GIFT OF 
 Miss E.T. w HIT* 
 
CORRECTIONS. 
 
 On Page 61 and 16th line from the top, for " Iodide of Silver," read Iodide 
 of Potassium. 
 On Page 167 and 2nd line, for " 32 ounces,'' read 64 ounces. 
 

HUMPHREY'S JOURNAL 
 
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A 
 
 PRACTICAL MANUAL 
 
 OF THB 
 
 COLLODION PROCESS, 
 
 GIVING IN DETAIL A METHOD FOE PRODUCING 
 
 POSITIVE AND NEGATIVE 
 
 0n 
 
 AMBROTYPES. 
 PRINTING PROCESS. 
 
 ALSO, 
 
 PATENTS FOR THE COLLODION PROCESSES; 
 
 MILAWOTTPIS PHOTOGRAPHS IK OIL ALBCMKHIZBD COLLODION CCTTIHO'S PATWTM 
 AKD CORBESPOSDKNOf. SPECIFICATION 07 ALL THE rOBEGOIVO, 
 SACH PROCESS KNTIBK. 
 
 THIRD EDITION, REVISED AND GREATLY ENLARGED. 
 
 By S. D, HUMPHREY. 
 
 NEW YORK: 
 
 UMPHEET'S JOURNAL PBINT, 
 87 LISPENARD STREET. 
 
 1857. 
 
ENTERED according to Act of Congress, in the 
 
 year 1857, by S. D. HUMPHEEY, 
 
 In the Clerk's Office of the District Court of the United States for the 
 Southern District of New York. 
 
PREFACE TO THE THIRD EDITION. 
 
 The rapid and unexpected sale of the entire second edition of 
 this Manual has induced the author to lay the Third Edition 
 before the Public. Although but little time has elapsed since 
 the second, yet there have been some new developments which it 
 has been thought best to give, as conducive to the interests of the 
 practitioner. The manipulations have been given somewhat more 
 in detail than in the Second Edition. 
 
 All that would have a tendency to confuse the reader has been 
 carefully avoided, and only the plain methods for operating laid 
 down. The work is intended for the beginner in the glass process 
 
 of producing Heliographic pictures. 
 
 S. D. H. 
 NEW YORK, February 1st, 1857. 
 
 248147 
 
PREFACE TO THE FIRST EDITION. 
 
 The object of this little MANUAL is to present, in as plain, clear 
 and concise a manner as possible, the practice of a COLLODION 
 PROCESS. This beautiful acquisition to (i sun-pencilling" was first 
 given to the public by Mr. FREDERICK SCOTT ARCHER, an English 
 gentleman, who alone is entitled to the credit, and deserves the 
 esteem of every lover arid practitioner of the Art, for his liberality 
 in giving it to the world. 
 
 The Process here presented has never before appeared in print, 
 and has been practised with the most eminent success by those who 
 have been enabled to adopt it. 
 
 All reference to the various systems or methods of manipula- 
 tion, by the thousands of practitioners, has been excluded, and one 
 Process given. I conceived that this was the better plan to adopt, 
 thus leaving the mind of the learner free from confusion, and 
 pointing out one course, which, if carefully followed, will produce 
 good and pleasing results. 
 
 I have also presented a list of all Patents upon the Collodion 
 Process; this will give all an opportunity of choosing their own 
 course in regard Lo the respect they may conceive to be due to such 
 Patent Rights. 
 
 S. D. H, 
 
CONTENTS, 
 
 PART I. 
 
 CHAPTEE L 
 
 Introduction Light Solar Spectrum Decomposition of Light 
 Light, Heat and Actinism Blue Paper and Color for the Walls of 
 the Operating Room Proportions of Light, Heat and Actinism 
 composing a Sunbeam Refraction Reflection Lenses Copying 
 Spherical Aberration Chromatic Aberration 13 
 
 CHAPTER H. 
 
 Camera Arrangement of Lenses Camera Tubes Camera Boxes, 
 Bellows, and Copying Camera Stands Head Rests Cleaning 
 Vice Nitrate Bath Leveling Stands Printing Frames Collo- 
 dion Vials 26 
 
 PART II. 
 
 Practical Hints on Photographic Chemistry. 
 
 CHAPTER III. 
 
 Soluble Cotton Manipulation Plain Collodion Bromo-Iodized Collo- 
 dion for Positives Ditto for Negatives Solution of Bromide and 
 Iodide of Potassium and Silver Double Iodide of Potassium and 
 Silver Developing Solution Fixing the Solution Brightening 
 and Finishing the Image Photographic Chemicals 41 
 
 PART III. 
 
 Practical Details of the Positive or Ambrotype Process. 
 
 CHAPTER IV. 
 
 Lewis's Patent Vices for Holding the Glass Cleaning and Drying the 
 Glass Coating Exposure in the Camera Developing Fixing or 
 Brightening Backing up, &c. 129 
 
XII CONTENTS, 
 
 PART IV. 
 
 Practical Details of the Negative Proces4 
 
 CHAPTER V. 
 
 Negative Process Soluble Cotton Plain Collodion Developing Solu- 
 tion Re-Developing Solution Fixing the Image Finishing the 
 Image Nitrate of Silver Bath 143 
 
 PART V. 
 
 Practical Details of the Printing Process. 
 
 CHAPTER VI. 
 
 Printing Process Salting Paper Silvering Paper Printing the Posi- 
 tive Fixing and Coloring Bath Mounting the Positive Facts 
 worth Knowing 151 
 
 CHAPTER VII, 
 
 Hdio Process. An Entire Process for Producing Collodion Positives 
 and Negatives with one Bath, and in much less time than by any 
 other known Process : by HELIO Photographic Patents 161 
 
 CHAPTER VIII. 
 The Collodio- Albumen Process in Detail 190 
 
 CHAPTER IX. 
 
 On a Mode of Printing Enlarged and Reduced Positives, Transparen- 
 cies, &c., from Collodion Negatives On the Use of Alcohol for 
 Sensitizing Paper Recovery of Silver from Waste Solutions, 
 from the Black Deposit of Hypo Baths, &c. The Salting and AI- 
 bumenizing Paper On the Use of Test Papers Comparison of 
 British and French Weights and Measures 191 
 
CHAPTER L 
 
 SPECTRUM ; DECOMPOSITION 'OF LIGHT 
 
 LIGHT, HEAT AND ACTINISM BLUE PAPER AND COLOR 
 
 fOR THE WALLS 6F THE OPERATING ROOM PROPOR- 
 TIONS OF LIGHT, HEAT ANO ACTINISM, COMPOSING A SUN- 
 BEAM- REFRACTION-- REFLECTION- LENSES- COPYING 
 
 'SPHERICAL ABERRATION- CHROMATIC ABERRATION^ 
 
 IT has been well observed by an able writer, that it is 
 impossible to trace the path of a sunbeam through our atmos- 
 phere without fee-ling a desire to know its nature, by 
 what power it traverses the immensity of space, and the 
 Various modifications it undergoes at the surfaces and the 
 interior of terrestrial substances. 
 
 Light is white and colorless, as long as it does not come in 
 contact with matter. When in apposition with any body it 
 suffers variable degrees of decomposition, resulting in 
 color, as, by reflection, dispersion, refraction and unequal 
 absorption. 
 
 To Sir I. Newton the world is indebted for proving the 
 -compound nature of a ray of white ligh<t emitted from the 
 sun. The object of this work is -not to engage in an ex- 
 tended theory upon the subject of light, but to recur only 
 to some points-of more particular interest to the photographic 
 operator. 
 
 The -decomposition of a beam of light can be noticed by 
 exposing it to a prism. If, in a dark room, a beam of light 
 
 2 
 
?IS.$, SOLAR SFECTR0M, 
 
 be admitted through a small hole in a shutter, it will foiiis 
 a white round spot upon the place where it falls. If a tri- 
 angular prism of glass be placed on the inside of the 
 dark room, so that the beam of light falls upon it, it no- 
 longer has the same direction, nor does it form a round spot, 
 but an oblong painted image of seven colors -red, orange, 
 yellow, green, blue, indigo, and violet. This is called the 
 solar spectrum, and will be readily understood by refer- 
 ence to the accompanying diagram, Fig. 1 , 
 Fig, 1. 
 
 Vioiet 
 
 J Indigo 
 JBftte 
 
 3 Green 
 Yellow 
 Or'nge 
 
 e- d. 
 
 To those who are unacquainted with the theory of light 
 (and for their benefit this chapter is given), it may be a 
 matter of wonder how a beam of light can be divided. 
 This can be understood when I say, that white light is a 
 bundle of colored rays united together, and when so incor~ 
 porated, they are colorless ; but in passing through the prism 
 the bond of union is severed, and the colored rays come 
 out singly and separately, because each ray has a certain 
 amount of refracting (bending) power, peculiar to itself. 
 These rays always hold the same relation to each other, 
 as may be seen by comparing every spectrum or rainbow ; 
 there is never any confusion or misplacement. 
 
 There are various other means of decomposing white 
 ght besides the prism, of which one of the principal and 
 
i.H-HT, HEAT, AND 
 
 18 
 
 most interesting to the photographer, is by reflection from co- 
 lored bodies. If abeam of white light falls upon a white sur* 
 face, it is reflected without change ; but if it falls upon a 
 red surface, only the red ray is reflected : so also with yel- 
 low and other colors ; the ray which is reflected corresponds 
 with the color of the object. It is this reflected decomposed 
 light which presents the beautifully colored image we see 
 upon the ground glass in our cameras. 
 
 A sunbeam may be capable of three divisions -LIGHT^ 
 HEAT, and ACTINISM ; the last causes all the chemical changes, 
 and is the acting power upon surfaces prepared to receive 
 the photographic image. The accompanying illustration, 
 Fig. 2, will readily bring to the minds of the reader the 
 relation of these one to another, and their intensities in 
 the different parts of a decomposed sunbeam. 
 
 Fiff. 2; 
 
 Actinism, or che- 
 mical power. 
 
 Light, c 
 
 F 
 
 Heat D 
 
 The various points of the solar spectrum are represented 
 In the order in which they occur between A and B, thia 
 
It) COLORING WALLS 
 
 exhibits the limits of the Newtonian spectrum, correspond- 
 ing with Fig. 1. Sir John Herschel and Seebeck have 1 
 Shown that there exists j beyond the violet, a faint violet 
 light, or rathef a lavender 'j to b, which gradually becomes 
 colorless ; similarly, red light exists beyond the assigned 
 limits of the fed ray to a. The greatest amount of actinic 1 
 power is shown at E opposite the violet 5 hence this color 
 Ci exerts*' the greatest amount of influence in the forma- 
 tion of the photographic image. 
 
 (Blue paper and blue color have been somewhat exten- 
 sively used by our operators in their operating rooms and 
 skylights, in order to facilitate the operation in the cameraj 
 I fancy, however, that this plan cannot be productive 
 bf as much gdod as thought by some, from the fact, that 
 the light falling upon the subject, and then reflected into 
 the camefa, is, coming through colorless glass, not 
 affected by such rays as may be reflected from the walla 
 bf the operating room j and even if it were so, I conceive 
 that it would be injurious, by destroying the harmony of 
 shadows which might otherwise occur.) The greatest 
 amount of white light is at G ; the yellow contains less of 5 
 the chemical power than any Other portion of the solaf 
 Spectrum. It has been found that the most intense heat 
 is at the Extreme Red, b. 
 
 Artificial lights differ in their color; the White light of 
 turning charcoal, which is the principal light from candles^ 
 bil and gas, contains three fays red, yellow and blue. The 
 dazzling light emitted from lime intensely heated, known 
 as the Drummond light, gives the color of the prism almost 
 as bright as th solar spectrum; 
 
 If we expose a prepared collodionized plate or sensitive 
 paper to the solar spectrum, it will be observed that th 
 
LIGHT, HEAT, AND CHEMICAL POWER, 
 
 17 
 
 luminous power (the yellow) occupies but a small space 
 compared with the influence of heat and chemical power. 
 R. Hunt, in his Researches on Light, has presented the fol- 
 lowing remarks upon the accompanying illustration : 
 Fiff. 3. 
 
 " If the linear measure, or the diameter of a circle which 
 shall include the luminous rays, is 25, that of the calorific 
 spectrum will be 42'10, and of the chemical spectrum 55- 10. 
 Such a series of circles may well be used to represent a 
 beam from the sun, which may be regarded as an atom of 
 Light surrounded with an invisible atmosphere of Heat, and 
 another still more extended, which possesses the remark- 
 able property of producing chemical and molecular change. 
 
 A ray of light, in passing obliquely through any me- 
 dium of uniform density, does not change its course ; but 
 
18 REFRACTION. 
 
 if it should pass into a denser body, it would turn from a 
 straight line, pursue a less oblique direction, and in a line 
 nearer to a perpendicular to the surface of thatbody. Water 
 exerts a stronger refracting power than air; and if a 
 ray of light fall upon a body of this fluid its course is 
 changed, as may be seen by reference to Fig. 4. It is 
 Fig. 4. 
 
 observed that it proceeds in a less oblique direction (to- 
 wards the dotted line), and, on passing on through, leaves 
 the liquid, proceeding in a line parallel to that which it 
 entered. It should be observed, that at the surface of 
 bodies the refractive power is exerted, r and that the light 
 proceeds in a straight line until leaving the body. The 
 refraction is more or less, and in all cases in proportion as 
 the rays fall more or less obliquely on the refracting sur- 
 face. It is this law of optics which has given rise to the 
 lenses in our camera tubes, by which means we are enabled 
 to secure a well-delineated representation of any object 
 we choose to picture. 
 
 When a ray of light passes from one medium to another, 
 and through that into the first again, if the tAvo refractions 
 be equal, and in opposite directions, no sensible effect will 
 be produced. 
 
 The reader may readily comprehend the phenomena of 
 
REFRACTION, LENSES, FOCUS. 
 
 19 
 
 refraction, by means of light passing through lenses of dif- 
 ferent curves, by reference to the following diagrams : 
 Fig. 5. Fig 6. Fig. 7. 
 
 Fig. 5 representing a double-convex lens, Fig. 6 a double- 
 concave, and Fig. 7 a concavo-convex or meniscus. By 
 these it is seen that a double-convex lens tends to con- 
 dense the rays of light to a focus, a double-concave to 
 scatter them, and a concavo-convex combines both powers. 
 If parallel rays of light fall upon a double-convex lens, 
 D D, Fig. 8, they will be refracted (excepting such as pass 
 directly through the centre) to a point termed the princi- 
 
 C D 
 
 A 
 
 Fig. 8. 
 
 B D 
 
 pal focus. The lines ABC represent parallel rays which 
 pass through the lens D D, and meet at F ; this point being 
 the principal focus, its distance from the lens is called the 
 focal length. Those rays of light which are traversing a 
 parallel course, when they enter the lens are brought to a 
 focus nearer the lens than others. Hence the difficulty 
 the operator sometimes experiences by not being able to 
 
20 
 
 ENLARGING OR REDUCING IN" COPYING. 
 
 " obtain a focus," when he wishes to secure a picture of 
 some very distant objects ; he does not get his ground 
 glass near enough to the lenses. Again, the rays from an 
 object nearby may be termed diverging rays. This will 
 be better comprehended by reference to Fig. 9, where it 
 
 -B 
 
 will be seen that the dotted lines, representing parallel 
 rays meet nearer the lenses than those from the point A. 
 The closer the object is to the lenses, the greater wil Ibe 
 the divergence. This rule is applicable to copying, Did 
 we wish to copy a ^ size daguerreotype on a -^ size 
 plate, we would place it in such a position to the lenses 
 at A, that the focus would be at F, where the image 
 would be represented at about the proper size. Now, if 
 we should wish to copy the -J- size picture, and produce 
 another of exactly the same dimensions, we have only to 
 bring it nearer to the lenses, so that the lens D E shall be 
 equi-distant from the picture and the focus, i. e* from A to 
 B. The reason of this is, that the distance of the picture 
 from the lens, in the last copy, is less than the other, and 
 the divergence has increased, throwing the focus further 
 from the lens. 
 
 These remarks have been introduced here as being im- 
 portant for those who may not understand the principles 
 of enlarging or reducing pictures in copying. 
 
i, I:\SES. 21 
 
 I would remark that the points F and A, in Fig. 9, are 
 termed " conjugate foci." 
 
 If we hold a double-convex lens opposite any object, 
 we find that an inverted image of that object will be 
 formed on a paper held behind it. To illustrate this more 
 clearly, I will refer to the following wood-cut : 
 Fig. 10. 
 
 
 
 " If A B C is an object placed before a convex lens, 
 L L, every point of it will send forth rays in all direc- 
 tions ; but, for the sake of simplicity, suppose only three 
 points to give out rays, one at the top, one at the middle, 
 and one at the bottom ; the whole of the rays then that 
 proceed from the* point A, and fall on the lens L L, will 
 be refracted and form an image somewhere on the line 
 A Gr E, which is drawn direct through the centre of the 
 lens ; consequently the focus E, produced by the conver- 
 gence of the rays proceeding from A, must form an image 
 of A, only in a different relative position ; the middle 
 point of C, being in a direct line with the axis of the lens, 
 will have its image formed on the axis F, and the rays 
 proceeding from the point B will form an image at D ; so 
 that by imagining luminous objects to be made up of an 
 infinite number of radiating points, and the rays from each 
 
SPHERICAL ABERRATION. 
 
 individual point, although falling on the whole surface of 
 the lens, to converge again and form a focus or represen- 
 tation of that point from which the rays first emerged, it 
 will be very easy to comprehend how images are formed, 
 and the cause of those images being reversed. 
 
 " It must also be evident, that in the two triangles 
 AGE and D G E, that E D, the length of the image, 
 must be to A B, the length of the object, as G D, the dis- 
 tance of the image, is to G B, the distance of the object 
 from the lens." 
 
 It will be observed, that in the last cut the image pro- 
 duced by the lens is curved. Now, it would be impos- 
 sible to produce a well-defined image from the centre to 
 the edge upon a plain surface ; the outer edges would 
 be misty, indistinct, or crayon-like. The centre of the 
 image might be represented clear and sharp on the ground 
 glass, yet this would be far from the case in regard to the 
 outer portions. This is called spherical aberration, and to 
 it is due the want of distinctness which is frequently 
 noticed around the edges of pictures taken in the camera. 
 To secure a camera with a flat, sharp field, should be the 
 object of every Operator ; and, in a measure, this consti- 
 tutes the great difference in cameras manufactured in this 
 country. 
 
 Spherical aberration is overcome by proper care in the 
 formation of the lens : " It can be shown upon mathe- 
 matical data that a lens similar to that given in the fol- 
 lowing diagram one surface of which is a section of an 
 elipse, and the other of a circle struck from the furthest 
 of the two foci of that elipse produces no aberration. 
 
 "At the earliest period of the employment of the camera 
 obscura,a double-convex lens was used to produce the image ; 
 
CHROMATIC ABERRATION. 
 
 23 
 
 but this form was soon abandoned, on account of the sphe- 
 rical aberration so caused. Lenses for the photographic 
 Fiff. 11. 
 
 camera are now always ground of a concavo-convex form, 
 or meniscus, which corresponds more nearly to the accom- 
 panying diagram." 
 
 Chromatic Aberration is another difficulty that opticians 
 have to contend with in the manufacturing of lenses. It will 
 be remembered, that in a former page (14) a beam of 
 light is decomposed by passing through a glass prism giv- 
 ing seven distinct colors red, orange, yellow, green, blue, 
 indigo and violet. 
 
 Now, as has been said before, the dissimilar rays having an 
 unequal degree of refrangibility, it will be impossible to ob- 
 tain a focus by the light passing through a double-convex 
 lens without its being fringed with color. Its effect will be 
 
 Fig. 12 
 R ' L M 
 
 readily understood by reference to the accompanying cut. 
 If L L be a double convex-lens, and R R R parallel rays 
 
24 CHROMATIC ABERRATION. 
 
 of white light, composed of the seven colored rays, each 
 having a different index of refraction, they cannot be 
 refracted to one and the same point ; the red rays, being 
 the least refrangible, will be bent to r, and the violet rays, 
 being the most refrangible, to v : the distance v r consti- 
 tutes the chromatic aberration, and the circle, of which the 
 diameter is a /, the place or point of mean refraction, and 
 is called the circle of least aberration. If the rays of the 
 sun are refracted by means of a lens, and the image re- 
 ceived on ft screen placed between C and o, so as to cut 
 the cone L a I L, a luminous circle will be formed on the 
 paper, only surrounded by a red border, because it is pro- 
 duced by a section of the cone L a I L, of which the exter- 
 nal rays L a L /, are red ; if the screen be moved to the 
 other side of o, the luminous circle will be bordered with 
 violet, because it will be a section of the cone M a M /, of 
 which the exterior rays are violet. To avoid the influence 
 of spherical aberration, and to render the phenomena of 
 coloration more evident, let an opaque disc be placed over 
 the central portion of the lens, so as to allow the rays only 
 to pass which are at the edge of the glass ; a violet image 
 of the sun will then be seen at v, red at r, and, finally, 
 images of all the colors of the spectrum in the interme- 
 diate space ; consequently, the general image will not 
 only be confused, but clothed with prismatic colors." 
 
 To overcome the difficulty arising from the chromatic 
 aberration, the optician has only to employ a combination 
 of lenses of opposite focal length, and cut from glass possess- 
 ing different refrangible powers, so that the rays of light 
 passing through the one are strongly refracted, and in 
 the other are bent asunder again, reproducing white light. 
 
 To the photographer one of the most important features, 
 
f'MKOMATIC AHK1M5ATIOY. 25 
 
 requiring his particular attention, is, that lie be provided 
 with a good lens. By the remarks given in the preceding 
 pages, he will be enabled, in a measure, to judge of some 
 of the difficulties to which he is occasionally subjected. 
 We have in this country but two or three individuals who 
 are giving their attention to the manufacture of lenses, 
 and their construction is such, that they are quite free 
 from the spherical or chromatic aberration. 
 
CHAPTER II. 
 
 CAMERA ARRANGEMENT OF LENSES CAMERA TUBES CA- 
 MERA-BOXES, BELLOWS, AND COPYING CAMERA STANDS 
 
 HEAD RESTS CLEANING VICE NITRATE BATH LEVELING 
 
 STANDS PRINTING FRAMES COLLODION VIALS. 
 
 BABTISTA PORTA, when he saw for the first time, on the 
 walls of his dark chamber, the images of external nature, 
 pictured by a sunbeam which found its way through only 
 a small hole, little thought of the importance which would 
 be attached to the instrument he was, from this cause, led 
 to invent. The camera obscura of this Italian philosopher 
 remained as a mere scientific toy for years, and it was not 
 until Daguerre's discovery that its true value was es- 
 timated. It now plays a very important part in giving 
 employment to at least ten thousand persons in this coun- 
 try alone. 
 
 It is of the utmost importance, in selecting a set of ap- 
 paratus, to secure a good camera ; for without such no one 
 can obtain fine pictures. In testing it, see that it gives 
 the pupil of the eye and lineaments of the features sharp 
 and distinct ; and that the whole image on the ground 
 glass has a fine pearly hue. Look also to the field, and 
 observe that the focus is good at the centre and extreme 
 edges of the ground glass at the same time. A poor ca- 
 mera generally gives a misty image, with the lights and 
 shades apparently running together. The best American 
 
CAMERA TUBES AND LENSES. 27 
 
 cameras are fully equal to those imported, while they cost 
 much less ; but there are great numbers sold which are 
 not worth using. 
 
 If a lens gives a well denned image on the ground glass, 
 it should do the same on the plate. Many a valuable lens 
 has been condemned for failing in this, merely in conse- 
 quence of the plate-holder not being in focus with the 
 ground-glass. In case of deficiency in this, put a glass 
 into the holder, lay a rule across the face, and measure the 
 distance between them very exactly ; measure the ground- 
 glass in the same way, and make the distance agree per- 
 fectly, by moving the ground-glass either back or forward 
 in the frame, as the case may be, so that the surface of the 
 glass plate shall occupy precisely the same position as the 
 face of the ground-glass when in the camera. 
 
 It is very desirable that the operator should under- 
 stand the arrangement of the lenses in the tube ; it not un- 
 frequently happens, that in taking out the " glasses" to 
 clean them, he does not return them to their proper places, 
 and the result is that his " camera is spoiled." A couple of 
 illustrations and a few remarks will be sufficient to enable 
 any one to replace the lenses in them properly. Fig. 13 
 
 Fig. 14 
 
 represents the tube for holding the lens, and Fig. 14 
 shows their arrangement. It will be seen that the two 
 
POSITION OF LENSES IN THE TUBE. 
 
 back lenses have a small space between them ; this sepa 
 ration is kept by a small tube or ring of the same circum- 
 ference as the lens. The two front lenses are nearest to- 
 gether. It will be observed that the two thick lenses are 
 towards each other ; these are made of flint glass contain- 
 ing much oxide of lead. The other two are double convex, 
 and are made of crown glass. By noting the fact that the 
 two cemented lenses go in the front of the tube, the 
 glass having the thickest edge goes inside, and that the 
 thickest lens of the other two goes in first, from the back of 
 the tube, it will not be easy for the operator to make a 
 mistake in returning the " glasses." 
 
 " I will remark that a diaphragm diminishes both chroma- 
 tic and spherical aberration, by cutting off the outside 
 portion of the lens. It lessens the brilliancy of the image, 
 but improves the distinctness by preventing various rays 
 from interfering with and confusing each other ; it also 
 causes a variety of objects at different distances to be in 
 focus at the same time." 
 
 The tube containing the lenses is to be mounted on a box 
 (camera-box) as in Fig. 15. For this purpose there are 
 
 Fig. 15. 
 
 several patterns of boxes, from among which I have made 
 
CAMERA BOXES. 
 
 29 
 
 two selections of the most approved, and represent them 
 by cuts, Figs. 16, 17, 18. [Fig. 16.] 
 
 Figs. 16 and 17 represent a bellows-box which is proba- 
 bly more in use than all the other patterns together. They 
 serve both for copying and taking portraits from life. A is 
 Fig. 17. 
 
 the base ; B is the back and sliding-box. ; C, bellows, which 
 admits of extension or contraction ; D is the opening to re- 
 ceive the carriage A, Fig. 17 ; E is a thumb screw to hold the 
 sliding-box at any required distance. Fig. 17 rep resents the 
 plate-holder and ground glass frame. 
 
 A, carriage to pass through D, Fig. 16 ; B, frame for 
 ground-glass, which may be turned in a horizontal or per- 
 pendicular position ; C, a movable plate-holder held in place 
 by means of springs ; D, reducing holder, with bottom and 
 plate to hold the glass plate : any size of reducing frame 
 can be put in frame C ; E E, spring bottom to keep frame 
 
30 
 
 CAMERA BOXES. 
 
 D in place ; F, slide ; G, thumb-screw, when the carriage 
 is to "be put in or taken out of the box, Fig 16 ; H H, 
 spring bottom to hold B in place. 
 
 Bellows-boxes can be obtained which receive the plate- 
 holder from the top, the same as in the copying-box, 
 Figs. 15 and 18. The common wood, or" copying-box," is 
 represented by Fig. 18. 
 
 Fig 18. 
 
 A, being the main or outside box, is made of wood veneered 
 with rosewood ; B is another box which fits into A, slid- 
 ing in and out as required. The ground glass and plate- 
 holders fit grooves made in the inside box. 
 
 In regard to plate-holders or tablets for holding the glass 
 plates, it need only be said that the camera-boxes are ac- 
 companied with a complete set, so arranged that the light 
 is wholly excluded from the plate while drawing out or 
 pushing in the slide, for shutting off the light while the 
 holder is out of the box. Should any one be desirous of 
 using the same camera, for taking both glass and daguer- 
 reotype pictures, it will be necessary for him to be pro- 
 vided with two sets of tablets for his box, one for each 
 process. 
 
CAMERA STANDS. 
 
 31 
 
 CAMERA STANDS. 
 
 There are several patterns of these ; almost every 
 dealer has some particular style, which, if not for beauty, 
 for his interest, suits his purposes best. Among the assort- 
 ment, I will present only two illustrations. The first, Fig. 
 19, represents one which has an advantage over many 
 others ; it is made of cast iron, and of an ornamental pat- 
 
 Fiff. 19. 
 
 tern : A, base on castors ; B, fluted hollow column, which 
 admits the iron tube C, which has on one side a hollow 
 tooth rack to receive a spiral thread on the inner face of 
 wheel D ; this wheel, when turned, elevates or lowers the 
 
32 CAMERA STANDS, ARM STANDS. 
 
 tube C to any desired height ; E, thumb wheel attached 
 to a screw which sets against tube C, to hold it in posi- 
 tion, F, a pinion by which the camera can be directed ; 
 G G, thumb screws to hold the two plates together when 
 in position. It is quite heavy, stands firm and solid, and 
 is not liable to be moved by the jar from walking over 
 the floor. For permanently located operators these are 
 the most desirable ; but for those who are moving about 
 from place to place, and those who wish to take views, a 
 Fig. 21. Fig. 20. 
 
 lighter article would be more convenient, such as one 
 represented at Fig. 20. This stand is made principally of 
 wood, and can be readily taken apart, so as to be packed 
 in an ordinary sized trunk. 
 
 Fig. 21 represents a small " Jenny Lind stand," and is 
 
UESiS, 
 
 & very Convenient article for the sitter to lean a hand or 
 arm upon while sitting for a portrait; It is fixed with a 
 rod for raising or lowering the top, and can be adjusted to 
 any required height. 
 
 HEAD RESTS* 
 
 There are several patterns of head supports, 6r, ad 
 they are cdmmonly called, head rests, in use by the pro- 
 fession. I give two illustrations (Figs. 22 and 23). The 
 
 Fig. 23. Fig, 23, 
 
 first is an independent iron rest, known as the " Jenny 
 Land Rest ;* and the other is for fastening to the back of a 
 chair, as seen in the cut. For general use, I would r'ecom* 
 mend the iron independent rest as far more advisable than 
 any other, 
 
 VICES FOR HOLDING GLASS. 
 
 The article used for holding the glass, during the pro* 
 cess of cleaning, is called a vice ; and, of the numerous 
 
PLATE-HOLDERS, BATH, DIPPING 
 
 styles recently introduced, I find none that I would prefei? 
 to the old one known in market as " Peck's Vice ;*' it is 
 simple and easy in operation, and at the same time is 
 effectual. Fig. 24 represents this vice, which is to be 
 Fig. 24, 
 
 firmly secured to a bench ; the small piece df wood at- 
 tached to the bottom is of ho use. A A are the grooves 
 for receiving the daguerreotype plate-block ; but as they 
 are too deep for the glass, I pin on a small strip of wood^ 
 BO that the upper edge of the glass will be a little above! 
 the projection of the vice. 
 
 NITRATE BATHS AND DIPPING 
 The accompanying illustration, Fig. 25, a, represents 
 Ficr. 25. Fig. 26. Fig. 27. 
 
 a b 
 
 bath for holding the nitrate of silver solution. 
 
shape is of my own suggestion, and the best adapted 
 to the wants of the photographer. It will be seen that the 
 front side is rounding, with a curve extending from side to 
 side. By this shape, the face of the glass is! protected from 
 coming in contact with the side of the bath both edges 
 of it turning so as to prevent injury. There is a small 
 projection on the top, at the opposite side of the oval j 
 this is to allow the solution to flow over and wash ofl any 
 dust that may have gathered upon the surface of the solu- 
 tion. This wash runs out of a small tube, as is shown in 
 the cut. Any convenient vessel can be placed under it to 
 receive the liquid. This can be filtered and returned as 
 often as required. I am not in the practice of filling my 
 baths full of solution, but always keep them filtered and 
 clean ; hence saving an excess of solution. 
 
 b represents a little support, which is secured at its base 
 upon the shelf, to hold the bath in a slightly inclined posi- 
 tion, which is preferable to having it stand perpendicularly. 
 
 LEVELING STANDS. 
 
 Persons oftentimes require a rest or place to put their' 
 Fig. 28. Fig. 20. Fig. 30. 
 
 glass during development or washing the picture. Eithef 
 
I'RiNTiNG 
 
 of the stands represented by the annexed cut will &nswei 
 the purpose. 
 
 Fig. 30 is known to the daguerreotype operator as 
 " gilding stand,*' and is the one best adapted to the wants 
 of operators on glass. It may be so arranged as to give 
 the surface of the glass a water-level 5 D D are thumb 6 
 screws, by means of which, when properly regulated, the 
 frame C may hold glass perfectly level and a large quan* 
 lity of solution may be poured over the surface, 
 
 PRINTING FRAMES. 
 
 'There are numerous methods and apparatus used for 
 holding the negitive and the paper during exposure to the 
 light. The following illustrations represent a convenient 
 economical frame for this purpose. 
 
 Fiff. 31. 
 
 Pig. 32, 
 
 Fig. 3l represents the front of th'e frame. The negative 
 glass is held upon it by springs attached by screws to the 
 bottom half of the frame, A, so that they can be 
 turned on or off, to suit the different sizes of glass. On 
 the other end of the spring are wooden buttons, which are 
 placed on the edges of the glass negative, holding it in its 
 place, and pressing it firmly against the paper which is 
 placed under it. This frame is made of two pieces of 
 inch board, which are connected by hinges, falling ovei* 
 
PRINTING FRAMES. 37 
 
 as seen in Fig. 32, B being the half that is movable. This 
 movable half is secured in position by means of a wooden 
 button, attached to A on the back and under B, as seen in 
 Fig. 32. The separate pieces, A and B, are bevelled where 
 they connect, as seen by Fig. 31. D (in Fig. 32) is one of 
 the springs, which can be seen in Fig. 31. 
 
 The entire bed or fece of the frame, A and B, should be 
 covered with a thick piece of satinet cloth, which may be 
 pasted to the lower half, A, and extended over the entire 
 surface of A and B. This forms a pad for the paper. 
 
 This printing frame can be easily made by any cabinet- 
 maker or carpenter. The springs may be of sheet iron or 
 brass either will be found sufficiently stiff for the purpose. 
 Every operator should be provided with from four to ten 
 frames : the saving of time will be found to amply repay 
 the expenditure necessary for a good supply. 
 
 Another article called a pressure frame, is represented in 
 Fig. 33. 
 
 the accompanying figure. This is more expensive than 
 the first, and is by some considered preferable. 
 
 Another cheap, convenient and equally good arrange- 
 ment for holding the negative and paper, is to take three 
 glasses say one a full size, being the one having the nega- 
 tive upon it ; and then take two glasses, each just half the 
 size of the negative, and have a piece of very thick heavy 
 cloth cut the size of the negative glass, which can be put be- 
 tween it and the two half glasses, and then they can be 
 held together by means of the common spring clothes pin. 
 
 3 
 
38 
 
 COLLODION VIALS. COLOR BOXES. 
 
 The advantage of the two glasses at the back is, that one 
 can be entirely removed while the picture is being ex- 
 amined, and afterwards returned without, in the least, 
 moving the impression. 
 
 COLLODION VIAL. COLOR BOXES. 
 
 This shaped vial is made expressly for collodion, to 
 which purpose it is admirably adapted. It has a wide 
 
 Fig. 34. Fig, 35. 
 
 Ft 
 
 mouth, and is so constructed that the liquid flows clear 
 and free. It is deep, and with a heavy protruding base, 
 to prevent its falling. There are two sizes made at pre- 
 sent, one to contain 2Jr ounces the other, 1J ounce. I 
 generally use the smaller ones, but always keep on hand, 
 and would not be without, a few of the larger size. 
 
 Fig. 35 represents a color-box. These can be had of any 
 dealer, completely fitted, with color and brushes for use. 
 
CHEMISTRY. 
 
 PRACTICAL HINTS 
 
 ON 
 
 PHOTOGEAPHIC CHEMISTRY, 
 
CHAPTER III. 
 
 SOLUBLE COTTON MANIPULATION PLAIN COLLODION 
 
 BROMO-IODIZED COLLODION FOR POSITIVES DITTO FOR 
 
 NEGATIVES SOLUTION OF BROMIDE AND IODIDE OF POTAS- 
 SIUM AND SILVER DOUBLE IODIDE OF POTASSIUM AND SIL- 
 VER DEVELOPING SOLUTION FIXING THE SOLUTION 
 
 BRIGHTENING AND FINISHING THE IMAGE PHOTOGRAPHIC 
 
 CHEMICALS. 
 
 The chemistry of Photography requires the attention, 
 in a greater or less degree, of every practitioner. It is of 
 the utmost importance, that those who wish to meet with 
 success in the various processes given, should not only be 
 provided with a good selection of chemicals, but also un- 
 derstand the nature of the agent employed. To give a 
 perfectly complete and full list of every agent used would 
 require more time and space than can be given in this 
 work. I shall confine myself to some of the most impor- 
 tant, and to such articles as are of the greatest interest to 
 the practitioner. 
 
 SOLUBLE COTTON. 
 
 I have, in my practice and trade, adopted the term solu- 
 ble cotton as the one most appropriate, making a desirable 
 distinction from the article sold as. gun cotton, they being 
 of a somewhat different nature gun cotton being the 
 most explosive and least soluble, while the other prepara- 
 tion is more soluble and less explosive. 
 
42 SOLUBLE COTTON. 
 
 There^are two methods employed in the preparation of 
 soluble cotton ; one being by the use of nitric and sulphu- 
 ric acids, and the other with sulphuric acid and nitrate of 
 potash. The last of these I would recommend as being 
 the most convenient for those who require only a small 
 quantity of cotton. Persons experimenting in the prepa- 
 ration of this article should exercise much care and judg- 
 ment. A good cotton is not the result of hap-hazard ope- 
 ration. The operator should be acquainted, as nearly as 
 possible, with the quality of the chemicals employed, and 
 the proper mode of manipulation. 
 
 Articles necessary. One quart "Wedgewood mortar and 
 pestle, or evaporating dish ; one glass rod ; one pane of 
 glass, large enough to cover the mortar or dish ; one ordi- 
 nary-sized pail two-thirds full of pure rain or distilled 
 water, and at least ten times that quantity of water at 
 hand ; twelve ounces (by weight, avoirdupois) of nitrate 
 of potash (Dupont's refined, pulverized) ; twelve ounces 
 (by measure) of commercial sulphuric acid ; and three 
 hundred and forty grains of clean, pure cotton wool. 
 
 Remarks. It is advisable that the mortar or dish be 
 deep and narrow, as the mixture can be better formed in 
 a vessel of this shape. If not convenient to procure a 
 mortar, a common earthen bowl will answer ; glass is ob- 
 jectionable, as the heat generated in the combination of 
 the acid and nitre is liable to crack it. A new pail should 
 not be used, especially if it is painted, as the acids attack 
 the paint, and injure the cotton. I prefer one that has 
 been used for some time, and has been frequently cleaned. 
 A common earthen wash-bowl, or any large glass dish, 
 will answer in place of the pail. Metal pails or vessels 
 should not be used. 
 
SOLUBLE COTTON. 43 
 
 Nitrate of Potash (saltpetre) should be dry and finely 
 powdered. I use none other than Dupont's refined ; this 
 is very nearly, if not absolutely, chemically pure. 
 
 The commercial Sulphuric Acid (oil of vitriol) of Ame- 
 rica is of great uniformity of strength, as sold by drug- 
 gists generally. I use a test-bulb graduated to the proper 
 density, and have been very successful in my experiments. 
 
 In some twenty different samples of acid, used in differ- 
 ent cities in the United States, I found only one that pro- 
 duced a poor cotton, and this might have been influenced 
 by the moisture of the atmosphere, it being a very rainy 
 day when I used it. 
 
 During my recent and somewhat extensive practice, I 
 have thought that the fine long fibres of cotton wool do not 
 make so desirable a soluble cotton as that which is heavy 
 or common. Four or five very careful experiments upon 
 this point, have had the effect to produce in me a strong- 
 belief that my ideas are entitled to some consideration. 
 I should not select the finest cotton for making solu- 
 ble cotton, but now invariably take that which is thick or 
 coarse. 
 
 The result of my experience is (other things being 
 equal), that cotton prepared in fine dry weather has a 
 greater degree of solubility than when prepared in a moist 
 atmosphere : hence I would recommend the experimenter 
 to choose fine, clear weather for preparing it. 
 
 Manipulation. 
 
 Having at hand every article requisite, proceed as fol- 
 lows : Put the nitrate of potash into the mortar or dish ; 
 be sure it is dry and well powdered, and then add the 
 acid ; stir them well with the pestle and glass rod, so that 
 
44 SOLUBLE COTTON. 
 
 the lumps will be all (or nearly so) out, and a pasty solu- 
 tion formed. This operation should not occupy more than 
 two minutes' time. Then put in the cotton, about one- 
 quarter of the whole bulk at a time : it should be well 
 picked apart, so that it may come immediately in contact 
 with the acids, and should be kneaded, with the pestle and 
 glass rod, into the solution, and as soon as wetted, another 
 quarter should be added and wetted as soon as possible ; 
 so continue until all is in : then knead with the pestle and 
 mortar for at least four minutes, or until every fibre of the 
 cotton is saturated with the liquid ; then the mortar should 
 be covered over with the pane of glass, and allowed to 
 stand for fifteen or twenty minutes ; then the entire con- 
 tents of the mortar should be thrown into the pail two- 
 thirds full of water, and stirred with the glass rod as ra- 
 pidly as possible : if this rapid stirring is omitted, the cot- 
 ton will be injured by the action of the acids in combining 
 with the water. The water should be poured off, and 
 another change put into the pail. 
 
 After about three changes, the hands maybe used in the 
 farther washing. The hands should be perfectly clean, 
 and free from all chemicals. The changes of water and 
 washing should be continued until every trace of acid has 
 disappeared, which can be seen by testing with blue lit- 
 mus test-paper. After it is thought that the cotton has 
 become free, the water may be squeezed out of a little 
 lump about the size of a pea, and then placed between 
 the fold of the test-paper, and if it reddens the paper, 
 there is acid present, and the washing should be continued 
 until there is no change in the paper. When this is done, 
 the cotton can be put into the folds of a dry towel or cloth 
 (which has been thoroughly rinsed, so that no soap be pre- 
 sent), and wrung out as dry as possible, and then it may 
 
SOLUBLE COTTON. 45 
 
 be picked apart and put aside, exposed to a moderate tem- 
 perature (say 100 Fah.) to dry, when it is ready for use. 
 
 I employ the method (for convenience, nothing more) 
 of displacing the water by the use of alcohol. [Cutting's 
 patent see patents.] I wring out the water as before, 
 then place the cotton in strong alcohol, stir and press it, 
 and then pour it off; wring it out again, then put it in a 
 change of alcohol, let it soak for about five minutes, then 
 wring it out as dry as possible, pick it apart, and it will dry 
 immediately, and place it in a close stoppered bottle ; or, 
 if wanted for use at once, put it into the dissolving solu- 
 tion immediately. 
 
 I will here remark that, since the first edition, I have 
 had occasion to use large quantities of soluble cotton, and 
 have found that if it be kept in an atmosphere of alco- 
 hol and ether, its solubility is somewhat improved : that 
 is, in the case of its not being used immediately after its 
 preparation. This is easily kept, by dropping a few drops 
 of ether or alcohol into the bottle containing it, and then 
 sealing close until wanted for use. In the event of the 
 water being displaced by alcohol, it is not necessary to tho- 
 roughly dry it, but put in a perfectly close bottle to keep. 
 
 Remarks. There are a few precautions necessary to be 
 observed in the preparation of soluble cotton. I should 
 select a fine clear day, if time is no object ; nevertheless I 
 have made a good article in a moderately dense atmos- 
 phere. Sulphuric acid has a powerful affinity for hydro- 
 gen, consequently, in damp weather, it is more or less re- 
 duced by the moisture in the air. 
 
 It is advisable to prepare the nitro-sulphuric acid mix- 
 ture on a roof, or between two doors or windows, where 
 there is a good current of air, in order to prevent the 
 inhalation of white vapors which arise, and are very poi- 
 
46 SOLUBLE COTTON. 
 
 sonous to the lungs. As a preventive, in case of inhal- 
 ing these vapors, I apply the fumes of aqua-ammonia. It 
 is best for every one to have six or eight ounces of this al- 
 ways at hand ; it neutralizes all acid that may be spattered 
 on the clothes, prevents its destructive powers, and 
 restores the color. 
 
 Yellow vapors sometimes appear when putting the cot- 
 ton in contact with the solution : this arises from its not 
 being wet ; and when they do appear, the cotton where 
 they are should be quickly put under the liquid and 
 kneaded rapidly, which will prevent a continuance of these 
 vapors. I have had them appear, and used the cotton, and 
 could not observe that any bad effect had been produced. 
 
 The temperature is worthy the attention of the operator : 
 if it be low, as in winter, and the cotton be left in the 
 nitro-sulphuric mixture for fifteen or twenty minutes, the 
 whole becomes a thick, stiff mass, bedded together, and 
 has not had proper action, giving a bad article. A good 
 temperature is about 140 Fah. for the last of the time the 
 cotton is in the mixture. This is not always convenient ; so 
 the operator will be governed by circumstances, taking 
 his chance of having a good article. In some cases I have 
 heated a thick iron plate, at a moderate temperature, plac- 
 ing the mortar upon it, and thus aided in regulating the 
 temperature. This is the most convenient method I have 
 employed. 
 
 It has been thought advisable to publish in full the 
 account of Edw. Ash Hadow's experiments and investiga- 
 tions upon the subject of soluble cotton. The following 
 is an account of them as it appeared in Humphrey's Jour- 
 nal, vol. VI. p. 12: 
 
 " Having, in my earlier experiments on the collodion pro- 
 
SOLUBLE COTTON. 47 
 
 cess of photography, experienced some difficulty in always 
 producing a collodion of uniform quality with regard to 
 sensitiveness, tenacity and fluidity, although making use of 
 the same materials for its preparation, and this I find being 
 the complaint of many others, it has been my study lately 
 to determine the variations in quality to which the ingre- 
 dients are liable, ancl the effects of these variations 011 the 
 sensitive film, and likewise to ascertain whether the excel- 
 lent qualities of some samples of collodion depend on the 
 materials in ordinary use, or on some substances acciden- 
 tally or intentionally added. Researches in the prepara- 
 tion of collodion may appear superfluous, now that it is 
 supplied of the best quality by so many makers ; but as 
 some persons of an independent turn of mind still prefer 
 manufacturing their own, I venture to bring forward the 
 subject with the hope of benefiting them. In this beauti- 
 ful process so much depends for success on the quality of 
 the collodion, that when in possession of a good specimen, 
 it becomes one of the easiest and most simple, and ought 
 to be the most certain of all the processes yet devised ; 
 for here no material of uncertain composition is intro- 
 duced, such as paper, and thus we have nothing to fear 
 from plaster of Paris, alumnia, or specks of iron or copper, 
 which continually endanger or modify the calotype pro- 
 cess ; each ingredient can and ought to be obtained in a 
 state of perfect purity, and with this precaution the de- 
 gree of success depends upon the skill of the operator 
 himself. 
 
 Of all the substances used in this process, the gun- 
 cotton is usually the only one actually prepared by the ope 
 rator himself; in this he cannot fail to have observed the 
 great variations in the solubility, and, when dissolved, the 
 
SOLUBLE COTTON. 
 
 transparency and tenacity of the films, to which it is liable ; 
 the various processes also that are given appear at first 
 sight unaccountably different, some directing ten minutes, 
 others a few seconds immersion. In consequence of this 
 I have specially examined into the cause of all these vari- 
 ations, with a view to obtain certainty, and also have endea- 
 vored to discover how far they affect the sensitiveness of the 
 prepared surface. If we take a mixture of the strongest 
 nitric and sulphuric acids and immerse as much cotton 
 as can be wetted, after some minutes squeeze out 
 the acid as far as posible, then immerse a second por- 
 tion of cotton, and again express the acids for a third por- 
 tion of cotton, and so on until the liquid is exhausted, we 
 shall find, on comparing the cottons thus treated, after 
 washing and drying, that there is a gradual alteration in 
 their properties, the first being highly and perfectly ex- 
 plosive, and each succeeding portion less so, until the por- 
 tion last immersed will be found hardly explosive, leaving 
 distinct traces of charcoal or soot when burned. This may 
 not appear surprising at first sight, as it may be imagined 
 that the latter portions are only a mixture of gun-cotton 
 and common cotton ; this is, however, not the case, for if 
 each quantity be immersed sufficiently long, it will not 
 contain a fibre of common cotton, and may yet become 
 charred on burning like unaltered cotton. The most re- 
 markable difference, however, is discovered on treating 
 them with ether containing a little alcohol, when, contrary 
 to what might have been anticipated, the first or strongest 
 gun-cotton remains untouched, while the latter portions dis- 
 solve with the utmost ease, without leaving a trace behind, 
 which alone is sufficient proof that no unaltered cotton re- 
 mains. This difference in properties is owing to the gra- 
 
SOLUBLE COTTON'. 49 
 
 dual weakening of the acid mixture, in consequence of the 
 nitric acid being removed by the cotton, with which it be- 
 comes intimately combined, at the same time that the 
 latter gives out a proportionate quantity of water. In 
 consequence of these experiments, a great many mixtures 
 of these acids were prepared of various strengths, each 
 being accurately known, both to determine whether there 
 were more than one kind of soluble gun-cotton, and, if 
 there were, to ascertain exactly the mixture required to 
 produce the most suitable to photographic purposes. By 
 this means, and by, what I believe has not been pointed 
 out, varying the temperature, at least five varieties were ob- 
 tained ; first, gun-cotton, properly so called, as before 
 stated, quite insoluble in any mixture of alcohol and sul- 
 phuric ether. Secondly, an explosive cotton, likewise in- 
 soluble, but differing chemically from the first, obtained by 
 a mixture of certain strength when used cold. If warm, 
 however, either from the heat produced spontaneously on 
 mixing the two acids; or by raising the temperature artifi- 
 cially to about 130, the cotton then immersed becomes 
 perfectly soluble, producing a third variety ; if, however, 
 it be thoroughly dried, it becomes in a great measure in- 
 soluble. The fourth is obtained by the use of weaker acids 
 used cold, and the fifth when the mixture has been warmed 
 to 130 previous to the immersion of the cotton ; in either 
 of the two last cases the product is perfectly soluble, but 
 there is a remarkable difference between their properties, 
 for on dissolving 6 grains of each in 1 ounce of ether, the 
 cotton treated with warm acids gives a perfectly fluid so- 
 lution (which is likewise the case with the third variety 
 produced by acids something stronger), while that obtained 
 by the use of cold acids makes a mixture as thick as cas- 
 tor-oil. 
 
50 SOLUBLE COTTON. 
 
 " Having obtained these more strongly marked varieties, 
 as well as intermediate kinds, with all gradations of solu- 
 bility, it was necessary, before I could select any particu- 
 lar formula for preparing the cotton, to compare their pho- 
 tographic properties, with especial reference to sensitive- 
 ness, opacity of the reduced silver in negatives, and its 
 color in positives. A certain weight of each being dis- 
 solved in a portion of the same mixture of alcohol and 
 ether previously iodized, the comparison was made, by 
 taking the same objects with each collodion in succession, 
 and likewise by pouring two samples on the same plate of 
 glass, and thus exposing them in the camera together, side 
 by side ; this last proved to be much the most satisfactory 
 plan, and was repeated many times for each sample, tak- 
 ing care to reverse the order in which they were poured 
 on, that there might be no mistake arising from the differ- 
 ence of time elapsing between the pouring on of the col- 
 lodion and its immersion in the sensitive bath. By these 
 experiments I had confidentially hoped to have solved the 
 question as to the cause of difference in sensitiveness and 
 other photographic properties of collodion ; but in this I 
 was disappointed, for, after repeated experiments, I believe 
 I may safely affirm that they are precisely similar as re- 
 gards their photographic properties. The same I believe 
 may be said of Swedish paper collodion, judging from a 
 few comparative experiments I have made, and indeed it 
 is difficult to discover what is the superiority of this mate- 
 rial over clean cotton-wool ; the ease of manipulation 
 which some allege is a matter of taste, but I should deci- 
 dedly prefer the open texture of cotton to that of a sub- 
 stance like filtering paper, composed of a mass of com- 
 pacted fibres, the innermost of which are only reached 
 
SOLUBLE COTTON. 51 
 
 when the acids have undergone a certain degree of weak- 
 ening by the water abstracted from the outer fibres ; and 
 when we consider that from cotton alone we have the 
 means of preparing all varieties of collodion, from the most 
 powerfully contracting and transparent to the weakest and 
 most opaque, and each if required with equal and perfect 
 certainty, there appears to be choice enough without resort- 
 ing to another material, differing only in being more rare 
 and more difficult to procure. But, although the photo- 
 graphic properties of these varieties of collodion-wool are 
 so similar, other circumstances, such as fluidity, tenacity, 
 and transparency, render its preparation of some impor- 
 tance, and indicate that the acid mixture should always 
 be used warm ; and it is chiefly in consequence of this very 
 circumstance, that greater success attends the use of nitrate 
 of potash and sulphuric acid than that of mixed acids ; for 
 the former when mixed, produce the required temperature, 
 and MUST be used while warm, since on cooling the mix- 
 ture becomes solid, whereas acids when mixed do not 
 usually produce so high a temperature, and being fluid 
 can be used at any subsequent period ; another obstacle 
 to their use is the great uncertainty of the strength 
 of the nitric acid found in the shops, requiring a varia- 
 tion in the amount of sulphuric acid to be added, 
 which would have to be determined by calculation or 
 many troublesome trials. When a proper mixture is ob- 
 tained, the TIME of immersion is of no importance, pro- 
 vided it be not too short, and the temperature be main- 
 tained at about 120 or 130 ; ten minutes is generally 
 sufficient ; (though ten hours would not render the cotton 
 less soluble, as is sometimes asserted.) 
 
 " In using the mixed acids, the limits are the nitric acid 
 
52 SOLUBLE COTTON. 
 
 being too strong, in which case the product is insoluble, 
 or too weak, when the cotton becomes immediately matted 
 or even dissolved, if the mixture is warm. I have availed 
 myself of these facts in order to produce collodion- wool 
 by the use of acids, without the trouble of calculating 
 the proper mixture according to their strength. Five 
 parts by measure of sulphuric acid, and four of nitric acid 
 of specific gravity not lower than 1*4, are mixed in an 
 earthenware or thin glass vessel capable of standing heat ; 
 small portions of water are added gradually (by half 
 drachms at a time, supposing two ounces to have been 
 mixed,) testing after each addition by immersion of a 
 small portion of cotton ; the addition of water is continued 
 until a FRESH piece of cotton is found to contract and dis- , 
 solve on immersing ; when this takes place, add half the 
 quantity of sulphuric acid previously used, and (if the 
 temperature does not exceed 130, in which case it must 
 be allowed to cool to that point,) immerse as much cotton, 
 well pulled out, as can be easily and perfectly soaked ; it 
 is to be left in for ten minutes, taking care that the mix- 
 ture does not become cold, and then transferred to cold 
 water, and thoroughly washed ; this is a matter of much 
 importance, and should be performed at first by changing 
 the water many times, until it ceases to taste acid, and 
 then treating it with boiling rain-water until the color of 
 blue litmus remains unchanged ; the freedom from all 
 trace of acid is insured by adding a little ammonia before 
 the last washing. Cotton thus prepared should dissolve 
 perfectly and instantaneously in ether containing a little 
 alcohol, without leaving a fibre behind, and the film it pro- 
 ducts be of the greatest strength and transparency, being 
 what M. Gaudin terms * rich in gun-cotton.' 
 
SOLUBLE COTTON. PLAIN COLLODION. 53 
 
 The mixture of nitrate of potash and sulphuric acid is 
 defective chiefly from the want of fluidity, in consequence 
 of which the cotton is less perfectly acted on ; this may 
 be remedied by increasing the amount of sulphuric acid, 
 at the same time adding a little water ; a mixture of 5 
 parts of dried nitre, with 10 of sulphuric acid, by weight, 
 together with 1 of water, produces a much better collodion 
 wool than the ordinary mixture of 1 of nitre with 1^ of 
 sulphuric acid. The nitre is dried before weighing, in 
 order that its amount, as well as that of the water con- 
 tained in the mixture, may be definite in quantity ; it is 
 then finely powdered, mixed with the water, and the sul- 
 phuric acid added ; the cotton is immersed while the mix- 
 ture is hot, and afterwards washed with greater care even 
 than is required when pure acids are used, on account of 
 the difficulty of getting rid of all the bisulphate of potash 
 that adheres to the fibres, which both acts as an acid and 
 likewise causes the collodion to appear opalescent when 
 held up to the light ; whereas the solution should be per- 
 fectly transparent." 
 
 PLAIN COLLODION. 
 
 To dissolve the soluble cotton (pyroxyline), and form 
 plain collodion, proceed as follows : 
 Take of 
 
 Sulphuric ether (concentrated), 10 ounces 
 
 Alcohol, from 90 to 95 per cent, - - 6 " 
 
 Soluble cotton enough to give the solution a consistency 
 such as will allow it to flow evenly over the surface of the 
 
54 PLAIN COLLODION. 
 
 glass, and impart to it quite a thick and transparent coat- 
 ing. If the coating is opaque, the cotton has not been pro- 
 perly prepared, the acid mixture has been too weak. 
 
 Remarks. It is desirable for every operator to use che- 
 micals of uniform strength, and the better method to adopt 
 is to employ those purchased from some one respectable 
 manufactory, and not take those furnished by irresponsi- 
 ble and unconscientious parties. At least one-half of the 
 failures experienced by beginners is from want of good 
 chemicals. It is not economy to purchase a cheap article. 
 
 Alcohol is an article that can be procured in almost any 
 small village in the United States, and is in general fit for 
 collodion purposes. I have used 88 per cent, in the 
 above proportions, also the intermediate varieties to 98 per 
 cent., and have been quite successful ; but feel convinced 
 that the ordinary 98, as marked (which usually stands by 
 actual test 95 to 97 per cent.), is preferable, except in 
 cases where water is employed in dissolving the iodizing 
 salts, when I would use fully 98 per cent. 
 
 Before concluding the subject on plain collodion, I will 
 introduce the account given by Mr. E. A. Hadow of his 
 interesting and valuable experiments, as published in 
 Humphrey's Journal, Vol. VI, page 18. 
 
 " Having obtained good collodion-wool, the next point of 
 inquiry was with regard to the solvent ; to ascertain whe- 
 ther the addition of alcohol beyond what is necessary to 
 cause the solution of the gun-cotton in ether, were benefi- 
 cial or otherwise. For this purpose ether and alcohol were 
 prepared perfectly pure, and mixtures were made of 1 of 
 alcohol to 7 of ether, 2 to 6, 3 to 5, 4 to 4 and 5 to 3. In 
 one ounce of each were dissolved 6 grains of gun-cotton, 
 and 4 grains of iodide of ammonium (iodide of potassium 
 
PLAIN COLLODIOX. 55 
 
 could not be employed, since it requires a certain amount 
 both of water and alcohol to keep it in solution) ; they 
 were then compared, using a 35-grain solution of nitrate 
 of silver, both by pouring on separate glasses, and like- 
 wise by covering two halves of a plate with two samples, 
 as in examining the gun cottons, thus placing them under 
 the same circumstances during the same time ; in this way 
 the effect of adding alcohol was very clearly perceived, 
 since the difference between the collodions was much 
 greater than could have been anticipated. 
 
 " The first mixture containing only -|th of alcohol was 
 quite unfit for photographic purposes, from its being al- 
 most impossible, even with the most rapid immersion, to 
 obtain a film of uniform sensitiveness and opacity through- 
 out, the surface generally exhibiting nearly transparent 
 bands, having an iridescent appearance by reflected light. 
 
 " The second mixture with -Jth of the alcohol is liable to 
 great uncertainty, for if there be any delay in pouring off 
 the collodion the same appearances are seen as in the first, 
 and like it the surface is very insensitive to light, while if 
 the plate be rapidly plunged in the bath, the collodion 
 film becomes much more opaque than before, and is then 
 very sensitive. 
 
 "The third proportion of 3 of alcohol to 5 of ether is de- 
 cidedly the best, giving without the least difficulty a beau- 
 tifully uniform and highly sensitive film, at the same time 
 perfectly tough and easily removable from the glass if re- 
 quired. A further addition of alcohol, as in the two last col- 
 lodions, was not attended with any corresponding advan- 
 tage or increase of sensitiveness ; on the contrary, the large 
 proportion of alcohol rendered them less fluid, though with 
 a smaller quantity of gun cotton they would produce very 
 
56 PLAIN COLLODION. 
 
 good collodions, capable of giving fine films : the cause of 
 the weakness of the film, observed on adding much of the 
 ordinary alcohol, is the large amount of water it usually 
 contains. 
 
 " This surprising improvement, caused by the addition of 
 a certain quantity of alcohol, is referable to causes partly 
 chemical, partly mechanical, for, on examining the films, 
 it will be found in the first, and occasionally in the second 
 collodion, that the iodide of silver is formed on the surface, 
 and can be removed entirely by friction without destroy- 
 ing the transparent collodion film below, while in those 
 collodions that contain more than one-fourth of alcohol, 
 the iodide of silver is wholly in the substance, and in this 
 state possesses the utmost sensitiveness. 
 
 " This difference of condition is owing to the very scaring 
 solubility of ether in water, which in the first case pre- 
 vents the entrance of the nitrate of silver into the film, 
 consequently the iodide and silver solutions meet on the 
 surface ; but on addition of alcohol, its solubility enables 
 the two to interchange places, and thus the iodide of sil- 
 ver is precipitated throughout the substance in a state of 
 the utmost division. This difference is clearly seen under 
 the microscope, the precipitate being clotted in the one 
 case, while in the other the particles are hardly discover- 
 able from their fineness. 
 
 " The presence of a little water considerably modifies 
 these results, since it in some degree supplies the place of 
 alcohol, and is so far useful ; but in other respects it is in- 
 jurious, for, accumulating in quantity, if the collodion is 
 often used, it makes the film weak and gelatinous, and 
 what is worse, full of minute cracks on drying, which is 
 never the case when pure ether and alcohol are used. 
 
PLAIN COLLODION. 57 
 
 Since the ether of the shops almost always contains alco- 
 hol, and frequently water, it is important to ascertain their 
 amount before employing it for the preparation of collo- 
 dion ; the quantity of alcohol may be easily ascertained 
 by agitating the ether in a graduated measure glass (a 
 minim glass does very well) with half its bulk of a satu- 
 rated solution of chloride of calcium ; this should be poured 
 in first, its height noted, and the ether then poured on its 
 surface, the thumb then placed on the top, and the two 
 agitated together ; when separated, the increase of bulk 
 acquired by the chloride of calcium indicates the quantity 
 of alcohol present, and for this allowance should be made, 
 in the addition of alcohol afterwards to the collodion. 
 
 " Water is readily detected, either in ether or alcohol by 
 allowing a drop to fall into spirits of turpentine, with which 
 they ought to mix without turbidity ; this is immediately 
 produced if they contain water : for detecting water in 
 alcohol, benzole is a more delicate re-agent than spirits of 
 turpentine (Chemist, xxix, 203). It is also necessary that 
 ether should be free from a remarkable property it acquires 
 by long keeping, of decomposing iodides and setting free 
 iodine, which thus gives the collodion a brown color ; the 
 same property may be developed in any ether, as Schon- 
 bein discovered by introducing a red hot wire into the va- 
 por in the upper portion of a bottle containing a little 
 ether and water ; if it be then shaken up and a solution 
 of iodide poured in, the whole rapidly becomes brown ; 
 this re-action is very remarkable and difficult to explain 
 for even a mixture of the ether and nitric acid fails to pro- 
 duce a color immediately. Ether thus affected can only be 
 deprived of this property by rectification with caustic 
 potash/' 
 
58 IODIZED COLLODION FOR POSITIVES. 
 
 BROMO-!ODIZED COLLODION FOR POSITIVES. No. 1. 
 
 One very important object in connection with this part 
 of the collodion process is to have chemicals of a good 
 quality, and always employ those of a fixed standard. 
 
 Plain collodion, 10 ounces. 
 Solution of bromide, and iodide of potassium and 
 
 silver, (page 61) - 3 drachms. 
 
 Iodide of ammonium, 10 grains. 
 
 Hydro-bromic acid - G drops. 
 
 Double iodide of potassium and silver (see page 62) 
 enough so that when the plate comes from the nitrate of 
 silver bath, it will have an opaque cream color. 
 
 Remarks. In the preparation of this sensitive collodion, 
 it is necessary to be cautious and not add too much of the 
 iodide of potassium and silver, for in that case the coating- 
 would flake off, and falling into the silvering solution, the 
 operator would be obliged to filter it before he could silver 
 his plate with safety as regards spotting it. 
 
 The method I employ is to add the plain collodion, bro- 
 mide and iodide of potassium and silver, iodide of ammo- 
 nium and hydro-bromic acid, and then cautiously add the 
 double iodide of potassium and silver from five to ten 
 drops at a time, trying the collodion from time to time 
 by pouring a little on a narrow strip of glass, which I dip 
 into the silvering solution, and let it remain for two 
 minutes. If the coating assumes the proper color (a cream 
 color), I shake the contents of the bottle, and then stand 
 it aside to settle : it is better after it has stood for a week 
 or two. 
 
 This collodion I have used after it has been made eight 
 months, and produced fine and satisfactory results, and use 
 
IODIZED COLLODION FOR POSITIVES. 59 
 
 this nearly altogether in practice. Since the first edition 
 of this work has been issued, I have sold over two thousand 
 pounds of this preparation, and the demand is on the in- 
 crease. I will append another preparation (No. 2) which 
 I have successfully employed, and some operators prefer. 
 
 BROMO-!ODIZED COLLODION FOR ^POSITIVES. No. 2. 
 
 Plain collodion 10 ounces. 
 
 Iodide of potassium 30 grains. 
 
 Bromide of ammonium - 20 " 
 
 Enough of the double iodide of potassium and silver to 
 give the coating a crearn color when it comes from the 
 silvering solution. It will take from one to three drachms. 
 Or this last may be omitted, and a few drops of a saturated 
 solution of dry iodine in alcohol may be added. Either of 
 these plans have been successful in my practice. 
 
 Remarks. The iodide of potassium being insoluble in 
 the collodion, it should be first dissolved in as little water 
 as possible ; i. e., take the quantity, 30 grains, put it into 
 a one-ounce graduate, and with a glass rod stir it, adding 
 water, drop by drop, only until all of the salt is dissolved. 
 Then it may be poured into the collodion, and there will 
 be a white powdery precipitate. 
 
 The bromide of ammonium will dissolve in the collodion, 
 and can be put into it. When all of the accelerators are 
 in, it should be well shaken, and then allowed to settle 
 and become clear. When wanted, a sufficient quantity 
 may be poured into a vial (see Fig. 34) for use, and the 
 main or stock bottle should not be disturbed oftener than 
 necessary. This last collodion is not as durable as the 
 first, but is less trouble to prepare. 
 
60 IODIZED COLLODION FOR NEGATIVES. 
 
 BROMO-IODIZED COLLODION FOR NEGATIVES. 
 
 Plain collodion 8 ounces. 
 
 Iodide of potassium (dissolved as per page 62) 24 grains. 
 Bromide of ammonium - 16 " 
 
 This collodion should be allowed to stand and settle 
 twenty-four hours before it is used : when wanted, it 
 should be poured off into a collodion vial. The more free 
 the collodion is from sediment and small particles of dust 
 or undissolved cotton, the softer and more perfect will be 
 the impression it makes. 
 
 In case the above proportions of iodide of potassium 
 should not produce a cream-colored coating, when it comes 
 from the nitrate of silver bath, more may be added : for 
 example, if the coating is of a bluish tint, I would dissolve 
 6 grains of iodide of potassium in water, as before, and 
 then try it : shake well, and test it by putting a little on a 
 slip of glass, and dipping it into the silvering solution ; if 
 it coats to a cream-color, it is right. 
 
 It should be borne in mind, that after the addition of 
 iodide of potassium here recommended, the collodion 
 should be allowed to stand until settled, before undertak- 
 ing to produce a picture, although the coating may be 
 previously tested by means of a slip of glass. 
 
 SOLUTION OF BROMIDE AND IODIDE OF POTASSIUM AND 
 SILVER. 
 
 D'ssolve 130 grains of crystallized nitrate of silver in 4 
 ounces of pure water, in a long 8-ounce vial. Then in a 
 clean 1 -ounce graduate, or some other convenient vessel 
 
BROMIDE AND IODIDE OF SILVER. 61 
 
 containing half an ounce of water, dissolve 130 grains 
 bromide of potassium. "When this and the nitrate of silver 
 are both dissolved, pour the solution of bromide of potas- 
 sium into the vial containing the silver, and a thick yel- 
 low precipitate will fall. This is the bromide of potassium 
 and silver. This should be washed by nearly filling the 
 vial with water ; shake it, and then let it settle, which it 
 will readily do, and then pour on the water, leaving the 
 yellow mass in the bottom of the vial ; continue this ope- 
 ration of washing for at least ten changes of water ; then, 
 after draining off' the water as close as possible, put into 
 the vial four ounces of alcohol, shake it well and let it 
 settle ; then pour off as close as possible. By this means 
 the water is nearly all taken out. 
 
 Pour into the vial three ounces of alcohol ; then in a small 
 mortar finely pulverize one ounce of iodide of silver, and 
 the solution, which was before clear, will be more or less 
 of a yellow color, and the bulk of the yellow precipitate 
 will be diminished. I have sometimes completely re-dis- 
 solved the yellow precipitate, but this does not often occur, 
 except there be more water present than is advisable. It 
 is better to have an excess of bromide of potassium in the 
 solution. This can be seen by its being white, and re- 
 maining undissolved in the bottom of the vial. This solu- 
 tion should be prepared in the evening, or in a dark room, 
 and only the light of a lamp or candle employed. 
 
 DOUBLE IODIDE OF POTASSIUM AND SILVER. 
 
 This solution is made in the same manner as in the 
 foregoing article, substituting the iodide of potassium for 
 the bromide no bromide being used in this preparation. 
 . 4 
 
62 DEVELOPING SOLUTION. 
 
 The yellow precipitate in this case will be re-dissolvedf 
 and taken up in the solution : it may require more than 
 one ounce of pulverized iodide of potassium to effect this, 
 "but it may be added in excess, so that the solution shall 
 contain a quantity in powder. 
 
 DEVELOPING SOLUTION 
 
 Proto-sulphate'of iron, - - 3 ounces. 
 
 Rain or distilled water, - 1 quart. 
 
 Put these into a quart bottle, and shake until the crys- 
 tals are all dissolved, and this can be kept for a stock bot- 
 tle, and when wanted for use pour into another bottle. 
 
 Of the'above solution, 5 ounces. 
 
 Acetic acid (No. 8) - 1 " 
 
 Chemically pure nitric acid - 20 drops. 
 
 Shake this mixture well, and filter through a sponge, 
 and it is ready for use. I file a mark in this bottle indi- 
 cating five ounces, and another for 1 ounce : this will save 
 time in mixing the solution. 
 
 Remarks. In my recent tour of the United States, I 
 found it difficult to obtain a good article of proto-sulphate 
 of iron, and in its stead I used the common copperas, such 
 as I could find almost in any store. I employ from one- 
 fourth to one-half more than the quantity given above. If 
 it looked a clear green, and free from a white or brown- 
 ish powder, about one-fourth addition : i. e., four ounces, 
 instead of three, as given above. If the solution in the 
 stock bottle is not wanted for a week or more, a few crys- 
 tals of the proto-sulphate of iron should be added, as it 
 decomposes, and the strength is depreciated. 
 
FIXING SOLUTION. HUiMPHREv's COLLODION GILDING, 63 
 
 There is quite a difference in the strength of the acetic 
 acid as sold by our country druggists, and the operator 
 should be sure that he has No. 8, to which quality the 
 above proportions are adapted. I never have employed 
 the developing solution but once, but can see no objections 
 to use it for a number- of glass plates, but it should be 
 filtered every time before using. The quantity of nitric 
 acid may be increased, so long as a proper proportion is 
 preserved with the strength of the bath. The effect of 
 this addition of acid will be to brighten the impression ; 
 but if carried too far, the reduction (developing) will be 
 irregular, and the harmony of the impression injured. 
 
 FIXING SOLUTION. 
 
 Water, - 8 ounces, 
 
 Cyanide of potassium, ... about 1 drachm* 
 
 Remarks. I put enough of the cyanide of potassium 
 into the water to make the solution of such strength as to 
 dissolve off the iodide of silver (" coating") in from twenty 
 to sixty seconds. The operation is quite similar to that of 
 hyposulphate of soda upon the coating of the Daguerreo- 
 type plate. A too concentrated solution is likely to injure 
 the sharpness of the image. 
 
 BRIGHTENING AND FINISHING THE IMAGE. 
 
 The article I now employ for finishing off my Positives 
 is in market, and known as HUMPHREY'S COLLODION GILD- 
 ING. It is a new preparation, and exerts a powerful influ- 
 ence upon the image, having the same brightening effect 
 as chloride of gold on the daguerreotype. There is no ar- 
 
64 NITRATE OF SILVER BATH, 
 
 ticle now in market that equals this. I have until quite 
 recently used a varnish for this purpose, but having some- 
 thing that is of far greater value, I have discarded it. It 
 is one of the most valuable improvements since the applica- 
 tion of the Collodion Film as a vehicle for producing photo- 
 graphic images. It is a new discovery, and is being rapidly 
 brought into use by the first ambrotypers and photogra- 
 phers in America. It adds at least one-half to the beauty of 
 an ambrotype, above any method heretofore in use. It is 
 imperishable, giving a surface almost equal in hardness to the 
 glass itself. It is easy of application; it gives abrilliant finish; 
 it is not affected by a moist atmosphere ; it is not affected 
 by pure water ; it is the best article ever used for finish- 
 ing ambrotypes ; it will preserve glass negatives for all 
 time ; it will preserve the whites in the ambrotype ; it 
 gives a rich lustre to drapery ; it will bear exposure to the 
 hot sun ; it preserves positives and negatives from injury 
 by light. It is an article that, when once tried, the ope- 
 rator upon glass (positive, negative, or albumenized plates) 
 will not do without. 
 
 The ingredients in the composition of this gilding are 
 neither patented nor published, but it can be procured from 
 any dealer in photographic chemicals. 
 
 NITRATE OF SILVER BATH. 
 
 I here give what I consider an improvement on the bath 
 mentioned in the first edition of this work. I first pub- 
 lished it in Humphrey's Journal, No. 23, Vol. VII. : 
 
 The nitrate of silver solution is an important mixture in 
 the chemical department of the ambrotype process, and 
 
NITRATE OF SILVER BATH. 65 
 
 requires the especial care of the operator in its prepara- 
 tion. I give the following as one of the most approved 
 for general practice. It is well adapted to the production 
 of positives, and its action is of great uniformity. 
 
 Pure water ..... 1 ounce. 
 
 Nitrate of silver in crystals [neutral to acid test] 45 grains. 
 Nitric acid C. P. [Quantity as given below]. 
 
 This proportion is to be observed for any quantity of 
 solution. If I were to prepare a bath 40 ounces, I would 
 proceed as follows : 
 
 Water ... 40 ounces. 
 
 Nitrate of silver - - 1800 grains. 
 
 Measure the water, and put into a two-quart bottle ; 
 then pour out 8 oz. of it in a pint bottle, and into this put 
 the whole of the nitrate of silver (1800 gr.) ; shake it well 
 until it is all dissolved. This forms a concentrated solu- 
 tion into which put the following prepared iodide of sil- 
 ver : 
 
 Dissolve in a 3 or 4 oz. bottle containing 1 oz. water, 
 10 gr. nitrate of silver ; and in another bottle or graduate 
 containing a little water, dissolve 10 grains of iodide of 
 potassium; pour this into the 10 grain solution of nitrate 
 of silver, and a yellow substance (iodide of silver) will 
 precipitate ; fill the bottle with water, and let it settle ; 
 then pour off the water, leaving the yellow mass behind ; 
 again pour on it clean water, shake it, and let it settle as 
 before, and pour off again ; repeat this for about six 
 changes of water. 
 
66 VOCABULARY OF 
 
 Then it (the iodide of silver) is to be put into the bottle 
 containing the 8 oz. water and 1800 gr. of nitrate of silver ; 
 shake it well, and it will nearly or quite all dissolve ; 
 pour this into the two-quart bottle, and shake well ; it 
 will be of a yellowish white tint, and should be filtered 
 through asbestos or sponge, when it will become clear. 
 When clear, test the solution with blue litmus-paper ; if 
 it turns it red, it is sufficiently acid ; if it does not change 
 it, add one or two drops of nitric acid, chemically pure ; 
 then test it again ; if it does not change it, add one or two 
 drops more, or just enough to change the paper to the 
 slightest red. 
 
 A solution prepared in this proportion will, like others, 
 improve by age. An old bath is considered far more va- 
 luable than one newly prepared. These remarks may ap- 
 pear to old photographic operators as of no importance, 
 but they must bear in mind that there are hundreds just 
 adopting this new process of picture taking. 
 
 This solution will work more satisfactorily than the one 
 I formerly used. It will work quicker in the camera, and 
 is equally durable. 
 
 ACKNOWLEDGMENT. The following pages, under the 
 head of Vocabulary of Photographic Chemicals, and treat- 
 ing upon the Chemicals used in Photography, are taken 
 from the third edition of " Hardwich's Photographic Che- 
 mistry :" 
 
 Vocabulary of Photographic Chemicals. 
 
 ACETIC ACID. 
 
 Symbol, C 4 H 3 3 + HO. Atomic weight, 60. 
 Acetic acid is a product of the oxidation of alcohol. 
 
PHOTOGRAPHIC CHEMICALS. 07 
 
 Spirituous liquids, when perfectly pure, are not affected 
 by exposure to air ; but if a portion of yeast, or nitroge 
 nous organic matter of any kind, be added, it soon acts as 
 a ferment, and causes the spirit to unite with oxygen de 
 rived from the atmosphere, and to become sour from for- 
 mation of acetic acid or " vinegar." 
 
 Acetic acid is also produced on a large scale by heating 
 wood in close vessels ; a substance distils over which is 
 acetic acid coKtaminated with empyreumatic and tarry 
 matter ; it is termed pyroligneous acid, and is much used 
 in commerce. 
 
 The most concentrated acetic acid may be obtained by 
 neutralizing common vinegar with carbonate of soda and 
 crystallizing out the acetate of soda so formed ; this ace- 
 tate of soda is then distilled with sulphuric acid, which 
 removes the soda and liberates acetic acid : the acetic acid 
 being volatile, distils over, and may be condensed. 
 
 Properties of Acetic Acid. The strongest acid contains 
 only a single atom of water ; it is sold under the name of 
 " glacial acetic acid," so called from its property of solidi - 
 fying at a moderately low temperature. At about 50 the 
 crystals melt, and form a limpid liquid of pungent odor 
 and a density nearly corresponding to that of water; the 
 specific gravity of acetic acid, however, is no test of its 
 real strength, which can only be estimated by analysis. 
 
 The commercial glacial acetic acid is often diluted with 
 water, which may be suspected if it does not solidify dur 
 ing the cold winter months. Sulphurous and hydrochlo- 
 ric acids are also common impurities. They are injurious 
 in photographic processes from their property of precipi- 
 tating nitrate of silver. To detent them proceed as fol- 
 lows : dissolve a small crystal of nitrate of silver in a 
 
68 VOCABULARY OF 
 
 few drops of water, and add to it about half a drachm of 
 the glacial acid ; the mixture should remain quite clear 
 even when exposed to the light. Hydrochloric and sul- 
 phurous acids produce a white deposit of chloride or sul- 
 phite of silver ; and if aldehyde or volatile tarry matter be 
 present in the acetic acid, the mixture with nitrate of sil- 
 ver, although clear at first, becomes discolored by the ac- 
 tion of light. 
 
 Many photographers employ a cheaper form of acetic 
 acid, sold by druggists as " Beaufoy's" acid ;* it should be 
 of the strength of the acetic acid fortiss. of the London 
 Pharmacopoeia, containing 30 per cent, real acid, and must 
 be tested for sulphuric acid (see sulphuric acid), and also 
 by mixing with nitrate of silver. 
 
 ACETATE OF SILVER. (See Silver, Acetate of.) 
 
 ALBUMEN. 
 
 Albumen is an organic principle, found both in the ani 
 mal and vegetable kingdom. Its properties are best stu- 
 died in the white of egg, which is a very pure form of 
 albumen. 
 
 Albumen is capable of existing in two states ; in one of 
 which it is soluble, in the other insoluble in water. The 
 aqueous solution of the soluble variety gives a slightly 
 alkaline reaction to test-paper ; it is somewhat thick and 
 glutinous, but becomes more fluid on the addition of a 
 small quantity of an alkali, such as potash or ammonia. 
 
 * In this country the practitioner uses the article sold in market as "Ace- 
 tic Acid, No. 8." S. D. H. 
 
PHOTOGRAPHIC CHEMICALS. 69 
 
 Soluble albumen may be converted into the insoluble 
 form in the following ways : 
 
 1 . By the application of heat. A moderately strong 
 solution of albumen becomes opalescent and coagulates on 
 being heated to about 150, but a temperature of 212 is 
 required if the liquid is very dilute. A layer of dried 
 albumen cannot easily be coagulated by the mere appli- 
 cation of heat. 
 
 2. By addition of strong acids. Nitric acid coagulates 
 albumen perfectly without the aid of heat. Acetic acid, 
 however, acts differently, appearing to enter into combi- 
 nation with the albumen, and forming a compound solu- 
 ble in warm water acidified by acetic acid. 
 
 3. By the action of metallic salts. Many of the salts of 
 the metals coagulate albumen very completely. Nitrate 
 of silver does so ; also the bichloride of mercury. Ammo- 
 niacal oxide of silver, however, does not coagulate albu- 
 men. 
 
 The white precipitate formed on mixing albumen with 
 nitrate of silver is a chemical compound of the animal 
 matter with protoxide of silver. This substance, which 
 has been termed albuminate of silver, is soluble in ammo- 
 nia and hyposulphite of soda ; but after exposure to light, 
 or heating in a current of hydrogen gas, it assumes a brick- 
 red color, being probably reduced to the condition of a 
 salt of the suboxide of silver. It is then almost insoluble 
 in ammonia, but enough dissolves to tinge the liquid wine- 
 red. The author is of opinion that the red coloration of 
 solution of nitrate of silver employed in sensitizing the 
 albumenized photographic paper is produced by the same 
 compound, although often referred to the presence of sul- 
 phuret of silver. 
 
70 VOCABULARY OF 
 
 Albumen also combines with lime and baryta ; and 
 chloride of barium has been recommended in positive 
 printing upon albumenized paper, probably from this 
 cause. 
 
 Chemical composition of albumen. Albumen belongs to 
 the nitrogenous class of organic substances. It also con- 
 tains small quantities of sulphur and phosphorus. 
 
 ALCOHOL. 
 Symbol, C 4 H 6 2 . Atomic weight, 46. 
 
 Alcohol is obtained by the careful distillation of any 
 spirituous or fermented liquor. If wine or beer be placed 
 in a retort, and heat applied, the alcohol, being more vo- 
 latile than water, rises first, and is condensed in an ap- 
 propriate receiver ; a portion of the vapor of water, how- 
 ever, passes over with the alcohol, and dilutes it to a 
 certain extent, forming what is termed " spirits of wine." 
 Much of this water may be removed by redistillation from 
 carbonate of potash ; but in order to render the alcohol 
 thoroughly anhydrous, it is necessary to employ quick lime 
 which possesses a still greater attraction for water. An 
 equal weight of this powdered lime is mixed with strong 
 alcohol of '833, and the two are distilled together. 
 
 Properties of Alcohol. Pure anhydrous alcohol is a lim- 
 pid liquid, of an agreeable odor'and pungent taste ; sp. gr. 
 at 60, '794. It absorbs vapor of water, and becomes 
 diluted by exposure to damp air ; boils at 173 Fahr. It 
 has never been frozen. 
 
 Alcohol distilled from carbonate of potash has a speci- 
 fic gravity of '815 to '823, and contains 90 to 93 per cent, 
 of real spirit. 
 
PHOTOGRAPHIC CHEMICALS. i I 
 
 The specific gravity of ordinary rectified spirits of wine 
 is usually about -840, and it contains 80 to 83 per cent, of 
 absolute alcohol. 
 
 AMMONIA. 
 Symbol, NH 3 or NH 4 0. Atomic weight, 17. 
 
 The liquid known by this name is an aqueous solution 
 of the volatile gas ammonia. Ammoniacal gas contains 1 
 atom of nitrogen combined with three of hydrogen : these 
 two elementary bodies exhibit no affinity for each other, 
 but they can be made to unite under certain circumstances, 
 and the result is ammonia. 
 
 Properties of Ammonia. Ammoniacal gas is soluble in 
 water to a large extent ; the solution possessing those pro- 
 perties which are termed alkaline. Ammonia, however, 
 differs from the other alkalies in one important particular 
 it is volatile : hence the original color of turmeric paper 
 affected by ammonia is restored on the application of heat. 
 Solution of ammonia absorbs carbonic acid rapidly from 
 the air, and is converted into carbonate of ammonia ; it 
 should therefore be preserved in stoppered bottles. Be- 
 sides carbonate, commercial ammonia often contains chlo- 
 ride of ammonium, recognized by the white precipitate 
 given by nitrate of silver after acidifying with pure 
 nitric acid. 
 
 The strength of commercial ammonia varies greatly ; 
 that sold for pharmaceutica purposes, under the name of 
 liquor ammonice, contains about 10 per cent, of real am- 
 monia. The sp. gr. of aqueous ammonia diminishes with 
 the proportion of ammonia present, the liquor ammonice 
 being usually about -936. 
 
VJ VOCABULARY OF 
 
 Chemical Properties. Ammonia, although forming a 
 large class of salts, appears at first sight to contrast strongly 
 i composition with the alkalies proper, such as potash 
 and soda. Mineral bases generally are protoxides of metals, 
 but ammonia consists simply of nitrogen and hydrogen 
 united with oxygen. The following remarks may perhaps 
 tend somewhat to elucidate the difficulty : 
 
 Theory of Ammonium. This theory supposes that a sub- 
 stance exists possessing the properties of a metal, but dif- 
 ferent from metallic bodies generally in being compound in 
 structure : the formula assigned to it is NH 4 , 1 atom of 
 nitrogen united with 4 of hydrogen. The hypothetical 
 metal is termed " ammonium," and ammonia, associated 
 with an atom of water, may be viewed as its oxide ; for 
 NH 3 -}-HO plainly equals NH 4 0. Thus, as potash is the 
 oxide of potassium, so ammonia is the oxide of ammonium, 
 
 The composition of the salts of ammonia is on this view 
 assimilated to those of the alkalies proper. Thus, sulphate 
 of ammonia is a sulphate of the oxide of ammonium j 
 muriate or hydrochlorate of ammonia is a chloride of am- 
 monium, etc. 
 
 AMMONIO-NITRATE OF SILVER, 
 (See Silver, Ammonio-Nitrate of.) 
 
 AQUA REGIA. (See Nitro-Hydrochloric Acid.) 
 BARYTA, NITRATE OF. (See JNitrate of Baryta.) 
 
 BICHLORIDE OF MERCURY. 
 (See Mercury, Bichloride of.) 
 
 BROMINE. 
 Symbol, Br. Atomic weight, 78. 
 
 This elementary substance is obtained from the uncrys- 
 
PHOTOGRAPHIC CHEMICALS. 73 
 
 tallizable residuum of sea-water, termed bittern. It exists 
 in the water in very minute proportion, combined with 
 magnesium in the form of a soluble bromide of magne- 
 sium. 
 
 Properties. Bromine is a deep reddish-brown liquid of 
 a disagreeable odor, and fuming strongly at common 
 temperatures ; sparingly soluble in water (1 part in 23, 
 Lowig), but more abundantly so in alcohol, and especially 
 in ether. It is very heavy, having a specific gravity of 3*0. 
 
 Bromine is closely analogous to chlorine and iodine in 
 its chemical properties. It stands on the list intermedi- 
 ately between the two ; its affinities being stronger than 
 those of iodine, but weaker than chlorine. (See chlorine.) 
 
 It forms a large class of salts, of which the bromides of 
 potassium, cadmium, and silver are the most familiar to 
 photographers. 
 
 BROMIDE OF POTASSIUM. 
 Symbol, KBr. Atomic weight, 118. 
 
 Bromide of potassium is prepared by adding bromine to 
 caustic potash, and heating the product, which is a mixture 
 of bromide of potassium and bromate of potash, to redness, 
 in order to drive off the oxygen from the latter salt. It 
 crystallizes in anhydrous cubes, like the chloride, and 
 iodide, of potassium ; it is easily soluble in water, but 
 more sparingly so in alcohol ; it yields red fumes of bro- 
 mine when acted upon by sulphuric acid. 
 
 BROMIDE OF SILVER. (See Silver, Bromide of.) 
 
 CARBONATE OF SODA. 
 Symbol, NaO C0 2 + 10 Aq. 
 This salt was formerly obtained from the ashes of sea- 
 
74 VOCABULARY OF 
 
 weeds, but is now more economically manufactured on a 
 large scale from common salt. The chloride of sodium is 
 first converted into sulphate of soda, and afterwards the 
 sulphate into carbonate of soda. 
 
 Properties. -The perfect crystals contain ten atoms of 
 water, which are driven off by the application of heat, 
 leaving a white powder the anhydrous carbonate. Com- 
 mon washing soda is a neutral carbonate, contaminated to a 
 certain extent with chloride of sodium and sulphate of 
 soda. The carbonate used for effervescing draughts is 
 either a bicarbonate with 1 atom of water, or a sesquicar- 
 boriate, containing about 40 per cent, of real alkali ; it is 
 therefore nearly double as strong as the washing carbo 
 nate, which contains about 22 per cent, of soda. Carbo- 
 nate of soda is soluble in twice its weight of water at 60, 
 the solution being strongly alkaline. 
 
 CARBONATE OF POTASH. (See Potash, Carbonate of.) 
 CASEJNE. (See, Milk.) 
 CHARCOAL, ANIMAL. 
 
 Animal charcoal is obtained by heating animal sub- 
 stances, such as bones, dried blood, horns, etc., to redness, 
 in close vessels, until all volatile empyreumatic matters 
 have been driven ofl, and a residue of carbon remains. 
 When prepared from bones it contains a large quantity of 
 inorganic matter in the shape of carbonate and phosphate 
 of lime, the former of which produces alkalinity in reacting 
 upon nitrate of silver. Animal charcoal is freed from 
 these earthy salts by repeated digestion in hydrochloric 
 acid ; but unless very carefully washed it is apt to retain 
 
PHOTOGRAPHIC CHEMICALS. 75 
 
 an acid reaction, and so to liberate free nitric acid when 
 added to solution of nitrate of silver. 
 
 Properties.-*- Animal charcoal, when pure, consists solely 
 of carbon, and burns away in the air without leaving any 
 residue : it is remarkable for its property of decolorizing 
 solutions ; the organic coloring substance being separated, 
 but not actually destroyed, as it is by chlorine employed as 
 a bleaching agent. This power of absorbing coloring 
 matter is not possessed in an equal degree by all varieties 
 of charcoal, but is in great measure peculiar to those de- 
 rived from the animal kingdom. 
 
 CHINA CLAY OR KAOLIN. 
 
 This is prepared, by careful levigation, from mouldering 
 granite and other disintegrated felspathic rocks. It con- 
 sists of the silicate of alumina, that is, of silicic acid or 
 flint j which is an oxide of silicon, united with the base 
 alumina (oxide of aluminum). Kaolin is perfectly inso- 
 luble in water and acids, and produces no decomposition 
 in solution of nitrate of silver. It is employed by photo- 
 graphers to decolorize solutions of nitrate of silver which 
 have become brown from the action of albumen or other 
 organic matters. 
 
 CHLORINE. 
 
 Symbol, 01. Atomic weight, 36. 
 
 Chlorine is a chemical element found abundantly in na- 
 ture, combined with metallic sodium in the form of chlo- 
 ride of sodium, or sea-salt. 
 
 Preparation By distilling common salt with sulphuric 
 
 acid, sulphate of soda and hydrochloric acid are formed. 
 
76 VOCABULARY OF 
 
 Hydrochloric acid contains chlorine combined with hydro- 
 gen ; by the action of nascent oxygen (see oxygen), the hy- 
 drogen may be removed in the form of water, and the 
 chlorine left alone. 
 
 Properties.- Chlorine is a greenish-yellow gas, of a pun- 
 gent and suffocating odor ; soluble to a considerable extent 
 in water, the solution possessing the odor and color of the 
 gas. It is nearly 2J times as heavy as a corresponding 
 bulk of atmospheric air. 
 
 Che?nical Properties. Chlorine belongs to a small natu- 
 ral group of elements which contains also bromine, iodine, 
 and fluorine. They are characterized by having a strong 
 affinity for hydrogen, and also for the metals, but are 
 comparatively indifferent to oxygen. Many metallic sub- 
 stances actually undergo combustion when projected into an 
 atmosphere of chlorine, the union between the two taking 
 place with extreme violence. The characteristic bleach- 
 ing properties of chlorine gas are explained in the same 
 manner : Hydrogen is removed from the organic sub- 
 stance, and in that way the structure is broken up and the 
 color destroyed. 
 
 Chlorine is more powerful in its affinities than either 
 bromine or iodine. The salts formed by these three ele- 
 ments are closely analogous in composition aud often in 
 properties. Those of the alkalies, alkaline earths, and' 
 many of the metals are soluble in water, but the silver 
 salts are insoluble ; the lead salts sparingly so. 
 
 The combinations of chlorine, bromine, iodine, and 
 fluorine, with hydrogen, are acids, and neutralize alkalies 
 in the usual manner, with formation of alkaline chloride 
 and water. 
 
 The test by which the presence of chlorine is detected, 
 
PHOTOGRAPHIC CHEMICALS. 77 
 
 either free or in combination with bases, is nitrate of silver ; 
 it gives a white curdy precipitate of chloride of silver, in- 
 soluble in nitric acid, but soluble in ammonia. The so- 
 lution of nitrate of silver employed as the test must not 
 contain iodide of silver, as this compound is precipitated 
 by dilution. 
 
 CHLORIDE OF AMMONIUM. 
 Symbol, NH 4 Cl. Atomic weight, 54. 
 
 This salt, also known as muriate or hydrochlorate of 
 ammonia, occurs in commerce in the form of colorless and 
 translucent masses, which are procured by sublimation, the 
 dry salt being volatile when strongly heated. It dissolves 
 in an equal weight of boiling, or in three parts of cold 
 water. It contains more chlorine in proportion to the 
 weight used than chloride of sodium, the atomic weights 
 of the two being as 54 to 60. 
 
 CHLORIDE OF BARIUM. 
 Symbol, BaCl+2 HO. Atomic weight, 123. 
 
 Barium is a metallic element, very closely allied to cal- 
 cium, the elementary basis of lime. The chloride of ba- 
 rium is commonly employed as a test for sulphuric acid, 
 with which it forms an insoluble precipitate of sulphate 
 of baryta. It is also said to affect the color of the pho- 
 tographic image when used in preparing positive paper ; 
 which may possibly be due to a chemical combination of 
 baryta with albumen : but it must be remembered that 
 this chloride, from its high atomic weight, contains less 
 chlorine than the alkaline chlorides. 
 
 Properties of Chloride of Barium. Chloride of barium 
 
78 VOCABULARY OF 
 
 occurs in the form of white crystals, soluble in about two 
 parts of water, at common temperature. These crystals 
 contain two atoms of water of crystallization, which are 
 expelled at 212, leaving the anhydrous chloride. 
 
 CHLORIDE OF GOLD. (See Gold, Chloride of.) 
 
 CHLORIDE OF SODIUM. 
 Symbol, NaCl. Atomic weight, 60. 
 
 Common salt exists abundantly in nature, both in the 
 form of solid rock-salt and dissolved in the waters of the 
 ocean. 
 
 Properties of the pure Salt. Fusible without decompo- 
 sition at low redness, but sublimes at higher temperatures ; 
 the melted salt concretes into a hard white mass on cool- 
 ing. Nearly insoluble in absolute alcohol, but dissolves in 
 minute quantity in rectified spirit. Soluble in three parts 
 of water, both hot and cold. Crystallizes in cubes, which 
 are anhydrous. 
 
 Impurities of Common Salt. Table salt often contains 
 large quantities of the chlorides of magnesium and cal- 
 cium, which, being deliquescent, produce a dampness by 
 absorption of atmospheric moisture : sulphate of soda is 
 also commonly present. The salt may be purified by re- 
 peated recrystallization, but it is more simple to prepare 
 the pure compound directly, by neutralizing hydrochloric 
 acid with carbonate of soda. 
 
 CHLORIDE OF SILVER. (See Silver, Chloride of.) 
 
 CITRIC ACID. 
 This acid is found abundantly in lemon-juice and in 
 
PHOTOGRAPHIC CHEMICALS. 79 
 
 lime-juice. It occurs in commerce in the form of large 
 crystals, which are soluble in less than their own weight 
 of water at 60. 
 
 Commercial citric acid is sometimes mixed with tar- 
 taric acid. The adulteration may be discovered by mak- 
 ing a concentrated solution of the acid and adding acetate 
 of potash ; crystals of bitartrate of potash will separate if 
 tartaric acid be present. 
 
 Citric acid is tribasic. It forms with silver a white in- 
 soluble salt, containing 3 atoms of oxide of silver to 1 
 atom of citric acid. If the citrate of silver be heated in 
 a current of hydrogen gas, a part of the acid is liberated 
 and the salt is reduced to a citrate of suboxide of silver ; 
 which is of a red color. The action of white light in red- 
 dening citrate of silver is shown by the author to be of a 
 similar nature. 
 
 CYANIDE OF POTASSIUM. 
 Symbol, K, C 2 N, or KCy. Atomic weight, 66. 
 
 This salt is a compound of cyanogen gas with the metal 
 potassium. Cyanogen is not an elementary body, like 
 chlorine or iodine, but consists of carbon and nitrogen 
 united in a peculiar manner. Although a compound sub- 
 stance, it reacts in the manner of an element, and is there- 
 fore (like ammonium, previously described) an exception 
 to the usual laws of chemistry. Many other bodies of a 
 similar character are known. 
 
 ETHER. 
 Symbol, C 4 H 5 0. Atomic weight, 37. 
 
 Ether is obtained by distilling a mixture of sulphuric 
 
80 VOCABULARY OF 
 
 acid and alcohol. If the formula of alcohol (C 4 H 6 2 ) be 
 compared with that of ether, it will be seen to differ from 
 it in the possession of an additional atom of hydrogen and 
 of oxygen : in the reaction, the sulphuric acid removes 
 these elements in the form of water, and by so doing con- 
 verts one atom of alcohol into an atom of ether. The 
 term sulphuric applied to the commercial ether has refe- 
 rence only to the manner of its formation. 
 
 Properties of Ether. It is neither acid nor alkaline to 
 test-paper. Specific gravity, at 60, about '720. Boils at 
 98 Fahrenheit. The vapor is exceedingly dense, and 
 may be seen passing off from the liquid and falling to the 
 ground : hence the danger of pouring ether from one bottle 
 to another if a flame be near at hand. 
 
 Ether does not mix with water in all proportions ; if the 
 two are shaken together, after a short time the former 
 rises and floats upon the surface. In this way a mixture 
 of ether and alcohol may be purified to some extent, as in 
 the common process of washing ether. The water em- 
 ployed however always retains a certain portion of ether 
 (about a tenth part of its bulk), and acquires a strong 
 ethereal odor ; washed ether also contains water in small 
 quantity. 
 
 Bromine and iodine are both soluble in ether, and gra- 
 dually react upon and decompose it. 
 
 The strong alkalies, such as potash and soda, also de- 
 compose ether slightly after a time, but not immediately. 
 Exposed to air and light, ether is oxidized and acquires a 
 peculiar odor. 
 
 Ether dissolves fatty and resinous substances readily, 
 but inorganic salts are mostly insoluble in this fluid. 
 Hence it is that iodide of potassium and other substances 
 
PHOTOGRAPHIC CHEMICALS. 81 
 
 dissolved in alcohol are precipitated to a certain extent by 
 the addition of ether. 
 
 FLUORIDE OF POTASSIUM. 
 Symbol, KF. Atomic weight, 59. 
 
 Preparation. -Fluoride of potassium is formed by satu- 
 rating hydrofluoric acid with potash, and evaporating to 
 dryness in a platinum vessel. Hydrofluoric acid contains 
 fluorine combined with hydrogen ; it is a powerfully acid 
 and corrosive liquid, formed by decomposing flour spar, 
 which is a fluoride of calcium, with strong sulphuric acid; 
 the action which takes place being precisely analogous to 
 that involved in the preparation of hydrochloric acid. 
 
 Properties, A deliquescent salt, occurring in small and 
 imperfect crystals. Very soluble in water : the solution 
 acting upon glass in the same manner as hydrofluoric 
 acid. 
 
 FORMIC ACID. 
 
 Symbol, C 2 H0 3 . Atomic weight, 37. 
 
 This substance was originally discovered in the red ant 
 (Formica rufa), but it is prepared on a large scale by dis- 
 tilling starch with binoxide of manganese and sulphuric 
 acid. 
 
 Properties. The strength of commercial formic acid is 
 uncertain, but it is always more or less dilute. The 
 strongest acid, as obtained by distilling formiate of soda 
 with sulphuric acid, is a fuming liquid with a pungent 
 odor, and containing only one atom of water : it inflames 
 the skin in the same manner as the sting of the ant. 
 
 Formic acid reduces the oxides of gold, silver, and mer- 
 
82 VOCABULAki ul* 
 
 cury, to the metallic state, and is itself oxidized into car* 
 bonic acid. The alkaline formiates also possess the same 
 
 properties. 
 
 GELATINE* 
 
 Symbol, C 13 H 10 5 N 2 . Atomic weight, 156. 
 
 This is an organic substance somewhat analogous to 
 albumen, but differing from it in properties. It is obtained 
 by subjecting bones, hoofs, horns, calves' feet, etc., to the 
 action of boiling water. The jelly formed on cooling is 
 termed size, or when dried or cut into slices, glue. Gela- 
 tine, as it is sold in the shops, is a pure form of glue. 
 Isinglass is gelatine prepared, chiefly in Russia, from the 
 air-bladders of certain species of sturgeon. 
 
 Properties of Gelatine. Gelatine softens and swells up 
 in cold water, but does not dissolve until heated : the hot 
 solution, on cooling, forms a tremulous jelly. One ounce 
 f cold water will retain about three grains of isinglass 
 without gelatinizing ; but much depends upon the tempe- 
 rature, a few degrees greatly affecting the result. 
 
 Gelatine forms no compound with oxide of silver ana- 
 logous to the albuminate of silver ; which fact explains 
 the difference in the photographic properties fo albumen 
 
 and gelatine. 
 
 GLYCERINE. 
 
 Fatty bodies are resolved by treatment with an alkali 
 into an acid which combines with the alkali, forming a 
 soap, and glycerine, remaining in solution. 
 
 Pure glycerine, as obtained by Price's patent process of 
 distillation, is a viscid liquid of sp. gr. about 1'23 ; miscible 
 in all proportions with water and alcohol. It is peculiarly 
 a neutral substance, exhibiting no tendency to combine 
 
PHOTOGRAPHIC CHEMICALS. 83 
 
 with acids or bases. It has little or no action upon nitrate 
 of silver in the dark, and reduces it very slowly even when 
 exposed to light. 
 
 GOLD, CHLORIDE OF. 
 Symbol, AuCl 3 . Atomic weight, 303. 
 
 This salt is formed by dissolving pure metallic gold in 
 nitro-hydrochloric acid, and evaporating at a gentle heat. 
 The solution affords deliquescent crystals of a deep orange 
 color. 
 
 Chloride of gold, in a state fit for photographic use may 
 easily be obtained by the following process : Place a 
 half-sovereign in any convenient vessel, and pour on it 
 half a drachm of nitric acid mixed with two and and a 
 half drachms of hydrochloric acid and three drachms of 
 water ; digest by a gentle heat, but do not boil the acid, or 
 much of the chlorine will be driven off in the form of gas. 
 At the expiration o.f a few hours add fresh aqua regia in 
 quantity the same as at first, which will probably com- 
 plete the solution, but if not, repeat the process a third 
 time. 
 
 Lastly, neutralize the liquid by adding carbonate of soda 
 until all effervescence ceases, and a green precipitate 
 forms ; this is carbonate of copper, which must be allowed 
 several hours to separate thoroughly. The solution then 
 contains chloride of gold in a neutral state, and free from 
 copper and silver, with which the metallic gold is alloyed 
 in the standard coin of the realm. 
 
 The weight of a half-sovereign is about 61 grains, of 
 which 56 grains are pure gold. This is equivalent to 86 
 grains of chloride of gold, which will therefore be the 
 quantity contained in the solution. 
 
84 VOCABULARY OF 
 
 The following process for preparing chloride of gold is 
 more perfect than the last : dissolve the gold coin in 
 aqua regia as before ; then boil with excess of hydrochlo- 
 ric acid to destroy the nitric acid, dilute largely with 
 distilled water, and add a filtered aqueous solution of com- 
 mon sulphate of iron (6 parts in 1 part of gold) ; collect 
 the precipitated gold, which is now free from copper ; re- 
 dissolve in aqua regia, and evaporate to dryness on a 
 water bath. 
 
 Avoid using ammonia to neutralize chloride of gold, as 
 it would be liable to occasion a deposit of " fulminating 
 gold/' the properties of which are described immediately 
 following. 
 
 Properties of Chloride of Gold. As sold in commerce it 
 usually contains excess of hydrochloric acid, and is then 
 of a bright yellow color ; but when neutral and somewhat 
 concentrated it is dark red (Leo ruler of the alchemists). 
 It gives no precipitate with carbonate of soda, unless heat 
 be applied ; the free hydrochloric acid present forms, with 
 the alkali, chloride of sodium, which unites with the chlo- 
 ride of gold, and produces a double salt, chloride of gold 
 and sodium, soluble in water. 
 
 Chloride of gold is decomposed with precipitation of 
 metallic gold by charcoal, sulphurous acid, and many of 
 the vegetable acids ; also by protosulphate and protoni- 
 trate cf iron. It tinges the cuticle of an indelible purple 
 tint. It is soluble in alcohol and in ether. 
 
 GOLD, FULMINATING. 
 
 This is a yellowish-brown substance, precipitated on 
 adding ammonia to a strong solution of chloride of gold. 
 
PHOTOGRAPHIC CHEMICALS. 85 
 
 It ra'ay be dried carefully at 212, but explodes violently 
 mi being heated suddenly about to 290. Friction also 
 causes it to explode when dry ; but the moist powder may 
 be rubbed or handled without danger. It is decomposed 
 by sulphuretted hydrogen. 
 
 Fulminating gold is probably an aurate of ammonia, 
 containing 2 atoms of ammonia to 1 atom of peroxide of 
 gold. 
 
 / 
 
 GOLD, HYPOSULPHITE OF. 
 Symbol, AuO S 2 2 . Atomic weight, 253. 
 
 Hyposulphite of gold is produced by the reaction of 
 chloride of gold upon hyposulphite of soda. 
 
 The salt sold in commerce as sel d'or is a double hypo- 
 sulphite of gold and soda, containing one atom of the for- 
 mer salt to three of the latter, with four atoms of water 
 of crystallization. It is formed by adding one part of 
 chloride of gold, in solution, to three parts of hyposulphite 
 of soda, and precipitating the resulting salt by alcohol ; 
 the chloride of gold must be added to the hyposulphite of 
 soda, and not the soda salt to the gold. 
 
 Properties.-^- Hyposulphite of gold is unstable and cannot 
 exist in an isolated state, quickly passing into sulphur, 
 sulphuric acid, and metallic gold. When combined with 
 excess of hyposulphite of soda in the form of sel d'or, it is 
 more permanent. 
 
 Sel d'or occurs crystallized in fine needles, which are 
 very soluble in water. The commercial article is often 
 impure, containing little else than hyposulphite of soda, 
 with a trace of gold. It may be analyzed by adding a 
 few drops of strong nitric acid (free from chlorine) diluting 
 
 5 
 
86 VOCABULARY G$ 
 
 with water, and afterwards collecting and igniting tlie yel- 
 low powder, which is metallic gold!. 
 
 GRAPE SUGAR. 
 Symbol, C 24 H 28 28 . Atomic weight, 36. 
 
 This modification of sugar, often termed granular sugar f 
 or gluecose, exists abundantly in the juice of grapes, and in 
 many other varieties of fruit. It forms the saccharine 
 concretion found in honey, raisins, dried figs, etc. It may 
 be produced artificially by the action of fermenting prin- 
 ciple's, and of dilute mineral acids, upon starch. 
 
 Properties.-^ Grape sugar crystallizes slowly and witfe 
 difficulty from a concentrated aqueous solution, in small 
 hemispherical nodules, which are hard, and feel gritty 
 between the teeth. It is much less sweet to the taste" 
 than cane sugar, and not so soluble in Water (1 part dis j 
 solves in 1^- of cold water). Grape sugar tends to absorb 
 oxygen, and hence it possesses the property of decompos- 
 ing the salts of the noble metals, and reducing them "by 
 degrees to the metallic state, even without the aid of light. 
 The action however in the case of nitrate of silver is slow? 
 unless the temperature be somewhat elevated. Cane 
 sugar does Hot possess these properties to an equal extenl f 
 and hence it is readily distinguished from the other variety .- 
 
 HONEY. 
 
 This substance contains two distinct kinds of sugar r 
 grape sugar, and an uncrystallizable substance analogous" 
 to, or identical with, the treacle found associated with com- 
 mon sugar in the cane juice. The agreeable taste of 
 honey probably depends upon the latter, but its reducing 
 
PHOTOGRAPHIC CHEMICALS. T 
 
 power on metallic oxides is due to thy former. Pure grapg 
 sugar can readily be obtained from inspissated honey, by 
 treating it with alcohol, which dissolves out the syrup, but 
 leave? the crystalline portion. 
 
 HYDROCHLORIC AciD; 
 Symbol, HC1. Atomic weight, 37- 
 
 ilydrbchloric acid is a volatile gas, which may be libe- 
 rated from the salts termed chlorides by the action of sul- 
 phuric acid* The acid, by its superior affinities^ removes 
 the base ; thus, =- 
 
 NaGl-h HO S0 3 NaO S0 3 +HCL 
 
 Properties. Abundantly soluble in water, forming the 1 
 liquid hydrochloric or muriatic acid of commerce. The 1 
 most concentrated solution of hydrochloric acid has a sp. 
 gr. 1-2, and contains about 40 per cent, of gas ; that com- 
 monly sold is somewhat weaker, sp; gr. 1-14=28 per cent; 
 teal acid. 
 
 Pure hydrochloric acid is colorless, and fumes in the 
 air. The yellow color of the commercial acid depends 
 upon the presence of traces bf perchldride of iron or 
 organic matter ; commercial muriatic ac"id also often con- 
 tains a portion of free chlorine and df sulphuric acid; 
 
 HYDRIOCIC Acim 
 Symbol, HI. Atomic weight, 127, 
 
 This is a gaseous compound of hydrogen and iddine, 
 corresponding in composition to the hydrochloric acid. It 
 cannot^ however, from its instability, be obtained in the 
 same manner, since, on distilling an iodide with sulphuric 
 
tciCAEULA&V O'K 
 
 acid, the hydriodic acid first formed is subsequently tie- 
 composed into iodine and hydrogen. An aqueous solution 
 o'f hydriodic acid is easily prepared by adding iodine to 
 water containing sulphuretted hydrogen gas ; a decora* 
 position takes place, and sulphur is set free ; thus : 
 HS + I=HI+S. 
 
 Properties.- Hydriodic acid is rery soluble in water,- 
 yielding a strongly acid liquid. The solution, colorless 
 at firstj soon becomes brown from decomposition, and libe- 
 ration of free iodine. It may be restored to its original 
 condition by adding solution of sulphuretted hy dreg-en. 
 
 HYDROSULPHURIC ACID. 
 Symbol, HS. Atomic weight; 17. 
 
 This substance, also known as sulphuretted hydrogen^ 
 is a gaseous compound of sulphur and hydrogen, analogous 
 in composition to hydrochloric and hydriodic acids. It is' 
 usually prepared by the action of dilute sulphuric acid 
 upon sulphuret of iron, the decomposition being similar to 
 that involved in the preparation of the hydrogen acids 
 generally ; = 
 
 FeS + HO SO 3 = F'eO S0 + HS t 
 
 Properties, Cold water absorbs three times its bulk of 
 hydrosulphuric acid, and acquires the peculiar putrid odor 
 and poisonous qualities of the gas. The solution is faintly 
 acid to test-paper, and becomes opalescent on keeping, 
 from gradual separation of sulphur. It is decomposed by 
 nitric acid, and also by chlorine and iodine". It precipi- 
 tates silver from its solutions, in the fdrm of black sul- 
 phuret of silver ; also copper, mercury, lead, etc. ; but 
 iron and other metals of that class are not affected, if the 
 
PHOTOGRAPHIC CHEMICALS. 89 
 
 liquid contains free acid. Hydrosulphuric acid is con- 
 stantly employed in the chemical laboratory for these and 
 other purposes. 
 
 HYDROSULPHATE OF AMMONIA. 
 Symbol, NH^-S HS. Atomic weight, 51. 
 
 The liquid known by this name, and formed by passing 
 sulphuretted hydrogen gas into ammonia, is a double 
 sulphuret' of hydrogen and ammonium. In the prepara- 
 tion, the passage of the gas is to be continued until the 
 solution gives no precipitate with sulphate of magnesia 
 and smells strongly of hydrosulphuric acid. 
 
 Properties. Colorless at first, but afterwards changes 
 to yellow, from liberation and subsequent solution of sul- 
 phur. Becomes milky on the addition of any acid. Pre- 
 cipitates, in the form of sulphuret, all the metals which 
 are affected by sulphuretted hydrogen, and, in addition, 
 those of the class to which iron, zinc, and manganese, 
 belong. 
 
 Hydrosulphate of ammonia is employed in photography 
 to darken the negative image, and also in the preparation 
 of iodide of ammonium ; the separation of silver from 
 hyposulphite solutions, etc. 
 
 HYPOSULPHITE OF SODA. 
 Symbol, NaO S 2 2 + 5 HO. Atomic weight, 125. 
 
 The hyposulphite of soda commonly employed by pho- 
 tographers is a neutral combination of hyposulphurous 
 acid and the alkali soda. It is selected as being more 
 
90 VOCABULARY OF 
 
 economical in preparation than any other hyposulphite 
 adapted for fixing. 
 
 Hyposulphite of soda occurs in the form of large trans- 
 lucent groups of crystals, which include five atoms of 
 water. These crystals are soluble in water almost to any 
 extent, the solution being attended with the production of 
 cold ; they have a nauseous and bitter taste. 
 
 HYPOSULPHITE OF GOLD. 
 (See Gold, Hyposulphite of.) 
 
 HYPOSULPHITE OF SILVER. (See Silver, Hyposulphite of.) 
 ICELAND Moss. 
 
 Cetraria Islandica. A species of lichen found in Ice- 
 land and the mountainous parts of Europe ; when boiled 
 in water, it first swells up, and then yields a substance 
 which gelatinizes on cooling. 
 
 It contains lichen starch ; a bitter principle soluble in 
 alcohol, termed " cetrarine ;" and common starch ; traces 
 of gallic acid and bitartrate of potash are also present. 
 
 IODINE. 
 
 Symbol, I. Atomic weight, 126. 
 
 Iodine is chiefly prepared at Glasgow, from kelp, which 
 is the fused ash obtained by burning seaweeds. The 
 waters of the ocean contain minute quantities of the 
 iodides of sodium and magnesium, which are separated 
 and stored up by the growing tissues of the marine plant. 
 
 Iii the preparation, the mother-liquor of kelp is evapo- 
 rated to dryness and distilled with sulphuric acid ; the 
 hydriodic acid first liberated is decomposed by the high 
 
PHOTOGRAPHIC CHEMICALS, 91 
 
 temperature, and fumes of iodine condense in the form of 
 opaque crystals. 
 
 Properties. Iodine has a bluish-black color and metallic 
 lustre ; it stains the skin yellow, and has a pungent smell, 
 like diluted chlorine. It is extremely volatile when 
 moist, boils at 350, and produces dense violet-colored 
 fumes, which condense in brilliant plates. Specific gravity 
 4'946. Iodine is very sparingly soluble in water, 1 part 
 requiring 7000'parts for perfect solution : even this minute 
 quantity however tinges the liquid of a brown color. Alco- 
 hol and ether dissolve it more abundantly, forming dark- 
 browii solutions. Iodine also dissolves freely in solutions 
 of the alkaline iodides, such as the iodide of potassium, of 
 sodium, and of ammonium. 
 
 Chemical Properties. Iodine belongs to the chlorine 
 group of elements, characterized by forming acids with 
 hydrogen, and combining extensively with the metals (see 
 chlorine). They are however comparatively indifferent to 
 oxygen, and also to each other. The iodides of the alka- 
 lies and alkaline earths are soluble in water; also those 
 of iron, zinc, cadmium, etc. The iodides of lead, silver, 
 and mercury are nearly or quite insoluble. 
 
 Iodine possesses the property of forming a compound of 
 a deep blue color with starch. In using this as a test, it is 
 necessary first to liberate the iodine (if in combination), 
 by means of chlorine, or nitric acid saturated with perox- 
 ide of nitrogen. The presence of alcohol or ether inter- 
 feres to a certain extent with the result. 
 
 IODIDE OF AMMONIUM. 
 Symbol, NH 4 I. Atomic weight, 144. 
 
 This salt may be prepared by adding carbonate of am- 
 
92 VOCABULARY OF 
 
 rnonia to iodide of iron, but more easily by the following- 
 process : A strong solution of hydrosulphate of ammonia 
 is first made, by passing sulphuretted hydrogen gas into 
 liquor ammonise. To this liquid iodine is added until the 
 whole of the sulphuret of ammonium has been converted 
 into iodide. When this point is reached, the solution at 
 once colors brown from solution of free iodine. On the 
 first addition of the iodine, an escape of sulphuretted hy- 
 drogen gas and a dense deposit of sulphur take place. 
 After the decomposition of the hydrosulphate of ammonia 
 is complete, a portion of hydriodic acid formed by the 
 mutual reaction of sulphuretted hydrogen and iodine 
 attacks any carbonate of ammonia which may be present, 
 and causes an effervescence. The effervescence being 
 over, the liquid is still acid to test-paper, from excess of 
 hydriodic acid ; it is to be cautiously neutralized with am- 
 monia, and evaporated by the heat of a water-bath to the 
 crystallizing point. 
 
 The crystals should be thoroughly dried over a dish of 
 sulphuric acid, and then sealed in small tubes containing 
 each about half a drachm of the salt ; by this means it 
 will be preserved colorless. 
 
 Iodide of ammonium is very soluble in alcohol, but it 
 is not advisable to keep it in solution, from the rapidity 
 with which it decomposes and becomes brown. 
 
 T}ie most common impurity of commercial iodide of 
 ammonium is sulphate of ammonia ; it is detected by its 
 sparing insolubility in alcohol. 
 
 IODIDE OF CADMIUM. 
 Symbol, Cdl. Atomic weight, 182. 
 
 This salt is formed by heating filings of metallic ead- 
 
PHOTOGRAPHIC CHI1MICALS. 93 
 
 miurn with iodine, or by mixing the two together with 
 addition of water. It is useful in iodizing collodion in- 
 tended for keeping, since it does not become brown from 
 liberation of free iodine with the same rapidity as the 
 alkaline iodides. 
 
 Iodide of cadmium is very soluble both in alcohol and 
 water ; the solution yielding on evaporation large six-sided 
 tables of a pearly lustre, which are permanent in the air. 
 The crystalline form of this salt is a sufficient criterion 
 of its purity. 
 
 IODIDE OF IROX. 
 
 Symbol, Fel. Atomic weight, 154. 
 
 Iodide of iron, in a fit state for photographic use, is 
 easily obtained by dissolving a drachm of iodine in an 
 ounce of proof spirit that is, a mixture of equal bulks 
 of spirits of wine and water and adding an excess of 
 iron filings. After a few hours, a green solution is ob- 
 tained without the aid of heat. The presence of metallic 
 iron in excess prevents the liberation of iodine and deposit 
 of peroxide of iron which would otherwise speedily occur. 
 It is very soluble in water and alcohol, but the solution 
 rapidly absorbs oxygen and deposits peroxide of iron ; 
 hence the importance of preserving it in contact with me- 
 tallic iron, with which the separated iodine may recom- 
 bine. By very careful evaporation, hydrated crystals of 
 .proto-iodide may be obtained, but the composition of the 
 solid salt usually sold under that name cannot be de- 
 pended on. 
 
 The periodide of iron, corresponding to the perchloride, 
 has not been examined, and it is doubtful if any such 
 compound exist,-;. 
 
94 VOCABULARl UF 
 
 IODIDE OF POTASSIUM. 
 Symbol, KI. Atomic weight, 166. 
 
 This salt is usually formed by dissolving iodine in so- 
 lution of potash until it begins to acquire a brown color ; 
 a mixture of iodide of potassium and iodate of potash 
 (KO 10 6 ) is thus formed ; but by evaporation and heating 
 to redness, the latter salt parts with its oxygen, and is 
 converted into iodide of potassium. 
 
 Properties. It forms cubic and prismatic crystals, which 
 should be hard, and very slightly or not at all deliquescent. 
 Soluble in less than an equal weight of water at 60 ; it 
 is also soluble in alcohol, but not in ether. The propor- 
 tion of iodide of potassium contained in a saturated alco- 
 holic solution, varies with the strength of the spirit, 
 
 with common spirits of wine, sp. gr. -836, it would be 
 about 8 grains to the drachm ; with alcohol rectified from 
 carbonate of potash, sp. gr. '823, 4 or 5 grains : with ab- 
 solute alcohol, 1 to 2 grains. The solution of iodide of 
 potassium is instantly colored brown by free chlorine ; also 
 very rapidly by peroxide of nitrogen ; ordinary acids, how- 
 ever, act less quickly, hydriodic acid being first formed, 
 and subsequently decomposing spontaneously. 
 
 Iodide of potassium, as sold in the shops, is often con- 
 taminated with various impurities. The first and most 
 remarkable is carbonate of potash. When a sample of io- 
 dide of potassium contains much carbonate of potash, it 
 forms small and imperfect crystals, which are strongly 
 alkaline to test-paper, and become moist on exposure to 
 the air, from the deliquescent nature of the alkaline car- 
 bonate. Sulphate of potash is also a common impurity ; it 
 may be detected by chloride of barium. 
 
PHOTOGRAPHIC CHEMICALS. 95 
 
 Chloride of potassium is another impurity ; it is detected 
 as follows : Precipitate the salt by an equal weight of 
 nitrate of silver, and treat the yellow mass with solution 
 of ammonia ; if any chloride of silver is present, it dis- 
 solves in the ammonia, and after nitration is re-precipi- 
 tated in white curds by the addition of an excess of pure 
 nitric acid. If the 'nitric acid employed is not pure, but 
 contains traces of free chlorine, the iodide of silver must 
 be well washed with distilled water before treating it 
 with ammonia, or the excess of free nitrate of silver dis- 
 solving in the ammonia would, on neutralizing, produce 
 chloride of silver, and so cause an error. 
 
 Iodide of potash is a fourth impurity often found in 
 iodide of potassium : to detect it, add a drop of dilute 
 sulphuric acid, or a crystal of citric acid, to the solution of 
 the iodide ; when, if much iodate be present, the liquid 
 will become yellow from liberation of free iodine. The 
 rationale of this reaction is as follows : The sulphuric 
 acid unites with the base of the salt, and liberates hydri- 
 odic acid (HI), a colorless compound; but if iodic acid 
 (10 -) be also present, it decomposes the hydriodic acid 
 first formed, oxidizing the hydrogen into water (HO), and 
 setting free the iodine. The immediate production of a 
 yellow color on adding a weak acid to aqueous solution of 
 iodide of potassium is, therefore, a proof of the presence 
 of an iodate. As iodate of potash is thought to render 
 collodion insensitive (?), this point should be attended to. 
 
 Iodide of potassium may be rendered very pure by re- 
 crystallizing from spirit, or by dissolving in strong alco- 
 hol of sp. gr. -823, in which sulphate, carbonate, and io- 
 date of potash are insoluble. The proportion of iodide 
 
96 VOCABULARY OF 
 
 of potassium contained in saturated alcoholic solutions 
 varies with the strength of the spirit. 
 
 Solution of chloride of barium is commonly used to de- 
 tect impurities in iodide of potassium ; it forms a white 
 precipitate if carbonate, iodate, or sulphate be present. 
 In the two former cases the precipitate dissolves on the 
 addition of pure dilute nitric acid, but in the latter it is 
 insoluble. The commercial iodide, however, is rarely so 
 pure as to remain quite clear on the addition of chloride 
 of barium, a mere opalescence, therefore, may be disre- 
 garded. 
 
 IODIDE OF SILVER. (See Silver, Iodide of.) 
 
 IRON, PROTOSULPHATE OF. 
 Symbol, FeO S0 3 -f- 7 HO. Atomic weight, 139. 
 
 This salt, often termed copperas or green vitriol, is a most 
 abundant substance, and used for a variety of purposes in 
 the arts. Commercial sulphate of iron, however, being 
 prepared on a large scale, requires recrystallization to ren- 
 der it sufficiently pure for photographic purposes. 
 
 Pure sulphate of iron occurs in the form of large, trans- 
 parent prismatic crystals, of a delicate green color : by ex- 
 posure to the air they gradually absorb oxygen and become 
 rusty on the surface. Solution of sulphate of iron, color- 
 less at first, afterwards changes to a red tint, and deposits 
 a brown powder ; this powder is a basic persulphate of 
 iron, that is, a persulphate containing an excess of the 
 oxide or base. By the addition of sulphuric or acetic acid 
 to the solution, the formation of a deposit is prevented, the 
 brown powder being soluble in acid liquids. 
 
 The crystals of sulphate of iron include a large quan- 
 
PHOTOGRAPHIC CHEMICALS. 97 
 
 tity of water of crystallization, a part of which they lose 
 by exposure to dry air. By a higher temperature, the salt 
 may be rendered perfectly anhydrous, in which state it 
 forms a white powder. 
 
 Aqueous solution of sulphate of iron absorbs the bin- 
 oxide of nitrogen, acquiring a deep olive-brown color : as 
 this gaseous binoxide is itself a reducing agent, the liquid 
 so formed has been proposed as a more energetic deve- 
 loper than the sulphate of iron alone. 
 
 IRON, PROTOXITRATE OF. 
 Symbol, FeO JS"0 5 + 7HO. Atomic weight, 153. 
 
 This salt, by careful evaporation in vacua over sulphu- 
 ric acid, forms transparent crystals, of a light green color, 
 and containing 7 atoms of water, like the protosulphate. 
 It is exceedingly unstable, and soon becomes red from 
 decomposition, unless preserved from contact with air. 
 
 The following process is commonly followed for prepar- 
 ing protonitrate of iron : 
 
 Take of nitrate of baryta 300 grains ; powder and dis- 
 solve by the aid of heat in three ounces of water ; then 
 throw in, by degrees, with constant stirring, crystallized 
 sulphate of iron, powdered, 320 grains. Continue to stir 
 for about live or ten minutes. Allow to cool, and filter 
 from the white deposit, which is the insoluble sulphate of 
 baryta. 
 
 In place of nitrate of baryta, the nitrate of lead may 
 be used (sulphate of lead being an insoluble salt), but the 
 quantity required will be different. The atomic weights 
 of nitrate of baryta and nitrate of lead are as 131 to 166 ; 
 consequently 300 grains of the former are equivalent to 
 380 grains of the latter. 
 
98 VOCABULARY OF 
 
 IRON, PERCHLORIDE OF. 
 Symbol, Fe a Cl 3 . Atomic weight, 164- 
 
 There are two chlorides of iron, corresponding in com- 
 position to the protoxide and the sesquioxide respectively. 
 The protochloride is very soluble in water, forming a 
 green solution, which precipitates a dirty white protoxide 
 on the addition of an alkali. The perchloride, on the 
 other hand, is dark brown, and gives a foxy-red precipi- 
 tate with alkalies. 
 
 Properties. Perchloride of iron may be obtained in the 
 solid form by heating iron wire in excess of chlorine ; it 
 condenses in the shape of brilliant and iridescent brown 
 crystals, which are volatile, and dissolve in water, the so- 
 lution being acid to test-paper. It is also soluble in alco- 
 hol, forming the tinctura ferri sesquicldoridi of the Pharma- 
 copeia. Commercial perchloride of iron ordinarily con- 
 tains an excess of hydrochloric acid. 
 
 LITMUS. 
 
 Litmus is a vegetable substance, prepared from various 
 lichens, which are principally collected on rocks adjoining 
 the sea. The coloring matter is extracted by a peculiar 
 process, and afterwards made up into a paste with chalk, 
 plaster of Paris, &c. 
 
 Litmus occurs in commerce in the form of small cubes, 
 of a fine violet color. In using it for the preparation of 
 test-papers, it is digested in hot water, and sheets of po- 
 rous paper are soaked in the blue liquid so formed. The 
 red papers are prepared at first in the same manner, but 
 afterwards placed in water which has been rendered 
 faintly acid with sulphuric or hydrochloric acid. 
 
PHOTOGRAPHIC CHEMICALS. 99 
 
 MERCURY, BICHLORIDE OF. 
 Symbol, HgCl 2 . Atomic weight, 274. 
 
 This salt, also called corrosive sublimate, and sometimes 
 chloride of mercury (the atomic weight of mercury being 
 halved), may be formed by heating mercury in excess of 
 chlorine, or, more economically, by subliming a mixture of 
 persulphate of mercury and chloride of sodium. 
 
 Properties. a very corrosive and poisonous salt, usually 
 sold in semi-transparent, crystalline masses, or in the 
 state of powder. Soluble in 16 parts of cold, and in 3 of 
 hot water ; more abundantly so in alcohol, and also in 
 ether. The solubility in water may be increased almost 
 to any extent by the addition of free hydrochloric acid. 
 
 The protochloride of mercury is an insoluble white 
 powder, commonly known under the name of calomel. 
 
 MILK. 
 
 The milk of herbivorous animals contains three princi- 
 pal constituents fatty matter, caseine, and sugar ; in ad- 
 dition to these, small quantities of the chloride of po- 
 tassium, and of phosphates of lime and magnesia, are 
 present. 
 
 The fatty matter is contained in small cells, and forms 
 the greater part of the cream which rises to the surface of 
 the milk on standing . hence skimmed rnilk is to be pre- 
 ferred for photographic use. 
 
 The second constituent, caseine, is an organic principle 
 somewhat analogous to albumen in composition and pro- 
 perties. Its aqueous solution however does not, like 
 albumen, coagulate on boiling, unless an acid be present, 
 which probably removes a small portion of alkali with 
 which the caseine was previously combined. The sub- 
 
100 VOCABULARY OF 
 
 stance termed " rennet," which is the dried stomach of the 
 calf, possesses the property of coagulating easeine,but the 
 exact mode of its action is unknown. Sherry wine is also 
 employed to curdle milk ; but brandy and other spirituous 
 liquids, when free from acid and astringent matter, have 
 no effect. 
 
 In all these cases a proportion of the caseine usually re- 
 mains in a soluble form in the whey ; but when the milk 
 is coagulated by the addition of acids, the quantity so left 
 is very small, and hence the use of the rennet is to be pre- 
 ferred, since the presence of caseine facilitates the reduc- 
 tion of the sensitive silver salts. 
 
 Caseine combines with oxide of silver in the same man- 
 ner as albumen, forming a white coagulurn, which becomes 
 brick-red on exposure to light. 
 
 Sugar of milk, the third principal constituent, differs 
 from both cane and grape sugar ; it may be obtained by 
 evaporating whey until crystallization begins to take place. 
 It is hard and gritty, and only slightly sweet ; slowly 
 soluble, without forming a syrup, in about two and a half 
 parts of boiling, and six of cold water. It does not fer- 
 ment and form alcohol on the addition of yeast, like grape 
 sugar, but by the action of decomposing animal matter is 
 converted into lactic acid. 
 
 When skimmed milk is exposed to the air for some 
 hours it gradually becomes sour, from lactic acid formed in 
 this way ; and if then heated to ebullition, the caseine 
 coagulates very perfectly. 
 
 NITRIC ACID. 
 
 Symbol, NO-. Atomic weight, 54. 
 Nitric acid, or aqua-fortis, is prepared by adding sul- 
 
PHOTOGRAPHIC CHEMICALS/ ' 101 
 
 phuric acid to nitrate of potash, and distilling the mixture 
 in a retort. Sulphate of potash and free nitric acid are 
 formed, the latter of which, being volatile, distils over in 
 combination with one atom of water previously united 
 with sulphuric acid. 
 
 Properties. Anhydrous nitric acid is a solid substance, 
 white and crystalline, but it cannot be prepared except by 
 an expensive and complicated process. 
 
 The concentrated liquid nitric acid contains 1 atom of 
 water, and has a sp. gr. of about 1*5 : if perfectly pure it 
 is colorless, but usually it has a slight yellow tint, from 
 partial decomposition into peroxide of nitrogen : it fumes 
 strongly in the air. 
 
 The strength of commercial nitric acid is subject to 
 much variation. An acid of sp. gr. 1 -42, containing about 
 4 atoms of water, is commonly met with. If the specific 
 gravity is much lower than this (less than 1'36), it will 
 scarcely be adapted for the preparation of peroxylme. 
 The yellow nitrous acid, so called, is a strong nitric acid 
 partially saturated with the brown vapors of peroxide of 
 nitrogen ; it has a high specific gravity, but this is somewhat 
 deceptive, being caused in part by the presence of the 
 peroxide. On mixing with sulphuric acid the color dis- 
 appears, a compound being formed which has been termed 
 a sulphate of nitrous acid. 
 
 Chemical properties. Nitric acid is a powerful oxidizing 
 agent ; it dissolves all the common metals, with the ex- 
 ception of gold and platinum. Animal substances, such 
 as the cuticle, nails, etc.. are tinged of a permanent yellow 
 color, arid deeply corroded by a prolonged application. 
 Nitric acid forms a numerous class of salts, all of which 
 arc soluble in water. Hence its presence cannot be deter- 
 
102 
 
 VOCABULARY OF 
 
 mined by any precipitating re-agent, in the same manner 
 as that of hydrochloric and sulphuric acid. 
 
 Impurities of Commercial Nitric Acid. These are prin- 
 cipally chlorine and sulphuric acid ; also peroxide of nitro- 
 gen, which tinges the acid yellow, as already described. 
 Chlorine is detected by diluting the acid with an equal 
 bulk of distilled water, and adding a few drops of nitrate 
 of silver, a milkiness, which is chloride of silver in sus- 
 pension, indicates the presence of chlorine. In testing 
 for sulphuric acid, dilute the nitric acid as before, and 
 drop in a single drop of solution of chloride of barium ; if 
 sulphuric acid be present, an insoluble precipitate of sul- 
 phate of baryta will be formed. 
 
 NITROUS ACID. (See Silver, Nitrate of.) 
 
 NITRATE OF POTASH. 
 Symbol, KG N0 5 . Atomic weight, 102. 
 
 This salt, also termed nitre or saltpetre, is an abundant 
 natural product, found effloresced upon the soil in certain 
 parts of the East Indies. It is also produced artificially in 
 what are called nitre-beds. 
 
 Nitrate of potash is an anhydrous salt, it contains 
 simply nitric acid and potash, without any water of crys- 
 tallization ; still, in many cases, a little water is retained 
 mechanically between the interstices of the crystals, and 
 therefore it is better to dry before use. This may be 
 done by laying it in a state of fine powder upon blotting- 
 paper, close to a fire, or upon a heated 'metallic plate, 
 
 NITRATE OF BARYTA. 
 Symbol, BaO N0 5 . Atomic weight, 131. 
 Nitrate of baryta forms octahedral crystals, which are 
 
PHOTOGRAPHIC CHEMICALS. 103 
 
 anhydrous. It is considerably less soluble than the chlo- 
 ride of barium, requiring 12 parts of cold and 4 of boiling 
 water for solution. It may be substituted for the nitrate 
 of lead in the preparation of protonitrate of iron. 
 
 NITRATE OF LEAD. 
 Symbol, PbO N0 5 . Atomic weight, 166. 
 
 Nitrate of lead is obtained by dissolving the metal, or 
 the oxide of lead, in excess of nitric acid, diluted with 2 
 parts of water. It crystallizes on evaporation in white 
 anhydrous tetrahedra and octahedra, which are hard, and 
 decrepitate on being heated ; they are soluble in 8 parts 
 of water at 60. 
 
 Nitrate of lead forms with sulphuric acid, or soluble sul- 
 phates, a white precipitate, which is the insoluble sulphate 
 of lead. The Iodide of lead is also very sparingly soluble 
 in water. 
 
 NITRATE of SILVER. (See Silver, Nitrate of.) 
 
 NITRO-HYDROCHLORIC ACID. 
 Symbol, N0 4 + Cl. 
 
 This liquid is the aqua-regia of the old alchemists. It 
 is produced by mixing nitric and hydrochloric acids : the 
 oxygen contained in the former combines with the hydro- 
 gen of the latter, forming water and liberating chlorine, 
 thus : 
 
 NO 5 + HC1 = N0 4 + HO + Cl. 
 The presence of free chlorine confers on the mixture the 
 
104 VOCABULARY OF 
 
 power of dissolving gold and platinum, which neither of 
 the two acids possesses separately. In preparing aqua- 
 regia it is usual to mix one part, by measure, of nitric 
 acid with four of hydrochloric acid, and to dilute with an 
 equal balk of water. The application of a gentle heat 
 assists the solution of the metal ; but if the temperature 
 rises to the boiling point, a violent effervescence and escape 
 of chlorine takes place. 
 
 OXYGEN, 
 
 Symbol, 0. Atomic weight, 8. 
 
 Oxygen gas may be obtained by heating nitrate of pot- 
 ash to redness, but in this case it is contaminated with a 
 portion of nitrogen. The salt termed chlorate of potash 
 (the composition of which is closely analogous to that of 
 the nitrate, chlorine being substituted for nitrogen) yields 
 abundance of pure oxygen gas on the application of heat, 
 leaving behind chloride of potassium. 
 
 Chemical Properties. Oxygen combines eagerly with 
 many of the chemical elements, forming oxides. This 
 chemical affinity however is not well seen when the ele- 
 mentary body is exposed to the action of oxygen in the 
 gaseous form. It is the nascent oxygen which acts most 
 powerfully as an oxidizer. By nascent oxygen is meant 
 oxygen on the point of separation from other elementary 
 atoms with which it was previously associated; it may 
 then be considered to be in the liquid form, and hence it 
 comes more perfectly into contact with the particles of the 
 body to be oxidized. 
 
 Illustrations of the superior chemical energy of nascent 
 oxygen are numerous, but none perhaps are more striking 
 
PHOTOGRAPHIC CHEMICALS. 105 
 
 than the mild and gradual oxidizing influence exerted by- 
 atmospheric air, as compared with the violent action cf 
 nitric acid and bodies of that class which contain oxygen ' 
 loosel combined. 
 
 This syrup of honey and vinegar is prepared as fol* 
 lows : Take of 
 
 Honey * 1 pound. 
 
 Acid, acetic, fortiss. (Beaufoy's acid) 11 drachms; 
 AYate.v - 13 drachms . 
 
 Stand the pot containing the honey in boiling water 
 tmtil a scum rises to the surface, which is to be removed 
 two or three times. Then add the acetic acid and water* 
 and skim once more if required. Allow to cool, and it 
 will be fit for use. 
 
 POTASH; 
 
 Symbol, KO + HO. Atomic weight, 5^. 
 
 Potash is obtained by separating the carbonic acid 
 from carbonate of potash by means of caustic lime. Lime 
 is a more feeble base than potash, but the carbonate of 
 lime, being insoluble in water, is at once formed on adding 
 milk of lime to a solution of carbonate of potash. 
 
 Properties: Usually met with in the form of solid 
 lumps, or in cylindrical sticks, which are formed by melt- 
 ing the potash and running it into a mould. It always 
 contain sbne atom of Water, which cannot be driven off by 
 the application of heat. 
 
 Potash is soluble almost to any extent in Water, much 
 heat being evolved. The solution is powerfully alkaline 
 and acts rapidly upon the skin ; it dissolves fatty and 
 
106 VOCABULARY 8F 
 
 resinous bodies, converting them into soaps; Solution b'i 4 
 potash absorbs carbonic acid quickly from the air, and 
 should therefore be preserved in stoppered bottles ; the 
 glass stoppers must be wiped occasionally, in order to pre- 
 vent them from becoming immovably fixed by the solvent 
 action of the potash upon the silica of the glass. 
 
 The liquor potasses of the London Pharmacopoeia has a 
 sp. gr. of 1-063, and contains about 5 per cent; of real 
 potash. It is usually contaminated with carbonate of pot- 
 ash, which causes it to effervesce on the addition of acids ? 
 also, to a less extent, with sulphate of potash, chloride of 
 potassium, silica^ etc, 
 
 POTASH, CARBONATE OF; 
 Symbol, KO COg. Atomic weight, tO; 
 
 The impure carbonate of potash, termed pcarlash, is ob- 
 tained from the ashes of wood and vegetable matter, hi 
 the same manner as carbonate of soda is prepared from 
 the ashes of seaweeds. Salts of potash and of soda ap- 
 pear essential to vegetation, and are absorbed and approxi- 
 mated by the living tissues of the plant. They exist in 
 the vegetable structure combined with organic acids in the 
 form of salts, like the oxalate, tartrate, etc., which when 
 burned are converted into carbonates. 
 
 Properties. The pearlash of commerce contains large 
 and variable quantities of chloride of potassium, sulphate* 
 of potash, etc. A purer carbonate is sold, which is free 
 from sulphates, and with only a trace of chlorides. Car- 
 bonate of potash is a strongly alkaline salt, deliquescent, 
 and soluble in twice its weight of cold water ; insoluble in 
 alcohol, and employed to deprive it of water- 
 
PHOTO'GRAPHIC CHEMICALS. lOf 
 
 PYROGALLIC ACID. 
 Symbol, C 8 H 4 4 ~ (Stenhouse). Atomic weight. 84. 
 
 The term pyro prefixed td gallic acid implies that the' 
 iiew substance is obtained by the action of heat upon that 
 "bddy. At a temperature df about 4lO Faht., gallic acid 
 is decomposed, and a white sublimate forms,; which con- 
 denses in lamellar 1 Crystals ; thig is pyrogallie acid. 
 
 Pyrogallic acid is very soluble in cold water, and in al- 
 cohol and ether ; the solution decomposes rind becomes 
 brown by exposure to the air. It gives an indigo blue 1 
 color with protosulphate df irdn, whie'h chariges to dark 
 green if any persulphate be present. 
 
 Although termed an acid, this substance is strictly neu- 
 tral ; it does not redden litmus-paper, aiid forms no salts, 
 The addition of potash dr soda decomposes pyrogallic acid,- 
 a't the same time increasing the attraction for oxygen ) 
 hence this mixture may conveniently be 1 employed for 
 absorbing the oxygen contained in atmospheric' air. The' 
 Compounds df silver arid gdld are reduced by pyrogallic 
 acid even more rapidly than by gallic acid, the reducing 
 agent absorbing the oxygen, and becoming Converted 
 into carbonic acid and a brown matter insoluble in water. 
 
 Commercial pyrogallic acid is often Contaminated with 
 empyreumatic oil, arid also with a black insoluble sub- 
 stance known as metagallic acid, which is formed when 1 
 the heat is raised above the proper temperature in thepro*- 
 cfess of manufacture. 
 
 SEL D'OR. (See Gold, Hyposulphite of.) 
 
 SILVER. 
 Symbol, Ag. Atomic weight, 108. 
 
 This metal, the luna or diana of the alchemis-ts, is found 
 
108 VOCABULARY OF 
 
 native in Peru and Mexico ; it occurs also in the forrri of 
 sulphuret of silver. 
 
 "When pure it has a sp. gr. of 10-5, and is very malleable 
 and ductile ; melts at a bright red heat. Silver does not 
 oxidize in the air, but when exposed to an impure atmos- 
 phere containing traces of sulphuretted hydrogen, it is 
 slowly tarnished from formation of sulphuret of silver. It 
 dissolves in sulphuric acid, but the best solvent is nitric 
 acid. 
 
 The standard coin of the realm is an alloy of silver and 
 copper, containing about one-eleVenth of the latter metal. 
 It may be converted into nitrate of silver, sufficiently pure 
 for photographic purposes, by dissolving it in nitric acid 
 and evaporating the solution to th.6 crystallizing point : or, 
 if the quantity be small, the solution may be boiled 
 down to complete dryness, and the residue fused strongly ; 
 which decomposes the nitrate of coppei*, but leaves the 
 greater portion of the silver salt unaffected. (N. B. 
 Hitrate of silver which has undergone fusion contains 
 nitrite of silver, and will require the addition of acetic 
 acid if used for preparing the "collodion sensitive film. :) 
 
 SILVER, AMJTONIO-NITRATE or. 
 
 Crystallized nitrate of silver absorbs amrnonaical gas 
 ra.pidly, with production of heat sufficient to fuse the re- 
 sulting compound, which is white, and consists of 100 
 parts of the nitrate + 29-5 of ammonia. The compoun 1 
 however which photographers employ under the name of 
 ammonio-nitrate of silver, may be viewed more simply as 
 a solution of 'the oxide of silver in ammonia, without re- 
 
PHOTOGRAPHIC CHEMICALS. 109 
 
 ference to the nitrate of ammonia necessarily produced in. 
 the reaction. 
 
 Very strong ammonia, in acting upon oxide of silver, 
 converts it into a black powder, termed fulminating silver, 
 which possesses the most dangerous explosive properties. 
 Its composition is uncertain. In preparing ammonio-ni- 
 trate of silver by the common process, the oxide first pre- 
 cipitated occasionally leaves a little black powder behind, 
 on re-solution ; this does not appear, however, according 
 to the observations of the author, to be fulminating silver. 
 
 In sensitizing salted paper by the ammonio-nitrate of 
 silver, free ammonia is necessarily formed. Thus : 
 
 Chloride of ammonium + oxide of silver in ammonia 
 = chloride of silver -{- ammonia -{- water, 
 
 SILVER, OXIDE OF. 
 Symbol, AgO. Atomic weight, 116. 
 
 If a little potash or ammonia be added to solution of 
 nitrate of silver, a brown substance is formed, which, on 
 standing, collects at the bottom of the vessel. This is 
 oxide of silver, displaced from its previous state of com- 
 bination with nitric acid by the stronger oxide, potash. 
 Oxide of silver is soluble to a very minute extent in pure 
 water, the solution possessing an alkaline reaction to lit- 
 mus ; it is easily dissolved by nitric or acetic acid, forming 
 a neutral nitrate or acetate ; also soluble in ammonia 
 (ammonio-nitrate of silver), and in nitrate of ammonia 
 hyposulphite of soda, and cyanide of potassium. Long 
 exposure to light converts it into a black substance, which 
 is probably a suboxide. 
 
 6 
 
HO VOCABULARY OF 
 
 Properties of the Suboxide of Silver. Suboxide of sil- 
 ver bears the same relation to the ordinary brown protox- 
 ide of silver that subchloride bears to protochloride of 
 silver. 
 
 It is a black powder, which assumes the metallic lustre 
 on rubbing, and when treated with dilute acids is resolved 
 into protoxide of silver which dissolves, and metallic 
 silver. 
 
 SILVER, CHLORIDE OF. 
 Symbol, AgCl. Atomic weight, 144. 
 
 Preparation of Chloride of Silver by double decomposi- 
 tion. In order to illustrate this, take a solution in water 
 of chloride of sodium or " common salt," and mix it with 
 a solution containing nitrate of silver ; immediately a 
 dense, curdy, white precipitate falls, which is the substance 
 in question. 
 
 In this reaction the elements change places ; the chlo- 
 rine leaves the sodium with which it was previously com- 
 bined, and crosses over to the silver ; the oxygen and ni- 
 tric acid are released from the silver, and unite with the 
 sodium: thus 
 
 Chloride of sodium + nitrate of silver 
 ^Chloride of silver -f- nitrate of soda. 
 
 This interchange of elements is termed by chemists 
 double decomposition. 
 
 The essential requirements in two salts intended for the 
 preparation of chloride of silver, are simply that the first 
 should contain chlorine, the second silver, and that both 
 should be soluble in water ; hence the chloride of potas- 
 sium or ammonium may be substituted for the chloride of 
 
PHOTOGRAPHIC CHEMICALS. Ill 
 
 sodium, and the sulphate or acetate for the nitrate of 
 silver. 
 
 In preparing chloride of silver by double decomposition, 
 the white clotty masses which first form must be washed 
 repeatedly with water, in order to free them from soluble 
 nitrate of soda, the other product of the change. When 
 this is done, the salt is in a pure state, and may be dried, 
 etc., in the usual way. 
 
 Properties of Chloride of Silver. Chloride of silver 
 differs in appearance from the nitrate of silver. It is not 
 met with in crystals, but forms a soft white powder resem- 
 bling common chalk or whiting. It is tasteless and inso- 
 luble in water ; unaffected by boiling with the strongest 
 nitric acid, but sparingly dissolved by concentrated hydro- 
 chloric acid. 
 
 Ammonia dissolves chloride of silver freely, as do solu- 
 tions of hyposulphite of soda and cyanide of potassium. 
 Concentrated solutions of alkaline chlorides, iodides, and 
 bromides are likewise solvents of chloride of silver, but 
 to a limited extent. 
 
 Dry chloride of silver heated to redness fuses, and con- 
 cretes on cooling into a tough and semi-transparent sub- 
 stance, which has been termed horn silver or luna cornea. 
 
 Placed in contact with metallic zinc or iron acidified 
 with dilute sulphuric acid, chloride of silver is reduced to 
 the metallic state, the chlorine passing to the other metal 
 under the decomposing influence of the galvanic current 
 which is established. 
 
 Preparation and properties of the Subchloride of Silver. 
 If a plate of polished silver be dipped in solution of per- 
 chloride of iron, or of bichloride of mercury, a Hack stain 
 is produced, the iron or mercury salt losing a portion of 
 
112 VOCABULARY OF 
 
 chlorine, which passes to the silver and converts it super- 
 ficially into subchloride of silver. This compound differs 
 from the white chloride of silver in containing less chlo- 
 rine and more of the metallic element ; the composition 
 of the latter being represented by the formula AgCL, that 
 of the former may perhaps be written as Ag 2 Cl. (?) 
 
 Subchloride of silver is interesting to the photographer 
 as corresponding in properties and composition with the 
 ordinary chloride of silver blackened by light. It is a 
 pulverulent substance of a bluish-black color, which is 
 decomposed by ammonia, hyposulphite of soda, and cya- 
 nide of potassium, into chloride of silver which dissolves, 
 and insoluble metallic silver. 
 
 SILVER, BROMIDE OF. 
 Symbol, AgBr. Atomic weight, 186. 
 
 This substance so closely resembles the corresponding 
 salts containing chlorine and iodine, that a short notice of 
 it will suffice. 
 
 Bromide of silver is prepared by exposing a silvered 
 plate to the vapor of bromine, or by adding solution of 
 bromide of potassium to nitrate of silver. It is an insolu- 
 ble substance, slightly yellow in color, and distinguished 
 from iodide of silver by dissolving in strong ammonia and 
 in chloride of ammonium. It is freely soluble in hyposul- 
 phite of soda and in cyanide of potassium. 
 
 SILVER, CITRATE OF. (See Citric Acid.) 
 
 SILVER, IODIDE OF. 
 Symbol, Agl. Atomic weight, 234. 
 
 Preparation and Properties of Iodide of Silver. Iodide 
 of silver may be formed in an analogous manner to the 
 
PHOTOGRAPHIC CHEMICALS. 113 
 
 Chloride, viz. by the direct action of the vapor of iodine 
 upon metallic silver, or by double decomposition between 
 solutions of iodide of potasssium and nitrate of silver. 
 
 When prepared by the latter mode it forms an impal- 
 pable powder, the color of which varies slightly with the 
 manner of precipitation. If the iodide of potassium be 
 in excess, the iodide of silver falls to the bottom of the 
 vessel nearly white ; but with an excess of nitrate of sil- 
 ver it is of a straw-yellow tint. This point may be no- 
 ticed, because the yellow salt is the one adapted for pho- 
 tographic use, the other being insensible to the influence 
 of light. 
 
 Iodide of silver is tasteless and inodorous ; insoluble in 
 water and in dilute nitric acid. It is scarcely dissolved by 
 ammonia, which serves to distinguish it from the chloride 
 of silver, freely soluble in that liquid. Hyposulphite of 
 soda and cyanide of potassium both dissolve iodide of sil- 
 ver ; it is also soluble in solutions of the alkaline bromides 
 and iodides. 
 
 SILVER, FLUORIDE OF. 
 Symbol, AgF. Atomic weight, 127. 
 
 This compound differs from those just described in being 
 soluble in water. The dry salt fuses on being heated, and 
 is reduced by a higher temperature, or by exposure to 
 light. 
 
 SILVER, SULPHURET OF. 
 Symbol, AgS. Atomic weight, 124. 
 
 This compound is formed by the action of sulphur upon 
 metallic silver, or of sulphuretted hydrogen, or hydrosul- 
 
114 VOCABULARY OF 
 
 phate of ammonia, upon the silver salts ; the decomposi- 
 tion of hyposulphite of silver also furnishes the black 
 sulphuret. 
 
 Sulphuret of silver is insoluble in water, and nearly so 
 in those substances which dissolve the chloride, bromide, 
 and iodide, such as ammonia, hyposulphites, cyanides, 
 etc. ; but it dissolves in nitric acid, being .converted into 
 soluble sulphate and nitrate of silver. 
 
 SILVER, NITRATE OF. 
 Symbol, AgO N0 5 . Atomic weight, 170. 
 
 Nitrate of silver is prepared by dissolving metallic sil- 
 ver in nitric acid. Nitric acid is a powerfully acid and 
 corrosive substance, containing two elementary bodies 
 united in definite proportions. These are nitrogen and 
 oxygen ; the latter being present in greatest quantity. 
 
 Nitric acid is a powerful solvent for the metallic bodies 
 generally. To illustrate its action in that particular, as 
 contrasted with other acids, place pieces of silver foil in 
 two test-tubes, the one containing dilute sulphuric, the 
 other dilute nitric acid ; on the application of heat a vio- 
 lent action soon commences in the latter, but the former 
 is unaffected. In order to understand the cause of the 
 difference, it must be borne in mind that when a metallic 
 substance dissolves in an acid, the nature of the solution 
 is unlike that of an aqueous solution of salt or sugar. If 
 you take salt water, and boil it down until the whole of 
 the water has evaporated, you obtain the salt again, with 
 properties the same as at first ; but if a similar experi- 
 ment be made with a solution of silver in nitric acid, the 
 result is different : in that case you do not get metallic 
 
PHOTOGRAPHIC CHEMICALS. 115 
 
 silver on evaporation, but silver combined with oxygen and 
 nitric acid, both of which are tightly retained, being, in 
 fact, in a state of chemical combination with the metal. 
 
 If we closely examine the effects produced by treating 
 silver with nitric acid, we find them to be of the following 
 nature : first, a certain amount of oxygen is imparted to 
 the metal, so as to form an oxide, and afterwards this oxide 
 dissolves in another portion of the nitric acid, producing 
 nitrate of the oxide, or, as it is shortly termed, nitrate of 
 silver. 
 
 It is therefore the instability of nitric acid, its proneness 
 to part with oxygen, which renders it superior to sulphu- 
 ric acid in the experiment of dissolving silver. Nitric 
 acid stands high in the list of " oxidizing agents," and it 
 is important that the photographer should bear this fact 
 in mind. 
 
 Properties of Nitrate of Silver. In the preparation of 
 nitrate of silver, when the metal has dissolved, the solu- 
 tion is boiled down in order to drive off the excess of ni- 
 tric acid, and set aside to crystallize. The salt, however, 
 as so obtained is still acid to test-paper, and requires either 
 re-crystallization, or a careful heating to about 300 Fah- 
 renheit, to render it perfectly neutral. 
 
 Pure nitrate of silver occurs in the form of white crys- 
 talline plates, which are very heavy and dissolve readily 
 in an equal weight of cold water. The solubility is much 
 lessened by the presence of free nitric acid, and in the 
 concentrated nitric acid the crystals are almost insoluble. 
 Boiling alcohol takes up about one-fourth part of its 
 weight of the crystallized nitrate, but deposits nearly the 
 whole on cooling. Nitrate of silver has an intensely bitter 
 and nauseous taste ; acting as a caustic, and corroding the 
 
116 VOCABULARY OF 
 
 skin by a prolonged application. Its aqueous solution is 
 perfectly neutral to test-paper. 
 
 Heated in a crucible the salt melts, and when poured 
 into a mould and solidified, forms the lunar caustic of com- 
 merce. At a still higher temperature it is decomposed, 
 and bubbles of oxygen gas are evolved. The melted mass, 
 cooled and dissolved in water, leaves behind a black pow- 
 der, and yields a solution which is faintly alkaline to test- 
 paper. The alkalinity depends upon the presence of ni- 
 trite of silver associated with excess of oxide, in the form 
 probably of a basic or sub-mtiite of silver.* 
 
 Solution of nitrate of silver is decomposed by iron, 
 zinc, copper, mercury, etc., the nitric acid and oxygen 
 passing to the other metal, and metallic silver being pre- 
 cipitated. 
 
 SILVER, NITRITE OF. 
 
 Symbol, AgO N0 3 . Atomic weight, 154. 
 
 Nitrite of silver is a compound of nitrous acid, or N0 3 , 
 with oxide of silver. It is formed by heating nitrate of 
 silver, so as to drive off a portion of its oxygen, or more 
 conveniently, by mixing nitrate of silver and nitrate of 
 potash in equal parts, fusing strongly, and dissolving in a 
 small quantity of boiling water ; on cooling, the nitrite 
 crystallizes out, and may be purified by pressing in blot- 
 ting paper. Mr. Hadow describes an economical method 
 of preparing nitrite of silver in quantity, viz. by heating 
 1 part of starch in 8 of nitric acid of 1*25 specific gra- 
 vity, and conducting the evolved gases into a solution of 
 
 * Nitrite of silver differs from the nitrate in containing less oxygen, and 
 is formed from it by the abstraction of two atoms of that element. 
 
PHOTOGRAPHIC CHEMICALS. 117 
 
 pure carbonate of soda until effervescence has ceased. 
 The nitrite of soda thus formed is afterwards added to 
 nitrate of silver in the usual way. 
 
 Properties. Nitrite of silver is soluble in 120 parts of 
 cold water ; easily soluble in boiling water, and crystal- 
 lizes, on cooling, in long slender needles. It has a certain 
 degree of affinity for oxygen, and tends to pass into the 
 condition of nitrate of silver ; but it is probable that its 
 photographic properties depend more upon a decomposi- 
 tion of the salt and liberation of nitrous acid. 
 
 Properties of Nitrous Acid. This substance possesses 
 very feeble acid properties, its salts being decomposed even 
 by acetic acid. It is an unstable body, and splits up, in 
 contact with water, into binoxide of nitrogen and nitric 
 acid. The peroxide of nitrogen, N0 4 , is also decomposed 
 by water and yields the same products. 
 
 SILVER, ACETATE OF. 
 Symbol, AgO (C 4 H 3 3 ). Atomic weight, 167. 
 
 This is a difficultly soluble salt, deposited in lamellar 
 crystals when an acetate is added to a strong solution of ni- 
 trate of silver. If acetic acid be used in place of an 
 acetate, the acetate of silver does not fall so readily, since 
 the nitric acid which would then be liberated impedes the 
 decomposition. 
 
 SILVER, HYPOSULPHITE OF. 
 Symbol, AgO S 2 2 . Atomic weight, 164. 
 
 In order to understand, more fully how decomposition of 
 hyposulphite of silver may affect the process of fixing, the 
 
118 VOCABULARY OF 
 
 peculiar properties of this salt should be studied. With 
 this view nitrate of silver and hyposulphite of soda may 
 be mixed in equivalent proportions, viz. about twenty-one 
 grains of the former salt to sixteen grains of the latter, 
 firss dissolving each in separate vessels in half an ounce 
 of distilled water. These solutions are to be added to 
 each other and well agitated ; immediately a dense depo- 
 sit forms, which is hyposulphite of silver. 
 
 At this point a curious series of changes commences. 
 The precipitate, at first white and curdy, soon alters in 
 color : it becomes canary-yellow, then of a rich orange- 
 yellow, afterwards liver-color, and finally black. The 
 rationale of these changes is explained to a certain extent 
 by studying the composition of the hyposulphite of silver. 
 
 The formula for this substance is as follows : 
 
 AgO S 2 2 . 
 
 But AgO S 2 2 plainly equals AgS, or sulphuret of silver, 
 and SO 3 , or sulphuric acid. The acid reaction assumed 
 by the supernatant liquid is due therefore to sulphuric 
 acid, and the black substance formed is sulphuret of sil- 
 ver. The yellow and orange-yellow compounds are earlier 
 stages of the decomposition, but their exact nature is un- 
 certain. 
 
 The instability of hyposulphite of silver is principally 
 seen when, it is in an isolated state : the presence of an 
 excess of hyposulphite of soda renders it more permanent, 
 by forming a double salt. 
 
 In fixing photographic prints this brown deposit of sul- 
 phuret of silver is very liable to form in the bath and upon 
 the picture ; particularly so when the temperature is high. 
 To obviate it observe the following directions : It is es- 
 
PHOTOGRAPHIC CHEMICALS. 119 
 
 pecially in the reaction between nitrate of silver and hypo- 
 sulphite of soda that the blackening is seen ; the chloride 
 and other insoluble salts of silver being dissolved, even to 
 saturation, without any decomposition of the hyposulphite 
 first formed. Hence, if the print be washed in water to 
 remove the soluble nitrate, a very much weaker fixing 
 bath than usual may be employed. This plan, however, 
 involving a little additional trouble, is, on that account, 
 often objected to, and, when such is the case, a concen- 
 trated solution of hyposulphite of soda must be used, in 
 order to dissolve off the white hyposulphite of silver before 
 it begins to decompose. When the proofs are taken at 
 once from the printing frame and immersed in a dilute 
 bath of hyposulphite (one part of the salt to six or eight of 
 water), a shade of brown may often be observed to pass 
 over the surface of the print, and a large deposit of sul- 
 phuret of silver soon forms as the result of this decompo- 
 sition. On the other hand, with a strong hyposulphite 
 bath there is little or no discoloration and the black depo- 
 sit is absent. 
 
 But even if, by a preliminary removal of the nitrate of 
 silver, the danger of blackening be in a great measure 
 obviated, yet the print must not be taken out of the fixing 
 bath too speedily, or some appearance of brown patches, 
 visible by transmitted light, may occur. 
 
 Each atom of nitrate of silver requires three atoms of 
 hyposulphite of soda to form the sweet and soluble double 
 salt, and hence, if the action be not continued sufficiently 
 long, another compound will be formed almost tasteless 
 and insoluble. Even immersion in a new bath of hypo- 
 sulphite of soda does not fix the print when once the yel- 
 low stage of decomposition has been established. Thif 
 
120 * VOCABULARY OF 
 
 yellow salt is insoluble in hyposulphite of soda, and con- 
 sequently remains in the paper. 
 
 SUGAR OF MILK. (See Milk.) 
 SULPHURETTED HYDROGEN. (See Hydrosnlphuric Acid.) 
 
 SULPHURIC ACID. 
 Symbol, S0 3 . Atomic weight, 40. 
 
 Sulphuric acid may "be formed by oxidizing sulphur with 
 boiling nitric acid ; but this plan would be too expensive 
 to be adopted on a large scale. The commercial process 
 for the manufacture of sulphuric acid is exceedingly inge- 
 nious and beautiful, but it involves reactions which are 
 too complicated to admit of a superficial explanation. The 
 sulphur is first burnt into gaseous sulphurous acid (S0 2 ), 
 and then, by the agency of binoxide of nitrogen gas, an 
 additional atom of oxygen is imparted from the atmos- 
 phere, so as to convert the S0 2 into S0 3 , or sulphuric 
 acid. 
 
 Properties. Anhydrous sulphuric acid is a white crys- 
 talline solid. The strongest liquid acid always contains 
 one atom of water, which is closely associated with it, and 
 cannot be driven off by the application of heat. 
 
 This mono-hydrated sulphuric acid, represented by the 
 formula HO S0 3 , is a dense fluid, having a specific gravity 
 of about T845 ; boils at 620, and distils without decom- 
 position. It is not volatile at common temperatures, and 
 therefore does not fume in the same manner as nitric or 
 hydrochloric acid. The concentrated acid may be cooled 
 down even to zero without solidifying ; but a weaker com- 
 
PHOTOGRAPHIC CHEMICALS. 121 
 
 pound, containing twice the quantity of water, and termed 
 glacial sulphuric acid, crystallizes at 40 Fahr. Sulphuric 
 acid is intensely acid and caustic, but it does not destroy 
 the skin or dissolve metals so readily as nitric acid. It 
 has an energetic attraction for water, and when the two 
 are mixed, condensation ensues, and much heat is evolved ; 
 four parts of acid and one of water produce a tempera- 
 ture equal to that of boiling water. Mixed with aqueous 
 nitric acid, it forms the compound known as nitro-sulphu- 
 ric acid. 
 
 Sulphuric acid possesses intense chemical powers, and 
 displaces the greater number of ordinary acids from their 
 salts. It chars organic substances, by removing the ele- 
 ments of water, and converts alcohol into ether in a simi- 
 lar manner. The strength of a given sample of sulphu- 
 ric acid may generally be calculated from its specific 
 gravity, and a table is given by Dr. Ure for that purpose. 
 
 Impurities of Commercial Sulphuric Acid. The liquid 
 acid sold as oil of vitriol is tolerably constant in compo- 
 sition, and seems to be as well adapted for photographic 
 use as the pure sulphuric acid, which is far more expen- 
 sive. The specific gravity should be about 1-836 at 60. 
 If a drop, evaporated upon platinum foil, gives a fixed resi 
 due, probably bisulphate of potash is present. A milkiness, 
 on dilution, indicates sulphate of lead. 
 
 Test for Sulphuric Acid. If the presence of sulphuric 
 acid, or a soluble sulphate, be suspected in any liquid, it 
 is tested for by adding a few drops of dilute solution of 
 chloride of barium, or nitrate of baryta. A white preci- 
 pitate, insoluble in nitric acid, indicates sulphuric acid. If 
 the liquid to be tested is very acid, from nitric or hydro- 
 chloric acid, it must be largely diluted before testing, or a 
 
122 VOCABULARY OF 
 
 crystalline precipitate will form, caused by the sparing 
 solubility of the chloride of barium itself in acid solutions. 
 
 SULPHUROUS ACID. 
 Symbol, S0 2 . Atomic weight, 32. 
 
 This is a gaseous compound, formed by burning sulphur 
 in atmospheric air or oxygen gas ; also by heating oil of 
 vitriol in contact with metallic copper, or with charcoal. 
 
 When an acid of any kind is added to hyposulphite of 
 soda, sulphurous acid is formed as a product of the decom- 
 position of hyposulphurous acid, but it afterwards disap- 
 pears from the liquid by a secondary reaction, resulting in 
 the production of trithionate and tetrathionate of soda. 
 
 Properties. Sulphurous acid possesses a peculiar and 
 suffocating odor, familiar to all in the fumes of burning 
 sulphur. It is a feeble acid, and escapes with efferves- 
 cence, like carbonic acid, when its salts are treated with 
 oil of vitriol. It is soluble in water. 
 
 WATER. 
 Symbol, HO. Atomic weight, 9. 
 
 Water is an oxide of hydrogen, containing single atoms 
 of each of the gases. 
 
 Distilled water is water which has been vaporized and 
 again condensed : by this means it is freed from earthy 
 and saline impurities, which, not being volatile, are left 
 in the body of the retort. Pure distilled water leaves no 
 residue on evaporation, and should remain perfectly clear 
 on the addition of nitrate of silver, even when exposed to the 
 light ; it should also be neutral to test-paper. 
 
PHOTOGRAPHIC CHElVflCALS. 123 
 
 The condensed water of steam-boilers sold as distilled 
 water is apt to be contaminated with oily and empyreumatic 
 matter, which discolors nitrate of silver, and is therefore 
 injurious, 
 
 Rain-water, having undergone a natural process of dis- 
 tillation, is free from inorganic salts, but it usually con- 
 tains a minute portion of ammonia, which gives it an 
 alkaline reaction to test-paper. It is very good for photo- 
 graphic purposes if collected in clean vessels, but when 
 taken from a common rain-water tank should always be 
 examined, and if much organic matter be present, tinging 
 it of a brown color and imparting an unpleasant smell, it 
 must be rejected. 
 
 Spring or river water, commonly known as "hard 
 water," usually contains sulphate of lime, and carbonate 
 of lime dissolved in carbonic acid : also chloride of sodium 
 in greater or less quantity. On boiling the water, the 
 carbonic acid gas is evolved, and the greater part of the 
 carbonate of lime (if any is present) deposits, forming an 
 earthy incrustation on the boiler. 
 
 In testing water for sulphates and chlorides, acidify a 
 portion with a few drops of pure nitric acid, free from 
 chlorine (if this is not at hand, use pure acetic acid) ; then 
 divide it into two parts, and add to the first a dilute solu- 
 tion of chloride of barium, and to the second nitrate of 
 silver, a milkiness indicates the presence of sulphates in 
 the first case or of chlorides in the second. The photogra- 
 phic nitrate bath cannot be used as a test, since the iodide 
 of silver it contains is precipitated on dilution, giving a 
 milkiness which might be mistaken for chloride of silver. 
 
 Common hard water can often be used for making a 
 nitrate bath when nothing better is at hand. The chlo- 
 
124 VOCABULARY OF 
 
 rides it contains are precipitated by the nitrate of silver, 
 leaving soluble nitrates in solution, which are not inju- 
 rious. The carbonate of lime, if any is present, neutral- 
 izes free nitric acid, rendering the bath alkaline in the 
 same manner as carbonate of soda. Sulphate of lime, 
 usually present in well water, is said to exercise a retard- 
 ing action upon the sensitive silver salts, but on this point 
 the writer is unable to give certain information. 
 
 Hard water is not often sufficiently pure for the deve- 
 loping fluids. The chloride of sodium it contains decom- 
 poses the nitrate of silver upon the film, and the image 
 cannot be brought out perfectly. The New River water, 
 however supplied to many parts of London, is almost free 
 from chlorides and answers very well. In other cases a 
 ew drops of nitrate of silver solution may be added to 
 eparate the chlorine, taking care not to use a large excess. 
 
PHOTOGRAPHIC CHEMICALS. 125 
 
 BLACK VARNISH. 
 
 Asphaltum, dissolved in Spirits or Oil of Turpentine. 
 The asphaltum may be coarsely pulverized and put into 
 a bottle containing the turpentine, and in a few hours, if it 
 be occasionally shaken, it will be dissolved and ready lor 
 use. It should be of about the consistency of thick paste. 
 
 I use the above, but will now give two more composi- 
 tions, for any who may wish to adopt them : 
 
 Black Japan. Boil together a gallon of boiled linseed 
 oil, 8 ounces of amber, and 3 ounces of asphaltum. When 
 sufficiently cool, thin it with oil of turpentine. 
 
 Brunswick Black. Melt 4 Ibs. of asphaltum, add 2 Ibs. 
 of hot boiled linseed oil, and when sufficiently cool, add a 
 gallon of oil of turpentine. 
 
 The following is from Humphrey's Journal, Vol. viii, 
 number 16. 
 
 Black Varnish. I generally purchase this from the 
 dealer ; but I have made an article which answered the 
 purpose well, by dissolving pulverized asphaltum in 
 spirits of turpentine. Any of the black varnishes can be 
 improved by the addition of a little bees'-wax to it. It is 
 less liable to crack and gives an improved gloss. 
 
 Before closing this chapter, it has been thought advisa- 
 ble to remark, that one of the most important departments 
 of Photography is the practice of its chemistry. Many 
 of the annoying failures experienced by those who are 
 just engaging in the practice of the art, arise from the 
 want of good and pure chemical agents, and the most 
 
126 VOCABULARY OF PHOTOGRAPHIC CHEMICALS. 
 
 certain way to avoid this, is to purchase them only from 
 persons who thoroughly understand "both their nature and 
 mode of application. As many who may read this work 
 might wish to know the prices of the various articles 
 employed in the practice of the processes given, they can 
 be informed by ad Iressing the author, who will furnish 
 them with a printed Price List. 
 
PRACTICAL DETAILS 
 
 OF THE 
 
 POSITIVE 
 
 OR 
 
 AMBROTYPE PROCESS, 
 
CHAPTER IV. 
 
 LEWIS'S PATENT VICES FOR HOLDING THE GLASS CLEAN- 
 ING AND DRYING THE GLASS COATING EXPOSURE IN- 
 
 THE CAMERA DEVELOPING FIXING OR BRIGHTENING 
 
 BACKING UP, &C. 
 
 MANIPULATIONS. 
 
 Under the head of manipulations I give the method I 
 employ, and avoid confusion by omitting all comments 
 upon the thousand suggestions of others. 
 
 The glass is to have its sharp edges and corners removed, 
 by drawing a file once or twice over it. The article used 
 for holding the glass is called a vice. This vice is firmly 
 secured to a bench. 
 
 [Since the foregoing pages have been in type there has 
 been introduced into market a new patent vice, adopted 
 both for glass and plate blocks. I find it, although a 
 little more expensive, an article better suited to the 
 wants of the operator or amateur. It is called Lewis's 
 Patent Glass Vice.] 
 
 Clasp the glass firmly in the vice, and pour or spurt 
 upon it a little alcohol and rotten stone, previously formed 
 into a paste, and then, with a piece of cotton flannel, the 
 same as used in the daguerreotype, rub the glass until it 
 is perfectly cleansed from all foreign substances, which 
 will soon be known by experience. The rotten stone 
 
130 MANIPULATIONS. 
 
 paste should not be allowed to dry while rubbing, as it is 
 more liable to scratch the glass. I use another small bot- 
 tle containing clear alcohol, which I spurt upon the glass, 
 to obviate the drying. 
 
 When the glass has been sufficiently cleaned, it should, 
 while wet, be put in a vessel of water for furture rinsing. 
 Clean, as before, as many plates of glass as may be re- 
 quired, and when enough are ready, rinse them off in 
 the water, and then in a quantity of clean water, or a run- 
 ning current, give them a second thorough rinsing, and 
 set them aside to drain. 
 
 A convenient method of doing this, is to drive two nails 
 horizontally into the wall or partition, a sufficient distance 
 apart (say about 2-1- inches) for the glass to rest on : the 
 upper corner of the glass should be placed against the 
 wall, and the extreme lower diagonal corner left hanging 
 between the nails which will probably be found the best 
 position for draining yet suggested. 
 
 After drying, they may be put into a box for safe and 
 clean keeping. Particular caution is necessary to avoid 
 handling the glass during the operation. I never take the 
 glass between my fingers, so that they come in con- 
 tact with both sides of it, except at one particular corner, 
 as at Figs. A and B. A quantity of glass prepared as 
 above, may be kept on hand for use two or three days, and 
 when wanted they should be again put into the vice* and 
 
 * The vice should be thoroughly cleansed, and no particles of rotten 
 stone, or other matter, be allowed to come in contact with the glass, as it 
 might adhere to the edges and wash off into the silvering bath, and ulti- 
 mately cause specks. Always remember that cleanliness is an indispen- 
 sable requisite in order to produce a good picture. 
 
MANIPULATIONS. 131 
 
 cleaned, first with cotton flannel wet with alcohol, and 
 then with dry flannel ; and then, at a temperature slightly 
 above that of the surrounding atmosphere, except in cases 
 where the thermometer stands above 70, it is ready for the 
 brush,* which should be carefully applied to each surface, 
 to free it from all particles of dust, and then it is ready for 
 the film of collodion. 
 
 The glass is held between the thumb and foiefinger of 
 the left hand by the corner 1, Fig. A., 3 and 4 towards 
 
 Fig. A. Fig. B. 
 
 and nearest the body, and as nearly level as possible. I 
 find this the best position to hold the glass ; as, in the case of 
 the larger ones, they can be rested on the end of the little 
 finger, which should be placed as near the edge as possi- 
 ble. Then, from the collodion vial, pour on the collodion, 
 commencing a little beyond the centre and towards 1, 
 continuing pouring in the same place until the collodion 
 nearly reaches the thumb the glass slightly inclined that 
 way ; then let the glass incline towards 4, and continue 
 to pour towards 2. 
 
 * One of the most desirable articles I have found for this purpose is the 
 wide (3 inch) flat camel's-hair brush often called a blender. 
 
132 MANIPULATIONS. 
 
 As soon as enough has been put on to liberally flow the 
 glass, rapidly and steadily raise corner 1, and hold it di- 
 rectly over 3, where the excess will flow ofl into the mouth 
 of the vial, which should be placed there to receive it. In 
 case of a speck of dust falling at the time of coating, it can 
 often be prevented from injuring the surface by changing 
 the direction of the flowing collodion, so as to stop it 
 in some place where it will not be seen when the picture 
 is finished. Now, with the thumb and finger of the right 
 hand, I wipe off any drops or lines of collodion that may 
 be found upon the outer edge or side of the glass, being 
 careful not to disturb that connected with the face. 
 
 When the coating has become sufficiently dry, so that 
 when I put my finger against it, it does not break the film, 
 but only leaves a print, I put it into the silvering bath 
 [see Fig. p. 34]. I generally try corners 2 and 3. The 
 time, from the first commencement of pouring on collodion 
 to its being put into the bath, should not exceed about 
 half a minute, at a temperature of 60. The finger 
 test is the best I have found. The glass is to be rested 
 on a dipper [see Fig. p. 34], and placed steadily and firmly 
 into the nitrate of silver bath this in a dark room. It 
 should not be allowed to rest for an instant as it is enter- 
 ing the solution, or it would cause a line. The time for 
 the glass to remain in the bath depends upon the age and 
 amount of silver the bath contains ; for a new solution, 
 from two to three minutes will be sufficient to give the 
 proper action. If it be old, three to five minutes will be 
 better. When it is properly coated, it can be raised up 
 and taken by the corner, and allowed to drain for a few 
 seconds, and then should be placed in the tablet, and is 
 ready for the camera. The time of exposure will depend 
 
POSITIVE PROCESS. 133 
 
 upon the amount of light present. If the bath is newly 
 mixed, and the collodion recently iodized, it should pro- 
 duce a sufficiently strong impression by an exposure of 
 about one-third of the time required for a daguerreotype. 
 If the collodion has been iodized some time, and the bath 
 is old, about one-half of the time necessary to produce a 
 daguerreian image will be required. 
 
 The plate should in no case be allowed to become dry 
 from the time it is taken from the bath up to the time of 
 pouring on the developer. At a temperature of about 70, 
 I have had the glass out of the bath ten minutes without 
 drying. After exposure, the glass should be taken again 
 into the dark room, and removed from the tablet and held 
 over a sink, pail, or basin and the developing solution 
 poured on it as follows : hold the glass between the 
 thumb and finger of the left hand, by the opposite end 
 corner from that in coating with collodion, i. e., 2, and let 
 3 and 4 be from you. 
 
 Commence pouring on the developing solution at the 
 end by the thumb, and let it flow quickly and evenly over 
 the entire surface, the first flooding washing off any excess 
 of nitrate of silver there may be about the edges or cor- 
 ners of the glass (if this silver is not washed off, it flows 
 over the edges and on the surface of the impression, pro- 
 ducing white wavy clouds of scum), and then hold the 
 glass as nearly level as possible, it having upon its sur- 
 face a thin covering of solution (care should be observed 
 not to pour the developing solution on the plate in one 
 place, as it would remove all the nitrate of silver and pre- 
 vent the development of the image, leaving only a dark 
 or black spot where it is poured on). Put down the bottle 
 containing the developing solution, and take up a quart 
 
 7 
 
134 MANIPULATIONS OF THE 
 
 pitcher previously filled with water, and as soon as the 
 outline of the image can be plainly seen by the weak or 
 subdued light of an oil or fluid lamp or candle, pour the 
 water over copiously and rapidly. Continue this until all 
 the iron solution has been removed. If this is not done, 
 the plate will be covered with blue scum on the applica- 
 tion of the washing solution. Then the glass can betaken 
 into a light room, and the iodide of silver coating washed 
 off with the cyanide solution, and then rinsed with clear 
 pure water, and stood in a position to drain and dry. I 
 place a little blotting paper under them : it aids in absorb- 
 ing the water, and facilitates the operation. 
 
 Place the face of the glass against the wall, in order to 
 prevent dust from falling upon it. I have often dried the 
 coating by holding or standing the glass adjacent to a 
 stove. A steady heat is advisable, as it leaves the surface 
 in a more perfect state, and free from any scum. After 
 the coating is perfectly dry, it is ready for the preserving 
 process. It should be warmed evenly, and when about 
 milk warm, " Humphrey's Collodion Gilding" is poured 
 on the image in precisely the same manner as the collo- 
 dion. In a few seconds the coating sets, and after three- 
 quarters of a minute, if it has not become dry, the blaze 
 of a spirit lamp may be applied to the back and it will 
 immediately become perfectly transparent, and nearly as 
 hard as the glass itself: the effect is fully equal, if not su- 
 perior, to that of chloride of gold in gilding the daguerreo- 
 type image. The surface becomes brilliant and perma- 
 nent. The back of the glass can now be wiped and 
 cleaned with paper or cloth, and gently warmed, and then 
 with a common small brush one coat of black varnish can 
 be applied. This brush should be drawn from side to side 
 
POSITIVE PROCESS. 135 
 
 across the glass, and on the side opposite to that which has 
 received the image. 
 
 This is in order not to make streaks in the coating of 
 varnish, but to have uniform lines across the entire length 
 or breadth of the glass. If the varnish is of the proper 
 consistency, it will flow into a smooth, even coating. 
 After this first coating is dry, apply a second in the same 
 manner, only in an opposite direction, so as to cross the 
 lines of the first, uniting at right angles ; when this last 
 coating is very nearly dry, a piece of paper, glazed black 
 on one side, and cut to the proper size, can be put next the 
 varnish ; it gives it a clean finish, at the same time that 
 it aids towards a dense blackening. 
 
 I sometimes apply the black varnish by flowing, in the 
 same mariner as in putting on the collodion. 
 
 This picture is to be colored and put up in the same 
 manner as the daguerreotype image, with a mat and glass. 
 The last glass may be dispensed with by first using the 
 collodion gilding, and then upon its surface apply the black 
 varnish, as before. In this case the image is seen through 
 the same glass it is on, and without being reversed : in 
 this case the mat goes on the outside of the glass. 
 
 When the image is seen through the glass upon which 
 it is taken, it cannot be colored with very great success, as 
 it cannot be seen through the reduced silver forming it. 
 This forms a more or less opaque surface ; but in point of 
 economy the single glass is preferable. Yet I would not 
 recommend such economy, for I consider that a good im- 
 pression ought to be well put up, and the welfare of the 
 art fully substantiates that consideration. 
 
 Many ways have been devised for putting up pictures 
 I have produced pleasing effects upon colored glasses : for 
 
136 MANIPULATIONS OF THE 
 
 instance, a picture on a light purple glass has a very pleas- 
 ing effect ; also in some other colors. I have also used 
 patent leather for backing the image. 
 
 I have produced curious and interesting results by 
 placing a piece of white paper, or coloring white the 
 back of the whites of the image, and then blackening 
 over or around this. By this means the whites are pre- 
 served very clear. 
 
 Positives for Pins, Lockets, etc. I employ mica for 
 floating the collodion on, as it can be as easily cut and 
 fitted ais the metallic plate in the daguerreotype ; and 
 positives taken upon fine, clear, transparent mica, are 
 fully equal to those taken upon glass, and yet they are 
 ambrotypes. 
 
 Mica is an article familiar to every one, as being used 
 in stoves, gratings, etc. 
 
 The method of using it, is to take the impression on a 
 thick piece, and then split it off, which can readily be 
 done in the most perfect, thin, transparent plates ; it is 
 equally as thin as tissue paper, and can be cut as easily. 
 The thickness of the piece upon which the impression is 
 taken is of no moment, since it can be reduced at pleasure 
 and is more easily handled while thick. 
 
POSITIVE PROCESS. 137 
 
 OBSERVATIONS ON THE POSITIVE COLLODION PROCESS. 
 
 FOGGING There are numerous causes which will pro- 
 duce fogging : the principal ones will be mentioned. One 
 is the admission of light upon the collodion. This may 
 be from a want of closeness of the dark room, the tablet,* 
 the camera, or by accidental exposure. The method to 
 locate the particular cause is to, first, when the glass is 
 
 * Since the foregoing pages have been in type an entirely new feature in 
 the line of apparatus has been introduced ; this is W. & W. H. Lewis's Pa- 
 tent Plate-holder with solid glass corners. These Holders have every requi- 
 site for excluding the light from the sensitive surface ; they are accompanied 
 with a " shut off," so that when the slide is drawn no light can reach the 
 glass. This, in connection with the unequalled advantage of the solid 
 corners, makes them the most desirable article for the Operator. Hum- 
 phrey' 's Journal, in referring to these Holders, says : 
 
 " We are always glad to note every step which our mechanics make to- 
 wards improvement on the apparatus used by our practical photographic 
 operators, and make the present announcement of one which has only to 
 be known to be readily understood, and to be seen to be appreciated. A 
 patent has recently been granted for making solid glass corners, which are 
 to be attached to plate-holders, and form the most perfect article that has 
 ever been introduced. Heretofore the operator has had the corners of his 
 plate-holders made with separate pieces of glass, cut so as to fit the corners 
 of his frames ; these are only glued or grooved in, and are constantly coming 
 apart, falling out, and annoying in many ways ; for our part, we never have 
 considered them as fit for use in any manner. We look upon the present 
 improvement as destined to entirely supersede all the methods heretofore 
 introduced. In this case the collodionized or albumenized plate can come 
 jn contact with no other substance than a single piece of glass, and conse- 
 quently there is far less liability of accident from either the staining of the 
 plate or breaking of the holder. The rapid favor this improvement has 
 gained already shows its great advantage over all other methods heretofore 
 employed." 
 
138 MANIPULATIONS OF THE 
 
 taken from the nitrate bath, let it stand for sufficient time 
 to drain, then pour on the developer, and if the coating 
 assumes a mistiness, or light-grey color, the fault is in the 
 dark room ; again, if the plate, after it has been treated 
 with the developer and fixed, is clear, then also the fault 
 is there. Now try the tablet in the same manner, and if 
 not there, try the camera, and the proper location will be 
 found. 
 
 " Decomposition by exposure to light or by long keeping, 
 even in the dark. The author conceives that it is possi- 
 ble for organic matter alone to produce, after a time, a 
 partial decomposition of solution of nitrate of silver, suf- 
 ficient to prevent it from being employed chemically neu- 
 tral, but probably not much interfering with its properties 
 in other respects. 
 
 " Use of rain water or of water containing carbonate of 
 silver being perfectly neutral and from nitric acid. This 
 difficulty is not a theoretical one only, but has actually 
 been experienced. Rain water usually contains ammonia, 
 and has a faint alkaline reaction. Pump water often 
 abounds with carbonate of lime, much of which, but not 
 the whole, is deposited on boiling. To remove the alka- 
 line condition, add acetic acid, one drop to half a pint of 
 the solution. 
 
 " Partial decomposition of the bath, by contact with 
 metallic iron, with hyposulphite of soda, or with any de- 
 veloping agent, even in small quantity. Also by the use 
 of accelerators, which injure the bath by degrees, and 
 eventually prevent its employment in an accurately neu- 
 tral state. 
 
 " Vapor of ammonia, or hydrosulphate of ammonia, 
 escaping into the developing room." 
 
POSITIVE PROCESS, 
 
 139 
 
 SPOTS. One principal cause of spots is dust. The ope- 
 rating room skould be kept as free from this as possible, 
 and instead of its being dusted, it should be wiped with a 
 damp eloth. Specks or flakes of iodide of silver are often 
 found in the nitrate bath. These sometimes occur by an 
 <tver-iodized collodion, and sometimes by collodion falling 
 off while being silvered. When this oeeura, the nitrate of 
 silver solution should be filtered. A new sponge or a tuft 
 of cotton is a good article to filter nitrate of silver solution 
 through. A small particle of light finding its way upon 
 the plate, will produce a spot. Another and very frequent 
 eause is, putting the slide of the tablet down rapidly, caus- 
 iiag it t spatter upon the plate the solution which has 
 drained off from it. This paper will be opaque when 
 viewed by reflected light, a^d dark when viewed 
 foy transmitted light. Occasionally a sort of transparent 
 spot will appear : this may be traced to a^want of sensi- 
 bility of the iodide of silver. Large transparent spots 
 frequently appear by the operator's pouring the developing 
 solution upon one place, and ivashing off the small quantity 
 of nitrate ef silver necessary t develope the image. This 
 will be easily detected, and can be obviated by flooding 
 the most of the surface cf the glass with a steady stream 
 of the developer. 
 
 STAI\ T S AND LIXES. If the glass be allowed to rest for 
 an instant with one portion of its surface in the silvering 
 colution and the other out of it, it would cause a streak 
 across ; hence the necessity of totally immersing it with 
 one firm, steady motion removing the glass before it has 
 been thoroughly wetted, and the ether and alcohol allowed 
 & uuiiorra action over the entire surface. A plate should 
 
140 POSITIVE PROCESS. 
 
 not be disturbed in the bath until it has been in a full 
 minute at least. 
 
 Irregular Lines are often caused by using the develop- 
 ing solution too strong, or by not pouring it evenly over 
 the plate at once. Should it be allowed to rest in its pro- 
 gress, if but for an instant, it will leave its line. Some- 
 times spangles of metallic silver appear : these are caused 
 by the presence of too much nitric acid in the developer 
 for the proportion of iodide in the film and the strength 
 of the bath. 
 
 There are other phases connected with the practice of 
 the positive process, which it would be almost impossible 
 to commit to paper, and cannot be so explained as to be 
 perfectly comprehended by the new experimenter. It is 
 absolutely necessary for all to observe every little point 
 noticed in the foregoing pages, and at the same time exer- 
 cise some good judgment, and no one need hesitate through 
 fear of not being successful. 
 
PRACTICAL DETAILS 
 
 OF THE 
 
 NEGATIVE PROCESS. 
 
CHAPTER V. 
 
 NEGATIVE PROCESS SOLUBLE COTTON PLAIN COLLODION 
 
 DEVELOPING SOLUTION RE-DEVELOPING SOLUTION 
 
 FIXING THE IMAGE FINISHING THE IMAGE NITRATE 
 
 OF SILVER BATH. 
 
 NEGATIVE PROCESS. 
 
 The manipulations and chemicals employed in the pro- 
 duction of the negative collodion pictures are very similar 
 to those already given for operating by the positive pro- 
 cess ; frequent reference will therefore necessarily be 
 made to portions of that process, as described in the pre- 
 ceding pages, and only such parts will be given here, as 
 do not correspond with the foregoing. 
 
 It is thought advisable to omit in this chapter every re- 
 ference that does not have a desired tendency to aid the 
 operator in the plain straightforward order of manipula- 
 tion. The negative process is fast becoming popular and 
 needs the attention of all who desire to keep pace with 
 the experiments in the art. Since the first edition of this 
 work it has been my pleasure to see many fine photogra- 
 phic specimens produced by the following process, and no 
 
144 MANIPULATIONS OF THE 
 
 one need fail, if he will carefully adhere to the details 
 given. 
 
 There perhaps may be circumstances making it advisa- 
 ble for some to have but one nitrate of silver solution for 
 both positive and negative collodion pictures : for such, a 
 process will be given in the following pages, which has 
 recently appeared in Humphrey's Journal, and is called, after 
 its author, the " Helio Process ," this is well adapted for 
 most purposes. 
 
 SOLUBLE COTTON. 
 
 The method for preparing this has been given in page 
 41. It is prepared in the same manner for both positives 
 and negatives. 
 
 PLAIN COLLODION. 
 
 The preparation of plain collodion employed is the same 
 as that described at page 53. 
 
 DEVELOPING SOLUTION FOR NEGATIVES. 
 
 Rain or distilled water -6 ounces 
 
 Proto-sulphate of iron 300 grains. 
 
 Acetic acid 2 ounces. 
 
 A little alcohol may be added to make it flow more evenly 
 over the plate say 1 oz. 
 
 This solution can be kept in a pint bottle, and should 
 have a funnel devoted solely to the purpose of filtering it. 
 One of the most convenient dishes for receiving this solu- 
 tion, when poured over the plate, is a bowl with a lip to 
 it, as it can be readily poured back into the funnel. 
 
NEGATIVE PROCESS. 145 
 
 The mode of employing this developer is the same as 
 that for positives, described at page 133. It may be used 
 an indefinite number of times, but should be kept clean ; 
 it soon assumes a red color. 
 
 RE-DEVELOPING SOLUTION. 
 
 This solution is for the purpose of giving increased in- 
 tensity to the negative, but as its use in the hands of be- 
 ginners is attended with some difficulty, I would not 
 recommend the operator to try it until he has had consi- 
 derable experience in the developing process, or he will 
 undoubtedly spoil his proofs. Its use requires promptness 
 of action and quick observation. 
 
 The following is the formula for its preparation : 
 
 Water - 4 ounces. 
 
 Bfcotosulphite of iron 400 grains. 
 
 Put this into a bottle, and when the crystals are dissolved, 
 it is ready for use. It should be kept filtered, and can be 
 used only once. Now in another bottle put 
 
 Water 4 ounces. 
 
 Citrate of silver 48 grains. 
 
 REMARKS. The impression is to be well washed after 
 the developing solution has been poured off, and then the 
 redeveloping solution (that portion containing the proto-sul- 
 phate of iron) can be poured on the plate being held per- 
 fectly level : the surface is completely covered ; the water 
 containing the nitrate of silver should then be poured 
 rapidly on, to mix with the iron, when the surface of the 
 impression will instantly commence to blacken ; and if the 
 
146 
 
 MANIPULATIONS OF THE 
 
 action be allowed to continue for a lengthened period, say 
 one minute, the impression will be ruined. 
 
 It is a matter worthy of notice, that there is no percep- 
 tible action when the iron solution is poured over the 
 glass ; but the action is very energetic the instant the ni- 
 trate of silver solution comes in contact with the iron salt 
 and the silver. 
 
 As soon as any change can be observed, after the re-de- 
 veloper has been poured over the plate, it should be 
 quickly and copiously washed off with clean water, and 
 then it is ready for the fixing process. 
 
 I would dissuade novices in the art from practising with 
 the re-developing solution, until they have first thoroughly 
 mastered the entire process of taking negatives. The de- 
 veloping solution is the only one used by operators gene- 
 rally, and will, with proper care, produce satisfactory re- 
 sults. 
 
 FIXING THE IMAGE. 
 
 Water - - 8 ounces. 
 
 Hyposulphite of soda - 4 ounces. 
 
 REMARKS. This is nearly a saturated solution. The 
 glass can be put in a dish and the solution poured over, or 
 held in the hand, in the same way as the plate in the da- 
 guerreotype process. It can readily be seen when a suf- 
 ficient action has been attained, as the unaltered bromo- 
 iodide of silver will be dissolved, leaving only the reduced 
 surface holding the image. 
 
 This action should not be continued too long, as it affects 
 the intensity of the picture, injuring it for printing. 
 
 The glass should be well washed by pouring over it 
 clean water, and then it can be stood away to dry, in a 
 
NEGATIVE PROCESS 147 
 
 nearly perpendicular position, on clean blotting paper, or 
 otherwise, as is most convenient ; when thoroughly dry, it 
 is ready for the finishing. 
 
 FINISHING THE IMAGE. 
 
 This is done with the same material, and in the same 
 manner, as that given for positives page 134. 
 
 REMARKS. The glass negatives, when not wanted for 
 use, should be carefully put aside in a box, and kept free 
 from dust and dampness : by so doing, it is believed that 
 they will remain good for any length of time. 
 
 NITRATE OF SILVER BATH. 
 
 This solution differs only from the positive bath, by 
 omitting the nitric acid : in all other respects it is precisely 
 the same, and is prepared by the same formula, as given 
 at page- 64. 
 
 This is called the neutral bath, and is best adapted to 
 the negative process. The nitrate of silver employed in 
 its preparation should be perfectly free from excess of 
 nitric acid, otherwise the whole solution will be slightly 
 acid. 
 
 If it should not be convenient to obtain nitrate of silver 
 without this objection, the acid may be neutralized by putting 
 into the solution a small quantity of common washing soda 
 say 1 grain to each 100 grains of nitrate of silver pre- 
 viously dissolved in about half an ounce of water. This 
 may be put in at the same time that the iodide of potas- 
 sium is, and it would save one filtration. 
 
 In twenty samples of nitrate of silver that I have tried 
 
148 NEGATIVE PROCESS. 
 
 the above quantity of soda has been found sufficient ; if, 
 however, the white precipitate first formed is re-dissolved 
 on shaking the mixture, free nitric acid is present, and 
 more of the soda may be added. 
 
 This bath will improve by age, and be less liable to fog 
 after having been in constant use for one or two weeks. 
 
 Operators who have the means, and design following 
 the art professionally, will find it to their advantage to 
 make from two to three times the quantity of solution they 
 require for immediate use : by this means they will be 
 enabled to replenish their stock, which may be used up or 
 otherwise lost. 
 
PRACTICAL DETAILS 
 
 OF THE 
 
 PRINTING PROCESS. 
 
CHAPTER VI. 
 
 PRINTING PROCESS SALTING PAPER SILVERING PAPER 
 
 PRINTING THE POSITIVE FIXING AND COLORING BATH 
 
 MOUNTING THE POSITIVE. 
 
 THE PRINTING PROCESS. 
 
 There is probably no department of the photographic 
 art where can be found an equal amount of variety, as 
 regards chemicals, manipulations, etc. The course adopted 
 in the commencement, of giving only one process for the 
 operator to work by and that a good one will be strictly 
 adhered to in this place. I have produced as good posi- 
 tives on paper by the following plan, as I have ever seen. 
 Should the reader wish more extensive acquaintance with 
 the printing processes, he is referred to HUMPHREY'S JOUR- 
 NAL. 
 
 SALTING PAPER. 
 
 Water 1 quart. 
 
 Muriate of ammonia 65 grains. 
 
 The water is put into a flat, gutta-percha, glass, or 
 earthen dish, and the muriate of ammonia is put into it, 
 and stirred until it is dissolved and is well mixed with the 
 water ; then proceed as follows : we will suppose we have 
 a gutta-percha dish sufficiently large to take in a sheet of 
 paper 8 by 10 inches, and about 1^ or 2 inches deep : 
 
152 .MANIPULATIONS OF THE 
 
 take hold of two corners of the paper with the thumb and 
 finger of each hand, and then draw the paper through the 
 solution, by passing it from one end of the dish to the 
 other, so that it will be wetted on both sides ; then turn- 
 ing it over in the same manner, draw it back, so that its 
 surface will be thoroughly moistened, but it is not neces- 
 sary to saturate the paper. Now the paper is ready for 
 drying, which may be done by hanging it on the edge of 
 a shelf by means of little tack nails put through it at the 
 same corners by which it was held in passing through the 
 salting solution. In order to prevent streaks, from form- 
 ing upon the paper, it is better to hang it in such a man- 
 ner that it cannot touch the shelf, except at the corners : 
 say the sheet is eight inches wide, and the tacks (which 
 are put through the corners) to be only five or six inches 
 apart, this will give the proper bend outwards, preventing 
 its contact with the shelf. This entire operation can be 
 performed in daylight, or otherwise as suits the conve- 
 nience of the operator. 
 
 This paper, when dry, should be laid between the folds 
 of blotting paper (filtering paper will answer), and may 
 be kept for any length of time, and is ready for the silver- 
 ing process. 
 
 SILVERING PAPER. 
 
 In silvering paper, I employ the ammonio-nitrate, which 
 is prepared as follows : 
 
 Water 2J ounces. 
 
 ? itrate of silver 75 grains. 
 
 Dissolve (in a 4-ounce vial) the nitrate of silver in the 
 water, and then pour one-fourth of the solution into an 
 
PRINTING PROCESS. 153 
 
 ounce graduate or any convenient vessel : this keep for 
 farther use in preventing the presence of an excess of 
 ammonia. Now, into the bottle containing the three- 
 fourths put about 4 drops of aqua-ammonia ; shake well 
 and a brown precipitate will be given. Continue adding 
 the ammonia, drop by drop, and shake after each addition, 
 until the brown precipitate is re-dissolved and the solution 
 is clear ; then pour back into the bottle the one-fourth 
 taken out at first : this will leave the solution slightly tur- 
 bid, and when so, there is no excess of ammonia which 
 would be objectionable. It may now be filtered through 
 filtering paper, and it (the clear liquid) is ready for use. 
 This should be kept in the dark, as it decomposes rapidly 
 when exposed to light. 
 
 The method of silvering the paper with ammonio-nitrate 
 of silver, is as follows : take a tuft of clean cotton, roll it 
 into a ball-shape, then wet it by holding it against the 
 mouth of the bottle containing the ammonio-nitrate, and 
 when well wet, apply it to the paper (which should be 
 placed flat on a clean board) by gently rubbing it over the 
 surface, care being taken not to roughen it. 
 
 If the solution has not been filtered for some time, it 
 would be advisable to pour a little on the centre of the 
 paper, and then distribute it over the surface by means of 
 the cotton, which is held in the fingers : by this last method 
 any sediment which may be in the bottom of the bottle is 
 prevented from getting upon the paper, and causing spots. 
 
 I have used a brush for the purpose of distributing the 
 solution, by which plan there is less liability of getting it 
 on the fingers and staining them. Care must be taken to 
 cover the entire surface of the paper, or there will be light 
 streaks, occasioned by the absence of the silvering solu- 
 tion. 
 
154 MANIPULATIONS OF THE 
 
 This want of silver will appear on the paper in light 
 parts, as seen in the accompanying cut : 
 
 Fig. 36. 
 
 After the paper has been perfectly coated, or washed 
 with the silvering solution, it should he placed in a per- 
 pendicular position to dry. I usually tack the paper on a 
 board of the requisite size, and then stand it on one edge 
 until it has drained and dried. As soon as dry, it is ready for 
 use. This paper will not keep more than twelve hours, 
 therefore the operator should silver in the morning the 
 quantity required for the day. It is imperatively neces- 
 sary that the silvered paper be kept in the dark. It is 
 extremely sensitive to light, and a very brief exposure of 
 the prepared sheet would render it unfit for USB. 
 
 PRINTING THE POSITIVE. 
 
 The several kinds of apparatus used for holding the 
 negative and the sensitive paper together, have already 
 been given on page 36, Figs. 31, 32, 33. The paper having 
 been salted and silvered, as just described, should be 
 placed on the pad of the printing frame or glasses, with 
 its sensitive surface up, and then the negative placed 
 
PRINTING PROCESS* 155 
 
 directly upon and in contact with it ; then it is to be fas- 
 tened together, when it will be ready for exposure to the 
 direct rays of the sun. From 10 to 40 seconds will be 
 found enough to give a sufficiently intense print. 
 
 The paper first changes to a slate color, and then to a 
 brown or copper color : when of a dark slate color is about 
 the proper time to take it out and immerse in the toning 
 bath. 
 
 FIXING AND COLORING BATH. 
 
 I have employed the proportions given by Mr. HARD- 
 WICH in his Photographic Chemistry, page 209 Hum- 
 phrey's American edition. 
 
 Solution of chloride of gold, a quantity equivalent to - 4 grains. 
 
 Nitrate of silver 30 " 
 
 Hyposulphite of soda - 2 ounces. 
 
 Water 8 
 
 " Dissolve the hyposulphite of soda in four ounces of 
 the water, the chloride of gold in three ounces, the nitrate 
 of silver in the remaining ounce ; then pour the diluted 
 chloride by degrees into the hyposulphite, stirring mean- 
 while with a glass rod ; and afterwards the nitrate of sil- 
 ver in the same way. This order of mixing the solution 
 is to be strictly observed ; if it were reversed, the hyposul- 
 phite of soda being added to the chloride of gold, the re- 
 sult would be the reduction of metallic gold. The differ- 
 ence depends upon the fact that the hyposulphite of gold 
 which is formed is an exceedingly unstable substance, and 
 cannot exist in contact with unaltered chloride of gold. It 
 is necessary that it should be dissolved by hyposulphite of 
 
156 MANIPULATIONS OF TttE 
 
 soda immediately on its formation, and so rendered more 
 permanent by conversion into a double salt of soda and 
 gold. 
 
 " The time of coloration depends much upon the quantity 
 of gold present, and may in some cases be extended to 
 many hours. The results of a few experiments, performed 
 roughly, appeared to indicate that the activity of this bath 
 is less affected by depression of temperature than those 
 prepared with tetrathionate. Certainly the injurious effects 
 of prolonged immersion are not so evident as with the 
 first two formulae : the purity of the whites remains unal- 
 tered for many hours if the bath is new, but with an old bath 
 there is a tendency to yellowness, which is probably 
 caused by the presence of sulphuretted hydrogen. Fresh 
 chloride of gold must be added from time to time, as it 
 appears to be required." 
 
 After the impression has remained in the toning bath a 
 sufficient length of time, it should be placed in a dish or 
 sink of clean water, which should be changed several 
 times floating for at least 12 hours ; then it may be 
 taken out and hung up to dry. 
 
 "TOUCHING." The coloring of a photograph forms no 
 part of my process : this is a matter to be given into the 
 hands of an artist, and when it bears the finishing touch 
 of his skill, it is no longer a photograph, but an oil or water- 
 color painting ; all the delicate workings of nature having 
 been lost or hidden under the colors. 
 
 A photograph may often be " touched" to advantage. 
 If, as is frequently the case, there be little white spots 
 on the face of the paper, they may be readily covered by 
 the application of a little India ink, with the point of a 
 wet pencil or fine small brush. 
 
PRINTING PROCESS. 157 
 
 MOUNTING OF POSITIVES. 
 
 This, though a small matter in itself, is worthy of great 
 attention. The durability of the proof depends much upon 
 the purity of the paste used in causing its adhesion to the 
 Bristol board. I have employed the following composition 
 with the most eminent success : 
 
 Gum arable ... ..... 2 ounces. 
 
 Gum tragacanth H " 
 
 Isinglass - - - H " 
 
 Sugar ... | < 
 
 Water - 3 pints. ' 
 
 These ingredients should all be dissolved, and then 
 boiled down to the proper consistency, by means of a 
 gentle heat. 
 
 I will give another composition, which will serve a 
 good purpose, and keep for a long time : 
 
 Water 8 ounces. 
 
 One table spoonful of wheat flour .... 
 
 Powdered alum 40 grains. 
 
 Powdered resin " 
 
 Brown sugar ounce. 
 
 Bi -chloride of mercury 20 grains. 
 
 This last composition may be more convenient for ope- 
 rators, and it will answer the purpose well. It is thought 
 by some to be the best and most durable paste yet prepared 
 for the purpose. 
 
FACTS WORTH MENTIONING. 
 
 The Poisonous Effects of cyanide of potassium upon 
 sores, may be obviated by immediately applying some of 
 the positive developing solution, described at page 62. By 
 this means much annoyance may be avoided to persons 
 afflicted with chapped or sore hands. 
 
 Bending Glass Rods or tubes can be easily done by 
 subjecting them to the blaze of a spirit lamp the same 
 as that used for gilding the daguerreotype. First hold the 
 rod just above the blaze, then gradually allow it to de- 
 scend into it, imparting to the rod a rotatory motion with 
 the finger and thumb : this will soon cause a softening of 
 the glass, when it may be bent to any desired shape. If 
 the ends are to be bent to form hooks, another small 
 piece of glass, or any warm metal, may be placed 
 upon the end, in the blaze of the lamp, and as soon as 
 thoroughly softened, it can be pressed or bent to form the 
 hook. By filing around a glass tube or rod, it may be 
 easily and safely broken at the desired point, by giving it 
 a sudden jerk between both hands, holding it close to the 
 encircled part. 
 
 Cementing Glass may be readily accomplished by 
 placing the two ends together in the blaze of the lamp, 
 and holding them there until they attain a sufficient de- 
 gree of heat to slightly fuse : when cool, the ends will be 
 found perfectly united. 
 
FACTS WORTH KNOWING. 159 
 
 The Background best adapted to positives is unbleached 
 muslin, such as is sold for sheeting, and can be found in 
 almost any dry goods' store : it should be from two to 
 three yards wide. A clouded appearance is given to the 
 background by merely marking it with charcoal, forming 
 streaks or " waves" resembling clouds. These come out 
 black, or dark, in the positive, and give a variegated ap- 
 pearance. The roughness of the marking does not matter, 
 since the background is generally a little out of the focus 
 of the lenses. Trees and other designs may be represented 
 in this matter. 
 
 Positive Collodion Pictures may be whitened by the use 
 of bichloride of mercury, thirty grains to one ounce of wa- 
 ter. After the picture has been developed, fixed and 
 washed, by the process given in the preceding pages, the 
 solution of bichloride of mercury may be poured over the 
 surface of the image : it almost immediately presents a 
 series of interesting changes in color. The surface at first 
 blackens but for a few minutes, when it begins to get 
 lighter, and gradually brightens to a pure white, inclining 
 to a blue. It should then be thoroughly washed and dried, 
 as usual. 
 
 Instantaneous Pictures may be taken by employing the 
 iodide of iron in the collodion. The best method with 
 which I am acquainted, is to have a saturated solution of 
 iodide of iron in alcohol, and drop one or two drops into 
 an ounce of the collodion (which has been previously 
 iodized) used in taking positives. This can be used at 
 once, as soon as mixed. No more of this collodion should 
 be prepared than is wanted for immediate use, as it" will 
 keep good for only a few hours. The saturated solution of 
 
160 FACTS WORTH KNOWING. 
 
 iodide of iron can be kept on hand ready for use at all 
 times. There should be an excess of the iodide in the 
 alcohol. The same accelerating effect is produced with 
 the negative collodion prepared in this way. 
 
 Plain Collodion may be iodized as soon as dissolved : 
 this will save time in settling. It is a fact that some cot- 
 ton is more readily dissolved when the bromo-iodizing is 
 present : but by the addition of this, I have often taken up 
 considerable quantities of the gummy sediment remaining 
 in the bottom of bottles. 
 
 Prepared Glass may be preserved clean and free from 
 dust by keeping in boxes such as those used for keeping 
 daguerreotype plates. By taking out every other partition 
 between the grooves, the glass can be readily put in. 
 
 Collodion Vials and Bottles, after having collodion in 
 them once, should be rinsed with alcohol and ether (in 
 the same proportions as employed for dissolving the cot- 
 ton), before using them a second time for that purpose. 
 Penuriousness in this respect would be bad policy. 
 
 Coating Large Glasses. A convenient method of doing 
 this is represented in the following illustration : 
 
 The glass is held by one corner, 2 ; the other corner, 4, is 
 
FACTS WORTH KNOWING. 161 
 
 rested on a table or bench, and the collodion poured on, so 
 that the excess may be poured off at 1. 
 
 Black Stains upon the hands, caused by nitrate of silver, 
 may be removed by moistening them and rubbing with a 
 lump of cyanuret of potassium. This salt is poisonous, if 
 used to a great extent [See page 139]. Another safer, but 
 more expensive plan, however, is to take a saturated solu- 
 tion of iodide of potassium in water, and then wash with 
 aitric acid diluted with two parts water. 
 
 Stains upon White Linen can be removed by washing 
 with a saturated solution of iodide of potassium containing 
 a little iodine ; then wash with water, and soak in a satu- 
 rated solution of hyposulphite of soda until the yellow 
 iodide of silver is dissolved. 
 
 The hands should always be washed after fixing a posi- 
 tive or negative picture, before again touching a glass to 
 be coated, or the dipper; this precaution is necessary, lest 
 any of the iron salt, or the hyposulphite, should get into 
 the silvering solution and spoil it. 
 
 In taking Collodion Pictures, it is always advisable for 
 the sitter to be arranged before the glass is taken from the 
 bath : this will save time and there will be less liability 
 of the collodion drying. 
 
 A Good Negative may be known by its possessing the 
 following characteristics : By transmitted light the figure 
 is bright, and appears to stand out from the glass ; the 
 dark shadows are clear, without any misty deposit of me- 
 tallic silver ; the high lights black almost to complete 
 opacity. 
 
162 FACTS WORTH KNOWING. 
 
 A Glass Coated with Collodion, if kept too long before 
 immersion in the bath, will not be equally sensitive over 
 its surface ; the parts most dry being the least sensitive. 
 
 Glass Pans, for Scales, can be procured by every one 
 at trifling expense : Take a watch crystal, and place in the 
 common metal pan ; balance this with lead, or any weight : 
 this can easily be kept clean, and is the most advisable 
 for weighing all deliquescent salts, and chemicals employed 
 in the collodion process. 
 
 Caution. Persons engaged in making collodion, and 
 using ether and alcohol, must bear in mind that these che- 
 micals are very inflammable ; hence extreme caution is ne- 
 cessary to avoid exposing them to the flame of a lamp or 
 candle. I have known of several serious accidents, of 
 recent date, all of which were caused by the imprudence 
 of the experimenter in the particular above mentioned. 
 
 Wipe the Plate-holder every time before the glass is put 
 into it : this will prevent spots, which might otherwise 
 occur from the presence of nitrate of silver solution which 
 drained from the plate previously used. These spots are 
 of an opaque yellowish tinge, and in shape resemble the 
 stain which would be occasioned by a splash of water. 
 
 Glass J 'or Positives. A good white or light-green glass 
 will answer for the collodion coating. Glass which con- 
 tains air-spots can be used, if it be placed in such a man- 
 ner as to let the light of the image come over them, as the 
 spots cannot be seen through the opaque surface. Only 
 the best white glass should be used for covering the pic- 
 ture. Some operators use the convex glass, which is very 
 clear, and answers the purpose. 
 
FACTS WORTH KNOWING. 163 
 
 The Nitrate of Silver Bath should be kept covered, ex- 
 cept when in. use. 
 
 If a Glass be Immersed too soon, streaks and waves will 
 be occasioned. These will be seen at the end of the plate 
 which is least dry : the coating is also more liable to peel 
 off. It should be borne in mind, however, that the peel- 
 ing of collodion is not always attributable to this cause. 
 
 Diffused Light in the Developing Roorn. In proportion as 
 the sensitiveness of the plates increases, greater care must 
 be exercised in thoroughly excluding all rays of white 
 light. With opalescent films, neutral, this cause of fog- 
 ging is more common than any other. 
 
 Tn the case of a portrait, if the features have an unnaturally 
 black and gloomy appearance, the dark portions of the 
 drapery, &c., being invisible, the picture has been under- 
 exposed in the camera. 
 
CHAPTER VII. 
 
 HELIO PROCESS.* 
 
 AN ENTIRE PROCESS FOR PRODUCING COLLODION POSI- 
 TIVES AND NEGATIVES WITH ONE BATH, AND IN MUCH 
 
 LESS TIME THAN BY ANY OTHER KNOWN PROCESS. B 
 
 HELIO. PHOTOGRAPHIC PATENTS. 
 
 Boston, Oct., 1856. 
 S. D. HUMPHREY. 
 
 Sir, As Humphrey's Journal is the only truly pro- 
 gressive and independent Photographic publication in 
 America, I feel it the duty of every one to aid its Editor 
 in furthering the interest of the amateur and practitioner 
 of the art ; and, suiting the action to the word, I present 
 the following Process as being worthy of confidence, and 
 having, in my hands, proved eminently satisfactory. I am 
 surprised to see that Operators and men respectably con- 
 nected with the practice of the Art should so far fall be- 
 neath the station of true artists as to advertise to catch 
 each other, or the verdant ones, by offering this or that 
 little improvement all " printed complete for five dollars." 
 As an amateur, and having the good of the science I love 
 at heart, I now contribute my mite for the benefit of all 
 
 * It has been thought advisable to publish in this work the Helio Process, 
 and I do so just as it appeared in Humphrey's Journal. S. D. H. 
 
HELIO PROCESS. 165 
 
 interested ; and, following the glorious example of G. B. C. 
 (who I hope we shall soon hear from again,) in your 
 last, I say God speed ! 
 
 I shall endeavor to be as minute and concise as possible, 
 so as to enable any one to adopt and successfully use my 
 processes. 
 
 Preparation of Soluble Cotton. I put into a wedge wood 
 mortar, twelve ounces, by weight, of dry and finely pul- 
 verized nitrate of potash (I use Dupont's refined), and add 
 to it twelve ounces, by measure, of good commercial sul- 
 phuric acid ; I mix these well together by the use of a 
 glass rod and pestel, so that it forms a paste ; I then add, 
 in small quantities at a time, about 325 grains of good 
 coarse cotton (this is according to your process), and knead 
 the mass well for from three to five minutes ; and then 
 cover the mortar with a piece of glass, and let it stand for 
 twenty or thirty minutes, by which time it will have been 
 sufficiently acted upon. Then the cotton is to be plunged 
 into a quantity of clean water and thoroughly washed in 
 a number of changes of water, so that when it is squeezed 
 between the folds of blue litmus-paper it will not redden 
 it ; this indicates that the acid has been washed out ; I 
 then place the cotton in a clean strong towel and wring 
 out all the water I can, then put it into alcohol, then wring 
 it again, and adopt your plan of not letting it become tho- 
 roughly dry. 
 
 The cotton being now ready for use, I dissolve it in the 
 following mixture, in a bottle of proper size : 
 
 Sulphuric ether 10 ounces. 
 
 Alcohol, 95 per cent. - ... 5 ounces. 
 
 Soluble cotton, enough to make it about as thick as cream. 
 
 The above should be well shaken, and then allowed to 
 
166 HELIO PROCESS. 
 
 stand for one or two days to settle. This constitutes rny 
 Plain Collodion, and should be poured off' into another bot- 
 tle, leaving the sediment behind. 
 
 Iodizing. For this purpose I employ the following pre- 
 paration : 
 
 A. Iodide of Silver. Dissolve fifty grains of nitrate of 
 silver, crystals, in two ounces of pure water, 'and forty 
 grains of iodide of ammonium in two ounces of pure water ; 
 then pour the two together, shaking the mixture well ; let 
 it settle, which it will do in a few minutes ; then pour off 
 the water carefully, leaving behind all the yellow iodide 
 of silver ; pour again a fresh quantity of water over the 
 precipitate, and continue this washing for at least six 
 changes of water ; then drain off the water as close as pos- 
 sible and pour on two ounces of alcohol, which, when drained 
 off, will leave the powder sufficiently clean for the purpose. 
 
 B. I now dissolve forty grains of bromide of ammonium 
 and one hundred grains of iodide of ammonium in two 
 ounces of 95 per cent, alcohol, and then add the iodide of 
 silver (preparation A), and shake the whole well together, 
 giving a saturated solution. This is to be filtered through 
 cotton or paper, when it will be ready for use. 
 
 C. To sixteen ounces of Plain Collodion add from eight 
 to twelve drops of tincture of iodine (50 grains of dry 
 iodine dissolved in half an oz. of alcohol) and 14 grains 
 or drops of fluoride of ammonium ; shake the mixture 
 well ; then add all of the solution B ; shake it again and 
 thoroughly ; after this has stood for twenty-four hours it 
 can be used, but will be found better after it has been pre- 
 pared one week. 
 
HKUO PROCESS. 1G7 
 
 Nitrate of Silver Solution. 
 
 Pure rain or distilledjwater 32 ounces. 
 
 Nitrate of silver (in crystals) 4J ounces. 
 
 Clean pure white sugar 75 grains. 
 
 Six grains of iodide of ammonium dissolved in half a drachm of 
 alcohol. 
 
 The above, thoroughly mixed and allowed to stand for 
 a few hours, should be filtered through a new clean 
 sponge, asbestos, or Swedish filtering paper, and then a 
 few drops of nitric acid, chemically pure, should be added, 
 just enough to redden blue litmus-paper ; then it is ready 
 for use, and will improve by age. 
 
 Developing Solution. This formula has proved very 
 satisfactory in my hands, and I hope will be equally so 
 with all who give it a trial : 
 
 Water - 1 pint. 
 
 Boracic acid J ounce. 
 
 Proto-sulphate of iron f ounce. 
 
 Pulverized nitre - J ounce 
 
 Three drops of oil of cinnamon dissolved in two ounces of alcohol. 
 
 Dissolve and filter, and it is ready for use. It is better 
 to make this developer fresh every other day. 
 
 Dissolving off the Iodide of Silver. Water, about half a 
 pint ; cyanide of potassium, enough to clear the impression 
 in about thirty seconds say a quarter of an ounce. 
 
 Fixing the Impression. I use the article well known to 
 every good photographer as Humphrey's Collodion Gild- 
 ing, and it serves the purpose better than anything that I 
 I know of. 
 
168 HEL10 PROCESS. 
 
 Black Varnish. I generally purchase this from the 
 dealer ; but I have made an article which answered the 
 purpose well, by dissolving pulverized asphaltum in 
 spirits of turpentine. Any of the black varnishes can be 
 improved by the addition of a little bees'-wax to it. It is 
 less liable to crack and gives an improved gloss. 
 
 Negative and Printing Processes. Being myself an ama- 
 teur, and desiring to study economy and convenience, my 
 attention has been given to the test of numerous plans 
 for avoiding the necessity of two baths and silvering solu- 
 tions and I feel confident that the amateur will find the 
 following, in connection with the foregoing Positive Pro- 
 cess, the best adapted to his wants. 
 
 The same bath and solution is used for the negative, as 
 for the positive process ; and the time of exposure in the 
 camera should be prolonged a few seconds. I have produced 
 beautiful negatives, in-doors, in four seconds, and, out-doors, 
 instantaneously. The manipulation, bath, and developing 
 solution are precisely the same as those used in the posi- 
 tive process. 
 
 Fixing the Negative. Place the following mixture in a 
 well-stoppered bottle : 
 
 Pure Water .... - 6 ounces. 
 Aqua ammonia, concentrated 1 ounce. 
 
 This solution should be poured on the negative and 
 allowed to remain for about twenty seconds. It should 
 be borne in mind, that the developing solution (same as 
 for positives) should be well washed off the glass before 
 the fixing solution is poured over ; after it has remained 
 on the glass for the time given (20 seconds), the negative 
 can be washed with clean water and dried ; it is then 
 
HELIO PROCESS. 169 
 
 ready for printing. The iodide of silver is not, as in other 
 processes, dissolved off, but remains on the glass. 
 
 It sometimes happens that the negative is not sufficiently 
 intense ; this result can be obtained by pouring over the 
 plate the following solution, which should remain for 
 about three-fourths of a minute : 
 
 Water 8 ounces. 
 
 Nitrate of silver 28 grains. 
 
 Alcohol 1 ounce. 
 
 Loaf sugar ounce 
 
 After this solution is used, I pour over the impression 
 the developing solution, and then wash well with water. 
 This re-developing may be repeated two or three times, and 
 almost any desired intensity obtained. 
 
 Printing Process Salting the Paper. Boil the following 
 mixture in an earthen vessel until it becomes transpa- 
 rent : 
 
 Distilled water 12 ounces 
 
 Muriate of ammonia 240 grains. 
 
 Arrow root 112 grains. 
 
 After this has been sufficiently boiled, it should be 
 strained through clean linen or cotton cloth (free from 
 soap or other substances), and, when cool, it is ready for 
 coating the paper, which is done by dipping a new clean 
 sponge into it and rubbing it over one side of the paper, 
 giving it a uniform coating ; but as it is not desirable to 
 have too much on the paper, it should be rubbed with a clean 
 sponge until nearly dry ; it can then be hung up by the 
 corner until thoroughly dry, when it can be put into a 
 portfolio and kept for exciting for use. 
 
170 HELIO PROCESS. 
 
 Silvering Solution This solution may be prepared in 
 the light, but must be used in a dark room : 
 
 Distilled water 1 pint. 
 
 Nitrate of silver w - 3f ounces.^ 
 
 Dissolve and pour into an earthen or gutta-percha dish. 
 Take the paper (cut to the proper size) &n<i float it on this 
 solution for about three minutes ; care must be observed 
 that there are no air-bubbles between the solution and the 
 paper, for this would cause spots. It now can be hung up 
 to dry, and as soon as dry it may be used. Let me here 
 repeat, that this operation must be conducted in a dark 
 room. 
 
 Fixing and Toning Bath. I find that a better eflect is 
 produced if the positive be a little over-printed before be- 
 ing acted upon by the following mixture : 
 
 Distilled water 8 ounces. 
 
 Chloride of sodium 240 grains. 
 
 This solution should be put into a flat dish and the print 
 placed on it, face down, for from one and a-half to three 
 minutes, when it should be taken off and put into the fol- 
 lowing solution, and allowed to remain there from three 
 quarters of an hour to two hours : 
 
 Distilled water 18 ounces. 
 
 Hyposulphite of soda ...... 3 ounces. 
 
 titrate of silver 60 grains. 
 
 The following method should be observed in preparing 
 this last mixture, viz. : dissolve the three ounces of 
 hyposulphite of soda in sixteen ounces of the water and 
 
HELIO PROCESS. 171 
 
 the sixty grains of nitrate of silver in the remaining two 
 ounces ; then pour the nitrate of silver solution into that 
 containing the hyposulphite of soda, stirring the mixture 
 continually until all is well mixed. 
 
 After the print has remained in the toning solution for 
 the specified time, it should be taken out and well washed 
 in several changes of clean water, and dried and mounted 
 in any of the usual ways. 
 
 With a few general remarks I will close this, perhaps, 
 too long communication. It should he a point in the 
 practice of every one who desires success in any process, 
 to maintain a strict observance to cleanliness ; this is one 
 point in which most persons fail, and it cannot be too 
 strongly impressed upon the minds of manipulators. It 
 should be understood that the foregoing process is complete 
 in itself, and is not to be confounded with any other me- 
 thod. The collodion is adapted for the nitrate of silver 
 bath, and the lath for the collodion ; and no one should use 
 other preparations of collodion and silvering solution, except 
 they do so with the full expectation that it will be at the 
 loss of either or both of the preparations employed. 
 
 Allow me, through the columns of your invaluable 
 Journal, to say to those who may read the foregoing pro- 
 cess, that if they find (as I have) my process to prove 
 profitable to them, I shall consider myself amply repaid if 
 they will, through the same medium, contribute to our 
 stock of information by giving an account of their 
 experiments. I feel quite confident that some of the ama- 
 teurs, with whose reputation I am already acquainted, and 
 of whose private works in photography America has 
 cause to feel proud, could furnish interesting, useful and 
 valuable information upon this subject. Such men, for 
 
172 HELIO PROCESS. 
 
 instance, as G. B. C., of Md. (who has already made a 
 good beginning), G. W. D., of the same place, and Mr. C. 
 G., of Pa. Friends and co-laborers, shall we hear from 
 you ? I pause for a reply ! 
 
 I look with interest upon every stroke of the pen from 
 your able correspondent G. M., of Washington, whose 
 specimens of photographic engraving you recently had 
 the kindness to show me. I assure you, it did not a 
 little astonish me to witness the surprising truthfulness 
 with which the details were presented. 
 
 HELIO. 
 
CORRESPONDENCE 
 
 BETWEEN THE U. S, COMMISSIONER OF PATENTS AND JAMES 
 A. CUTTING, RELATIVE TO HIS APPLICATIONS FOR LETTERS 
 PATENT. 
 
 United States Patent Office, April 17, 1854. 
 
 Sir : Your application for letters patent for an alleged improve- 
 ment in making photographic pictures, having been submitted to 
 the proper examiner, is rejected. As the use of alcohol to absorb 
 water in hasty desiccation is understood to be commonly practical 
 in most chemical laboratories, no reference is thought necessary 
 for the rejection of the first claim. 
 
 Secondly, the mixture of alcohol and ether in unlimited pro- 
 portions to dissolve gun cotton for photographic purposes, is com- 
 mon. [See Gaudin's Process, ! Humphrey's Daguerreian Jour- 
 nal," vol. 4, p. 229.] 
 
 Thirdly, collodion with bromide basis, is not new. [See Gene- 
 ral Remarks on Collodion, by Gaudin. " Photographic Art Jour- 
 nal," 1st Series, vol. 6, p. 348.] 
 
 The two articles above referred to are translated from the 
 French, and contain also, it is believed, sufficient to show that 
 the subject of the fourth claim has been anticipated, rendering 
 further reference unnecessary. 
 
 Respectfully yours, &c., 
 
 S. F. SHUGERT, Acting Commissioner. 
 J. A. CUTTING (care of C.G. Page), Washington, D. C. 
 
 June 17, 1854. 
 
 SIR : Tn regard to the use of bromide bases with collodion, I 
 am prepared to show that I had it in successful use in the month 
 of April, 1853; and if the circumstances require legal proof of 
 the same, it will be furnished, though at some expense of time 
 and money to me; and as the question is only between the pub- 
 lic and myself, I trust the office will see fit to grant me a patent 
 for the same. JAMES A. CUTTING. 
 
 Hon. CIIAS. MASON, Commissioner of Patents. 
 
174 PHOTOGRAPHIC PATENTS. 
 
 United States Patent Office, April 19, 1854. 
 
 SIR : In your letter of the 17th, you say that, if necessary, 
 proof can be given that you had in successful use, in the month of 
 April, 1853, collodion prepared with a bromide basis. On refer- 
 ring to the " Journal of the Photographic Society," of London. 
 No. 6 (June, 1853), page 70, you will see that Sir John Herschei 
 used bromide for the same purpose previous to the year 1840. 
 Ammonia, in various combinations, has long been in use for the 
 preparation of sensitive collodions. [See Report of the British 
 Association, 1850, p. 150, " Journal of the Photographic Society/' 7 
 No. 9, 1853, p. 116.] F. M. Lyndes' process and compositions 
 show that he has used iodine, bromide, and chloride of ammonium ; 
 and Count de Montegon, in the same journal, No. 2, April, 1853. 
 page 24, for his fifth composition of collodion, used liquid ammo- 
 nia. These are all regarded as equivalents for your compositions 
 covered by the fourth claim ; if, however, there is a difference, 
 you are at liberty to show in what it consists; and the examina- 
 tion is accordingly postponed to await your action. 
 
 Yours ; &c., 
 
 C. MASON, Commissioner. 
 J. A. CUTTING (care of C. G. Page), Washington, D. C. 
 
 Washington, June 21, 1854. 
 
 SIR : In reply to your communications of the 19th instant, and 
 April 17th, 1854, I propose to modify my claims as follows, to 
 wit : 
 
 After the first clause of the claim, nineteenth line, ending with 
 the words " set forth," add as follows : " I do not claim the use 
 of alcohol as a desiccating agent, but limit my claim to its spe- 
 cial use and purpose, as herein stated." 
 
 Erase the fourth clause of the claim, commencing on the twenty- 
 sixth line, and ending with the words " set forth on the thirtieth 
 line. 
 
 In reply to the objection raised by the office that i: bromide 
 was used in 1840," I have to say that I was fully aware of the 
 employment of bromide in various ways for photographic pur- 
 poses, and that I have also, in common with photographers, known 
 the extreme difficulty of using bromide, and that notwithstand- 
 ing the sensitiveness imparted by bromide to other compounds, 
 it has been almost universally discarded by practical photogra- 
 phers. The discovery of collodion as a vehicle for sensitive mate- 
 rials is of recent date, and there seems to have been a back- 
 wardness on the part of photographers to attempt bromide bases 
 with collodion, and so far, whatever trials have been made sub- 
 
PHOTOGRAPHIC PATENTS. 175 
 
 sequent to my discovery, it is evident that they have been 
 attended with the results of " misty pictures/' To whatever 
 my success may be due, I maintain that I have been the first 
 to use a bromide base with collodion and with that only do I 
 claim it and the results in my pictures show with what success. 
 
 Respectfully, 
 
 JAMES A. CUTTING, 
 
 By Att'y, CHAS. G. PAGE. 
 Hon. CHAS. MASON, Commissioner of Patents. 
 
 United States Patent Office, June 21, 1854 
 
 SIR : Your specification of an improvement in composition for 
 producing photographic pictures is herewith returned for a slight 
 amendment, which is, to omit the reference to specimens which 
 do not accompany the patent, and to correct an error in the 
 oath as noted on the margin. 
 
 Yours, &c., 
 
 C. MASON, Commissioner. 
 JAMES A. CUTTING, 142 Hanover st., Boston, Mass. 
 
 United States Patent Office, June 22, 1854. 
 
 SIR: By reading a paper by Mr. W. Crookes in the "Journal 
 of the Photographic Society, London,' 7 No. 7, p. 86, "on the 
 employment of bromine in collodion," it is believed you will be 
 satisfied that the date there given on which he used bromized col- 
 lodion is prior to your claim to having used it ; he refers to p. 72, 
 No. 6, published in June, 1853, for experiments made with bro- 
 mized collodion, which paper is dated June 2d, 1853. Mr. Isaac 
 Rhen, of Philadelphia, has testified to having seen you make use 
 of a bromide base, viz., bromide of potassium and collodion, about 
 the 1st of July, 1853, or about one month after the date of Mr. 
 Crookes' paper in England. The specification is accordingly re- 
 turned, that you may cancel the fourth claim, and amend the 
 papers to suit. Yours, &c., 
 
 C. MASON, Commissioner. 
 
 Mr. J. A. CUTTING, (care of C. G. Page), Washington, D. C. 
 
176 PHOTOGRAPHIC PATENTS. 
 
 PATENT FOR THE USE OF CAMPHOR IN COMBINATION WITH 
 IODIZED COLLODION. 
 
 The schedule referred to in the Letters Patent, and making part 
 of the same. 
 
 To whom it may concern : 
 
 Be it known, that I, JAMES A. CUTTING, of the City of Boston, 
 County of Suffolk, and State of Massachusetts, have invented a 
 new and useful improvement in positive photographic pictures on 
 glass, and I do hereby declare the following to be an exact descrip- 
 tion thereof : 
 
 The nature of my invention consists in the use of gum camphor, 
 in addition to the existing materials in the preparation of collodion 
 
 for positive photographic pictures on glass. 
 
 To enable others skilled in the art to make and use my invention, 
 I will proceed to describe the process as follows : 
 
 Having prepared the collodion in the usual manner, I take a 
 pint bottle, in which I introduce twelve ounces of collodion, to 
 which I add one drachm of iodide of potassium, dissolved in alco- 
 hol. I then shake the mixture thoroughly, and add thereto eighteen 
 grains of refined gum camphor, shaking the mixture again, until 
 the whole is combined, then allow it to settle, when it is fit for 
 use. 
 
 The advantages of my improvement consist in the increased 
 vigor of the delineations of the half-tones of positive pictures on 
 glass, giving greater depth and rotundity thereto, which render 
 this combination exceedingly useful for microscopic pictures, as 
 well as the ordinary purposes of portraiture. 
 
 T would have it understood that the combination of camphor 
 with iodide of potassium and collodion, as above specified, is 
 adapted solely to the production of positive pictures on glass and 
 not to the production of negative pictures on glass, from which pos- 
 itive pictures on paper may be printed, as a sufficient degree of 
 opacity is not thus afforded for that purpose. 
 
 What I claim as my invention, and desire to secure by Letters 
 Patent, is the use of camphor, in combination with iodized 
 collodion, as set forth in the specification. 
 
 JAMES A. CUTTING. 
 
 SAMUEL GRUBB. 
 
 I.REHN. \ Witnesses. 
 
 Dated, July 4th, 1854. 
 
PHOTOGRAPHIC PATENTS. 177 
 
 PATENT FOR THE USE OF BALSAM FOR SEALING PHOTO- 
 GRAPHIC PICTURES ON GLASS. 
 
 The schedule referred to in Letters Patent and making part of 
 the same. 
 
 To whom it may concern : 
 
 Be it known that I, JAMES A. CUTTING, of Boston, in the Coun- 
 ty of Suffolk and State of Massachusetts, have invented new and 
 useful improvements in. photographic pictures on glass, and I do 
 hereby declare the following to be an exact description thereof: 
 
 The nature of my improvement consists in the application of a 
 coating of balsam of fir to the side of the glass on which the pic- 
 ture is made, over which coating I place another glass of equal size 
 with the one on which the picture is. 
 
 To enable others skilled in the art to make and use my inven- 
 tion. I will proceed to describe the process as follows : 
 
 After thoroughly cleaning a glass plate of the same size as that 
 on which the picture to be secured is made, and moving all dust 
 from the picture, I hold the glass containing the picture in a hori- 
 zontal position with the pictured side uppermost, then apply the 
 balsam in a line along one edge of the glass and placing one edge of the 
 second glass in close contact with the first, containing the balsam, 
 press them gradually together towards the opposite edge, causing 
 the balsamtoflow by a gentle pressure towards the opposite edge, 
 in this manner excluding all air from between the glasses ; then 
 by an even pressure exclude the superabundant balsam. The ad- 
 vantages of my improvements are, that by a mechanical combina- 
 tion of the balsam with the picture it is greatly increased in strength 
 and beauty, by an additional brilliancy and the exhibition of the 
 most minute delineations ; and by the application of the second 
 glass in combination with the balsam, the picture is hermetically 
 sealed and rendered entirely permanent, by being secured 
 from the influence of both air and moisture, and also from injury 
 by dust or other extraneous matter, or acid vapors, or any violence 
 less than what could occasion the fracture of the plate glass. 
 
 I am aware of the previous use of balsam for the cementing of 
 lenses and the securing of microscopic objects, and other like 
 purposes, and do not therefore extend my claim to any of these 
 uses ; but 
 
 What I claim as my invention, and desire to secure by Letters 
 Patent, is the combination of balsam with photographic pictures 
 on glass, and with additional glass by which they, with the bal- 
 sam, are hermetically sealed, as described in the specifications, and 
 for the purposes therein set forth, and for no other. 
 
 JAMES A. CUTTING. 
 
 ISAAC REHN, 
 
 SAMUEL GRUBB, 
 
 Dated July lith : 1854. 
 
178 PHOTOGRAPHIC PATENTS. 
 
 PATENT FOR DISPLACING WATER FROM SOLUBLE COTTON 
 BY THE USE OF ALCOHOL J ALSO, FOR THE USE OF BRO- 
 MIDE OF POTASSIUM IN COMBINATION WITH COLLODION. 
 
 The schedule referred to in these Letters Patent, and making 
 part of the same. 
 
 To all to whom these presents shall come : 
 
 Be it known that I, JAMES A. CUTTING, of Boston, in the 
 County of Suffolk and State of Massachusetts, have invented 
 certain improvements in making photographic pictures, and that 
 the following is a full, clear and exact description of the principle 
 or character which distinguishes them from all other things before 
 known, and of the usual manner of making, modifying, and 
 using the same. 
 
 My improvements relate to that class of photographic pictures 
 in which the pictures are obtained upon a prepared film of glass 
 or other substance. 
 
 The film which I employ is collodion, and in order to insure 
 success, the collodion must be prepared after my own process, as 
 follows: Take 3 ounces (Troy) of pure dry nitrate potassa, and 
 pulverize in a clean glass mortar ; add to this 2| ounces, fluid mea- 
 sure, of pure sulphuric acid, and stir the mixture with a glass rod ; 
 immerse in this liquid, 80 grains of clean, dry cotton, and knead 
 the mass of cotton in the liquid for about five minutes ; remove the 
 cotton and quickly wash it, till every trace of acid is gone, and 
 it must then be dried quickly -for I have discovered that the 
 more rapidly the cotton is dried, the more sensitive the collodion ; 
 and I have found the best effecls produced by displacing the water 
 from the cotton by strong alcohol. 
 
 To prepare the collodion, take 10 ounces concentrated sul- 
 phuric ether, 60 Baume. and mix this with 6 ounces of 95 per 
 cent, alcohol. To this mixture add the prepared cotton, in quan- 
 tity sufficient to make a collodion as thick as it can, and yet at 
 the same time flow evenly over the surface of glass. Let it set- 
 tle clear, and decant the solution. 
 
 In order to "excite" this collodion, take a deep 1 ounce vial 
 introduce 2i grains of bromide of potassium, and add water, 
 drop by drop, to make a saturated solution. In this solution 
 dissolve 2 grains of iodide of potassium, then add 1 ounce of 
 collodion, and shake well. Let it settle clear and decant for use. 
 
 The solution must be decanted every day. In order to make the 
 most sensitive collodion, I dissolve the bromide and iodide of potas- 
 
PHOTOGRAPHIC PATENTS. 179 
 
 pium and the collodion* in a saturated solution of carbonate of 
 ammonia in water. In using this collodion, pour it upon a clean 
 glass plate to form a film in the usual way, and as soon as the collo- 
 dion has set, and before it becomes dry, immerse the plate in a 
 bath of nitrate of silver, made with 30 grains of nitrate of silver, 
 2 grains of iodide of silver, and 1 ounce water. Take the plate 
 directly from the bath to the camera, and after sufficient exposure, 
 the plate is taken to a dark room to develope the impression with 
 the following solution : 'Take pyrogallic acid, 4 grains ; acetic acid, 
 No. 8, 1 ounce : dissolve and filter. For use, take of this liquid 1 
 drachms, diluted with 6| drachms of water, and when the impres- 
 sion is sufficiently developed, pour off the liquid, and immerse the 
 plate in a solution of the hyposulphite of soda, 4 ounces to the pint 
 of water. Wash the plate with pure water, and dry it in the usual 
 way. 
 
 The advantages of the above process are, the brief time required 
 to produce an impression, and the sharpness of the pictures. Por- 
 traits can be taken with as much facility as with the Daguerreo- 
 type, and the pictures are sharp and of excellent tone. The im- 
 pression thus obtained is negative, and the positive picture is pro- 
 duced in the usual way. I denominate this the mezzographic pro- 
 cess. 
 
 What I claim as my improvements in the process of obtaining 
 photographic pictures, are 
 
 First. Displacing the water from the cotton, for this purpose, 
 with strong alcohol, as set forth. I do not claim the use of alco- 
 hol as a desiccating agent, but limit my claim to its special use 
 and purpose, as herein stated. 
 
 Second. The employment of bromide of potassium in combina- 
 tion with collodion. 
 
 JAMES A. CUTTING. 
 
 T. CAMPBELL, > 
 
 SAMUEL GRUBB. 5 
 
 Dated July llth, 1854. 
 
 PATENT FOR THE USE OF JAPANNED SURFACES PREVIOUSLY 
 PREPARED UPON IRON OR OTHER METALLIC OR MINERAL 
 SHEETS OR PLATES IN THE COLLODION PROCESS. 
 
 To all whom it may concern : 
 
 Be it known that I, HAMILTON L. SMITH, of Gambier, in the 
 County of Knox, and State ot Ohio, have invented certain new and 
 
 * This is a mistake : the collodion is not to be dissolved in the " carbonate 
 of ammonia in water," but only the bromide and iodide of potassium. I called 
 Mr. Cutting's attention to this, and he said I was correct. S. D. H. 
 
180 PHOTOGRAPHIC PATENTS. 
 
 useful improvements in Photographic Pictures, and I do hereby 
 declare the following to be a full, clear, and exact description of the 
 same, and of the manner of making and. using my invention or dis- 
 covery. 
 
 The nature of rny invention or discovery relates to the taking of 
 positive pictures by the photographic process, upon a black japan- 
 ned surface prepared upon iron or any other metallic plates or 
 sheets, and consists in the use of collodion, and a solution of a salt 
 of silver, and an ordinary camera. 
 
 To enable others skilled in the art to make and use my inven- 
 tion. I will proceed to describe the manner of preparing and apply- 
 ing it which I have found to answer well in practice ; not confin- 
 ing myself, however, to the special process or processes herein 
 described, so long as the characteristics of the invention remain 
 the same. 
 
 I first take metallic sheets, preferring for the purpose iron, as 
 this metal is the only one, except the precious metals, which is 
 without action on the silver salts generally used, as also the other 
 chemicals; but other metallic or mineral sheets may be used, and 
 I do not, therefore, confine myself specially to any particular me- 
 tal. Upon each of the sheets is prepared a black japanned or 
 varnished surface, such as is used by tinners or japanners for coat- 
 ing metallic and other surfaces. The japan or varnish jjmay be 
 made and applied as follows : Take one quart of raw linseed oil ; 
 add to this two ounces of asphaltum and sufficient umber, or lamp 
 black, to give the desired shade. Boil these ingredients until a 
 portion dropped on a cool surface will remain in a round spot 
 without flowing away. It is then thick enough to use. If it 
 should be too thick, it can readily be thinned with spirits of tur- 
 pentine. Apply the japan to the sheets or plates with a brush, 
 and after allowing it to stand a short time, until the marks of the 
 brush disappear, place the sheets or plates in a drying oven and 
 submit them to heat until the surface will bear the finger to be 
 drawn over it without bringing off the japan ; it may, if found ne- 
 cessary, be coated again and treated in a similar way, and finally 
 polished with rotten-stone and oil, or other polishing material. 
 Other ingredients may be used in making the japan, such as mas- 
 tic, lac or copal varnish, and other shades of coloring matter may 
 be used. 
 
 By collodion I mean any solution of gun-cotton or pyroxyline ; 
 and by a solution of salt of silver, I mean any of the salts thereof 
 which can be used in photography for obtaining positive impres- 
 sions by a camera. 
 
 A japanned surface may be prepared on glass, or on leather and 
 other fibrous materials. Or glass may be made black by means of 
 
PHOTOGRAPHIC PATENTS. 181 
 
 coloring matter introduced or embodied with the glass, so as to be 
 in instead of on- the glass. But foreseeing the difficulty of embrac- 
 ing all these applications in one application, I do not desire to 
 have them so considered ; but reserve the right to hereafter apply 
 for such application of my general principle as I may deem essen- 
 tial, or of sufficient importance to be protected by Letters Patent. 
 And it might be proper to add, that vulcanized gutta-percha or 
 indurated rubber may be used as the basis upon which, or in which 
 the japanned surface may be made. The invention, however, 
 consists mainly on the surface, so that a silver picture may be 
 made upon it, said surface forming the back-ground of the picture. 
 
 The ingredients for fixing and developing the positive impression 
 upon the japanned surface may be the same as those heretofore 
 essayed by me in a former application, and need not again be re- 
 peated here. Though other chemicals, or other proportions of the 
 same chemicals, mav be used. 
 
 Having thus fully described the nature of my improvement in 
 photographic pictures, and shown how the same may be accom- 
 plished, what I claim therein as new and desire to secure by Let- 
 ters Patent, is:^ 
 
 The obtaining positive impressions upon a japanned surface pre- 
 viously prepared upon an iron or other metallic or mineral sheet or 
 plate, by means of collodion and a solution of a salt of silver and 
 a camera, substantially as herein described. 
 
 HAMILTON L. SMITH. 
 
 GEO. T. CHAPMAN, > w - 
 JAMES H. LEE. \ 
 
 Dated February, 19th, 1856. 
 
 PHOTOGRAPHIC PICTURES ON OIL. 
 
 To all whom it may concern : 
 
 Be it known that I, JOEL HAYWOOD TATUM, of the City of 
 Baltimore and State of Maryland, have discovered or invented a 
 
 new and useful preparation of oil ground or body, and mode of 
 
 9 
 
182 PHOTOGRAPHIC PATENTS. 
 
 preparing the same by which Photographic impressions, such as 
 portraits of all sizes, landscapes or still life may be produced upon 
 such oil prepared ground body or surface, whether upon canvass, 
 mill-board, pannel, or other body whatever, without any perma- 
 nent injury to such body, ground or surface for the reception of 
 colors in oil (water) or dry (paste), without impairing the texture, 
 quality, durability, or other desirable quality of the body ground, 
 or surface rendered so impressible, and give the following as the 
 Process used in accomplishing the result. 
 
 I take ordinary prepared canvass, mill-board, pannel or other 
 substance for the reception of oil painting by any composition of 
 oil (or oleaginous substance) and oxide of lead or zinc, Spanish 
 whiting, Fuller's earth, or their equivalents, singly or in combina- 
 tion, and after having removed all irregularities or lumps from 
 the surface I damp or wet the surface with spirits of wine, and 
 wipe clean : after which, I treat the surface with a solution of 
 potassium or any good alkali, regulating the strength to the amount 
 of oil in the body-ground or surface to be treated (ordinarily 1 oz. 
 of super, carb. soda to 1 pint of water), as soon as the surface has 
 uniformly changed color allow the surplus solution to run off, 
 wash off by pouring over the surface clean water, let dry, but not 
 by the fire or in the sun, as that would bring out the oil to the 
 surface. When dry, treat the surface again with a solution of the 
 chloride of sodium (of the strength ordinarily used and prescribed 
 for paper positives) ; decant from the surface the superfluous fluid 
 after a minute, and let dry. as before ; remove to a dark room, 
 and treat the surface with a solution of the nitrate of silver, its 
 strength being governed by the strength of impression desired, 
 usually 18 grains of nitrate of silver to 1 oz. of distilled water ; 
 allow the solution to float upon the surface a few moments to 
 insure uniformity of deposit, and then decant the surplus, in the 
 bottle or lath : place a small piece of filtering paper on the edge 
 'of the body, and place that, edge down, to facilitate the drainage ; 
 when dry, place the negative impression (which must previously 
 have been obtained, by the use of the camera, either ou collodion 
 
PHOTOGRAPHIC PATENTS. 183 
 
 or albumen upon glass or upon paper) upon the body or ground to 
 receive the impression in the position the picture is desired, with 
 the face of the negative to the surface of the body to receive the 
 impression. If the negative impression does not cover the whole 
 surface, then a mat should be used so as to extend to the edge 
 of the ground on all sides. Expose to the light, and, when suf- 
 ficiently long, remove the negative into a dark room (lighted with 
 a feeble lamp) ; dash over the impression a weak solution of 
 hyposulphite of soda, and let stand a few moments ; then wash 
 off with a very dilute acid of only sufficient strength to neutralize 
 the alkalies remaining upon the surface, usually five or six drops 
 of sulphuric acid to an oz. of water is sufficient. 
 
 What I claim as rny own invention and discovery, and desire to 
 secure by Letters Patent, is the mode of preparing and rendering 
 oil (oroleaginous) bodies, grounds, or surfaces impressible or sensi- 
 tive to the Photographic art by the temporary destruction or che- 
 mical change of the oil or oleaginous matter of the immediate 
 surface only, by the use of spirits of wine and alkaline solution, 
 or their equivalents, and, after fixing the impression by the use of 
 hyposulphate of soda, the use of dilute acid, by which last appli- 
 cation the alkalies are neutralized and the oil restored with the 
 impression permanent upon the surface. 
 
 Disclaiming everything heretofore known in the production of 
 Photographic pictures upon paper or any unoiled body or surface. 
 Witnesses. 
 
 J. S. HOLLINGSHEAD, ) 
 
 E. G. HANDY. j JOEL HAYWOOD TATUM. 
 
 Original, dated April, 15. 1856. 
 Re-issue, dated May 13, 1856. 
 
 PATENT FOR MAKING THE BORDER OF THE PICTURE TRANS- 
 PARENT, AND PLACING THE MAT BACK OF THE PICTURE. 
 
 To all whom it may concern : 
 
 Be it known that we, ALBERT BISBEE, of Columbus, in 
 the County of Franklin and State of Ohio, and Y. DAY, of Nash- 
 
184 PHOTOGRAPHIC PATENTS. 
 
 ville, in the County of Davidson and State of Tennessee, have in- 
 vented certain new and useful improvements in photographic 
 pictures on glass, and we do hereby declare the following to be a 
 full, clear and exact description of the same. 
 
 The nature of our invention consists in making the edges of the 
 coating or film on the glass transparent so that the picture is made 
 only on the central part of the glass, and extending so far as to 
 meet the inside edge of the mat or border, generally used in put- 
 ting up such pictures, and then placing the mat back of the pic- 
 ture. 
 
 To enable others skilled in the art to make and use our inven- 
 tion, we will proceed to describe the same as follows : 
 
 We place inside of the camera, and about one-tenth of the focal 
 distance of the lens from the glass, a board having an aperture of 
 any desired pattern that we wish the edges to have. This board 
 shades the edges of the glass, thereby leaving them transparent in 
 the picture. Then the picture, being taken in the usual manner, 
 is finished by varnishing with transparent white varnish, and then 
 backed with japan varnish, care being taken to have the japan on 
 the back extend only to meet the inside edges of the mat. Then 
 we place the mat back of the picture and secure it in its place with 
 the preserver. 
 
 If applied to the process, as patented by J. A. Cutting, with two 
 glasses, the picture is made as above described, and then the second 
 glass is applied, and finished as before by backing with japan. 
 
 The advantage of our improvement, is in having the mat pro- 
 tected from being soiled, and making the picture appear more round, 
 causing an illusion as though the picture or image was suspended 
 in the atmosphere, clear from the back-ground. 
 
 Having thus fully described the nature of our invention, what 
 we claim therein as new, and desire to secure by Letters Patent, is, 
 making the border of the picture transparent and placing the mat 
 back of the picture, as described in the above specification, and for 
 the purpose set forth. 
 
 Witnesses to the signature of 
 
 A. Bisbee. 
 
 C. A. BARKER, ) 
 
 WM. FIELD. $ A. BISBEE. 
 
 Witnesses to the signature of 
 Y. Day. 
 
 B. BlNGHAM, ) 
 
 W. ATKINS. j Y. DAY. 
 
 Dated May Nth, 1856. 
 
PHOTOGRAPHIC PATENTS. 185 
 
 PATENT FOR THE APPLICATION OF COLORING SUBSTANCES, 
 OR MATTER, TO PHOTOGRAPHIC IMPRESSIONS. 
 
 Be it known that I, GILES LANGDELL, and MARCUS A. ROOT, 
 of Philadelphia, in the State of Pennsylvania, have invented a 
 new and improved mode of coloring daguerreotype and other pho- 
 tographic portraits or pictures made on glass, metal or other mate- 
 rial ; and we do hereby declare that the following is a full and ex- 
 act description : 
 
 The nature of our invention or discovery consists in providing 
 and applying both mineral and vegetable coloring matters in solu~ 
 tion to the daguerreotype or any other photographic impression, in- 
 troducing the said coloring matter either into the collodion or the 
 developer, or by pouring upon the plate after the impression is fixed 
 by hyposulphite of soda, or the cyanide of potassium, or by any 
 other means. 
 
 The several coloring substances, E. G. red saunders, alkanet, 
 dragons' blood, &c., &c., can be used separately or in conjunction 
 or compounded with various mineral substances, or with any color- 
 ing matters obtained from other roots, woods, gums or other vege- 
 table matter, the proportions or quantity employed being varied 
 or regulated by the lightness or depth and strength of tone which 
 may, from time to time, be required. 
 
 The desired or similar results may be obtained from different 
 formulae. The following answers for all practical purposes ; but 
 may be varied at pleasure : 
 
 Digest for two or three days red saunders (pterocarpus santalinus) 
 half a pound in three pints of water to which the aqua ammonia 
 has been added. Then pour off the solution and precipitate by the 
 addition of nitric acid. Wash the precipitate thoroughly with wa- 
 ter and dry it. Then dissolve it in strong alcohol and dilute with 
 the same as required to produce the tone or tint that may be de- 
 sired. Alkanet (anchusa tinctoria) may be prepared in the same 
 way. Dragons' blood dissolved in alcohol and treated in the same 
 manner will produce the various shades of yellow. The foregoing 
 
186 PHOTOGRAPHIC PATENTS. 
 
 articles, and also madder, indigo, cochineal, arid some other color- 
 ing substances both vegetable and mineral alone or combined, will 
 produce pleasing results when applied as follows (although they 
 may be introduced into the collodion) : 
 
 We prefer first to develope the impression, then to fix and dry 
 it, and afterwards to flow on the toning or tinting solution, as col- 
 lodion or varnish, &c., is poured upon the plate, allowing the solu- 
 tion to run off the corner, and then levelling the plate to make the 
 fluid flow uniformly over and tint the whole surface of the plate 
 eve ly. 
 
 Then wash at once and thoroughly with clean water, and stand 
 the plate up to dry, after which it may be colored (the dress of any 
 tint or color desired the face, hands, &c, are flesh tint) with dry 
 colors (as is usual in coloring daguerreotypes) applied to the collo- 
 dion or upon the varnish. 
 
 What we claim as our invention and discovery, and desire to 
 secure by Letters Patent, is the application of coloring substances 
 or matter to Photographic impressions or pictures upon glass or 
 metal, or other material in the form and manner herein described. 
 
 Witnesses. 
 
 JAMES J. B. OGLE, \ GILES LANGDELL [L. s.] 
 
 WILLIAMS OGLE, j M. A. ROOT. [L. s.j 
 
 Dated July 15th, 1856. 
 
 PATENT FOR THE USE OF ALBUMENIZED COLLODION. 
 
 To all whom it may concern : 
 
 Be it remembered, that I, VICTOR M. GRISWOLD, of the 
 City of Lancaster, in the County of Fairfield and State of Ohio, 
 have invented certain improvements in the art and mode of taking 
 Photographic Pictures, and I do hereby declare that the following 
 is a full and exact description thereof: 
 
 The nature of my invention consists in an improvement in the 
 photographic art of taking pictures. To one quart of collodion pre- 
 pared in the usual way or manner, I add three ounces of a solution 
 
PHOTOGRAPHIC PATENTS. 187 
 
 prepared thus : The clear solution which results from the whites 
 of eggs which have been well beaten, and one equal bulk of pure 
 soft water. When this is added to the collodion, it is thrown to 
 the bottom in long stringy white masses, which after a few days 
 impart to the liquid albuminous properties, rendering the film 
 closer in texture, and bringing out all the minor details more 
 sharply and perfectly than by the ordinary collodion, and giving to 
 the picture a glossy and sparkling tone, unlike any produced by 
 other means. 
 
 Another method which I frequently adopt is thus ; albumen as 
 above, without water, to which is added iodide of potassium forty 
 grains ] this throws down the albumen in jelly-like masses, and, 
 when added to the collodion, not only iodizes it, but produces the 
 same effect upon the collodion as by the formula above. Also, 
 another method : one ounce of chloroform, to which is added one 
 half ounce of albumen, prepared as above, iodized ; this forms also 
 a soft semi-transparent jelly, which on being added to the collodion 
 produces perhaps the best effect of any of these preparations. 
 
 This addition of albumen also answers a far better purpose 
 than any that has hitherto been employed for freeing old 
 samples of collodion from free iodine held in suspension by 
 which they can be rendered as clear and limpid as they were when 
 first mixed. 
 
 What I claim as my invention, and desire to secure by Letters 
 Patent is the addition of albumen to collodion in the manner and 
 for the purpose herein and above specified. 
 
 V. M. GRISWOLD. 
 ALFRED M'VEIGH, ) T T 7 .. 
 J. C. HEULEY. } ^nesses. 
 
 Patented July 15th, 1856. 
 
 COLORING AMBROTYPES. 
 
 To all whom it may concern : 
 
 Be it known that we, D. B. SPOONER and H. B. SPOONER, 
 of Springfield, in the County of Hampden, in the State of Massachu- 
 
188 PHOTOGRAPHIC PATENTS. 
 
 setts, having invented new and useful improvements in coloring 
 Ambrotype or Photographic Pictures on glass, and we do hereby 
 declare that the following is a full and exact description thereof : 
 
 The nature of our invention consists, in so preparing the collo- 
 dion film containing the picture in alternate placers with gnm or 
 other suitable material, so that when a penetrating dye or pigment, 
 in a solution that will penetrate the collodion film, may be depo- 
 sited on any particular portion of the picture between the collodion 
 film and the glass, in order to give it the requisite color properly 
 distributed between the face, drapery, &c. 
 
 The following is the process adopted : 
 
 After the picture is thoroughly washed and dried, proceed with 
 a brush to cover any portion of the picture not designed to take the 
 color, with a solution of gum or any other substance insoluble in 
 the coloring solution ; but soluble in any other liquid in which the 
 coloring matter is not soluble. 
 
 E. G. Take a solution of gum arabic in water, and apply it to 
 a portion of the picture. Now take a solution of turmeric in 
 alcohol, and pour it upon the collodion surface of the picture, and 
 you immediately get a deposit of the coloring matter between the 
 collodion and the glass, the portion of the picture covered with the 
 gum not being penetrated by the alcohol, is protected from the 
 color while all other portions are colored. 
 
 Then, by washing the picture in water, the gum is dissolved and 
 washed off, and the parts uncolored may remain in their natural 
 state without color, or, by applying the gum solution to the portion 
 already colored with a part of the uneolored portion, another color 
 may be produced by the use of another pigment in the same man- 
 ner as before described. 
 
 In this manner any number of colors may be produced ; or, when 
 a small portion only of the picture is to be colored, the whole of 
 the picture may be colored and dried, and then that portion which 
 is to retain the color may be covered with the gum solution, and 
 the coloring matter not protected by the gum may be extracted 
 with alcohol or other solvent, and the gum washed off as before. 
 
PHOTOGRAPHIC PATENTS. 189 
 
 The advantages of our invention consist in depositing the color- 
 ing matter in its various tints on the front side of the picture be- 
 tween the collodion and the glass, instead of coloring the fibre of 
 the collodion, or the upper side of it, as is common, which does not 
 show through to the positive side of the picture on account of the 
 opacity of the silver deposit which forms the picture. 
 
 We do not claim the coloring of a picture all over with a single 
 tint, but 
 
 What we claim as our invention and desire to secure by Letters 
 Patent, is the application of gum arabic or other equivalent mate- 
 rial, as set forth in the specification, for the purposes therein de- 
 scribed, and no oiher. 
 Witnesses. 
 
 GEORGE W. ADAMS, | D. B. SPOONER. 
 
 CHAS. H. CODMAN. j H. B. SPOONER. 
 
 Patented August 5, 1856. 
 
CHAPTER VIII. 
 
 THE COLLODIO-ALBUMEN PROCESS. 
 
 This is a process, invented by Dr. Taupenot, for obtaining nega- 
 tives on glass, which bids fair to outrival all others, being easy of 
 manipulation, and giving results of the most exquisite minutiae and 
 beauty. Glass plates, when prepared and excited by this process, 
 may be kept at least a fortnight before being developed, and these 
 plates when exposed in the frame may be developed immediately, 
 or kept for days before commencing this operation. Indeed it is 
 quite possible to prepare and excite a number of plates before leav- 
 ing home to go on a tour of twelve or fourteen days ; to expose the 
 plates at any time or place during the journey, and bring them 
 home to be developed. 
 
 The manipulation may be said to consist of nine distinct opera- 
 tions. 
 
 1. Cleaning the plate. 2. Coating with iodized collodion. 3. 
 Exciting the collodion film. 4. Coating with albumen. 5. Ex- 
 citing the albumen coating. 6. Exposure in the camera. 7. De- 
 veloping the image. 8. Fixing the image. 9. Varnishing the 
 plate. 
 
 Before describing these operations, I propose to give clear direc- 
 tions for preparing the necessary solutions, merely promising that, 
 where I have deviated from the inventor's plan, it has been after 
 performing careful experiments, to test the merits of the two modes 
 of proceeding. 
 
 The necessary solutions for this process are : 
 
 Collodion bath solution. Iodized collodion. Iodized albumen. 
 Albumen bath solution. Pyrogallic solution. Silver developing 
 solution. Fixing solution. 
 
 Collodion Bath Solution. 
 
 Nitrate of silver in crystals - -1 ounce. 
 
 Iodide of potassium .... -2 grains. 
 
 Distilled water - 16 ounces. 
 
 Alcohol ---. -2 drachms. 
 
 Dissolve the ounce of nitrate of silver in two ounces of the dis- 
 tilled water, and the two grains of iodide of potassium in one 
 drachm of distilled water; mix the two solutions and shake well 
 together until the precipitate which is first thrown down is redis- 
 
COLLODIO-ALBUMEN PROCESS. 191 
 
 solved ; when this takes place, add the remaining fourteen ounces 
 of distilled water, and the two drachms of alcohol. On the addi- 
 tion of the water a turbidness ensues, which must be removed by 
 the solution being very carefully filtered through filtering paper; 
 and the filtered liquid should be clear and transparent, free 
 from any deposit or floating particles, and must possess a slightly 
 acid reaction of test-paper. 
 
 In order to ascertain if the solution thus prepared possesses the 
 necessary amount of free acid without superabundance, proceed to 
 test and to correct it, if necessary. 
 
 Iodized Collodion. 
 
 The collodion to be used in this process must be one yielding 
 good negative pictures lhat supplied by Home & Thornthwaite 
 under the name of negative collodion answers admirably. This is 
 supplied either ready iodized, or the collodion and iodizing in sepa- 
 rate bottles. As this collodion becomes less sensitive after being 
 iodized a fortnight, it is advisable to iodize no more than will be 
 used in that time therefore, obtain the collodion and the iodizing 
 solution separate, as the mode of iodizing this collodion is very 
 simple. Half an ounce of the iodizing solution is mixed with one 
 ounce and a half of collodion, and the mixture allowed to settle 
 twelve hours before being used ; and it is even advisable to pour 
 off the clear solution into a perfectly clean bottle, in order to get 
 rid of any insoluble matter which may fall to the bottom. 
 
 Iodized Albumen. 
 
 White of egg (free from yelk) .... 10 ounces. 
 
 Honey - 1 ounce. 
 
 Iodide of calcium- - 2 scruples* 
 
 Yeast ... 1 tablespoonful. 
 
 Mix these together in a tall glass jar, or wide-mouthed bottle of 
 at least one pint capaciiy ; tie a piece of paper, pierce with small 
 holes over the top to keep out dust; then place the whole near a 
 fire or other warm situation, where the temperature is not lower 
 than seventy degrees, or higher than ninety degrees. In a few 
 hours fermentation commences, which is evident by the formation 
 of bubbles of gas, rising through the liquid. This action continues 
 for five or six days j when it ceases, pour the whole on a paper- 
 filter contained in a funnel, underneath which must be placed a 
 bottle to receive the liquid as it passes through. The fluid being 
 of a viscid nature filters slowly, generally occupying twelve hours. 
 
 The filtered liquid is the " iodized albumen/' which is said by 
 
192 COLLODIO-ALBUMEN PROCESS, 
 
 Dr. Taupenot to keep good for years. It must be carefully pre- 
 served from dust or contact with any substance, as the success of 
 the picture depends materially on the condition of this albumen. 
 
 Albumen Bath Solution. 
 
 Nitrate of silver 1 ounce and a half. 
 
 Acetic acid, glacial 1 ounce. 
 
 Distilled water - - - - - - 16 ounces. 
 
 Animal charcoal 2 drachms. 
 
 Dissolve the nitrate of silver in the distilled water, then add the 
 acetic acid and animal charcoal, and keep in a closely stoppered 
 bottle for use. 
 
 Pyrogallic Solution. 
 
 Pyrogallic acid ...... 15 grains. 
 
 Glacial acetic acid 2 drachms. 
 
 Alcohol - 2 drachms. 
 
 Distilled water 7 ounces. 
 
 Dissolve the pyrogallic acid in the distilled -water, and then add 
 the acetic acid and alcohol. 
 
 Silver Developing Solution. 
 
 Nitrate of silver -1 drachm. 
 
 Acetic acid ........ 2 drachms. 
 
 Distilled water 7 ounces. 
 
 Dissolve the nitrate of silver in the distilled water, and then add 
 the acetic acid. 
 
 fixing Solution, 
 
 Hyposulphite of soda 2 ounces. 
 
 Water 1 pint dissolve. 
 
 Varnish. 
 
 The varnish best adapted for this purpose is that supplied by 
 Home & Thornthwaite, and termed negative varnish.* 
 
 Cleaning the Plate. 
 
 The plates must be cleaned in the usual way, merely premising 
 that extra care must be observed to remove every impurity, as 
 cleanliness in photography is an absolute necessity. 
 
 * In this country, Humphrey's Collodion Gilding is the article in almost uni- 
 versal use. 
 
COLLODIO-ALBUMEN PROCESS- 193 
 
 In order to hold large plates whilst being cleaned, the <c screw 
 plate-holder" is exceedingly useful. This is made in three sizes, 
 and adapts itself to all sized plates. 
 
 The small size is useful for plates up to 7 inches by 6. 
 
 The second size is for plates up to 10 inches by 8. 
 
 And the third size for plates up to 14 inches by 10. 
 
 Coating with Iodized Collodion. 
 
 The plate having been thoroughly cleaned, and received its final 
 polish by the use of a prepared chamois leather, is coated with nega- 
 tive collodion, which has been iodized at least twelve hours, and 
 allowed to settle. 
 
 Exciting the Collodion Film* 
 
 After the ether has evaporated, and the surface of the collodion 
 appears set, the plate must be laid, collodion side upwards, on a 
 glass dipper, and plunged with one downward movement into a 
 bath filled to within an inch of the top with collodion bath solu- 
 tion, made as described at page 190, which must be carefully fil- 
 tered through filtering paper before being used. After the plate 
 has been allowed to remain in the bath one minute, it is lifted out 
 three or four times, in order to facilitate the removal of the oily 
 appearance the plate now presents. When the surface appears 
 wetted uniformly, on being drawn out of the solution the plate is 
 removed from the dipper, and the excess of solution drained off, and 
 is then placed collodion side upwards, on a fixing stand, and dis- 
 tilled or filtered rain water poured over the surface, so as to re- 
 move as much as possible of the bath solution from the surface. 
 The plate is now removed from the fixing stand ; the back well 
 washed with water, and then placed nearly upright on blotting 
 paper, with the face against a wall for one minute to drain. 
 
 Coating with Albumen. 
 
 Having allowed the plate to drain one minute ; place it again on 
 a levelling stand, with the film upwards, and pour over it as 
 much of the iodized albumen as the plate will hold, from 
 a glass measure containing not more than enough of the 
 albumen to coat two plates with, pour off the excess into the 
 measure, and again cover the plate with albumen three separate 
 times; ultimately drain off as much as possible of the excess of 
 albumen, and place the plate nearly upright against the wall, 
 
 * This and subsequent operations (except exposure in the camera) must 
 be performed in a dark room. 
 
194 COLLODIO-ALBUMEN PROCESS. 
 
 with the coated side inwards, to dry, which takes place in an ordi- 
 nary temperature in about one hour, 
 
 In coating with albumen, the presence of air-bubbles or dust 
 must be guarded against. The former can be easily done by tak- 
 ing care, in pouring the albumen into the measure and on the plate, 
 not to pour so as to generate air-bubbles in the liquid. But should 
 any be detected, hold the plate horizontally and give it another 
 coating of albumen, then incline the plate so that the bulk of the 
 liquid shall pass over and carry off the bubbles with the running 
 stream. Dust on the plate must be prevented by operating in a 
 room as free from this photographic enemy as possible. 
 
 In order to render the coating of albumen as uniform as possible, 
 the plate must stand to dry on two or three layers of filtering paper 
 and the upper surface must touch the wall at one point only and 
 not to be allowed to rest against it along its entire upper edge. 
 
 When the albumen coating is thoroughly dry (and not till then), 
 the plate is ready to be excited, but if more have been prepared 
 than are likely to be used for taking pictures on during the next 
 ten days or fortnight, they may be stowed away in a plate box, 
 ready to receive the sensitive coating at any time. The author's 
 experience has led him to believe that these albumenized plates 
 will keep good any length of time, as plates which had been coated 
 a month, when excited, exposed, and developed, appeared to possess 
 all the properties of recently prepared plates. 
 
 Exciting the Albumen Coating. 
 
 Prior to the plates being excited they must be thoroughly dry 
 and free from any particles of loose dust on the surface, back, or 
 edge. Sufficient of the albumen bath solution, page 192, must be 
 filtered through filtering paper to fill a dipping bath of the required 
 size, so that the plate can be immersed in it. 
 
 The careful filtering of the fluid is very necessary in order to 
 free it from any floating particles, and to separate the animal char- 
 coal. 
 
 The plate is now taken and laid, albumen side upwards, on the 
 dipper, and then lowered into the bath with one steady downward 
 movement, where it is allowed to remain one minute ; it is then 
 taken out, the excess of liquid drained off, and placed on the fixing 
 stand, with the albumen surface uppermost, and a stream of water 
 poured over it for at least one minute, so as to remove every par- 
 ticle of the bath solution. This complete washing is very neces- 
 sary, in order to prevent stains in the after development, which in- 
 variabiy takes place around the edges, if not thoroughly washed. 
 The plate having been thoroughly washed, is leaned against a wall 
 to dry, or if required for immediate exposure, may be dried on a 
 plate of heated metal or foot warmer, but in no case must the ex- 
 posure in the camera take pi ace until the surf ace is thoroughly dry. 
 
COLLODIO-ALBUMEN PROCESS. 105 
 
 Exposure in the Camera.% 
 
 As has been before stated, this operation may take place im- 
 mediately the plate is thoroughly dry after being excited, or a 
 fortnight may intervene between the excitement arid exposure, 
 provided the plate is kept very carefully excluded from light and 
 any chemical or sulphurous vapors, in a plate-box adapted for that 
 purpose, with the sensitive surface towards the back of the box. 
 When the exposure is about to take place, or at any time previously, 
 the camera- backs may each have a plate placed in them ready for 
 exposure ; to do this, the camera-back must be taken into the ope- 
 rating room and the door closed, BO as to exclude all white light. 
 The hinged flap of the camera back is opened, and the prepared 
 plate laid, with its sensitive surface down wards, or next the sliding 
 flap, so that its corners may rest on the silver wire corners of the 
 plate frame previously placed within the camera back ready to re- 
 ceive it. The hinged flap is now closed and kept from opening by 
 turning the flap button over it ; the sliding flap is examined to see 
 that it is pushed closely down so as to guard any access of light, 
 and it is then ready to be placed in the camera, and may be taken 
 into the open air with impunity. Should the exposure not take 
 place immediately, or ; should the camera back have to be carried 
 any distance, it is advisable either to wrap it up in black cloth, or 
 secure the flaps from the chance of coming open during transit, 
 by a stout string being tied around the back. 
 
 The focussing is conducted in the usual way and the cap re- 
 placed on the lens ; the focussing glass is now removed and the 
 camera back fitted into the same aperture, with the sliding flap 
 next the lens. The sliding flap is pulled up to its fullest extent, 
 placing the hand on the camera back to prevent it rising out of 
 the camera with this action. The cap of the lens is then re- 
 moved, so that the light may be admitted into the camera, and 
 to fall on the sensitive surface of the plate. After the necessary 
 time of exposure has taken place, the cap is replaced on the lens, 
 the sliding flap is pushed down, and the camera back withdrawn 
 from the camera ; the plate can then be taken into the operating 
 room to be developed, or this operation may be deferred for days 
 or even a week, or more if convenient. The time of exposure in 
 the camera varies according to the intensity of the light and the 
 aperture and focal length of the lens ; therefore, to give the exact 
 time of exposure would be impossible, still it may assist the ama- 
 teur if I give the time required in summer with full sunshine, and 
 
 * Remarks as to the selection of the view, &c., are not given, as this can 
 be effected by the individual taste of the operator, but care must be taken 
 that direct rays from the sun shall not fall on the lens or enter the camera 
 during the exposure of a plate. 
 
196 COLLODIO-ALBUMEN PROCESS. 
 
 merely state that this time may be increased to double in winter 
 or dull weather. 
 
 In the ordinary sunshine of a summer's day the time of exposure 
 will be : 
 
 30 seconds with a lens of 4-inch focus and 4-inch stop. 
 
 21 seconds with a lens of 4-inch focus and |-inch stop. 
 
 5 seconds with a lens of 4-inch focus and l inch aperture 
 with no stop. 
 
 1^ minute with a lens of 6-inch focus and ^-inch stop. 
 
 4* seconds with a lens of 6-inch focus and 2^-inch aperture with 
 no stop. 
 
 2 minutes with a lens of 8-inch focus and |-inch stop. 
 
 li minute with a lens of 8-mch focus anof |-inch stop. 
 
 3 minutes with a lens of 10-inch focus and i-inch stop. 
 
 2 minutes with a lens of 10-inch focus and f-inch stop. 
 
 5 seconds with a lens of 10-inch focus, 3i-inch aperture, with 
 no stop. 
 
 6i minutes with a lens of 14-inch focus and |-inch stop. 
 
 4 minutes with a lens of 14-inch focus and f-inch stop. 
 
 2 minutes with a lens of 14-inch focus and f-inch stop. 
 
 8^ minutes with a lens of 16-inch focus and i-inch stop. 
 
 $i minutes with a lens of 16-inch focus and f-inch stop. 
 
 2f minutes with a lens of 16-inch focus and f-inch stop. 
 
 Developing the Image. 
 
 The camera back is taken into the operating room, from which 
 all white light is carefully excluded, the plate removed from the 
 camera back, and laid, albumen side upwards, on the fixing 
 stand; as much distilled water is now poured on it as the sur- 
 face will hold, taking care that every part of the sensitive sur- 
 face is covered with the liquid ; allow the water to remain on 
 the surface for one minute, then pour off and drain slightly; 
 replace the plate on the stand, and pour over the surface so as 
 thoroughly to cover every part, the pyrogallic solution (made as 
 described at page 192, and carefully filtered just before being 
 used) ; allow this to remain on the plate for one minute, then 
 drain off into a perfectly clean measure, and add to it an equal 
 bulk of silver developing solution, page 192 ; mix these thoroughly 
 together with a glass rod, and then pour the mixed liquids over 
 the plate ; allow them to rest until the picture begins to appear, 
 which generally takes about from three to five minutes ; then pour 
 off and on repeatedly, until the developing fluid becomes opaque, 
 which then contains floating particles, and these, if allowed to do 
 so, would settle on the plate, to the injury of the picture ; but this 
 may be prevented by brushing the surface with a camel's hair 
 brush frequently during the development. When this opacity of 
 
COLLODIO-ALBUMEN PROCESS. 197 
 
 the developing fluid takes place, drain all the fluid off the plate, 
 and thoroughly wash with water : then mix another quantity of 
 pyrogallie and silver developing solution in the same proportions 
 as before ; and pour this on and off the plate as before, until the 
 picture appears sufficiently intense, and the middle shades well 
 brought out ; when this takes place drain off, and wash with water. 
 so as to clean the surface thoroughly, and the plate is then ready 
 for the next step, " fixing the image." 
 
 Should the picture begin to develope in less than three minutes 
 after the application of the mixed developing fluids, thoroughly 
 drain the plate, and wash well with water, then continue the de- 
 velopment with a solution of three parts pyrogallie solution and 
 one part silver developing solution; but should the picture not 
 begin to appear in five minutes, the addition of half a drachm of 
 the albumen bath solution to each ounce of mixed developing solu- 
 tion will be necessary, in order to obtain the middle shades and 
 the required intensity. It may be stated, as a guide, that the best 
 negatives which the author has produced occupied from ten to 
 twelve minutes in developing. 
 
 Fixing the Image. 
 
 The plate, having been thoroughly freed from the developing 
 fluid by careful washing, is now placed on the fixing stand, and the 
 surface covered by the fixing solution, made as described at page 
 192 ; being poured over it. In a few seconds the yellow opalescent 
 color of the film will begin to disappear, and its complete removal 
 may be hastened by blowing gently on the plate, so as to disturb 
 the fluid. 
 
 When every particle of yellowness has disappeared, the fixing 
 solution is drained off, and the surface thoroughly washed, and it 
 is then leaned against the wall to drain and dry. 
 
 Varnishing the Plate. 
 
 The plate, being thoroughly dry, is ready to receive a coating of 
 transparent varnish.* in order to protect the albumen surface from 
 injury during the printing process. To do this effectually the 
 plate must be held before a fire, or over a lamp, until it is slightly 
 warm all over; then pour over its surface the negative varnish, in 
 the same manner as collodion is applied ; allow the superfluous 
 varnish to drain back into the bottle ; hold the plate again before 
 the fire until the whole of the spirit is evaporated ; and, when 
 cold, the plate is ready to be printed from, so as to produce any 
 number of positive pictures on paper. 
 
 It will be observed, that in describing. this process, the ope- 
 
 * Humphrey's Collodion Gilding is tlie best for this purpose. 
 
198 COLLODIO-ALBUMEN PROCESS. 
 
 rator has been supposed to be so situated, that in case a second 
 V'ew of the same spot were required, he could return to his ope- 
 rating room, remove the plate which had been exposed, from the 
 camera back to the plate box, and place another in the camera 
 back, ready for taking another view. But, unfortunately, this is 
 not at all times practicable. We, therefore, require some means 
 of removing the plates, after being exposed, from the camera back 
 into the plate box, and substituting others in their stead, whilst 
 we are in the open air. 
 
 In order to effect this, the " field plate box" has been devised 
 by the author, by the aid of which the plates may be removed 
 from the box, exposed in the camera, and again returned into the 
 box, without any possibility of access of light falling on it. 
 
 This box is but a trifle larger than the ordinary one, and is 
 furnished with two sliding bottoms, working in grooves, one over 
 the other; the lower bottom has a grooved channel, into which 
 the side of the camera back slides ; the camera back has an 
 aperture through the side, closed by a narrow slide, and the lower 
 bottom of the field box has a corresponding one. We now suppose 
 the field box to have been previously filled with excited glass 
 plates, having their sensitive sides towards the back of the box, 
 and the box lid closed. The bottom slide is now pushed on until 
 the aperture is in a line with any particular groove of the field 
 box (which position is indicated by a numbered scale and index 
 point). The camera back is then slid on to its place on the field 
 box, so that the hinged flap is towards the front of the box, and its 
 narrow slide drawn out. The upper slide is then withdrawn, and 
 the box inclined, so that the plate in that groove opposite the aper- 
 ture in the lower slide, may pass through into the camera back. 
 When this has taken place, push in the narrow slide of the camera 
 back, invert the box, and push in the inner slide; then withdraw 
 the camera back from its channel, and expose the plate in the ca- 
 mera. When this is done, slide the back again into its channel, 
 draw out the inner box slide, then the narrow camera back slide, 
 invert the box, and the plate will then leave the camera back and 
 pass into the field box, occupying the same groove as before. 
 
 In order to get out another plate, slide the lower bottom, so 
 that the index points to the number on the scale, as that of the 
 groove in which the required plate is situate. Then proceed as 
 before directed. 
 
CHAPTER IX. 
 
 ON A MODE OF PRINTING ENLARGED AND REDUCED POSI- 
 TIVES, ETC., FROM COLLODION NEGAVIVES. 
 
 To explain the manner in which a photograph may be enlarged 
 or reduced in the process of printing, it will be necessary to refer 
 to the remarks made at page 20, on the conjugate foci of lenses. 
 
 If a collodion negative be placed at a certain distance in front of 
 a camera, and (by using a tube of black cloth) the light be 
 admitted into the dark chamber only through the negative, a re- 
 duced image will be formed upon the ground glass ; but if the 
 negative be advanced nearer, the image will increase in size, until 
 it becomes first equal to, and then larger than, the original nega- 
 tive ; the focus becoming more and more distant from the lens, or 
 receding, as the negative is brought nearer. 
 
 Again, if a negative portrait be placed in the camera slide, and 
 if the instrument be carried into a dark room, a hole be cut in the 
 window-shutter so as to admit light through the negative, the 
 luminous rays, after refraction by the lens, will form an image of 
 the exact size of life upon a white screen placed in the position 
 originally occupied by the sitter. These two planes, in fact, that 
 of the object and of the image, are strictly conjugate foci, and, as 
 regards the result, it is immaterial from which of the two, anterior 
 or posterior, the rays of light proceed. 
 
 Therefore in order to obtain a reduced or enlarged copy of a ne- 
 gative, it is necessary only to form an image of the size required, 
 and to project the image upon a sensitive surface either of collo- 
 dion or paper. 
 
 A good arrangement for this purpose may be made by taking an 
 ordinary portrait camera, and prolonging it in front by a deal box 
 blackened inside and with a double body, to admit of being 
 lengthened out as required; or, more simply, by adding a frame- 
 work of wood covered in with black cloth. A groove in front car- 
 ries the negative, or receives the slide containing the sensitive 
 layer, as the case may be. 
 
 In reducing photographs, the negative is placed in front of the 
 lens, in the position ordinarily occupied by the object but in mak- 
 ing an enlarged copy it must be fixed behind the lens, or, which is 
 equivalent, the lens must be turned round so that the rays of light, 
 
200 PRINTING POSITIVES. 
 
 transmitted by the negative, enter the back glass of the combina- 
 tion, and pass out at the front. This point should be attended to 
 in order to avoid indistinctness of image from spherical aberration. 
 
 A portrait combination of lenses of 2^ or 3| inches is the best form 
 to use, and the actinic and luminous foci should accurately corres- 
 pond; as any difference between them would be increased by en- 
 larging. A stop of an inch or an inch and a half aperture placed 
 between the lenses obviates to some extent the loss of sharp outline 
 usually following enlargement of the image. 
 
 The light may be admitted through the negative by pointing the 
 camera towards the sky : or direct sunlight may be used, thrown 
 upon the negative by a plane reflector. A common swing looking- 
 glass, if clear and free from specks, does very well; it should be 
 so placed that the centre on which it turns is on a level with the 
 axis of the lens. 
 
 The best negatives for printing enlarged positives are those which 
 are distinct and clear ; and it is important to use a small negative, 
 which strains the lens less and gives better results than one of 
 larger size. In printing by 2 lens for instance, prepare the nega- 
 tive upon a plate about two inches square and afterwards enlarge 
 it four diameters. 
 
 Paper containing chloride of silver is not sufficiently sensitive to 
 receive the image, and the print should be formed upon collodion, 
 or on iodized paper developed by gallic acid. 
 
 The exposure required will vary not only with the intensity of 
 the light and the sensibility of the surface used, but also with the 
 degree of reduction or enlargement of the image. 
 
 In printing upon collodion the resulting picture is positive by 
 transmitted light ; it should be backed up with white varnish, and 
 then becomes positive by reflected light. The tone of the blacks 
 is improved by treating the plate first with bichloride of mercury, 
 and then with ammonia. 
 
 Mr. Wenham, who has written a most practical paper on the 
 mode of obtaining positives of the life size, operates in the follow- 
 ing way : he places the camera, with the slide containing the ne- 
 gative in a dark room, and reflects the sunlight in through a hole 
 in the shutter, so as to pass first through the negative and then 
 through the lens ; the image is received upon iodized paper, and 
 developed by gallic acid. 
 
 On Printing Collodion Transparencies for the Stereoscope. This 
 may be done by using the camera to form an image of the nega- 
 tive in the mode described at the last page; but more simply by 
 the following process : Coat the glass, upon which the print is to 
 be formed, with collodio-iodide of silver in the usual way, then lay 
 it upon a piece of black cloth, collodion side uppermost, and place 
 two strips of paper of about the thickness of cardboard and one- 
 fourth of an inch broad, along the two opposite edges, to prevent 
 
TO SENSITIZE PAPER. 201 
 
 the negative being soiled by contact with the film. Both glasses 
 must be perfectly flat, and even then it may happen that the nega- 
 tive is unavoidably wetted j if so, wash it immediately with water, 
 and if it be properly varnished no harm will result. 
 
 A little ingenuity will suggest a simple framework of wood, on 
 which the negative and sensitive plate are retained, separated only 
 by the thickness of a sheet of paper; and the use of this will be 
 better than holding the combination in the hand. 
 
 The printing is conducted by the light of gaa or of a camphine or 
 moderator lamp, diffused daylight would be too powerful. 
 
 The employment of a concave reflector, which may be purchased 
 for a few shillings, ensures parallelism of rays, and is a great im- 
 provement. The lamp is placed in the focus of the mirror, which 
 may at once be ascertained by moving it backwards and forwards 
 until an evenly illuminated circle is thrown upon a white screen 
 held in front. This in fact is one of the disadvantages of printing 
 by a naked flame that the light falls most powerfully upon the 
 central part, and less so upon the edges, of the negative. 
 
 (From Humphrey's Journal, No. 17, Vol. 8.) 
 ON THE USE OF ALCOHOL FOR SENSITIZING PAPER. 
 
 I have practised for some time the following simple method, 
 which appears to me to be very superior for cleanliness and cele- 
 rity in working, for depth of tone, and especially for purity of white 
 in its results. By means of it T have produced very satisfactory re- 
 sults upon paper which was otherwise nearly worthless. 
 
 To your sensitizing solution (which should be not less than 60 
 grains to the ounce), whether simple nitrate or ammonio-nitrate, 
 add 50 per cent, of alcohol. Float the paper upon the solution for 
 40 seconds. 
 
 This method answers equally well for albumenized or plain 
 paper. You will find that the solution penetrates the paper which 
 flattens instantaneously upon it. It becomes as transparent as 
 though it were oiled, and every minute air-bubble or defect in the 
 paper is rendered visible. Remove the air-bubbles by pressing 
 upon the paper about an inch from the bubble, and thus driving 
 it out under the paper. In doing this, if the solution flows par- 
 tially over the back of the paper, shake it until the paper is wholly 
 
202 TO SENSITIZE PAPER, 
 
 immersed, which will prevent any unevenness in printing. Th<3 
 paper reassumes its transparency in the toning bath, but it will 
 dry a pure white. The sensitising solution will not become mate- 
 rially discolored even after frequent applications of albumenized 
 paper. Should it become so much discolored as to give a dark hue 
 to the paper, shake it in a bottle with two drachms of animal 
 charcoal and leave it a night to settle. It will filter clear, A 
 very small portion of your solution may be made available in sen- 
 sitizing a sheet of paper by pouring it upon a clean glass, the size 
 of the paper or a little larger, which is carefully levelled and 
 nicely laying down the paper upon it. This is useful when your 
 solution is too small to float in your trays. The alcohol causes it 
 to flow and be absorbed with perfect evenness. 
 
 To remove the papers from the solution and dry them : Pro- 
 vide a dozen or more clothes-pins, of the kind that are supplied 
 with a ring of india-rubber for a spring. Into the top drive a pin 
 firmly and bend it to a hook. Lift a corner of the paper by pass- 
 ing under it the point of a quill tooth-pick, and attach to it one of 
 the clothes-pins ; lift the edge out by this, and attach another to 
 the other corner. You may thus carry the sheet by the pins and 
 hang it upon a line to dry without touching it with the fingers, a 
 matter of some importance to Amateurs of the art, who mnst have 
 unstained hands for their day's business. 
 
 It may be worth while here to add the following simple and eco- 
 nomical method of printing, which I have found to surpass in con- 
 venience and afford all the advantages of the most expensive 
 printing frames. Four common clothes-pins, such as work with a 
 wire spring supply pressure enough for a f-plate. Lay your pre- 
 pared paper upon the negative, and next to it about twenty sepa- 
 rate leaves of thin common wrapping paper cut to the size of the 
 negative ; next a sheet of tolerably stiff and smooth writing paper, 
 and lastly, a piece of glass as a back to the whole. Let the glass 
 back be pushed from the lower edge of the papers about 1-20 of 
 an inch, or just so far as to enable you to pinch the negative and 
 
RECOVERY OF WASTE SILVER, ETC. 203 
 
 papers with the thumb-nail and forefinger. Attach a pin to each 
 corner and your negative is prepared for exposure. Now, to exa- 
 mine your picture without endangering its displacement: remove 
 the pins from one end, and place it, face downwards, on a table, 
 the other end with pins attached projecting an inch beyond the 
 edge. Hold down the back glass with the left hand, while with 
 the right you remove the pins and pinch the papers and nega- 
 tive together between the forefinger and thumb-nail. Upon the 
 smooth sheet of paper you can easily slide the back glass an inch 
 from the edge. Hold it there, and on the uncovered margin attach 
 three of the pins \vith as deep a bite as they will take. You may 
 now examine your picture to within an inch of its margin, as you 
 would turn over the leaves of a book. To replace the back, lay it 
 again on the table and slide the back glass up to the pins before 
 you remove them. The rest of the process is obvious. 
 
 The minutiae of my communication may excite a smile with 
 some, but I shall always act upon the principle, that nothing is 
 more out of place than an apology for minuteness in describing ma- 
 nipulations. G. B. C. 
 
 RECOVERY OF SILVER FROM WASTE SOLUTIONS, FROM THE 
 BLACK DEPOSIT OF HYPO BATHS, ETC. 
 
 The manner for separating metallic silver from waste solutions 
 varies according to the presence or absence of alkaline hyposulphite 
 and cyanides. 
 
 a. Separation of metallic Silver from old Nitrate Baths. The 
 silver contained in solutions of the nitrate, acetate, etc.. may easily 
 be precipitated by suspending a strip of sheet copper in the liquid ; 
 the action is completed in two or three days, the whole of the nitric 
 acid and oxygen passing to the copper, and forming a blue solution 
 of the nitrate of copper. The metallic silver however separated 
 in this manner, always contains a portion of copper, and gives a 
 blue solution when dissolved in nitric acid. 
 
204 RECOVERY OF WASTE SILVER, ETC. 
 
 A better process is to commence by precipitating the silver 
 entirely in the form of chloride of silver, by adding common salt 
 until no further milkiness can be produced. If the liquid is well 
 stirred, the chloride of silver sinks to the bottom, and may be 
 washed by repeatedly filling the vessel with common water, and 
 pouring off the upper clear portion when the clots have again set- 
 tled down. The chloride of silver thus formed may afterwards be 
 reduced to metallic silver by a process which will presently be de- 
 scribed. 
 
 b. Separation of Silver from solutions containing alkaline Hy- 
 posulphites, Cyanides or Iodides. In this case the silver cannot 
 be precipated by adding chloride of sodium, since the chloride of 
 silver is soluble in such liquids. Therefore it is necessary to use 
 the sulphuretted hydrogen, or the hydrosulphate of ammonia, and 
 to separate the silver in the form of sulphuret. 
 
 Sulphuretted hydrogen gas is readily prepared, by fitting a cork 
 and flexible tubing to the neck of a pint bottle, and having intro- 
 duced sulphuret of iron (sold by operative chemists for the purpose), 
 about as much as will stand in the palm of the hand, pouring upon 
 it H fluid ounces of oil of vitriol diluted with 10 ounces of water. 
 The gas is generated gradually without the application of heat ; and 
 must be allowed to bubble up through the liquid from which the 
 silver is to be separated. The smell of sulphuretted hydrogen be- 
 ing offensive, and highly poisonous if inhaled in a concentrated form, 
 the operation must be carried on in the open air, or in a place where 
 the fumes may escap3 without doing injury. 
 
 "When the liquid begins to acquire a strong and persistent odor of 
 sulphuretted hydrogen, the precipitation of sulphuret is completed. 
 The black mass must therefore be collected upon a filter, and 
 washed by pouring water over it, until the liquid which runs 
 through gives little or no precipitation with a drop of nitrate of 
 silver 
 
 The silver may also be separated in the form of sulphuret from 
 old hypo baths, by adding oil of vitriol in quantity sufficient to de- 
 
ON THE USE OF TEST PAPERS. 205 
 
 compose the hyposulphite of soda ; and burning off the free sul- 
 phur from the brown deposit. 
 
 Conversion of Sulphuret of Silver into Metallic Silver. Tho 
 black sulphuret of silver may be reduced to the state of metal by 
 roasting and subsequent fusion with carbonate of soda; but it is 
 more convenient, in operating on a small scale, to proceed in the 
 following manner : first convert the sulphuret into nitrate of sil- 
 ver, by boiling with nitric acid diluted with two parts of water ; 
 when all evolution of red fumes has ceased, the liquid may be di- 
 luted, allowed to cool, and filtered from the insoluble portion, which 
 consists principally of sulphur, but also contains a mixture of chlo- 
 ride and sulphuret of silver, unless the nitric acid employed was 
 free from chlorine ; this precipitate may be heated in order to vola- 
 tilize the sulphur, and then digested with hyposulphite of soda, or 
 added to the hypo bath. 
 
 The solution of nitrate of silver obtained by dissolving sulphuret 
 of silver is always strongly acid with nitric acid, and also contains 
 sulphate of silver. It may be crystallized by evaporation ; but 
 unless the quantity of material operated on is large, it will be 
 better to precipitate the silver in the form of chloride, by adding 
 common salt, as already recommended. 
 
 ON THE USE OF TEST PAPERS. 
 
 The nature of the coloring matter which is employed in the 
 preparation of litmus-paper has already been described at page 98. 
 
 In testing for the alkalies and basic oxides generally, the blue 
 litmus-paper which has been reddened by an acid may be used, 
 or. in place of it, the turmeric paper. Turmeric is a yellow vege- 
 table substance which possesses the property of becoming brown 
 when treated with an alkali ; it is however decidedly less sensi- 
 tive than the reddened litmus, and is scarcely affected by the weaker 
 bases, such as oxide of silver. 
 
 In using test papers observe the following precautions: they 
 10 
 
206 SALTING TAPER, ETC. 
 
 should be kept hi a dark place, and protected from the action of 
 the air ? or they soon become purple from carbonic acid, always 
 present in the atmosphere in small quantity. By immersion in 
 water containing about one drop of liquor potassse in four ounces, 
 the blue color is restored. 
 
 Test-papers prepared with porous paper show the red color bet- 
 ter than those upon glazed or strongly sized paper. If the quan- 
 tity of acid present however is small, it is not sufficient in any 
 case simply to dip the paper in the liquid ; a small strip should 
 be thrown in, and allowed to remain for ten minutes or a quarter 
 of an hour. 
 
 If the paper, on immersion, assumes a wine-red or purple tint, 
 in place of a decided red, it is probably caused by carbonic aid 
 gas : in that case the blue color returns when the paper is washed 
 and held to the fire. 
 
 Blue litmus-papers may be changed to the red papers used for 
 alkalies by soaking in water acidified with sulphuric acid, one drop 
 to half a pint. 
 
 THE SALTING AND ALBUMENIZING PAPER. 
 Tak3 of 
 
 Chloride of ammonium, or pure chloride of sodium - 200 grains. 
 Water - - - 10 fluid oz. 
 
 Albumen - - 10 fluid oz. 
 
 If distilled water cannot be procured, rain water or even corn- 
 mon spring water* will answer the purpose. To obtain the albu- 
 men, use new-laid eggs, and be careful that in opening the shell 
 the yelk is not broken: each egg will yield about one fluid ounce 
 of albumen. 
 
 When the ingredients are mixed, take a bundle of quills or a 
 fork, and beat the whole into a perfect froth. As the froth forms, 
 
 * If the water contained much sulphate of lime, it is likely that the sea 
 Bitiveness of the paper would be impaired (?). 
 
SALTING PAPER, ETC. 207 
 
 it is to be skimmed off and placed in a flat di&h to subside. The 
 success of the operation depends entirely upon the manner in 
 which this part of the process is conducted ; if the albumen is 
 not thoroughly beaten, flakes of animal membrane will be left in 
 the liquid, and will cause streaks upon the paper. When the 
 froth has partially subsided, transfer it to a tall and narrow jar, 
 and allow to stand for several hours, that the membranous shreds 
 may .settle to the bottom. Pour off the upper clear portion, which 
 is fit for use-.'' Albumenous liquids are too glutinous to run well 
 through a paper filter, and are better cleared by subsidence. 
 
 A more simple plan than the above, and one equally efficacious, 
 is to fill a bottle to about three parts with the salted mixture of 
 albumen and water, and to shake it well for ten minutes or a quar- 
 ter of an hour, until it loses its glutinosity and can be poured out 
 smoothly from the neck of the bottle. It is then to be transferred 
 to an open jar, and allowed to settle as before. 
 
 The soluticu ; prepared by the above directions, will contain ex- 
 actly ten grains of salt to the ounce, dissolved in an equal bulk of 
 albumen and water. Some operators employ the albumen alone 
 without an addition of water, but the paper in that case has a very 
 highly varnished appearance, which is thought by most to be ob- 
 jectionable. 
 
 The principal difficulty in albumenizing paper is to avoid the 
 occurrence of streaky lines, which, when the paper is rendered sen- 
 sitive, bronze strongly under the influence of the light. The writer 
 believes these to be caused by a commencing decomposition of the 
 animal matter composing the cells in which the albumen is retained 
 and the best remedy appears to be to use the eggs quite fresh ; the 
 same object may sometimes (but not invariably) be attained by 
 allowing the albumen to stand for several weeks until it has be- 
 come sour ; after which it will be sufficiently limpid to run through 
 a filter. 
 
 In salting and albumenizing photographic paper by the formula 
 above given, it was found that each quarter sheet, measuring 
 eleven by nine inches, removed one fluid drachm and a half from 
 
208 SALTING PAPER, ETC. 
 
 the bath ; equivalent to about one grain and three quarters of salt 
 (including droppings). In salting plain paper, each quarter sheet 
 took up only one drachm ; so that the glutinous nature of the al- 
 bumen causes a third part more of the salt to be retained by the 
 paper. 
 
 Selection of the Paper. The English papers are not good for al- 
 bumenizing; they are too dense to take the albumen properly, and 
 curl up when laid upon the liquid ; the process of toning the prints 
 is also slow and tedious. The thin negative paper of Canson, the 
 Papier Rieve, and Papier Saxe. have succeeded with, the writer 
 better than Canson's positive paper, which is usually recommended ; 
 they have a finer texture and give more smoothness of grain. 
 
 To apply the albumen, pour a portion of the solution into a flat 
 dish to the depth of half an inch. Then, having previously cut 
 the paper to the proper size, take a sheet by the two corners, bend 
 it into a curved form, convexity downwards, and lay it upon the 
 albumen, the centre part first touching the liquid and the corners 
 being lowered gradually. In this way all bubbles of air will be 
 pushed forwards and excluded. One side only of the paper is wet- 
 ted : the other remains dry. Allow the sheet to rest upon the so- 
 lution for one minute and a half, and then raise it off, and up by 
 two corners. If any circular spots, free from albumen, are seen, 
 caused by bubbles of air, replace the sheet for the same length of 
 time as at first. 
 
 The paper must not allowed to remain upon the salting bath 
 much longer than the time specified, because the solution of albu- 
 men being alkaline (as is shown by the strong smell of ammonia 
 evolved on the addition of the chloride of ammonium), tends to re- 
 move the size from the paper and sink in too deeply ; thus losing 
 its surface gloss. 
 
 Albumenized paper will keep a long time in a dry place. Some 
 have recommended to press it with a heated iron, in order to coa- 
 gulate the layer of albumen upon the surface ; but this precaution 
 19 unnecessary, since the coagulation is perfectly affected by the 
 
SALTIXG PAPER, ETC. 209 
 
 nitrate of silver used in the sensitizing ; and it is doubtful whether 
 a layer of dry albumen would admit of coagulation by the simple 
 application of a heated iron. 
 
 To render the paper sensitive. This operation must be conducted 
 by the light of a candle, or by yellow light. Take of 
 
 Nitrate of Silver '" 60 grains. 
 
 Distilled Water - 1 ounce. 
 
 Prepare a sufficient quantity of this solution, and lay tlie sheet 
 upon it in the same manner as before. Three minutes' contact will 
 be sufficient with the thin negative paper, but if the Canson posi- 
 tive paper is used, lour or five minutes must be allowed for the 
 decomposition. The papers are raised from this solution by a pair 
 of bone foreceps or common tweezers tipped with sealing-wax ; or 
 a pin may be used to lift up the corner, which is then taken by the 
 finger and thumb and allowed to drain a little before again putting 
 in the pin, otherwise a white mark will be produced upon the pa- 
 per, from decomposition of the nitrate of silver. When the sheet 
 is hung up, a small strip of blotting-paper suspended from the lower 
 edge of the paper will serve to drain off the last drop of liquid. 
 
 The solution of nitrate of silver becomes after a time discolored 
 by the albumen, but may be used for sensitizing until it is nearly 
 black. The color can be removed by animal charcoal,* but a 
 better plan is to use the '' kaolin" or pure white china clay. The 
 writer has also tried the common " pipe-clay," which answered 
 perfectly, but appeared to injure the sensitiveness of paper subse- 
 quently floated upon the bath (?). 
 
 Sensitive albumenized paper, prepared as above, will usually 
 keep for several days, if protected from the light, but afterwards 
 turns yellow from partial decomposition. 
 
 * Common animal charcoal contains carbonate and phosphate of lime 
 the former of which renders the nitrate of silver alkaline ; purified animal 
 charcoal is usually acid from hydrochloric acid. 
 
310 
 
 WEIGHTS AND MEASURES. 
 
 Comparison of British and French Weight* 
 and Measures. 
 
 WEIGHTS 
 
 Grain, Apothecaries'. 
 Ounce " 
 
 " Avoirdupois 
 Drachm, Apothecaries' 
 
 Gramme 
 
 Decigrammo 
 
 Centigramme 
 
 0-0648 grammes, French. 
 31-102 " 
 
 28-346 " 
 
 3-888 " 
 
 15-4340 grains, Apoth. 
 1-5434 " " 
 0-1543 " 
 
 Litre 
 Decilitre 
 Centilitre 
 MillUitre 
 
 Killogramme 
 
 MEASURES OF CAPACITY. 
 
 Cubic Inches. 
 
 61-028 = 
 
 6.02 = 
 
 0-610 = 
 
 0-061 = 
 
 Lb. 
 2 
 
 MEASURES OF LENGTH. 
 
 Metre 
 Decimetre 
 Centimetre 
 Milimetre 
 
 Cubic inch of water at 32* 
 " " mercury " 
 
 Fluid oz. of water 
 " " measure* 
 
 1 f. drachm 
 
 1 pint (New York) 
 
 1 oz. bromine 
 
 1 grain, Troy or Apoth. 
 
 1 IK Avoir. 
 
 1 " 
 
 Fluid Ounce*. 
 35-79 
 3-57 
 0-35 
 0-03 
 
 Oz. 
 
 3 AvoirdupoU. 
 
 39-37 inches. 
 3-93 " 
 0-39 " 
 0-03 " 
 
 252-45 grains. 
 3425-35 " 
 437-50 " 
 1-73 cub. in. 
 
 54-68 grains. 
 
 27-68 cub. in. 
 
 2 f. drachma. 
 1-097 gr. Avoir. 
 7000 Troy grs. 
 7680 of its own grs. 
 
 The drachm Avoirdupois is never used except in weighing silk. 
 Pendulum vibrating seconds at New York = 39- 102 inche*. 
 
WEIGHTS AND MEASURES. 211 
 
 In weighing solids, few weights are really necessary if they are properly 
 assorted ; nothing less than half a grain is likely to be useful, and the series 
 following will weigh any quantity from the half grain to two thousand one 
 hundred and ten and a half grains, by differences of only a single grain. 
 
 The numbers are hi grains, but the same principle may be carried out 
 with any other denomination, whether ounces, pounds, or tons. 
 
 }, 1,2, 3, 4 ; 10, 20, 30, 40 ; 100, 200, 300, 400 ; 1000, &c. 
 
 The artist should be p/ovided with not less than three glass measures 
 one of a pint, graduated to ounces one of two ounces, graduated to drachms 
 and one of two drachms, graduated to minims. 
 
 Lewis's Patent Glass Baths for Nitrate of Silver Solutions. Since 
 the foregoing pages have been in print this new article of Baths has been 
 introduced, and will probably supersede all others now in market. They 
 are encased in a box made expressly to hold them, and form a valuable and 
 important improvement in the apparatus used in the various Glass processes. 
 
212 
 
 INDEX. 
 
 ABERRATION, chromatic, 23; spherical. . 
 
 Acetic acid, 66. 
 
 Albumen, 68 ; preparation of positive paper with, 206. 
 
 Alcohol, 70; used in sensitizing paper, 201. 
 
 Ammonia, 71. 
 
 Ammonio-nitrate of silver, preparation and use of, 152. 
 
 Animal charcoal, 74. 
 
 Barium, chloride of, 77. 
 Baths, glass, 211 j gutta pcrcha, 34. 
 Bichloride of mercury for whitening positives. 159. 
 Bromide and iodide of potassium and silver, 60. 
 Bromide of potassium, 73. 
 Bromine, properties of, 72. 
 
 Bromo-iodized collodion for positives, (ambrotypes), 58, 59 ; for 
 negatives, 60. 
 
 Camera boxes. 28. 
 Camera, construction of, 28. 
 Camera stands, 31. 
 Carbonate of soda, 73. 
 Chemical and visual focus, 21. 
 China clay, 75. 
 Chloride of ammonium, 77. 
 Chloride of barium, 77. 
 
 Chloride of gold, preparation of, 83 ; for toning, 155 
 Chloride of sodium, 78. 
 Chlorine, 75. 
 Chromatic aberration, 22. 
 Citric acid, 78. 
 Cleaning glass plates, 129. 
 Coating large glasses with collodion, 160. 
 Collodion, manufacture of, 53 ; iodized for positives, 58, 59 ; for 
 negatives, 60 ; mode of coating glasses with, 131 ; vials, 38. 
 Collodio-Albmnen process, Dr. Taupeuot, 190. 
 Color boxes, 
 
 Cutting's patents and correspondence, 173. 
 Cyanide of potassium, 79 : use of, 63. 
 
INDEX. 213 
 
 Decomposition of light, 16. 
 
 Developing solution for positives, 62; for negatives, 144 ; 145. 
 
 Dippers, glass and gutta percha, 
 
 Double iodide of potassium and silver, 61. 
 
 Ether, preparation of ; 79. 
 
 Fixing positives on glass, 134; negatives on glass, 146; posi- 
 tives on paper, 155. 
 Fluoride of potassium, 81. 
 Fogging of collodion positives, 137. 
 Formic acid, 81. 
 Fulminating gold, 84. 
 
 Gelatine, properties of, 82; for mounting photographs, 157. 
 
 Glass, cementing, 158. 
 
 Glass plates, cleaning of, 129; coating with collodion, 131; 
 
 coating with albumen, 193. 
 Glass rods, bending of, 158. 
 Glycerine, its properties, 82. 
 
 Gold, chloride of, preparation of, 85; for toning, 155. 
 Grape sugar, 86. 
 
 Hadow, Mr. /Researches and Formula for making soluble cotton, 
 
 46 ; on iodizing collodion, 54. 
 Head rests, 33. 
 
 Helio, collodion process for positives and negatives, 164. 
 Honey, 86. 
 
 Humphrey's collodion gilding, 63. 
 Hydrochloric acid, 87. 
 Hydroiodic acid, 87. 
 Hydrosulphuric acid, 88. 
 Hypo bath, 203. 
 Hyposulphite of gold, 85. 
 Hyposulphite of silver, 17. 
 Hyposulphite of soda, preparation and properties of, 89. 
 
 Instantaneous positives, 159. 
 
 Iodide of ammonium, preparation of, 91 ; for iodizing collo- 
 dion, 58, 59. 
 
 Iodide of cadmium, 92. 
 
 Iodide of iron, preparation of, 93 ; its uses and acceleration, 159. 
 
 Iodide of potassium and silver, preparation of, 61 ; use in sensi- 
 tizing collodion, 58, 60. 
 
 Iodide of potassium, properties and preparation of, 94. 
 
 Iodide of silver, preparation and properties of, 112 ; its use in 
 the nitrate bath. 65, 147. 
 
214 IXDEX. 
 
 Iodine ; preparation and properties of, 90. 
 Iodized collodion, 58, 59, 60 ; 131. 
 Iron, perchloride of, 98. 
 li protonitrate of, 97. 
 
 Jenny Lind stands, 32. 
 Kaolin, properties of, 75. 
 
 Lenses, double-convex, concavo-convex, double-concave, 19. 
 Lenses, forms of, 19, 20; combination of, for portraits, 27; 
 
 chromatic aberration of, 23 ; spherical aberration of, 22. 
 Leveling stands, 35. 
 Light, decomposition of, 16. 
 Litmus, 98. 
 
 Manipulations of the positive collodion process, 129 ; negative 
 
 process, 143. 
 
 Measures and Weights, 210. 
 Milk, 99. 
 Mounting positives on paper, 157. 
 
 Negatives for printing positives, 151, 169. 
 
 Nitrate of potash, 102. 
 
 Nitrate of silver,' 11 6. 
 
 Nitrate of silver bath, mode of preparing for positives, 64; for 
 negatives, 147; for negatives and positives in Helio's pro- 
 cess, 164. 
 
 Nitrate of silver used in developing negatives, 145. 
 
 Nitric acid, preparation and properties of, 100; use in nitrate 
 bath, 65, 147 ; use in making soluble cotton, 46. 
 
 Nitro-sulphuric acid used in preparing soluble cotton, 42, 51. 
 
 Oxide of silver, preparation of, 109. 
 
 Oxygen, 109. 
 
 Oxymel, preparation of, 105. 
 
 Paper, sensitive, for printing, 152 ; alcohol used in, 201. 
 
 Patent for the use of camphor in combination with iodized col- 
 lodion, 176 ; for sealing photographic pictures, 177 ; for the 
 use of alcohol as a desiccating agent, 178 ; for the use of 
 bromide of potassium in collodion, 178 ; for the use of ja- 
 panned surfaces for taking positives, 179 ; for photographic 
 pictures in oil, 181 ; for making transparent borders, 183; 
 coloring positives, 185,187; for albumenized collodion, 186- 
 
 Plate-Holders, Lewis's patent, solid glass corners for, 137. 
 
 Plate vices, 64, 
 
IXDEX. 215 
 
 Portrait lenses, combination of, 9,7. 
 
 Positives, (ambrotypes,) process for producing, 129 ; by the He- 
 
 lio process, 164; printing on albumenized paper, 192,206; 
 
 ammonio-nitrate of silver used in, 152; use of chloride of 
 
 gold in toning. 155; fixing, 155; fixing and brightening, 
 
 (atnbrotypes), Humphrey's collodion gilding used in, 63 ; 
 
 printing frames for, 36; collodion for, 58, 59; mica used 
 
 for, 136. 
 
 Positives, enlarging from negatives, 199. 
 Potash, 105; carbonate of, 106. 
 Practice of the positive collodion process, 129; negative process. 
 
 143; Helio's positive and negative- process, 164; printing 
 
 on paper, 151. 
 
 Prism, 14 ; refraction of light by, 14. 
 Protosulphite of iron used in developing positives. 62 ; negatives, 
 
 144. 
 Pyrogallic acid, preparation of, 107. 
 
 Sensitizing paper, \ise of alcohol in, 201. 
 
 Silver, properties of, 107 ; removal of stains from the nitrate of, 
 
 161 ; recovery of from waste solutions, 203. 
 Solar spectrum, 14. 
 Soluble cotton, 42 ; Hadow on, 46. 
 Spherical aberration, 22. 
 Spots upon positives, 139. 
 Stains and lines upon positives, 139. 
 
 Taupenot, M., his Collodio-albumen process, 190. 
 
 Test-paper, use of, 205. 
 
 Toning bath for positives on paper, 155. 
 
 Weights and Measures, 210. 
 

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