 on cloth, which is then passed through a strong solution of potash, in 
 which some protoxyde of arsenic has been dissolved. 
 
 Drab, The same mordant as is used for purple. Bark, the dye stuff. 
 
 Olive, The chocolate mordant dyed in bark. Both these very much 
 diluted, and thickened with gum. 
 
 Buff, A weak acetate of iron is applied, and washed in water. 
 
 3. Chintzes. — A number of different colours printed upon cloth together, 
 viz. black, red, one or two pale reds, purple, blue, green, and yellow. The 
 black, red, and blue, are the same as in No, 1. ; the purple, as No. Ij 
 thickened with gum ; the two pale reds are weaker solutions of alum and 
 acetate of alumina, thickened with gum ; the yellow is berry yellow 
 applied after the other colours are finished ; the green is formed by the 
 yellow falling upon the blue ; and all the varieties of orange, olive, &C.5 
 by its falling upon the pale reds and purple. The dyeing and subsequent 
 bleaching are the same as has been described in No. 1, with madder 
 only. 
 
 4. A dark ground discharged, — When the discharge is printed before 
 the mordant, it consists of concentrated lime juice alone, thickened with 
 gum. The mordant, which is also thickened, is blotched over the whole 
 piece, and dried off it as quickly as possible. 
 
 When the mordant is applied first it is not thickened, and the acid has 
 an addition of one pound bisulphate of potash in each gallon. They are 
 dunged and dyed like other single colours. Blacks, instead of madder- 
 are generally dyed with logwood and galls. 
 
 5. Blue grounds.' — To make a blue paste for dark blues, three to four 
 pounds sulphate of copper are dissolved in a gallon of water, with a pound 
 or a pound and a half of acetate of lead. The clear solution is thickened 
 with pipe-clay and gum. The pieces printed with this paste are hooked 
 upon a frame, and dipped in a weak blue vat five or six times ; then taken 
 out and kept in the air till they become blue. Alternate immersions and 
 airings are thus continued till the requisite shade has been obtained. 
 The goods are then washed and dipped in a weak sulphuric acid, to dis- 
 
528 NOTES. 
 
 solve the oxyde of copper. The hhie vat, as is well known, is nnade by 
 one part of indigo, with two parts sulphate of iron, and about two and a 
 half parts hydrate of lime. 
 
 6. A mordant for red, to resist the blue vat, is made by dissolving 
 about four ounces acetate of copper in a red mordant, ^nade from four 
 pounds of alum, and two and a half pounds acetate of lead, per gallon, 
 and thickening the solution with pipe-clay and gum. When this is printed 
 upon the cloth and dipped in the blue vat, it resists the blue, and a white 
 is left, which, when dunged and dyed in madder, becomes red. 
 
 A white called neutral, is made by dissolving sulphate of copper in 
 concentrated lime juice, and is used along with this red. It must possess 
 the three following properties: 1. Resisting the blue; 2. Remaining 
 white after dyeing, when the red happens to go over it ; 3, To leave no 
 oxyde of copper upon the cloth. 
 
 A berry yellow is grounded in after the blue, white, and red, in this 
 style, are finished. 
 
 7. Chemical colours, — This name has been given to those colours which 
 are applied topically ; most of them are fugitive. 
 
 Black, A decoction of logwood and galls, thickened with flour, and, 
 when cold, nitrate of iron mixed with it. 
 
 Red. A decoction of brazil or peach wood, with the protomuriate or 
 permuriate of tin. 
 
 Purple, A decoction of logwood with muriate of tin. 
 
 Blue, Ground prussian blue is soaked in muriatic acid for a day or 
 two, and then as much of it mixed with gum tragacanth water as is 
 sufficient to give it the desired shade. 
 
 Yellow, A decoction of fustic with muriate of tin. 
 
 Green, A mixture of the blue and yellow. 
 
 All these colours are simply washed off in water. 
 
 M. Vitalis gives the following prescriptions in calico printing : — 
 
 Mordant for Reds, 
 
 52 J gallons of boiling water ; 
 150 pounds of pure alum ; 
 50 pounds of acetate of lead ; 
 6 pounds of commercial potash or soda 4 
 6 pounds of chalk ; 
 3 pounds of ground brazil wood. 
 Into a vat capable of holding 87i gallons, and partly filled with the 
 52J gallons of boiling water, the alum in powder is put, and then the 
 decoction of brazil wood. After stirring till the alum is dissolved, the 
 acetate of lead in powder is added. The mixture is to be carefully 
 stirred for some time, and when the liquor begins to clarify, the potash 
 
NOTES. 
 
 529 
 
 is put in, then the chalk, in small portions at a time, to avoid too great an 
 effervescence. The whole must now be stirred for an hour, and left to 
 settle. The clear liquor is used as occasion requires. 
 
 For strong reds (full reds) the above mordant is thickened with starch. 
 This is called first red. 
 
 If reds of a weaker tone be wanted, the mordant is thickened with 
 gum. 
 
 For the second red three quarts of the mordant are thickened with two 
 pounds and a half of gum dissolved in a quart of cold water. The whole 
 is well mixed by due agitation. 
 
 For the third red three pints and a half of mordant are mixed with the 
 solution of five pounds of gum dissolved in ten pints and a half of cold 
 water. 
 
 The above red mordant serves also for weld fustic and quercitron 
 yellows, with all their shades. 
 
 Mordant for Blacks. 
 
 12 quarts of iron liquor, (pyrolignite of iron.) 
 4 ounces of copperas. 
 
 Dissolve the copperas in the liquor ; and after having decanted the 
 clear, mix in gradually four pounds of starch. Heat in a boiler, stirring 
 continually, and take it out when the starch is well boiled. 
 
 Another Black Mordant. 
 
 For eight pounds of iron liquor, take about two pounds and a half of 
 superfine wheat flour, which is to be gradually mixed up with a portion of 
 the liquor; then add the remainder of this, and leave at rest for 12 or 
 24 hours, or even longer. Then boil for half an hour, or till the mixture 
 has acquired the consistence of a paste. The boiler is then to be removed 
 from the fire, and the mordant is to be stirred till it becomes cold. It is 
 now to be passed through a sieve, and used in printing. 
 
 These mordants give a beautiful black with logwood, and especially 
 madder. 
 
 Under the article Chemical Black, (topical black,) in Rees' Cyclopedia, 
 (article Colour,) we have the following recipes. 
 
 To a decoction of Aleppo galls, in five times their weight of water, 
 made into a paste with flour, add a solution of iron in nitrous acid, of 
 specific gravity 1.25, in the proportion of one measure of nitrate of iron 
 to 18 or 20 of the decoction, and a black will be formed fit for almost all 
 the purposes of calico printing, and possessing the chief requisites of this 
 colour, namely, tolerable fixity, and a disposition to work well with the black. 
 
 When a nitric solution of iron is added to a decoction of galls, the 
 
 2 M 
 
530 
 
 NOTES. 
 
 solution is decomposed, the oxyde of iron unites with the gallic acid and 
 tanning principle, while the nitrous acid is disengaged. This appears 
 from the blackness which the solutions assume immediately on being 
 mixed. The disengaged acid, however, reacts in a short time on the new 
 compound, the blackness gradually disappears, and if the nitrate of iron 
 has been added in proper quantity, the paste in a few days becomes, from 
 black, of a dirty olive green. When the proportion of nitrate of iron is 
 greater than i^, this change takes place sooner ; and if it amounts to tst, 
 the paste, when applied to the cloth, will be a bright orange, like the 
 acetate of iron. By exposure to heat and air this colour generally 
 deepens, becoming grey, and at last a full black. In this state it is per- 
 manent, and adheres powerfully to the cloth. 
 
 These changes of colour depend on the solution of the tannate and 
 gallate of iron in the disengaged nitrous acid, and the dissipation of the 
 acid from the cloth, when it is exposed to heat and air. This solution of 
 the tannate and gallate of iron is indeed an essential requisite to the 
 goodness of the chemical black. If the disengaged acid is not sufficient 
 to effect this, or if it is in a state of too great dilution, the colour has but 
 a feeble adherence to the cloth. It is not presented in a state favourable 
 to its union with it, since the combination into which the iron has entered 
 is insoluble in water. It lies merely on the surface, but does not pene- 
 trate its fibres, and gives way readily in the various operations to which it 
 is subjected. This chemical black, therefore, is a solution of the tannate 
 and gallate of iron in nitric acid. 
 
 Mordants for Violets, (from Vitalis.) 
 
 First violet, — ] 6 quarts of iron liquor ; 
 
 8 quarts of water ; 
 
 4 ounces of Roman vitriol, (sulphate of copper.) 
 
 This mixture is to be thickened with powdered gum, in the proportion 
 of a pound to the quart. 
 
 Second violet, — Mix three parts of the preceding with one of water, and 
 thicken as above. 
 
 Third violet, — Dilute two parts of the first mordant, with three of water. 
 
 Coffee Colour, 
 
 10 quarts of iron liquor ; 
 
 2 quarts of the mordant of the first red ; 
 
 4 quarts of water. 
 Thicken with starch. 
 
NOTES. 
 
 531 
 
 Puce, or Carmelite Colour. 
 3 quarts of mordant of the first red ; 
 
 1 quart of iron liquor. 
 
 Deep Brown, 
 
 2 quarts of red mordant ; 
 
 1 pint of iron liquor. 
 
 Marroon Colour (^Chestnut-Brown,) 
 
 2 quarts of. violet mordant ; 
 1 quart of red mordant ; 
 
 8 ounces of green copperas to be dissolved in the 
 mixed mordants. 
 
 Chocolate, 
 8 quarts of violet mordant ; 
 12 quarts of red mordant. 
 
 Deep Lilac, 
 1 quart of violet mordant ; 
 1 quart of mordant for the second red. 
 
 Pale Lilac. 
 1 quart of violet mordant ; 
 
 3 quarts of mordant of the second red. 
 
 Musk Colour. 
 1 quart of red mordant ; 
 3 quarts of black mordant. 
 
 Incarnate (JFlesh) Colour ; Colour between Cherry and Rose. 
 10 quarts of red mordant ; 
 1 quart of black mordant, 
 
 Olive Colour, 
 
 Welding on the mordant of the first, second, or third violet. 
 
 Reseda Colour. 
 Welding on puce mordant. 
 
 Colours of Application (Topical Colours) from Vitalis. 
 Topical, or Pencil Blue. 
 Boil in 15 gallons of water, for half an hour, 15 pounds of potash, and 
 six pounds of quicklime, in order to render the potash caustic. Then add 
 
532 
 
 NOTES. 
 
 six pounds of orpiment (sulphuret of arsenic) reduced to fine powder, 
 and continue the boiling for a quarter of an hour^ taking care to stir con- 
 tinually with a rod. When the boiler is a little cooled, pour into it from 
 six to eight pounds of indigo well ground at the mill, and stir again till 
 the indigo be well dissolved, which is discovered by a drop of the liquor, 
 when placed on a bit of glass, appearing yellow. The bath, while still 
 hot, is to be thickened with a pound of gum for every three pints and a 
 half of liquor, or with eight ounces of starch. 
 
 This preparation must be carefully preserved from contact of air, and 
 only employed when its colour is yellow, or at least, yellowish-green. If 
 it become blue, the liquor is to be treated anew with some pounds of 
 caustic potash and orpiment. 
 
 This blue of application, says M. Vitalis, much used formerly, is seldom 
 employed at the present day. Another blue, of less permanence, but 
 more brilliancy, is now preferred. It is made with prussian blue, in the 
 following manner : — 
 
 Into an earthen pot, four ounces of finely ground and sifted prussian 
 blue are to be put. Over this must be slowly poured, stirring all the while, 
 sufiicient muriatic acid, to bring it to the consistence of syrup. The 
 mixture is to be stirred every hour for a day, and afterwards thickened 
 with from 14 to 28 pints of gum-water, according to the shade wanted. 
 
 Topical Med. 
 
 A pound of brazil wood is to be boiled in seven pints of water for two 
 hours ; the decoction is then to be decanted, and boiled down to three 
 pints and a half. As much red mordant must now be added as is neces- 
 sary to form a fine red ; and it is to be finally thickened with eight ounces 
 of starch. The colour will be more beautiful the older the decoction of 
 brazil wood is. 
 
 Instead of brazil wood, wood of Japan, Saint Martha, or Nicaragua 
 (peach wood,) may be used, provided their colour has been refined from 
 the dun which they contain, by the process with milk, previously described 
 under note PP. 
 
 Topical Yellow, 
 
 This is prepared by boiling four pounds of Turkey or Avignon berries 
 in five gallons and a quarter of water, which is boiled down to one-half. The 
 clear liquor is drawn off, and a pound and a half of alum is dissolved in 
 it. For the light yellows it is thickened with gum j for the deep with 
 starch. This topical yellow does not resist soap. The following is 
 equally fast and agreeable. 
 
 In two gallons of water boil four pounds of quercitron bark in powder, 
 
NOTES. 
 
 533 
 
 down to one-half of the bulk. Pass through the searce, thicken with 
 three pounds of gum, and mix in gradually enough of solution of tin to 
 render the colour of a brilliant yellow. This yellow resists vegetable 
 acids and soap very well. When placed on a blue ground, it forms a 
 fine green, and it may be applied by the plate or the pencil. 
 
 The best solution of tin which can be employed for this topical yellow, 
 is that made with a mixture of three ounces of muriatic acid, four Ounces 
 of nitric, and four ounces of pure water. Two ounces of grain tin are to 
 be dissolved bit by bit in this liquor. When the solution is completed, 
 half an ounce of sugar of lead is to be added. The mixture must then 
 be well stirred ; left to settle, and decanted. Half an ounce of this solu- 
 tion is to be taken for every quart of the yellow bath. 
 
 On mixing with the yellow bath a little of the annotto bath, we have 
 orange yellows. 
 
 Rust' Yellow, ^ 
 
 This is made with acetate of iron, or the black cask. It is thickened 
 with gum for the light yellows, and with starch for the deeper shades. 
 Rust-yellow, when applied on blue, gives a deep green, which serves for 
 the stems of certain flowers. 
 
 Topical Green. 
 
 This preparation is formed by a mixture of topical blue and yellow, in 
 which the yellow predominates considerably. The mixture must be made 
 by little and little with the utmost care, so as to hit the wished-for shade. 
 
 Topical Auroi^a, 
 
 A sufficient quantity of alum in solution must be added to the annotto 
 bath ; and the mixture is to be thickened with gum. 
 
 Topical Black, 
 
 To three gallons of the black cask, or of pyrolignate of iron, at 4° 
 Baume (5J° Tw.) add four ounces of Roman vitriol dissolved in water, 
 and a sufficient quantity of decoction of galls to form a good black. Thicken 
 with three pounds and a half of starch, which is to be gradually worked 
 up with a portion of the liquor. Boil, withdraw from the fire, and keep 
 stirring, till the liquor be cool ; it must then be passed through a searce 
 or a linen cloth. 
 
 Another Topical Black, 
 In six gallons of water, boil two pounds of logwood, two pounds of su- 
 mach, and eight ounces of galls, till the liquor be reduced to half its volume. 
 Add then a quart of the black cask (or pyrolignate of iron ;) boil away 
 
534 
 
 NOTES. 
 
 six quarts ; take oflF the clear of the bath, dissolve in it two ounces of 
 Roman vitriol, and one ounce of sal ammoniac ; after which thicken with 
 starch, and pass through a search before making use of the composition. 
 
 Topical Violet and Lilac, 
 
 •In seven gallons and a half of water boil six pounds of logwood, ground 
 or in chips, till ten quarts be evaporated ; {jusqiCa reduction de dix pintes^ 
 Decant the clear, and dissolve in it one ounce of alum for every quart of 
 liquor. The deep violets are thickened with starch, and the light violets 
 with gum, which is to be dissolved in the cold. 
 
 This colour changes readily ; for which reason it should be prepared 
 only as wanted, and be immediatelj^ put to use. 
 
 EXAMPLES FROM VITALIS OF THE MODE OF MANAGING DIFFERENT STYLES 
 OF CALICO PRINTING. ^ 
 
 Calicoes of 07ie Block (Indiennes d une main,) 
 First Example, — Violet on a white ground. 
 
 1. Impression of violet mordant; 2. Dunging and washing; 3. Mad- 
 dering ; 4. Branning and exposure on the grass for a few days, to clear 
 the grounds. 
 
 Second Example,— Black on a yellow ground. 
 
 I. Bath of yellow mordant ; 2. Welding; 3, Topical black. 
 
 Calicoes of two Blocks, 
 First Example, — First olive and second olive on a white ground. 
 1. Impression of the first olive mordant; 2. Impression of the second 
 
 olive mordant: 3. Welding. 
 
 Second Example, — Red and blue on a white ground, 
 
 1. Impression- of the red mordant: 2. Maddering ; 3. Impression by 
 
 the block (rentreur^) of topical blue. 
 
 Third Example, — Yellow and black on a white ground. 
 
 1. Impression of the yellow mordant, welding ; 2. Impression of topical 
 
 black. 
 
 Calicoes of three Blocks. 
 Example, — First olive, second olive, and yellow on a white ground. 
 1. Impression of the first olive mordant ; 2. Impression of the second 
 olive mordant ; 3. Impression of the yellow mordant ; 4. Welding. 
 
 * When the calico is to have several colours, says M. Vitalis, for example, black, 
 several reds, several violets, &c., as many mordants must be given as there are different 
 colours, which must be inserted (ventres) into the first plate (figure,) called the plate of 
 impression (printing hlock, planche cT impression.) 
 
 The insertion (rentrage) of the mordants is executed by means of blocks (planches^) 
 
NOTES. 
 
 535 
 
 The third block (main) might also be performed by the impression of 
 the topical yellow. 
 
 Calicoes of fou?' Blocks, 
 
 Example, — Black, red, violet, and yellow on white. 
 
 1 . Impression of the black mordant ; 2. Impression of the red mordant ; 
 3. Maddering ; 4, Impression of topical yellow, or of the yellow mordant, 
 and welding. 
 
 Calicoes of five Blocks, 
 Example, — Black, red, violet, yellow, and blue. 
 
 1. Impression of the black mordant; 2. Impression of the red mor- 
 dant ; 3. Impression of the violet mordant ; 4. Maddering, insertion of 
 the blue, and afterwards of the yellow. 
 
 Calicoes of six Blocks, 
 
 Example. — First olive, second olive, black, first red, second red, and 
 yellow on white ground. 
 
 I . Impression of the black mordant ; 2. Impression of the first red 
 mordant : 3. Impression of the second red mordant ; 4. Maddering ; 5. 
 Impression of the second olive mordant ; G. Impression of the yellow 
 mordant ; 7, Welding. 
 
 It is now very seldom, however, that the number of three blocks (courses) 
 is exceeded, on account of the high price to which the labour would ne- 
 cessarily raise the calico. 
 
 The following is an example of printing in fugitive colours : 
 
 Violet, black, red, and yellow, on white ground. 
 
 These four topical colours are successively applied, in the order above 
 mentioned. 
 
 Calicoes with fast colours, after receiving the impressions, are dried, 
 and washed from the mordants, when they are ready for the maddering. 
 
 which take the name of rentreures. These blocks are engraved with the same patterns 
 as the printing blocks, but so as that they apply the new mordants only to the places of the 
 pattern reserved in the first blocks. It may be readily conceived how necessary it is for 
 these blocks to have an exact correspondence with one another, otherwise the colours would 
 not be comprised within the limits of their outlines. This fault is too often met with in 
 common prints, on account of the rapidity with which they are worked off, and the little 
 care taken in the fabrication. In order that every colour may occupy the place assigned to 
 it in the drawn pattern {le dessein enlumine,) adjusting brass points {picois de rapports) are 
 made use of, which guide the printing on of the successive mordants, at precisely that 
 place of the figure where the colour to be produced from each mordant ought to fall. 
 
536 
 
 NOTES. 
 
 Of Pinnting by Reserves ^ (with Meserve or Defending Pastes.) 
 
 Goods printed by reserve, are so called, because the colour does not 
 strike the whole surface, but only certain unprotected portions of it. 
 The reserve is composed of the reserve bath, and the thickening. 
 
 Meserve Bath, 
 
 Dis§olve in a quart of water six ounces of sulphate of copper, three 
 ounces of verdigris, two ounces of alum, and four ounces of gum arable. 
 
 Another Reserve Bath, 
 Dissolve in three pints and a half of water four ounces of Roman vitriol 
 (sulphate of copper,) and six ounces of verdigris, to which add one pound 
 of gum arable ; and when it is dissolved, pass through a fine sieve, or let 
 it settle, and decant. 
 
 Thickening. 
 
 To thicken the bath, knead a pound of pipe-clay, well ground and sifted, 
 with three or four ounces of water : with this thick dough carefully mix 
 the reserve bath, and triturate well before making use of it. 
 
 The reserve is printed on the goods like the mordants. Twenty-four 
 hours after the impression the goods are to be passed through the dyeing 
 vat. This style is much used in blue dipping. 
 
 The theory of the reserve is very simple. The oxyde of copper, which 
 forms the basis of the reserve, restores to the indigo the oxygen which it 
 had been deprived of by the sulphate of iron. The re-oxydised indigo loses 
 its solubility, and consequently cannot fix on the stuff. 
 
 Since the reservd, intended to nullify the action of the indigo, essentially 
 acts merely by the oxyde of copper which it contains, it follows, that the 
 proportions of this oxyde are not indifferent, and that the measure will not 
 perfectly accomplish its end, unless the dose of oxyde of copper, which 
 the sulphate, &c., can furnish, be adequate to neutrahze the action of the 
 indigo. A similar result would ensue, if the reserve be not suitably 
 thickened. 
 
 Some object to the introduction of alum. 
 
 The proportions of the cupreous salts ought, however, to be as little as 
 can effect the purpose ; if their quantity be too great, their operation 
 would be extended to the indigo diffused through the bath. 
 
 Sometimes the sulphate of copper is made to predominate, and some- 
 times the acetate. 
 
 The following recipes for reserves are given by M. Vitalis : — 
 1. Sulphate of copper .... 20 pounds 
 Acetate of copper . . . . 12 
 
NOTES. 
 
 537 
 
 Gum 
 Alum 
 Water 
 2. Sulphate of copper 
 Acetate . 
 Alum . » 
 Gum 
 Water 
 
 The thickening is always made with pipe-clay. 
 
 IG pounds 
 5 
 
 7 gallons 
 16 pounds 
 24 
 
 4 
 
 15 lbs. 8 oz. 
 1 J gallons 
 
 To make a Sky-blue on a Dark Blue, 
 1. Dye the cloth of a sky-blue ; 2. Apply the usual reserve ; 3. Pass 
 the cloth through a strong blue vat. Brighten in a bath, feebly acidulated 
 with oil of vitriol, (or muriatic acid), to carry off the particles of lime 
 suspended in the vat. Wash and dry. 
 
 Sky-blue i Dark Blue, and White, 
 ]. Apply the reserve ; 2. Dye sky-blue ; 3. Apply the reserve anew ; 
 4. Pass through a blue vat of sufficient strength. 
 
 Deep Blue, Sky-blue, Green, Yellow, and White, 
 1. Print on the reserve: 2. Pass through a weak vat, giving two or 
 three dips ;• dry, brighten with very dilute sulphuric acid, wash, dry again ; 
 3. Print on once more the common reserve paste ; 4. Dye in a stronger 
 vat than the above, till the blue be sufficiently deep ; dry, brighten as 
 before, wash and dry ; 5. Print on the red mordant, and dry ; 6. Give 
 the weld or quercitron. The mordant applied to the white spots, and to 
 the pale blue, (^petit blanc), allbrds yellow and green. The white portions 
 that have not been touched with the mordant remain white, in like 
 manner as the pale blue spaces, not covered by this mordant, furnish the 
 pale blue. 
 
 Reserves are also applied to silks. 
 
 For example, on the handkerchiefs csXl^di foulards, the reserve is styled 
 waxing, 
 
 A mixture of tallow and rosin is melted, and applied to the silk with 
 the block ; this reserve being given, the silk is dipped in the blue vat. 
 The reserved portions being defended from the action of the indigo, 
 remain white, while the rest of the surface takes a fast blue. 
 
 Sky-bhie, Bed, and White, 
 1. Apply the usual reserve ; 2. Apply the red mordant, thickened 
 with pipe-clay, and dry ; pass through a weak blue vat, to obtain sky-blue ; 
 wash at the river, madder, wash, and spread out on the grass to clear the 
 white. 2 N 
 
538 
 
 NOTES. 
 
 Printing with Discharges (par rongeant) on a Mordant. 
 
 This process serves to form mourning garments, composed of a white 
 figure on a black ground. 
 
 The piece of goods is first passed through the black mordant, (by means 
 of the padding or blotching machine.) When this mordant is very dry, 
 (by passing, for example, over steam cylinders,) the white discharge is 
 applied, prepared with nitric, oxalic, tartaric, or citric acid, or bisulphate 
 of potash, thickened with British gum. It is dried, washed, and maddered. 
 On quitting the madder bath, the goods must be well washed, and exposed 
 on the grass till the whites be very clear. 
 
 The portions of the cloth where the mordant has not been acted on by 
 the discharge, will take a black of a greater or less depth from the madder, 
 while on those places where the discharge has been applied, the mordant 
 will be removed, and the madder colour will not combine with the stuff. 
 Exposure on the grass will carry off the loose madder. 
 
 In like manner, by this process, white figures may readily be obtained 
 on a ground of red, carmelite, violet, puce, &c. ; since it will be necessary 
 merely to pass through the mordant of one of these colours, then to apply 
 the white discharge, and finally to madder. 
 
 To have white figures on an olive ground, weld or quercitron must be 
 used instead of madder. 
 
 Printing with a Discharge on Colour, (JDyed Goods,) 
 
 Suppose that the calico has been dyed in a logwood bath, mixed 
 with iron liquor, the cloth will take a black colour. If, after dyeing, it 
 be impressed with a solution of tin, properly thickened, the ferruginous 
 portions of the cloth touched with the discharge will be removed, and 
 they will pass from a deep black to a very brilliant crimson. 
 
 By subjecting to the same treatment calicoes dyed of different colours 
 and shades, determined by the different degrees of oxydizement of the 
 iron, a multitude of varieties will be produced, either in the colours or in 
 their shades. 
 
 By a similar operation, we may make figures of a beautiful green on 
 goods, by dyeing them first of a pale blue in the indigo vat, passing them 
 then through a bath of sumach and sulphate of iron, and finishing in a 
 bath of quercitron with alum. 
 
 Here the green colour produced by the indigo and the quercitron re- 
 mains masked, as well as the other colours, by the oxyde of iron in the 
 sulphate, till the solution of tin be applied, which causes the other colours 
 to disappear, and gives to those that remain a lustre which they would 
 not otherwise have had ; because the solution of tin renders the quercitron 
 
NOTES. 
 
 539 
 
 yellow more vivid, and because from this vivid yellow, associated with the 
 blue, results a more brilliant green. 
 
 A figure of aurora colour on an olive ground may be made, by passing 
 the cloth first through a bath of sumach and sulphate of iron, then washing 
 in an alkaline decoction of fustet, and printing on at last the solution 
 of tin. 
 
 Let us give for an example the mode of making yellow figures on olive. 
 The problem is reduced to find a discharge, which, in destroying the 
 colour communicated by iron, can at the same time change the colour to 
 yellow. This discharge is the thickened solution of tin. To the solution 
 of salt of tin (muriate) a little muriatic acid is added. This is thickened 
 with starch, previously boiled, in a very thick and cold state, observing to 
 pour in the solution in small portions, in order to ensure the thorough 
 union of the ingredients. As soon as the piece has been impressed with 
 this discharge, it is carried to the river to be washed, and to prevent the 
 discharge from acting too long on the colour. If the pattern required 
 is black, it wouH.be necessary to^^pply,it,bef«^M,the4»yoy9W»d2scha/^^ 
 
 Calico Printing> hy the comhiiied M^^^^ on the Mordant 
 
 and on the Dye, , j 
 
 First Example. — Olive, ;yell6w, an^' Whi^t^i ',.,'>..: ' - ■ ' 
 
 1. Pass through the olive mordant. 2. Print on the white discharge; 
 wash and dry. 3. Weld. 4. Print on the yellow discharge. 
 
 Second Example. — Bright red, and dull red ; white, yellow, and black, 
 on an olive ground. 
 
 1. Print on the red mordant, 2. Madder. 3, Pass through the olive 
 mordant. 4. Print on the white discharge. 5. Weld. 6. Print on the 
 yellow discharge and the topical black, and wash. 
 
 The colours by discharges, though bright, are not so fast as those given 
 by the dye-baths. 
 
 If, instead of applying the yellow discharge, thickened as usual with 
 starch, one-third more starch be employed, and a colouring of decoction of 
 Turkey berries, or brazil wood, be added, we shall obtain, in the first case, 
 a richer yellow, and, in the second, an orange-yellow. 
 
 Of Lapis Lazuli, 
 
 This name is given to calicoes which, after having been printed with 
 reserve discharges, and different mordants, are passed in succession, first 
 through the blue vat and then through a madder bath. If a yellow or a 
 green be wanted, there is given, in the sequel of tne madder washing, a 
 yellow mordant, and the goods are turned through a bath of weld or 
 quercitron. 
 
540 
 
 NOTfiS, 
 
 Suppose that we are to print on cloth a pattern hito which there enter 
 white, red, black, blue, green, and yellow. The goods being previously 
 thoroughly whitened, we proceed as follows : — 
 
 1. Apply the reserve discharge.* 2. Print on the red mordant, 
 thickened with pipe-clay. 3. Print on the black mordant, thickened in 
 the same manner. Pass the goods through a strong vat in forty-eight 
 hours at farthest after the printing has been given. The dipping ought to 
 be for six minutes at most, at two times : between each dip, the goods 
 must be aired for five minutes. They are then carried to the river, allowed 
 to steep in it for an hour, and washed. 5 They are dunged. 6. Passed 
 through bran. 7. Maddered. 8. Beetled very carefully, and dried. 
 9. The red mordant is applied, which serves also as a yellow mordant. 
 The pieces are now to be well cleaned. 10. They are passed through a 
 quercitron bath, after which they are washed and finally dried. 
 
 The lapis pattern may be put on a blue ground, a red, puce, &c. ; 
 whence result a great many varieties. The pattern was originally called 
 lapi^^^3Vfi ^ts,«reserxTbj.ance,4a '/ajais /a 4 slight refiecfeipn on the above 
 process v^ ill' show lis 'aow^^ihe differbtlt co\6\itB t^x^ prod-ac'ed. 
 
 The blue is the immediate effect of the blue vat ; the red and black 
 are developed by :th'e: ntadd eiiwg von the ro5>p<3ctive mordants of these 
 colours. T^ie idombin^iAiop , of'^iylue with yellow^ on the yellow mordant, 
 gives green. The yellow results from the colouring matter of the quer- 
 citron bark fixed by the red mordant, which is, at the same time,, the m.or- 
 dant for yellow. Finally, the white is occasioned by the white discharge 
 of the reserve discharge. 
 
 A neat and expeditious style of discharge work on indigo grounds, has, 
 of late years, been extensively employed by the calico printers in this 
 country. A paste is made with aquafortis and pipe-clay, which is applied 
 in the press, by a revolving cylinder of wood, having the pattern cut upon 
 it. The cloth, immediately after receiving the impression, is passed 
 through a strong body of steam, at 212® Fahr., issuing from a row of small 
 orifices in a horizontal box. The high temperature gives blanching energy 
 to the nitric acid, and the accompanying moisture dilutes it, so as to pre- 
 vent corrosion of the cotton fibres. The safety of the goods, however, is 
 ensured by a thorough washing. 
 
 ^' The reserve discharge is prepared by melting together hog's-lard and rosin, {arcamion) 
 and Avhen the mixture is cool, diluting it with oil of turpentine ; adding afterwards binar- 
 soniate of potash, and a little corrosive sublimate in powder. The whole being well 
 blended or ground together, is to be then printed on. 
 
 W. Tyler, Printer, Bolt-court, London. 
 
^ Date Due 
 
 CCD (iKf 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
I 
 
 GETTY CENTER LIBRARY 
 
 3 31 
 
 25 00140 2680 
 
Cm.