Book_ o GopyrigM I L- CjQZffilGKT DEPOSIT ELEMENTS OF INDUSTRIAL CHEMISTRY BY ALLEN ROGERS In charge of Industrial Chemistry, Pratt Institute, Brooklyn, N. Y. » An Abridgment of Manual of Industrial Chemistry Written by Forty Eminent Specialists and Edited By ALLEN ROGERS 117 ILLUSTRATIONS NEW YORK D. VAN NOSTRAND COMPANY 25 Park Place 1916 Copyright, 1916, by D. VAN NOSTRAND COMPANY 4i 0*L NOV 24 I9IS JCI.A4 485G7 3 PREFACE The purpose in presenting this elementary work on Industrial Chemistry is to meet the needs of those teachers of the subject who find that the time at their disposal does not warrant the employment of an extended treatise. The author, therefore, has compiled from the Manual of Industrial Chemistry an abridged volume which covers the most salient points of the larger book. The endeavor has been, in arranging this con- densation, to treat the subjects covered in a general manner only, thus eliminating as much of the detail as possible in order that the fundamental principles might be more clearly set forth. Although the subject matter is essentially descriptive, a certain amount of theoretical consideration has been included where necessary for the proper understanding of the text. Should the student desire more detailed information on the subject, or a more extended description of the processes under con- sideration he is referred to the Manual from which this book is compiled. No claim for originality is made for this volume, and full credit should be given to those who contributed to the larger book mentioned above. The book as it now stands consists of twenty-seven chapters covering a somewhat limited range of subjects, but at the same time is sufficiently broad to give the student a very compre- hensive view of the entire field. Allen Rogers. Pratt Institute, Brooklyn, N. Y. September 20, 1916. CONTEXTS PAGE General Processes Chapter I 1 Grinding — Crushing — Crushers — Mills — Disintegrator — Pulverizer — Sifting — Sedimentation — Levigation — Filtration — Filter Press — Centrifugal machine— Lixiviation — Extraction — Crys- tallization — Calcination — Furnaces — Kilns — Evaporators — Kettles — Refrigeration. Water, Its Uses and Purification Chapter II 30 Natural waters — Boiler waters — Scale formation — Incrustation — Corrosion — Foaming — Purification of water — Numerical standards — Classification — Potable waters — Sand nitration — Boiler compounds. Fuels Chapter III 49 Wood — Peat — Lignite — Bituminous coal — Briquettes — Anthra- cite — Charcoal — Water gas — Coal gas — Oil gas — Natural gas. Sulphuric Acid Chapter IV 65 Occurrence — Raw materials — Outline of process — Glover tower — Gay-Lussac tower — Sulphur burning — Furnaces — Pyrites — Burners — Dust prevention— Chamber system — Kestner lifts — Acid eggs — Platinum stills — Contact process — Silica stills. Nitric Acid Chapter V 91 Occurrence — Properties — Manufacturing processes. Elements and Inorganic Compounds Chapter VI 106 A short description of over 300 elements and compounds with a brief account of their commercial application. Ceramic Materials and Products Chapter VII 177 Lime — Kilns — Mortar — Cement — Limestone — Marl — Clays — Plaster of Paris — Kaolin — Bricks — Tile — Pottery — Stoneware — Por- celain — Glass. v vi CONTENTS PAGE Pigments Chapter VIII 203 White Lead — Sublimed white lead — Zinc oxide — Lithopone — Barytes — Whiting — Asbestine — Gypsum — Red pigments — Blue pig- ments — Yellow pigments — Black pigments — Lakes. Fertilizers Chapter IX 219 Raw materials — Blood — Tankage — Guano — Cyanamide — Fish scrap — Phosphate rock — Thomas slag — Belgian slag — Bone — Potash. Illuminating Gas Chapter X 231 Coal gas — Retorts — Hydraulic Main — Condensers — Tar Extract- ors — Exhausters — Scrubbers — Purifiers — Water gas — Lowe appa- ratus — Williamson machine — All-oil water gas — Pintsch gas — Blau gas — Acetylene. Coal Tar and Its Distillation Products Chapter XI 247 Coal tar — Retort gas tar — Oven gas tar — Producer gas tar — Blast furnace tar — Water gas tar — Pintsch gas tar — Creosote oil — Cresol — Benzene — Toluene — Naphthalene — Anthracene. The Petroleum Industry Chapter XII 262 Petroleum — Origin — Constitution — Locality — Production — Dis- tillation — Asphalt — Shale oil — Ozokerite . The Destructive Distillation of Wood Chapter XIII 277 Preparatory treatment — Distillation — Retorts — Condensers — Rosin process — Hot water process — Extraction process — Wood alcohol — Acetone. Oils, Fats and Waxes Chapter XIV 290 Classification — Constitution — Vegetable oils — Animal oils — Fish oils — Waxes. Lubricating Oils Chapter XV 317 Choice of oils — Watch oils — Spindle oils — Loom oils — Engine oils — Crank case oils — Greases — Belt dressings — Reduced oils — Soluble oils. CONTENTS vii PAGE Soap, Soap Powder, and Glycerine Chapter XVI 323 Classification — Boiling — Graining — Framing — Slabbing — Finish- ing — Boiled toilet — Milling — Plodding — Pressing — Half boiled — Soft soap — Floating- — Powders — Glycerine. Essential Oils Chapter XVII 340 Crude distillation — Modern distillation — Steam distillation — Ex- pressed oils — Macerating process — Enflurage process — Flower po- mades — Volatile solvents — Absolutes — Chemical constitution — Oils. Resins, Oleo-resins, Gum-resins, Gums Chapter XVIII 362 Sources— Constitution — Gums — Resins — Rubber. Varnish Chapter XIX 370 Definition — Classes — Outfit for making varnish — Spirit varnishes — Oil varnishes — Baking varnishes — Japan driers. Sugar Chapter XX 381 Raw materials — Cane sugar — Extraction process — Defecation process — Beet sugar — Sugar refining. Starch, Glucose, Dextrin and Gluten Chapter XXI 395 Classification — Sources — Methods of manufacture — Drying — Al- kaline starches— Grape sugar — Dextrin — British gum. Beer, Wine and Liquor Chapter XXII 406 Malting — Brewing — Grapes — The Must — Fermentation — Distil- lation. Textiles Chapter XXIII 429 Origin — Animal fibers — Vegetable fibers — Mineral fibers — Arti- ficial fibers — Bleaching. Dyestuffs and their Application Chapter XXIV 447 Textile coloring — Textile printing — Dyeing — Staining — Mordant colors — Acid colors — Basic colors — Natural colors — Azo-colors — Vat colors. The Paper Industry Chapter XXV 459 Rag paper — Wood paper — Mechanical process — Soda proeess — Sulphite process. Yin CONTENTS PAGE ...Chapter XXVI 470 powders — Nitrogly- Explosives Black powder— Nitrocellulose— Smokeless cerine— Dynamite— Fulminates. Chapter XXVII 481 Leather Raw materials-Soaking-Depilation-Bating-Chrome tannage —Vegetable tannage— Alum tannage— Formaldehyde tannage- Patent leather. ELEMENTS OF INDUSTRIAL CHEMSTEY CHAPTER I GENERAL PROCESSES GRINDING. In the manufacture of chemical products, one of the most important operations is that of grinding. Not only is it often necessary to reduce the raw material to a state of fine division before it can be used, but the finished product, in many instances, must be placed on the market in the form of a fine powder or paste. The result to be secured depends entirely upon the nature of the product or material and the purpose for which it is to be employed. Thus in many metallurgical opera- tions it becomes necessary to crush very hard rocks or ores; while on the other hand some materials, like pigments, must be sold as a very fine powder. Therefore, we have two general divisions of grinding machines — those which are used for crushing or coarse grinding and those which are used for producing a fine powder. For those materials which appear on the market in the form of a paste, special forms of grinding machines are employed. The following are some of the types of grinding machinery: JAW CRUSHER. 1 The simplest and least expensive form of crusher in use is that known as the jaw crusher. It is a very heavy type of machine and consists essentially of a stationary steel plate against which a corresponding steel jaw works on a cam, thus giving a rolling motion. The working parts may be regu- lated by means of an adjusting screw so as to give a coarse or fine product as desired. This machine is capable of crushing the hardest of materials. It finds extensive application in metal- lurgical operations where ores are to be crushed; in the manufac- ture of plaster of Paris; in crushing of pyrites for sulphuric acid 1 Sturtevant Mill Co., Boston, Mass. 2 ELEMENTS OF INDUSTRIAL CHEMISTRY manufacture and for many other purposes. On account of the strain this machine is always placed on a very solid foundation. Fig. 1 represents a small-size jaw crusher used for laboratory work which may be either hand or power driven. Fig. 2 illus- Fig. 1. Fig. 2. trates a heavy machine employed in crushing pyrites for the manufacture of sulphuric acid. CRUSHING ROLLS. 1 This type of machine is employed quite extensively for reducing the product of the jaw crusher to a finer state of division. Fig. 3 shows a laboratory roller, while Fig. 4 'Sturtevant Mill Co., Boston. Mass. GENERAL PROCESSES 3 illustrates a heavy type of machine used in metallurgical opera- tions. The rolls may be either plain or corrugated. These machines are also employed for crushing soft materials. Fig. 5 represents a battery of rollers used in crushing sugar cane, while Fig. 3. Fig. 4. Fig. 6 is a form used extensively for crushing seeds such as flax- seed in the manufacture of linseed oil. ROTARY FINE CRUSHER. 1 For rocks of moderate hard- ness the rotary crushers are almost universally employed. These 1 Sturtevant Mill Co., Boston, Mass. ELEMENTS OF INDUSTRIAL CHEMISTRY GENERAL PROCESSES 5 machines are provided with double doors that carry all of the grinding parts and swing open as easily as the doors of a safe, thus exposing every part to inspection. They are built with capacities of from 2 to 30 tons per hour. They may be regulated while running for fine or coarse work by turning the adju ting wheel. Fig. 7 represents such a mill, which finds extensive application in the grinding of cement rock. CHASER. 1 There are many materials which, owing to their peculiar nature, cannot be crushed by means of the machines r\ Fig. 7. Fig. described above. Such substances as drugs, clays, and putty are handled in the chaser. It is also employed in mixing bams for use in the foundry, for mixing mortar and for mixing and grinding to a semi-dry state. The chaser is constructed with a stone or steel bed on which rotates one or two " edge runners " or " travelers." An arm provided with a scraper travels just in front of the runners, which brings the material under the heavy rollers, while the whole is set in a pan arranged with a gate for discharging. Fig. 8 shows such a machine. 1 Chas. Ross & Sons Co., Brooklyn, N. Y. 6 ELEMENTS OF INDUSTRIAL CHEMISTRY DISINTEGRATOR. 1 This type of machine, also known as pulverizing mill, is especially adapted for such materials as are of a lumpy nature, such as dry colors, soft pigments, borax, sul- phur, starch, etc. ; also for mixing dry materials, such as fertilizers, for example. The construction of this machine is very simple, Fig. 9. Fig. 10. as will be seen from Figs. 9 and 10. The steel cages run at a very high speed in opposite directions, thus driving the material through the steel bars by centrifugal force, and pounding it to a powder. They are strongly built, and may be easily and quickly cleaned by taking off the top half of the casing, 1 Chas. Ross & Sons Co., Brooklyn, N. Y. GENEEAL PEOCESSES removing the bolts holding bearing frames to bed plate, then drawing frame and cages apart by tail screw, as shown in the illustration. BUHR STONE MILL. 1 For the fine grinding of dry or wet materials this type of mill is in very common use. Fig. 11 shows an under-driven dry mill, which is open in order to give an idea of the grinding surfaces. This mill is employed for the grinding of soft materials such as flour, pigments and dry colors. Fig. 12 Fig. 11. Fig. 12. is the Ross improved paint and color mill ready for work. This mill is provided with a double set of stones having a water- cooling arrangement to prevent excessive generation of heat in the grinding of paste colors and paints. In using these mills the material is fed in through the hopper and by centrifugal force is carried to the grinding parts of the first set of stones, from which it then passes to the second set. The degree of fineness is regulated by means of set screws on the side. For paste and paint grinding it is necessary to provide a scraper on 1 Chas. Ross & Sons Co., Brooklyn, N. Y. 8 ELEMENTS OF INDUSTRIAL CHEMISTRY the traveling stone to remove the product as it passes the grinding face. BALL MILL. There are many types of these mills on the market which find application in various lines of industry. Among the most commonly used of these mills might be mentioned the Fuller-Lehigh pulverizer, Fig. 13, largely employed in the manu- facture of cement, which consists of a horizontal ring or die against which revolve four balls. The balls are propelled by means of pushers. The die and pushers are chilled charcoal-iron castings. The balls are of steel forgings. They revolve at a speed of about 155 R.P.M., and hence press against the die with enormous centrifugal force. The ma- terial to be ground is fed into the hopper which serves the feeder. The material discharged by the feeder falls down into the pan of the mill, situated below the die, and is drawn up from this in between the rapidly revolving balls and stationary die by means of air currents induced by fans placed in the chamber above the die. The ma- terial is pulverized by the rolling of the ft^^^^ G^lifeo balls against the die, the grinding action being similar to that of a mortar and pestle. The finely pulverized material is sucked upwards by means of the fans and out through the screens. The ma- terial passing through the screen falls down between this screen and the outer casing, and is discharged from the mill through the discharge spout, which may be placed at any one of four quarters of the mill. The feed to the mill and consequently the fineness of the product, may be con- trolled in two ways — either by a slide on the hopper or by means of the stepped pulley, connected to the screw conveyor by gearing. The mill is provided with two screens, one — the inner — of 1-in. mesh and made of very heavy wire to protect the outer one. The outer screen does not really screen, but merely controls the draft of air, and hence the fineness, since the greater the velocity the greater the carrying power of the air, and hence the coarser the product. GENERAL PROCESSES 9 The Griffin mill is somewhat similar to the Fuller-Lehigh mill in operation. It consists of a steel die against which a roll also of steel is made to revolve, and it is between these two that the material is ground. The roll is suspended by a shaft from a spider, and actuated by a pulley and a universal joint. The fully ground material is sucked up and forced through the screens. The coarse particles fall back into the pans of the mill and are thrown up between the roll and the die by means of a plow attached to the roll. The finished product passes through the Fig. 14. screen and travels from these to the outer casing and thence through openings in the base of the mill to screw conveyors. PEBBLE MILLS. 1 Pebble mills grind principally by friction, the effect being produced by the sliding, tumbling and rolling- inside of the mill of a great number of flint pebbles or porcelain balls which are mixed with the substance to be ground. The movement is caused by revolving the mill at a regulated speed. As pebble mills are not crushers, all material should be crushed to a certain degree of fineness before being charged into the machine. The mill shown in Fig. 14 is lined with vitrified por- 1 Abbe Engineering Co., New York City. 10 ELEMENTS OF INDUSTRIAL CHEMISTRY celain, thus presenting a grinding surface which will neither contaminate nor discolor the material being pulverized. TUBE MILLS. The general principle of grinding employed by the tube mill is the same as in the ordinary pebble mill, the difference being that the material to be ground in the tube mill is fed in at one end and is delivered as a finished product at the other, the fineness of the product being regulated simply by the speed at which the material is fed into the machine. The slower the feeding the longer the material receives the action of the pebbles and the finer the discharged product will be. To make a coarse material the feeding is increased. Some of the more modern forms of tube mills are provided Fig. 15. with a " spiral feed." By means of a crescent-shaped opening located where the spiral starts, a certain quantity of the material is allowed to enter, and as the machine revolves this travels forward until it reaches the center, where it enters the grinding chamber. Thus after two or three revolutions there is a constant feed of a regular amount of material. From the grinding chamber the product passes through a perforated plate into a reverse spiral and thence is discharged from the center of the machine. In this way all labor of shoveling pebbles is avoided. ROLLER MILLS. 1 For the grinding of lithographic inks, colors in varnish, chocolate and many other pasty materials the 1 Chas. Ross & Sons Co., Brooklyn, N. Y. GENERAL PROCESSES 11 above methods cannot be satisfactorily employed. The roller mill, Fig. 15, obviates the difficulties encountered and is largely used for the purposes mentioned. In their construction these machines usually consist of three steel rolls, which rotate at different speeds, thus passing the product to the front, where it is detached by means of a scraper, and falls onto the apron. By means of adjusting wheels the front and back rolls are under perfect control, and may be set to any degree of fineness desired. SIFTING. In those instances where the substance being treated is ground in a dry condition, it is often necessary to separate the coarse from the fine material. This is accomplished by the use of sifting or bolting machines, there being numerous forms and styles employed for the purpose. The degree of fine- ness is regulated by using either wire sieves or bolting cloth. In all cases the ground material enters the reel, and as this rotates the fine powder passes through the meshes, leaving the coarse particles in the reel. SEDIMENTATION. In order to overcome the annoyance and loss caused by flying dust, many materials are ground in water. As the resulting turbid liquid comes from the mill it is allowed to flow into the first of a series of tanks, where the coarser and heavily particles rapidly subside, leaving the finer substance in suspension. The liquid is then drawn to the second tank, where it is allowed to remain somewhat longer than in the first tank. In each of the subsequent tanks the liquid is allowed to remain for a longer period than in the one previous, thus giving various degrees of fineness to the resulting product, the coarse particles being returned to the mill for further grinding. This operation is sometimes spoken of as " levigation." FILTRATION. By this process is meant the separation of suspended solids from a liquid, and often presents grave difficul- ties; especially is this so when working with large volumes. The medium employed may be paper, cloth, cotton, wool, asbestos, slag or glass-wool, unglazed earthenware, sand or other porous material. RIBBED FILTER. For handling small amounts of material the ribbed filter is very convenient, and consists in folding an ordinary large filter in such a manner that when inserted into the funnel it will leave canals along the side. To prevent breaking of the filter the tip should be forced well into the neck of the funnel. 12 ELEMENTS OF INDUSTRIAL CHEMISTRY BAG FILTER. A very satisfactory method of filtering coarse material is to arrange four pieces of wood as shown in Fig. 16, and on the brads suspend a piece of muslin in such a manner as to form a bag. The portion passing through at first may be slightly cloudy, but as the pores fill with the precipitate the filtrate becomes clear. Suction Filter. This form of filter is used very largely where it is desired to retain the filtrate as well as the solid matter. It consists of a box arranged so that the lower section is connected with the vacuum pump, and over the perforated bottom is placed canvas or other filtering medium. FILTER PRESS. A very rapid and con- venient method of filtration is by means of the filter press. Although they are all built on the same principle, their details of construction vary to a marked degree. In its simplest form, how- Fig. 17. ever, it consists of distance frames and plates. These plates and frames rest upon a pair of parallel bars, and are held in position by means of lugs projecting from each side. Over the surface of each plate is stretched a filtering medium, usually cloth, which is held in GENERAL PROCESSES 13 place by means of pegs, the whole being forced against the adjacent frame by means of a screw or hydraulic pressure. The material to be filtered is forced through the channel along the top of the press and into the distance frames. The solid material is held back by the filtering medium, gradually filling the chambers and producing a solid cake. The liquid which passes through the filter is allowed to discharge into the channels along the lower por- tion of the press, where it may be recovered or discarded as wished. A more recent form of filter press is the Sweetland self-dump- Fig. 18. ing filter, shown in Fig. 17. The material to be filtered is forced into the filter body by gravity pressure or by means of a pump. The filter body comprises two semi-cylindrical castings of high tensile strength. As soon as the filter body is filled, the pressure rises, causing the liquid portion to pass through the filter cloth, while the solid matter is deposited on the leaf in a compact form. When the filter is full the bottom half of the body is lowered, and then by reversing the pressure the cake is easily and very quickly detached. Centrifugal Machine. 1 This appliance is used for sepa- 1 American Tool and Machine Co., Boston, Mass. 14 ELEMENTS OF INDUSTRIAL CHEMISTRY rating liquids from solids. It is especially adapted to the drying of crystals in that it throws off the adhering mother liquor by centrifugal force. It is also employed for drying yarns, textiles, wood pulp, sugar, starch, etc. The centrifuge, therefore, is used more as a means of drying than of filtration. It consists of a cylindrical perforated basket fixed to a vertical shaft, which rotates at a very high speed (900 to 1200 revolutions per minute), Fig. 18. * By means of the centrifugal force generated the contents of the basket are driven to the outer wall, where the solid material is detained, and the liquid thrown off. In working with the Fig. 19. machine great care must be exercised lest grave accidents occur. It is also necessary to see that the machine is carefully con- structed. DRYING. Before submitting material to the dr3 7 ing process proper it may be advantageous to remove as much of the adher- ing liquid as possible by draining, filtering, or centrifuging. The water that still adheres is now removed by evaporation in contact with the air at as high a temperature as compatible with the substance and economical practice. Whenever waste heat is available it should be used. In order that drying should be uniform the substance to be dried is stirred, usually by mechanical appliances. The simplest GENERAL PROCESSES 15 arrangement would consist of a platform of metal or stoneware heated by flue gases and upon which the material would be spread and stirred from time to time; this is not, however, an economical process. A less wasteful method is by the use of drying chambers, built of brick, wood, or metal. The chamber may be heated from the inside, or the air passing through it may be heated. To aid in the removal of the moist air an exhaust or fan is usually employed. Where temperatures of 100° C. or less are desired the air may be heated by passing it over steam-heated coils, or the plate on which the material is placed may have a steam-heated jacket. As the point at which the heat enters the apparatus, be it steam or flue gases, is the point of greatest heat, it is usual to provide for the conveying of the material from the further and cold end of the apparatus toward the hottest portion. For this purpose the shaft furnace can be used, provided the material is hard enough and there is no need of regulating the temperature very carefully. A large number of more or less efficient forms of dryers are manufactured, among which vacuum dryers, in which the drying is done at a considerable saving of labor, fuel and time, are the most important. Vacuum dryers may be divided into shelf dryers, Fig. 19, for material that does not need to be stirred while drying; rotary dryers for material which must be continuously stirred; and drum dryers for substances like glue, which readily forms a dry film on the surface. LlXTVIATlON. The process of lixiviation consists in the separation of water-soluble material from insoluble or less soluble material. The substance to be treated with water may be sus- pended in bags or baskets, or placed in tanks provided with perforated false bottoms. The solution, being denser than water, sinks to the bottom and may be removed. The material is usually submitted to a systematic treatment with water, in such a manner that the pure water first comes in contact with the nearly exhausted substance, and then with the less exhausted in another tank, and so on until it reaches the last tank containing the fresh material. Such a series of tanks is known as a battery. The term extraction is generally used when solvents other than water are employed. It is possible to extract several substances from the original raw material by the successive use of several solvents such as water, alcohol, ether, and naphtha. CRYSTALLIZATION. Crystals are geometric solids which may form by the separation of a compound from its concentrated 16 ELEMENTS OF INDUSTRIAL CHEMISTRY solution. The solubility of most substances increases as the temperature of the solvent, usually water, is raised. A limit may be reached, however, for every temperature when no more will dissolve, and the solution is said to be saturated. If the temperature be now decreased, crystals of the substance will separate; and these crystals, though formed in an impure mother liquor, may be quite pure. By evaporation or concentration of the mother liquor more crj^stals will result, which, however, will be less pure than the first crop. Thus this operation may be continued until the impurities accumulating in the liquor become so great that the crystals will enclose a large amount of foreign matter. This difficulty can be prevented to a certain extent by stirring the solution while crystallization takes place; this causes the separation of very small crystals, or crystal meal, which can then be washed so as to remove the adherent impurities. This process is usually spoken of as " Granulation." Fractional Crystallization. Crystals may be further purified by several successive recrystallizations. This is a method used for the separation of substances when mixed in a solution; isomorphous substances, that is, those crystallizing in the same system cannot, however, be separated in this manner. The only way to proceed in such a case is to so react upon the solution as to change the chemical composition of one of the substances in such a manner that separation by crystallization becomes pos- sible. As an instance of this may be mentioned the preparation of pure copper sulphate from a mixed solution of copper and fer- rous sulphates. When blue vitriol is made from copper pyrites it is usually accompanied by more or less green vitriol. From this mixed solution only crystals of copper sulphate mixed with iron sulphate can be obtained, these salts being isomorphous. By oxidizing the ferrous to the ferric sulphate this may be avoided and pure copper sulphate prepared. CALCINATION. In the process of calcination substances are submitted to the action of high heat, but not, however, to the point of fusion. Material may be calcined: to drive off moisture, to drive off some volatile constituent or cause a chemical action such as oxidation or reduction. The terms roasting, firing, glowing, or burning are sometimes used in place of calcination. The process is usually carried on in furnaces, of which there are three common types — reverberatory, muffle, and kiln. REVERBERATORY FURNACE. In the reverberatory or open roaster the material to be heated is exposed to the direct action GENERAL PROCESSES 17 of the fire gases. It consists essentially of an arched chamber built of brick and heated from a grate placed at one end, while the products of combustion and reaction are removed by a chimney at the other end. The material is placed upon the bed of the furnace, the fire gases pass over it and are deflected by the arched form of the roof of the furnace so as to come more directly in contact with the charge. The insides of such furnaces are lined with firebricks, while the outsides are built of common bricks. If an oxidizing reaction is desired, that is, if the fire gases are to contain an excess of oxygen, such condition may be produced by setting the fire bars widely apart and feeding the fuel in thin layers at a time. Should a reducing action be desired, the fire bars must be placed closer together and the fuel charged in thick layers. MUFFLE FURNACE. The muffle furnace, closed or blind roaster is built in such a manner that the fire gases do not come in contact with the substances to be calcined. It generally con- sists of a muffle of firebrick with the flues so arranged that the hot gases pass underneath the bed of the muffle and are then con- ducted over the top, back to some point near the grate, where they are discharged into the chimney. A pipe is sometimes fitted to the top of the muffle in order to discharge any gases which may be formed during calcination. REVOLVING FURNACE. It is frequently necessary to stir the material during calcination, which would entail much heavy labor if done by hand ; to obviate this, me- chanical means have been devised, the most important of which is the revolver or revolv- ing furnace. It consists of a drum or cylinder of iron or steel, Fig. 20, lined with refractory material and open at T both ends. The drum, which may or may not be inclined, revolves slowly about its longitudinal axis, while the highly heated gases, from the grate situated at one end, pass through it. The hot gases leaving any of these furnaces may be economically used for drying or evaporating. W^W 18 ELEMENTS OF INDUSTRIAL CHEMISTRY KILNS. Kilns or shaft furnaces may be periodic or continuous, and are very largely used in the burning or calcination of lime- stone. In periodic kilns the calcined charge is allowed to cool, then withdrawn and the kiln recharged with fresh material. In the continuous form the calcined material is drawn from the bottom at the same time that a fresh charge enters the top, the operation being a continuous one. EVAPORATION. By evaporation is understood the conver- sion of a liquid into a vapor for the purpose of recovering any solid matter which may be dissolved in it. In most instances the liquid to be evaporated is water. Other liquids would be recovered, and the process termed distillation. Spontaneous Evaporation. This method is usually conducted in the open air by exposing the liquid in large shallow pans. The time required depends entirely upon atmospheric con- ditions, the best results being obtained on a windy day in hot, dry weather. Evaporation by Direct Heat. By this method the flames or hot gases may play directly on the bottom of the con- taining vessel, or they may be made to pass over the surface of the liquid. In the former case the usual method is to employ large shallow pans which are so arranged as to be heated from the waste gases from other operations. In the latter mode of evapo- ration, the flue dust and ashes are very apt to fall into the pan, thus causing the product to become impure. This method is used, however, to some extent where the purity of the product is not essential. Evaporation by Indirect Heat. The use of steam is very largely employed for the reason that it is convenient to handle, and there is no danger of injury to the product by over- heating. The simplest means of utilizing this method of heating is to circulate the steam through coils of pipe arranged inside the vessel. This method is especially adapted to the heating of liquids contained in wooden tanks. The temperature to which the liquid may be raised depends wholly upon the steam pres- sure, which may be regulated to suit the conditions required. STEAM- JACKETED KETTLES. The most convenient method of applying steam is by means of the steam -jacketed kettle, a cut of which is shown in Fig. 21. In conducting an evaporation the valve to drain pipe is opened in order to allow the first con- densations to escape, and to prevent bumping. The exhaust valve is now opened, the inlet valve given a half turn, and then GENERAL PROCESSES 19 slowly opened until a good supply of dry steam issues from the drip. The drip is finally closed and the inlet of steam so regu- lated as to secure the proper heat for evaporation. The kettles in common use are constructed of copper or cast iron, the jacket usually covering one-half of the kettle. For purposes where copper or iron will not resist the action of acids or other chemicals, it is customary to employ an enamel- lined kettle, which enamel consists of an easily fusible glass. In many operations it is necessary to stir the liquid being evaporated, to accomplish which the kettle is generally equipped with an agitator provided with paddles of various shapes. Fig. 21. Recently several forms of acid- proof iron have been brought on the market, Vessels constructed of these materials appear to be giving entire satisfaction. Evaporation under Reduced Pressure. There are many forms of apparatus employed for evaporating under reduced pres- sure, yet they all depend upon the same principle. VACUUM PAN. The necessary equipment for this installa- tion is a vacuum pan, condenser, receiver and pump. The pan is usually a globular copper or iron vessel, which is provided with a manhole, a discharge opening at the bottom, a thermometer, a vacuum gauge, peep holes, test cocks, liquor gauge and catch- all. In most of the larger pans the heating is accomplished by means of steam coils placed in the bottom of the pan, while the smaller sizes have a steam jacket. At the top of the pan is a dome or large pipe connected with the " catch-all," the purpose of which is to retain any liquid that may be carried along mechan- ically by the steam. A small pipe at the bottom of the catch-all returns the water to the pan, while a larger one is connected to the condenser. The condenser is a tin-lined copper coil sur- rounded by running water. Joined to the condenser is the receiver, which, like the pan, is provided with a liquor gauge. Attached to the receiver is the pump which in such an apparatus would be one working on the dry system. In many cases, how- ever, it is not necessary to collect the liquid passing off, so that it is then possible to dispense with the condenser and employ 20 ELEMENTS OF INDUSTRIAL CHEMISTRY a vacuum pump which works on the wet system. A wet-system pump is so constructed as to take care of all condensations with- out the aid of an extra condenser. Multiple-effect System. The most efficient method of evaporation is that secured by means of the multiple-effect system. The apparatus usually consists of three or four vacuum pans, so arranged that the steam from the first pan passes through the coils or jacket of the next in line, and the steam generated in the second serves to heat the liquid in the third. The vacuum maintained in each of the pans increases as it approaches the pump for the reason that the condensations play quite an impor- tant part in producing reduced pressure. Thus it is that the pan having the highest temperature has the least vacuum, and that having the greatest vacuum has the least temperature. As a rule only three pans are employed, being known as triple effect, although sometimes four are used, when they are known as quad- ruple effect. YARYAN EVAPORATOR. This apparatus consists of a large number of small tubes joined together in groups of six, each group of which is a unit. The tubes of each set are joined in such a manner as to form a continuous coil, each end of which is free, the whole being enclosed in an outside shell of boiler plate. In the operation of this apparatus the steam is allowed to enter the cylindrical chamber surrounding the series of tubes. Either exhaust or pressure steam may be used, as desired. The solution to be concentrated is passed into the coils under pressure and being highly heated is converted into a mass of foam, which finally escapes from the last tube of the coil into the separator. Here it is discharged with considerable force against baffle plates, thus separating the liquid from the steam. The liquid collecting in the separator of the first effect is forced into the coil of the second effect, while the steam produced in the first effect is con- ducted into the chamber surrounding the tubes of the second effect, where its heat is utilized for further evaporation of the solution; thus the operation is repeated throughout the entire system. The steam from the final effect is passed into a con- denser, which in its turn is connected to a vacuum pump, thus producing a high vacuum in the separating chamber and coils. Owing to the reduction in the boiling-point of the liquid there is a condensation of the steam as it strikes the cooler pipes, thereby producing a less perfect vacuum in the preceding effect. Thus we have a gradual reduction of pressure and consequent GENERAL PEOCESSES 21 lowering of the boiling-point from the time the liquid enters the first effect until it is discharged from the last. The condensed steam, entrainments, from the chambers surrounding the coils, together with that from the condensers, is collected in many factories, and may be employed as feed-water for boilers or for other purposes. The ordinary form of vacuum pan will evaporate from eight to ten pounds of water per pound of coal, while it is claimed that the triple-effect Yaryan will evaporate from 23 to 25 lbs., and the quadruple effect 30 lbs. LlLLIE EVAPORATOR. 1 The mode of operation which dis- tinguishes the " Lillie " from other forms of apparatus is that the results obtained are due to film evaporation; that is to say, the liquid flows over the heated tubes rather than through them, thus exposing a very large surface for evaporation. In the older forms of multiple-effect apparatus some difficulty was encountered from liquids which deposit heavy incrustations on the heating surfaces. This difficulty, how- ever, has been overcome in the new model. The new feature, which corrects this condition, is the reversal at will of the direction of the course of the vapors or heat through the multiple effect, making there- by, what before the reversal was the hottest effect the coolest, and what was the coolest the hottest. Fig. 22 shows a vertical longitudinal section through the body cf the evaporator. The evap- orating tubes incline slightly downward to the steam end and open through the heavy tube plate partition in which they are firmly expanded and by which they are supported. The other ends of the tubes are closed save for a small air vent in each. They are not fastened or supported in any way, and the tubes are quite free to expand or contract independently of the shell of the effect. On the under side is a centrifugal circulating pump, located midway between the ends of the evaporator. The condensation from the steam in the tubes flows back into the steam end, and 1 The Sugar Apparatus Manufacturing Co., Philadelphia, Pa. Fig. 22. 22 ELEMENTS OF INDUSTRIAL CHEMISTRY thence through a steam trap into the end of the next cooler body, and finally to the atmosphere from the coolest body, in the case of the multiple effect. The solution delivered by the centrifugal pump is forced on to a perforated distributing plate, from which it flows over the tubes in a deluging shower. The circulation in this case is independent of ebbulition, and there being no depth of solution on the tubes the vapors have a free passage for escape. The method of heating and securing the reduced pressure is very similar to that of the Yaryan just described. Fig. 23. Another form of evaporator is shown in Fig. 23, which is self- explanatory. Distillation. This operation is. usually for the purpose of separating certain liquids from other liquids, or from solids, and may be considered as a special form of evaporation. In fact, evaporation and distillation are often carried on simultaneously. Many forms of distilling apparatus are in use, although they all have three points in common: (1) The still or vessel holding the liquid to be heated, (2) the condensers or cooling apparatus, and (3) the receiver or vessel in which the distilled liquid collects. Between the still and condenser is a spray catch, provided with baffle plates, to prevent any of the solution from being carried over mechanically by the vapor. By this means the liquid is returned to the still while the vapor passes along to the condenser. GENERAL PROCESSES 23 represents one The column or The apparatus shown is made of copper, the condenser worm being tin lined. COLUMN STILL. The illustration, Fig. 24 of the types of column stills in common use. dephlegmator B is placed on top of the boiler A and is divided into chambers by means of plates, each of which has a dome or flat-covered opening, with an overflow pipe lead- ing to the chamber below. The vapor from the boiling liquid passes up through the opening, where it bubbles out through the liquid on each plate. The heavier liquid which is condensed here flows down through the overflow pipes and into the boiler. Between the column and the condenser E is a series of U-tubes surrounded by a water- bath, which may be kept at any temperature desired. As the mixed vapors pass through these tubes, the high-boiling portions are condensed and returned to the column, while the lightest or more volatile liquid only passes through the coil in the condenser E. COFFEY STILL. This form of apparatus, Fig. 25, consists of two towers: A known as the analyzer and B the rectifier. Free steam is forced into A through the pipe C, where it bubbles up through the liquid on the perforated plates D, D and out by the way of E into the rectifier B. The liquid to be dis- tilled is now pumped through the pipe F and the coil G, G, and is delivered into the analyzer by the pipe H. The liquid in this way becomes heated by the steam surrounding the coil and is delivered hot to the analyzer. The hot liquid as it falls on the perforated plates spreads out in a thin layer, and runs down to the next compartment through the overflow pipe J. The steam, as it passes up through the layers of liquid, heats it very hot and carries the volatile portion over into the rectifier. During the passage of the mixed vapors up the rectifier the steam becomes condensed by contact with the cold pipes, thus allowing the more volatile portion to pass out through the pipe K to the con- denser L. The water which collects in the bottom of the Fig. 24. 24 ELEMENTS OF INDUSTRIAL CHEMISTRY rectifier is pumped to the top of the analyzer through the pipe M. From the bottom of the analyzer is a pipe N to act as a dis- charge for the spent liquor which has lost its volatile matter. CONVEYING SOLIDS. The man with a wheelbarrow is the sim- plest method of conveying solids, and is at the same time the least economical. A steel tray or wheelbarrow weighs from 60 to 70 lbs., and will hold about 2 cu.ft. In a general way the laborer pushes the barrow through 200 ft. in a minute, and con- sumes about one and one-half minutes for loading and unloading. Larger barrows are made with two wheels, weighing from 200 to 250 lbs., and having a capacity of 8 to 9 cu.ft. As a rule barrows are used on level surfaces only, and are made of various Fig. 25. shapes for special purposes. In some cases it is advisable to lay steel tracks and draw the cars by means of electric motors or small locomotives. The arrangements for dumping the cars vary to some extent, but of the ones in common use may be mentioned the V-shaped dump car, the gabled or saddle- bottom dump car and the hinged-end dump car. Cars which have to go up a steep incline may be hauled by a wire cable or run into an elevator. Endless chains or cables provided with catches to hold the car while it is being drawn up the incline are much used, especially for mining operations. An aerial cableway is often used where the country is rough and where it is necessary to cross a stream. The cable or wire rope is sus- pended from towers. The cable is usually endless, and along it are run carriages to which skips or buckets are attached. Material GENERAL PEOCESSES 25 may also be moved by the use of the revolving locomotive crane with clamshell bucket or other form of container. A very effi- cient form of transportation is by means of the belt conveyor. These belts are usually made of rubber or cotton. The rubber belts (cotton duck coated with rubber) are especially designed for rough usage, while the cotton belts are more often employed for the carrying of boxes and packages. The belts, which may be flat or troughed, are run on rollers for support, the motion being imparted by a head pulley, and the slack taken up by the foot pulley. Different types of rollers are used according as the belt is flat or trough shaped. The capacity of such a conveyor depends upon the width of the belt and its speed, a troughed belt being able to carry two or three times as much load as a flat one. For the transportation of hot or very rough material bucket conveyors are generally employed. These buckets are carried on rollers and are joined together by a roller chain. Apron con- veyors are made by attaching light strips of wood or metal to link chains, thus forming a continuous belt much used for handling light packages. In drag or flight conveyors the material is pushed along, the simplest form being one in which the plain scraper is drawn by a central rope or wire. In the suspended draw conveyor the flights are attached to crossbars having wearing shoes at either end which slide on angle-iron tracks. In the roller flight con- veyor the shoes are replaced by rollers. The screw conveyor consists of a shaft around which metal flights are bolted to form an endless screw, this shaft rotating in a trough pushes the material along. When material is to be lifted any distance it is done by bucket elevators. The buckets are fastened to belting or link chains. A bucket shaped like the letter L is easily discharged, and is there- fore largely used for conveying pasty material; those shaped like the letter V have a larger capacity, but do not empty so readily as the L-shaped. The buckets may be made of steel, malleable iron or copper, according to the use to which they are to be put. They are also sometimes perforated to allow the material to drain, while others have saw edges, as those used for lifting tan- bark and such material. The belt to which the buckets are attached passes over two pulleys and the material is discharged by centrifugal force as it goes over the top one. For conveying barrels and boxes special elevators have been designed. 26 ELEMENTS OF INDUSTRIAL CHEMISTRY CONVEYING LIQUIDS. The simplest problem which presents itself is the conveying of a liquid from a higher to a lower level, in this case gravity is the motive force; that is, the liquid is made to flow by means of a head. Liquids are usually conveyed in pipes which may be made of a variety of materials. For water, galvanized, or cast iron, lead, copper, tin, and alloys as well as ebonite are used. Earthenware and cement pipe are used exten- sively for waste material. Glazed pipe or vitrified tile find appli- cation for acid liquids; they are rather fragile, however, and should not be exposed to over 20 lbs. pressure to the square inch. Wooden pipes which are made of staves bound together with steel bands are much used for beer, vinegar, organic acids and dilute mineral acids. Lead pipe is very valuable in chemical industry, as it resists corrosion, but is not satisfactory when exposed to heat or pressure; for this reason iron pipes which are lead lined are much employed. Tin pipes are sometimes used in breweries, and for conveying distilled water, carbonated water, vinegar and wine; but owing to their expense tin-lined copper or iron pipes are more generally employed. Copper and brass pipes find extensive application, especially for conveying and use in the manufacture of dye-wood extracts and tanning materials. Wrought iron, either plain or galvanized, is used for the distribution of water, while cast-iron pipes are employed for conveying concen- trated acids. Elevating LIQUIDS. The most common method of lifting liquids is by means of pumps, which may be driven by steam, electricity, water, belt or gear. The pressure secured in a plunger pump is due to the force of a piston, while in a centrifugal, the pressure is obtained through a rotary motion imparted by means of revolving fans. The pulsometer and hydraulic ram are used to a limited extent. To withstand the action of acid and alkaline solutions, pumps are made of various materials; but for the elevation of more corrosive liquids the acid egg is generally used. Acid eggs are usually made of acid-proof cast iron and heavy enough to with- stand the necessary pressure; they are also sometimes made of earthenware. To operate, it is allowed to fill with the liquid, the ingress closed, then by the admission of compressed air the liquid is forced through a tube. The Harris system of elevating liquids by compressed air consists of two cylinders, opening into common fill and discharge pipes, the cylinders being filled by suction and discharged by pressure. GENERAL PROCESSES 27 Where a liquid is to be transferred from a higher to a lower level the siphon is the simplest and most economical appliance which can be used. The simplest method to start the flow is to fill both limbs with the solution, and plunge the short arm into the liquid contained in the upper vessel. A very convenient form of siphon can also be arranged by having a swivel pipe attached to the bottom of the tank, and lower it to the proper level by means of a chain. Liquids are sometimes raised or conveyed by means of injec- tors which are usually operated by steam, and whose efficiency depends upon the principle of the difference in velocity of a jet of steam issuing from an orifice and that of a jet of water. The solutions raised by an injector become heated and diluted by the condensed steam. CONVEYING GASES. Gases, if valuable for manufacturing purposes as well as those which are of no use have to be conveyed from one part of the plant to another, or entirely removed, as the case may be. The pipes used for this purpose may be of sheet iron, galvanized iron, cast iron, or wrought iron, as well as flues of brick, concrete, and lead-lined wooden ones. Gas blowers and exhausters are made either to overcome a low counter-pressure or rarefaction such as blowers and ventilators; or to overcome high counter-pressure, or exhaust against a high rarefaction. These go under the name of compressors and exhausters. Fan blowers consist of a number of blades fixed on a rapidly revolving shaft; they are only used where the counter-pressure is very slight. In pressure blowers the width of the blades are parallel with the shaft and enclosed in a casing, usually of metal. The higher the speed at which the blades revolve the greater the pressure. Chimneys are often used to carry off noxious gases as well as to create a draft and promote combustion of fuel. For a good draft height is especially desirable, while for the removal of noxious gases size is perhaps the more important. Forced draft may be produced by blowing air through the flues or by exhaust- ing the gases formed during combustion. That chimneys deliver noxious gases at a sufficient height to prevent deleterious action on vegetable and animal life should also be taken into consider- ation. REFRIGERATION. The principle involved in all refrigerating machines is the absorption of heat by the evaporation of a volatile liquid. The substances in most common use are liquefied 28 ELEMENTS OF INDUSTRIAL CHEMISTRY ammonia, sulphur dioxide, and carbon dioxide. The one most commonly employed, however, is ammonia, and it is used both in the compression and the absorption systems. Compression System. The gas being heavily compressed is liquefied by passing it through coils over which cold water is allowed to flow ; the liquid is then passed through a small opening into a large coil of pipe. The expansion of the ammonia from a liquid, to a gaseous state causes the absorption of much heat, with the result that the temperature falls below the freezing- point of water. The gases formed in the expansion pipes are rapidly exhausted by means of a pump and returned to the com- pressor, where the cycle is repeated, it being necessary only to supply sufficient ammonia to replace that lost by leakage. For the manufacture of artificial ice the expansion coils are surrounded with a strong brine or calcium-chloride solution, into which galvanized-iron boxes filled with water are immersed. When used for cold storage it is desirable to increase the cool- ing surface of the expansion coils. To do this cast-iron disks are placed at frequent intervals on the pipe perpendicular to its line of direction and the pipes suspended from the ceiling of the room. Absorption System. The York absorption refrigerating ma- chine consists of a generator, analyzer, dehydrator, ammonia condenser, ammonia receiver, exchanger, weak aqua cooler, absorber, strong aqua tank, aqua ammonia pump and pressure gauges. In operating this machine steam is admitted to the generator coils, thus heating the aqua ammonia to boiling. The liberated gas parses upward through the analyzer, which is mounted on top of the generator, where some of the water still left in suspension in the gas is removed by coming in direct con- tact with the incoming strong aqua ammonia from the absorber. On leaving the analyzer the gas enters the top of the dehydra- tor, where the remaining water is condensed. The now anhydrous gas enters the ammonia condenser, where it is liquefied, and drawn into the anhydrous liquid ammonia receiver. From this receiver it is admitted to the evaporating coils in which the refrigerating effect is produced. The expanded gas from the evaporating coils then enters the absorber, where it comes in contact with weak aqua ammonia, thus producing a solution of strong aqua ammonia. The strong aqua ammonia overflows from the absorber into a strong aqua tank; the aqua ammonia pump, taking its suction from this tank, discharges the strong aqua ammonia into the GENERAL PROCESSES 29 exchanger at the bottom of the shell. In passing through the exchanger the liquid becomes heated to within 35 to 40° F. of the temperature of the generator by the weak aqua ammonia from the generator. On leaving the exchanger the strong aqua ammonia enters the top of the analyzer, where it is still further heated by passing over the baffle plates and coming in direct contact with the liberated gas from the generator. From the analyzer it enters the generator at very near the temperature due to the steam coils of the generator, is again boiled, and the cycle repeated. CHAPTER II WATER, ITS L USES AND PURIFICATION Composition of Natural Waters. All natural waters contain, dissolved or suspended in them, more or less of all materials with which they have come into contact. The;efore absolutely pure water cannot be obtained for industrial purposes, and the fitness of natural water for use in any given process depends on its content of other substances. In general waters from regions of old rocks like granite are low in mineral content; those from regions of limestone are hard; those from regions of alkali deposits are high in sodium and potassium; and those from swampy regions are highly colored.. Surface waters flowing through districts of easily disintegrated material like clay are muddy. The drainage from basins with low rainfall is more highly mineralized than that from more humid areas. Ground waters are usually higher in mineral content than surface waters in the same locality, though this superiority is somewhat counterbalanced by the fact that most ground waters are clear, while surface waters are frequently very muddy. USES OF WATER. In judging the value of a water from its analysis it is necessary to consider the supply both in relation to its intended use and in relation to other available supplies. Besides its domestic use, water is essential in steam making, paper making, starch manufacture, and many other industrial processes. For each of these applications the amounts of certain ingredients in the water determine its value and assist in its classification. For example, considerable iron in a water may be harmful in one process and harmless in another. The value of a water for another process may be directly measurable by the amount of suspended matter, the amount of dissolved matter not being significant. It is obvious that the chemical composi- tion of other available supplies should be taken into consideration, because the best water that can be obtained at reasonable expense should be used. Therefore, the best practice is to consider the 30 WATER, ITS USES AND PURIFICATION 31 quality of the water in relation both to its application and to other local supplies. WATER FOR BOILER USE. The chief industrial use of water is for steam making, and its value for that purpose depends pri- marily on the amount and the chemical character of the mineral matter dissolved and suspended in it. The troubles in boiler- room practice caused by the mineral constituents of natural waters are scale formation, corrosion, and foaming. FORMATION OF SCALE. Formation of scale is the deposition of mineral matter within the boiler shell, and the deposit is called incrustation, sediment, or sludge according to its texture and its position. When water is heated under pressure and concentrated by evaporation as in a boiler, certain substances are thrown out of solution and solidify on the flues and crown sheets or within the tubes. These deposits increase fuel consumption because they are poor conductors of heat, and they also increase cost of boiler repair and attendance because they have to be removed.' If the amount of scale is great or if it is allowed to accumulate, the boiler capacity is decreased and disastrous explosions are likely to occur. Formation of scale is the most common boiler trouble, probably one-fifth of the steam generators in this country being found defective on that account. The scale of incrustation consists of the substances that are insoluble in the feed-water or become so within the boiler under conditions of ordinary operation. It includes practically all the suspended matter; the silica, probably precipitated as the oxide; the iron and aluminium, appearing in the scale as oxides or hy- drated oxides; the calcium, precipitated in the form of carbonate and sulphate; and the magnesium, found in the deposits prin- cipally as the oxide but partly as the carbonate. The scale con- stituted by these substances is, therefore, a mixture of compounds, which varies in amount, density, hardness, and composition with different conditions of water supply, steam pressure, type of boiler, and other circumstances. Calcium and magnesium are the prin- cipal basic substances in the scale, over 90 per cent of which usually is calcium, magnesium, carbonates, and sulphates. If much organic matter is present part of it is precipitated with the mineral scale, as the organic matter is decomposed by heat or by reaction with other substances. If magnesium and sulphates are comparatively low or if suspended matter is comparatively high, the scale is soft and bulky and may be in the form of sludge that can be blown or washed from the boiler. On the 32 ELEMENTS OF INDUSTRIAL CHEMISTRY other hand a clear water relatively high in magnesium and sul- phates may produce a hard, compact scale that is nearly as dense as porcelain, clings to the tubes, and offers great resistance to the transmission of heat. Therefore the value of a water for boiler use depends not only on the quantity of scale produced by it but also on the physical structure of the scale. CORROSION. Corrosion, or " pitting," is caused chiefly by the solvent action of acids on the iron of the boiler. Free acids capable of dissolving iron occur in some natural waters, especially in the drainage from coal mines, which usually contains free sulphuric acid, and also in some factory wastes draining into streams. Many ground waters contain free hydrogen sulphide, a gas that readily attacks boilers; and dissolved oxygen and free carbon dioxide also bring about corrosion. Organic matter is probably a source of acids, for it is well known that waters high in organic matter and low in calcium and magnesium are corrosive, though the exact nature and action of the organic bodies are not understood. Acids freed in the boiler by the deposition of iron, aluminium, and magnesium as hydrates that are later partly or completely converted into oxides are the chief cause of corrosive action, and magnesium is the most important of these as it is the most abundant. According to the chemical composition of the water the acid radicles that were in equilibrium with these beses may do one or all of three things: they may pass into equilibrium with other bases, displacing equivalent proportions of carbonates and bicarbonates, or they may decompose carbonates that have been precipitated as scale, or they may combine with the iron of the boiler, thus causing corrosion. The certainty of these reac- tions can be expressed, even with the most complete analyses, only as a probability. If acid thus freed exceeds the amount required to decompose the carbonate and bicarbonate radicles, the iron of the boiler is attacked, and pits or tuberculations of the interior surface, leaks, particularly around rivets, and con- sequent deterioration of the boiler result. FOAMING. Foaming is the formation of masses of bubbles on the surface of the water in the boiler and in the steam space above the water, and it is intimately connected with "priming," which is the passage from the boiler of steam mixed with water. Foaming results when anything prevents the free escape of steam from the water, and the principal cause of it is usually believed to be an excess of dissolved matter that increases the surface tension of the liquid and thereby reduces the readiness with which the WATEE, ITS USES AND PURIFICATION 33 steam bubbles break. Consequently, as sodium and potassium remain dissolved in the boiler water while the greater portion of the other bases is precipitated, the foaming tendency is commonly measured by the degree of concentration of the alkaline salts in solution, because this figure, in connection with the type of boiler, determines to a great extent the length of time that a boiler may run without danger of foaming. It is a fact that the worst foaming waters in railroad practice are encountered in arid and semiarid regions of the Southwest, where the quantity of dissolved alkali is greatest. However, it is well known that suspended matter can cause foaming, for certain surface waters that when clear do not foam, but deposit a moderate amount of scale foam badly whenever they carry a great quantity of mud. Greth states that the cause of foaming is among the following factors: the condition of the boiler, the design of the boiler, the size and shape of the water space, the steam pipe, irregular blowing off, introduction of oil into the feed water from the exhaust steam, neglect to change water periodically, irregularity of load, and improper firing and feeding. He concludes that it is not merely the presence of sodium salts in solution that causes foaming, but the presence of other substances which together with the sodium salts and operating conditions bring about foaming. A strong pure solution of sodium carbonate might not induce excessive foaming in a boiler, but suspended matter or precipitated sludge is invariably present under operating conditions, and the intro- duction of sodium carbonate would increase the suspended matter either by precipitating calcium and magnesium or by loosening previously deposited scale ; therefore, it is difficult under working conditions to distinguish between possible causes of the trouble. Experience has shown that the type of boiler, steam pressure, and other operating conditions accelerate or retard foaming to a great extent. Remedies for Boiler Troubles. The best remedy for troubles caused by substances in feed-waters is treatment of sup- plies before they enter boilers; this subject is considered under " Purification of Water." When such treatment cannot be given there are various ways of obviating trouble. Low-pressure, large- flue boilers are used in many stationary plants supplied with hard waters, and it is said that the scale formed in them is softer and more flocculent and can therefore be more readily removed than that in high-pressure boilers. Blowing off is about the only prac- tical means of preventing foaming, because this trouble is due 34 ELEMENTS OF INDUSTRIAL CHEMISTRY principally to concentration of soluble salts in the residual water of the boilers. Accumulated sludge, or soft scale, can be removed by blowing, particularly in locomotive practice. In condensing systems much of the trouble due to mineral matter in the feed- water is obviated because the quantity of raw water supplied is proportionately small. Yet the problem is not completely solved in such systems because the incrusting or corrosive action is trans- ferred from the boiler to the condenser, which requires more or less cleaning and repairing in proportion to the undesirable quali- ties of the water supply. BOILER COMPOUNDS. Boiler compounds are widely used in regions where hard waters abound, but treatment within the boiler should be given only when it is impossible to purify the supply before it enters the boiler or when a relatively pure supply requires only minor correction. If previous purification is not practicable some feed-waters can be improved by judicious addi- tion of chemicals. Many substances, ranging from flour, oatmeal, and sliced potatoes to barium and chromium salts, have been recommended for such use, but only a few have proved to be really efficient. These substances have been classified according to their action within the boiler. Those that attack chemically the scaling and corroding constituents precipitate incrusting matter and neutralize acids. Soda ash, the commercial form of sodium carbonate, containing about 95 per cent Na2COs, is the most valuable substance of this character, because it is cheap and its use is attended with the least objectionable results. Tannin and tannin compounds are also used for the same purpose. The addition of limewater to the feed-water to prevent corrosion and to obviate foaming has been recommended, and it is probable that lime used with waters high in organic matter and very low in incrustants would improve them. Such practice increases the incrustants in proportion to the lime added, but prevents injury of the boiler by corrosion. Soda ash neutralizes free acids, pre- cipitates the incrusting ingredients as a softer, more flocculent material, which is more easily removed, and increases the foaming tendency of the water by increasing its content of dissolved matter. The proper amount of it to be used depends on the chemical composition of the water and the style of boiler. The second class of boiler compounds comprises those that act mechan- ically on the precipitated crystals of scale-making matter soon after they are formed, surrounding them and robbing them of their cement-like action. Glutinous, starchy, and oily sub- WATER, ITS USES AND PURIFICATION 35 stances belong to this class, but they are not now used to any considerable extent, because they thicken and foul the water more than they prevent the formation of hard scale. The third class comprises those that act mechanically, like those of the second class, and also partly dissolve deposited scale, thus loosening it and aiding in its ready removal. Kerosene is very effective, but graphite is believed to be still better. Many boiler compounds possessing or supposed to possess one or more of the functions ju?t described are on the market and are widely sold. Some are effective and some are positively injurious. Most of them depend for their chief action on soda ash, petroleum, or a vegetable extract, but all are costly compared with lime and soda ash. It can be readily understood that boiler compounds cannot in any manner reduce the total amount of scale but may increase it. Their only legitimate functions are to prevent deposition of hard scale and to remove accumulations of scale that have become attached to the boiler. It should always be borne in mind that a steam boiler is an expensive piece of apparatus and that boiler repairs and fuel are also expen- sive. It is far more economical to have the water supply analyzed and to treat it effectively by certain well-known chemicals in proper proportion, either within or without the boiler, than to experiment with compounds of unknown composition. NUMERICAL STANDARDS. The committee on water service of the American Railway Engineering and Maintenance of Way Association have offered a classification of waters in their raw state that may be employed for approximate purposes, but, as their report states, "it is difficult to define by analysis sharply the line between good and bad water for steam-making purposes." Approximate Classification of Waters for Boiler Use Incrusting and corroding constituents.* Parts per million. Classifica- tion. More than Not more than 90 200 430 90 200 430 680 Good Fair Poor Bad Foaming constituents. f Parts per million. Classifica- tion. More than Not more than 150 250 400 150 250 400 Good Fair Bad Very bad "! i * Proc. Am. Rv. Eng. and Maintenance of Way Assoc, Vol. V, 1904, p. 595. t Idem, Vol. IX, 1908, p. 134. 36 ELEMENTS OF INDUSTRIAL CHEMISTRY The question how hard a water may be used without treat- ment can be decided by comparing the cost of artificially soften- ing the water with the saving effected by the use of softened water. The benefits include: Saving in boiler cleaning. Saving in boiler repairs. Saving in fuel due to decrease in scale. Increased number of boilers in service. Decreased depreciation of boilers. Value of materials removed by softening plant. The cost of softening includes: Labor for operating softener. Power for operating softener. Softening chemicals. Interest on cost of installation. Depreciation of softening plant. Waste in changing boiler water due to increased foaming tendency of the water. In general it is economical to treat waters containing 250 to 850 parts per million of incrustants, and those containing less than the lower amount if the scale contains much sulphates. As the incrusting solids may commonly be reduced to 80 or 90 parts per million, the economy of treating boiler waters deserves careful consideration in regions of hard water. The amount of mineral matter that makes a water unfit for boiler use depends on the combined effect in boilers of the soften- ing reagent used with such waters and of the constituents not removed by softening. Sodium salts added to remove incrust- ants or to prevent corrosion increase the foaming tendency, and this increase may be great enough to render a water useless for steaming purposes. It is not of much benefit to soften a water containing more than 850 parts per million of non-incrusting ma- terial and much incrusting sulphates. Trouble from foaming in locomotive boilers begins at a concentration of about 1700 parts per million of foaming constituents and a concentration of 7000 parts is about the limit of safety for stationary boilers. Though waters containing as high as 1700 parts per million of foaming constituents have been used, it is usually more economical to incur considerable expense in replacing such supplies by better ones. WATER, ITS USES AND PURIFICATION 37 Water for Industrial Use other than Boiler Pur- poses. The manufacture of many articles is affected by the ingredients of natural waters. The quality of water for boiler service has already been discussed; with reference to factories it need only be added that increase of boiler efficiency often justifies purification of poor water when increased value of the manufactured product alone may not be considered to do so. This observation applies particularly to paper, pulp and straw- board mills, laundries, and other establishments where large quantities of water are evaporated to furnish steam for drying, and to ice factories and similar plants where distilled water is produced. But besides its use for steam making, water plays a specific part in many manufacturing processes. In paper mills, strawboard mills, bleacheries, dyeworks, canning factories, pickle factories, creameries, slaughter houses, packing houses, nitroglycerin factories, distilleries, breweries, woolen mills, starch works, sugar works, tanneries, glue factories, soap fac- tories and chemical works water becomes a part of the product or is essential in its manufacture. As the principal function of water in most of these establishments is that of a cleansing agent or a vehicle for other substances, a supply free from color, odor, suspended matter, microscopic organisms, and especially bacteria of fecal origin, and fairly low in dissolved substances, especially iron, is generally satisfactory; but there are some exceptions. Water hygienically acceptable is necessary where it comes into contact with or forms part of food materials, as in the making of beverages, sugar, and dairy or meat products. As all these ideal conditions are encountered in few natural supplies, the manufacturer is confronted with the problems of ascertaining what degree of freedom from these substances is necessary to prevent injury to his machinery or to his output and whether the cost of obtaining such purity is counterbal- anced by decreased cost of production and increased value of product. Competitive business methods and increased facil- ities of transportation have standardized the values of manu- factured articles so thoroughly that makers are now obliged to scrutinize carefully every item of production costs in order to obtain reasonable profits. Therefore any appreciable saving effected by improvement of the water supply is one of the easiest sources of profit for the manufacturer. POTABLE WATER. Water that is used on food materials in any industrial operation should be potable; that is, should be pal- 38 ELEMENTS OF INDUSTRIAL CHEMISTRY atable, est helically unobjectionable, and absolutely free from anything that might cause disease. Increased public attention to the quality of foods and beverages makes this standard essen- tial and it is an extremely short-sighted manufacturer that dis- regards it. Because of this and because employees in many establishments use the mill supply for drinking, it is not out of place to note the requisites of water as a beverage. To be entirely acceptable in this respect water should be free from suspended matter, color, odor, and taste, and fairly cool. It should be free from disease-bearing germs and poisonous chemicals; and it should be low in dissolved mineral ingredients. The nearer a water approaches these conditions the more satis- factory it is for general use. PHYSICAL QUALITIES. Suspended mineral matter clogs pipes, valves and faucets, and growths of microscopic plants suspended in water frequently cause bad odors and stains in clothes. Color is usually due to dissolved vegetable matter and is a cause of serious objection in a domestic supply only when it exceeds 20 or 30 parts per million. Some waters, especially those containing iron, develop a turbidity of 10 to 30 parts per million on exposure to the air, due to precipitation of dissolved matter, and such condition gives rise to an apparent though not a real color. Odors may be caused by various conditions. One like that of rotten eggs is due to free hydrogen sulphide. Growths of microscopic organisms in tanks and water mains often have unpleasant odors that make the water objectionable. Per- fectly acceptable drinking supplies are free from color, odor, taste, and turbidity. BACTERIOLOGICAL QUALITIES. Before a water is used for domestic purposes there should be reasonable certainty that it is free from disease-bearing organisms. Yet present bacteriolog- ical technique does not permit positive statement regarding the presence or absence of such organisms, and it is advisable, there- fore, to guard supplies against all chances of infection. The disease germs most commonly cariied by water are those of ty- phoid fever. The bacilli enter the supply from some spot infected by the discharges of a person sick with this disease and though the germs are comparatively short-lived in water, they persist in fecal deposits and retain their power of infection for remark- able lengths of time. Consequently wells should be so located that their waters are guarded against the entrance of filth of any kind either over the top or by infiltration, and pumps and piping WATER, ITS USES AND PURIFICATION 39 in the S3 r stem should also be protected. Water from a carefully cased well over 20 or 30 feet deep is acceptable if the well is located after the exercise of reasonable judgment in regard to privies, cesspools, and other sources of pollution. Open dug wells and the pits constructed as reservoirs around the tops of many casings are exposed to fecal contamination from above or through cracks in poorly built sidewalls. Care should be taken that the casings of deep wells do not become leaky near the surface of the ground so as to allow pollution to enter. As a a matter of ordinary precaution the ground should be kept clean and water should not be allowed to become foul or stagnant near any well, no matter how deep it is. If shallow dug wells are necessary they should be constructed with water-tight casings extending down as far as practicable into the well and also a short distance above ground.- The floor, or curbing, should be water-tight, and pumps should be used in preference to buckets for raising the water. Every possible precaution should be taken to prevent feet scrapings and similar dirt from getting into the water by way of the top of the well. Underground water is not only less likely to become contaminated if protected from surface washings, air, and light, but it keeps better and is less likely to develop microscopic plants that give it an unpleasant taste. CHEMICAL QUALITIES. Amounts of dissolved substances permissible in a domestic supply depend much on their nature. No more than traces of barium, copper, zinc, or lead should be present because these substances are poisonous. The occur- rence of these elements in measurable amounts in ordinary waters is so rare that tests for them are not usually made. Any constit- uent present in sufficient amount to be clearly perceptible to the taste is objectionable. Water containing two parts per million of iron is unpalatable to many people, and even this small amount can cause trouble by discoloring washbowls and tubs and by producing rusty stains on clothes. Tea or coffee cannot be made satisfactorily with water containing much iron because a black, inky compound is formed. Four or five parts of hydrogen sul- phide are unpleasant to the taste, and this dissolved gas is objec- tionable also because it corrodes well strainers and other metal fittings. The amounts of silica and aluminium ordinarily present in well waters have no special significance in relation to domestic supply. Approximately 250 parts of chlorides make a water taste " salty," and less than that amount causes corrosion. 40 ELEMENTS OF INDUSTRIAL CHEMISTRY Calcium and magnesium are chiefly responsible for what is known as the hardness of water. This undesirable quality is indicated by increased soap consumption, as calcium and mag- nesium unite with soap, forming insoluble curdy compounds with no cleansing value and preventing the formation of a lather until these two basic radicles have been precipitated. The use of soda ash to " break " hard waters, or to precipitate the cal- cium and magnesium, is common and effects saving in the cost of soap. PURIFICATION OF WATER. Purification of water is prac- ticed on a large scale with one or more of three objects in view: first, to render the supply safe and unobjectionable for drinking purposes; second, to reduce the amount of the mineral ingre- dients injurious to boilers; third, to remove substances injurious to the machinery or to the manufactured product in industrial processes. The largest purification plants in this country have been constructed for the purpose of producing potable waters without special attention to other possible uses, and some waters need no further treatment before being suitable for steaming and for general industrial purposes. But many other waters are hard, and increased appreciation of the value of good water has resulted in demand for the removal of the hardening constit- uents also. Removal of bacteria, especially those causing disease, and removal of turbidity, odor, taste, and iron are the principal requirements in purification of a municipal supply, elimination of bacteria and suspended master being the most important. The common methods of effecting such purification are slow filtration through sand and rapid filtration after coagulation, both methods usually being combined with sedimentation. The first process is known as " slow sand " filtration and the second as " rapid sand " filtration. The efficiency of such filters is meas- ured primarily by the ratio between the number of bacteria in the applied water and the number in the effluent. This figure, stated in percentage of removal, should be as high as 98, and it often reaches 99.8 per cent with a carefully operated filter of either kind under normal conditions. Removal of scale-forming and neutralization of corrosive constituents are the chief aims in preparing water for steam mak- ing and three general methods are employed, namely, cold chem- ical precipitation followed by sedimentation, application of heat with or without chemicals, usually followed by rapid filtration, WATER, ITS USES AND PURIFICATION 41 and distillation. The first process is carried on in cold-water softening plants and the second in feed-water heaters. The most efficient distillation is effected in multiple-effect evapo- rators. Besides the four common systems of purification that have been cited, several minor processes are used, sometimes alone but more frequently as adjuncts to filters or softeners. Surface waters are screened through wooden or iron grids or through revolving wire screens to remove sticks and leaves before other treatment. Coarse suspended matter can be removed by rapid filtration through ground quartz or similar material in units of convenient size provided with arrangements for washing the filtering medium similar to those used in mechanical filters. Very turbid river waters are first allowed to stand in sedimenta- tion basins in order to reduce the cost of operating the filters by preliminary removal of part of the suspended soils. Supplies undesirable only because of their iron content are aerated by being sprayed into the air or by being allowed to trickle over rocks or by other methods that cause evaporation of carbonic acid and absorption of oxygen, thus precipitating and oxidizing the iron in solution so that it can readily be removed by rapid filtration. Similar aeration is often employed for the purpose of evaporating and oxidizing dissolved gases that cause objection- able tastes and odors. Disinfection by ozone, copper sulphate, calcium hypochlorite, and other substances kills organisms that may cause disease or impart bad odors and tastes. Purification of this character must be done with substances that destroy the objectionable organisms without making the water poisonous to animals. Calcium hypochlorite, sodium hypochlorite, and chlorine gas are used to disinfect drinking water, and treatment with these substances is now widely practiced either as an adjunct to filtra- tion or as an emergency precaution where otherwise untreated supplies are believed to be contaminated. Disinfection by this method is not a substitute for purification by filtration, for it does not remove suspended matter nor appreciable amounts of color, organic matter, swampy tastes or odors, and it does not soften water. Natural purification of water is accomplished largely through biological processes in which the organic matter is oxidized by serving as food for bacteria, and objectionable organisms are destroyed by the production of conditions unfavor- able to their existence. Action of this kind takes place in reser- 42 ELEMENTS OF INDUSTRIAL CHEMISTRY voirs and lakes, and it is also relied upon in many processes for the artificial purification of sewage. Slow Sand Filtration. Slow sand filtration consists in causing the water to pass downward through a layer of sand of such thickness and fineness that the requisite removal of sus- pended substances is accomplished. This filter is also called the continuous and the English filter. On the bottom of a water- tight basin commonly constructed of concrete, perforated tiles or pipes laid in the form of a grid are covered with a foot of gravel graded in size from 25 to 3 millimeters in diameter from bottom to top, and a layer of fine sand 3 to 4 ft. in depth is put over th& gravel, which serves only to support the sand. When water is applied on the surface it passes through the sand and the gravel, and flows away through the under-drain. The suspended solids, including bacteria, are removed by the sand, the action of which is rendered more efficient by the rapid formation of a mat of finely divided sediment on the surface. When this film has become so thick that filtration is unduly retarded, the water is allowed to subside below the surface and about half an inch of sand is removed, after which filtration is resumed. The sand thus taken off is washed to free it from the collected impurities, and it is replaced on the beds after they have been reduced by successive scrapings about a foot in thickness. As cleaning necessitates temporary withdrawal of filters from service they are divided into units of convenient size, usually half an acre each, so that the operation of the system may not be interrupted. Most modern filters are roofed and sodded, as this facilitates cleaning by preventing the formation of ice, permits work on the filter beds in all kinds of weather, inhibits algae growths, and prevents agitation of the water by wind and rain. RAPID SAND FILTRATION. The distinctive features of the rapid sand process are the coagulant and the high rate of filtra- tion. This type is also known as the American filter and it was formerly called the " mechanical " filter because of the con- trivances for washing the filtering medium. The raw water dur- ing its entrance into the sedimentation basin, which is smaller than that used with slow sand filters, is treated with a definite proportion of some coagulant, which forms by its decomposition a gelatinous precipitate that unites and incloses the suspended material, including the bacteria, and absorbs the organic color- ing mAter. This combined action destroys color and makes suspemted particles larger and therefore more readily removable. WATER, ITS TjSES AND PURIFICATION 43 Aluminium sulphate, the coagulant most commonly used, is decomposed, aluminium hydrate is precipitated, and the sulphate radicle remains in solution, replacing an equivalent amount of the carbonate, bicarbonate, or hydroxyl radicle. The natural alkalinity of many waters is sufficient to effect this reaction. According to Hazen one part per million of ordinary aluminium sulphate should be allowed about 0.6 part of alkalinity expressed as CaC03 to insure complete decomposition. If the alkalinity is not sufficient, part of the aluminium sulphate remains in solu- tion and good coagulation does not take place. Therefore lime or soda ash is added if the alkalinity is too low. The proper amount of aluminium sulphate to be used is determined by the amounts of color, organic matter, and suspended matter and by the fineness of the suspended matter, and is best ascertained by direct experimentation with the water to be purified. It may vary from 12 or 15 parts per million for water with 10 parts of sus- pended matter and a color of 30 to 25 or 30 parts for a water with a turbidity of 400 and a color of 80. Ferrous sulphate is used instead of aluminium sulphate as a coagulant in some plants; lime must be added with it in order to bring about proper coagu- lation. The water, after having been mixed with the coagulant, is allowed to stand three or four hours in the sedimentation basin, where a large proportion of the suspended pai tides is deposited. It is then passed rapidly through beds of sand or ground stone to remove the rest of the suspended matter. Sand with an effect- ive size somewhat greater than that customary for continuous filters is used. Many filters now in use are built of wood or iron in cylindrical form 10 to 20 ft. in diameter, and some are designed so that filtration can be hastened by pressure. The sand, 30 to 50 ins. deep, rests on a metallic floor containing perforations large enough to allow ready issue of the water but small enough to prevent passage of sand grains. When the filter has become clogged the flow of water is reversed, filtered water being forced upward through the sand to wash it and to remove the impurities, which pass over the top of the filter with the wasted water. A revolving rake with long prongs projecting downward into the sand mixes it during washing and prevents it from becoming graded into spots of coarse or fine particles. Fig. 26 is a dia- grammatic vertical section of a rapid sand filter with a mechanical agitator. When filtration is taking place raw water enters through pipe A into the cylindrical tank filled with sand B under which 44 ELEMENTS OF INDUSTRIAL CHEMISTRY d ^uv •J. Lk Fig. 26. are grids of collecting pipes with small nozzles C discharging through pipe D. When -nJ~| the sand is to be washed -^n pipe A is shut off and ~~ |j water is forced upward from pipe D into the sand while the agitator E with rake-like teeth F is re- volved by power. The dirty water is decanted over the gutter G and escapes through waste- pipe H. Cold Water Soften- ing. The principal ob- jects of water softening are to remove the substances that cause incrustation in boilers, particularly calcium and "^^n magnesium, and to neu- tralize those that cause corrosion. Chemicals of known strength properly dissolved in water are added to the raw supply in such proportion as to precipitate all the dis- solved constituents that can be economically re- moved by such treatment. The water is then allowed to stand long enough to permit the precipitate to settle, after which the clear effluent is drawn off, ' or the partly clarified efflu- ent may be filtered, very rapidly through thin beds of coke, sponge, excelsior, wool, or similar material, in order to remove parti- cles that have not subsided in the tanks. The water softeners on the market differ from Fig. 27. WATER, ITS USES AND PURIFICATION 45 each other chiefly in the precipitant, in the filtering medium if one is used, and in the mechanism regulating the incor- poration of the chemicals with the water. Installations may be of any size to suit consumption, and the process can be com- bined with mechanical filtration for purifying municipal water supplies, as in the municipal plant at New Orleans. Fig. 27 is a diagrammatic representation of a cold-water softener. The raw water passes by pipe A into box B, whence it falls over wheel C, generating power for operation. It then flows into the top of cone E after being mixed with the softening chemicals at D. The mixture settles in E and F and is filtered through excelsior G and finally flows out by pipe H. The chemicals are dissolved in tank /, and the solution is raised by pump J" to tank K, where it is kept mixed by agitator L. The float M raises or lowers pipe N, thus keeping the supply of chemicals proportional to the supply of raw water. The sludge is let out at 0. Among the substances that have been proposed as precipi- tant s are sodium carbonate, silicate, hydrate, fluoride, and phos- phate, barium carbonate, oxide, and hydrate 3 and calcium oxide, but of these substances lime and soda ash are almost exclusively used on account of their excellent action and comparative cheap- ness. When soda ash and lime dissolved in water to form solu- tions of known strength are added to a water in proper pro- portion, free acids are neutralized, free carbon dioxide is removed, the bicarbonate radicle is decomposed, and iron, aluminium, and magnesium hydrates and calcium carbonate are precipitated. The four basic substances are removed to the extent of the solu- bility of these compounds in water, and the calcium added as lime is also precipitated; in other words the scale-forming in- gredients are removed. PERMUTIT. There has recently been brought on the market a product known as " Permutit," which is an artificial zeolite having the formula Al2O3-10SiO2-10Na 2 O. The valuable prop- erty of this substance is to exchange its sodium for the bases calcium and magnesium, which it does when brought in contact with solutions containing these elements. Therefore if a hard water is passed through a bed of permutit, the sodium of the permutit is replaced by the calcium and magnesium of the water forming a calcium-magnesium permutit, while the acid radicles formerly united to the calcium and magnesium in the water unite with the sodium. It will be seen by this that the 46 ELEMENTS OF INDUSTRIAL CHEMISTRY hardness of the water is removed, although the amount of total solids will remain the same. When the sodium of the permutit has become exhausted by the replacement with magnesium and calcium it is treated with a salt solution which by mass action converts the exhausted permucit back to its original condition. This treatment can go on indefinitely. The method of handling is very simple in that all that is required is a number of tanks containing the per- mutit. The water runs through the bed thus formed and comes from the filter free from incrustatmg materials. FEED-WATER HEATING. Water heaters are designed pri- marily for the purpose of utilizing waste heat in stationary boiler plants by raising the temperature of the feed-water and thereby lessening the work of the boilers themselves, but they also effect some purification, and many heaters have been specially con- structed to take advantage of that effect. The heat is derived from exhaust steam or from flue gases, and the heaters utilizing steam are either open, that is, operated at atmospheric pressure, or closed and operated at or near boiler pressure. In accordance with these three conditions, which result in distinct purifying effects, feed-water heaters are classified as open or closed or economizers, the last being those using flue gases. In most open heaters, which are best adapted for removing large quantities of scale-forming material, the steam enters at the bottom and the water at the top, and intimate contact between the two is obtained by spraying the water or by allowing it to trickle over or to splash against plates. In this manner the water is quickly heated nearly to boiling temperature. Dissolved gases are expelled, the bicarbonate radicle is decomposed, and the iron, aluminium, part of the magnesium, and calcium equivalent to the carbonates after decomposition of the bicarbonates are precipitated as hydrates, oxides, and carbonates under varying conditions of temperature, pressure, and time. The precipitate agglomerates the particles of suspended matter and makes them more readily removable by sedimentation and filtration. The slowness with which the reactions take place and the presence of acid radicles other than carbonates to hold the bases in solution prevent com- plete removal of calcium and magnesium. The addition of soda ash in proper proportion, however, effects fairly complete precipita- tion of the alkaline earths, and apparatus for constant introduc- tion of this chemical in solution may be provided. After the precipitate has been formed the water passes through filters of WATER, ITS USES AND PURIFICATION 47 burlap, excelsior, straw, hay, wool, coke, or similar material arranged in units that can readily be cleaned. Open heaters operated without a chemical precipitant remove substances that are soft and bulky and leave in the water the constituents that form hard scale ; scale from water treated in such heaters is there- fore not so great in amount, but is harder than that formed by the raw water. The open feed-water heater and receiver utilizes the exhaust and brings it into intimate contact with the raw water, not only softening the latter, but also heating it for boiler use. In closed heaters the water is passed through metal tubes surrounded by steam at high pressure or around pipes in which steam circulates, and manholes or other openings are provided for cleaning the scale from the tubes. As the water is heated under pressure some precipitation takes place, but closed heaters are not so efficient in this respect as open heaters, because they do not permit escape of the gases liberated from the water. This objection does not hold if treatment in a closed heater follows treatment in an open one from which the gases escape, and several systems accomplish very good purification by using a unit of each type in series. Economizers consist essentially of water tubes set in the flues leading from the furnaces. Facilities are provided for cleaning scale from the inside and soot from the outside of the tubes. As economizers are heated by flue gases, the water in the tubes can be heated under pressure to a much higher temperature than in open or closed heaters, and the boiler conditions described in the section on water for steam making are approximated. The precipitation of incrustants varies greatly with the normally fluctuating temperature of the flue gases. DISTILLATION. The natural waters in some regions are so strongly mineralized or so badly polluted as to be unfit for general industrial use even after being filtered or softened, and water practically free from all dissolved and suspended matter is neces- sary for some industrial processes. Under such conditions the water must be distilled. This process is carried on in some factories by condensing steam from ordinary boilers, but if large quantities are required the installation of multiple-effect stills is advisable, for by their use the cost of producing pure water is greatly reduced. The principle of distillation is too well known to require detail; multiple-effect stills are so designed that by proper adjustment of steam pressures and temperatures, the heat 48 ELEMENTS OF INDUSTRIAL CHEMISTRY interchange between the purified and raw supplies is utilized to produce great efficiency. The best stills have attachments by which the noxious volatile substances and gases are eliminated. Distillation is the only commercial process by which supplies suitable for industrial use can be obtained from salt or strong alkali waters. CHAPTER III FUELS DEFINITION. A fuel is a substance whose combustion in atmospheric oxygen can be utilized as a source of heat energy for commercial or domestic purposes. They are most conveniently considered as* divided into three natural classes: solid, liquid, and gaseous. Elementary Constituents. The two elements which contribute most to the heating power of fuel are carbon and hydrogen. Though other elements, such as sulphur, contribute somewhat to the formation of heat, the two mentioned above are by far the most important. That portion of the oxygen which occurs in the fuel as a partial oxidation product of some compound constituent thereof causes a loss in the heating value, as its presence means that a certain amount of the oxidation and heat development have been accomplished outside the furnace. Sulphur in small amounts is usually found in fuels. In large amounts it is undesirable, as it has a corrosive action and renders the fuel unfit for metallurgical uses. Nitrogen is usually an inert constituent, escaping uncombined during combustion. Silicon and phosphorus are also found in fuels, the latter being undesirable in metallurgical work. Together with the last two there is usually a considerable amount of mineral matter which is left after combustion as ash, and usually a certain amount of water which occurs free in the fuel. Ash is undesirable, as it dilutes the combustible matter of the fuel, causes an additional expense for its removal, and may interfere seriously with the use of the fuel because of its low fusion point and the consequent tendency to form clinker. Water is a direct loss of heat, as it dilutes the fuel, requires a large amount of heat for its evaporation, and by escaping up the flue at the temperature of the escaping gases, carries away a certain amount of heat. Heat of Combustion. The heat of combustion of a substance is the number of calories produced by the complete oxidation of 1 gram of it. As applied to fuels, it is called the 49 50 ELEMENTS OF INDUSTRIAL CHEMISTRY calorific value or heating power of the fuel. The calorific value is one of the most important points to be decided in the purchase of a fuel. Having decided the character of fuel best adapted to the purpose for which the purchase is to be made, the remaining point of chief consideration is the calorific value, which is deter- mined by means of a calorimeter. Solids and non-volatile liquids are usually burned in a heavy steel bomb in an atmosphere of oxygen under a pressure of about 25 atmospheres. The cal- orimeter is immersed in water contained in a vessel protected by non-conducting material from temperature changes. The temperature of the water before and after the experiment, the amount of water and the water equivalent of the calorimeter being known, the total amount of heat liberated by the action is obtained. SOLID FUELS. Wood. Wood is composed principally of cellulose and ligno-cellulose in about equal quantities, together with gums, resins, a variable amount of water, and inorganic matter left as ash when the wood burns. Cellulose has the composition (CeHioOs)^ and is the principal constituent of the cell membranes of young plants. The formula above serves only to give the percentage of the constituents, the molecule being very complex. Ligno-cellulose is the substance with which the cellulose of young plants becomes incrusted as it grows old, and becomes woody fiber. It is not a carbohydrate, and little is known of its chemical nature. Wood. Wood has a low calorific value, varying from 3000 to 3500 calories, and contains a considerable amount of moisture, the amount depending on the kind of wood, the season in which it is cut, and the extent it has been allowed to dry, being rarely less than 18 per cent. Wood is of little value as a fuel, but it is sometimes used on account of its cleanliness and small amount of ash formed. Peat. There is no doubt that peat represents a comparatively early stage in the transformation which vegetable matter under- goes when sufficiently protected to prevent its complete oxida- tion, as in many localities it is possible to observe the transition from the vegetable matter covering the ground to the underlying peat in various stages of formation. In the upper portions the vegetable matter is easily discernible, while at the bottom, most, if not all, visible signs of plant remains disappear. The forma- tion of peat occurs in bogs or swamps where sufficient vegetable FUELS 51 matter accumulates to give rise to the formation. The deposit from each year's growth, such as mosses, grasses, leaves, branches and trunks of trees fall and are partially protected by the water from complete decomposition. The action of organisms and atmospheric oxygen transforms this material first into a loose brown substance, finally, with the aid of pressure from above, into a brown or black peat. Little is known of the chemical compounds composing peat. Some solvents and solutions of alkalies dissolve considerable amounts of organic matter of a complex character from peat, but the substances obtained from these solutions are probably impure. Peat has long been used as a fuel, and in northern and western Europe, and in Ireland (where peat bogs are said to cover one- tenth of the total area) it has been extensively used. Peat bogs are also widely distributed in this country and in Canada. The recent peats are usually brown in color and approach wood in chemical composition, containing less oxygen and hydro- gen and more carbon. The oldest peats are usually dark in color, and the percentage of carbon is greater than in recently formed peats. Peat has a higher calorific value than wood, varying from 3500 to 5000 calories. As it is cut from the ground it contains a large amount of water, often as much as 90 per cent of its weight. If the blocks are left to dry under cover in the air this is greatly reduced. The difficulty of freeing it from this water is one of the drawbacks to its use. By application of pressure much of it can be expelled, but it still contains a considerable amount on account of its jelly-like character. A recent observation that this jelly-like character is destroyed by heating it to 150° C, after which the water can be expelled by pressure, may assist in the solution of this difficulty. Peat is frequently formed into briquettes, when it makes an excellent fuel for domestic uses, as it burns with a bright cheerful flame and without much smoke. Lignite. Lignite and brown coal are names applied to the sub- stances which represent the next stage to peat in the transforma- tion of vegetable matter into coal. The distinction of lignite from peat on the one side and bituminous coal on the other is not sharp, as the transition from one to the other is gradual. Chemically, lignite seems to be more closely related to peat than to bituminous coal and, as with peat, it is found that certain 52 ELEMENTS OF INDUSTRIAL CHEMISTRY solvents and solutions of alkalies dissolve considerable organic matter of a complex character from lignites. The evidences of vegetable origin are not usually distinct in lignites, though when properly treated, microscopic examination is usually able to show the remains of plant structure. In general, lignite is denser, darker in color, and contains more carbon than peat. It contains about 35 per cent of water, and on air-drying this falls to about 15 per cent. Its calorific value varies from 4000 to 6500 calories. The amount of ash varies greatly, but should not exceed 10 to 15 per cent. On account of the difficulties encountered in shipping and storing lignite, its formation into briquettes has been practiced to a considerable extent, especially in Germany. In this country the necessity for using such fuels has not been greatly felt, and the operation of briquetting such fuel is here in its beginning. This question will be mentioned later in connection with bitumi- nous coal. Bituminous Coal. The next stage in the formation of coal is represented by bituminous coal, by far the most important of all the classes of fuels. The division of bituminous coals from lignites is more sharply defined than that of lignites from peats, but still the transition is gradual. The origin of coal is swamp flora laid down when the growth of vegetable matter was far more luxuriant than now, and which in earlier geologic ages has passed through successive stages which are represented now by peat bogs and beds of lignite. The properties of bituminous coals differ widely. The amount of volatile matter varies from 15 to 50 per cent, the amount of ash from 2 to 20 per cent, but the most marked differ- ences are observed in the coal substance when heated. The dif- ferences are noticed in the characters of both the volatile matter and the residue or coke. Some, when heated, fuse together to a compact mass, and if heated sufficiently leave behind a firm, solid mass composed principally of carbon and the ash of the coal. Such coals are said to be coking coals. Non-coking coals do not fuse and the mass left behind when such coals are heated coheres only slightly or not at all. Coals are frequently changed, after mining, by the absorption of oxygen and the loss of some of their combustible constituents, and on long standing their heating power is materially changed, some even losing their coking power. Frequently, this absorp- tion of oxygen is so rapid and accompanied with the evolution FUELS 53 of so much heat that when large amounts are stored in one pile the temperature gradually rises until spontaneous combustion ensues. To overcome some of these difficulties and to utilize those portions of the fuel which unavoidably go to waste around the mine, finely divided coal is frequently mixed with pitch or tar, and compressed while hot into molds. These briquettes are less bulky, less likely to deteriorate and to undergo spontaneous combustion, and can be fired more efficiently than the raw coal. Where it is necessary to keep large stores of coal on hand, these advantages are sufficient to justify the operation of briquetting. The practice of briquetting coal and lignite is more common in Germany than in this country. One of the chief objections to the burning of bituminous coals is the production of smoke during combustion. It is doubtful if this can be prevented by any means which involves the introduction of fresh coal directly into the fire. Mechanical stokers are designed to bring the fuel into the fire slowly, and at a regular rate. In this way the volatile matter is expelled gradu- ally and mixed with sufficient oxygen for its combustion, the result being that less smoke is produced, the fire kept in a more uniform condition than is possible by hand firing, and at the same time the fuel is consumed more efficiently. Anthracite. In composition the anthracite coals approx- imate the final stage in the carbonization of vegetable matter. On one side of the anthracite we have bituminous coals separated by the semi-anthracites, and on the other side the anthracites approach graphite. As indicated above, anthracites contain a large amount of fixed carbon as compared with their content of volatile matter. They are denser than bituminous coals, have a cnnchoidal fracture, and a high kindling temperature. Anthracite is used largely for metallurgical work, for the manu- facture of producer and water gases, and for domestic purposes, As it has little volatile matter, and burns with a non-luminous flame, it is well adapted to these purposes. Charcoal. Charcoal is made from wood by two methods. By the first, wood is converted into charcoal by what is called the charring process. This consists of piling the wood into large circular heaps, leaving horizontal flues near the bottom and a vertical flue at the center for the escape of the evolved gases and covering over the whole, except for these points of ventilation, with powdered charcoal, earth and turf. At the points of ventila- 54 ELEMENTS OF INDUSTRIAL CHEMISTRY tion the wood burns, the area of the combustion depending on the drafts, and the heat produced by the burning at these points suffices to raise the temperature of the whole mass to the point where most of the volatile matter of the wood is expelled. When all the volatile matter has been driven off and the escaping gases cease to burn with a luminous flame, the draft holes are covered and the operation stopped. By this process air-dried wood yields about 25 per cent of charcoal, but all the volatile matter is lost. By the second method of preparing charcoal provision is made for the recovery of these by-products, which consist of combus- tible gases, wood alcohol, organic acids, acetone and tar. The operation consists in the destructive distillation of wood from closed vessels, the charcoal remaining in the retort. For the production of charcoal for certain purposes these retorts are heated by means of superheated steam. Charcoal is quite porous and brittle and retains the shape of the wood, though the pieces are only about three-fourths the size of that of the wood. It still contains traces of volatile matter from which it is impossible to free it, and the ash-forming con- stituents of the wood. It burns with little flame, contains little sulphur and phosphorus, a low amount of ash, and has been ex- tensively used in metallurgical work, especially for the produc- tion of the finer grades of iron and steel. Its calorific value is about 7000 calories. The porosity depends on the character of the wood used in preparing it, some giving a denser product than others. It possesses the peculiar property of condensing many gases before they reach their point of liquefaction, and of abstracting coloring matter from solutions. This power of absorbing materials is frequently utilized to purify solutions from tarry materials and coloring matter. Because of the great ten- dency of charcoal to hold back small amounts of other substances perfectly pure amorphous carbon is unknown. Coke. Coke is the residue left after the destructive dis- tillation of coal, and is composed principally of carbon and the ash-forming constituents of the coal from which it was formed. The production of coke was at first carried out in much the same way that charcoal is obtained from wood in charcoal kilns; the bee-hive oven of to-day, in which a large amount of the coke produced in this country is made, is a development of this method. Fig. 28 illustrates the bee-hive oven as used in this country. It is simply a dome-shaped enclosure built of firebrick, 12 ft. in FUELS 55 diameter, 7 ft. high, with an opening at the top for charging and for the escape of the products of combustion and volatile matter formed during the operation, and a door at the side through which the coke is withdrawn, usually by hand, at the end of the operation. This door is built up with firebricks during the process, except at its top above the level of the charge. In this way five or six tons of coal are coked at each charge, and the time required is from forty-eight to seventy-two hours, yielding from 60 to 65 per cent of coke. The operation is brought to an end by quenching the fire in the oven with a stream of water, after which the coke is withdrawn. These ovens are usually Fig. 28. built together in one or two rows, with a track on top to bring up the coal. As seen from the above description, the burning of a part of the coal furnishes the heat necessary for coking the remainder, and the volatile matter of the coal is either burned or turned into the air. Numerous forms of ovens have been designed to collect these products and use them. These so-called by-products consist of combustible gases, various organic compounds, compounds of nitrogen, including ammonia and tar. Figs. 29, 30, 31 and 32 are illustrations of three types of by- product coke ovens which are used considerably in this country and will serve to illustrate the operation. 56 ELEMENTS OF INDUSTRIAL CHEMISTRY SECTION THROUGH REGENERATOR ELEVATION TRANSVERSE SECTIONS' Fig. 29. FUELS 57 The Otto-Hoffmann type of oven is shown in transverse and longitudinal sections in Figs. 29 and 30. The coal is charged through d into the coking chambers D beneath. These are long, narrow retorts of firebrick construction placed side by side, usually in groups of fifty. In the walls separating the retorts are the vertical flues/, in which the gas evolved in coking previous charges is returned from the condensing house and burned to furnish the heat for coking the charge. The retorts are about 33 ft. long, 6| ft. high, and 20 ins. wide, closed at each end by an iron door which is raised and lowered electrically, and during the coking process luted with fireclay. The air for the com- bustion of the gas passes through the checker work R, made of Fig. 31. refractory material, which, as we will see, is highly heated, the gas entering at the burner B. The burning gases pass along the horizontal flue Fi, and up each of the vertical flues / of one- half of the retort wall to the upper horizontal flue F 1 , then down the remaining vertical flues / of the second half of the wall to a similar horizontal flue F 2 , situated beneath the coking chamber D, then out through the second chamber or regener- ator R' filled with refractory checker work, where the heat of the escaping gases is abstracted by heating up the checker work to incandescence. After a certain length of time, when Z^'has been heated and R cooled, the currents of air and gas are reversed through the flues, the air entering through R' and the gas through another burner at the other end of the retort. The volatile 58 ELEMENTS OF INDUSTRIAL CHEMISTRY products escape from D through the uptake pipes, provided with valves, and pass into the common main G at a high temperature, and are gradually cooled in the iron pipes, depositing some of the condensable portions, the remainder being subsequently removed in the condensing house. After the completion of the coking process, the charge is removed by a steam or electrically operated pusher, which pushes Fig. 32. the whole charge of the retort out on the opposite side, where it is rapidly cooled by a stream of water. The time required for coking a charge in this type of oven is about twenty-four hours, yielding about 70 per cent of coke. In the Semet-Solvay type of by-product oven, shown in Fig. 31, the coking chamber D is somewhat similar to that of the Otto- Hoffmann oven above. They are built in sets of thirty or forty, are 35 ft. long, 1\ ft. high and 16J ins. wide. The coal is charged through d into the coking chamber D, the volatile products escaping through g into the common main G. The flues /, built in the walls of the ovens, are in this type five in FUELS 59 number and arranged horizontally. The gas returned from the condensing house is delivered at the four burners B, and mixes with preheated air delivered from beneath the oven. The current of burning gases is from the top flue downward through each of the others, fresh gas burning at each of the burners during their downward course. The gases from the flues in each wall of the chamber pass into a single flue beneath D, thence into a series of channels with thin walls where the air passing to the burners is preheated, as stated above. The flue gases are subsequently passed through water-tube boilers, and their remaining heat used to generate steam for power purposes. A charge of from 7 to 9 tons of coal can be coked in these ovens in about twenty-four hours. Fig. 32 shows a Kopper Coke Oven. In this type the chambers are heated by one generator, the gases passing along vertical flues. The chambers are 14 ft. long, 8 ft. high and 18J ft. wide. The chambers aie charged from the top of the larry with about four tons of coal at a time, the coke being pushed out by means of a ram. For each set of chambers a separate hydraulic main is provided. Coke is also obtained as a by-product in the manufacture cf coal gas, which will be mentioned later. But the coke obtained in this way is soft and unfit for metallurgical purposes, and is partly consumed in the producer used to heat the retorts, and for domestic purposes. During the coking process the coal fuses and the escape of the gases formed by the destructive distillation of the coal leaves the residue or coke full of cavities, the walls of which are quite hard. This cellular structure is very advantageous, as the coke to be of service for metallurgical work must be sufficiently strong to sustain the charge above without crushing, and at the same time must be porous. It has a silvery white luster, a metallic ring when struck and is infusible. It burns without smoke and has a calo- rific value of 7600 to 8100 calories. All of the ash of the coal and ordinarily about half of the sulphur remain in the coke, and it is frequently necessary to wash the coal to remove portions of these constituents in order to make a serviceable qualit}' of coke. The phosphorus of the coal is all found in the coke. Besides these, there is a considerable amount of nitrogen and water, and small amounts of hydrogen and oxygen which cannot be driven off by heat. Some coals which do not yield a good quality of coke can be mixed to advantage with a good coking coal. 60 ELEMENTS OF INDUSTRIAL CHEMISTRY The chief use of coke is for metallurgical purposes, but a great deal is used in gas producers, on railroad engines and for domestic purposes. The objection to the use of coke made in by-product ovens seems to have been without foundation, and the relative amount of coke made in the by-product ovens has increased steadily and rapidly. It seems that in a short time most of the coke made in this country will be made in this way, the increase being lim- ited only by the demand for the by-products. LIQUID FUELS. The only liquid substances which have any extended use as fuels are crude petroleum and various products obtained by its fractional distillation; as petroleum spirit, lamp oil, and the residue or " residuum " left in the retort after the distillation of the lubricating oils. Tars obtained as by-products in other industries are sometimes burned as fuels when a more remunerative market is not available, but they are too expensive for this purpose. The objection of expensiveness applies also to alcohol at present, but as it possesses certain advantages as a fuel, and its production is subject to our control, it is possible that it may assume more importance in the future if it can be pro- duced more cheaply. Petroleum. Petroleum is widely distributed, but 86 per cent of the world's output comes from this country and Russia; the United States producing 63 per cent and Russia 23 per cent of the total. In this country the Pennsylvania fields have been most prominent, and it was here that oil was first obtained by systematic borings. Besides Pennsylvania, many other States have become oil-producing. In using crude petroleum as a fuel the greatest objection is that the volatile portions will escape and mix with air and form an explosive mixture, as it requires only small amounts to form an explosive mixture with air. But it is only necessary to remove these by distillation to avoid such danger. In burning crude oil in 'furnaces it is first converted into a very fine spray by means of special burners, and the spray directed against refractory material, which, becoming incandescent, trans- mits much heat to the boiler by radiation, and it also effects better combustion. These burners are operated in two ways. In the first, the oil is " atomized " by forcing it under pressure through burners so constructed as to send the oil into the furnace in a sheet of finest spray. By the second the same disintegration of the oil is accomplished by a jet of steam. The objection to the FUELS 61 second method is that a large amount of steam is consumed, and the flame is cooled down at the point where the combustion should be most rapid, and, while the steam is effective in securing the combustion of the last portions and preventing the formation of smoke, it can be best introduced later in the flame and in smaller amounts. Several advantages are obtained by using petroleum as a fuel. It has a high calorific value, from 10,000 to 10,500 calories, is more uniform than coal, is easily regulated to secure complete combustion, and the rate of combustion can be changed by merely turning the valve admitting the fuel. It does not deteriorate if kept in covered tanks, and no spontaneous combustion occurs. It requires a small fraction of the number of stokers required to burn coal, gives no ashes, cinders or smoke when properly burned, and is easily transferred at sea through flexible hose by pumps. Still the output is so small when the total amount of fuel consumed is considered, and the supply so uncertain, that it seems that petroleum as a fuel must remain an adjunct except near the sources of supply and for certain special purposes such as on fast ocean-going ships, for use in navies, and to assist in meeting sudden demands on power-houses of a temporary character. GASEOUS FUELS. When the products of combustion of solid fuel are allowed to pass through a bed of incandescent carbon they are partially reduced, and can be ignited on their escape. The pale blue flame often seen burning at the top of an open grate fire is an illustration. And if the fuel bed were sufficiently thick and hot enough to reduce most of the carbon dioxide and water formed at the bottom of the grate, and provision made for collecting the gas, we should have a sample of producer gas. Producer gas is, then, the combustible gas obtained by the burning of solid fuel with a restricted supply of air, or with air and steam together in such a way that there is subsequent reduc- tion of the products of combustion and the steam by incandescent carbon. When air alone is used, the gas is called " air gas. 7 ' When steam is blown in along with the air the gas obtained is called " semi-water gas." By the action of steam alone on heated carbon the product is " water gas." Producer gas has the lowest calorific value of any gaseous fuel, and the temperature of its flame is the lowest of any, yet it is the cheapest artificial gas per unit of heat. It has become of great commercial advantage, as nearly any kind of solid fuel can be converted into a gaseous fuel in the producer. Although about 62 ELEMENTS OF INDUSTRIAL CHEMISTRY 20 per cent of the total heat of combustion of the fuel is lost in the producer, the remainder can be used so efficiently that the loss is more than retrieved. Its use in connection with the gas engine is an efficient means of power generation. With care it can be burned with a small excess of air, and complete combustion secured, causing a smaller amount of heat to be carried away by the escaping gases. It is finding application in commercial work of many kinds where a gas of high calorific value is not required. Siemens' Regenerative Furnace. The method used in con- nection with the Otto-Hoffmann oven above, for recovering the heat from the flue gases is known as the regenerative system. Fig. 33. Fig. 33 is an illustration of this type of furnace, which was first worked out by Siemens in connection with his gas producer, and known as the Siemens " regenerative " furnace. Beneath the furnace proper, A, are four chambers, B, C, D, and E, filled loosely with firebrick. The gas and air enter through B and C, and after burning pass out through D and E. After the interior of D and E is highly heated the direction of the gases is reversed, the gas and air entering through D and E, where they are highly heated before burning, and escape through A and B. Various methods have been worked out for the recovery of the heat con- tained in the gases which escape hot after the completion of an operation. This is illustrated in the Otto-Hoffman and Semet- Solvay coke ovens above, and in connection with gas producers FUELS 63 it is a matter of considerable importance to use as much as possi- ble of the heat of the escaping gases to preheat the air and steam introduced into the producer. Water Gas. Steam is usually forced into the gas producer along with air to overcome practical difficulties encountered in operating the producer with air alone, and at the same time to increase the calorific value of the gas. As the action of steam on carbon is accompanied with an absorption of heat, it is necessary to supply heat to continue the operation. The production of " semi-water gas " is made a continuous operation by the heat generated by the action of the oxygen of the air on the fuel in the producer. By separating the two operations taking place in the formation of " semi-water gas," and collecting the result- ing gases separately, we would obtain " air gas " and " water gas." The intermittent operation of the producer with air and steam is the usual method of preparing water gas. The producer is operated a few minutes with air until the temperature is suffi- ciently high, when steam is passed in until the temperature falls too low to produce a gas of high calorific value. The action of steam on highly heated carbon results in the formation of carbon dioxide, hydrogen, and carbon monoxide in proportions varying with conditions. It is customary to express the action by the following two equations: (1) 2H 2 0+C = CO2+2H2 - 18,340. (2) H 2 0+C = CO+H 2 - 28,650. At low temperatures the reaction is mostly according to Eq. (1) while at more elevated temperatures, according to Eq. (2). As the gases formed by these two reactions are capable of reacting according to Eq. (3) CO 2 +2H^CO+H 2 O-9310, and since equilibrium is obtained more readily between gases than between a solid and a gas, the composition of the water gas will tend to approach the condition of equilibrium according to this equation. The producer used to generate water gas does not differ greatly from the ordinary gas producer. The first successful water-gas plant was worked out by Lowe in 1874. Coal Gas. Coal gas is made by the destructive distillation of coal in fireclay retorts of special construction. They are mounted above a gas producer which furnishes the gas with which the retorts are heated. Above is a fireclay arch. Each retort 64 ELEMENTS OF INDUSTRIAL CHEMISTRY effects the distillation of a charge of about 400 lbs. in four hours. The gas escapes through a cast-iron mouthpiece which closes the open end of the retort and into a common main, where the opening of each tube is water sealed to prevent back pressure when the retort is opened. The composition of the gas varies with the kind of coal used and the conditions during distillation. These cause greater change in the illuminating power than in the calorific value. It burns with a bright, often sooty flame, and as it is composed almost entirely of combustible gases it has a high calorific value. The coke left in the retort is of inferior quality because of the method used to effect distillation and the character of the coal necessary to form a good quality of gas. It is used principally for illuminating purposes, and on ac- count of its high calorific value, it is used to some extent where a great deal of fuel is not needed. Oil Gas. Oil gas is made by the destructive distillation of petroleums. It is somewhat similar to coal gas, and contains a considerable amount of unsaturated hydrocarbons which im- part luminosity to the flame. Natural Gas. Natural gas occurs ready formed in the earth, and in the oil regions of Pennsylvania and Russia it is found in enormous quantities. It always accompanies petroleum, and their origins are closely connected. It is frequently confined under great pressure, and when borings are made through the overlying strata its escape is at times beyond control. While it always accompanies petroleum, it is sometimes found alone. As it is composed almost entirely of combustible gases, its calorific value is very high. The natural gas of this country burns with a slightly luminous flame, and has a higher kindling point than other gaseous fuels. When it is properly burned it is an excellent fuel, because of its high calorific value and prac- tically smokeless flame, CHAPTER IV SULPHURIC ACID PROPERTIES. Concentrated sulphuric acid is a heavy, oily liquid, which is colorless and odorless when pure. Its density is about 1.9, boils at 290° C. and freezes at about 10° C. The strong acid has a very powerful dehydrating action, break- ing down the skin and many other organic substances by robbing them of their water, in some cases even carbonizing or blacken- ing them. Burns produced by sulphuric acid are best treated by the instant application of large quantities of water, followed by the application of a solution of sodium bicarbonate and then dressing the w r ound with an emulsion of limewater and lin- seed oil. Impure acid attacks practically all metals, including platinum. Acid stronger than 65 per cent has no action on iron, while that less than 65 per cent has no action on lead. OCCURRENCE. Sulphuric acid is found in commerce as: Chamber acid (about 53° Be., 66.6 per cent H2SO4) taken from the bottom of the chambers in the chamber process; Glover acid (about 60° Be., 77.7 per cent) taken from the first or Glover tower of the chamber process; 66 acid is fairly pure acid con- centrated to 66° Be., 93.2 per cent; 98 acid, of 98 per cent, made by concentration or by the contact process and generally of great purity; oleum or fuming acid (100 per cent H2SO4 con- taining additional SO3 in solution), made by distillation of sul- phates (obsolete) or by the contact process: Nordhausen acid (oleum when made from distillation of weathered shales [obso- lete], containing iron sulphate or from FeSCk), approximating a composition H2SO4SO3 or H2S2O7, which is pyrosulphuric acid; and oil of vitriol, also called o.v. (generally about 66°). The old name, " oil of vitriol," is derived from its first preparation by the alchemists Gaber, Valentine and their predecessors, who made it by distillation of sulphates, particularly green vitriol, FeS04, or by the burning of sulphur after the addition of salt- peter. In fact, historically, sulphuric acid is one of the first isolated acids, known to the Arabians in the eighth century and 65 66 ELEMENTS OF INDUSTRIAL CHEMISTRY to Europe in the fourteenth and fifteenth centuries, when chemi- cal industries really began to develop. RAW MATERIALS. The three principal sources of sulphuric acid are: native sulphur, sulphide ores, and waste gases from metallurgical and technical operations. The chief supply of sul- phur in this country is from the Louisiana beds. This is an under- ground deposit which is being successfully worked by the Frasch process. Iron pyrites, often carrying more or less copper sulphide, is, at present, the largest source of sulphur for acid making. The chief supply of pyrites comes from Spain, although a limited quantity is obtained from other countries and a small amount from Canada and the United States. The third source of supply is from the " fumes " from the sulphide smelters. These gases were formerly allowed to go to waste, but are now being util- ized to some extent. OUTLINE OF PROCESS. Before describing the various operations involved in the manufacture of sulphuric acid it may be well to give a brief outline of the general process, later return- ing to consider the various steps more in detail. Thus, starting with the ore, it is crushed to get it to a uniform size con- venient for handling. The ore, or sulphur if that is used, is burnt in the appropriate form of furnace. By the combination of the sulphur with the oxygen of the air, the gas sulphur dioxide is produced. Regardless of the form of furnace, or the nature of the raw material, the hot sulphur dioxide immediately passes over the niter pots, where it is brought into contact with vapors of nitric acid. This nitric acid is formed by treating sodium nitrate with sulphuric acid, and is for the purpose of keeping up the supply of nitric oxides, which in their turn act as oxidizers for the SO2 by converting it to SO3. As the sulphur dioxide, now mixed with nitric acid, leaves the niter pots, it passes through a dust chamber, where it comes in contact with baffle plates, thus causing the dust to be deposited. The dust-free gases next pass into the bottom of the Glover tower and work their way up through a bed of porous material over which is flowing a mixture of dilute sulphuric acid and nitrosvl-sulphuric acid from the Gay-Lussac tower. The nitrosyl acid, being decomposed by the dilute chamber acid, gives off nitrogen oxides which tend also to oxidize the SO2 to SO3. The SO3 thus formed combines with the dilute sulphuric acid, thereby converting it into strong acid. The strong acid from the bottom of the Glover tower is in part used over in the Gay-Lussac tower, the remainder going to storage tanks. The gases from the top SULPHURIC ACID 67 of the Glover tower pass into the first lead chamber, where they meet with water in the form of steam or spray and with a supply of oxygen. Most of the remaining SO2 is converted into SO3 in the first chamber, which on account of the presence of moisture at once forms sulphuric acid. The color of the fume in the first chamber is of a heavy white character, due to the formation of the sulphuric acid. The gases pass from the first to the second and then to the third chamber. In so passing the content of sul- phur oxides becomes less and less, while the content of oxides of nitrogen becomes more concentrated. The oxides of nitrogen having accomplished their purpose are now recovered by passing into the Gay-Lussac tower, where they are absorbed by means of concentrated sulphuric acid. The nitrosjl-sulphuric acid, (NCfeHOSC^), produced in the Gay-Lussac tower is pumped to the top of the Glover tower, where it is decomposed by the weak chamber acid, and the oxides of nitrogen again returned to the system. The acid formed in the chambers goes by gravity to the storage tanks, from which it is pumped to the evaporating pans for concentration. Having taken a hasty glance of the general method employed in making sulphuric acid, let us now take up the steps more in detail so as to get a better understanding of the process as a whole. SULPHUR BURNING. In burning sulphur three points chiefly have to be considered: i.e., freedom of the gases from vol- atilized sulphur which has not been oxidized, sufficient richness of the gases for profitable operation of the sulphuric- acid -making portions of the plant, and as complete removal as possible of sulphur from the slight residue of mineral matter. Provision must be made for maintaining a sufficiently high temperature of the surrounding walls and of the material on which the sul- phur is supported. For the latter purpose an iron plate is generally used — Cast iron preferred — and it should be heavy enough and hot enough to insure active combustion of the sulphur at all points, even where the collected mineral residue is practically all that is left and only a small percentage of sulphur is being burned out of it. For this purpose special ovens are constructed. The necessity for accurate draft regu- lation is apparent. Too much draft is better than too little if ample provision has been made for the complete interaction of the gases before they are allowed to cool. In some types of 68 ELEMENTS OF INDUSTRIAL CHEMISTRY burners, in which the gases are drawn away too quickly from the burning pan, an excessive supply of air serves to chill the vapors and promote the deposition of sulphur in the flues. Fig. 34 illustrates one type of furnace recommended. The burner consists essentially of a shell of brickwork having an upper and lower chamber, the division between the two acting as a reverberatory over the pan A, in which the sulphur is burned. Draft is regulated at the door E. The fire cooled when neces- Fig. 34. is sary to retard the vapo- rization of the sulphur by means of admitting the air to space B be- neath the plate. Prod- ucts of combustion pass up through the hole C into the upper chamber D, where opportunity is given for the inter- action of sulphur vapor with the excess of air. A division wall in this upper chamber insures longer passage of the gases before cooling. A small hole above the inlet opening C into this upper chamber admits more air if necessary for the complete combustion of the sulphui vapor. Iron supports are provided for a niter pot when it is preferred to furnish niter for the chambers in this manner. This is one of the intermittent type of burners, generally operated in batteries. The exact regulation of draft is very difficult, and extreme care in periodic rotation of charges is essential to successful operation. BURNING OF PYRITES, Like coal, pyrites ore was not rec- ognized as a combustible' until early in the last century, various claims dating from 1793 to 1820. The first step in the burning of pyrites is properly to adapt the size of the ore to the character of burner being used. Although ore may be purchased on contract relatively free of fines or small ore, it is generally desirable to render the plant as independent as possible of market conditions. If run of mine ore is pur- chased, lumps may exceed 12 or 14 ins. diameter and a heavy breaker of the general Blake pattern, illustrated in Fig. 2, should SULPHURIC ACID 69 be provided and located preferably below the ground level. Feeding should be done from an iron-sheathed plank or cement floor. If lump ore is to be burned the product of the breaker should be elevated to a rotary screen of punched metal plates | to | in. in thickness the holes in which are f in. in diameter. The amount of fines made will be dependent upon the diameter of these holes, the character of the ore and the speed of the crusher. From the rotary screen, or riddle, the fines should be allowed to fall into a small hopper, and the lumps into a larger one. If all ore is to be burned as fines there should be placed, preferably below the breaker, one, or better, two sets of rolls illustrated in Fig. 4, and the breaker should be set some- what closer. * The breaker may then be expected to reduce the ore to about 1J to 2 ins., the first rolls to 1 in. and the second rolls from 1 to | in. or less. For the delivery of fines ore to fines burners Fig. 35. a belt conveyor is well adapted, and link-belt carrier conveyor with tripper has been used. Lump Burners. The lump burner is the simplest form of deep-bed coal fireplace. The charges required are weighed out with moderate accuracy and placed before each burner, each furnace being furnished with a regular size of lump. Fig. 35 shows a good type of burner, in which the common flue is provided with a double arch top. All doors are either hinged or their faces inclined, carefully planed, and therefore swing by gravity or latch against the planed edges cf the door jamb, allowing little leakage. The ash pit door D is perforated with 7 or more 1-in. holes, which can be plugged to regulate the admission of air below the grates. The doors E admit the shaker to the grate bars and also permit, to some extent, barring near the grate level. The doors C are likewise pro- vided for the latter purpose, raising large scars to the surface 70 ELEMENTS OF INDUSTRIAL CHEMISTRY of the bed, but are ordinarily not often required and may be made of the slide pattern and puttied tight if desired. Through the door B the charges are introduced, and distributed as quickly as possible over surface of 'ohe fire bed. The upper doors F, also slide doors, are not open except for occasionally cleaning the upper flue and may therefore be puttied up between times. The cross-section of the upper flue should be carefully figured to avoid rapid currents of gas that would interfere with the exit of gases from the individual burner. These burners are generally built from 4 to 5 J ft. wide and 4 to 6 ft. from front to back. Fig. 35 also shows one method of potting niter (for supplying the nitric oxides to the chambers). The nitrate of soda and sulphuric acid are charged through a covered hopper K, into the cast- iron vessel H, which is supported on a plate in an enlarge- ment of the common flue. Being thus subjected to heat from the burner, the nitric acid is distilled out. The door J is provided for removing the entire vessel. All work that it is necessary to do with the burners should be done as rapidly as possible, so that doors may be open the minimum time. The successive rotation of the burners should be as regular as clockwork. If the number of burners in a set (frequency of charging) is such that two burners are to be charged at once they should always be as nearly as possible diagonally opposed to each other on opposite sides of the set, and the rota- tion should be so arranged that the period of greatest heat occurs in burners half the length of the burner set from each other. No red-hot ore should ever come through the grate bars; in fact, working with any usual depth of fuel bed, the ore when shaken down should be fairly cool. Proper burning of the cinder is superficially indicated by lightness, porosity of surface and a clear red, brown, or black shade (according to the character of ore) with little evidence of mottling, streaking or apparent hard spots. When broken the ore should show no kernel or hard center, but should have substantially the same texture through- out, except right at the suiface it is likely to be more porous and frequently is checked by numerous cracks. Fines Burners. Owing to the difficulty encountered in the burning of fine ore a number of forms of mechanical furnaces have been invented. The two latest and those used most in this country are the O'Brien and the Wedge burners. Even though the former is almost a toy as compared with the latter, it fills its place in smaller works, burning 5 to 15 tons a day. SULPHUEIC ACID 71 The best running capacity of the O'Brien on high-grade ore smaller than i in. is about 6000 to 7000 lbs. per day. The same furnace can properly burn 9000 or even 10,000 lbs., but repairs become excessive. Wedge furnaces range from 12 to 32 ft. in diameter, with five to seven hearths. The 21J-ft. furnace has a capacity of 28,000 to 48,000 lbs., and weighs about 304 tons. The O'Brien Burner. Fig. 36 shows the O'Brien burner, the mechanical features of which need little explanation. The 'cen- tral shaft A is cooled by the vertical current of air passing up through it, The arms B are likewise hollow and subdivided lengthwise nearly to the outer end in such a manner that a portion of the current of air is drawn out sidewise through one side and back again to the hub by the draft of the central shaft acting as a stack. The arms are secured by hubs C tightly fitting into the central shaft. The inner end of the arm tapers, is inserted with the blades D turned sidewise and locks with a quarter turn on its own axis in the direc- tion which the drag of the ore on the blades along its bottom tends to continue. Thus the action of rotation around the central shaft tends to lock the arms more firmly into the hubs, at the same time they can be turned up in the opposite direction by a special tool, removed and replaced in a few minutes. The rabble blades are cast as part of the arm, and given an angular position. They are carried around the central shaft, slowly moving the ore outward or inward on the alternate shelves. The shelves, raked inward, have an opening E around the central shaft through which the gas passes up and the ore falls down. The alternate shelves have openings F at the periphery for the same purpose. A screw feed from the hopper G gives an excellently regulated supply of ore and the cinder passes out through the bottom chutes H that supply a portion of the air for burning. Two doors I are provided to each Fig. 36. 72 ELEMENTS OF INDUSTRIAL CHEMISTRY shelf for removal of arms and have wheeled draft openings J that serve also as peep-holes for observing temperatures. Rota- tion is imparted to the shaft 4 by a very cheap and simple gear which is nearly the whole diameter of the burner and is made by bolting segmental sheets L of i^-in. steel to a flange M on the lower end of the shaft, uniting the periphery of the circular plate thus formed with cheap cast-iron sections of curved racks N which in turn rest upon small pinions 0. If any- thing catches inside the burner the weight of the rack becomes insufficient to keep the gears meshed and the racks jump without breaking or injury, only making enough noise to call attention quickly to the trouble. A vertical chain drive P actuates the large sprocket on the screw shaft Q from the main pinion shaft below. The Wedge Burner. The Wedge burner, Fig. 37, is naturally more substantial in every respect, as required by its heavier duty. The central shaft A is large enough to admit a work- man, its temperature being at all times low enough to per- mit his making any repairs that may be necessary. Each arm B is separately water- cooled and strongly secured to the shaft by a heavy breech lock C, also water-cooled, while the rabble blades are individually removable and replaceable with practically no interruption of the furnace. The hearths are level and have openings E near the shaft and F at the outer edge for drop- ping ore and permitting the rise of gases. The entire top of the burner G serves as a combined feed hopper and feed table, being provided with its own special arms and tripper rakes that swing back under the excessive load of deep-piled ore, thus regulating the feed at the center even if the ore is piled high at the sides, at the same time gradually distributing such a pile evenly. The Fig. 37. SULPHURIC ACID 73 supply of ore entering around the shaft through a sand-lute continually renews the lute and further regulates the feed, cinder being discharged through the chute H. Repair doors /, poke and peep-holes J are likewise provided. The central shaft, all arms and moving parts are supported on the gear M, by means of the four roller bearings N, traveling on the smooth outer face of the gear, the whole being merely centered by the bottom pin P, giving a rigid central shaft with no " steppe" or base block, prac- tically without wear, friction being almost wholly rolling. Obvi- ously the feed is here strictly dependent on the operation of the rake arms and over-feeding or clogging is almost impossible, as is also the failure of the water-cooled arms. Nevertheless the driving pinion is actuated by a shear pin in the hub of this pinion that cuts off if any serious obstruction takes place in the furnace. Dust Prevention. As the gases come from the furnace they are more or less loaded with fine dust carried along mechan- ically by the draft. This dust if allowed to enter the Glover tower would result in serious difficulties. Although the fines burners have many advantages over lump burners, the amount of dust carried into the system is far greater in the former method of burning the ore. It be- comes necessary, there- fore, to remove this dust or at least reduce its quantity. In the oldest method the gases were allowed to pass into a large chamber, where the current was slowed down to a marked degree, thus allowing the dust to settle out. Baffle plates or walls were then introduced into the chamber and found to give much better results. These dust chambers are still used to quite an extent even to-day, an illustration of which is shown in Fig. 38. Centrifugal separators have been invented by A. P. O'Brien, which are entirely feasible when used in conjunction with a fan. He has also adapted them to serve as niter ovens, by placing the pots in the bottom of the conical body. The most effective form of separator is that recently introduced by Henry Howard, which consists of a series of horizontal parallel shelves an inch or so apart, across which the gases pass in a slow steam from the Fig. 38. 74 ELEMENTS OF INDUSTKIAL CHEMISTRY general inlet chamber to the general outlet chamber. The results obtained are truly astonishing, even dust ordinarily regarded as impalpable being largely retained. Glover Tower and Its Reactions. The gases as they come from the burners usually contain from 6 to 8 per cent of SO2, which as they pass over the niter pots become somewhat oxidized, thus bringing to the Glover tower a mixture of sulphur dioxide, sulphur trioxide, oxygen, nitrogen, some oxides of nitro- gen, a small amount of moisture and a little dust. As these gases come in at the bottom of the tower they meet the mixed dilute sulphuric and nitrosyl-sulphuric acids flowing down the stack. Considerable heat is generated at this point, concentra- tion of the dilute acid occurs and the following reaction probably takes place: 2NO2HOSO2+SO2+2H2O = 3H 2 S0 4 +2NO. The sulphuric acid formed here together with the SO3 combine with the dilute acid, thus producing a fairly strong acid known as " tower acid." The gases not absorbed by the dilute acid pass up the tower, various reactions tak- ing place as they progress, finally leaving as a mixture of S0 2 , S0 3 , NO, N2O3 and 2 . The Glover tower must be built to stand the severest duty and is well illustrated in Fig. 39. The interior is of heavy lead construction and is filled with acid proof brick. At the top is an arrangement for the proper control of the supply of nitrosul- phuric acid and dilute acid, the former being introduced to furnish the nitrogen oxides and the latter to decompose the former. Chamber System and Reactions. Fig. 40 illustrates a typical arrangement for the chamber process. Near the top of the Glover tower is a favorite place for locating a fan (4) which Fig. 39. SULPHURIC ACID 75 takes the gases from the Glover to the first of the lead chambers. It is customary to make the first chamber (5) fairly large, as the gases are at first converted rapidly. In this chamber the gases come into contact with water in the form of steam or spray and with atmospheric oxygen. Here about one-third of the entire output of a plant is formed. Many and complicated reactions take place in this chamber as well as in the following chambers. The conditions of working prevent a definite knowledge being obtained, so that it is a matter of theory and each authority has his own particular theory. Certain definite changes do, ffiw€m Fig. 40. however, take place which may be expressed in the following reactions: S0 2 +N 2 3 = S0 3 +2NO; S0 3 +H 2 = H 2 S0 4 ; 2NO+0 2 = 2N0 2 . Thus it is that the oxides of nitrogen serve to convert the sulphur dioxide to the trioxide, which in the presence of air revert to their original condition and again repeat the cycle. As the ga-es pass from the first to the second chamber and then to the third chamber the content of sulphur oxides becomes less and less, until finally in the last chamber their composition is largely a mixture of XO and N0 2 or what is usually spoken of as N2O3. 76 ELEMENTS OF INDUSTRIAL CHEMISTRY The Gay-Lussac Tower and Its Reactions. The gases coming from the last chamber are passed into the Gay-Lussac tower, which is somewhat similar to the Glover tower in its construction. Into the top of this tower, however, is introduced a supply of concentrated sulphuric acid obtained from the bot- tom of the Glover tower. The gases meeting this strong acid are absorbed according to the following reaction: N 2 3 + H2SO4 = 2NO2HOSO2 + H 2 0. The nitrosyl-sulphuric acid thus formed is pumped to the top of the Glover tower, where it is used to furnish the oxides of nitrogen for the chamber reactions. CIRCULATING SYSTEM. It is now proper to describe in more detail the acid circulating system and the apparatus provided for this purpose. It will be apparent that large quantities of acid have to be elevated to the tops of the towers. Calculation shows that the nitrous gases for their sufficient recovery require that an amount of 60° Be., equivalent to 60 per cent of the total production of the chambers, be run down the Gay-Lussac per day. In practice this is generally 90 to 150 per cent. When intensive work is used, 150 to 300 per cent is needed. This lifting has almost universally been done by compressed air admitted into vessels, Fig. 41. These " eggs " are filled with acid through a pipe contain- ing some form of check valve that prevents its return. Air is then automatically or manually ad- mitted through another pipe. A third pipe from the bottom of the vessel permits the acid under pressure to leave the vessel fol- Fig. 41. lowed by the rush of air of equal or slightly greater compressed volume than the acid pumped— a method wasteful in the extreme. Fig. 42 shows one of the automatic Kestner lifts attached to a small acid egg, the operation of which will be apparent from the illustration. These Kestner lifts have been used for years by many of the largest acid manufacturers and have given entire satisfaction. Moderately heavy walled lead pipe is used through- out the chamber plant for the transportation of acid. Recently lead-lined iron pipe has found great favor for that portion of SULPHURIC ACID 77 the acid lines subjected to very heavy pressure (like those from the eggs to the heads of the Gay-Lussac tower) or to jars by reciprocating pumps or lifts. Geared pumps if made of iron ffrfr require excessive repairs. Stone- [5, ware pumps have not this objec- tion, but are hardly safe to use above 30 lbs. pressure or 40 ft. acid-head. Centrifugal pumps, arranged in stages, have been tried with excellent success for low lifts of strong acid, but in [he chamber work all of the acid is 62° or weaker and the neces- sity for perfect regularity of opeiation makes it undesirable to multiply the mechanical devices necessary to accomplish the single lift. Positive acting steam pumps have been used successfully for acid, but are corroded and it is doubtful whether they are any more economical than the best air lifts (Pohle) where the necessary depth is obtainable. Pohle lifts consume only about half the air required for blowing by eggs, furnish a steady stream like a pump, are without moving parts and can be made practically free from wear. MOVEMENT OF GASES. The fans used for actuating the gases in the chamber system are of three types, according to loca- tion, between the dust chambers and the Glover, between the Glover and the acid chambers, or between the acid chambers and the Gay-Lussac. In the first case a steel fan, water cooled, is used very success- fullt in handling the hot gases; in the second place a regulus metal fan is frequently used and in the third instance a stoneware fan may be employed. Purification" of Sulphuric Acid. Sulphuric acid as manufactured in the chambers, particularly as concentrated in the Glover tower, exhibits certain impurities that are quite important from an industrial point of view. These are lead, iron, arsenic, selenium, antimony, aluminum salts, nitrous oxides 78 ELEMENTS OF INDUSTRIAL CHEMISTRY and nitric acid, platinum, mercury, the alkalies, calcium, and copper. It is found that if the acid is treated with H2S for the lemoval of arsenic, practically all other impurities are removed at the same time and the acid is even clarified from some inert suspended matters that are undesirable in appearance only, if, however, a thoroughly pure and limpid acid is required, there is practically no way of obtaining it except by distillation on the one hand or the use of the contact system on the other. Sulphuric acid as made in the chambers will vary in its arsenic con- tent from about 0.1 per cent up to about 0.3 per cent according to the ore used and the amount of dust carried over from the burners. Of the various methods used for the precipitation of the arsenic and other impurities by generation of the H2S within the liquid, probably the best, and certainly the most frequently used, has been the precipitation vyith barium sulphide. The advan- tages presented by barium' sulphide are twofold. First, the barium itself is precipitated as sulphate in the liquor and adds greatly to the weight and density of the precipitate. Second, substantially no soluble material is left in the liquor to inter- fere with subsequent concentration or use of the acid. The acid, however, must be diluted to sp. gr. 1.4 containing 50 per cent of H2SO4. To obtain the best results it must then be heated to about 80° C. and a warm solution of barium sulphide 7J° to 8° Be. run in at the bottom of the vessel in such a manner as to prevent the escape of H2S. The most convenient way of doing this is to divide the liquid through as many small openings as will permit the passage of the gas without plugging up by forma- tion of the precipitate. These openings may preferably be placed beneath a perforated shelf of lead, or a ribbed shelf without perforations but around the edges of which are serrations to divide the bubbles of gas again. The separation of the purified liquid from the mud may be carried out by either of the usual nitration methods. The only objection presented by the barium sulphide treatment is that the purification cannot be carried so far in this way. Nearly double the amount of arsenic remains in the acid. This can, of course, be removed by subsequent treatment with gaseous H2S, but if the treatment by gas is to be undertaken, the whole operation might better be carried out by the gaseous method. The Concentration of Sulphuric Acid. Two systems of concentration, illustrating the wide range of principles employed in practice, will be described. SULPHURIC ACID 79 The first installation, Figs. 43 and 44, will be that likely to be found in a chemical plant manufacturing a good grade of 66° acid. The acid will have been purified in some man- ner, probably by the use of H2S gas, and will be ap- proximately 46° Be. Lump burners will be found of the usual type except that prob- ably the flue above the arches will be somewhat higher at one end. The common flue above the burner is crossed at suitable intervals with sup- porting beams, set in reinforced concrete. Beginning vvith the burner furthest away from the supply of acid, the flue is very low, increasing in height toward the acid supply end. This results from the successive rise of the lead pans to Fig. 43. Fig. 44. allow for the downward flow of the acid. Upon these protected I-beams are laid cast-iron plates, If ins. thick at the lower end and 1 in. at the upper end furthest away from the burner arch. Passing backward along the flow of the acid each of the beams is raised 1 in. higher than the preceding. On the iron plates a layer of coarse sand is placed, as thin as can be made with absolute certainty of everywhere having a separation of sand between the iron and lead in order to prevent immediate contact between them, as these points would thus become over- 80 ELEMENTS OF INDUSTRIAL CHEMISTRY heated and cause excessive corrosion of the lead. Two or three layers of thin asbestos paper may be used instead of the sand. The pans vary gradually in depth from 8 to 14 ins. and vary also in thickness. After the pans are all in place the long double edges where they abut are bent over to form lips. From the series of pans Fig. 44, the acid continues its downward flow into another series of pans Figs. 45 and 46, which may immediately adjoin the first series or be located in an entirely different build- ing. These pans utilize the waste heat from the higher concentration apparatus to be described, and are located over the flue supported on perforated cast-iron plates. These plates give a larger output with entire safety and better fuel economy, but do not serve to protect the flue below as do the solid plates rimmed around the edge. Fig. 45. Fig. 46. The acid then flows from the pan to the platinum still, the rate of flow being regulated automatically. PLATINUM STILLS. Many shapes and patterns of platinum stills have been designed and special advantages claimed for each. In all probability the net result is just about the same in the long run except that the lower and longer pans are more economical of platinum. Some stills are provided with baffle partitions, causing a circuitous flow of the acid through the still, the advantage claimed for these being that a better concen- tration is obtained in a single operation. Against this must be set, not only the small increase in platinum, but also the very SULPHURIC ACID 81 great increase in liability to leakage and in irregular strains on the bottom of the pan. Corrugated bottoms are used in some patterns of platinum still. They present about 60 per cent more surface for transfer of heat, but on the other hand, increase to some extent the difficulty of making side joints and conse- quently the liability to leakage. They have, however, the advan- tage of stiffening the bottom. Lining with gold has been found greatly to increase the life of the platinum pan and, at the present relative prices of gold and platinum, is a very marked saving. Gold resists about seven times as well as platinum. The gold is not plated on or attached by dipping, but must be attached by the method invented by one of Heraeus's assistants. The over- heated gold is poured on top of the platinum ingot heated nearly to fusion, forming a double ingot, which is then rolled into the sheet to be made up into stills. Owing to the prohibitive cost of platinum it is being aban- doned almost completely in England. Better designed stills with tile lining, Kestner stills, towers, or silica dishes in cascade are rapidly replacing it. THE CONTACT PROCESS. The name is derived from the fact that by mere " contact " with a so-called catalytic material, the SO2 of burner gases and the oxygen of the residual air are caused to unite to form SO3, which is then either separated out by cooling (not usual) or absorbed in sulphuric acid of high strength, either maintaining the strength of this acid against the dilution by weaker acid (or water), or else increasing the strength of the absorbing acid above 100 per cent by the absorption of SO3 in H2SO4. When the acid arrives by absorbing SO3 at a strength at about 106 per cent, equivalent to 26.8 per cent per SO3 dissolved in H2SO4, absorption becomes slow. The word catalytic is something of a cloak for ignorance. Between the temperatures of 300° C. and 900° C. the mere presence of platinum in a finely divided state, or plat- inum black serves to very greatly accelerate the reaction SO2 -f 0±=>S03- At first sight the platinum black appears to take no part in the reaction. It merely glows and gives off heat. The action starts about 325°, and is most complete between 400 and 450°. Similar but less effective results are obtained at higher temperatures with ferric oxide, particularly ferric oxide containing a little copper oxide; also chromium oxide and even hot silica and quartz assist the rate of progress toward equilibrium. It may seem that none of these materials take part in the reac- 82 ELEMENTS OF INDUSTRIAL CHEMISTRY tion, but probably each of them does in one way or another. Particularly is this the case with oxides of iron, copper, chromium and with the sulphates of alkalies and alkali earth metals. In the light of more recent knowledge, the original meaning of " catalytic " must therefore be abandoned or modified to the extent that a catalytic reaction may be defined as a reaction which leaves one of the assisting compounds substantially un- altered after the completion of the reaction. According to the law. of mass action such a catalyte or intermediate reacting compound is not to be expected to affect the ultimate equilibrium of the reaction, that is, the final extent to which the reaction proceeds in an infinite length of time. The function of the catalyte is merely to affect the rate at which the reaction pro- ceeds, and thus to give it sufficient rapidity to be of practical interest. Sulphur dioxide and oxygen unite to some extent (at a very slow rate at 350° to 375° C.) whether or not a catalyte be present. The presence of a suitable catalyte (possibly acting as a carrier of oxygen, similar in effect to the lower oxides in the chamber process) greatly increases the rate of reaction so that the sulphur dioxide and oxygen at 375 to 450° combine rapidly and produce sulphur trioxide with nearly theoretical complete- ness. Construction of Contact Plant. In order to illustrate the various principles used in the construction of contact plants, it would be necessary to describe a number of different plants more or less in detail provided actual installations were used to illustrate the principles. Instead of that a typical arrangement of the installation is given in Fig. 47, in the form of a schematic diagram which will be described in detail and which illustrates the principles used in the majority of the contact plants in this country. Air enters at the opening A into a drying tower B filled with quartz or other loose material down through which strong sul- phuric acid is flowing. The air passes up through this tower and on its way is almost completely dehydrated. It then passes down by the pipe B\ to the pyrites burners C into the cinder pit under which it is admitted by the pipes B2, B%, B4, etc. The doors of these burners C are of two kinds, upper and lower, the upper being for the insertion of the pyrites and the lower for the removal of the cinder. Both of these should be made as tight as possible by the use of asbestos gaskets and screw spiders or similar devices. Through the flue above these burners the SULPHURIC ACID 83 gases pass into a contact shaft D, where they pass over the cindei produced by the burners. This cinder is removed through the doors C-2 from the burners, is screened in order to remove dust and a portion of it is then put in through the funnel into the contact shaft D. About 10 per cent of the cinder is used to advan- tage in this way. The necessity for renewing the cinder arises through the accumulation of dust in the interstices and the fact that the cinder gradually becomes so saturated with arsenic and other impurities that it does not react promptly. The chief consideration, however, is the reduction of draft by stopping Fig. 47. up the interstices with dust. A portion of the cinder may then be shaken down into the cinder pit of the contact shaft and lemoved by the door Di. By the heat of the gases direct from the burners this contact shaft will be maintained at a temperature between 600 and 800° C. and in order not to have the temperature fall too low, the shaft is jacketed as well as pos- sible by somewhat heavy walls of brickwork and other devices. As the whole burner system and contact shaft operates under suction, it is preferable to enclose the entire setting in a steel plate cover closely riveted and calked. In this contact shaft the gases are partly converted, about 40 to 50 per cent of the SO2 present when they leave the burner chambers being changed 84 ELEMENTS OF INDUSTRIAL CHEMISTRY over into SO3, and sufficient heat being generated b}^ this reaction to maintain the temperature of the gases. Leaving the con- tact shaft by the pipe D3, the gases are somewhat cooled and are introduced into the cooling tower E. This tower consists af a riveted steel plate shell over the outside of which water is poured, the water being collected in a trough at the bottom and carried away. Some acid condenses in the pipe D3 and runs into the tower E. Also consideiable acid collects in the tower E and is removed by the pipes shown at the bottom. One such tower, unless of considerable size, would be insufficient to cool the gases so that they pass through the pipe Ei into a second tower E2 (or third) of similar character, whence thoroughly cooled they pass by the pipe E3 into the absorbing tower F. This tower consists of either riveted steel plates or semi-steel castings, or cast iron poured into a mold containing a wrought-iron outer shell. The reason for this precaution is that cast iron is affected by SO3 in a peculiar way, the SO3 seeming to enter into the pores of the cast iron and cause a gradual expansion, placing the metal under such strain that it cracks or even bursts apart. The tower F is filled with quartz or similar surface-exposing material and is fed from above with a slow stream of acid for the purpose of absorbing the SO3 in the gas. From the tower F the gases pass on to the pipe F\ into the tower F2, which is of similar con- struction and likewise provided with a flow of acid, the strength and character of which will be mentioned later. Thence through the pipe ^3 the gases pass to the blower or actuating means for the system, the part of the apparatus hitherto described being operated under suction. From the blower the gases pass by the pipe H to a series of valved branches Hi, H2, Hz, etc., leading into filters I, I\, I2, etc. These filters are mere boxes of iron or lead containing a deep layer of fine coke, or fine slag from the basic open-hearth process. In either case the action is largely one of gaseous filtration, in order to remove the last suspended impurities that have not been taken out by the washing or the centrifugal action of the fan. This purification is so thorough that the gases no longer betray the presence of the dust in a strong beam of light nor do they yield up any impurity to filtra- tion by a close plug of cotton wool. If there be suspended sul- phuric acid left in the gases they will blacken the plug of cotton wool, or if any traces of dust remain these will be deposited upon the cotton and show their discoloration. The number of filters are thus placed in parallel in order to permit the cutting SULPHURIC ACID 85 out of one filter by closing the entrance and exit valve and the renewing of the filtering body without interruption of the process. From these filters, the gases, thoroughly purified, pass away through the valved connecting pipes 1 3, 1 4, 1 5, etc., to the assem- bling gas main J. From here two courses are open to them, but the normal course used as a rule throughout the operation of the plant will be first described and the emergency course J\ described later. Normally the gases pass through J 2 downward through the valve K3 into the heat exchanger M . This heat exchanger is constructed very much like a tubular boiler having the tubes Mi connected between headers M2 and M3 and the incoming gases pass downward through these tubes and out of the heat- exchanger by the pipe M± up to the distributing main K. During the passage through the heat exchanger M they have been partially heated up by the hot gases passing away from the platinum converter R. They are again heated up by being passed down through the heat exchanger N of similar construction, having the pipes A r i between the headers N2 and N3 outside of which pipes are passing the hot gases from the first converter Q. The now thoroughly heated gases leave the heat exchanger N through the pipe iV"4 and pass upward into the pipe and downward through O2 into the converter Q. This converter consists of a cylindrical cast-iron box containing a number of layers of platinized asbestos supported on punched sheets of steel. The gases passing down through this platinized asbestos are further converted and heated by this action. They then pass away through the pipe Q2, and around the pipes Ni and are cooled by the incoming gases passing through the inside of these pipes. From this heat exchanger they pass through the pipe Q3 into the second platinum converter R, having similar layers of contact material Ri supported on steel trays. This converter may be somewhat larger in order to insure the complete conversion of the now nearly exhausted gases. From here they pass through the pipe R2 into the heat exchanger M, where they pass around the outside of the pipes and give up some of their heat to the incoming gases, passing down through the pipes. Leaving this heat exchanger through the pipe P3 they pass the final cooler S, which is again constructed somewhat like a boiler having headed pipes Si between the headers $2 and S3, only in this case instead of being cooled on the outside by gas these pipes are cooled by water fed through the pipe $4 and overflowing to the pipe S5. The now thoroughly cold gases pass 86 ELEMENTS OF INDUSTBIAL CHEMISTEY through the pipe Sq into the absorbing tower T. This tower is filled with porous or other acid-proof material and is sprayed with acid from the distributer I2, after which the gases are per- mitted to exit through the pipe Ts to the atmosphere. The passage of the various liquids used for treatment of this gas should now be traced. The acid for absorbing sulphur trioxide from the iron conversion enters through the pipe a to the tank b at the foot of the tower F2, and adds itself to the liquid flowing down from the tower. Thence it flows to the pipe 61 into the egg c, and is thrown up by the pipe c\ into the tank d at the head of the tower. The acid added by the pipe a should be of such strength and quantity as to maintain the flow of acid down the tower F2 somewhere between 93 and 99 per cent, preferably about 97 per cent, because the absorption of SO3 is much more rapid and complete in sulphuric acid between 97 and 98 per cent than in acid which is either much weaker or stronger. From the tank d most of acid is permitted to flow down the tower F2, but as the acid increases in quantity through the absorption of sulphur trioxide on the one hand and the addition of weaker acid from the pipe a on the other hand, the overflow goes to the supply tank e of the tower F, whence the acid trickles down in a slow stream through the tower F and may be raised to a strength equivalent to 105 or 106 per cent H2SO4, and be taken to the finished acid tank g. Calling the acid 105 per cent means that the sulphuric acid contains sufficient sulphur trioxide dissolved in it that, when the necessary water is added to unite with this sulphur trioxide and produce sulphuric acid, the total quantity of acid of 100 per cent produced will be 5 per cent greater than the amount of H2SO4 and SO3 taken. The strength may likewise, of course, be expressed by giving the per- centage of free SO3 dissolved in the H2SO4. The acid collected by condensation in the cooling towers E and E2 will be impure owing to the amount of dust carried over from the iron contact shaft and may profitably' be used in the preliminary drying tower B flowing down the pipes g$ and g± into the egg h whence it is blown up by the pipe hi into the tank i at the head of the drying tower. The excess of the drying acid thus accumulated may be flowed over to the pipe h 2 and utilized for any convenient purpose in the works. A deficiency of acid from these cooling towers is made up from the finished tank g by adding acid through the pipe g\. The absorption of the sulphur trioxide produced by the plati- SULPHURIC ACID 8? num contacts Q and R may be completely carried out in a single tower T provided the strength of the acid in this tower be main- tained at the most advantageous point between 97 and 98 per cent. A steady flow of weaker acid is taken in through the pipe j to the tank k, where it is cooled and thoroughly mixed with a stream flowing out through the pipe h from the tower. From a special compartment of this tank or an independent tank located beside it, &2, the acid is thrown up by a centrifugal pump or other convenient means by the pipe £4 into the supply tank I at the head of the tower, whence it flows through the pipe h to the distributer within the tower. A heavy stream of acid is carried in order that the sulphur trioxide absorbed may not too greatly increase the percentage of the acid on its way down the tower. Whatever excess of acid is formed in this system, as in the other, overflows to the tank k% and is regarded as finished acid. Owing to the careful preliminary purification of the gas this acid is very much purer than that produced by the iron contact. In some plants, therefore, the iron contact is not used and the gases pass directly from the burners into a large cooling chamber that takes the place of the towers E and E2, after which it is washed with sulphuric acid, as in the towers F and F2, which without the iron contact does not increase the volume of the supply liquid materially because there is no sulphur trioxide to speak of. By using stronger sulphuric acid in the tower F2 the gases are thoroughly dried and are prepared to go to the filters. The complete conversion is carried out in two steps in the con- verters Q and R and all of the sulphur trioxide produced is then absorbed in the tower T by 97 to 98 per cent acid. In such an installation the parts D, B, h and i would be omitted, as the pre- liminary purification of the gases has been shown to be more effective if the gases were moist. In fact moisture is injected into them as they leave the burners and before they are cooled in the laige chamber which according to that method of working would replace the cooling towers E and E2. In the other method of working the gases instead of passing through a more complicated conversion like that shown would be heated by exchange with the gases as they left the iron contact D, and would then be taken directly to a single platinum con- verter which might be located between two iron contact shafts or in any other convenient position for sustaining its temperature. The second stage of the absorption of the gases sulphur trioxide thus produced might, of course, be carried out in a second set of 88 ELEMENTS OF INDUSTRIAL CHEMISTRY absorbing towers similar to F and F2. If a very complete con- version is to be made in the final platinum converter the tem- perature must be carefully regulated and provision made both for additional heating of the gases and reducing the amount of heating action. When it is necessary to increase the temperature of the gases passing through the first converter Q, as for instance in starting up of the plant, the heater P is available and provision is made through the valve 0\ and P2 for passing the gas through this heater into the pipe O2 by shutting the valve whenever this is desired. The heater P consists of an ordinary coal heater of special design provided with the firing door P3 and having inside heating pipes Pi and a stack for exit of the coal gases, Pq. When, on the other hand, it is desired to reduce the temperature of the gases passing through the first converter it is possible by opening the valve Ji to admit cold gases directly from the pipe J into the pipe L and thence into the converter. When a less violent cooling action is desired the valve K2 may be opened and the gas admitted to the pipe K before passing through the heat exchanger N. It will be obvious that the purpose of breaking up the conversion into a series of stages is to reduce the amount of heat liberated at any particular stage and avoid the necessity of cooling the gases during conversion. It amounts substantially to using a weaker gas at each stage in the conversion. Another method of getting at the same result is to make the converter Q very much wider and allow the radiation from the thin layer of con- tact material at the top to preheat the gases to such a degree that the contact mass itself is sufficiently cooled by radiation to the upper portion of the converter in which the gases are being heated. Another method of securing this result is to construct the converter like the heat exchangers N and M and to place the contact material within the tubes, passing the gases on their way to the contact around the outside of the tube so that the mass in the tube is continually kept cool by the passage of the gas around the outside. This was the method devised originally by Knietsch for maintaining within the contact chamber a temperature which at the hottest portion of the chamber should be between the com- posing and decomposing temperatures of sulphur trioxide. This most elegant form of contact chamber which combines within itself the converter proper, and the heat transferrer is illustrated in Fig. 48. The gases, after leaving the burners and being mixed with steam and cooled in a large cooling and settling chamber designed to take the place of the towers E and E2, Fig. 47, were SULPHURIC ACID 89 then washed as in towers F, F2, the washing being repeated in successive towers until the gases no longer showed any impurity. Special washing liquid might be used for different characters of special impurities depending on the kind of ore used and they were then finally dried in a tower like F2. Such gases were then passed directly in through the opening A, Fig. 48, whence they were permitted to circulate back and forth across the outside of the pipes B extending down through the chamber and finally reaching the bottom of this chamber to pass upward through these pipes themselves and to the contact material supported in layers within , these pipes. As the gases became heated on their way down to the end of the pipes and as the reaction at this entrance was more violent, the temperature at this point rose to the desired degree and the conversion proceeded very rapidly. Then as the gases passed on through the contact material contained in the pipes they would find cooler and cooler layers of contact materials so that their equilibrium might be retained at its most complete stage, at approximately 400 to 425°, before being removed from the pipes. In this manner 90 to 95 per cent or even 97 per cent of the SO2 may be converted in a single con- verter, and if desired, the temperature of the gases can be raised partly by an added exterior transferrer, through which the con- verted gases pass on their way to being finally cooled and absorbed. The final cooling may take place in a separate cooler, S } Fig. 47, or the absorption liquid may be so rapidly cooled that the hot gases can be cooled and absorbed simultaneously. If strong oleum is to be made, however, they should first be thoroughly cooled. If 98 per cent acid is to be made a single absorbing tower may be used, but if oleum is to be made it is more desirable to carry the absorption out in a series of towers, the last of which is supplied with 97 to 98 per cent acid in order to make an entirely complete absorption. Broadly speaking, it may be said that the cost of manu- facturing sulphuric acid by the contact system is not much, if any, higher than that by the chamber system. The operation i- somewhat more sensitive and delicate and involves the use Fig. 48. 90 ELEMENTS OF INDUSTRIAL CHEMISTRY of more refined machinery, so that a higher class of labor has to be employed. The conversion when the contact system is operated properly is practically as complete as that in the cham- bers. Well designed, the contact system requires practically no fuel for preheating the gases and the power required for driving the gases through the more resistant series of chambers used in the contact system is more than made up by the absence of niter consumption. The cost of installation is somewhat higher owing to the considerable quantity of platinum used, hence the attempt to substitute other materials as oxide of iron, but it is doubtful whether in the long run the substitution works any economy. One advantage of the contact system, particularly where platinum alone is used, is the great purity of acid resulting from the necessary thorough purification of the gases, but for ordinary manufacture of sulphuric acid, particularly in districts more or less remote from foundry and machine shop facilities, there is considerable question whether the contact system offers great inducement to the manufacturer. CHAPTER V NITRIC ACID PROPERTIES. Strong nitric acid when free from lower oxides and freshly made is practically colorless, but the action of light, slightly elevated temperatures, or traces of organic matter, generally gives it a slight pale amber tint gradually developing into* a clear pale red-brown. It is more mobile than sulphuric acid of like strength and about one-third lighter in weight. Pure acid of 99.5 per cent reaches a specific gravity of 1.52 (49.6° Be.). Unlike sulphuric acid, the anhydride is not stable in solution in the acid (unless H2SO4 is present), so strengths higher than 100 per cent are not made, but N2O4 dissolved in the acid increases its specific gravity until 12 per cent of N2O4 has a density of 1.62 (about 56° Be.), and shows a greater oxidizing power than the pure acid. The destructive action of nitric acid on organic matter is rapid, partly oxidizing and partly nitrating (forming nitric esters or NO2 substitutions). The oxygen-containing bodies of the paraffine series tend to form oxalic acid, the — CHOH groups to form esters, a characteristic also exhibited by cellulose, glycerine and under proper conditions, starch. The sulphur-containing bodies tend to sulphonic acids, while the aromatic series is char- acterized by its greater tendency to form nitro derivatives. Most ordinary metals are attacked by nitric acid of various strengths, gold and platinum excepted. The hydrogen liberated acts upon the nitric acid to reduce an additional portion of it, liberating various oxides of nitrogen, depending on the concentration of the acid and the temperature. Broadly speaking the more con- centrated the acid the more higher oxides will be produced and dilute acid will be largely reduced to ammonia. Lead and iron, however, are somewhat slowly acted upon by strong acid, iron in particular being the material generally used for the dis- tilling parts of nitric acid apparatus. Its protection at this point is due to three causes, chiefly the presence of sulphuric acid, superseding or inhibiting the action of the nitric and form- ing insoluble sulphates which orotect the surface; second, the high 91 92 ELEMENTS OF INDUSTRIAL CHEMISTRY temperature which prevents condensation of acid on the surface, and lastly to some extent the peculiar passivizing action which nitric acid possesses for iron surfaces. OCCURRENCE. The usual commercial strengths of nitric acid are " 38° " (56.5 per cent), " 40° " (61.4 percent), and " 48° " (91.4 per cent). " Pale acid," " free from lower oxides " (that is, less than 0.1 per cent of NO, N2O3 and N2O4) may be of any strength, but is generally made from acid stronger than 40° Be. (sp. gr. 1.381) by dilution because the weaker acid does not " bleach " well. " Red acid " is generally 40° Be. or stronger and contains dissolved lower oxides. " Dynamite acid " is strong acid for making 96 per cent mixed acid (34 per cent HNO3 and 62 per cent H2SO4). It was formerly necessary to have the nitric acid 93 per cent, but now that " oleum " is used, it need only be 88 per cent. " Spent acid " is the mixed acid diluted and partly deprived of HNO3 by use in nitrating organic substances; and " fuming nitric " is very strong acid containing much lower oxides. " Weak nitric," generally applied to acid 38° Be. or less, obtained from the final towers or tourilles of the condensing system, is also frequently called " tower acid," particularly when used to supply the Glover tower of a chamber system. " Aqua fortis " or " strong water " (because of its great solvent power) is the name given nitric acid by Geber (a.d 750-800), or one of his immediate prodeces- sors, who made it by heating together saltpeter, copper vitriol and alum. The first mention of the present process of making it is by Basil Valentine (a.d. 1450-1500) who says, however, that this method had long been used. Nitric acid was, therefore, one of the earliest mineral acids known. MANUFACTURE. In this country Carter & Scattergood of Philadelphia began the manufacture of nitric acid in 1824 but the industry was not very important until 1862, when the dis- covery of nitroglycerine, followed by other nitro-explosives, opened a new field for it. Two general methods of making nitric acid are important, first, the old reaction of Basil Valentine from nitrate of soda (natural deposits) by action of an excess of sulphuric acid and distillation of the liberated nitric acid, the reaction approximating NaN0 3 +H 2 S04 = NaHS04+HN0 3 . The second method is synthetic and developed from Sir Wm. Crookes's fascinating suggestion in 1890, that the ultimate exhaus- NITRIC ACID 93 tion of the natural deposits should be anticipated by perfecting the combustion of air, giving a practically inexhaustible source of nitrogen products for fertilizers. This modern process consists in burning the nitrogen of the air with its oxygen in an elongated electric arc and quickly cooling the resulting gases. It is only within the last five years that it has developed commercially — principally in Norway, Sweden and Switzerland because of the cheap water power available there. Mixed oxides of nitrogen are thus produced and their oxidation completed in reaction towers after which they are absorbed in milk of lime. The acid neutralized produces " nitro-lime," chiefly used for fertilizer. It is question- able whether the production of strong nitric by this process can be carried out economically except when extremely cheap electric power (from waterfalls) is available. In this country one com- mercial failure was made during the early stages of the develop- ment of this process, but another installation is practically com- pleted and under much more favorable auspices promises better results. Weak nitric acid increases in strength on dis- tillation until 69 per cent is reached, after which a hydrate (2HX0 3 -3H 2 0) of about 70 per cent HNQ 3 distills over at a constant boiling-point. Some methods of overcoming this difficulty and making the synthetic process directly available for the production of strong acid, have been proposed but com- mercial success has not yet been attained. The practical processes, then, make nitric by treatment of sodium nitrate with sulphuric acid. Four methods of decom- posing have been claimed as successful, those of Prentice, Uebel, Yalentiner and the various forms of plain still (most generally used in this country). Prentice Process. This method consists in continuously mix- ing the nitrate and an unusually large excess of sulphuric acid in a separate vessel provided with a condenser to which the X2O4 and CI liberated are supposed to pass, leaving the nitric to be distilled off free from these impurities. It was said to have worked for some time satisfactorily at Stowmarket, England, and to be capable of producing its entire output at a strength of 94 per cent. The feature apparently most criticised was that 12 parts of oil of vitriol were required for 10 of nitrate of soda, but this is no more than should be used to get a good niter cake containing 30 per cent free acid, easy to fuse and fluently mixing. A very slight loss of nitric, at 4 J cents per pound, quickly makes up for any saving in sulphuric, at half a cent per pound. The acid 94 ELEMENTS OF INDUSTRIAL CHEMISTRY then made was not what we would regard as well bleached but this could easily have been remedied. Uebel's Process. In this system, Fig. 49, half of the niter cake (approximately NaHSC>4, which results after expelling the last nitric acid from a charge in retort A) is to run into an equiva- lent weight of moderately strong sulphuric acid in the pan B lo- cated over the flue C. In this pan the heat of the niter cake serves to drive out 15 or 20 per cent of water from the sulphuric acid, and form practically anhydrous " poly sulphate " NaH3(SQi)2- This is maintained in a fused condition by the heat of the flue C below, retained by the cover D, and is drawn off by the valved pipe E and the gutter F into a hoisting pot G that can be elevated by chain fall or power hoist and by trolley rail carried over the feed hole of the retort H or H'. These are charged alternately, at intervals of about 4 hours, with 700 to 900 lbs. of nitrate of soda, dried by spreading out in the iron pans J. Charging is done through the feed hole K, which is then closed with a stone or stoneware plate L and covered with nitrate of soda. Some- times the hoisting pot is provided with a bottom nipple (fitting a NITRIC ACID 95 small hole in the plate L) closed inside with a plug valve. Some- times the fused " polysulphate " is poured in. Particularly in the latter case it must be added slowly, as the hot liquid liberates considerable nitric acid as vapor. To avoid unnecessary heating at this stage the damper M is closed, all the fire being given to the retort H', which is then being boiled off. When the polysul- phate is all in (about 4 minutes) the damper M is opened and the boiling off of H is begun, which occupies from 2 to 3 hours. During this time boiling off of H' is completed, the damper M' is closed and by opening the valve the liquid bisulphate in H' is run down to the lower retort A. The retort A is never wholly emptied (except in shutting down) so that the incoming bisulphate Fig. 50. blends with the already highly heated charge and thus gives up the last of its nitric acid. The now empty retort H' is then ( usually after slight cooling) charged with its nitrate of soda and a fresh hoisting pot of liquid polysulphate. As a matter of fact, however, Uebel's retorts are generally operated with sulphuric instead of polysulphates. Valentiner Process. By this method the nitrate is decom- posed under a vacuum. At first the suction was commenced as soon as the charge was made and increased until about one-third of an atmosphere remained, when the heat was applied. It was found, however, that the intimate mixture of nitrate and acid was better insured, and frothing which carried suspended nitrate upon the sides of the retort, was prevented by throttling the outlet of the gases. About 2200 lbs. of nitrate is charged into the retort A, 96 ELEMENTS OP INDUSTRIAL CHEMISTRY Fig. 50, through the hole B having an iron lid, which is then care- fully diluted. Sulphuric acid (2360 lbs. 66° o. v. or preferably 96 per cent) is then run in from a measuring tank or scale tank C by a pipe D goosenecked and provided with a cock. When the acid is all in, suction is applied by the means of the 12X16 inch, 60 r.p.m. vacuum pump E. This is protected from the acid fumes and chlorine liberated from any NaCl in the niter by a series of wash bottles alternately empty and about half filled with milk of lime. Pipes may be arranged as indicated to insure against either sucking back or absence of liquid in its proper wash bottle when operating. Under the suction and heat of reaction rapid evolution of nitric vapor begins. To prevent its becoming too rapid a throttle plate with a small hole is inserted between the still and the gas pipe G, which is provided with a Y-branch for cleaning and is surmounted by a short length of wire-covered glass pipe H for observing the color of the passing vapors. A reducer pipe to 2\ ins. then takes the gases to a small tourille / filled with broken pumice, where entrained sulphuric or niter dust are separated. Thence the gases pass through two large stoneware coils J and K (2 J ins. bore and about 45 sq. ft. cooling surface), placed in wooden tanks supplied with cold water at the bottoms and provided with overflows near the tops. Here the acid is largely condensed and most of it flows into the large receiver P. Wire-covered glass pipes L and M are provided at the outlet of each coil for observing the color and rate of flow of the acid and a device N for drawing samples for testing. A three- way cock is provided to pass any weak or discolored acid into the smaller jar S, the flow to which can be observed at R. Any air or uncondensed vapor from the coils passes through the pipe Q and the jars S and T, where it deposits some acid, and then upward through the reflux cooling worm V, 2\ ins. bore about 22 sq. ft. cooling surface, where nearly all the condensible vapor is caught and returned to the jar T. Weaker acid collected in S and T may be added to the 96 or 98 per cent sulphuric used for charging the retort. Bleaching of the acid is not required in this process for two reasons : the solution pressure of N2O4 and CI in the acid is greatly reduced by the vacuum, and also the low temperature of vacuum distillation causes very little breaking up of the nitric to form N2O4. The slight loss corresponding to the HC1 liberated and oxidized to nitrosyl chloride at the expense of nitric is inevi- table. No loss by leakage of joints can occur under suction and less breakage of stoneware results from the lower temperatures NITRIC ACID 97 employed. More continuous rapid evolution of vapor makes it possible to run off the charges in about eight-hour cycles. After the first application of two-thirds of an atmosphere suction it gradually increases as evolution of vapor begins to reduce the temperature in the retort. Heat is then gently applied until the retort reaches 80° and, as the rate of vapor evolution again decreases, is gradually raised to 130°. When the acid flow ceases the pump is shut off and the heat raised to facilitate running of the niter cake through the bottom spout W. An excellent quality of acid (XoO3 = .05 per cent) is produced, about 80 per cent averaging 96 per cent HNO3, or the whole output averaging 89 per cent if weak acid is returned with the sulphuric to the retort. The niter cake produced is of excellent quality. The statements found in the literature that " perfectly pure nitric monohydrate . iif k^^^ Fig. 51. 1HXO3) produced by this process is now found in commerce," is, however, an exaggeration, although the writer regards the process as one of the best on the market to-day. Common Process. By far the greater proportion of nitric acid, however, is made by the simple action of sulphuric acid on the nitrate of soda at substantially atmospheric pressure. This reaction is generally carried out in ordinary cast-iron retorts either of cylindrical pattern horizontally placed, or of the general shape of deep pots. The former is illustrated in Fig. 51, in which A is the brick setting properly provided with buckstays B. Through this setting extend cast-iron cylinders C provided at either end with a closing plate D consisting of either cut stone or cast iron. One of these plates, generally the one above the firing door, is provided with two holes. The smaller hole E serves for the introduction of the acid and the larger hole F for the charging with nitrate of soda, after which it is closed either by a luted 98 ELEMENTS OF INDUSTRIAL CHEMISTRY cover or by a screw plate. The plate on the opposite end is provided with holes G into which the exit pipe for gases is luted and H for tapping off niter cake. These cylinders vary from 3 ft. in diameter, 5 ft. in length, to 5 ft. in diameter and 10 ft. in length, sometimes the diameter being as great as 5 ft. 6 ins. The charges of nitrate of soda are 700 to 2200 lbs. It will be noted that a relatively small grate area and a single fire is used and much of the success of the operation in yield, quality and speed depends on its careful manipulation. According to the older practice only a slight excess of sulphuric acid was used and the niter cake remain- ing behind was consequently so hard that it was necessary to get into the still and dig it out. Modern practice, which to a very large extent utilizes the niter cake for other manufacture, permits 33 to 36 per cent excess of sulphuric to remain in the Fig. 52. Fig. 53. niter cake. The end plate, generally that in the rear, is pro- vided with a hole at the bottom for withdrawing the niter cake, this hole generally being closed by an iron peg or tap loosely ground in and sometimes held in place by a screw handle. Pot Still. Another form of still, pot-shaped in general outline, is shown in Fig. 52. The bottom, middle section and cover being cast in separate pieces to permit of separate renewal according to the wear which they have suffered. The belt and top are generally lined with brick as indicated in Fig. 53. The bottom piece is left unlined to permit the free transmission of heat and because the corrosion at this point, where there is always plenty of sulphuric, is very much less. The bottom of this pot is provided with a hole F set in a trough G, thus permitting the bi sulphate, when the charge is completed, to be run out into a pan or wagon. The gas outlet H, 3 to 6 ins. in diameter, and the charging hole I, 8 to 10 ins. diameter, are provided in the cover. NITRIC ACID 99 These sections are luted together with acid-proof cement, for which purpose " Vitrex " cement may well be used; or cement made up at the works from asbestos powder containing a little finely powdered barium sulphate, made into a thick paste with 5 per cent silicate of soda solution; or equal parts iron filings and powdered brimstone, thoroughly mixed with 4 parts of ground firebrick with as little water as will serve to make a thick putty. Charging. After completing one charge and before putting in another, the retorts are allowed to cool somewhat, as the hottest part of the operation is at the end, which temperature would be too high for initiating a new charge. The nitrate of soda charge is then dumped into the still, generally after drying if strong acid is required. The manhole plate is luted or clamped on and the sulphuric acid run in rapidly. Evolution of nitric begins before all the sulphuric acid has been added, but a light fire is started before the evolution slackens and the heat is gradually increased so as to ensure a steady flow of nitric acid. A single charge of 2200 lbs. is generally run off in one of these large size retorts in 2-4 hours, though by skillful manipulation it is possible to secure two charges in 2-i hours or at most, 27 hours. In many factories, however, it is found most satisfactory to have the still started in the morning, under the eye of the superintendent, and have no charging done at night. Distillation. The first run of the acid is generally weak, or impure or both. It is the writer's experience that to some extent this depends on the character of nitrate used and the strength of the sulphuric acid applied. Nitrates containing chloride will produce impure acid to begin with because of its contamination with nitrosyl chloride. If the charges are made in too hot a still or if the sulphuric acid is run in too rapidly, there will be considerable lower oxides in the first run of acid. Likewise, if impure nitric, recovered from the final towers of the condensation system, has been mixed with the sulphuric used for charging, most of its impurities will come over in the early stages of the reaction. The retort should not be too cold at the time of charging or the partial condensation of nitric acid on its surface will cause excessive corrosion with contamination of niter cake and early destruction of the still. The whole retort should be as nearly as possible the same temperature throughout ; therefore it is desirable to have the retort enclosed as completely as possible in the brickwork. This temperature should be very slightly above the boiling point of the nitric acid, enough above> 100 ELEMENTS OF INDUSTRIAL CHEMISTRY however, materially to warm up the charge of niter when added. The nitrate of soda is perferably dried and sulphuric acid used at approximately 93 to 95 per cent, or equivalent strength of H2SO4 after diluting with recovered nitric. Too strong sulphuric is apt to promote the formation of lower oxides by dehydration of the nitric acid. Too early an application of the fire or too rapid introduction of the sulphuric, or too high a temperature of the still are all apt to produce irregular and incomplete mixing of the* charge by distilling out too much nitric in the initial stage of the operation. When all conditions are right, a gradual and steady distillation should begin when about one-third of the sulphuric acid has been introduced and should only reach its full strength just after the last of the sulphuric has been added. Condensation. There are two general methods of carrying out the condensation of nitric acid. In the older method the condensed acid brings down with it such lower oxides and chlorine as it may carry and the product is separated into stronger or weaker fractions according to the requirements of the market and the uses to which it is to be put in the plant. This system is naturally best adapted to the production of extremely high strength acid, because of the separation of various fractions. It is necessary, however, to treat the acid thus produced in order to purify it. This is done by heating the acid and blowing out the impurities with dry air. Some of the high strength secured is lost because of the tendency of the strong nitric to distill out of the mixture. The other method consists in treating the dis- tillates from the still on the reflux condenser principle and making the heated gases, sometimes mixed with a little air, coming from the still serve the purpose of bleaching the acid, thereby produc- ing substantially the entire output of the still at a somewhat lower percentage, but all of highly bleached and purified quality so far as lower oxides and chlorine are concerned. Other systems of condensation combine, to a greater or less degree, the two different characteristics above outlined. Two such systems will be described; in the first instance to show the extreme of con- densation and subsequent purification and in the last to show the extreme of complete production and automatic bleaching by the action of the hot gases. Fig. 54 illustrates the condensing plant designed to operate under the first mentioned systems, i.e., collection and subsequent purification of the acid. The distillate from still A passes over into a first receiver B designed to catch any impurities carried NITRIC ACID 101 over by foaming or excessive violence of distillation. The acid in this receiver is, however, under normal conditions, clear, and pure enough for use along with the major portion of the pro- duction. Provision is therefore made for carrying this acid down by the pipes C and the gutters D to the general receiving reservoir after it has been examined and proved satisfactory for use. The greater portion of the gas, however, passes up through the pipe F and is condensed in coils G surrounded by water in a wooden tank, whence the condensed acid flows along with the uncondensed remainder of gas into the receivers H. Herein collects the greater portion of the condensed acid and it is not unusual to provide Fig. 54. a pair of receivers in the position H, one intended for strong and the other for weak acid. In the pipe between G and H is pro- vided a three-waj r cock so that the acid according to its strength may be separated into one or other of the receivers. Two reser- voirs E are provided for receiving the acid respectively from the two receivers H, whether it be strong or weak. After leaving the receiver H the gases pass over into a second receiver I, wherein the residual portion of suspended liquid may be collected, as also the return drips from the gas pipes leading into the recovery towers K and L. This gas line is provided with branches J' to bring the gases from the receiving tank M into which strong acid is blown from the receiver E when it is desired to bleach the 102. ELEMENTS OF INDUSTRIAL CHEMISTRY acid; also the branch J" from the receiver E to carry off any unoxidized gases that may be generated in that receiver and the branch J"' from the receiver at the top of the tower into which the stronger spraying acid is blown. The two towers K and L are connected in series, packed with coke and provided with an outlet N connected with a chimney or other source of draft. In these towers the lower oxides of nitrogen are absorbed in respec- tively stronger nitric in the tower K and water in the tower L and^ oxidized by the air which comes through the system along with these gases from various leakages, etc. The weak liquid going down the tower L passes through the pipe I into the receiver V, whence it goes into an air lift I" and is thrown up thereby into the storage tank P at the top of the other set of towers. From here a pipe p permits the exit of the air used in blowing to the atmosphere because the acid in this tower is so weak that little gas will be carried away from it. From the tank P a pipe returns the weak acid to the top of the tower L, which contains a distrib- uter to insure equal flow of acid down through the cross-section of the tower. The receiver U receives a slight but steady flow of water maintaining the acid in the system of the tower L at about 18° to 20° Be. Naturally with the addition of water absorption of gas and oxidizing of this gas into nitric acid, an excess of acid accumulates in the tank P. This excess is permitted to overflow by gravity to the pipe p' into the strong acid receiver 0, from the bottom of which a supply pipe is carried to the tower K. , From the bottom of this tower K a pipe k carries the strong tower acid into the receiver k', whence it passes into the air- lift ~k" and is elevated into the receiver 0. In this tower the stronger gas is absorbed and oxidized and a portion of the outflow from the tower K is permitted to pass out through the valve q into the receiver Q for the recovered tower acid, which will be from 35 to 40° Be. The strong acid accumulated in the receiver E is elevated by a Montejus or air lift, not shown, into the receiver M, which is the acid supply reservoir for the bleaching system. From here it is allowed to flow in a slow stream through the coil R immersed in a hot water tank and thence into the tower S, wljich is likewise immersed in a deeper hot water tank and is filled with pumice stone or coke. The temperature of the hot water in the two tanks is carefully regulated to heat the acid to approximately 80° C. and a slow stream of air is supplied to the bottom of the tower S through pipes not shown. The acid warmed up in the coil R and flowing down over the extended surface of NITRIC ACID 103 the coke or pumice in the tower S is fully exposed to this stream of warm air and thus oxidized. At the same time whatever Lower oxides of nitrogen not thus oxidized are blown out by the stream of air and with it into the coil above. This coil is connected as a reflux and is given a very small supply of water, since the object is only to condense the liquid which might be carried out with the gas. The lower oxides pass out through the coil T into the strong tower U of a separate recovery system, where they are oxidized, as were the lower oxides, from the generating plant in the tower K. Likewise a second tower B for weak acid is provided similar to the tower L. The supply of acid for U is taken from the reservoir 0, which sup- plies the other strong tower K, and the weak acid for supplying the tower V is taken from the reservoir P. The outflow lines at the bottom of the towers U and V respectively join the lines k and / respectively from the strong and weak recovery towers connected with the generating system and the same air lifts furnish a con- tinuous supply for both the decomposing and the bleaching system. After passing down through the heated tower S the acid is entirely freed from chlorine, contains less than 0.10 per cent lower oxides figured as N2O3 and is received in the jar W for test and examination, whence it is run by a pipe not shown into the final receiver for bleached acid X. This system will seem to be somewhat complicated, but it is found to be thor- oughly efficient and lends itself readily to careful control to the quality of acid at various points. Some of the larger manufac- turers of strong nitric, for use in making mixed acid, both in this country and abroad, use this system with great success. Skoglund Condenser. In most nitric acid plants the aim is to combine the condensation and bleaching into a single step, by doing the condensation at such a temperature that as little of the lower oxides of nitrogen shall be condensed with the acid as passible and that in the second place what little is condensed shall be supplied with sufficient hot air to carry out its oxidation at once and produce in a single step a water-white acid of high strength. The simplest, and in the writer's opinion the most efficient apparatus for this purpose is the condenser system of Skoglund, see Fig. 55. It is characterized by the carrying out of this preliminary condensation and bleaching action in a tower somewhat similar to, though smaller in size, than the final towers used for the oxidation of lower oxides that cannot be condensed. From the still A the gases pass over in the usual manner into a 104 ELEMENTS OF INDUSTRIAL CHEMISTRY Fig. 55. tourille or jar B, serving as a sort of safety bottle to catch any suspended matter that may be carried over when the still foams. From here they pass through a pipe C into a special injector pipe D, which is arranged to be served with compressed air and thence into the bottom of the tower F. This tower is filled with lumps of quartz, through which the hot gases mixed with air pass upward, while the acid, after condensation, flows downward. From the top of the tower the gases pass through a condenser, which is generally a water-cooled coil. In this figure it is shown as an air-cooled series of pipes G, which may, however, be water cooled if desired by covering each with a piece of linen and trickling water down upon them from above. The purpose of the linen is to distribute the film of water equally over the surface of the pipes and not permit it to flow through certain lines caused by salt deposits, thus producing irregular cooling and consequent breakage of the pipes. From this condenser the gases pass over by a pipe F to the bottom of the tower H and thence through the tower H', both of which are similar to the final towers in either of the other systems described. The acid produced in the condenser G flows downward through the tower, entering it at almost the boiling point, which temperature is maintained throughout its entire flow over the surface of the quartz. Accumulating at the bottom of the tower, the acid then flows out through the pipe I into the small jar or tourille J, whence it flows through the cooling worm K, out of the top of this worm through the overflow L and into the final storage jar M. Similar storage jars are provided for the acid from the towers G and H so that it may be returned with the sulphuric acid into the still A. Through the center mouthpiece of the jar J another hot-air pipe is carried to the bottom of the acid in J and the large mouthpiece of J is connected with a similar inlet to the tower so that instead of using the injector through the pipe D air is pref- NITRIC ACID 105 erably blown through the hot acid collected in the jar J and the gases thus removed carried back into the tower. In order to maintain this tower at a high temperature it is customary to connect three or four stills charged in rotation to a single tower. Either the bottom of the tower is provided with inlets on three or four sides, or else a common gas main is employed, into which the injectors are connected. The jar B is asbestos-covered but it cools down considerably after each charge and serves as a sort of preliminary condenser to catch the first weaker acid that comes over when the still is charged. In some cases this acid is added to the condenser acid at the top of the tower by means of a specially provided neck, but generally it is mixed with the sulphuric acid and the weaker acid from the final towers H and H', the whole being returned to the still with the nitrated soda of the succeeding charge. Using moderately dry (not spe- cially dried) nitrate of soda and 98 or 99 per cent sulphuric diluted with the weak nitric acid to a strength of approximately 93 per cent H2SO4, the average output from this plant is from 89 to 90 per cent in strength, perfectly water-white and substantially free from chlorine. The operation is conducted under a slight suction. As the tower E is carefully jacketed with insulating material so as to maintain its high temperature and protect it from contact with the cold air, and the pipes C and D are also carefully jacketed, there is practically no risk of breakage except of the air-cooled pipes G. This breakage is as small as can be credited to any form of nitric condensation. CHAPTER VI ELEMENTS AND INORGANIC COMPOUNDS ALUMINIUM. This is one of the most important of the ele- ments. It occurs in nature in the form of hydrated oxides such as bauxite, diaspore, and hydrargillite; and as silicate such as common clay, kaolin, feldspar, and cryolite. It was first prepared in a free state by Wohler in 1827, who heated to redness a mixture of aluminium chloride and metallic potassium. Many attempts were made to produce the metal electrolytically, but the processes were not successful in America until 1890, when Hall took out his patents on the electrolysis of fused alumina in the presence of a fluoride. Aluminium is a silvery white metal having a specific gravity of 2.7. Its lightness and resistance to atmospheric influences have brought it into use for a variety of purposes where great strength and low weight are desirable. One of its important applications is in the manufacture of thermite, a material consist- ing of a mixture of iron oxide and powdered aluminium. This mixtuie when ignited produces a very intense heat, causes a reduction of the iron oxide and is applied in the welding of steel and in foundry processes. Alloyed with other metals aluminium gives a very valuable series of bronzes. ALUMINIUM OXIDE. The oxide of aluminium is of commer- cial importance in the form of corundum, emery, ruby, and sapphire, as well as a raw material for making metallic aluminium. ALUMINIUM ACETATE. This compound usually is found on the market in a liquid condition known as " red liquor." It may be prepared either by acting upon aluminium hydroxide with acetic acid, or by double decomposition of aluminium sulphate with calcium acetate. It is principally used as a mordant in dyeing and printing and in the water-proofing of tissues. ALUMINIUM CHLORIDE. This compound is prepared by passing dry hydrochloric acid gas over heated metallic aluminium, or by heating a mixture of aluminium oxide and carbon in the presence of chlorine. The chloride distills off as a white crystal- 106 ELEMENTS AND INORGANIC COMPOUNDS 107 line mass, which fumes in the air and boils at 183° C. Its princi- pal use is in the manufacture of organic compounds by the Friedel and Craft reaction. Its acid solution is sometimes used as a disinfectant. Aluminium Hydroxide. This product is obtained as a gelatinous precipitate on treating salts of aluminium with alka- line hydroxides or carbonates. On a commercial scale it is usually prepared by the Lowig process, which consists in treat- ing sodium aluminate with milk of lime. By this process sodium hydroxide and calcium aluminate are produced. The calcium aluminate is then dissolved in hydrochloric acid and to the alumin- ium so formed is added a calculated amount of the calcium aluminate. As, a result aluminium hydroxide is completely precipitated. The freshly prepared aluminium hydroxide is employed to precipitate many of the dyestuffs from their solu- tions, thus forming insoluble colors known as lakes. ALUMINIUM NITRIDE. Recently a new carrier of nitrogen has attracted a great deal of attention. If alumina is heated with carbon in the presence of nitrogen to about 1900° C.j A1X is formed. This nitride when treated in an autoclave with caustic soda forms sodium aluminate and ammonia, serving both as a means of obtaining a pure alumina for the aluminium industry and for the fixation of nitrogen. Unfortunately the difficulty of obtaining furnaces of the required life are so great as to preclude any present successful solution of this process of fixing nitrogen, though much effort and money is being expended in the attempt. Aluminium Sulphate. The sulphate of aluminium AI2 >04^3. I8H2O is prepared from clay, bauxite or from the aluminium oxide obtained in the manufacture of soda by the cryolite process. The calcined clay is finely pulverized and treated with sulphuric acid (sp.gr. 1.47). The mixture is heated to start the reaction, which soon becomes violent. At the end of the reaction a hard cake remains (alum cake), which contains the silica, iron and other impurities. From bauxite, it is pre- pared by adding enough sodium carbonate to the finely powdered mineral to form a mixture containing 1.2 molecules of sodium carbonate for every molecule of aluminium oxide. The mass, after fusion, is rapidly lixiviated and the solution of sodium aluminate thus obtained is filtered, concentrated to 35° Be. and treated with a current of carbon dioxide which precipitates the AI2O3 in a granular form. This precipitated oxide on dissolv- 108 ELEMENTS OF INDUSTRIAL CHEMISTRY ing in sulphuric acid produces a sulphate which contains not over .02 per cent of Fe2C>3. The aluminium oxide obtained in the cryolite process when dissolved in sulphuric acid produces a very pure form of aluminium sulphate. ALUM. Alums have the general formula M /// 2 (S0 4 ) 3 , M , 2S0 4 24H 2 0. POTASH ALUM. Potassium aluminium sulphate, A1 2 (S04)3, K2SO4, 24H 2 0, is obtained from alunite or alumstone, which is mostly found near Rome. The mineral is calcined at a moderate heat (about 500° C), exposed, when moist, to the atmosphere for 3 or 4 mouths, and then lixiviated. The alum obtained by the evaporation of the wash waters contains a small amount of basic aluminium sulphate and crystallizes in cubes called Roman or cubical alum. Alum may be obtained from alum schists or slates by roasting and subsequent exposure to the air. The iron sulphide present is oxidized to sulphate and sulphuric acid. This latter reacts on the aluminium silicate, forming sulphate of aluminium. The ferric sulphate formed attacks the aluminium compounds, pro- ducing aluminium sulphate and basic ferric sulphate. The mass is washed and the solution evaporated to 40° Be. Most of the iron compounds crystallize out, and are separated. The proper amount of potassium sulphate in concentrated solution is now added when the alum begins to separate. The crystalline product obtained still contains some iron and must be purified by recrystallization. Alum may be readily obtained b}^ adding the proper amount of potassium sulphate to a concentrated solution of aluminium sulphate and allowing it to crystallize out. Sodium and Ammonium Alums. These alums may be obtained by using sodium or ammonium sulphate in place of potassium sulphate. These products all have nearly the same chemical and physical properties, being colorless, soluble salts which crystallize in octahedra. AMMONIA. When animal matter undergoes decomposition more or less ammonia is produced. It is also formed when nitrogenous organic substances are subjected to destructive dis- tillation. By means of the latter process, during the distillation of coal for the production of illuminating gas and coke, most of the ammonia of commerce is produced. To a limited extent ammonia is also obtained from the distillation of bones and other ELEMENTS AND INORGANIC COMPOUNDS 109 animal matter, from putrid urine, sugar residues, and from waste furnace gas. The nitrogen in the ammoniacal liquor of the gas works is present in the form of free ammonia, ammonia combined as carbonate, sulphide, sulphydrate, sulphite, sulphocyanide and ferro-cyanide. As the liquor comes from the hydraulic main, the scrubbers and condensers, it is mixed with a large amount of tarry matter, which, on standing, settles out, leaving a fairly clear liquid which may be treated for its ammonia content. There are various methods employed for recovering the ammonia, but the one in common use is that in which the Feldman apparatus is employed: The settled gas liquor passes by means of a series of narrow tubes through a cylindrical chamber, where it becomes somewhat heated from the waste gases passing through this chamber, which is known as the " economizer." The heated liquor is then forced to the top of a tall tower, where it meets a current of steam which causes volatile ammonia com-, pounds to be liberated. The non-volatile compounds flow down the tower and coming into contact with boiling lime water free ammonia is produced. The free and volatile ammonia com- pounds are next caused to pass through a large pipe into the absorption vessel containing sulphuric acid. Here the sulphides and other volatile salts of ammonia are decomposed with the formation of ammonium sulphate and the liberation of hydrogen sulphide and carbon dioxide. These hot gases so formed are collected in the dome over the absorption vessel and from there pass into the shell of the economizer, producing the heat referred to above. The waste sludge from the lime treatment is drawn off from time to time and the liquor in the absorption vessel con- centrated as it becomes saturated, being sold as crude ammonium sulphate. On recrystallizing the crude ammonium sulphate and redis- tilling with lime, a pure gas is obtained which, being absorbed in water, forms the " aqua ammonia " of commerce, or the ammo- nium hydroxide of the laboratory. By subjecting ammonia gas to high pressure it is possible to convert it into a liquid. Liquid ammonia has extensive application at present, being used for producing cold in ice machines. Ammonium Carbonate. The commercial product is pre- paid by heating a mixture of the sulphate of ammonia and powdered calcium carbonate in iron retorts and collecting the sublimate formed in lead-lined chambers. The product thus 110 ELEMENTS OF INDUSTRIAL CHEMISTRY obtained is a mixture of ammonium bicarbonate and ammonium carbamate. AMMONIUM CHLORIDE. This compound is manufactured either by absorbing the gas in dilute hydrochloric acid, or by neutralizing the gas liquor directly with the acid. In either case the resulting solution is evaporated to obtain the crystals, which is then purified by recrystallization or sublimation. Ammonium chloride is usually purified, however, by sublimation, in which case it is heated in iron or earthenware pots provided with a dome- shaped cover. The purified product collects in the dome as a thick crystalline cake which is removed and placed on the market as sal-ammoniac. Formerly this salt was made by burning dried camel's clung, but at present it is all prepared from gas liquor. Ammonium chloride is used in soldering, in the manufacture of dyestuffs, and in calico printing. It also has extensive appli- cation in electrical appliances. AMMONIUM NITRATE. This salt is prepared in a manner similar to that employed in making the chloride, except that it cannot be purified by sublimation. Its chief uses are in the manufacture of explosives and for making nitrous oxide, so-called laughing gas. AMMONIUM SULPHATE. The crude salt is dark brown in color and is prepared as described under ammonia. Its chief use is as a base for making other ammonia salts, and in the impure form for the manufacture of fertilizer. When purified it gives a white crystalline product used for fire-proofing fabrics as well as for other purposes. ANTIMONY. This element occurs in nature as the sulphide Sb2S3, known as stibnite. The antimony sulphide is first sepa- rated from the gangue by heating in a furnace with sloping floor along which the fused sulphide flows in a channel. This sulphide is then placed in a reverberatory furnace, when it is converted into the oxide. The oxide is heated in a crucible, when on cooling the metal settles to the- bottom. The metal has become very important owing to its application in many metallic alloys, such as hard lead and type metal. Antimony Fluoride. The compound SbF 3 is prepared by dissolving antimony oxide in hydrofluoric acid. This salt readily forms double compounds with alkaline sulphates and chlorides. (NH^SCU, SbFs is an example of these double salts and is one of the important mordants. The double fluoride of ammonium and antimony, 8SbF3, 2NEUF, is a useful salt, ELEMENTS AND INORGANIC COMPOUNDS 111 These compounds are used as mordants, and have, to a great extent, replaced tartar emetic. ARGON. This element occurs in the air to the extent of 0.935 per cent. It can be prepared by passing atmospheric nitrogen, free from oxygen and moisture, over red-hot magnesium ribbon: magnesium nitride is thus formed, while the argon does not combine. ARSENIC. This metal occurs in nature usually in the form of sulphide, such as realgar, orpiment, smalt, and arsenical pyrites. It is obtained from the pyrites by heating it away from the air, when the arsenic sublimes, leaving the iron sulphide behind. ARSENIOUS OXIDE. White arsenic, As 2 3j is obtained by roasting arsenical minerals, such as mispickel, FeAsS, cobalt ite, CoAsSj smaltite, CoAso, and other minerals containing arsenic. By far, however, the greater amount of arsenious oxide is obtained as a by-product in the smelting of ores containing this element in small quantities. The roasting is carried on in reverberatory furnaces with free access of air and the sublimed arsenic trioxide condensed in suitable chambers. It is purified by resublimation and collected as a white powder. By resublimation under pres- sure it is obtained in a vitreous variety known as arsenic glass. It is usually ground to a fine powder, which is slightly soluble in water. It is principally used as an antiseptic for preserving- hides: it also finds application in glass manufacture, and its glycerine solution is used in calico printing. ARSENIC ACID. By oxidizing arsenic trioxide with nitric acid the compound HsAsO^ is obtained as a thick syrupy liquid. SODIUM ARSENATE. By fusing together a mixture of arsenic trioxide and sodium nitrate the compound Na2HAs04 is obtained. BARIUM. This element occurs in nature in the form of heavy spar or barytes and as witherite. It is prepared by heating the oxide with magnesium. It has a metallic appearance with a yellowish tint. As a metal it has no practical application. BARIUM OXIDE. This compound can be prepared by heat- ing the nitrate or hydroxide to a dull red beat: It is manufac- tured commercially, however, by heating a mixture of barium sulphate and carbon in the electric furnace. BARIUM PEROXIDE. This is prepared from the oxide by heating to 500° C. in the presence of air. At a higher tempera- ture oxygen is again eliminated. It is used in the manufacture of oxygen and hydrogen peroxide. 112 ELEMENTS OF INDUSTRIAL CHEMISTRY BARIUM HYDROXIDE. This compound is formed when the oxide is treated with water, in which it is soluble, forming a strongly alkaline solution. It is used for the extraction of sugar from molasses and to some extent in the softening of water. BARIUM CARBONATE. Barium carbonate occurs in nature as the mineral witherite. It is used as a raw material in making other barium compounds. < BARIUM CHLORIDE. By treating witherite with hydrochloric acid the compound BaCl22H20 is produced. Commercially barium chloride is obtained from barytes. The mineral is heated in a closed furnace in the presence of carbon and the resulting barium sulphide treated with a solution of sodium carbonate. The products of the reaction are barium carbonate and sodium sulphide, from which the chloride may be easily prepared. In some cases the barium sulphide is directly converted to the chloride by means of hydrochloric acid. It is used for the pre- vention of boiler scale, for the manufacture of blanc-fix and in the preparation of certain color lakes. BARIUM NITRATE. Witherite when dissolved in dilute nitric acid gives this compound. On a large scale it is prepared by double decomposition of barium chloride and sodium nitrate. It is used commercially to some extent for making peroxide and in the manufacture of fireworks to obtain a green flame. BARIUM SULPHATE. This compound is found in nature as barytes or heavy spar. The mineral is ground to a fine powder and used in the manufacture of paints. When produced arti- ficially, however, it gives a pigment of finer texture known as blanc-fix. The natural sulphate when heated with carbon is reduced to a sulphide which on dissolving in water and adding to a solution of zinc sulphate produces the product known as lithophone. BISMUTH. This element occurs in the native state also as the oxide and sulphide. , The ores are smelted in the presence of iron, which acts as a desulphurizing agent. The pure metal has a lustrous appearance like antimony, but may be distinguished from it by a reddish reflex. Bismuth forms easily fusible alloys used in making valves, wires, etc., for safety devices on boiler valves, fire doors and fusible plugs. BISMUTH NITRATE. This is obtained as a crystalline com- pound containing five molecules of water, when the metal is dis- solved in nitric acid and evaporated. It is easily soluble in & ELEMENTS AND INORGANIC COMPOUNDS 113 small quantity of water, but when a large amount of water is used the subnitrate is produced. BORON. This element occurs in nature in boric acid and borax. It is obtained by reduction as a brown amorphous powder. BORIC ACID. This compound, also known as boracic acid, is found in the steam which issues from fissures in the earth in the vicinity of volcanoes. The steam is condensed in reservoirs of water built around the points from which it issues. When the water has become fairly well saturated it is allowed J;o settle and then transferred to lead-lined tanks, where it is concentrated to a specific gravity of 1.08. The boric acid which crystallizes is usually purified by recrystallization. Some boric acid is obtained by decomposition of borax with hydrochloric acid. It is a color- less crystalline solid, slightly soluble in cold water, but readily soluble in hot water. It is used as a flux, in fusible glazes, in special optical glass, and as an antiseptic and preservative. BORAX. Sodiimi tetraborate may be prepared by neutral- izing boric acid with sodium carbonate. The chief source of borax, however, is from the natural deposits of Thibet, and from the crude borax of California. Crude borax is purified by slow recrystallization. Commercially borax is prepared on quite a large scale by boiling Colemanite (Ca2BeOn -5H20) with sodium carbonate and sodium bicarbonate. The most common form is the prismatic Na^B^tOz, IOH2O, which effloresces in the air and melts in its water of crystallization, becoming anhydrous at a red heat. Borax is used as a flux, in glass and enamel making, in the manufacture of soap and as a preservative. BROMINE. Bromine is manufactured from the bromides of the alkali and alkali-earth metals. These salts do not occur in nature in quantity in high concentration and are always associ- ated with large quantities of chlorides. The bromides accumulate in the mother liquors from which the chlorides have been extracted. Such mother liquors serve as the chief raw material of the bro- mine industry. The principal sources are the mother liquors of various salt wells in the United States (Michigan and Natrona, Pa.), and mother liquors from the manufacture of Carnallite at Stassfurt, Germany. The Carnallite mother liquors contain about ^% bromine in the form of magnesium bromide. The concentration of the American mother liquors is higher and has enabled the American producers to wrest a considerable share of the world's 114 ELEMENTS OF INDUSTRIAL CHEMISTRY market from their foreign competitors who at one time enjoyed a practical monopoly. From such mother liquors bromine is liberated either by the action of chlorine or by direct electrolysis. The former method (Process of Dow, etc.) is simpler and probably cheaper and better. It depends upon the simple reaction MgBr 2 + Cl 2 - MgCl 2 +Br 2 . The mother liquor containing bromide is caused to meet a stream of chlorine on the counter current principle in a stoneware tower, which may be of the Lunge plate tower type or filled with stoneware balls to increase the surface of contact. The amount of chlorine is regulated so that practically all is used up in the liberation of bromine so that the secondary formation of bromine chloride is minimized. A large part of the liberated bromine remains dissolved in the liquor flowing from the reaction tower. It is collected in granite wells and heated to boiling with live steam which expels the bromine. This is condensed in stoneware worms. The crude bromine contains about 2 to 4 per cent chlorine. The chlorine may be removed by treating with ferrous bromide solution and redistilling, the chlorine being held back as ferrous chloride. The crude bromine may also be purified by being heated very slowly to a point just below the boiling point of bromine and held at this temperature (59° C.) for thirty- six to forty hoars. The electrolytic processes depend upon the fact that bromides decompose at a lower voltage than chlorides and hence are first decomposed. Diaphragm cells are used. Owing to the low con- centration and the large bulk of liquid to be handled the effi- ciency is low. In the processes depending on displacements by chlorine, the chlorine may be generated within the liquor by the action of muriatic acid on manganese dioxide, but the use of externally generated chlorine is simpler and gives a better control of the process. Bromine is used in metallurgy (bromo-cyanogen process), in the manufacture of bromides for use in pharmacy and the photo- graphic industries, and also as a disinfectant. CADMIUM. This element usually accompanies zinc in its ores. It is easily separated, as it distills off before the zinc. It FeOtC =Fe + CO (Complete) *'* (8) CaCOj = CaO*C0 2 I850°(4) CtCOi -200 (Prey a, is) SO ZOSO? go ino'F.) 'iilo'tA (9)5I0 2 +2C = 5/ t2C0 (10) FeS i-CaOtC* CaS tFetCO (//> Mn0 2 t2C = Mn + ZCO 02)P 2 2 tSC - 2P + 5C0 Fig. 65. to the top of the bosh (see Fig. 66), and above this are alternate layers of coke and iron ore, together with an appropriate flux, which is generally limestone. The preheated air, at a temperature of usually 800 to 1200° F. 425 to 650° C.) and at a pressure of about 15 lbs. per square inch, enters through the tuyere pipes at the top of the hearth, combines with the fuel and creates a volume of intensely hot reducing gases, which pass up through the interstices of the charge, melting, heating and reducing the ore which it meets and finally passing out at the throat of the furnace. The tempera- 142 ELEMENTS OF INDUSTEIAL CHEMISTEY tures at different points in the furnace and the various reactions which take place are shown in a general way in Fig. 65. Below the top of the bosh the fuel is the only material not in liquid form. The iron, containing about 3.50 to 4.50 per cent of carbon and varying amounts of silicon, sulphur and other elements, according to the reactions of the smelting zone, collects in the bot- tom of the hearth, and on top of it the cinder, consisting of the impurities in the ore together with the ash of the coke and the lime, magnesia and impurities of the flux. All sulphur which is brought to the condition of CaS goes into the cin- der, and all that in the form of « FeS goes into the iron. With this exception the cinder contains all the oxidized materials and the metal all those in reduced condition. The cinder, because of its low specific gravity, floats on top of the metal and is drawn off about fifteen times in twenty- four hours and dis- posed of. The metal is tapped out of the bottom of the furnace about every six hours and is either cast in the form of pigs (Fig. 67) or transported to a nearby steel mill in the liquid form. Because of its impurity and therefore its friability, pig iron cannot be worked or wrought. Many millions of tons per year are used in the form of iron cast- ings, and the remainder purified. The purification consists in oxidizing the carbon, silicon and some other impurities. Electric Iron and Steel. Electricity may be used as a source of heat in the smelting of either iron or steel, and in localities remote from fuel supply and adjacent to other cheap sources of power, experiments of this nature have been made with commer- cial success. They have excited a great deal of interest, although the volume of production has not yet attained relative importance. It is 'believed, however, that electric smelting will give a cheaper, and a higher grade of steel than the crucible process, and impor- tant developments in this field have already begun. Electric furnaces are also the only means of producing some of the " ferro- Lcgcod i -^ Lumps o Layer of Molten Slag. Ltjrftr oi Mofeto Ira., Fig. 66. ELEMENTS AND INORGANIC COMPOUNDS 143 alloys" because sufficient temperature cannot be otherwise obtained. FERROUS ACETATE. This is prepared by adding lead or calcium acetate to a solution of ferrous sulphate. An impure product, known as " black iron " or " iron liquor," is made by adding scrap iron to crude pyroligneous acid. Its principal use is as a mordant in leather dj^eing and in calico printing. Fig. 67. FERROUS SULPHATE. This compound, also known as cop- peras and as green vitriol, is obtained largely as a by-product from the pickle used in cleaning iron castings and iron wire. The solution of ferrous sulphate obtained is concentrated by application of heat to the surface of the liquid, which thus pre- vents oxidation. The concentrated solution is allowed to crystal- lize on wooden rods. The crystals of ferrous sulphate effloresce in the air and become more or less oxidized, basic ferric sulphate being formed. Recently the evaporation has been carried out 144 ELEMENTS OF INDUSTRIAL CHEMISTRY in multiple effect vacuum paus and the sulphate separated in a granular form by rapid cooling and agitation. It is soluble in about 1§ parts of water. Ferrous sulphate finds its most impor- tant use as a mordant, as a disinfectant, in the manufacture of ink, Prussian blue and red oxide. FERROUS SULPHIDE. On melting iron and sulphur together a black compound, FeS, results. It is used as a source of hydro- gen sulphide. FERRIC OXIDE. This compound occurs in nature in various minerals, or it may be prepared artificially by the rusting of iron. The natural product serves as an ore for the production of iron and steel and in some of its forms is of value as a pigment. The artificially prepared oxide is obtained in various shades, depending upon the method of preparation, and is used almost exclusively in the manufacture of paints. FERRIC CHLORIDE. This compound is obtained by the oxidation of ferrous chloride with nitric acid or by passing chlorine through a solution of ferrous chloride. It is used in the chlorina- tion of copper and silver and as a mordant in dyeing. Some- times it is used for the purifying of effluent water. FERRIC SULPHATE. This may be prepared by the weathering of pyrites in the presence of sulphuric acid. It may also be made by adding sulphuric acid and nitric acid to a solution of ferrous sulphate. Its principal use is as a sewage precipitant. FERRIC NITRATE. By treating scrap iron with an excess of nitric acid (sp.gr. 1.3) and evaporating the solution, colorless crystals are obtained. By adding ferric hydroxide to this solu- tion a basic nitrate is obtained. This basic nitrate is used in silk dyeing and weighting and for coloring buff on cotton. The usual form of " nitrate of iron " consists of basic sulphate of iron containing oxides of pitrogen. It is used in silk dyeing. KRYPTON. This is one of the rare elements of the atmosphere, being present to the extent of one part in one million. It has a characteristic spectrum and is noticed especially in the aurora borealis. LANTHANUM. This element occurs as a rare oxide in mon- azite. When the oxide is heated it gives off a very intense white light, which has led to its practical application, together with other rare earths, in the manufacture of gas-light mantles. LEAD. This element is found abundantly in nature as the mineral galena, and to a smaller extent in various other minerals. There are many methods in vogue for obtaining the metal, but ELEMENTS AND INOEGANIC COMPOUNDS 145 the one most commonly used in this country is to first roast the ore in a reverberatory furnace with a silica flux; the mixture of oxide and silicate thus obtained is transferred to a cupola furnace, where it is heated with coke, lime sometimes being added. The lead thus formed is drawn off from time to time and run into molds, giving the product known as pig lead. Pure lead is of a bluish-gray color, is soft and ductile. On heating in the air it readily oxidizes. It is not attacked by sulphuric acid. Nitric as well as many organic acids, however, dissolve lead very rapidly, forming lead salts, all of which are very poisonous. Lead is used very extensively in chemical technology, espe- cially for building of lead chambers and other equipment em- ployed in the manufacture of sulphuric acid. It is used for making small pipes, small shot, in storage batteries and a con- stituent of many alloys. One of its principal applications is in the manufacture of lead pigments. Lead Suboxide : Pb 2 0. This is a black powder which readily oxidizes to the higher form. LEAD OXIDE: PbO. On heating metallic lead or residues remaining from the manufacture of white lead, & reddish-yellow powder is obtained which is commercially known as litharge. This material finds extensive application as a drier in paint oils, in the manufacture of rubber goods, and as the raw material for making a large number of lead salts. LEAD DIOXIDE: Pb0 2 . This compound, also called lead peroxide, is obtained by treating red lead with nitric acid. It is used extensively as an oxidizing agent and to some extent in the manufacture of matches. MINIUM: Pb.^O^ This compound, also known as red hnch is prepared by heating litharge in a reverberatory furnace to a temperature of about 450° C. or by heating a mixture of litharge and sodium nitrate to a dull red heat. It is applied in the form of a paint as a protective coating for steel and iron structures, for painting machinery, in the manufacture of glass, and in the preparation of storage batteries. LEAD CARBONATE. This material is obtained in both the neutral and basic condition and is discussed in Chapter VIII. LEAD CHLORIDE. This is a white crystalline powder obtained by adding hydrochloric acid or sodium chloride to a soluble lead salt. LEAD NITRATE. By dissolving litharge in dilute nitric acid 146 ELEMENTS OF INDUSTRIAL CHEMISTRY and evaporating to a small volume colorless crystals of lead nitrate are produced. By treating with an excess of litharge the basic nitrate is formed. LEAD SULPHATE. This compound is formed by adding sul- phuric acid or a sulphate to a soluble lead salt. It is also dis- cussed in Chapter VIII. LEAD SULPHIDE. This compound may be prepared by adding a soluble sulphide to a lead salt. It occurs in nature as the mineral galena. LITHIUM. This metal may be obtained by electrolysis of the fused chloride. It is a soft metal with a silvery luster and hav- ing a specific gravity of 0.59 is the lightest known metal. In the form of carbonate and salicylate it is much used in medicine. MAGNESIUM. This element occurs in the minerals mag- nesite, dolomite, asbestos, talc, serpentine, and in the form of mag- nesium salts in the Stassfurt deposits as carnallite, kieserite, and kainite. It is prepared in the metallic state by electrolysis of the fused chloride and is of a silvery white color. It is ductile and malleable and when heated may be drawn into wire or ribbon. When heated in a gas flame it takes fire, burning to the oxide with a very bright light, which is rich in chemical rays. Two parts of powdered magnesium with one part of potassium chlorate gives a very intense light when brought into contact with a spark and hence finds extensive application in flashlight photography. MAGNESIUM OXIDE: MgO. This compound is obtained by heating the carbonate to a very high temperature. It is used in medicine and also as a refractory material for furnaces which are required to withstand very high temperatures. It finds application in the Nernst incandescent electric lamp, where it is mixed with oxides of some of the rare earths. Magnesium Peroxide: Mg0 2 . This product is obtained by treating a concentrated solution of magnesium sulphate with either sodium or barium peroxide. MAGNESIUM CHLORIDE. This compound is obtained from the mother liquor of the Stassfurt salts and in this country from the salt brines of Michigan by evaporating to about 42° Be. The crystals which separate consist of about 80 per cent of MgCl2, 6H2O. It is used as a filler for cotton and woolen goods and in the preparation of magnesia cements. These cements, which are very hard, are known under various trade names, but ELEMENTS AND INORGANIC COMPOUNDS 147 they nearly all consist of a mixture of magnesium chloride, saw- dust, and magnesium oxide. Magnesium Sulphate. Epsom salts is found in many mineral springs, but the most important source is Kieserite (MgSO.±, H2O), which is quite insoluble in water, but on standing in contact with water for some time it undergoes solution, becom- ing MgS04, 7H2O. It is also prepared from kainite (K2SO4, MgSC>4, MgCL?, 6H2O), and is easily obtained by action of sulphuric acid on the natural carbonate, magnesite. It is a colorless crystalline salt, readily soluble in water and efflorescent in dry air. It loses all of its water of crystallization at about 230° C. Magnesium sulphate is used in medicine under the name of Epsom salts.* in the finishing of cotton fabrics and for weighting paper, silk and leather. MANGANESE. Tliis element does not occur free in nature, but is widely distributed in the form of ores, the principal one being pyrolusite. In the metallic condition it is obtained by the Goldschmidt process as a gray lustrous material. As ferro-man- ganese (spiegel) it is used in metallurgy; and in some of its compounds has quite an extensive application in the drying of oils. MANGANESE DIOXIDE. This compound is found in nature iii the mineral pyrolusite. Dissolved in cold hydrochloric acid it forms the chloride MnCU, which on heating breaks down into the chloride MnCU and CI2. This reaction is the foundation of the Weld on process for the manufacture of chlorine, which has already been described. The oxide is used for many other pur- poses, among which might be mentioned the manufacture of oxygen. ' MANGANOUS SULPHATE. This compound is obtained by dissolving the carbonate in sulphuric acid. It is used in dyeing and for painting on porcelain. POTASSIUM PERMANGANATE. This compound is prepared by mixing together potassium hydroxide in solution with man- ganese dioxide and potassium chlorate, boiling vigorously and evaporating to a paste. The paste is then heated in a crucible to the point of fusion, dissolved in water and oxidized with chlorine or ozone. It is stated on good authority that the oxida- tion i< also brought about electrolytically. The permanganate illizes from the concentrated solution in metallic-looking crystals. It is fairly soluble in water, giving a purple color. It 148 ELEMENTS OF INDUSTRIAL CHEMISTRY is a strong oxidizing agent for organic and inorganic substances. It is used for bleaching vegetable fibers and for purifying various gases. MERCURY. This is the only metal which is liquid at ordinary temperatures. It is found to a slight extent in the free condition, but is obtained almost exclusively from cinnabar. From this mineral, which is the sulphide HgS, it is prepared by distilling in a free supply of air; when the mercury distills over and is condensed while the sulphur burns to sulphur dioxide. Mercury is a silvery white liquid having a specific gravity of 13.6. It has the property of combining with nearly all of the metals except iron, thereby forming amalgams which have varied and extensive applications. The mercury-vapor electric lamp of Bastian has recently found quite an extensive application. The lamp consists of a long tube placed horizontally and contains a small quantity of mercury. At each end of the tube, which is under high vacuum, is an electrode. By passing a current through the mercury it becomes vaporized; the vapor thus acting as a conductor gives off a very intense light. The largest amount of mercury is used for the extraction of gold and silver, but a certain amount is also required for chemical and physical appara- tus. Mercury forms both mercurous and mercuric compounds. MERCUROUS OXIDE: Hg 2 0. This compound is obtained by treating a mercurous salt with sodium hydroxide. It is of a dark brown color and readily decomposes when exposed to light. MERCURIC OXIDE: HgO. This oxide is produced by heat- ing mercuric nitrate and mercury in an iron crucible. It is of a bright red color and known sometimes as red precipitate. Mercurous Chloride. This compound, also known as calomel, is prepared by heating a mixture of 4 parts of mercuric chloride with 3 parts of metallic mercury. It is heated in an iron pot until a white mass is formed ; the temperature is then raised when the mercurous chloride sublimes. It is then further puri- fied by washing. MERCUROUS NITRATE. This is obtained by dissolving mercury in warm nitric acid, having an excess of mercury always present. Mercurous Sulphate. This compound is formed by the action of concentrated sulphuric acid on an excess of mercury. It is a crystalline product and only slightly soluble in water. MERCURIC CHLORIDE. This compound, also known as corrosive sublimate, is obtained by subliming a mixture of mercuric ELEMENTS AND INORGANIC COMPOUNDS 149 sulphate and sodium chloride in the presence of a small quantity of manganese dioxide. It may also be prepared by dissolving mercuric oxide in hydrochloric acid. Commercially, however, it is made by heating mercury in the presence of chlorine gas. Being a violent poison it should be handled with great care. In very dilute solutions it is applied as an antiseptic for medicinal purposes; while on an industrial scale it is used for impregnating timber. MOLYBDENUM, This element occurs principally in the mineral molybdenite, from which the oxide M0O2 is obtained by roasting. The metal is obtained by heating the oxide with carbon in a stream of hydrogen in the electric furnace. Thus prepared it is a gray powder w T hich on fusing becomes silvery in appearance. The metal is used in manufacture of some of the hard steels and the oxide is used in the preparation of molybdates. NEODYMIUM. This is one of the rare earths and has no practical application. NEON. This is one of the rare elements and occurs in the atmosphere. NICKEL. This metal occurs principally in the mineral garnierite, 2(XiMg)SUOi2-2H20, from which it is extracted by heating with coke and a basic flux, subsequently puddling in an open-hearth furnace with hot air to separate the iron, manganese, and silicon. The crude nickel formed by this or other methods constitutes what is known as nickel matte and is purified by elec- trolytic means. Pure nickel has a silvery appearance, is ductile and slightly magnetic. It remains unchanged in the air and consequently is used in many alloys such as nickel coins and German siber. It is also much used for electroplating iron, in the manufacture of various utensils, for making nickel-steel and armor-plate. In the finely divided condition it is employed as a catalytic agent. NICKEL SULPHATE. This compound is produced by dissolv- ing nickel in sulphuric acid, forming bright emerald-green crystals. It i< used as an electrolyte in electroplating. NITROGEN. This element is found free in nature in the atmosphere, of which it forms about four-fifths. But in this case some argon and other rare elements may be obtained from the air by removing the oxygen present. It is also found in abundance in ammonia salts, nitrates, and in many organic substances. By heating a mixture of sodium nitrite and ammo- nium chloride pure nitrogen may be obtained. 150 ELEMENTS OF INDTJSTKIAL CHEMISTEY Formerly nitrogen was thought to be one of the most inert of the elements. At present, however, this idea has been greatly modified, as we now have many compounds which are formed by direct union with the element. The application of nitrogen in the form of some of its com- pounds is a very vital factor in the production of crops. As the natural supply of nitrates and ammonia are becoming limited we have had to devise ways and means for obtaining this much- needed element from its inexhaustible source, the atmosphere. Fixation of Nitrogen. The passage of a current of air through an electric arc causes the combination of the nitrogen and the oxygen to form one of the oxides of nitrogen, which may readily be converted into nitric acid or into a salt of this acid. But one commercial plant is at present in operation for the manufacture of this acid from air. This is in Norway, and uses the Birkeland- Eyde apparatus. An arc is sprung between special terminals of an alternating-current circuit and forced to take a broad flat form by means of suitable electromagnets. Through this arc the air is passed, the temperature of the flame being 2500-3000° C. By suitable regenerative systems the gases, containing only 30-40 milligrams of combined nitrogen as NO per liter, are cooled to 1000° C. and pass thence through boilers for further cooling, the steam from the boilers being used for evaporation of the final products. From the boilers the gases pass into alum- inium coolers and thence to oxidation tanks — iron vessels lined with acid-proof stone. Here the NO formed in the arc is further oxidized and passes to absorption towers, where the nitric oxides are absorbed in water. The last tower of the series is fed with caustic soda in order to catch the last traces of the nitric oxide. The final solution contains 30 volume per cent of nitric acid, and the towers absorb over 98 per cent of all nitrous gases produced. Besides nitric acid and nitrate of soda the Norwegian Plant also produces a basic nitrate of calcium, used in the fertilizer industry, which is made by treating calcium carbonate with nitric acid, and evaporating the product to dryness. About 60,000 horse-power is being utilized in this industry, individual furnaces up to 3000 horse-power being in operation. The yield in the process is estimated to be about 600 kilograms of HNO3 per kilowatt-year. Cyanamide. Nitrogen is absorbed by hot calcium carbide, forming what is known in the trade as cyanamide. The reac- ELEMENTS AND INORGANIC COMPOUNDS 151 tion involved in the absorption is a reversible one, reading as follows : CaC 2 +N 2 <=* CaCN 2 +C. This industry is making rapid strides, there being some fourteen plants in operation throughout the world, the bulk of the product being consumed in the fertilizer industry. Calcium carbide is first made from lime and carbon by the usual electric furnace process. This carbide is then finely ground and the powdered material charged into a special form of electric furnace, where it is kept at 1000° C. Pure dry nitrogen, produced either by the copper oxide or the Linde process, is then passed over the hot carbide and is there absorbed. Starting with a carbide containing 75-80 per cent calcium carbide, from 80-90 per cent of the theoretical amount of nitrogen will be absorbed, the resulting product being a grayish-black mass of cyanamide, carbide and lime. It contains on the average 20 per cent nitro- gen. The American fertilizer manufacturers require that the material be freed from undecomposed carbide and free caustic lime before they can use it. The product is therefore hydrated in specially designed rotary mixing apparatus before appearing upon the market. A small quantity of mineral oil is added to assist in keeping down the dust. This hydrated oiled material is sold in the United States under the name cyanamide. OSMIUM. This is one of the rare elements and has the highest specific gravity (22.48) of any of the metals; it also has the highest melting-point and in the mass is not affected even by aqua regia. In the form of its oxide it has been suggested as an electric lamp filament, but this application has never met with commercial success. OXYGEN. Oxygen is the most abundant and important of the elements being found in the air to the extent by weight of 23 per cent, in water 89 per cent, as well as in minerals, acids, salts and as a constituent of all animal and vegetable matter. It com- bines either directly or indirectly with all elements except fluorine, helium, and argon. In the laboratory it may be prepared in various ways, thus giving a colorless, odorless gas. On an industrial scale many methods of preparation have been proposed, but of these only a few have proven of practical and of economic value. Electrolytic Oxyge n. Among the processes which have recently 152 ELEMENTS OF INDUSTEIAL CHEMISTRY come into use is that based upon the electrolysis of water in specially arranged cells. This process, it is claimed, has many advantages over the others, especially as hydrogen is generated at the same time. The equipment, however, is somewhat expen- sive and depends largely upon the cost of electrical power. It can of course be operated to greater advantage where electrical energy is readily available. Boussingault-Brin Bros. Process. In the original process barium oxide is heated to a dull redness in a current of air, which has been freed from carbon dioxide. At this temperature it ab- sorbs oxygen and becomes barium peroxide. When the reaction is completed the heat is raised to bright redness when it is dis- sociated into barium oxide and oxygen. The barium oxide can be used again and the process would be continuous if the barium oxide did not become glassy and hydrated. For this reason the process is not practical, as the reaction cannot be repeated suc- cessfully more than ten or twelve times. Thessie du Motay-Marechal Process. In this process a mixture of manganese dioxide and caustic soda is heated in a current of dry air to dull redness, sodium manganate being formed. The properly granulated mass is now heated to 450° C. in a current of steam, when the following reaction takes place : Na 2 Mn0 4 +H 2 = 2NaOH+Mn0 2 +0. To secure regularity in the reaction a small amount of cuprous oxide may be added to the mixture. As manganese dioxide and sodium hydroxide are regenerated in the second reaction the process is a continuous one. Oxygen from Liquid Air (Linde Process). The machines for the production of liquid air have been perfected so that its production has become very economical. If liquid air is allowed to evaporate the nitrogen passes off more readily than the oxygen. By use of double- walled vacuum vessels the evaporation takes place so slowly that most of the nitrogen escapes, leaving fairly pure oxygen. By this method oxygen gas containing about 10 per cent of nitro- gen may be obtained. Oxygen is used in the oxy-hydrogen blowpipe, in the manu- facture of blown oils, in the aging of liquors, in refining of glass, in medicine and in the oxy-acetylene welding process. OZONE. This peculiar form of oxygen was first observed by van Marum in 1785, who passed a current of air through an ELEMENTS AND INORGANIC COMPOUNDS 153 electric discharge. It is a colorless gas having an odor of chlorine. Under great pressure its color is blue and when liquefied it becomes a dark blue, mobile liquid with highly magnetic properties. The chemical formula is O3 and the molecular weight is 48. At ordi- nary temperatures it is relatively stable, but decomposes in contact with organic, or in general, oxidizable matter, and spon- taneously at 280° C. Ozone may be formed in various ways — viz., by chemical action, by electrolysis, by the electrostatic field, by ultra-violet rays, by radio-active elements, by incan- descent solids and by vaporization of water. Of the chemical methods, the heating of peroxides or potassium permanganate with strong sulphuric acid may be mentioned, but the production by the electrostatic field has been the only one developed com- Fig. 68. mercially . The theory of the latter is not fully understood, but it is probable that ionization by collision takes place with consequent dissociation of the oxygen, which on recombination furnishes aggre- gates of ions consisting of molecules with an attached extra atom. Machines. Ozone generators have been made in various forms. The essential principle of all is the juxtaposition of two, or a plurality of discharging surfaces so as to form a condenser with an air gap which may or may not be furnished with a dielectric element. The discharging surfaces may be smooth or armed with points, and if smooth they may be flat or curved. Ozonators without dielectrics generally possess rotating electrodes so that they are in relative motion with the aim of averting sparking which favors the formation of nitrogen oxides and the destruc- tion of ozone already formed. A representative tubular unit is shown in Fig. 68. This con- 154 ELEMENTS OF INDUSTRIAL CHEMISTRY sists of a cast-iron frame with two closed bulkheads connected together by the ozone tubes in much the same way as in a water- tube boiler. Within these tubes, which are of glass, the cylindrical high-tension electrodes are placed coaxially. The outer tubes are immersed in water, which forms the ground element, while the inner high-tension elements are connected to the circuit by means of suitable contacts on a bus bar carried into the air header through insulating bushings. The air is introduced into the rear header and passes through the tubes to the front, whence it passes into the ozone collecting pipe. PALLADIUM. This is one of the rare elements and is found to a limited extent in combination with gold. In the spongy condition it absorbs hydrogen with rapidity, producing a marked increase in temperature. Advantage is taken of this fact in pro- ducing automatic gas lighters. PHOSPHORUS. Tribasic calcium phosphate Ca 3 (P04)2 in the form of bone, bone ash and mineral phosphate is the source from which phosphorus is manufactured. The finely ground material is treated with sulphuric acid (sp.gr. 1.52) in lead-lined tanks. This converts the tricalcium phosphate into monocalcium phos- phate. The clear solution is drawn off and the precipitate thoroughly washed with hot water. The solution and washings are evaporated in leaden pans to 45° Be., about 25 per cent of coke or charcoal added and the pasty mass dried in iron pans. The dry mixture is then subjected to distillation in fireclay retorts, usually placed in two tiers. At the start of the operation the monocalcium phosphate is changed to the metaphosphate, which in the presence of carbon forms tricalcium phosphate, phosphorus and carbon monoxide. The neck of the retort is passed into a condenser containing water, under which the phosphorus col- lects. By this method about two-thirds of the phosphorus in the phosphate is set free. Electrical processes are taking the place of the older methods for the manufacture of phosphorus. A charge of the mineral phosphate, coke and sand is heated in an electric furnace and results in a yield of about 86 per cent. The crude phosphorus is purified by filtration through porous tile, chamois skin, or canvas, this operation being carried on under warm water, which keeps the phosphorus liquid. It may also be purified by melting under a warm solution of potassium dichromate and sulphuric acid. In Germany it is usually puri- fied by redistillation in iron retorts. ELEMENTS AND INORGANIC COMPOUNDS 155 Ordinary phosphorus is a vellow, wax-like solid, which melts at 44° C, has a specific gravity of 1.82, and distills at 269° C. It appears on the market in the form of sticks; which being highly inflammable, have to be kept under water. RED PHOSPHORUS. The amorphous form is prepared by heating ordinary phosphorus in closed iron pots to a temperature of 250° C. for several days, as there always remains some un- changed phosphorus which must be removed by treating the mass with boiling caustic soda or carbon disulphide. Thus obtained it is a reddish-brown substance, which only inflames in the air when heated to about 260° C. It is insoluble in water, car- bon disulphide and, unlike ordinary phosphorus, is not poisonous. Ordinary phosphorus is used in making phosphor bronze; while the red variety is used in the manufacture of safety matches. PHOSPHORIC ACID. This acid is prepared from bone ash or mineral phosphate by the action of sulphuric acid. The filtered solution is concentrated to a sirupy consistency, which contains about 85 per cent of H3PO4. If further heated it loses one molecule of water and becomes metaphosphoric acid, which is called glacial phosphoric acid. PLATINUM. This metal occurs in the natural condition as small granules of the sandy deposits of the Ural Mountains, from which it is obtained by levigation. The platinum thus obtained is mixed with some of the other rare metals, from which it is separated by aqua regia and subsequent precipitation. Pure placinum has a silvery appearance, is one of the noble metals and is not altered in the air even at elevated temperatures. It alloys with other metals and is affected by fused alkaline hydroxides, phosphorus, c} r anides, sulphides, and halogens. It is applied in many forms of chemical apparatus and is being used very exten- sively in the manufacture of jewelry. POTASSIUM. This element occurs abundantly in nature combined with various other substances. It is present in all soils and is necessary to the production of vegetable life. The principal source is from feldspar and the Stassfurt deposits. Germany controls the market of the world of the metal and its compounds. Many methods have been proposed for obtaining the compounds of this element from other sources, but up to the present time none of them has reached any commercial impor- tance. The preparation of the element is similar to that which will be given under sodium, and like sodium it forms a very extensive series of valuable compounds. 156 ELEMENTS OF INDUSTRIAL CHEMISTRY Potassium Carbonate. This compound, also known as potash and salts of tartar, is found in the ashes of wood and plants, beet-sugar residues and wool scourings, but the largest quantity is obtained from the chloride by the same methods as employed for the corresponding sodium salt. The use of potassium car- bonate is somewhat limited, especially since the introduction of the Leblanc process for the manufacture of sodium carbonate. POTASSIUM CHLORATE. If chlorine acts upon milk of lime at a high temperature (60 to 70° C), the chlorine being in excess, hypochlorite is formed only as an intermediate product, which immediately is converted to chlorate, the final reaction being 6Ca(OH)2 + 12Cl = Ca(C10 3 )2+5CaCl2+6H 2 0. This is the reaction upon which the manufacture of chlorate is based. Chlorine is systematically passed over milk of lime in cast-iron cylinders provided with stirrers, which are kept at the proper temperature mainly by the heat which the reaction itself evolves, if the combination is allowed to proceed at a suffi- ciently rapid rate. The chlorine is passed over the surface of the lime water till most of the lime has dissolved and been con- verted into chlorate. Any unabsorbed chlorine passes to another fresh cylinder in series where it is utilized. The solution is then evaporated to about 1.35 sp.gr. with potassium chloride, which reacts, forming potassium chlorate. Ca(C10 3 )2+2KCl = 2KC10 3 +CaCl 2 . On cooling the bulk of the potassium chlorate crystallizes out. The mother liquors are evaporated a second and third time and well cooled to recover the small amount of chlorate which remains in solution. The crude potassium chlorate is purified by recrystallization, and is washed and dried in a centrifugal machine. POTASSIUM CHLORIDE. This compound occurs abundantly in the Stassfurt deposits, from which it is separated by crystalliza- tion and is the chief raw material for all potassium compounds. POTASSIUM CYANIDE. By fusing potassium ferrocyanide with potassium carbonate a change takes place resulting in the formation of potassium cyanide and potassium cyanate; the latter being mostly eliminated by the addition of carbon during the reaction. ELEMENTS AND INORGANIC COMPOUNDS 157 Potassium Hydroxide. This compound, also known as caustic potash, may be prepared by adding milk of lime to a solu- tion of potassium carbonate. The industrial method in common use to-day. however, is the same as that employed for the sodium hydroxide. The principal use of this material is for the manufacture of soft and liquid soaps. POTASSIUM FERROCYANIDE. The oldest method of manu- facture consists in heating a mixture of scrap iron and potas- sium carbonate with organic materials containing nitrogen, such as horns, hoofs, hides, dried blood. The modern method is to fuse potassium carbonate in iron crucibles and add in small portions the nitrogenous material. The action is very violent, and must be conducted with care. After the reaction is com- pleted the fused mass is lixiviated to separate the ferrocyanide from the carbonaceous matter. The solution is evaporated to a sp. gr. of 1.27, when the ferrocyanide crystallizes out. As the first product is very crude, it must be subjected to recrystalliza- tion. POTASSIUM FERRICYANIDE, This is prepared by acting upon the ferrocyanide with a current of chlorine: K,Fe(CN) 6 +Cl = KCl+K 3 Fe(CN) 6 . POTASSIUM NITRATE. This compound has been known and used for hundreds of years. It is found in nature to a limited extent, but is mostly prepared from sodium nitrate by double decomposition with potassium chloride. Its principal use is in the manufacture of black gunpowder. PRASEODYMIUM. This is one of the rare elements and occurs together with the other rare earths in the monazite sands. RADIUM. For many years fluorescence and phosphorescence have been known. Some substances give off light after exposing to sunlight, but eventually lose the property when kept for some time in a dark place. Phosphorescence, as we have long known, can be produced by friction and through other causes. Recently, however, some very interesting substances have been discovered which emit heat and light without any outside stimulants; these •• radio-active " substances have been much studied during the past few years and the discoveries made have marked a wonder- ful era in the development of the science of both chemistry and physics. Becquerel in 1896 discovered that uraninite, or p>'trhblew(r, emitted radiations capable of affecting a photo- 158 ELEMENTS OF INDUSTRIAL CHEMISTRY graphic plate by rays which could not be reflected or refracted. These rays it was also learned rendered gases good conductors of electricity and converted insulating materials into conductors of the current. Becquerel attributed these properties to uranium and its compounds, but in 1898-99 Madame Curie and her husband, Professor Curie, showed that the emanat'ons were more marked in the residues from pitchblends from which the uranium had been removed. By using enormous quantities of the residues they were eventually able to separate a substance a million times more active than uranium, to which they at first gave the name of polonium, but afterwards called it radium. This original radium of the Curies has since been shown to contain other elements, but it is not within the scope of this chapter to deal with all of the interesting points which have been developed from this wonderful discovery. Radium is an element somewhat similar to barium in its chemical properties, forming salts with the mineral and organic acids. One very interesting point is that radium is supposed to be a metal in the stage of decomposition, for the emanations which are given off have been condensed and have proven to be the element helium. RHODIUM. This is one of the rare elements belonging to the platinum group. It is a silvery white metal which is insoluble even in aqua regia. It is used in the construction of electrical pyrometers. RUBIDIUM. This is one of the rare elements and occurs in lithium-bearing minerals. Its properties are somewhat similar to potassium. RUTHENIUM. This is a rare element belonging to the plat- inum group and has properties somewhat similar to that metal. SAMARIUM. This element is found in monazite, but has no commercial applications. SCANDIUM. This element occurs in the same group as samarium and is of no commercial importance. SELENIUM. This element occurs in some of the Bohemian and Swiss pyrites and is found in the dust chambers and in the mud of the lead chambers of the sulphuric acid works. The selenium is recovered by treating the dust and mud with a con- centrated solution of potassium cyanide and reprecipitating with rrydrochloric acid. The crude selenium thus obtained is oxidized with nitric acid to Se02, which is then purified by sublimation. The metal may be obtained by reducing with sulphur dioxide. ELEMENTS AND INORGANIC COMPOUNDS 159 When heated in the air selenium barns to the oxide, giving off an odor of rotten onions. The metal may be obtained in an amorphous or crystalline condition, the latter being a good con- ductor of electricity, the conductivity increasing with the illum- ination. On account of this property it finds application in wireless telegraphy and in the wireless telephone. Much research work has been conducted along applied lines, but up to the present time there are many difficulties still unsolved. The salts have been proposed as a treatment, with a certain amount of success, in some of the so-called incurable diseases. SILICON. This element does not occur in the free state, but in combination as silicon dioxide and as silicates it constitutes the bulk of the earth's crust. In the free condition it may be prepared in various ways: one being the heating of powdered silica with powdered metallic magnesium. Within recent years its commercial preparation by heating sand and carbon in the electric furnace has brought it to the front in the manufacture of chemical apparatus. WATER GLASS. Soluble glass or water glass consists of soluble silicates of sodium or potassium or a mixture of the two. It usually comes on the market as a thick sirupy liquid. In its manufacture a mixture of sand, charcoal and soda is heated together in a reverberatory furnace for eight to ten hours. The glass-like mass is broken up and boiled with water. The solu- tion obtained is filtered and concentrated to the proper con- sistency. Waterglass is used to render tissues non-inflammable, to protect wood and porous stone, as an addition to cheap soaps, to fix pigments on calico, in the manufacture of artificial stone, as a fixative in mural paintings, also as a cement for glass and pottery. SILVER. This metal is found free in nature and in combina- tion with other elements principally as the sulphide. The usual method of obtaining the metal depends upon the fact that lead, when used with the proper flux, has the power of withdrawing the silver from its ores. The lead buckle thus obtained is heated in a furnace with an excess of air, when the lead burns off, leaving the silver behind. Many other methods have been proposed, but cannot be described at this time. Pure silver has a white ►us color. It is the best conductor of electricity known. It does not oxidize when exposed to the air even if heated and so is classed as one of the noble metals. It is used as a constituent 160 ELEMENTS OF INDUSTRIAL CHEMISTRY of many alloys for jewelry and for coins. It is also used exten- sively for silver plating. SILVER CHLORIDE. This compound is found ready formed in nature as the mineral horn silver, or it may be prepared by add- ing sodium chloride to a soluble silver salt. It is insoluble in water, but easily dissolves in ammonia, potassium cyanide, and sodium thiosulphate. It is used extensively in the preparation of photographic papers. * SILVER BROMIDE. By adding sodium bromide to silver nitrate this compound is formed. It is applied in making the photographic dry plate and in gaslight papers. SILVER IODIDE. When sodium or cadmium iodide is added to silver nitrate this compound is produced. It is applied in the manufacture of photographic dry plates and for developing papers. SILVER NITRATE. By dissolving pure silver in dilute nitric acid silver nitrate is obtained. If a copper-silver alloy is used, the copper may be eliminated by evaporating to dryness and heating the dry mass to a temperature of 250° C. The copper nitrate is decomposed, yielding copper oxide, and as the silver nitrate is not affected, it may be dissolved in water and the solution evaporated to crystallization. It is a colorless salt, soluble in water, melts at 225° C. and decomposes at dull red heat. It is used as a cautery, in photography, in the preparation of indelible ink and for silvering the back of mirrors. SODIUM. This metal is not found in the free condition in nature but is widely diffused in combination with other substances and is especially abundant as the chloride or common salt. Metallic sodium has a silvery appearance closely resembling potassium. It is oxidized rapidly when exposed to the air and so must be preserved under petroleum. Sodium as a metal is used in the preparation of fused sodium peroxide and sodium cyanide. Formerly it was also used to quite an extent in the preparation of metallic aluminium. SODIUM PEROXIDE: Na20 2 . This compound is prepared by heating sodium to 300° C. in aluminium pans in a current of dry air. It is a very energetic oxidizing agent at elevated tem- peratures and when dissolved in water gives off atomic oxygen, thus rendering it of value as a bleaching agent. CAUSTIC SODA. This product is prepared by causticizing sodium carbonate with lime. The purified tank liquor, which must be kept at a specific gravity of 1.1, is treated with lime at ELEMENTS AND INORGANIC COMPOUNDS 161 a boiling temperature. Water or dilute liquor must be added in order that a reverse action will not take place. In the Thomas process the reaction may be carried out in a concentrated liquor, under pressure and at a temperature between 140 to 145° C. The calcium carbonate is allowed to settle and the supernatant liquor is filtered through sand and carbon. The solution of caustic soda is evaporated in cast-iron kettles until all of the water is driven off and the alkali remains as a fused mass. The lower compounds of sulphur, such as thiosulphate, may be oxi- dized by the addition of a small quantity of sodium nitrate. For transportation, the fused caustic is run into sheet-iron drums, which are closed as soon as cold to prevent absorption of water and carbon dioxide. Caustic soda may be purified by solution in pure alcohol, which dissolves the sodium hydroxide, but not the carbonate. A still purer sodium hydroxide may be obtained by the action of metallic sodium on distilled water. There are a number of electrolytic processes for the manu- facture of caustic soda which are discussed under chlorine. Sodium hydroxide is used in large quantities in the manufac- ture of soap, in the manufacture of paper pulp, for mercerization of cotton, in the manufacture of dyestuffs, in the purification of mineral oils and for various other purposes. SODIUM CARBONATE. Before 1791 sodium carbonate was obtained from natural deposits and the ashes of marine plants. At the time of the French Revolution Leblanc brought forward his method for the commercial production of soda from salt. The process, which was introduced in 1791, held sway without competition until 1863, when the Solvay process (ammonia-soda) made its appearance. This would probably have entirely re- placed the Leblanc process were it not for the valuable by-product, hydrochloric acid, which is formed during the operation of the latter. At present the Leblanc process furnishes a little less than half of the sodium carbonate consumed. Leblanc Process. By the action of sulphuric acid on common salt sodium sulphate is obtained. The sodium sulphate is then trans- formed into carbonate by the action of carbon and calcium car- bonate: the reactions involved being represented by the following equation: 2NaCl+H 2 S0 4 = Na 2 S0 4 +2HCl, Na 2 S0 4 +2C = Na 2 S-h2C0 2 , Na 2 S + CaC0 3 = Na 2 C0 3 + CaS . 162 ELEMENTS OF INDUSTRIAL CHEMISTRY Preparation of Sodium Sulphate or Salt Cake. The reaction takes place in two stages, viz.: NaCl+H 2 S0 4 =NaHS04+HCl, NaCl+NaHS0 4 = Na 2 S04+HCl. The furnace used for this purpose is described at another place. The first reaction takes place at a comparatively low tem- perature and at the back of the furnace; when it slackens the charge is raked forward, and is exposed to a higher heat, when the second reaction takes place. The sulphuric acid should be of a strength between 57 and 60° Be. Below 56° Be. it would attack the cast-iron pan of the furnace, and above 60° Be. it forms lumps of salt with an anhydrous coating of sodium sul- phate. This coating prevents the penetration of the acid, thus making the action irregular and incomplete. Conversion of Salt Cake into Carbonate. The salt cake should contain no sodium chloride and but little free sulphuric acid. It should be porous and friable, for which purpose it is exposed to the action of the air for two or three days. It is now mixed with limestone and powdered coal, the proportions indicated by Leblanc being : Sodium sulphate 100 parts Calcium carbonate 100 parts Carbon 50 parts In practice it is usual to use an excess of limestone and coal. At the end of the operation, when the temperature has reached about 1000° C, the calcium carbonate in excess is decomposed with the formation of lime and carbon dioxide. The latter, coming in contact with the carbon, is converted into carbon monoxide; the blue flame which makes its appearance indicates that the reaction is completed. The passage of the carbon mon- oxide through the mass renders it porous. The limestone should be very pure, as silica and aluminium would cause the formation of silicates and aluminates. The coal should contain little or no nitrogen, as this gives rise to cyanides, which react upon iron to form ferrocyanides and, in small quantities, cyanates. Black Ash. In the manufacture of black ash the mixture of sulphate, carbon and limestone is introduced into the back of a black ash or balling furnace, which is a long reverberatory furnace. The mixture is heated at a rather low temperature at first; then ELEMENTS AND INORGANIC COMPOUNDS 163 after some time the charge is raked forward, nearer the grate, where the temperature is much higher, reaching 1000° C. The mass is stirred until it stiffens and the blue flame appears, indicat- ing the end of the reaction. It is now worked together into a ball and raked into wagons, where it rapidly solidifies. On exposure to the air for two or three days the small quantity of lime present slakes, rendering the mass friable and easier to lixivi- ate. The hand-worked furnace is being replaced by the revolving furnace. Good black ash is of a very dark brown or gray color with porous fracture. It contains about 45 per cent of sodium car- bonate, 30 per cent of calcium sulphide, 10 per cent of calcium oxide, 6 per cent, of calcium carbonate and small amounts of sodium silicate, sodium aluminate, sodium sulphide, sodium chloride, ferric oxide and coal, while very slight amounts of cyanide, ferrocyanide and thiosulphate are usually present. Lixiviation of Black Ash. When properly made, black ash is easily extracted by Shank's process. The material is placed in tanks having false bottoms, and is systematically treated with water. The fresh water comes in contact with the nearly exhausted ash and as it becomes more concentrated it meets the fresh ash. The lixiviation should be done at as low a tem- perature as possible and the ash kept covered with water to avoid contact with the air. In case these precautions are not observed, secondary reactions take place, thus reducing the yield of sodium carbonate. Purification and Evaporation of Tank Liquors. The principal impurities of tank liquor are caustic soda, sodium sulphide, sodium thiosulphate, sodium ferrocyanide, sodium ferro-sulphide and traces of other compounds. The liquor is allowed to clarify by sedimentation and is then passed through carbonating towers, where it trickles over porous substances and comes in contact with a current of carbon dioxide and air. The caustic soda and sodium sulphide are here converted into carbonate, the ferro- sulphide is decomposed, and any iron, silica and aluminium present precipitated. Paulie's Process. In this process Mn02, as Weldon mud, is added to the liquor and superheated steam and air are passed through it. Sodium sulphide is oxidized to sulphate, and any iron, silica, and aluminium precipitated. In either case the purified liquor is evaporated in cast-iron pans. As it becomes concentrated a crystalline powder separates, 164 ELEMENTS OF INDUSTRIAL CHEMISTRY Na 2 C03,H20, which by calcination at a red heat is converted to Na2C03- The mother liquor is further purified or used for the production of caustic soda. This liquor usually contains a large amount of caustic soda and sodium sulphide. Instead of calcining the Na2C03,H20. it may be converted into soda crystals (sal soda) by dissolving in hot water and allowing it to crystallize slowly. In this way large, nearly pure, crystals of Na2CO3,10H2O are formed. Ammonia Soda or Solvay Process. This process was intro- duced by Solvay in 1863, and has been worked successfully since about 1873. It consists in reacting upon sodium chloride in a cold solution with hydrogen ammonium carbonate : NaCl+NH 4 HC0 3 = NaHC0 3 +NH 4 Cl. The sodium hydrogen carbonate (bicarbonate) is calcined, which decomposes it into sodium carbonate, carbon dioxide and water. By treating the ammonium chloride formed in the first reaction with lime, the ammonia is regenerated. The carbon dioxide is derived in part from the calcination of the sodium bicarbonate and partly from limestone, which furnishes also the lime for the regeneration of the ammonia from the ammonium chloride. The process is more economical than the Leblanc, the product is purer and there is no troublesome by-products, such as tank waste. In conducting this process a pure concentrated brine solution is saturated with ammonia. The brine is contained in tanks with perforated false bottoms, through which the ammonia is forced in the form of a gas. When the brine is thoroughly satu- rated with the gas it is run into the carbonating tower. The tower consists of a cast-iron cylinder 40 to 60 ft. high and 5 to 6 ft. in diameter. At intervals of 3 to 3J ft. there are fixed plates with a central opening. Over these plates are placed dome-shaped diaphragms, which are perforated with numerous small holes. The ammoniacal brine is forced under pressure into the carbonating tower through a pipe which enters near the middle of the tower. The carbon dioxide, at a pressure of 25 to 30 lbs., is forced into the lower end of the tower and allowed to bubble through the many perforated diaphragms; its ex- pansion as it enters the tower produces a cooling effect which prevents any great rise in temperature. NaCl+NH 3 +H 2 0+C0 2 = NH 4 Cl+NaHC03. ELEMENTS AND INORGANIC COMPOUNDS 165 The bicarbonate of soda being insoluble in the ammonium chlo- ride solution is precipitated, drawn off, filtered, washed with cold water and calcined in cast-iron pans. The carbon dioxide liberated from the bicarbonate is pumped to the carbonating tower, and any ammonia given off is condensed and returned to the ammonia stills. The gases issuing from the carbonating tower are also condensed to recover any ammonia which they contain. The temperature of the solution in the carbonating tower should be carefully controlled, 30 to 35° C. being the temperature most favorable for the action. The soda ash produced by the calcination of Solvay process bicarbonate of soda is white and usually very pure, containing only traces of salt and sodium bicarbonate. Cryolite Process. The reactions involved in this process are as follows: 3XaF,AlF3+3CaC03 = Na 3 A103+3CaF2+3C02. The sodium aluminate resulting from this fusion is decomposed in an aqueous solution by carbon dioxide : 2Xa 3 A103+3C02 = 3Na2C03+Al 2 03. The sodium carbonate formed by this process is very pure. Sodium Bicarbonate. Most of the sodium bicarbonate on the market is produced by the Solvay process. It is used in the manufacture of baking powders, soda water, and other prod- ucts which require a mild alkali. Sodium Chloride. Common salt has been known and used since the time of the earliest man. It is an important constituent of food for both man and animals. It is found in all parts of the world. Small amounts are present in most river waters and some spring waters are impregnated with large quantities of it. Sea water contains it to the extent of about 3 per cent, while the water of the Dead Sea contains about 10 per cent and that of the Great Salt Lake, 9.7 per cent. It is also found in large deposits as rock salt, where it may exist in a colorless transparent form or with varying grades of purity down to a marl-like mass which contains but little salt. The deposits that are worked usually consist of salt not in transparent condition, but in a white, gray or red massive state. When it is transparent it will split out in cubes, but there is no cleavage in its more impure condi- tions. There are many deposits of rock salt in Germany and 166 ELEMENTS OF INDUSTRIAL CHEMISTRY Austria, the most important being at Stassfurt. In Spain there is a bed of importance ; and in fact all countries possess some salt deposits. The United States leads all countries in the production of salt, furnishing in 1912, 33,334,808 barrels of two hundred pounds. Of the various States Michigan produces the largest quantity, in 1912 this State furnished nearly 11,000,000 barrels. While the output of New York is over 400,000 barrels less than that of Michigan, the quality makes it much more valuable. The value of the 1912 production was 12,597,280. New York has led, as far as value goes, for the last five years. Louisiana leads in the production of pure rock salt, but important workings are also found in Kansas, Colorado, and other States. Rock salt and brine, with few exceptions, contain so much impurity that for the table and for many manufacturing purposes the salt must be purified before use. Properties. Sodium chloride is a colorless, crystalline solid, with a specific gravity of 2.13, crystallizing in cubes often with hollow faces. It melts at 815° C. or 1500° F., and volatilizes below a white heat. There is little difference in the solubility of salt in hot and cold water, 100 parts of water at 0° dissolving 36 parts of salt, while 100 parts of water at boiling temperature dissolve 39 parts. This fact makes it possible to separate salt from its impurities, as most other substances are much more soluble in hot than in cold water. Absolutely pure salt is not hygroscopic, but ordinary salt will attract moisture from the air, sometimes in quantities sufficient to form a paste. This is due to the presence of admixed calcium or magnesium chloride, which always accompanies salt in its deposits. Theory of Deposits. The salt beds always give indications of being the result of the drying up of salt seas. In these deposits the admixed salts are found in the relative order of their solu- bility. On the bottom are found the insoluble calcium sulphate, calcium and magnesium carbonates, while on the top are the deliquescent chlorides of calcium and magnesium, with the chlorides of sodium and potassium and their sulphates and the sulphate of magnesium intermediate in the order of their solu- bility. In the Stassfurt deposits sixteen different salts may be recognized. The problem of producing commercial salt is to separate it from its impurities, and this is done usually by recrys- tallization. Working of Deposit. The working of the salt deposits is dependent upon the purity. In Germany, Louisiana, and many ELEMENTS AND 1N0KGAXIC COMPOUNDS 167 other deposits the salt is mined. Shafts are sunk and galleries are run, often a mile or more in length. The salt is under cut and then blasted down from above with low-power dynamite. The broken-down mass is taken to the mill and run between corrugated rollers. The crushed salt is screened to various sizes, the finer grades being blown to remove the dust. One Colorado deposit is in the form of a crust over an underground lake of brine. In working this deposit the earth is removed and the salt cut like ice, washed in the brine, and then crushed. In other deposits, as in New York, the location of the bed or the large quantity of admixed cla} T or earthy matter renders this method impractical, and the salt is removed from the ground by boring wells and dissolving out the salt with water. In this case it is important to protect the upper part of the wells with pipes to prevent the absorption of the brine by the surface soil. The brine, whether natural (sea water, spring water) or artificial, must now be concentrated. This may be done either by natural evaporation through the aid of the sun or by the use of fuel. A means of purifying both rock salt and brine in one process consists in saturating the latter with the former and then crystal- lizing. In warm countries, as along the shores of the Mediter- ranean, and in California, the sea water is collected in reservoirs and then exposed in shallow basins to the heat of the sun, the salt being removed as it crystallizes, placed in heaps and allowed to drain and dry. One plant in California, covering 600 acres, divided into seven basins, requiring fifteen miles of levees, pro- duces 2000 tons of salt a year. The pumping is done by wind mills. All of the salt is collected from the last basin. The season is from "Slay to October. This is so impure that it must be refined before it can be used for table or dairy purposes. A process similar to this is practiced in working the salt in Great Salt Lake. The water is pumped into crystallizing ponds, which are simply large areas, enclosed with mud banks and divided into smaller basins. The total area of these ponds is about two square miles. The crystallization is carried on from March 15th to September loth, after which time the liquid (" bittern ") is run back into the lake and the " crop " gathered. The " crop " consists of a layer of about 6 ins. of salt, or about 900 tons per acre. The brine which was run back into the lake carries with it the bulk of the impurities, particularly the calcium and magnesium salts, but the gathered salt is largely contaminated with sodium sul- phate. This impurity is removed by drying, as the sulphate 168 ELEMENTS OF INDUSTRIAL CHEMISTRY will effloresce and be reduced to a fine powder. When this powder is acted upon by a current of compressed air the fine sulphate will be blown away, leaving the coarser salt. When this is ground and screened it contains about 98 per cent of sodium chloride. The fine material which was blown out contains about 75 per cent of salt; this is pressed into cakes, and is used for cattle and sheep. This salt is not very satisfactory for dairy purposes, owing to the sulphates it contains. In Norway and other cold* countries the sea water is concentrated by freezing the water in enclosed basins, then pumping out the still liquid part, which contains all of the salt, and evaporating to crystallization. Evaporation of Brine. The usual form of apparatus for evaporating the brine by artificial heat is a long, narrow, shallow pan, heated at one end and with flues running the entire length. These pans vary from 40 ft. to over 100 ft. in length, and from 10 to 25 ft. in width. The salt is raked out as it forms. The most difficult impurity to remove is calcium sulphate, which collects in the form of a scale on the pan. This must be removed, or local superheating will result in the destruction of the pan. Various attempts have been made to use the vacuum pan in the salt-boiling industry, but on account of the separation of anhydrous calcium sulphate, this process has not proven success- ful. Another objection advanced against the vacuum boiled salt is that it is large grained and must be crushed before use; this produces much dust and consequently loss. In the boiling of salt, if a small quantity of fat or oil is added to the pan it pre- vents the formation of a crust on the surface, which would retard evaporation. The salt which is fished out of the pans is exposed to steam. This dissolves out the more soluble chlorides of calcium and magnesium, after which it is whizzed and dried. Two English patents have recently been taken out for purifying salt. The first heats the dry salt to fusion and allows it to remain in that state until the impurities settle, then the clear liquid is decanted. The second electrolyzes a portion of the brine, producing sodium hydroxide, blows carbon dioxide through to form carbonate, then mixes this with the raw brine, precipitat- ing the calcium and magnesium, filters and evaporates. Neither of these methods are used in the United States. Uses of Salt. In addition to its use for table and dairy pur- poses, sodium chloride is used in preparing sodium sulphate, sodium carbonate, and indirectly for the production of all sodium salts. It is used in tanning, wet extracting of copper and silver ELEMENTS AND INORGANIC COMFOUNDS 169 from ores, as a glaze for common earthenware or stoneware, and as a food preservative. Hydrochloric acid is also produced from common salt. Some countries impose a tax on salt used for table or dairy purposes; commercial salt being prepared under government supervision and " denatured " by the addition of various sub- stances which would render it unfit for table use, such as Glauber's salt, soda ash, 4-15 per cent, soda crystals, 12 per cent, sulphuric acid, 2 per cent, strong hydrochloric acid, 2 per cent, ammonia liquor, or aniline dye. The use to which the salt is to be put determines which of the denaturing substances is to be used. SODIUM NITRATE. This compound is found in large quan- tities, especially in Chile. The supply, however, is becoming exhausted, and as the material is a very important one from an agricultural point of view, ways and means have been devised for producing it artificially by electrolytic methods. SODIUM NITRITE. This compound is prepared by heating sodium nitrate with metallic lead to a temperature of 450 to 500° C. It is a very important chemical and is used extensively in the manufacture of dyestuffs and colors. SODIUM SULPHATE. Sodium sulphate occurs in nature both in crystallized form and dissolved in water. Large deposits are found in Arizona, Spain, Peru, Hungary, Siberia, and the Hawaiian Islands. Some salt works evaporate the bittern for the produc- tion of sulphate, but this is as a rule contaminated with much magnesium. Much of this sulphate is pure enough for technical uses. Nearly all natural sulphate, however, contains enough iron to make it unfit for glass manufacture. As a usual thing sodium sulphate is prepared in the anhydrous state, and only a small proportion is converted into the crystallized form. The usual method of preparing salt cake is by the action of sulphuric acid upon salt, producing hydrochloric acid as a by- product. In this country, where the Leblanc soda process is not used, hydrochloric acid is made, and the sulphate obtained as a by-product. In the manufacture of nitric acid, by the action of sulphuric acid upon soda niter, the sulphate formed is NaHSO/t, which is of very little technical use. In most places this is considered a true waste product, and treated as such. If vitriol and niter were taken in the proportion required to produce a neutral sulphate, the extra cost of working and the loss by decomposi- tion would more than balance the value of the sulphate formed. 170 ELEMENTS OF INDUSTRIAL CHEMISTRY In England it is customary to mix the niter cake with the salt in the salt-cake furnace and work it up in that way. This is done in some places in this country and the practice is growing. Mechanical furnaces must be used in this process. Many other methods have been proposed for making sulphate, but the only one to meet with success is that of Hargreaves and Robinson, which is used to some extent in Europe, but finds in this country limited application, due largely to the fact that Leblanc soda is not made here. By far the most important method for the production of sul- phate is the old method of decomposing salt with sulphuric acid. This decomposition takes place in two stages: first, NaCl+H2S04 = NaHS04+HCl; second, NaCl-f-NaHS0 4 = Na 2 S0 4 +HCI. The first of these takes place at ordinary temperature, but the second requires considerable heat. The actual decomposition is usually accomplished in two parts of the furnace, except where the cylinder furnaces are used. Here the operation is complete in the one apparatus. The salt and sulphuric acid are mixed jn a cast-iron pan and gently heated, usually by waste heat, until the mass becomes stiff. It is then pushed over onto the bed of a reverberatory furnace, where it is heated until all the acid is driven off. In many works, instead of the reverberatory furnace a muffle is used, thus keeping the acid vapors and the furnace gas separate, and not contaminating the sulphate with the furnace dust, thus permitting the use of coal instead of coke for fuel. During the second heating the mass is worked by rakes and slice bars in order to insure complete action. Formerly the pans were made of lead, but they have almost entirely been replaced by cast-iron pans. The lead pans are still used in making salt cake for the plate-glass industry. The iron pans, Fig. 69, are circular in shape, from 10 to 14 ft. in diameter, and about 2 ft. deep. Fig. 69. They are at the bottom 5 to 7 ins. thick and on the sides 2 to 3 ins. They are built in the furnace and covered with a gas-tight dome made of firebrick, and provided with an earthenware pipe to carry away the hydrochloric acid. Mechanical salt-cake furnaces have been introduced in England, but they are objected to on account of the introduction of a considerable quantity of iron into the salt cake. These furnaces consist of flat-bottomed iron pans, provided with a shaft carrying plows to keep the mass thoroughly worked ELEMENTS AND INORGANIC COMPOUNDS 171 up. When the reaction is complete the salt cake is raked out and allowed to cool. Salt cake contains from 93 to 99 per cent of Na2S0 4 . The varying quantities of impurities in salt cake, such as NaHS0 4 , CaS0 4 , FeS0 4 , Fe 2 3 , MgS0 4 , Si0 2 , NaCl, depend upon the salt used and the kind of furnace. The sulphate from Hargreaves's process gives a purer product, excepting its content of NaCl, which is high. Glauber's Salt In the production of Glauber's salt, the salt cake is dissolved in hot water, filter pressed and run into coolers. If the salt is desired in large crystals the coolers are made of heavy planking and so protected that the crystallization takes place without any agitation. If from 10 to 12 per cent of soda is added with the salt cake, the crystals will be larger, firmer and more like soda. If small granular crystals are desired the hot liquid is run into large coolers, and when the temperature has fallen to about 30° C. the liquid is agitated either by a wooden paddle or by blow- ing compressed air through it; this gives the sulphate in the form of fine needles, much resembling Epsom's salt, and it was formerly used to adulterate and even as a substitute for that salt. The addition of some soda ash before crystallization serves the double purpose of improving the appearance of the crystals and precipitating the iron. A little milk of lime is also often added to free it from traces of iron. In order to get a very pure Glauber's salt, the crystals first obtained are freed from the mother liquor by whizzing, and are recrystallized. The crystallization of a batch of sulphate crystals takes from five to eight days in winter, and from fifteen to twenty days in the summer. The great change in the solubility, due to a slight change in temperature, makes it more profitable to push the crystallization during the winter and store up the material during the summer. The principal uses of sodium sulphate are soda making, glass making, especially window and bottle glass, and for making ultramarine. In the form of Glauber's salt it is used as a mor- dant assistant, in the production of thiosulphate, in medicine, especially for veterinary uses, and in the making of cooling mixtures. SODIUM SULPHITE. This compound is prepared by saturat- ing a solution of sodium hydroxide or carbonate with sulphur dioxide and then adding the same amount of sodium hydroxide 172 ELEMENTS OF INDUSTEIAL CHEMISTRY or carbonate as was originally introduced. It forms large crystals, which are used in medicine, in photography as an antichlor, and is the raw material for making the sodium thiosulphate. SODIUM BISULPHITE. This is prepared by saturating sodium carbonate or sodium hydroxide with sulphur dioxide, and comes into the market as a powder or as a concentrated solution. It is used in bleaching, as an antichlor, in paper manufacture, in the manufacture of dyestuffs, and in chrome tannage. SODIUM THIOSULPHATE. This compound is prepared by boiling a solution of sodium sulphite with an excess of sulphur. It is used in photography, as an antichlor, and in the tanning of leather by the Schultz process. SODIUM SULPHIDE. This compound is prepared by heating a mixture of sodium sulphate, salt and coal to a temperature of about 900° C. It is used in dyeing cotton with sulphur colors, in the manufacture of dyestuffs, in unhairing hides and skins, and for denitrating artificial silk. SODIUM CHLORATE. Sodium chlorate is much more soluble than the potassium salt, and cannot be made in quite the same way. In the manufacture of sodium chlorate, calcium chlorate is first made. This is evaporated to about 1.5 gravity and then cooled. Four-fifths of the calcium chloride solidifies. The mother liquor is drained off and most of the calcium precipitated with sodium sulphate, a little sodium carbonate being added to remove the last of the calcium. The solution of sodium chloride and sodium chlorate is then boiled down. Most of the sodium chloride separates from the boiling hot solution and is removed. The solution is then cooled, and much of the sodium chlorate crystal- lizes out. Twenty per cent or so is, however, left in the mother liquor, which goes back into process. The separation is based on the difference in solubility of sodium chlorate and sodium chloride in hot and cold solutions. STRONTIUM. This is one of the less commonly occurring elements and is found in nature principally as the mineral stron- tianite. It forms a series of compounds somewhat similar to those of barium. STRONTIUM NITRATE. This compound is prepared by treating the carbonate with nitric acid. It is used in the manu- facture of fireworks for producing red light. SULPHUR. This is an element which has been known for centuries, and some of the alchemists have even described com- ELEMENTS AND INOEGANIC COMPOUNDS 173 pounds of it with the metals. It is known in the amorphous, rhombic and prismatic conditions. It is of a yellow color, insolu- ble in water; slightly soluble in alcohol, ether, oils, and fat, but very soluble in carbon disulphide, and fairly so in petroleum ether. Sulphur is found in large quantities in Sicily and up to within the past few years this country has furnished practically all of the world's supply. The recent opening up of the Louisiana deposits, however, has driven Sicily sulphur from the American market, as we in this country are now being supplied from the Louisiana fields. The Sicily sulphur is a surface deposit which on being mined is placed in piles and heated. The molten sul- phur in this way runs off from the impurities and when cool is ready for the market. The Louisiana deposits are too deep to be mined, and although these rich fields were known as far back as 1868, no method of obtaining the sulphur was devised until the Frasch method was discovered. In 1902 the Union Sulphur Company started work under the Frasch process, obtaining about 100 tons per day. The production, however, has steadily increased until at the present time several thousand tons are being produced daily. The Frasch process consists in sinking a shaft or well about 12 ins. in diameter, just as in the case of boring for oil or salt, until the sulphur is reached. The well is lined with an iron pipe in which are three other concentric tubes lined with aluminium, which are driven into the sulphur. Through the largest of the tubes superheated water under a pressure of 100 lbs. is introduced. The heated water melts the sulphur, causing it to rise in the outer tube. The sulphur, however, being heavy, will not flow to the surface, so to overcome this hot air under pressure is caused to bubble through the sulphur, thus forming an emul- sion, which can easily be pumped to the surface. As the sulphur issues from the tube it is run into large wooden boxes, where it settles away from the water into an immense hard cake. The boxes are about 20 ft. wide by 100 ft. long, the sides being built as the sulphur enters, some boxes being 30 to 40 ft. high. When cool the planks are removed from the sides and the solid sulphur broken out by means of a steam shovel and loaded directly into cars or boats. The product is so pure that it needs no further refining. FLOWERS OF SULPHUR. By heating sulphur in a Closed retort it distills and the volatile product formed on passing into 174 ELEMENTS OF INDUSTRIAL CHEMISTRY a cool chamber collects on the walls in the farm of fine crystals, which are known as flowers of sulphur. BRIMSTONE. During the refining of sulphur for flowers of sulphur much of the distillate collects on the floor of the condensing chamber and eventually melts again. The molten sulphur is then drawn off into molds, in which it hardens, thus forming sticks of sulphur known as brimstone. FLOUR OF SULPHUR. A large amount of sulphur is passed through grinding mills, when it is converted into a powder known as flour of sulphur. LAC SULPHUR. By precipitating sulphur from some of its combinations a very light-colored product results, which is filtered off, dried and comes into the market as lac sulphur. Sulphur is used to some extent in the manufacture of sul- phuric acid; for making bisulphites, sulphites, and thiosulphates : and for various other purposes. SULPHUR MONOCHLORIDE. To prepare this compound a current of chlorine is passed over melted sulphur, which is heated to about 130° C. Chloride of sulphur mixed with sulphur distills over and is purified by redistillation. It is a somewhat oily liquid of a yellowish-brown color, having a suffocating odor and boiling at 144° C. When brought in contact with water it decom- poses with the formation of hydrochloric acid, sulphur, sulphur- ous acid and a small amount of sulphuric acid. Its chief use is in the vulcanization of rubber and in the manufacture of rubber substitutes. TANTALUM. This is one of the rare elements and occurs usually with columbium. It has recently acquired importance due to its application in the tantalum filament for the electric lamp. The lamp consumes less than one-half the energy of a carbon filament lamp for the same candle power, TELLURIUM. This element occurs in small quantities in the natural state mixed with gold and silver. It belongs to the same group as sulphur and forms compounds somewhat similar to that element. It has at present no commercial applications. TERBIUM. This is one of the rare elements belonging to the same group as cerium. THALLIUM. This is one of the rare elements and has no commercial value. THORIUM. This element is found in the monazite sands, and in its nitrate is used quite extensively in the manufacture of gas light mantles. The mantle used was at first made from ELEMENTS AND INOKGANIC COMPOUNDS 175 cotton or linen, but to-day is prepared from artificial silk. The woven fabric is dipped into a solution of the nitrate of these rare earths, allowed to dry, dipped again and again or until a sufficient quantity of the salts have been absorbed. The dry mantle is then dipped in a solution of collodion. The mantle when used is put in position on the burner, the collodion and fiber burnt out, thus leaving a network of the oxides, which glow when heated, with the characteristic intense light. THULIUM. This is one of the rare earth elements and has no practical application. TIN. This is a metal which has long been known and is found in nature as the oxide occurring in many minerals. It is a metal with a silvery appearance and is not changed in the air at ordinary temperatures. Tin is used extensively for making cooking utensils, for lining condensers, as tin foil, and as a con- stituent of many alloys. It forms both stannous and stannic salts. Stannous Chloride. The hydrated salt, SnCl 2 2H 2 0, is prepared by the solution of the metal in concentrated hydro- chloric acid, aided by moderate heat. The addition of a little nitric acid facilitates the reaction. The solution is concentrated by evaporation, cooled and allowed to crystallize. When dis- solved in water it undergoes partial decomposition with the formation of an insoluble oxychloride. It is a valuable mordant and is used as a weighting material for silk, and in calico printing. STANNIC CHLORIDE. The hydrated compound is obtained from the mother liquor of stannous chloride by the progressive addition of nitric acid; the resulting liquid is concentrated and the stannic chloride allowed to crystallize. The penta hydrate, SnCl4,5H 2 0, may be prepared by passing chlorine through the mother liquor from stannous chloride. Its principal use is that of a mordant. SODIUM STANNATE. The salt, Na 2 Sn0 3 ,3H 2 0, may be obtained by fusing sodium hydroxide and metastannic acid to- gether, or by boiling tin scrap with sodium plumbite. It is known as preparing salt, and is used as a mordant. Solutions of tin in sulphuric acid and oxalic acid are known in the trade as tin spirits, and used for mordanting. TITANIUM. This is one of the less commonly occurring metals and is found principally in the mineral titanite. As a metal it is used in conjunction with iron for making a very tough steel. As the compound potassium titanium oxalate it is much 176 ELEMENTS OF INDUSTRIAL CHEMISTEY used as a fixing agent for basic colors employed in dyeing cotton and leather. TUNGSTEN. This metal is found in certain minerals, prin- cipally in wolframite. The free metal is obtained by the Gold- schmidt process by reducing tungsten oxide with aluminium powder. In the metallic state it is used with iron for making hard tungsten steel. In the colloidal form it is now being used extensively for making the tungsten electric lamp filament; and in the form of sodium tungstate as a fireproofing on wood and fabrics. URANIUM. This is one of the rarer elements and is found in the mineral pitchblende. Its oxide is used in producing a yellow fluorescence in window glass. VANADIUM. This metal occurs in the mineral vanadinite. It is used to some extent with iron in producing a vanadium steel. Certain of its salts are used in dyeing and printing, while its oxides are used in the manufacture of glass and pottery. XENON. This is one of the very rare elements occurring in the atmosphere to the extent of about one part in forty million. YTTERBIUM. This is one of the rare elements and occurs in the mineral gadolinite. YTTRIUM. This is a rare element also occurring in the mineral gadolinite. It is used in the filament of the Nernst lamp. ZINC. This metal usually occurs in nature as the sulphide and is found in many minerals. The sulphide on roasting is converted into the oxide of the metal and sulphur dioxide escapes. The oxide may then be readily reduced to the metal by heating with carbon in a muffle furnace. Metallic zinc has a grayish- white appearance. It is used in making zinc-coated wire and iron, the latter being known as galvanized iron. It is used in various alloys and has many other applications. ZINC OXIDE. This compound is used extensively in the manufacture of paint and is discussed in that chapter. ZINC SULPHATE. White vitriol, ZnS0 4 ,7H 2 0, is prepared by dissolving scrap zinc in dilute sulphuric acid. Upon evapora- tion a white crystalline product separates. It is used to some extent in calico printing and in dyeing, as a drier for linseed oil, as a disinfectant, and as an astringent. ZIRCONIUM. This is one of the rare earths and was used in preparing the first incandescent mantles, CHAPTER VII CERAMIC MATERIALS AND PRODUCTS LIME. Lime, when good, is nearly pure calcium oxide, CaO, or a mixture of calcium and magnesium oxides. High calcium limes are stronger than those containing considerable percentages of magnesia. They are also better suited for mortar work, as they slake more readily. Magnesium limes, on the other hand, are better finishing limes, because they work smoother under the trowel. Pure lime, whether magnesium or not, is snow white. A very small percentage, however, of certain impurities may give the lime a gray or yellow color. These impurities are chiefly iron and manganese. Through certain methods of burning the ash of the fuel may be introduced into the lime, causing discolora- tion. Woodburned lime is usually much whiter than lime burned with coal. Lime is made by burning limestone in suitable furnaces at a temperature sufficient to drive off all of its carbon dioxide, the reaction being CaC0 3 = CaO+C0 2 . Theoretically, 2350 cal- ories per gram of lime are required to produce this change. This temperature is between 600 and 900° C. If a temperature much above 1200° C. is employed, the lime will be partially fused on the outside of the lumps. This causes the lime to be very slow in slaking, which is undesirable, as some of it may escape hydration in the mortar box and later will expand, or what is technically termed " blow " or " pop " in the wall. This latter manifests itself in small blisters in the finished work. Intermittent Kilns. The types of kilns ordinarily employed in burning lime may be divided into two classes — intermittent kilns and continuous kilns. The intermittent kilns are primitive and uneconomical. They are, however, frequently used by farm- ers and other small producers of lime. These kilns are usually made of large blocks of the limestone itself, though sometimes brick is used. The kilns are usually located on the side of a hill in order that the top may be accessible for charging by wagons and the bottom for drawing the lime and supplying the fuel. 177 178 ELEMENTS OF INDUSTRIAL CHEMISTRY In charging the kilns an arch of large blocks of limestone is built 2 or 3 ft. from the ground, numerous small openings being left in it through which the flames may pass to the interior of the kiln. The fire is built under the arch, and on the top of the latter the limestone is piled, the charge usually consisting of stone from 2 to 8 ins. in diameter. After the kiln is full, a fire, usually of wood, is started, and the temperature gradually raised to prevent the limestone arch from crumbling. After about six or eight hours the temperature is raised to a red heat and main- tained at this temperature for about two days. The kiln and contents are then allowed to cool and the lime drawn by pulling down the arch. There is a great waste of heat and time in these kilns, owing to the fact that the kiln must be cooled and reheated each time it is charged. Old kilns of this sort can usually be seen in any of the limestone farming regions. Continuous Kilns. Three different types of continuous kilns are employed: these are (1) the vertical kiln with mixed feed, in which the limestone and fuel are charged in alternate layers; (2) the vertical kiln with separate feed, in which the limestone and fuel are not brought into contact; and (3) the chamber or ring kiln. Vertical Kilns. Vertical kilns with mixed feed are very similar to intermittent kilns, except that they are provided with an arrangement whereby the lime may be drawn at regular intervals from below. They are also usually somewhat larger than inter- mittent kilns. Like the latter, they are built on the side of a hill, usually of limestone blocks, and are sometimes lined with firebrick. In charging them, first a layer of anthracite coal or coke and then a layer of limestone is fed into the top. Fire is started at the bottom and works its way up. The process of charging and drawing the lime is continuous. These kilns are economical and, for the same size kiln, yield a larger quantity of product than do the vertical kilns with separate feed. On the other hand, the lime is contaminated by ash of the fuel, and the lime burned in these kilns must be carefully sorted in order to discard those lumps to which the fuel ash has adhered. The vertical kiln with separate feed usually consists of a steel cylinder lined with firebrick. These are equipped with two fire- places for the burning of the fuel, which are built into the sides of the kiln, so that the fuel is not mixed with the stone. The hot gases of combustion pass from the fire-box into the kiln, while the ash of the fuel drops through the grate bars into an ash pit below, and does not mix with the lime. The kilns are usually constructed CERAMIC MATERIALS AND PRODUCTS 179 with hopper-shaped cooling chamber, set below the fire-box, which is closed by doors at the bottom. The cooling chamber holds about one draw of lime. These kilns are from 6 to 10 ft. in cross-section, and from 40 to 50 ft. in height. They are usually charged by employing an incline and a cable hoist, by means of which the cars of limestone are drawn from the quarry to the top of the kilns. These kilns are sometimes provided with steel stacks in order to induce a better draft, as it has been found that the better the draft the greater facility with which the lime can be burned. Ring Kiln. The chamber or ring kiln is employed to some extent abroad, but has not been used in this country. It con- sists of a series of chambers which are built about a central stack and connected to the latter by flues. These chambers are alter- nately charged with fuel and limestone. Any chamber may be disconnected from the flue at will and also separated from those before and after it by partitions. As a chamber burns out, it is disconnected, the lime removed and the chamber recharged. As a chamber is charged it is connected with the stack and the flames passed through all the other chambers to this one, and thus to the stack. These kilns are economical of fuel, but require considerable labor. Hydrated Lime. When lime is treated with water it combines with the water to form calcium hydroxide, CaO+H20 = Ca(OH) 2 . If the lime is free from impurities, it w T ill take up 32.1 per cent of its own weight of water. A less amount of water than the theoretical quantity, however, is required thoroughly to hydrate lime, because of the impurities that are always found to a greater or less extent in all commercial limes. Until very recently, lime was always hydrated or slaked by the mason just preparatory to its use. An excess of water was always used, and the calcium hydroxide formed with this a wet mass called lime putty. Re- cently, mechanical means of hydration have been introduced whereby the lime is hydrated by the manufacturer with just sufficient water to form the hydrate, leaving none in excess. This hydrated lime is a fine dry powder, practically all of which will pass through a 100-mesh screen. It is packed in paper bags or cloth sacks, and will keep indefinitely. It can be stored with- out danger of causing fire, which is not true of caustic lime. Mortar made with it shows less danger of blowing or popping in the walls. It may be added to cement, when it makes the latter to some extent waterproof and more easy to trowel. 180 ELEMENTS OF INDUSTRIAL CHEMISTRY Hydraulic Lime. Limestones containing appreciable amounts of impurities sufficient to give the calcined product hydraulic properties, but insufficient to take up all the lime present, make, when burned, hydraulic limes. They form an intermediate product between ordinary lime and natural cement. These products range from feebly hydraulic limes to limes which harden quite satisfactorily under water. At one time these limes were manufactured to a large extent in Europe. They have never, however, been manufactured in any quantity in this country. They are made by burning limestone containing from 10 to 17 per cent silica, alumina and iron and from 40 to 45 per cent lime. Magnesia may replace lime to a considerable extent. Hydraulic lime slakes with water jus fas does ordinary lime, only much more slowly. GRAPPIER CEMENTS. These are obtained by grinding the hard cores which are obtained in the manufacture of hydraulic lime, and consist of that portion of the hydraulic lime which dees not slake when water is added. La Farge cement is of this class, and is imported extensively in this country, owing to its light color and the fact that it does not stain marble and other building stones as does Portland cement and natural cement. NATURAL CEMENT. Natural cement was at one time manu- factured extensively in this country. Owing to the cheapness, however, with which Portland cement can be manufactured, it is being replaced by this latter. Natural cements are produced by burning and subsequently grinding clayey or argillaceous limestones, which are natural mixtures of calcium carbonate and clay. These limestones usually carry from 13 to 35 per cent clayey matter (Si02+Al203+Fe2C>3), and often a considerable percentage of magnesia, which seems to be interchangeable with lime and to replace the latter without disadvantage. PORTLAND CEMENT is now considered next to iron and steel as our most important building material, and the production of this in the United States amounts to over ninety millions of barrels annually. Portland cement is manufactured by com- bining a material high in lime, such as limestone or marl, with one in which silica, iron oxide and alumina are the chief constitutents, such as clay or shale. The raw materials are intimately mixed by finely grinding the two. The fine powder is then subjected to a temperature of from 1400 to 1600° C, when a sintering or semi-fusion takes place and the mixture rolls up into little balls varying in size from that pf a walnut down to that of wheat, with CERAMIC MATERIALS AND PRODUCTS 181 an occasional larger piece and some fine sand. After cooling, these lumps or " clinkers " are mixed with a small amount (2-3 per cent) of gypsum and finely pulverized. The resulting powder is Port- land cement. The following diagram explains this graphically: LIMESTONE OR MARL OR CHALK CLAY OR 5HALE OR SLAG OR CEMENT ROCK Mixed in Proper Proport- ions as shown by Analysis Pi .1 erized tea fineness of 90% to 95% passing a No IOC Test Sieve Burned afo Tempera- ture of from 1400° C to 1600° C Pulverized toa fineness of at /east 92% Passing a No. iOO Sieve and 75% Passing a No. 200 Sieve PORTLAND CEMENT It is now generally agreed that Portland cement is a solid solution of lime in a magma of ortho-silicates and ortho-aluminates of lime. It is therefore impossible to ascribe to Portland cement any definite chemical formula. The composition of Portland cement, however, has a great bearing upon its physical properties. The conditions of manufacture, particularly as to burning and grinding, also influence this. The composition of Portland cement of good quality is usually within the following limits : Composition of Poetland Cement Limits, Per Cent. Average, Per Cent. Silica 20-24 22.0 Iron oxide 2-4 2 . 5 Alumina 5-9 7 . 5 ' Lime 60-64.5 62.0 [Magnesia : . . . ; 1-4 2 . 5 Sulphur trioxide 1-1 .75 1.5 182 ELEMENTS OF INDUSTRIAL CHEMISTRY Practical experience has shown that the essential elements in cement are lime, silica and alumina. Iron oxide is present in nearly all clays and shales, and hence is always present in cement. It has a definite advantage, in that it assists in burning and lowers the temperature of the latter process. Cement containing no iron is white, but rather hard to burn. The proportions of a good cement should satisfy the following ratios: . Per cent lime = 1 9 to 2 1 Per cent silica + per cent iron oxide + per cent alumina Per cent silica Per cent alumina 2.5 to 4. In the manufacture of Portland cement great care is taken to see that the composition satisfies the above. If too much lime is present the cement will be " unsound " — that is, in time concrete made from it will expand and crack. If too little lime is present the concrete will be low in strength and may " set " quickly — that is, harden before the masons have a chance to place it in the forms. Cement in which alumina is high is also apt to be quick setting, and is hard to burn uniformly. High silica cements are usually very slow hardening, and do not attain their full strength for a considerable period. Cements should not contain more than 4 per cent magnesia, or 1.75 per cent SO3. The latter is usually introduced in the form of gypsum, and is added to regulate the setting time of the cement. * The materials from which Portland cement is manufactured may be divided into two classes: those which supply the lime and those which supply the silica, iron oxide and alumina. The first are termed calcareous and the second argillaceous. The following groups show the principal materials used in the manu- facture of Portland cement. Calcareous Materials. Argillaceous Materials. Limestone Cement Rock Clay Marl Shale Chalk Slate Alkali waste Blast furnace slag The cement rock is an argillaceous limestone which contains usually between 65 and 80 per cent carbonate of lime. If it CERAMIC MATERIALS AND PRODUCTS 183 contains more than 75 per cent it is necessary to add clay, shale or slate to it in order to make a satisfactory mixture for burning. If it contains less than 75 per cent it will be necessary to add limestone for a similar purpose. Limestone is usually mixed with clay or shale, marls and chalks with clay or shale. Blast furnace slag is used with lime- stone. Alkali waste (or precipitated CaCC>3, obtained from the manufacture of caustic soda) was at one time mixed with clay, but is not now employed for the manufacture of Portland cement. Limestones, marls and chalks which are to be used in the manu- facture of Portland cement should contain less than 2\ per cent magnesia and preferably not more than 3 or 4 per cent silica, iron oxide and alumina combined. Clay, shales and slates should all have at least 2 J and not more than 4 times as much silica as alumina. Exceptions to this are in the case of a high silica lime- stone, with which a high alumina clay may be used to advantage, since all that is necessary is that the mixture shall satisfy the requirements expressed by the above formulas for the composi- tion of Portland cement. Three processes are employed for the manufacture of Port- land cement — the dry process, a semi-wet process, and a wet process. The dry process is employed exclusively for the manu- facture of cement from cement rock and limestone, and also from limestone and shale and limestone and blast furnace slag. The semi-wet process is employed at a few plants manufacturing cement from limestone and clay. The wet process is employed by plants using marl and clay. The dry process is an American invention, is the most econ- omical of the three and is the one most largely employed in this count ry. In this process the materials are dried and mixed, ground to such a degree of fineness that at least 92 per cent of the mix will pass a 100-mesh sieve. The material is then burned in a rotary kiln at a temperature of from 1400 to 1600° C. The resulting clinker is then mixed with 2 to 3 per cent of gypsum, ground to pass a 100-mesh sieve and is known as Portland cement. The grinding is done in various forms of mills and many mechanical operations are involved. The most important stage, however, is the burning, and to make this clear a description of the rotary kiln will be found below. Rotary Kiln. The rotary kiln in its usual form, Fig. 70, consists of a cylinder from 6 to 8 ft. in diameter and from 60 184 ELEMENTS OF INDUSTRIAL CHEMISTRY to 150 ft. long, made of sheet steel and lined with firebrick. The steel sheets are from \ to -^ in. thick, and are held together by single-strap butt joints. This long cylinder is supported at a very slight pitch (f in. to the foot) from the horizontal, on two or more tires made of rolled steel, which in turn revolve on heavy friction rollers. The kiln is driven at a speed of from one turn a minute to a turn in two minutes by a girth-gear situated near its middle, and a train of gears. The power is supplied by either a line shaft or a motor. The upper end of the kiln projects into a brick flue, which is surmounted by a steel stack, also lined with firebrick for its entire height. The flue is provided with Fig. 70. a door at the bottom, which serves not only to allow the flue to be cleared of the dust which accumulates in it, but also as a damper to control the draft of the kiln. The material to be burned is usually fed into the kiln through a horizontal water-jacketed screw conveyor, or else spouted into it through an inclined cast-iron pipe. When slurry is to be burned this is pumped into the kiln. The dry raw material is kept in large steel bins above the feeding device, while slurry is stored in vats, in order, in either case, to have on hand a constant and regular supply. The raw material feeding device is usually attached to the driving gear of the kiln, so that when the kiln stops the feed also stops. CERAMIC MATERIALS AND PRODUCTS 185 The lower end of the kiln is closed by a firebrick hood. This is usually mounted on rollers, so it can be moved away from the kiln when the latter has to be relined. The hood is provided with two openings: one for the entrance and support of the fuel-burning apparatus, and the other for observing the opera- tion, temperature, etc., of the kiln, and through which bars may be inserted to break up the rings of material which form, and to patch and repair the lining. The lower part of the hood is left partly open. Through this opening the clinker falls out and most of the air for combustion enters. The kiln is heated by a jet of burning fuel, usually powdered coal, but sometimes (as in Kansas) natural gas and (as in Cali- fornia) fuel oil are used. The coal is blown in by a blast of air supplied by either a fan or air compressor. If the fan is used, about 20 per cent of the air necessary for combustion is supplied in this way. If the compressor is employed, only 5 to 10 per cent of the air is delivered by the compressor. The necessary temperature of the hottest part of the kiln is about 1400° C, and is rarely ever less than 1600° C. To properly maintain this temperature, about 80 to 160 lbs. of fuel are required per barrel of cement, the actual amount depending on the coal itself, the material to be burned and the dimensions of the kiln. The longer the kiln, the greater economy it will show. Dry materials require much less coal than slurry. With limestone and shale mixture, and a kiln 100 ft. long by 7 ft. in diameter, the coal consumption will amount to about 90 lbs. of good gas slack per barrel. A kiln 60 ft. long by 6 ft. in diameter will, on the other hand, require about 110 lbs. of this material per barrel. Coolers. As the clinker leaves the kiln at about 2000° F., it is entirely too hot to grind , and must be cooled to ordinary air temperatures. This can be done by allowing it to lie in piles; but as it is a slow way of doing it, mechanical devices are usually resorted to. These may consist of either revolving horizontal cylinders or vertical stationary coolers. The former consist of steel cylinders provided with angle irons on their insides to carry the material up and drop it through the current of air passing through the cylinders. They are mounted on tires and rollers, just as are kilns and driers, and revolve at a speed of about a turn or two a minute. They are usually placed below the kiln, and the clinker falls from the kiln into them. The air for cooling is also drawn through them into 186 ELEMENTS OF INDUSTRIAL CHEMISTRY the kiln by the draft of the latter. They thus serve not only to cool the clinker, out also to preheat the air entering the kiln. The upright cooler, however, is almost universally used in the Lehigh district. It consists of an upright steel cylinder, 8 ft. in diameter and 35 ft. high, provided with baffle plates and shelves. As the clinker falls over these, it meets a current cf air blown in through a perforated pipe running up through the^ center of the cylinder^ and is thus cooled. The clinker is carried from the kiln into these latter coolers by means of bucket elevators, water being run into the buckets to keep them cool. This also suddenly chills the clinker and makes it brittle and easier to grind. After cooling, the clinker is ground in Griffin mills or ball and tube mills. In the case of the Griffin mills, it is usually found more economical to crush the clinker down to pea size by a set of rolls, before feeding to the mills. Kent mills and air sep- arators, and also Kent mills which grind as preparation for the other mills, are used to a limited extent. The clinker should be ground so fine that at least 92 per cent of it passes a sieve having 100 meshes to the linear inch. In order to regulate the set of the cement, since clinker ground alone would set very rapidly, it is necessary to add to it calcium sulphate in some form or other, usually as gypsu m or plaster of Paris. As this can be most easily mixed with the cement during grinding, it is the usual practice to add the retarder to the clinker before the latter is ground, and to grind the two together. The amount of gypsum or plaster of Paris used is usually about 2 or 3 per cent of the weight of the clinker. PLASTER OF PARIS. Plaster of Paris is made from gypsum by heating the latter to a temperature of between 212 and 400° F., when three-quarters of the water of crystallization of the gypsum is driven off, the resulting product being plaster of Paris. 2CaS0 4 2H 2 6 = (CaS0 4 )2H 2 0+3H 2 0. In actual practice the temperatures employed to bring about this reaction are 330 to 395° F. If gypsum is heated above 400° F., it loses all of its water of combination and becomes anhydrous sulphate of lime, the latter being the basis of hard finish plaster, floor plaster, Keene's cement, etc. When plaster of Paris is mixed with water it sets or hardens CERAMIC MATERIALS AND PRODUCTS 187 very promptly, this change being due to absorption of water, forming gypsum again. (CaS04)2H 2 0+3H20 = 2CaS042H 2 0. A pure plaster of Paris will normally harden or set in from five to fifteen minutes after having been mixed with water. If the gypsum from which the plaster is made contains impurities, the set will be much slower than this. Plaster to be used for building purposes must be slow setting. For ornamental use, it must also be white; and since the impurities usually render the plaster slightly colored, it is the common practice to add retarders to the plaster before placing the same upon the mar- ket. The materials used as retarders are usually of a colloidal nature, such as glue, sawdust, blood, packing-house tankage, etc. If a very quick-setting plaster is desired, crystallized salts are employed, such as common salt, sodium sulphate, sodium carbonate, etc. CLAYS. This is the term applied to such natural-occurring earthy materials having the property of plasticity when wet, which on heating to a high temperature become hard and retain the shape of the molded article. Clay is of secondary origin, and, as a rule, results from the weathering of feldspathic rock, such as granite. When found overlying the rock from which it was formed it is termed primary or residual clay. When washed from the original bed and deposited elsewhere it is known as secondary clay. Kaolin. This term applies to the white-burning clays which are composed almost wholly of silica, alumina and chemically com- bined water, with only a very small percentage of fluxing material, such as iron. Their formation is principally due to the weather- ing of pegmatic veins, although in some cases they have originated from granite, quartz, and limestone. When mined they contain a greater or less amount of the parent rock, which is removed by subsequent washing. It occurs quite widely distributed in the United States, east of the Mississippi, while less important deposits are found in Missouri, Utah, and Texas. It is used in the manufacture of white ware, porcelain, tiles, and as a filler for paper. 1 Ball Clay. These clays are white burning, but differ from the kaolins in that they are plastic in character. They find extensive application in the manufacture of white ware, being 188 ELEMENTS OF INDUSTEIAL CHEMISTRY used for the purpose of giving the necessary plasticity and bonding power. They must be as free as possible from iron oxides and possess considerable tensile strength. These clays occur mostly in Florida, Kentucky, Tennessee and New Jersey. Fire clays. This term applies to such clays as are capable of withstanding high temperature. They owe their refractiveness in most part to the large amount of silica and small amount of fluxing agents which they contain. Fireclays vary widely in their physical and chemical properties, showing great dif- ferences in color, plasticity, texture, and tensile strength. They are, as a rule, light in color, ranging from gray to yellowish red. The deposits may be of either primary or secondary origin. They may be divided into plastic and flint clays, the former being plastic when wet; while the latter are hard and flint- like, even when finely ground, but they are very highly refrac- tory. They occur quite widely distributed over the United States. The principal uses of fireclays are for the manufacture of firebricks, retorts, furnace linings, crucibles and terra-cotta; while a special grade is also used for making pots and tanks for glass manufacture. Stoneware Clays. These clays differ from fireclays in that they produce a very dense body when heated at a comparatively low temperature. In many instances, however, they are very refractory, but must possess sufficient toughness and plasticity to be worked on the potter's wheel. In making stoneware it is usually customary to employ mixtures of clays so as to pro- duce certain characteristics in the finished product. Stoneware clays are used in the manufacture of stoneware vessels, as well as yellow ware, art ware, earthenware and even terra-cotta. Terra-cotta Clays. The clays used for making terra-cotta differ quite widely, although most manufacturers prefer a semi- fireclay. Buff burning clays are commonly used, because of the hard body produced on burning. Those suitable for this purpose are found mostly in New Jersey, Pennsylvania, Indiana and Mis- souri. Seiver-pipe Clays. The clays employed for this purpose are quite similar to those used in the manufacture of paving brick. The easily fluxing clays are of advantage here, as the higher iron content aids in the formation of the salt glaze with which the pipes are covered. Some fireclay is usually employed in the mix in order to retain the shape of the tube during the burning. Brick Clays. In making common brick, low-grade red-burn- CERAMIC MATERIALS AND PRODUCTS 189 ing cla3^s are usually employed. The principal requirement is that the clay shall mold readily and burn hard at a comparatively low temperature. Owing to the market price being low it often happens that poor bricks, which are made from local deposits, are used for structural purposes where a better material should have been employed. Pressed brick, on the other hana, call for a higher grade of clay. The physical requirements here are uniformity of color in burning, freedom from warping, absence from soluble salts, with sufficient hardness and low absorption when burned at a moderate temperature. Paving-brick Clays. A great variety of materials are em- ployed for this purpose, although those mostly in common use are made from, impure shales. These shales are widely distributed. They should have a fair degree of plasticity and a good tensile strength. Slip Cloys. These clays contain a large amount of fluxing material which melts at a low temperature, forming a natural glaze of greenish-brown glass. Gumbo Clays. Included in this class are certain fine-grained, plastic and tough clays, which on account of their shrinkage on burning cannot be used for brick making. Their chief use is in the manufacture of railroad ballast. Retort Clays. These are dense burning, plastic, semi-refrac- tory clays, emploj^ed mostly in the manufacture of gas and zinc retorts. Pot Clays. The clays coming under this head are hard burn- ing and are employed in the manufacture of pots for glass making. Ware Clays. These clays are the same as ball clays. Pipe Clays. These clays are the same as sewer-pipe clays. Sagger Clays. This is the term applied to those clays which are used in making the saggers in which high-grade pottery is burned. Portland Cement Clays. In the manufacture of Portland cement a mixture of lime and clay is employed. They may be either true clays or shales. Paper Clays. In order to give body, weight and finish to certain papers, some form of clay is usually employed. The clay, which should be of a plastic nature and of light color, is mixed with the pulp in the beater engine, where it becomes en- meshed. Paint Clays. Many of the clays mix well with linseed oil and form a good grade of paint. The color of these clays varies from 190 ELEMENTS OF INDUSTRIAL CHEMISTRY light yellow to a dark reddish brown, due to the presence of iron oxide and in some instances to that of manganese. The chief clays coming under this heading are the ochers and siennas. USES OF CLAY. In order to show the varied and numerous applications of clays the table compiled by R. T. Hill and ampli- fied by Heinrich Reis will be given : " Domestic. Porcelain (white ware, stoneware, yellow ware, Rockingham ware for table service and for cooking); majolica stove; polishing brick; bath brick; fire-kindlers." " Structural. Brick (common, front, pressed, ornamental, hollow, glazed, adobe); terra-cotta; roofing-tile; glazed and encaustic tile; drain tile; paving brick; chimney-flues; chimney- pots; door-knobs; fireproofing; terra-cotta lumber; copings; fence-posts.' 7 " Refractories. Crucibles and other assaying apparatus; gas retorts; firebricks; glass pots and blocks for tank furnaces; saggers; stove and furnace bricks; blocks for fire boxes; tuyeres; cupola bricks; mold linings for steel castings." " Engineering. Puddle; Portland cement; railroad ballast; water conduits ; turbine wheels; electrical conduits; road metal." " Hygienic. Urinals; closet bowls; sinks; washtubs; bath- tubs; pitchers; sewer-pipe; ven bila ting-flues ; foundation-blocks; vitrified bricks." " Decorative. Ornamental pottery; terra-cotta; majolica; gar- den stands; tombstones." "Minor Uses. Food adulterant; paint fillers; paper filling; electric insulators; pumps; hilling cloth; scouring soap; pack- ing for horses' feet; chemical apparatus; condensing worms; ink-bottles; ultramarine manufacture; emery wheels; playing marbles; battery-cups; pins; stilts and spurs for potters' use; shuttle-eyes and thread-guides; smoking-pipes ; umbrella-stanas ; pedestals; filter-tubes; caster wheels; pump-wheels; electrical porcelain; foot-rules; plaster; alum." BUILDING BRICKS. There are many forms of building bricks, including common building bricks, pressed bricks, glazed bricks and enamel bricks, but as space does not permit a complete description of each, only the manufacture of common building brick will be given. The processes involved may be divided into the preparation of the clays, the molding, the drying and the burning. Preparation. Since only a few clays can be used directly as mined it becomes necessary to subject the material to weathering CERAMIC MATERIALS AND PRODUCTS 191 agencies. This is done by spreading the clay over the ground in a thin layer of from 2 to 3 ft. in depth, and allowing it to remain thus exposed for a considerable period, lasting in some cases a year or more. In order to hasten the process, however, some clays are disintegrated by artificial means, for which purpose crushers, edge runners, disintegrators and roller mills are employed. The grinding is usually done on the dry clay, although in some cases the wet clay is used and the process is known as tempering. Ring Pits. These are pits about 25 ft. in diameter and from 2 to 3 ft. deep. A heavy iron wheel is arranged by means of gears so that it travels in the pit and causes a thorough mixing of the mass. The operation lasts from five to six hours, at the end of wnich time the clay is ready for the brick machine. Pug Mills 1 These machines are of different shapes and capacity, but are all provided with blades which cut up the clay, produce a thorough mixture and pass it along to the discharge end. They do not take up as much room as the ring pit and are much more readily handled. Molding. The simplest form of molding consists in pressing the soft clay or mixture into wooden frames which have been dusted with sand to prevent sticking. This operation is done either by hand or by machine and is known as the soft-mud process. In the so-called stiff -mud process the clay is tempered with much less water. The prepared clay is forced through a die in the form of a rectangular bar, which is then cut into lengths of the brick. The machine employed for this purpose is provided with an auger screw and runs in a cylinder which tapers at the end to the size of the die. Dry pressing is sometimes done as well as semi-dry pressing. In either case the prepared clay is forced with great pressure into steel molds. Drying. After molding, the bricks must be dried before burning. This may be accomplished in several ways, the simplest being to spread the bricks over a smooth flat floor and allowing them to dry in the sun. Pallet driers are covered frames on which the bricks are placed as they come from the machine. Drying in the air has the disadvantage in that it cannot be used in cold or damp weather. To overcome this many brickmakers are employing drying tunnels. In this method the green bricks are placed on cars and run in at the cooler end of the tunnel and gradually pushed along to the warmer end. These tunnels are built in a variety of ways, but when possible the waste heat from other operations is employed. 192 ELEMENTS OF INDUSTRIAL CHEMISTRY Burning. The bricks having been thoroughly dried are placed in kilns and heated to a comparatively high temperature or " burned." The temperature and time of heating depends upon the kind of clay employed and the degree of hardness desired. The kilns may be either " up-draft ,; or " down-draft. " In the former system the heat from the fire passes into the body of the kiln and up through the ware, finally escaping at the top. The heat in the down-draft kiln enters at the top, passes down over the ware and escapes through flues at the bottom. Continuous or ring kilns are also employed. They consist of a series of chambers arranged in the form of a circle, connected with each other and with the stack by means of a series of flues. The fire is built under the chamber which is to receive the highest temperature ; from here the heated gases pass to the next chamber and so on to the freshest charge. In order to utilize the heat from the cooling bricks, after they have reached their maxi- mum temperature, the air supply to the fire is drawn through the chambers containing the thoroughly burned and cooling bricks. Sewer-pipe Manufacture. Most sewer-pipes are made from shale, which after crushing is mixed with the necessary amount of plastic material and made into the desired shape by a special form of press. The drying and burning is then carried out in a somewhat similar manner as that given for brick. Hollow Structural Material. Included in this classi- fication are fireproofing terra-cotta lumber, hollow blocks and hollow bricks. The fireproofing materials are those which are employed in floor arches, partitions, and wall furring for girders and columns. Terra-cotta lumber is a soft and porous material produced by mixing sawdust with the clay and subsequently burning it out. This being soft can be nailed the same as lumber. Hollow block and hollow brick are used for outside walls. FIREBRICKS. Most of the firebricks on the market are made from a mixture of several clays to which has been added a certain amount of ground firebrick or quartz. They are made in many shapes and vary greatly in hardness and their degree of refractory power. The burning is almost universally conducted in down-draft kilns. TILE. Under this heading comes roofing tile, floor tile and wall tile. They are made in a variety of ways and from a variety of materials. Some are made in a porous condition while others are colored and highly glazed. CERAMIC MATERIALS AND PRODUCTS 193 POTTERY. This heading includes a great variety of prod- ucts ranging from the cheap earthenware, such as flower-pots, to the most delicate porcelain vase. In the manufacture of pottery there are certain operations which are common to all, but with the higher grades much more care and a larger number of details are necessarily involved- The general operation consists in the preparation of the raw material, tempering, molding, drying, biscuit burning, dipping, glost-burning, and decorating. STONEWARE. This class of material is made from low- grade plastic clay, being porous in character, red to cream in color and may or may not be glazed. If the object is to receive a glaze, it is usually developed with the body so that after drying the object is in a proper condition for the application of the glaze. Slip-clay, which is largely used for this purpose, melts to a brown glass at the temperature at which the ware is burned. Salt glazing is a very simple method and is in com- mon use for this kind of ware, although it is applied more especially to sewer-pipe. The goods having been placed in the kiln and the maximum temperature reached, the salt is thrown imo the fire. The high temperature causes a volatilization of the salt which on coming in contact with the clay unites with it, forming a glaze on the surface of the ware. In yellow ware the object is burned to develop the body, after which the glaze is applied and the ware heated a second time. WHITE WARE. Included in this class are those products having a white or nearly white body and usually glazed. Mix- tures consisting of kaolin, ball-clay, quartz, and feldspar are the materials which are employed, and these are selected with the idea of their white-burning qualities in view. PORCELAIN. Prior to the sixteenth century, this term was used to designate those objects made from mother-of-pearl. At the present time, however, the same materials are employed for making porcelain as those used for white ware. Great care, however, must be exercised in their selection and the mixtures so proportioned as to give a hard and translucent body. That in which spar is used for the flux is known as hard porcelain and is bluish white by transmitted light, while that fluxed in part with calcium phosphate, known as bone china, is yellow by transmitted light. GLAZES. For all pottery, except hard porcelain, the ware is first burned in the biscuit kiln, forming porous porcelain, then glazed and burned again in the glost-kiln. The glazes 194 ELEMENTS OF INDUSTRIAL CHEMISTRY consist of mixtures of acids and bases so combined that they will melt to a glass at the temperature of burning. It is very important also that the coefficient of expansion agrees with the body of the ware, otherwise a defective glaze will be the result. GLASS. Glass is an amorphous product of fusion, differing widely in composition. Ordinarily it is considered as a mix- ture of an alkaline silicate and the silicate of one or more bases, the alkali being sodium or potassium, the base calcium or lead, while sometimes all four elements enter into its compo- sition. While this is true of nearly all commercial glass, it must be noted that at Jena and elsewhere glasses have been made free from alkali, that borates and phosphates have been substituted for silicates, and that many elements, such as zinc, barium, magnesium, and antimony, have been substituted for lead and lime, so that it is practically impossible accurately to define glass. Technically, transparent glasses are divided into lime glass or lead glass according to the presence of these elements. The term flint glass, which originally meant a pure lead potash glass, is now often applied to all clear transparent glass. Sometimes the lime glass is called lime flint or German flint. Bottle and window glass are impure forms of lime glass. White or "'opal " glass and colored glass are glasses to which materials have been added to produce the color effect. The following are the chief raw materials used in making glass : Silica. Silica is usually introduced in the form of sand, which may vary in purity, according to the source and care in preparation. The chief impurities in sand are iron, alumina, and organic matter. The presence of a small amount of alumina does not injure the glass, but iron acts as a coloring agent, pro- ducing a green of more or less intensity, depending on the quan- tity present and the state of oxidation. For the finer glass, therefore, a sand as free , from iron as possible is required, while for more common ware, such as green bottles, a much larger quantity is permissible. Sand from Berkshire, Mass., is prac- tically free from iron, while that from Pennsylvania and West Virginia often contains less than one-tenth of one per cent. Sand from New Jersey usually has a much higher iron content. The sand must be of uniform size, not too coarse to prevent reaction with the other material, not yet so fine as to cause the reaction to take place too violently and cause excessive foaming CERAMIC MATERIALS AND PRODUCTS 195 during the melting. Natural silicates, such as feldspar, are sometimes used as a source of silica, because of the alumina and alkali which they contain. Slags from metallurgical proc- esses have been used for common ware with va^dng success. Alkali Metals. Sodium-carbonate (soda ash), produced either by the Solvay or the Leblanc process, is the chief source of soda and is obtained from the trade in a pure condition. Sodium sulphate (salt cake), owing to its cheapness, is also used in the manufacture of plate and window glass. Its use requires the addition of carbon as a reducing agent and is attended with many difficulties not met with when the carbonate is used. The amount of carbon added is much less than that called for by theory and it is impossible to give an exact explanation of the reaction. Sodium nitrate (Chile saltpeter), either as it comes from Chile (95 per cent) or refined for the better ware, is used as an oxidizing material to destroy organic matter and to change the iron to the ferric condition. Potassium carbonate (pearl ash, salts of tartar), usually hydrated, containing from 80 to 85 per cent potassium carbonate, is the chief source of potas- sium in the glass industry, sulphates and chlorides being the chief impurities, In some European factories crude pearl ash from the sugar refineries is used in the cheaper kinds cf glass. Potassium nitrate is also used as an oxidizing material. Alkali Earths. Calcium is introduced as a carbonate, oxide or hydrated oxide. Limestone occurs in nature of suf- ficient purity for use after simply grinding. Burnt lime is also used, but more frequently the hydrated oxide. The advantage of the different forms of lime is an open question, some works preferring one, some another. The advantage of burnt lime is the saving in heat by the removal of the carbon dioxide before entering the furnace, while on the other hand the liberation of carbon dioxide from the carbonate helps stir the glass during the melting process. Iron in all glass-making materials is harm- ful, while magnesia makes the glass hard and more difficult to " plain/' though many American factories use a lime high in magnesia content without any apparent disadvantage. Barium is sometimes used in the form of sulphate together with carbon, bat more generally as a carbonate either natural or prepared. It produces a glass high in refractive power and is used for many optical purposes. Heavy Metals and Acid Radicles. Lead is used generally as red oxide or litharge to impart brilliancy and to produce 196 ELEMENTS OF INDUSTRIAL CHEMISTRY glass of high refractive power. Red lead, because of the oxygen which it liberates, is preferred to litharge. Freedom from metallic lead and discoloring metallic impurities, such as copper and iron, is required. Zinc is used as oxide to replace lime or lead, especially in the modern heat-resisting glasses. It is also largely used in opal glass. Boric acid and borax are used in optical and heat-resisting glass as well as in colored glasses. Phosphate of lime, bone ash, is used to produce opalescence or opacity, depending upon the quantity. Bone ash, unless it is present in large quantity, requires " reheating " to bring out the opal- escence. Feldspar is used as a source of alkalies and alumina. Used with fluorspar it produces opal glass. Fluorspar used with feldspar or alumina produces opal glass. Iron and metallic sulphides (lead and zinc) are the chief harmful impurities. Cry- olite, sodium aluminium fluoride, used alone, produces dense opaque glass, but owing to its solvent action on the clay pots other materials are taking its place. It is largely used in making opal glass by the tank method. Arsenic as white oxide is used in opalescent and opal glass and in enamels. Tin oxide is used to a limited extent in colored glasses and in enamels. Antimony as oxide, sulphide, or metal is used in colored glasses and the sulphide is emoloyed in tank glass to " improve the color." Coloring Materials. Uranium, usually as sodium uranate, is used to produce a peculiar yellow fluorescent glass. When in the ferrous state, iron colors glass green, and yellow when in the ferric condition. The temperature of the furnace, how- ever, materially affects the state of oxidation of the iron, a high temperature changing it from yellow to green. As a colorant it is usually added as red oxide or iron scales. Chromium produces green and greenish-yellow glass. The oxide Cr203 is very hard to dissolve; hence potassium dichromate or other metallic chromates are used. Manganese. Black oxide, Mn02, is the most used of all the coloring oxides. In large quan- tities it produces black, and in less amount purple to light pink color. It is used to correct the color effect of iron, which is always more or less present in glass material. It acts as an oxidizing agent also. The quantity of manganese to be used depends on the amount of iron present and the temperature of the furnace, as the hotter the furnace the more manganese is required. The heat " burns out the color." Nickel, as oxide, is used in a very limited way. European practice substitutes it for manganese in some glasses, but American factories CERAMIC MATERIALS AND PRODUCTS 197 have not found this satisfactory. Cobalt, as oxide or smalt, is employed in giving an intense blue color. The blue from cobalt shows purple by transmitted light. Gold as chloride or purple of Cassius is used to produce a ruby color. Copper in the cuprous form produces red, in the cupric it produces a peacock-blue color. Selenium is used to produce a red color. Cadmium sulphide forms a lemon yellow color in lead-free glass. Both cadmium and selenium are usually added after the glass has been melted in the pot. Carbon is used as a reducing agent in sulphate glass. In the form of coke, oats, bark, and other organic matter it produces an amber color in lime glass. Pot Furnaces. The glass mixture is melted in clay cru- cibles or pots known as pot furnaces. These furnaces are either open or closed, and may be fired either direct, regenerative or recuperative. The direct-fired coal furnace is still used, but the regenerative furnace is the most satisfactory and economical of pot furnaces. In this type the burnt gases from the furnace are made to pass through firebrick checker-work flues which then become highly heated. The direction of the draft is then reversed by suitable dampers, and the incoming air and gas are led through while the burnt furnace gases go to heat another checker work which has become cooled by the incoming air and gas of the previous run. Thus the burnt furnace gases give up then waste heat to the checker work, which in turn gives it up to the incom- ing gas and air. In practice this reversal of draft is made every twenty or thirty minutes. In the recuperative furnace there is no reversal of draft, but the hot burnt gases pass through clay tubes which by conduction give up their heat to the incoming air and gas. This furnace is used abroad, but has not been adopted widely in America. Tank Furnace. The introduction of the tank furnace marked an epoch in the glass industry. The batch is put in a shallow fireclay tank covered with a refractory arch of silica brick and heat applied to the surface of the batch. The simplest form is intermittent or " day tank." The batch is shoveled in, the work holes are closed and heat is applied, either oil or gas being used. When the glass is " plain " the heat is reduced, the work holes opened, and when cooled sufficiently the glass is worked. These tanks are filled in the afternoon and are ready to work the following morning, hence the name. To obviate the loss of heat by this method continuous tanks are used. These are usually much larger than the day tanks and are usually divided 198 ELEMENTS OF INDUSTRIAL CHEMISTRY into compartments by fireclay obstructions. The batch is filled in at one end of the tank, and after melting flows under the obstruction to the working end. As fast as the glass is worked out, a new batch is introduced so that the melting and working go on continuously, thus maintaining a nearly constant level of glass. The continuous tank is the most economical form of glass furnace, and wherever large quantities of glass are made, it is used. The glass produced is not so good in color as that made in closed pots, so that for the finest ware or where small quan- tities are made, pot furnaces are still employed. Pots vary in size from those holding but a few pounds (known as monkeys) to those holding several tons. The life of a pot varies greatly. It may be broken from the outside by a sudden change of temperature, or by one of the many other causes, but the natural end of a pot is by corrosion from the inside. This corrosion varies with the different kind of batches. Some pots may last but a few weeks, while others may remain perfectly good for a year. Sometimes a pot is taken out before it breaks because it is introducing small pieces of clay (stones) into the glass. Melting Process. The batch, made by weighing and carefully mixing the various materials together with some broken glass (cullet), is filled into the pot and the stoppers luted on. After this charge has melted more material is added until the pot is full; usually one such " topping " is sufficient to do this, but sometimes it must be repeated. Casting. Plate glass is made in open pots that can be removed from the furnace and their contents poured on a casting table and then rolled to the desired thickness by a metal roller. The plate of cast glass is then transferred to a kiln or annealing oven (lehr) and gradually allowed to cool. After the plate, which is rough and uneven, is cooled, it is fastened to a table with plaster of Paris, ground with revolving iron rubbers and sand, first coarse, then finer until the surface is even and smooth. It is then polished by felt-covered rubbers and rouge paste. The plate is then reversed and the other side ground and polished. Unpolished plate glass, known as rough plate is made simi- larly to regular plate glass excepting that the glass is taken from the pot in large steel ladles and poured on a table between guides. The table or the roller often have a design on them, thus pro- ducing ornamental effects in the glass. Wire glass is rolled plate in which wire has been imbedded CERAMIC MATERIALS AND PRODUCTS 199 during the rolling process. Special care is necessary to prevent this glass from flying apart, owing to unequal expansion of the glass and wire. Polished plate glass of opal and black glass have been made and used for table tops, sanitary wall, and for other purposes. Pressing. Glass is gathered on the end of an iron rod (punty) by revolving it rapidly in the molten glass. It is then carried to the workman (presser), who cuts off with shears the amount desired and allows it to drop into the mold. A metal plunger is then forced into the mold and forces the glass to fill the space between the plunger and the mold. When the glass has become firm, the plunger is withdrawn, the mold opened and the article either sent direct to the annealing oven or first reheated in an auxiliary furnace (glory hole) to remove mold marks or to alter the shape. Press molds are made of cast iron and so constructed that the pressed article can be easily removed. The temperature of the mold and plunger is regulated by streams of air blown against them, the expansion and contraction of the mold being carefully controlled by the workman. The plunger is usually operated by hand power, but for some purpose steam or compressed air is used. Blowing. Window glass until recently was entirely hand made, but machines are being introduced which are replacing hand labor. In the hand-made glass the workman gathers a lump of glass on the end of a hollow iron pipe and after cooling it a little, introduces it into the molten glass and gathers more. This is repeated until he has sufficient for his purpose. Then by blow- ing and swinging and further manipulation, he produces a large cylinder of glass. The surplus glass is cracked off the ends of the cylinder and it is cracked lengthwise for the next operation. The cylinder is then gradually heated in a flattened oven and as it begins to soften it is flattened by rubbing on a flat stone, after which it is transferred to the annealing oven and gradually with- drawn from the heat. Window glass is now generally made in continuous tanks, which have replaced the old open-pot furnaces. Machine-made window glass is made by immersing a blow- pipe in molten glass, introducing compressed air and gradually withdrawing the blowpipe from the molten glass. By carefully regulating the speed of withdrawal and the amount of air intro- duced cylinders of any length are made and flattened as usual. 200 ELEMENTS OF INDUSTRIAL CHEMISTRY Crown Glass. Crown glass, once the chief source of sheet glass, is now made only for special purposes, such as microscope slides and cover-glasses, where a surface free from imperfections is required. It is made by blowing a ball of glass, attaching to the side away from the gathering iron a hot iron rod (punty) and cracking it off the gathering iron. The glass is then heated and rapidly revolved until it forms a large flat disk, when it is annealed and selected. Hollow Ware. Hollow ware is shaped in molds of metal or wood. The glass is gathered on a hollow pipe, and after shaping by rolling on a polished plate (marver) or revolving in a hollow iron or wooden block it is blown into the mold and takes its shape. In the case of chimneys, tumblers and other cylindrical articles the glass is revolved in the mold and shows no joint or mold mark. Such molds are lined with charcoal or special paste which enables the glass to be turned. In the case of lan- tern globes or articles with raised or sunken patterns the glass is blown without turning and takes the exact impression of the mold (iron mold). Bottles. Bottles are made by blowing in a mold, and after reheating the neck is finished with a special tool. Optical Glass. Optical glass is usually made in a one-pot furnace and differs from other glass in being allowed to remain in the pot until it has become cool. The batch is melted and after it has become " plain " is stirred with a burnt fireclay rod to produce uniformity and destroy striae. Then the glass is quickly cooled until it loses its fluidity, and after this it is very gradually cooled. When cool the pot is broken open and the glass sorted. Only a small portion is fit for use. In recent times advances have been made in this kind of glass, especially at Jena, where many of the optical glasses have originated. Colored Glass. Amber is produced by the addition of carbonaceous matter, e.g.-, grain, coke, coal, sawdust, or other organic matter, to a lime glass. The intensity and shade of color depend on the kind and quantity of matter added. Amber is also produced by sulphur and certain sulphides. Black is pro- duced by an excess of coloring matter such as manganese, cobalt, or iron. Blue can be produced by cobalt or copper. When produced by cobalt it is dark, showing purple by transmitted light. The copper blue is a less intense color, bordering on the green. Canary, a special color produced by uranium. Green, CERAMIC MATERIALS AND PRODUCTS 201 Chromium or iron alone will produce a green glass, though it is usually made by combining several oxides, such as cop- per and iron or chromium and copper. Gray, H London smoke." When substances producing complementary colors are added to the same glass a gray color is produced. Opalescent. Glass resembling the opal is produced by the addition of arsenious oxide and calcium phosphate. When this glass comes from the pot it is colorless, but on allowing it to cool and then reheating, the opalescence is developed. If the cooling is carried too far the opalescence is lost and a milky effect produced. Opal or white opaque glass was originally produced by the addition of cryolite or an excess of calcium phosphate (bone ash). Mix- tures of fluorspar and minerals containing aluminium, such as feldspar, have been substituted and recently artificial compounds bearing fluorine, such as aluminium fluoride, and sodium silico fluoride, have been used. Purple is produced by manganese dioxide. Red or Ruby is produced by gold, selenium or copper. In the use of copper great care is required to have the copper in the right condition of division and reduction. The glass, as it comes from the pot, is usually light green in color but on cooling and reheating an intense red (such as is used for railroad signal lights), is produced. The color, however, is usually too intense for use alone so it is " flashed " by gathering a small quantity of the ruby glass and then covering it with sufficient clear glass to make the desired color. " Flashing " is frequently resorted to in making colored sheet glass. Gold ruby is worked very much the same as copper ruby, excepting that it can be produced sufficiently light in color to be used alone, though flashing is often used to reduce the intensity. Gold ruby as it comes from the pit is colorless or yellow, but when properly cooled and reheated develops the ruby color. Decorated and Cut Glass. Decorated or painted glass is produced by painting on the glass with easily fusible glazes. These glazes are finely ground, mixed with oil and applied to the object and after drying it is put in a kiln and heated sufficiently to fuse the glazes. Cut glass is usually a highly refractive lead glass which when cut shows a beautiful play of prismatic color. The design is first marked out with red paint and then " roughed " with sand on an iron wheel. It is then " smoothed "ona fine- grained stone wheel and finally polished on a wood wheel with putty and pumice. Of recent years this last operation has been replaced by dipping in strong hydrofluoric acid. Glass is obscured 202 ELEMENTS OF INDUSTRIAL CHEMISTRY or roughed by means of sand blast or by dipping in a bath of alkaline fluorides. In etching designs on glass a print is made on paper, using a protective wax as ink. This print is transferred by rubbing it upon the glass. The paper is removed, leaving the ink design on the glass. The inside of the article is now protected by wax and then immersed in hydrofluoric acid. The acid etches the part exposed, but does not affect the parts protected by the ink or - wax. The wax is then removed by hot water, leaving the finished design. Often the glass is first obscured by the sand blast and the design etched in the roughened surface. Annealing. In all the processes of manufactuer, with bat a few exceptions, the finished articles while still hot are taken to an oven and gradually cooled. If glass is cooled suddenly it develops great internal strain so that it is likely to fall, to pieces under change of temperature or when its surface is scratched. To obtain glass free from strain it must be " annealed " or cooled gradually. This is accomplished either by placing the finished article in a heated room and allowing the fire gradually to die out (kilns or ovens) or by gradually withdrawing the article from the heat (lehrs). The former method is used for heavy articles such as carboys, plate glass, blanks for cutting, and optical glass, while the continuous lehr is used for lighter ware. Recently, however, such improvements have been made in con- tinuous lehrs that large articles and even plate glass can be successfully annealed in them. The time of annealing varies from a few hours in the lehrs to a week or more in the kilns, depending on the thickness and composition of the glass. In annealing optical glass the cooling is carefully controlled and of long duration, as any sign of internal strain renders it unfit for use. CHAPTER VIII PIGMENTS DEFINITION. Pigments are mineral or organic bodies used to give body or impart color to a base by admixture with its substance. They are usually insoluble in water, oils or other neutral liquids. It is desirable that the pigments be opaque in order to give good " covering power," or that they possess a high tinting value. The color of a pigment depends upon the amount and kind of light that it reflects and should entirely conceal the surface to which it is applied. Some pigments have sufficient body to be used alone, while others can be employed only in conr- bination. In order to apply these pigments they must be mixed with some form of vehicle that binds them to the surface upon which they are placed. A pigment or mixture of pigments so bound to a surface may be applied for protective or decorative purposes or may serve as both. APPLICATION. Protective paint, by which is meant paint used for the purpose of protecting the surface to which it is ap- plied, is relatively new. In Europe building construction was of such a character, and is largely so to-day, that paint is not used to any great extent on the exterior of dwellings. Only in a pioneer country like America where domiciles were made of wood, was it found necessary to apply an exterior coating to preserve the wood. For decorative and preservative effect, we find more evidence of the early use of paint in England than we do in any other country. There are items of expense in the reign of Edward I showing the use of paint as early as the year 1274. Up to the latter part of the fourteenth century, however, oil painting for artistic purposes was not an exact art. To Hubert and Jan Van Eyck, two Dutchmen, belongs the credit of first having made public their manner of oil painting by means of pigment ground as near as we know in linseed oil. Occasionally we hear a complaint that the pigments made nowadays are not as good as those that were made in former 203 204 ELEMENTS OF INDUSTRIAL CHEMISTRY years, and the poverty of oar pigments is the cause of the early decay of many of our paintings. An error of this kind deserves correction, for the art of manu- facture of colors has never reached a higher plane than it has at present, but to the ignorance of the painters and to the greed of paint-makers must we attribute the fugitiveness of our paint- ings. As nearly as can be determined there existed between the twelfth and the seventeenth centuries, at most nine or ten pig- ments. To-day we have 215 or more, 200 of which ought never to be used for permanent artistic painting. When we see a painter with a pot of paint and brush paint- ing either a steel or wooden structure, we imagine without further thought that that is the use to which most paints are put. As a matter of fact, paints and colors are used in enormous quan- tities in the arts and sciences for other than decorative or pro- tective purposes. The following is a list of the purchases of the Bureau of Engraving and Printing, Washington, D. C. for the year 1910, showing the actual contract for 1,599,900 lbs. of pigments: Lbs. White 802,200 Black 297,500 Blue 52,000 Green 180,000 Red 68,200 Yellow 200,000 1,599,900 These pigments are identical in every respect with those used for general painting, and yet all these pigments are used for the purpose of printing the currency and the postage stamps of this Government. The printing ink industry in the United States consumes enormous amounts of paint. In some instances the paint is ground in a varnish made of linseed oil, but for book and news- paper ink linseed oil is not used, but resinous mediums which act as a binding material for the pigment. The floor oil cloth and table oil cloth industries are also enormous users of paint in the strict sense of the word; and while it is true that the mixtures which they make differ from the house painters' mixtures, the principle involved is identically the same as that of ordinary paint. PIGMENTS 205 The shoe and leather industries are users of paint materials in large quantities, for making patent and harness leather, and so is the wall-paper industry, the window-shade industry, the rubber industry, and the cement industry, all using for their color effects the same pigments that are used for ordinary painting. In the strict sense of the word, paint which is used on con- crete, steel or wood, is an engineering material, and serves a pur- pose which is far more valuable than we imagine. The pigments used in ordinary general manufacture of paints are as follows: Whites White lead Sublimed white lead Zinc oxide Lithophone Barytes Whiting Gypsum China clay Asbestine Silica Zinc white lead Satin white Yellows Chrome yellow Yellow ochre Cadmium yellow Oroiment Litharge Gamboge Indian yellow Blues Ultramarine Prussian blue Smalt Cobalt blue Copper blue Chinese blue Violets Ultramarine Reds Red lead Chrome red Red ochre Venetian red Vermilion Realgar Antimony red Carmine Greens Ultramarine Brunswick green Chrome green Guignet's green Copper green Arsenic green Blacks Lamp black Drop black Graphite Ivory black Oranges Orange mineral Chrome orange Antimony orange Browns Lnibers Vandyke brown Sepia Many other pigments, both natural and artificial, are in use, but are not used to such an extent as the list given above. A large class of bodies known as " Lakes " are also used extensively and will be taken up in order in this chapter. WHITE LEAD. The name white lead applies to a compound consisting of carbonate of lead and hydrate of lead in chemical union. It is a commercial name, and is distinctive of a definite product which has been upon the market for hundreds of years. 206 ELEMENTS OF INDUSTRIAL CHEMISTRY For the manufacture of white lead a very pure pig lead is usually needed, especially in such processes as do not result in the removal of some of the impurities at some point in the manu- facturing process. There is probably no chemical product in so general use for which more patents have been taken out claiming to revolutionize processes of manufacture. Some of these have been tried on a commercial scale and some have not passed beyond the issuance of patents. Most have been ineffective. To-day in the United States there are four processes in prac- tical commercial operation. These are the Dutch, the Carter, the Matheson and the Rowley or Mild process. There is also said to be an electrolytic process in operation in Boston, but practically no information is obtainable regarding it. All of these processes except the Mild process use acetate of lead as an assist- ing agent in the process. The great bulk of white lead in the United States is manufactured by the Dutch process. Next in volume of product is the Carter process. The Dutch Process Corroding. To change pig lead into white lead, it is subjected to the corroding gases produced by the fermentation of refuse tan bark. Special buildings are provided for this purpose, known as " corroding houses." These " corroding houses " are build- ings about 30 ft. high with floor-space frequently about 20X40 ft. The floor of this building may be of ordinary earth, and upon it a layer of spent tan bark is placed about 20 ins. thick. On this is placed a layer of corroding pots, Fig. 71, covering the entire floor, except around the edges, where tan bark, known as " banking," is packed. In each corroding pot about half a pint of weak acetic acid, containing about 2 \ per cent of glacial acetic acid, is placed. These pots are then filled with lead buckles. On top of the pots a layer of boards is placed, and on these boards another layer of tan bark. Another layer of pots is placed on this second layer of tan bark; these pots are filled, as with the first layer, and other layers are placed on this until there are from eight to ten layers or " tiers " in the stack. For the corrosion of lead to white lead, a certain amount of ventilation is necessary so that the moisture can be carried off from the stack. This is done in various ways. A typical way PIGMENTS 207 is to provide a wooden pipe that shall run from each tier up near the center of the stack to the top. On the top of this pipe is an outlet which may be opened or closed as may be desired. Chemical Change. When the stack has been built, the tan bark commences to ferment, liberating carbon dioxide, and generating considerable heat. The heat causes the acetic acid to evaporate and its fumes attack the lead buckles. In a short Fig. 71. time these buckles are covered with a layer of basic acetate of lead. The carbon dioxide generated by the fermentation of the tan bark then decomposes the basic acetate of lead, pro- ducing white lead or basic carbonate and liberating neutral acetate of lead, which has a strong solvent action upon lead itself. This fermentation and corrosion of the lead continues until most of the lead is changed into white lead. At times the heat gen- erated by the fermentation of the tan bark rises rather high, sometimes exceeding 180° F. Grinding. When the fermentation of the tan bark has 208 ELEMENTS OF INDUSTRIAL CHEMISTRY practically ceased and the corroding action is nearly finished, the " stack," as the whole body of tiers is called, is taken down or " stripped," Fig. 72, commencing at the top. The corroding operation takes from 100 to 130 days. When the stack is stripped, it is found that the metallic lead that was originally in the pots has been changed to a white, porcelain-like material, which is white lead. All of the metallic lead originally present has not been corroded, however. It is necessary, therefore, to remove the remaining metallic lead, and to grind the white lead finely Fig. 72. in order to make it a suitable paint material. This work is done largely in iron machinery that is air-tight, so that the dust formed will not escape. The corroded lead from the stacks is first passed through a screen, covered with sheet-steel perfo- rated with rather large holes. This screen tumbles the lead about, breaking up the white lead sufficiently, so that it passes through the holes in the steel covering, while the large pieces of metallic lead pass out as tailings, to be remelted for further use. This coarse white lead is then passed through rolls and fine screens to remove the finer metallic lead; following which, the white lead reaches the condition known as " unground carbonate " PIGMENTS 209 and becomes suitable for water-grinding. The unground car- bonate is mixed with water and ground with high-speed mill- stones, so that every particle will pass through fine silk bolting cloth. The white lead in water after grinding is also floated a long distance so that any coarse and unground particles may settle out. The water containing the white lead is pumped into large tanks and allowed to settle. Pulp Lead. The thick mixture of white lead and water, called " pulp," which settles to the bottom, is pumped onto drying pans made of copper and dried with exhaust steam, the product being the dry lead of v commerce. This dry white lead is mixed with linseed-oil and ground through burr mills to produce a white lead paste, which is the commercial white lead in oil. Sometimes, the white lead pulp is mixed directly with refined linseed-oil in special mixers, the oil combining mechanically with the white lead, producing white lead in oil of commerce, the water being eliminated. The Carter Process Chemically, white lead manufactured by the Carter process is the same as when manufactured by the Old Dutch process. In each case pure metallic lead is converted into basic lead acetates, which are acted upon by carbon dioxide to form basic carbonate of lead, or white lead. The Carter process starts with pig lead, a grade commercially known as " corroding," which is as free as possible from bis- muth, antimony, and other impurities. The first step is to atomize the metallic lead, the method being substantially the same as atomizing a liquid in the ordinary nasal atomizer. The pig lead is melted in a kettle to which is affixed a nozzle through which the molten lead flows by gravity. At the outlet it is struck by a jet of superheated steam which atomizes or blows the lead into very fine particles which are very slightly oxidized. In some text-books on paints and paint pigments, the Carter process is referred to as " the quick process." This is a little misleading, for while the time of corrosion is cut down from about 120 days by the Dutch process to about fifteen days, the mass of metallic lead exposed to the corroding agencies is re- duced in much greater proportion. The powdered lead, in charges of about 4000 lbs. is then 210 ELEMENTS OF INDUSTRIAL CHEMISTRY Fig. 73. placed in wooden cylinders, Fig. 73, about 6 ft. in diameter and 10 ft. long, which revolve very slowly on their own horizontal axes. The metallic lead in the cylinders is treated with dilute acetic acid (vinegar) and carbon dioxide (carbonic acid gas). A very weak solution of the acetic acid is sprayed into the cylinders at intervals. The carbon dioxide is admitted through the center of the head and is produced by the perfect combustion, in the presence of an excess of oxygen, of carefully selected coke. The coke is burned under boilers so as to utilize its calorific value. The lead in the cylinders is kept moist with water during corrosion and a certain per cent of oxygen (air) passes into the cylinders with the carbon dioxide. The action of the acetic acid upon an excess of metallic lead and lead oxide produces various basic lead acetates. The carbon dioxide acting on these basic acetates forms basic lead carbonate or white lead. The acetic acid, freed by the action of the carbon dioxide on the basic acetates, acts again on the excess of metallic lead and lead oxide and is again liberated, and so on in cycles until corrosion is complete. As the cylinders slowly revolve, the pulverized lead is car- ried upward on the interior of the cylinder and rolls down to the bottom, exposing new particles to the corroding agencies. The heavy mass also performs most efficiently the functions of a tube mill in grinding the carbonate off the metallic particles as fast as it is formed and reducing it to an exceedingly fine powder. By the Carter process corrosion is complete in about fifteen days. No artificial heat' is required, sufficient heat being gen- erated by the chemical combination to keep the contents of the cylinder at about 145° F. during corrosion. At the proper stage, the cylinders are emptied and the white lead is then washed and agitated in water, removing any traces of acetic acid or acetate of lead. It is then floated in water to remove the small particles of coarse lead, if any, and is then pumped into storage tubs, where the lead settles in the form of PIGMENTS 211 a heavy pulp. After evaporating the water from the pulp, commercial dry white lead results. For general use, white lead is put up in stiff paste form to facilitate mixing into paint. This paste consists of 92 per cent of hydrated carbonate of lead and 8 per cent of pure raw linseed oil. This paste is produced in two ways: one by chasing, mixing and grinding in a double set of heavy buhr-stone mills,* dry white lead and pure linseed oil; the other by mixing the lead pulp (lead and water) with linseed oil in what is known as pulp machines, the white lead taking up the oil to the exclusion of the water and becoming " lead in oil," which is then chased and mixed and run through the heavy buhr-stone mills. The pulp process simply does away with drying the lead pulp, and the only purpose of the heavy grinding is to secure complete incorporation of the lead and the oil. Properly ground lead in oil, ground either dry or from pulp, does not contain more than 0.5 per cent of free moisture. The last step in the Carter process is to convey the paste white lead from the mills to storage tanks, each of 75 tons capacity, there it is allowed to stand for several days before it is drawn off and filled into kegs. The pressure of the lead in these tanks completes a perfect saturation of the lead with the oil and forms a very smooth, unctuous paste. The Matheson Process This process is a development of the process usually attached to the name of Thenard, who introduced it at Clichy, France. It involves the use of a solution of basic acetate of lead into which carbonic acid more or less purified is conducted. The carbonic acid combines with the basic lead, removing it from its combina- tion with the acetate of lead, the carbonate compound separating as a precipitate of white lead. The white lead thus produced is removed by filtration, washed with water and dried. The nearly neutral lead acetate is then recharged with lead oxide to bring it to the proper basicity and the operation repeated. The lead acetate acts therefore as a carrier for the lead and theoretic- ally should all be recovered. A small amount of the acetate of lead remains with the white lead, however, probably as a hexabasic acetate. 212 ELEMENTS OF INDUSTRIAL CHEMISTRY The Rowley or Mild Process This process, although similar to, differs from, the Carter proc- ess in that no acetic acid is used. It had long been assumed that white lead could not be made without a carrier like acetate of lead. The advent of this process shows that this assumption was erroneous. The lead is atomized in a manner similar to that used in the Carter process. The atomized lead after proper notation is run into oxidizers which consist of mechanically agitated tanks containing water into which air under low pressure is forced. The oxide of lead so produced — which may be more or less in the form of hydroxide — is floated away from the unoxidized metal and run into carbonators which are horizontal rotating cylinders where, under the action of carbonic acid gas (contained in purified flue gas), white lead is produced. It is then allowed to settle and the thickened pulp is pumped onto drying pans and dried. SUBLIMED WHITE LEAD. Sublimed white lead is an amor- phous white pigment possessing excellent covering and hiding power, and is very uniform and fine in grain. It is a direct furnace product obtained by the sublimation of galena, and within the last ten years it has come into great prominence among paint makers, it now being regarded as a stable, uniform, and very valuable paint pigment. The author has examined a great many paints containing sublimed lead. Among one hundred reputable paint manufacturers in the United States sixty-five used sublimed lead. About eight thousand tons were used in the United States in 1905. Considering the fact that sublimed lead as a pigment is about twenty-five years old, it is very likely, judging from its qualities, that it will be used more universally and in larger quantities in the future. When mixed with other pigments, such as zinc oxide, car- bonate of lead, and the proper reducing materials added, such as silica, clay, barium sulphate, etc., it produces a most excellent paint, and at the seashore its wearing quality is superior to that of carbonate of lead. In composition it is fairly uniform. From the analysis of thirty-four samples of sublimed lead its composi- tion may be quoted as 75 per cent lead sulphate, 20 per cent lead oxide, and 5 per cent zinc oxide, although each of these figures will vary slightly either way. Corroded white lead also varies in its percentage of hydrate, but for analytical purposes a constant must be admitted which will fairly represent the composition. PIGMENTS 213 The question has arisen of late years whether sublimed lead is a mixture of the three components just cited, or whether it is a combination of lead sulphate and lead oxide with the mechan- ical addition of zinc oxide. Inasmuch as all the lead oxides that are known in commerce or in chemistry are yellow, red, or brown, it is held by many that the lead oxide of sublimed lead is really an oxysulphate, or, in other words, a basic sulphate of lead. A mix- ture of precipitated lead sulphate, litharge, and zinc white in approximately the proportions found in sublimed lead, when ground in oil and reduced to the proper consistency, dries totally differently from sublimed white lead ; in fact, sublimed lead when ground in raw linseed oil takes two days to dry dust free, but the mixture just cited will dry sufficiently hard for repainting in twelve hours, because lead sulphate is a fair drier and lead oxide a power- ful one. Yet the oxysulphate, having the same composition, behaves totally differently from the mixture and in addition is of a different color. Under the microscope, sublimed lead shows the absence of crystals and remarkable uniformity of grain. Being a much more complete chemical body than the other lead paints, it does not react on linseed oil and therefore makes a much more durable paint compound. It has been urged that sublimed lead is not as susceptible to sulphur gases as white lead, but this the author has not been able to substantiate, for while it may take hydrogen sul- phide a longer time to discolor it, it is simply a question of degree, and it is acted upon by sulphur gases, although not as quickly as white lead. Sublimed lead can be determined in a white mixed paint without any difficulty, owing to the established ratio between lead oxide and lead sulphate. The percentage of free zinc sulphate in sublimed white lead varies from a trace to a half per cent, and many times a chemist will report more zinc sulphate than is actually present, because in washing or boiling a dry or extracted sample the lead sulphate may interact with the zinc oxide and show a larger percentage of zinc sulphate than is really present in the dry products before analysis. Sublimed white lead as a marine or ship paint is of much value, owing to its hardness of drying and imperviousness of film. ZINC OXIDE. As a paint pigment zinc oxide is but little over fifty years old. Its discovery was made by Le Claire in France and by Samuel T. Jones in America at about the same time. The product made by the Le Claire process is known as 214 ELEMENTS OF INDUSTRIAL CHEMISTRY " French process " or " French zinc oxide," while that made by the Jones process is known as " American process " or as " American process zinc oxide." French Process. The raw material for this process is metallic zinc, which is obtained from its ores as " spelter " by reduction, distillation and condensation. The vaporized zinc as it comes in contact with the air at high temperatures takes fire, thus pro- ducing a smoke which is conducted into large chambers where it settles and from whence it is removed from time to time for shipment. Much zinc oxide is made in this country by the French process and is known as " Florence zinc." It is sold in three grades, mmely " White Seal," " Green Seal," and " Red Seal." American Process. In this process the raw materials are ores of zinc. The ore and reducing material are heated in a special form of furnace so arranged that the escaping vapors are brought into direct contact with air. The fume is then conducted by means of a fan into the collecting system. The collecting system consists of a series of bags which are suspended vertically from a system of horizontal pipes. From these bags the oxide is removed, bolted and graded for shipment. American zinc oxides come on the market as " Selected," " XX Black Brand," " Special," and " XX Red Brand." Owing to the fact that zinc oxides have a great powder to carry oil, give a very white color and help to harden the film, they have met with quite general application. They are especially help- ful as a constituent of mixed paints. LlTHOPONE. When solutions of zinc sulphate and barium sulphide are mixed together in molecular proportions, a heavy flocculent precipitate is formed according to the following reac- tion: ZnS0 4 +BaS = ZnS-f-BaS0 4 . The theoretical percentage will be 29| per cent zinc sulphide and 70J per cent barium sulphate. This precipitate as such has no body or covering power, and when washed and dried is totally unfit for paint purposes, but John B. Orr, of England, in 1880 discovered that when it is heated to dull redness, suddenly plunged into water, ground in its pulp state, thoroughly washed and dried, its characteristics are totally changed, and it makes a very effective and durable pigment for paint purposes. In the first place, it is a brilliant white; in the second place, it is extremely fine in texture, and in the third place, it has the same PIGMENTS 215 tinctorial strength but more hiding power than pure zinc oxide. Inasmuch as it is a complete chemical compound it is stable in every medium known for paint purposes, excepting those which are highly acid. It took several years to perfect the manufacture of lithopone, but it may be said that at the present time litho- pone is made with great uniformity and has valuable properties. Lithopone is likewise very largely used in the cheaper grades of enamel paints, because it does not combine with rosin or semi- fossil resin varnishes and therefore remains unaltered in the pack- age. As an interior white, a first-coat white, a ready-mixed flat paint for surface, or as a pigment in the lighter shades for floor paints, lithopone cannot be excelled for its body, durability, hardness, fineness of grain, and ease of application. It does not oxidize progressively, and this single feature has made it invalu- able to the table oilcloth and floor oilcloth industry throughout the world. Its indiscriminate use, however, is not to be recom- mended, and the paint chemist should be permitted to decide when its value is the greatest. As a marine paint, either as a first coat or for making neutral paints where other whites would be necessary, it is found to outlast both zinc oxide and lead car- bonate. BARYTES. This material is the sulphate of barium. It is a very heavy white pigment and is sometimes used as an adulter- ant of white lead. When employed in small amount, however, it gives strength to the film and should not be considered as an adulterant. WHITING. This is the carbonate of calcium and for certain purposes finds application in the paint manufacture. ASBESTINE. This material is a magnesium silicate pre- pared from asbestos. Its use in paint is as a binder and owing to its nature finds application as an emulsifier. That is, it helps to hold other pigments in suspension. Quicksilver Vermilion. Quicksilver vermilion is the amorphous mercury sulphide which is normally black, but when made with sulphur in the presence of an alkaline solution, it be- comes bright red. Red Lead and Orange Mineral. Red lead and orange mineral are the red oxides of lead and are both chemically alike. Red lead, is, however, made by heating litharge, which is the ground oxide of lead, and orange mineral is made by heating white lead until all the water and carbonic acid are driven off. VENETIAN Red. This is a ferric oxide containing gypsum 216 ELEMENTS OF INDUSTRIAL CHEMISTRY in varying quantities, obtained by heating ferrous sulphate in the presence of calcium oxide. INDIAN RED. Indian red is generally a very pure form of ferric oxide made by heating copperas or ferrous sulphate until it is converted into ferric oxide. Permanent Vermilion. Permanent vermilion is usually orange mineral tinted with para-nitr aniline. Burnt Ochre and American Sienna. Burnt ochre and American sienna are analogous, being made of hydrated oxide of iron and clay ore burnt until the ferrous salt is converted into ferric. CHROME YELLOW. Chrome yellow is chromate of lead made by adding chromate of potassium or sodium to a basic lead nitrate solution. The precipitate thus formed is washed, pressed and dried. Ultramarine Blue, Cobalt Blue. Ultramarine blue and cobalt blue may both be made from the natural minerals. Ultramarine blue whether artificial or genuine is chemically the same, with the one difference that the genuine ultramarine blue is the powdered mineral known as lapis lazuli, and ordinarily is the blue known under that name, but the mineral itself is found at times in an impure state either admixed with slate or gang rock, or contaminated slightly with other minerals. The genu- ine ultramarine bhe may run, therefore, from a very deep blue to a very pale ashen blue; in fact, the lapis lazuli which lies adjacent to the gang rock is ground up and sold under the name of ultramarine ashes, which is nothing more nor less than a very weak variety of genuine ultramarine blue. From the standpoint of exposure to light or drying quality, the artificial ultramarine is just as good as the genuine, and the only advantage that the genuine has over the artificial is that the genuine is not so quickly affected by acids as the artificial is. PRUSSIAN BLUE. This is a very permanent and powerful color made by precipitating solutions of ferrous salts with ferro- cyanide of potassium, and subsequently converting into the ferric condition. CHROME GREEN. Chrome green is a mixture of chrome yellow and Prussian blue, and is not the chromium oxide described in the next paragraph. CHROMIUM OXIDE. This green is one of the most perma- nent greens used, but it is not extensively employed in the manu- facture of mixed paints except where absolute permanence is PIGMENTS 217 necessary. It is met with occasionally in railway paints for switch target signals, and as a mixed paint to be used on vessels for repainting the receptacle in which the starboard lights rest. It is not a brilliant green and cannot be compared with the chrome greens, which are mixtures of chrome yellow and Prus- sian blue. It is more of an olive shade. Lamp Black and Carbon Black. Both of these are con- densed soots, the one made from dead oil, and the other usually from gas. They are pure carbon. GRAPHITE. Graphite is either artificial or natural, and very seldom contains more than 90 per cent of carbon. It has a peculiar silvery luster by which it can be identified. CHARCOAL AND COAL. Charcoal and coal are analogous in composition, except that charcoal black is alkaline and coal black acid. Vine black is also the same as charcoal black. MINERAL BLACK. Mineral black is usually a slate colored with oxide of iron. SILICA AND INFUSORIAL EARTH. Silica and infusorial earth are usually either ground quartz or the native infusorial earth washed and powdered. China clay and kaolin are silicates of alumina largely used as either reinforcing pigments or substra- tums for lakes. BARIUM SULPHATE. Barium sulphate is an artificial pre- cipitate, usually made from barium chloride and sodium sulphate, and is largely used as a lake base, and in its dry form as a rein- forcing pigment. The United States Navy has lately experi- mented with it in a very large way for making battleship gray. Gypsum and Terra Alba. Gypsum and terra alba are either artificial or natural calcium sulphate. Prince's Mineral and Prince's Metallic Prince's mineral and Prince's metallic are both oxides of iron containing about 40 per cent of oxide, the balance being silicate or clay. OCHRE. Ochre is clay stained with the hydrated oxide of iron. UMBER. Umber is a clay earth stained with oxides of man- ganese and iron. SIENNA. Sienna is largely composed of hydrated oxide of iron and a very small percentage of clay. Vandyke Brown. Vandyke brown is a clay earth stained with a bituminous compound. PAINT VEHICLES. The vehicles or liquids used in making paint are linseed oil, soya bean oil, China wood oil, fish oil, corn oil, turpentine, benzine, benzol, turpentine substitutes and driers. 218 ELEMENTS OF INDUSTRIAL CHEMISTRY LAKES. In addition to the large number of pigments which are employed, we have an almost unlimited number of compounds which are derived from the various classes of dyestuffs. These compounds, known as lakes, are prepared by precipitation of the dyestuff with a suitable precipitant in the presence of an inert base, this base acting as the carrier of the color. The precipi- tants used depend upon the nature of the dyestuff, those ordinarily employed being barium chloride, calcium chloride, lead acetate, zinc sulphate, aluminium sulphate, and tannic acid. The base upon which the color is precipitated is important , as it affects the covering power, cheapness, and character of the pigment. These lakes are sold as dry colors; pulp colors, mixed with water; or paste colors, mixed in oil. These color lakes find extensive application in the manufacture of lithographic inks, paint colors, colors for kalsomine or wall finishes, and colors for wall paper and coated paper surfaces. CHAPTER IX FERTILIZERS FERTILIZER MATERIALS. Broadly speaking, there are two kinds of fertilizer materials: those which are in themselves a direct source of plant food, and those which, by their action, tend to make plant food fertilizers more available. While crops may grow T without the use of fertilizers of the second class, no crops can mature without fertilizers of the first class. Fertilizers of the second class comprise lime, gypsum, and common salt; they are all useful, but rarely indispensable. These are sometimes called " stimulant fertilizers." They tend to make rapidly available the stores of ammonia, phosphoric acid, and potash naturally present in the soil. When stimulant fer- tilizers are used exclusively for a term of years, the soil loses ammonh, phosphoric acid, and potash. The inevitable result of such treatment must be finally the exhaustion of these important food constituents of the soil. True fertilizers contain forms of plant food which contribute directly to the growth and substance of plants. Such materials may contain either ammonia, potash or phosphoric acid com- pounds, or all three. TERMS USED IN ANALYSIS. Fertilizer dealers and experi- ment station bulletins treat the different forms of fertilizer ma- terials separately, and a familiar understanding of these trade names is important. Ammonia is expressed either as nitrogen, as ammonia, or as nitrogen " equivalent to ammonia." There are various conditions in which phosphoric acid may be expressed, such as reverted, available, insoluble, total, and phosphoric acid " equivalent to bone phosphate of lime." Potash is expressed as potash, as potash actual, or as potash equivalent to sulphate of potassium or to chloride of potassium. All genuine commercial fertilizers owe their value to the kind, quality, and amount of nitrogen, phosphoric acid, and potash they contain. They are made by mixing more or less of 219 220 ELEMENTS OF INDUSTRIAL CHEMISTRY the several kinds of raw materials furnishing the desired ingre dients, and to these may be added sulphuric acid to render the phosphoric acid available and a filler to make up the desired formula. Expression of Formulae. One often sees formulas expressed in this manner, 4-8-2, or 3-6-4. It means that nitro- gen comes first, phosphoric acid next, and potash third, hence the 4-8-2 indicates a fertilizer containing 4 per cent of nitrogen, 8 per cent of phosphoric acid, and 2 per cent potash. These figures multiplied by 20 give for each ton 80 lbs. nitrogen, 160 lbs. phosphoric acid and 40 lbs. potash. EXPLANATIONS OF MARKET QUOTATIONS; HOW TO ESTI- MATE THE VALUE OF FERTILIZERS. Phosphate rock, kainit, bone, fish-scrap, tankage, and some other articles are commonly quoted and sold by the ton. The seller usually has an analysis of his stock, and purchasers often control this by analysis at time of the purchase. Acid phosphate is usually quoted at so much " per unit " of available, that is, soluble and reverted phosphoric acid. The meaning of the term unit is explained below. Tankage is usually sold with a quotation of so much " per unit of ammonia " and " per unit of bone phosphate." The amount of bone phosphate may be calculated by multiplying the amount of phosphoric acid by 2.1850. On the other hand, the amount of phosphoric acid is calculated from the bone phosphate by multiplying the latter by 0.4576. Sulphate of ammonia, nitrate of soda, and the potash salts are quoted and sold by the pound, and generally their wholesale and retail prices do not differ materially. Blood, azotin, and concentrated tankage are quoted at so much " per unit of ammonia." To reduce ammonia to nitrogen, multiply the per cent of ammonia by 0.8228; to make the reverse calculation multiply by 1.2154. A " unit of ammonia " is 1 per cent, or 20 lbs. per ton. To illustrate: if a lot of tankage has 7 per cent of nitrogen, equivalent to 8.50 per cent ammonia, it is said to contain 8 J units of ammonia, and if quoted at $2.25 per unit, a ton of it will cost 8| times $2.25, or $19.13. Tankage and fish-scrap are sometimes sold at a price, based on analysis, with regard to both the nitrogen and phosphoric acid which the product in question contains. For example : Tank- age, 9-20 quoted at $2.49 and 10 cents per unit, means that a given lot of tankage contains somewhere in the neighborhood FERTILIZERS 221 of 9 per cent ammonia and 20 per cent bone phosphate, and is offered at $2.49 per unit of ammonia and 10 cents per unit of bone phosphate. A unit of ammonia, 20 lbs. is equivalent to (20 times 0.8228) 16.46 lbs. of nitrogen and is quoted at $2.49. 2 49 One pound of nitrogen, therefore, costs -~^ equal to 15.10 cents. A unit of bone phosphate, 20 lbs., is equivalent to 20 times 0.4576 equal to 9.15 lbs. of phosphoric acid, and is quoted at 10 cents. One pound of phosphoric acid therefore costs ^pp> equal to 1 cent. Hence it appears that a tankage containing 9 per cent ammonia and 20 per cent of bone phosphate and quoted at $2.49 and 10 cents per unit/ costs for nitrogen 15.1 cents per pound and for phosphoric acid 1 cent per pound. The cost of such a tankage will be 9 units of ammonia at $2.49 equal to 822.41 plus 20 units of bone phosphate at 10 cents per unit, or $2 or $24.41 per ton. Materials Furnishing Nitrogen. Guano. On the coast of Peru lie the Chincha Islands. These islands and the main- land opposite are in the dry zone of Peru in which rain seldom falls. They are small, high and rocky, barren and uninviting; yet from them has come vast wealth. Guano to the value of one thousand million dollars has been taken from the Chincha Islands. It is doubtful if there be another spot of equal size on the earth which has yielded so much wealth as these guano beds. These islands, however, are not the only source of Peruvian guano, as the Macabi, Guanape, the Lobos, Ballestas, and the Huanillos, as well as scores of small islands have also furnished large quantities. The word guano is the Spanish rendering of the Peruvian word huanu, meaning excrement. There are many varieties of Peruvian guano having different fertilizing values due to their different chemical constituents, but they all are alike in their origin. Guano is mainly the excrement of marine birds mixed with the remains of the birds themselves and the fish they have brought to land. In some cases on the Chincha Islands the deposits are from 160 to 180 ft. thick. The lower strata of such deposits may be thousands of years old. In reviewing this subject, L'Engrais of Paris estimates that in forty years over 18,500,000 tons were taken from these locali- ties or about 440,000 tons annually. 222 ELEMENTS OF INDUSTRIAL CHEMISTRY As the penguins and pelicans are very voracious each bird is capable of furnishing on an average, about 32 gms. of excre- ment per night. It is estimated that 100 kgms. of guano, con- taining 14 per cent of nitrogen and 10 per cent of phosphoric acid, require the consumption of 600 kgms. of fish containing 2.3 per cent nitrogen and 1.7 per cent phosphoric acid. An annual deposit of 40,000 tons is, therefore, the digestive product of 3,420,000 pelicans. It is reported that while the old beds have been considerably reduced there are layers 30 ft. thick which have not been touched and which are still forming. The guano is taken out by shovel and pick. As the coasts are rough and few harbors exist, loading of steamers can be done in calm weather only. The water is very deep and large steamers can anchor close to the shore so that most of the guano can be loaded directly into the steamer from the shore by means of cable trams. In some cases, it has to be taken to the steamer in boats. Calcium Cyanamide. This is a product derived by heating calcium carbide in an atmosphere of nitrogen. The reactions are intricate, but may be represented by the following equation: CaC2+N 2 = CaCN 2 +C. The technical procedure is simple, but care must be taken in carrying out the details. The nitrogen must be technically pure and the complete nitrification of the carbide, necessary to pro- duce a high-grade product, is dependent upon progressive and cumulative reactions, which once started may not be checked or diverted at any stage except at the cost of the quality of the final product. To prepare adequately the raw cyanamide for incorporation into fertilizers several processes have been developed and much costly machinery designed, the object of such processes being simply to hydrate all the caustic lime and to dislodge and expel as a gas all the substances in the raw cyanamide which will produce acetylene, phosphine, and hydrogen sulphide. Dry Fish Scrap. The menhaden (Brevoortia tyr annus) belongs to the family Clupeidse and has many local names. On the Maine coast it is called pogy, pony fish, moss-bunker; in Massachusetts, hardhead bunker; in Delaware, bug fish, in addi- tion to those already given; on the Virginia coast, old wife, cheboy, ellfish, bug fish, green tail, and bughead; in North Carolina, fat-back and yellow-tail shad. FERTILIZERS 223 When full grown the fish weigh from 10 ounces to 1J lbs. and measures from 12 to 15 ins. in length. They are found in immense schools on the American North Atlantic coast from the Bay of Fundy to the Mosquito Inlet, Florida. Their usual habitat is the bays and rivers, sometimes as far as brackish water extends, and ocean-ward as far as to the Gulf Stream. On the approach of warm weather the schools begin to appear and remain until cold weather sets in. Approximately a temperature of from 60 to 70° F. appears favorable. In the Chesapeake Bay the season extends from March and April to November and December. The New Jersey fishing season begins about May 1st and ends about the middle of November. The habit of the fish is to congregate in very large schools and then swim along close to the surface of the water, packed closely side by side and tier on tier. As many as 450,000 tons of these fish have been taken in a single season. When a school of fish is sighted, the steamer gets as close as possible without scaring the fish and then lowers the two seine boats of whale-boat pattern. The seine is a net from 750 to 1800 ft. long and 75 to 150 ft. deep with the usual fitting of cork and sinkers, and so arranged that the bottom may be drawn together, thus making a purse in which the fish are held. The two boats, each carrying an equal amount of the net, start in opposite directions around the school and when they have met, start pulling in the purse string. When the bottom is closed the steamer comes up and the fish are scopped from the net by means of large scoops worked by a derrick on the steamer. When a steamer has a load it returns to the factory, as the fish, if kept too long, soon turn soft and are then very difficult to handle. On reaching the factory, the fish are unloaded by being shoveled into a traveling conveyor which takes them to a belt which carries them into the store shed. From here they are carried to a continuous steam cooker, where the oil cells are broken and the fish bodies broken up. This requires but a few minutes, when the fish are run into screw presses. On leaving the cookers they contain about 75 per cent of water. The screw presses can press the fish down to about 45 to 50 per cent of water. Most of the oil is here liberated. The water and oil are run into large settling tanks and the oil which rises to the top is taken off. The fish from the presses then go to direct-heat or steam- heated cylindrical dryers. They are dropped into the hot end 224 ELEMENTS OF INDUSTRIAL CHEMISTRY of the dryer where the flame from either soft coal or oil is pouring in. The water in the scrap prevents the burning of the fish as it immediately takes up the heat. The scrap falls to the bottom of the dryer and is carried around as it revolves and showered down through the hot gases. On reaching the end of the dryer it is cool enough to handle and contains about 8 per cent water. It is now picked up by a traveling belt and run to the storehouse where it is bagged ready for shipment. Great care must be taken in the storeroom, on account of the combustible nature of this material, owing to the presence of the oil left in it. It heats very rapidly if left in large piles and must be cooled by turning over. The capacity of a factory is usually calculated as the number of barrels per day of fish that it can handle. One barrel contains 300 fish. A large and well-equipped factory will handle 700 barrels of fish per hour, turning it out as wet acid scrap, or if the dryer capacity is equal to the cooking and pressing capacity as dry scrap. To produce 1 ton of dry scrap requires an average of 50 barrels of fish, while to make 1 ton of acid scrap (wet) requires 30 barrels of fish. In a good season about 3 gallons of oil per barrel of fish is recovered. Wet Acid Scrap. Where the plant does not have enough dryer capacity to take care of the catch, the excess is made into wet acid scrap. The fish scrap from the presses is acidulated with from 60 to 80 lbs. 60° Be. sulphuric acid to the ton of wet scrap. This converts some of the bone phosphate into the avail- able form and at the same time preserves the scrap from decom- position. Good acid scrap that has not lain long in piles will analyze on 50 per cent water basis as high as 7.50 to 7.75 per cent ammonia. Slaughter House Tankage. In all slaughter houses the scrap meat ie saved and treated for the production of " tankage." As all this material has more or less grease still adhering to it, it is first placed in large tanks and boiled under pressure till the grease, has left the meat and the bone. The scrap is then allowed to drop to the bottom of the tank and the liquor is drawn off into large vats. After the grease has risen to the top it is with- drawn. The remaining liquor is then treated for its fertilizing constituents as given elsewhere under " concentrated tankage." The scrap meat and bone, or as it is called, " tankage, " is now pressed to free it as much as possible from the water and ad her- FERTILIZERS 225 ing grease and is then dried in rotary direct-heat or steam dryers. It is then ready for sale. In plants where the liquors are evaporated for " concentrated tankage " it is a general practice to mix the " stick " or thick liquor obtained by evaporation directly with the tankage before drying. This raises the percentage of ammonia and at the same time does away with the making of a second product. PHOSPHORIC ACID. This as 'used in fertilizers does not exist as true phosphoric acid, but as various salts of phos- phoric acid and lime. Soluble phosphoric acid is the mono- calcium phosphate formed during the process of acidulating phosphate rock or bone. Reverted phosphoric acid is the dieal- ciurn phosphate which is also formed during the process of acidu- lation and is soluble in neutral ammonium citrate. Available phosphoric acid is the sum of the soluble and reverted forms and is the total phosphoric acid in a condition capable of being absorbed by plants. Insoluble phosphoric acid is the tricalcium phosphate as it exists in phosphate rock and bone and is not available for plant food. Total phosphoric acid is the total amount present irrespec- tive of the form in which it is present. It is the sum of the above three forms. Phosphoric acid equivalent to bone phosphate simply means the total phosphoric acid calculated as the tri- calcium phosphate. Phosphatic Crude Stock. Furnishing insoluble phosphoric Furnishing available phosphoric acid: acid. Animal : Animal : Bones Dissolved bone, acid-fish- scrap. Mineral: Mineral: Apatite, phosphate rock Acid-phosphate from any from Florida, Tennessee, form of mineral phosphate, of blue, brown and white colors. Thomas slag. The Phosphate Rock Industry. From time to time various deoosits of phosphate rock have been found and mined throughout the world, but the principal workings to-day are to be found in Florida, South Carolina, and Tennessee in the United 226 ELEMENTS OF INDUSTRIAL CHEMISTRY States, in Algeria and Gafsa in North Africa, and in Ocean and Christmas islands in the far east. The first serious attempt to obtain phosphate in this country was in Canada, mining what is known as Canadian apatite. This is a very high-grade material, but it was very expensive to mine and when in 1870 the South Carolina, and in 1888 the Florida deposits were marketed, it could not compete with them. The rock in South Carolina is found in two grades — river and land pebble. It is deposited in considerable quantities along the mar- gins of navigable streams and in the river beds between Charles- ton and Beaufort. When a deposit is located it is first thoroughly prospected by boring with a core boring machine, as by this means the depth of the bed is ascertained as well as the grade of the various layers of phosphate encountered. The mining is hydraulic. Powerful streams of water are thrown against the edge of the bed and the phosphate gravel together with the sand and clay is washed into a hole about 10 ft. in diameter and 10 to 15 ft. deep. The gravel is sucked up from this hole by means of a pipe and run to the mill, which may be half a mile or more away. Here it is passed over screens which allow the fine silt and sand to escape while the phosphate pebbles are caught. This serves to wash the rock, and it is then passed through direct-heat rotary dryers and carried by belts to the storage bins, ready for shipment. Tennessee Brown Rock Phosphate. The Tennessee phos- phates occur almost entirely in Silurian and Devonian strata, but more particularly in the former, and in the transition strata between the two. In December, 1893, blue rock phosphate was discovered in Hickman County. The beds of brown rock in this vicinity, which are the finest phosphate deposits in the world, were not worked till later. Some 45,000,000 tons of this brown rock are estimated as being available for mining in this district. New fields are being continually opened up, railroads built and large quantities shipped. As the brown rock of this locality is gradually used, the vast blue rock fields of Maury, Hickman, and Lewis counties will come into active development. This brown rock lies in strata formation with layers of clay and earth as overburden. This overburden is stripped by hand or steam shovel and the soft wet phosphate taken out either by- hand or steam shovel. It is carried to the washers, where it is freed from the most of the clay and dirt. On account of the porous nature of this rock, the clay is disseminated all through FERTILIZERS 227 it and it is very difficult to get rid of all the clay by the use of simple log washers. Many types of washers are used, the most efficient being the form used in cleansing glass-makers' sand. This is done by pumping the fine material through pipes having sharp angles, where the pressure is greatly increased. The clay is washed out in this manner and the clean rock is finally deliv- ered to very deep settling tanks, where the muddy water hold- ing the clay in suspension is drawn off and the heavier rock, which settles after the tank is filled, is dried in rotary direct- heat dryers and is then ready for shipment. Thomas or Belgian Slag. Thomas or basic slag is a by- product in the modern method of steel manufacture from ores containing noticeable quantities of phosphorus. The process of removing the phosphorus from the ore was first discovered by the English engineers Gilchrist and Thomas and consists in add- ing to the converter containing the milled ore a definite quantity of freshly burnt lime, which, after powerful reaction, is found to be united with the phosphorus and swims on the top of the molten steel in the form of a slag. The fertilizing value of the slag was not recognized for a long- time. A considerable portion of its phosphoric acid was found to be soluble in dilute citric and carbonic acids, which led to suc- cessful field experiments. The only preparation of the slag for fertilizer purposes when its value was first recognized, consisted in having it finely ground in specially prepared mills so that To per cent would pass a sieve of 0.17 mm. mesh. This require- ment was suggested by M. Fleischer, who used the slag with much success in improving marsh and meadow lands. Bone. Bones consist of two distinct kinds of matter. One is mineral in character and consists of phosphate of lime or true bone phosphate; the other is organic, consisting of a flesh-like matter called ossein, which contains much nitrogen. POTASH. This term as applied to fertilizers always means the oxide of potassium. It is not found as such in fertilizers, but as either chloride, sulphate, nitrate or carbonate of potassium, or as organic potash. Potash soluble means the actual K2O soluble in water, and is the only kind considered in fertilizers. Crude Stock Furnishing Potash. Muriate or chloride, kainit, containing both muriate and sulphate; sulphate; double manure salt; the double sulphate of potash and magnesia; less important salts are carnalite, krugite, sylvanite. Carbonate of 228 ELEMENTS OF INDUSTRIAL CHEMISTRY potash, such as wood ashes. As organic potash, tobacco stems and ashes, cotton-seed meal. As nitrate, potassium nitrate. Alunite, the hydrated sulphate of potash and alumina, is found in many places in the West and work is being done on it to deter- mine its availability as a source of potash. It has been found that after ignition and leaching, over 90 per cent of the, potash can be recovered as sulphate. It appears to be a very promising source for future supply of this material. PEAT FILLER. Dried humus or peat is used as a filler on account of its absorbent properties, but its use is prohibited by some States if the nitrogen content is included in the nitrogen of the fertilizer, because this nitrogen is unavailable. how to Calculate Amounts of Material to be Used in Making a Complete Fertilizer of Definite Com- position FROM THE RAW MATERIALS. Suppose that we desire to make a fertilizer having the composition: nitrogen 4 per cent, phosphoric acid 8 per cent, and potash 10 per cent. Suppose in addition we have on hand the following materials: nitrate of soda containing 16 per cent nitrogen, acid phosphate containing 15 per cent available phosphoric acid, and muriate of potash containing 50 per cent actual potash (K2O). How many pounds of each of these materials will we require? To contain 4 per cent nitrogen, the ton must contain 80 lbs. Nitrate of soda contains 16 lbs. of nitrogen in every 100 of the nitrate, and hence 500 lbs. of nitrate of soda would be required to make up the 80 lbs. To contain 8 per cent phosphoric acid, the ton must contain 160 lbs. The phosphate contains in every 100 lbs. 15 lbs. of phosphoric acid and hence 1067 lbs. of the acid phosphate will be required to furnish 160 lbs. available phosphoric acid. To contain 10 per cent potash the ton must contain 200 lbs. Our muriate contains in every 100 lbs. 50 lbs. actual potash, and hence 400 lbs. will be required to give the 200 lbs. We should then have the following: 500 lbs. nitrate of soda, 1067 lbs. acid phosphate, 400 lbs. muriate of potash, or a total of 1967 lbs. Now to make it up to 1 ton we simply add 33 lbs. of any inert material such as dirt, for instance, and we then obtain 1 ton of fertilizer of the desired composition. By FERTILIZERS 229 adding 1 more ton of " filler " we should have 2 tons of fer- tilizer of the following composition: nitrogen, 2 per cent, phos- phoric acid, 4 per cent, and potash, 5 per cent. Now for the more complicated example suppose we wish to make a fertilizer of the same composition, but instead of having three materials, each containing only one ingredient, suppose we have on hand Peruvian guano, containing 3 per cent nitrogen, 18 per cent phosphoric acid, and 3| per cent potash. To give us 160 lbs. (8 per cent) of phosphoric acid we shall require about 900 lbs. of this guano. Nine hundred pounds would also supply 27 lbs. of nitrogen and 31 lbs. of potash. But we require 80 lbs. of nitrogen and 200 lbs. of potash in all, or 53 lbs. more nitrogen and 169 lbs. more potash to complete the mixture; 384" lbs. of nitrate of potash analyzing 14 per cent nitrogen and 44 per cent potash would supply this 53 lbs. nitro- gen and also the 169 lbs. potash, therefore we have Nitrogen. Phos. Acid. Potash. . 900 lbs. guano containing 27 lbs. 160 lbs. 31 lbs. and 384 lbs. nitrate of potash 53 lbs. 169 lbs. or total of 1284 lbs. containing 80 lbs. 160 lbs. 200 lbs. Now by adding 716 lbs. of filler we have 1 ton of fertilizer of the desired formula. For a third example, suppose we have the following materials : 1st, one containing 3 per cent nitrogen, 18 per cent phos. acid, and 3| per cent potash; 2d, one containing 6 per cent nitrogen, 9 per cent phos. acid and 2 per cent potash; 3d, one containing 50 per cent potash; we would then take 1st. 300 lbs. containing 2d. 1200 lbs. containing 3d. 332 lbs. containing Total 1832 81 162 200 By adding 168 lbs. of filler we then have 1 ton of our fer- tilizer. A filler in common use is obtained from garbage extracted Nitrogen. Phos. Acid. Potash. 9 lbs. 54 lbs. 10 lbs. 72 lbs. 108 lbs. 24 lbs. 166 lbs. 230 ELEMENTS OF INDUSTRIAL CHEMISTRY for the grease it may contain. The pressed and dried material has practically no value from its nitrogen or phosphorus content, although the tankage is very heavy in soluble material. These methods of calculation of formulae are simply given as examples; as a matter of fact, probably not over 5 per cent of all the complete fertilizer manufactured contains " filler " in the sense in which it is given above. When low-grade fertilizers are to be made, they are compounded from low-grade raw materials that will, without the use of fillers, or with only a very small amount, give the formula desired. CHAPTER X ILLUMINATING GAS CLASSIFICATION. The industrial gases in use at the present time may be divided, roughly, into three general classes — coal and carbureted water gas and their various mixtures; the dif- ferent classes of oil gas, acetylene, gasoline gas; and producer gas. The first class is by far the most important from an illu- minating standpoint, while producer gas is, of course, of the greatest importance for fuel and power use. The other gases are generally employed in special cases where the use of the first class is impossible or inconvenient. Manufacture of Coal Gas. Coal gas is the result of the destructive distillation of bituminous coal in highly heated fire- clay retorts. The retorts vary considerably in cross-section, length and method of heating. They are usually set in groups of from six to nine retorts in what is known as a " bench," and the group of " benches/' varying with the capacity of the plant, is known as the " stack." In a few of the older and smaller plants the retorts are heated by a direct fire of coke or coal, but in the more modern and larger plants they are heated with pro- ducer gas. These retorts may be set either in a horizontal, inclined or vertical position, but in the latter cases the method of charging and discharging is different from that of the former. The object, however, in any case is to drive off the volatile matter, which consists principally of gas. In the manufacture of coal gas, coal with a high volatile content is preferred; that is, a coal belonging to the bituminous series according to the usual method of coal classification. Horizontal Retorts. In operating the horizontal retorts, Fig. 74, the coal is placed in position by means of a charging machine, although formerly this was done by hand. The retort being filled about two-thirds full of coal, the door is closed and sealed. The bench is so arranged that the flame from the burning fuel heats the firebricks supporting the retorts. The time necessary to drive off the gases from the coal varies from six to eight hours / 231 232 ELEMENTS OF INDUSTRIAL CHEMISTRY at the end of which time only the residue of coke is left in the retort. The coke on being drawn from the retort is either quenched with water or allowed to fall into the furnace used for heating the retorts. The gases as they leave the retort pass up through ascension and dip pipes into the hydraulic main. From here the passage Fig. 74. of the gas will be considered after taking up the other methods of production Inclined Retort. In this form of apparatus the retorts are set at an angle. The charging is done by allowing the coal to run in at the elevated end directly from the storage bins; while the discharging is accomplished by removing the door at the lower end. Less labor is necessary for inclined retorts, but it is claimed ILLUMINATING GAS 233 by some that the yield of gas is not so great. The gas passes from the bottom of the retort through ascension pipes into the hydraulic main. Vertical Retorts. As the name indicates the retorts are built in a vertical position, illustrated in Fig. 75. The three retorts Ftg. 75. are charged at one time, the coke having been removed from the bottom by electrically operated machinery. The heating is accomplished by means of gas producers having large grate areas with primary and secondary air control. The gases from the three retorts, as shown in the illustration, pass through the ascension pipe to the b^draulic main. The ascension pipe bridge and dip pipes are provided with 234 ELEMENTS OF INDUSTKIAL CHEMISTRY removable covers so arranged that they may be readily cleaned of deposits of tar and pitch which accumulate in them and must be constantly removed. The producer is provided with grate bars and cleaning doors and is charged with hot coke as it is drawn from the retorts through the charging door on the upper floor level. The primary air enters through regulation shutters at the front of the bench, passes around the lower waste gas flues and hence beneath the grate. Rising through the fuel it combines with the carbon, forming producer gas. Steam is admitted beneath the grate to soften the clinkers and control their formation by lowering the temperature of the fuel bed. As the producer gas rises through the nostrils into the com- bustion chamber it meets the secondary air which is admitted through regulating shutters below and at the front of the bench. * Cyanogen Scrubber Fig. 76. The air travels through firebrick ducts in what is known as the recuperator , where it passes horizontally to the right and left and upward and is heated by the waste gases to a temperature of from 1600 to 1800° F., practically attaining the temperature of the waste gases. As the combustion takes place the hot products of combus- tion rise around the retorts to the top of the combustion chamber and are then drawn down and toward the front of the bench where they enter the waste gas flues in the recuperator, passing hori- zontally front and back and downwards giving up their heat to the incoming secondary and primary air. The waste gases finally pass to the back of the bench and hence to the stack, the draft of which is controlled with a damper set at a convenient point in the recuperator. The gas as it issues from the coal passes out through the mouthpiece and up the ascension pipe, and by means of the dip- pipe enters the hydraulic main. This acts as a seal to prevent ILLUMINATING GAS 235 the gas escaping from the hydraulic main back into the retort when the mouthpiece is open for charging or discharging. Fig. 76 shows the general plan of coal-gas plant. Ordinarily, there is an ascension pipe for each retort, but in some cases one ascension pipe serves three retorts, which are set directly above one another. This system is, of course, only applicable where the retorts are charged and discharged simul- taneously by machinery. Hydraulic Main. The desirability of the use of a liquid seal in the hydraulic main is subject to some question, and there are a number of methods proposed and in use whereby this seal may be lowered after the retort has been charged, thus putting the retort in direct connection with the hydraulic main, and then raising it' so that the retort is sealed off when the lids are opened for charging and discharging. Valves of different design have also been used for this purpose. When the hot gases come in contact with the liquid in the hydraulic main, a certain amount of tar is deposited; this is removed automatically from the main in order that it may not come into direct contact with the gas, and thus cause a deterior- ation of the candle-power. The crude gas leaves the hydraulic main at a temperature of from 65 to 75° C, and contains a number of impurities — tar, ammonia, sulphureted hydrogen, organic sulphur compounds, naphthalene and cyanogen — which must be removed in whole or in part before the gas is considered ready for distribution, and, furthermore, the gas must be brought down to the ordinary temperature. Condensers. When the gas leaves the hydraulic main it con- tains in addition to the imparities just mentioned a very complex mixture of hydrocarbons of widely varying boiling points, in addition to the water vapor with which it is practically saturated. Some of the hydrocarbons are fixed gases at the ordinary tem- peratures while in the others may be vapors, liquids or solids; while practically all are mutually soluble in each other and to some extent in water. As much of the illuminating value of the gas is due to the vapors of the benzol homologues it is important that these be retained in the gas as far as possible, while on the other hand the heavier hydrocarbons, especially naphthalene, must be removed as far as possible on account of their interference with succeeding stages of the purifying process or with the dis- tribution of the gas itself. 236 ELEMENTS OF INDUSTRIAL CHEMISTRY At the temperature at which the gas leaves the hydraulic main, the tar exists principally as a fog, and also as a vapor which will condense with a lowering of the temperature. This is effected in the primary condensers, one form of which is illustrated in Fig. 77. The cooling agent may be either water or air. In a recent system the cooling water is sprayed through the gas, assisting in the removal of the tar, and the water is then freed from tar, cooled and recirculated. To? Extractor. On leaving the primary condensers, in which some of the tar is deposited, the gas is passed into some form of Fig. 77. Fig. 78. tar extractor, the usual form being that of the P. & A., which consists, as shown in Fig. 78, of a drum composed of a series of perforated sheets consisting of alternate series of small holes and blanks so arranged that the blank spaces in one set of sheets opposes the perforated sections in the adjoining sheets. Another form of apparatus is known as the washer-scrubber. In this, the gas passes through a number of small openings into contact with ammonia liquor, the action of the water causing the tar particles to coalesce and be condensed. It is found that the most efficient operation for the removal of tar requires a tem- perature of from 105 to 115° F. ILLUMINATING- GAS 237 Exhauster. The gas is now passed through the exhauster, Fig. 79, which operates to maintain a constant pressure in the retorts and to furnish the pressure necessary to overcome the resist- ance of the train of purifying ap- paratus, and to force the gas into the storage holder. Scrubber. From the exhauster the gas passes into the naphthalene scrubbers. These scrubbers, Fig. 80, are composed of horizontal cylinders divided by a number of vertical partitions. A central shaft carries a disk made up of a large number of short wooden rods set parallel to the axis of the shaft, and arranged so that as they re- volve they dip into the contents of the scrubber, and on rising present a large wetted surface in contact with the stream of gas. A heavy tar oil, such as anthracene oil, water gas tar or vertical retort tar, is the material generally used for the removal of naphthalene. Fig. 79. Fig. 80. When cyanogen is extracted it is usually removed by means of a washer similar to the naphthalene washer. The solutions used 238 ELEMENTS OF INDUSTRIAL CHEMISTRY vary according to the processes employed, but they usually con- sist of an alkaline solution of ferrous sulphate. The gas now passes to the ammonia scrubbers, similar to naphthalene scrubber. In order that the absorption of ammonia by water, which is usually used to remove it, will be complete, it is necessary that the temperature of the gas be reduced to about 60°. This reduction in temperature is secured in the second- ary condensers; these are always water cooled in order to secure the low final temperature that is necessary. This absorption was formerly carried on in large towers filled with cobble stones or boards, or other devices exposing a large surface, which was kept moistened by water or weak liquor passing down from the top. This form of scrubber has been generally replaced by the more compact washer-scrubber similar in construction to that described for cyanogen removal. In these mechanical scrubbers the ammonia is completely removed by the use of from 10 to 15 gallons of water per ton of coal car- bonized, and as the gas is at the same time brought into contact with the concentrated ammonia liquor at the inlet end of the scrubber, a considerable proportion of sulphureted hydrogen and carbon dioxide is also removed. Ammonia Liquor. The ammonia liquor and tar that are removed at the different points in the condensing and purifying system are collected and passed through what is known as a separator. In this apparatus, the stream of mixed liquor in pass- ing through the separator is baffled and turned in its course a number of times, so that the tar, which has a specific gravity of 1.2, and higher, falls to the bottom and may be removed, while the liquor rises to the top and may be pumped orV to the ammonia storage tanks. The remaining impuri- ties in the gas are sulphur eted hydrogen and organic sulphur compounds. Purifiers. The sulphureted hydrogen is generally removed by passing it through large vessels, called purifiers, Fig. 81, where it is brought into contact with some form of ferric oxide. There Fig. 81. ILLUMINATING GAS 239 is considerable discussion as to the exact reactions which take place. The probable reactions are Fe 2 Os + 3H 2 S = Fe 2 S3 + 3H 2 and Fe 2 3 +3H 2 S = Fe 2 S+S+3H 2 0. It seems likely that these two reactions take place simultaneous^, and the proportions of ferric and ferrous sulphide formed are dependent upon the nature of the oxide and other conditions. It is said to be in the relation of three parts ferric to five parts ferrous sulphide. When the oxide has become saturated it is removed from the purifiers and exposed to the air, where, under the influence of the atmospheric oxygen, ferric oxide is formed and sulphur set free. In order to take advantage of this reaction, small quantities of air are sometimes admitted to the crude gas before entering the purifiers, the oxygen in which reacts with the partially fouled purifying material, and thus considerably increases the length of time before it is necessary to remove it. The purifying material is composed of either a natural ferric oxide or, as is generally the case, made by coating shavings, planer chips or com cobs with some form of ferric oxide. The efficiency of the purifying material thus made seems to depend upon the nature of the ferric oxide; the more active oxides are apparently colloidal in nature. Where the oxide is made by rusting iron borings on the chips the organic acids in the wood act as protective colloids and result in the formation of varying percentages of the iron in the colloidal form. Certain natural oxides and some of the artificial oxides that result as by-products in the manufacture of alums are found to have a considerable proportion of their iron content in the form of a colloid ferric hydroxide. Apparently it is the enormous surface that is presented by these colloidal oxides that explains the increased chemical efficiency of oxides in this state. In the older type of pufifiers the oxide was contained in shallow cast-iron boxes provided with water-sealed lids, the oxide being carried on wooden trays in two layers of about 30 ins. each. These boxes were arranged usually in sets of four or six, and so connected with valves that the sequence of boxes could be varied at will, and any box could be removed from service for cleaning. 240 ELEMENTS OF INDUSTRIAL CHEMISTRY It has now been found more economical to put the oxide into only two or three large boxes, building these either of steel or concrete out of doors, and th\ s saving expensive buildings. In testing the operation of the purifiers, we find that the first box removes the greater portion of the hydrogen sulphide, and that as the percentage of sulphur decreases it becomes increas- ingly difficult to remove it. The purifiers are usually arranged, therefore, so that at least one box is kept filled with fresh and active oxide to retain slight traces of sulphureted hydrogen which Fig. 82, might pass through the other boxes which remove the bulk of the Lr purity. WATER GAS. The manufacture of water gas depends upon the decomposition of steam by the action of incandescent carbon. The gas made by this reaction is called " blue gas," and while it has a heating value of about 300 B.T.U.'s per cubic foot it is non- luminous. In order to render the flame luminous it is necessary to add some hydrocarbon that will liberate free carbon in the flame. Many early patents were taken out to do this, but the process ILLUMINATING GAS 241 did not become important until the Pennsylvania petroleums became commercially available. The modern apparatus is the development of the Lowe apparatus that was patented in 1872-75. In its present form it is a very efficient process, as every feature has been considered both from a theoretical and operative standpoint. The supply of air and steam is metered. The temperatures in the fixing chambers are controlled with electric pyrometers and the sensible heat in the off-going blast and illuminating gases is recovered in greater part in economizer boilers that return sufficient steam to operate the plant. The apparatus shown in Fig. 82 has a capacity of 1,500,000 cu.ft. per day, but units having a capacity of 3,000,000 cu.ft. per day are in regular operation. Operation. The operation of a modern plant is as follows: The generator is charged with the fuel through the coaling door A. After ignition, it is raised to a point of incandescence by a blast of air supplied under a pressure of from 16 to 20 ins. through the blast pipe B, passing through the interlocking valve C, which is so connected that it will be impossible for the blast and the gas to come together and thus cause explosions. The air passes down through the Venturi meter D and is controlled by the valve E, where it enters the generator beneath the grate, passing through the fuel bed, where the reaction C+02 = C02 and C02+C = 2CO. The temperature of the fuel rises rapidly and a certain amount of producer gas is formed. This passes through the pair of valves FG, F being open during the blast, through the connection H, into the carbureter. The carbureter, which is a firebrick-lined vessel filled with checker-brick, is brought to the required temperature by the sensible heat in the blast products, and by the combustion of their CO by means of a secondary supply of air entering through the valve I. From the carbureter the products pass downward and up through the superheater, out through the valve K to the stack. When it is desired, the tertiary supply of air can be admitted through the valve J at the base of the superheater, causing further com- bustion, if desired, and local heating in this part of the apparatus. When the carbureting and superheating vessels have been brought to the proper temperature, the fuel in the generator is very highly heated. The air blasts are cut off in the order J, I and E. The stack-valve K is closed by means of lever L, and steam is introduced by means of the valve M and the steam 242 ELEMENTS OF INDUSTRIAL CHEMISTRY meter beneath the grate. The steam passes up through the bed of incandescent fuel, where the reactions C+H20 = H2+CO, and the further general water-gas reactions CO+H20 = C02+H2 take place. The water gas passes into the carbureter, where it meets the carbureting oil, which is measured by the meter Q and is sprayed into the carbureter through R. The sensible heat of the water gas and the high temperature in the surface of the checker-bricks vaporize the oil. The mixture of water gas and oil vapors then passes down through the carbureter, where the vaporization is completed, a considerable portion of the vapors decomposed and to some extent polymerized into fixed gases. Passing from the base of the carbureter up through the superheater, the temperature of the checker-brick of which is very carefully regulated, the decomposition of the oil vapors is carried to the most advantageous point, and the resulting mixture is composed of fixed gases, some condensible vapors and a small quantity of complex hydrocarbons, known as water-gas tar. These pass out through the connection to the valve K, through the dip-pipe S into the wash-box, which acts as a hydraulic seal and prevents both the escape of the products of combustion dur- ing the blasting period and the return of the illuminating gases. In contact with the water in the wash-box, the temperature of the gas is reduced from 1200 to 1300° F. to about 190° by the vaporization of the water, and some of the tar is deposited. The gases pass out of the wash-box through the connection to the base of the scrubber, and rise through the staggered nest of wooden trays, where the entrained solid matter, considerable water, and some tar are deposited by impingement and the temperature is somewhat reduced. From the top of the scrubber it passes into the top of the condenser through the water-cooled tubes. By means of the cooling water the temperature is reduced to 150° F., and it passes out of the connection Z to the relief holder. Fuel Used. The fuels used in the manufacture of water gas are anthracite and semi-anthracite coals and the various grades of coke. As they are used primarily as a source of carbon they should be high in fixed carbon, containing not over 7 per cent of volatile combustible, as some of this is liable to loss during the blasting period. The ash should be low and of high fusing point so that the formation of clinkers may be reduced to a minimum, although fuels containing as high as 25 per cent of very fusible ash can be utilized successfully. The fuel should be uniform ILLUMINATING GAS 243 in size to permit the free flow of the blast and steam and it should be low in moisture and sulphur. Enriching Oils. The oils available for enriching purposes vary in their composition in the different fields. The oils from Pennsylvania, Ohio, Indiana, and Illinois are composed prin- cipally of the paraffine and olefine series; the oils from Kansas and Oklahoma differ somewhat according to their gravity, the lighter oils containing considerable paraffine while the heavier oils contain some paraffmes but principally naphthenes. The gas as it leaves the machine goes to a relief holder, then to shaving scrubbers, then to the purifiers and finally to the gasometers for distribution. These pieces of apparatus are prac- tically the same as used for coal gas. The tar, however, is of an entirely different nature. A new form of water gas apparatus, which is largely replacing the Lowe Machine is that known as the Williamson Machine. This machine has the carbureter and superheater above the fuel bed. By this means it is possible to economize on space and cost of installation. The working of the machine is the same as for the older type. ALL-OIL WATER GAS. Directly related to the manufacture of carbureted w r ater gas is the so-called all-oil water gas which is used so extensively on the Pacific Coast where there is an abun- dant supply of cheap fuel oil. In the present form of apparatus which is illustrated in Fig. 83, there are two firebrick-lined shells in the form of a U, with one leg longer than the other, the shorter leg serving as the primary generator while the longer leg serves as a superheater. Both shells are filled with checker-brick. The gas take-off for the blast gases is at the top of the longer leg while the illuminat- ing gas take-off is in the middle. In the operation of the set, oil and steam are blown into the top of the primary generator while the blast is admitted in the center. The blast is turned on for about three minutes before the oil at a pressure of about 9 ins., at the end of this time the oil is turned on at a pressure of about 8 lbs., the atomizing steam at 35 lbs. The heating period is about twelve minutes; at the end of this time the blast is cut off, the valve opened con- necting with the wash-box, and the gas-making oil is injected as before, with steam, through another set of nozzles. The gas- making nozzles are located both in the primary generator and also in the top of the secondary generator, so that the flow of 244 ELEMENTS OF INDUSTRIAL CHEMISTRY oil through the machine can be regulated according to the heat carried in the checker- work in all parts of the set. The oil is admitted to the top of the primary generator at first quite rapidly, it is then gradually reduced during the run until at the eighth minute it is flowing at about one-third the initial rate per minute. The oil is admitted to the secondary generator at a slightly slower rate and is gradually reduced in the same pro :ortion. The last two minutes of the run the oil is cut off and the steam pressure is raised to 100 lbs., and allowed to remain at this pressure for two minutes in order to purge the machine. The heats in the machine are controlled by the appearance Fig. 83. of the overflow from the wash-box, the presence of tar showing that the heat is too low, while lampblack from the overflow in the first scrubber shows that the heat is too high. The make of gas per minute during the run is a very good indication of the heats carried and is an indqx to the proper length of the run. In the larger machines about 16 per cent of the total oil used is burned during the heating runs; so that where the total oil per thousand runs abou: 8^% gallons, about 1-^- gallons per thou- sand are used during the heating run and 7^ gallons during the gas-making run. In general this gas resembles coal gas in many of its con- stituents much more closely than it does water gas. But there ILLUMINATING GAS 245 is eveiy reason why this should be so, as both of these gases are formed by the pyro-condensation of hydrocarbons. The formation of the all-oil water gas is almost identical with the second and third stages of the coal-gas distillation except that in the case of the oil gas the temperature conditions and time of contact are under much more exact control. In general all that has been said previously in reference to the decom- position of the hydrocarbons applies with equal force in the manufacture of oil gas in this apparatus. PlNTSCH GAS. Another commercial adaptation of oil gas is that known as Pintsch gas. Iintsch gas is simply an oil gas compressed to about ten atmospheres and was developed origi- nally for the lighting of railway passenger cars. The Pintsch patents were taken out about 1870. In this system the oil is first decomposed in a double iron retort, set in a regular coal-gas bench, an outline sketch of which is shown in Fig. 84. The oil is introduced at the front of the upper retort and falls upon a movable tray, which collects most of the car- bon formed. The gas and vapors thus produced pass to the back of the upper retort down and out through the lower retort to a hydraulic main located in front cf the bench. The crude gas is passed through a dry scrubber, con- denser and purifier and after metering is collected in a low- pressure holder, very similar in all respects to the processes employed in condensing and purifying coal gas. The gas is then compressed, generally in a two-stage compressor, into the storage cylinders. Blau GAS. Another modification of the Pintsch gas is known as Blau gas. In this process the oil is decomposed in the retorts, as in the manufacture of Pintsch gas. The gas is purified and then compressed to 100 atmospheres, so that the greater portion of it liquefies. Under this pressure the liquefied hydro- Pic. 84. 246 ELEMENTS OF INDUSTRIAL CHEMISTRY carbons probably absorb and hold in solution some of the olefines and paraffines that would normally be gases at this pressure. The oil is gasified at rather a lower temperature than that ordi- narily employed in the manufacture of oil gas. The fixed gases that are left after compression are used in operating the machinery necessary in the manufacturing operations. The liquefied gas has a specific gravity referred to water of .59. The liquid is sold ordinarily in seamless steel flasks that hold 45 and 10 kg. The gas is first expanded from 100 atmospheres down to about 10, and is then expanded again to 10 or 12 ins. water pressure. One gallon of the liquefied gas will yield about 28 cu.ft. of expanded gas. GASOLINE GAS. Gasoline gas is a mixture of atmospheric air and light hydrocarbon vapor in varied percentages generally above the explosive limit. This gas has been developed to meet the requirements of isolated localities where the quantity of gas required is small, so that the installation of the usual form of coal or water-gas apparatus would not be profitable. There are two general systems used in its manufacture ; one system operates in the cold while the other system employs heat to aid in the vaporization. Gasoline or carbureted-air gas differs from the ordinary forms of coal gas, water gas or oil gas, due to the fact that it is a simple mixture of the vapors of a liquid hydrocarbon which is not changed chemically in the vaporization. In the cold process, where the air is not heated, a very light grade of gasoline must be employed, while in the system employing steam or other source of heat to assist in the evaporation the less expen- sive naphthas may be used. ACETYLENE. The use of acetylene as an illuminant in small towns and for isolated plants has developed to a very consider- able extent during the last few years, owing to the standardization that has taken place in the manufacture of calcium carbide. In producing this gas it is only necessary to treat the carbide with water, held in a suitable container, and pass the gass through pipes to the service point. CHAPTER XI COAL TAR AND ITS DISTILLATION PRODUCTS COAL TAR. This is the black, foul-smelling, onV mixture which separates from the gases formed in the destructive dis- tillation of coal. The raw tar is composed of light oils, pyridine bases, phenols, naphthalene, anthracene, heavy oils, pitch, com- plex organic compounds insoluble in benzene, and known as free carbon, water, ammonia, and dissolved constituents cf the gas. As there is little prospect that the principal object of the destruct- ive distillation of coal will be the production of tar, there has been little research upon the conditions necessary to produce tars of the most desirable properties. It varies greatly in com- position and may be divided into retort-gas tar and oven-gas tar, according to its method of production. Retort-gas Tar. This tar is obtained as a condensation product in the hydraulic mains, scrubbers, or condensers, in the manufacture of coal gas for illuminating purposes. It is less fluid and contains less of the lighter hydrocarbons, more naphtha- lene, anthracene and their accompanying oils, and more free car- bon than tars from some other sources. The composition varies with the heats and coals employed. The lower the carbonization temperature of any coal the more fluid the tar and the lower the free carbon content. The specific gravity of the dry (water-free) tar varies from 1.10 to 1.25 or even somewhat higher. It contains from 18 to 40 per cent of free carbon and yields on distillation from 1 to 5 per cent of light oil to about 200° C, 30 to 50 per cent heavy oil, including naphthalene, anthracene, phenols, and accompanying oils, from 200° C. to the coking tem- perature, and from 45 to 65 per cent coke; or if distilled to pitch the yield would be light oil 1 to 5 per cent, heavy oil 25 to 40 per cent, and pitch 50 to 75 per cent. Oven-gas Tar. This material is obtained as a by-product in the distillation of coal in retort coke ovens. It is similar to retort-gas tar, except that it is more fluid. It contains more of 247 248 ELEMENTS OF INDUSTRIAL CHEMISTRY the hydrocarbons, and considerably less free carbon, which latter usually runs from 5 to 20 per cent. The composition of course changes with the coal, with type of oven, and with the coking temperature. Producer-gas tar, owing to the method of production, usually consists of large percentages of water and free carbon, together with a very small amount of oils and yields, when distilled, a very friable pitch entirely unsuitable for the purposes for which pitch is made, and therefore of no commercial importance. * Blast-furnace tar is essentially a low-heat tar, being pro- duced in blast furnaces fed with coal instead of coke and the gases liberated from the coal come in contact with a cooler zone as soon as formed. It usually has a specific gravity between 0.94 and 1.000 and contains more phenoloid and basic sub- stances than ordinary coal tar. These phenoloid substances resemble those obtained from the destructive distillation of wood and lignite and amount to from 5 to 10 per cent of the tar, while 1 to 2 per cent is the usual amount in ordinary coal tar. It also contains from 2 to 5 per cent of basic bodies and about 16 per cent of paraffine oils which solidify on cooling. These tars are entirely different from the ordinary coal tar and not suited for the same purposes. Water-gas Tar. From the manufacture of carbureted water gas for illuminating purposes, the car obtained differs mainly from coal tar in the entire absence of tar acids (the phenol group), ammoniacal liquor, and in the small amount of free carbon present, which is usually less than 2 per cent in these tars. The specific gravity varies from 1.005 to 1.15, but is usually between 1.03 and 1.12 in tars from the larger and more care- fully supervised works. Dry water-gas tar, when distilled, yields from 5 to 15 per cent of light oil to 200° C, 30 to 50 per cent of heavy oil from 200° C. to pitch, and 35 to 60 per cent of pitch. Pintsch or Oil-gas Tar. This comes from the manufacture of oil gas used for railway lighting. It is similar to water-gas tar, but sometimes contains much larger amounts of free car- bon, frequently 25 to 30 per cent, or even more. APPLICATION OF TAR. Tar is little used in the crude state, but is refined by removing the water and more or less oil by distillation. In this condition it is used to saturate roofing felt, to coat roofs laid with plain tar felt, as a cheap paint, and COAL TAE AND ITS DISTILLATION PRODUCTS 249 to coat wood which is to be buried in the ground. With more oil removed it is used as a binder in asphalt pavements and SandFIlIing Fig. 85. Fig. 86. tar-macadam roads. With an admixture of water, it is used to sprinkle telford and macadam roads to prevent dust. 250 ELEMENTS OF INDUSTRIAL CHEMISTRY Tars are separated into their valuable constituents by dis- tillation. The stills, Figs. 85 and 86, may be either horizontal or vertical cylinders set in brickwork and heated by direct fire similar to steam boilers. Stills vary in size and in design. Those with a capacity of 10,000 gallons are not uncommon, but most stills have less than half this capacity. The European practice is to use vertical stills with convex top and concave bottoms. The top and sides are constructed of half-inch boiler plate, while the bottoms are frequently from 1 to 1} ins. in thickness and are protected from the direct heat of the fire by a brick arch. The hot gases from the fire are led around the lower half of the still in flues. The American practice is to use horizontal stills heated on slightly less than half of their cylindrical surface protected by an arch directly over the fire and so designed that the portion of the shell heated may be readily replaced when damaged. The still is equipped with the usual worm, which may be made of either cast- or wrought-iron pipe with receivers, and with a pitch cooler. The objections to cast-iron worms are their numerous joints and greater weight. Since the development of electric welding wrought-iron worms may be made of any de- sired length with no joints to give trouble. Where high-carbon tars are worked, stills must be provided with suitable means of agitating to prevent the carbon becoming caked upon the heated part of the shell. Drag chains were formerly employed for this purpose, but compressed air or superheated steam is now more often used, as they serve to keep the still clean and assist in removing the high-boiling oils. DISTILLATION OF TAR. The operation of tar stills varies considerably at different works. The receivers are changed at different temperatures and therefore the products are not uni- form. In America it is the more common practice to fraction as light oil until the distillate commences to sink in water and as heavy oil or creosote oil from that point to pitch. Very little, if any, anthracene is made in this country, as most of the tar is run only to soft pitch with a melting-point between 60 and 80° C. The European practice is different. From four to six frac- tions are taken before the pitch and a very large percentage of the tar is run to hard pitch. The following will show the most common fractions and the temperatures of the " cuts." GOAL TAR AND. ITS DISTILLATION PRODUCTS 251 American Practice European Practice Light oil, or \ Till oil sinks in water First light oil, or \ T 11n o p Crude naphtha J about 200° C. First runnings ( ±0 iiU ^- SdtgMoil }noto2oo»c. Heavy oil, ] 90n o r Carbolic oil 200 to 240° C. Dead oil, or [ ZTLi+lL Creosote oil 240 to 270° C. Creosote oil J to pitch Anthracene oil 270 to pitch Pitch Residuum Pitch Residuum The tar is usually charged into the hot still (from the pre- vious run) . The fire is lighted when the charging is about half com- pleted. The fire must be carefully regulated till the rumbling or crackling noise in the still ceases, which denotes that the water has all been driven over. The firing can now be pushed so that the distillate runs at the rate of 200 to 400 gallons per hour. When the desired grade of pitch has been obtained, the fire is drawn and the pitch is run or drawn into the pitch cooler, a closed tank with a manhole having a loose-fitting, free-opening lid which, while it acts as a safety valve, prevents free access of air. The pitch, when sufficiently cooled, is filled directly into barrels for shipment or storage. The fraction to 200° C. contains water, ammoniacal liquor, crude benzols, pyridine bases, and a part of the naphthalene, heavy oil and phenols. The second fraction from 200° C. to soft pitch (about 270° C.) consists of phenols, naphthalene, heavy oil and some anthracene, though the greater part of the anthracene comes over above 270° C. If the distillation is con- tinued to hard pitch, a cut could profitably be made at about 270° C.j above which point most of the anthracene and anthra- cene oil would be obtained. The treatment of the fractions as obtained by the American practice only will be considered with incidental allusions to the foreign methods. The light oil fraction is allowed to settle and the ammoniacal liquor or water is drawn off. The pyridine bases are not as a rule recovered in this country, but are allowed to remain in the heavy oil with the phenols. If it is desired to separate them the light oil is agitated with dilute sulphuric acid in a lead-lined cone-bottomed tank, fitted with a lead-covered propeller, usually supported entirely outside the tank, which mixes the contents. After the pyridine bases have been removed the oil is trans- ferred to a similar iron tank, in which, in order to remove the phenols, it is treated with caustic soda solution of about 1.116 252 ELEMENTS OF INDUSTRIAL CHEMISTRY specific gravity. After the carbolates have been drawn off, the oil is charged in a still, of 2000 to 3000 gallons capacity, similar to a tar still, but having in addition a column and con- denser for fractionally condensing, Fig. 87, and washing the INVENT PIPE COLUMN OR DEFHLECMATOR EH . WWATER OVERFLOW . THERMOMETER /:? "^ 9 COILS 2)i"PIPE -COOLER WORM -2)4 WATER OVERFLOW Fig. 87. vapors coming from the still. The following fractions are usually taken : Crude 90 per cent benzol, to 95° C. Crude toluol, 95 to 125° C. Crude solvent naphtha, 125 to 170° C. Heavy naphtha, 170 to 200° C. Residue. The residue consists of naphthalene, heavy oil, and phenols if not previously extracted. It should be added to the second fraction from the tar still. In some works only three fractions are made in the light- oil still, the first two being combined and this fraction being- subjected before washing to another distillation in a steam- COAL TAR AND ITS DISTILLATION PRODUCTS 253 heated column still. The fraction consisting of benzene, toluene, xylene, and their impurities, would be cut as follows: Crude 90 per cent benzene up to 95° C. Intermediate fraction (which is rerun) 95 to 105° C. Crude toluene 105 to 120° C. Crude solvent naphtha added to that fraction . 120 to 125° C. The purification of these fractions consists in the polymeriza- tion of the unsaturated compounds and the removal of the dis- solved polymerized hydrocarbons by distillation. The oil is treated with small portions of sul- successive sp.gr. in an phuric acid, 1.835 agitator tank, Fig. 88, similar to the one used for pyridine extrac- tion. vThe agitator for washing with strong acid can be lined with lead. A better construction is of cast iron with leaded joints of the bell-and- spigot type, similar to those used on ifDiaxrraceMeij rieadftpe pron Pipe Water In lef -IironPipeWater Outlet to Dram | 'Standard CIPipe cast-iron water pipe, and with a conical bottom to permit of com- plete separation of the acid and the oil. The several small portions of acid are agitated with the oil, allowed to settle for a few minutes and the acid tar composed of spent acid and polymerized hydrocarbons drawn off. Care must be taken to remove the acid tar completely after the final application of acid. The acid necessary for a satisfactory purification of the oil shou.d be determined by a laboratory test after each addition of acid. If too little acid is used the tarry products are apt to separate and clog the draw-off, and if too much is used the spent acid will be very thin and fluid. A good wash is usually obtained when between \ and f of a pound of acid is used per U. S. gallon. This is applied in four to six successive portions. In this way a better wash and a larger yield will result together with a saving of acid. Formerly it was usual to wash Fig. 88. 254 ELEMENTS OF INDUSTRIAL CHEMISTRY the oil two or three times with water, but as this serves only to reduce slightly the caustic soda necessary to remove all the acid remaining in the oil, and as it adds materially to the time required to complete the wash, it has been in most cases discontinued. The oil is finally treated with sufficient 10 per cent caustic soda solution to remove all traces of the acid. The washed oil is dis- tilled in a steam-heated still, which leaves behind, as a viscid mass, the polymerization products that were dissolved in the oil. This residue is reported to have some application in waterproofing paper. The final fractioning of the refined oils is conducted in steam- heated stills with columns similar to those used for the rectifica- tion of spirits. They consist of a series of plates, inclosed in a shell, with nozzles extending from their upper side, over which are inverted saucers or caps so designed as thoroughly to mingle the ascending vapors with the descending condensed oils and yet prevent foaming as far as possible. These columns were formerly made entirely of copper, as is the practice in alcohol rectification, but cast iron, wrought iron and steel are better materials, cost less and are not acted upon by the sulphur compounds contained in the oils. Columns fre- quently have as many as thirty sections to do the best work, though by far the greater part of the fractioning is done in the first ten or twelve sections. BENZOL. The crude benzols from light oil are colorless when freshly distilled, but they soon become a pale straw color and continue to darken for some time. They are known in the trade as crude or " straw-color " benzols of the various grades. Fraction. Specific Gravity. 5-10% 90% Dry. Flash-point. Straw-color benzol Crude 90 per cent benzol . Straw-color toluol } 0.860-0.875 0.860-0.875 0.870-0.885 0.925-0.940 80° C. 100° C. 130° C. 160° C. 100° C. 120° C. 160° C. 2.10° C. 120° C. 140° C. 190° C. 220° C. below 0° C. below 0° C. Crude solvent naphtha . 22-26° C. 43-45° C. These crude oils are chiefly used as solvents where their odors are not objectionable. Crude solvent naphtha and heavy naphtha are also used as thinners in certain cheap paints. Of the refined oils three are separated in a pure state, C.P. COAL TAP AND ITS DISTILLATION PRODUCTS 255 benzol, C.P. toluol, and xylol. The first two distill entirely within 2° C, while the last is a mixture of the three xylenes and distills from 135 to 145° C. C.P. benzol or benzene, has sp.gr. .875 to .884. Freezing- point 4° C, boiling-point 80° C. It should distill completely within 2° C, be colorless and have the characteristic odor. It should not be colored on shaking with one-half its volume of C.P. sulphuric acid, 1.84 sp.gr., and the acid should be only slightly colored after standing for half an hour. It should be free from thiophens, contain only traces of carbon disulphide and from 1 to 3 per cent of inert paraffines. TOLUOL. C.P. toluol or toluene has sp.gr. .865 to .876, boiling-point 110° C. It should be colorless and have the charac- teristic aromatic odor. It should not be colored by shaking with one-half its volume of C.P. sulphuric acid, sp.gr. 1.84, and the acid layer should not be colored deeper than a pale straw after standing for a half hour. In other respects it should answer the specifications for C.P. benzol. The following refined commercial fractions are colorless and should not be colored by shaking with one-half their volume of C.P. sulphuric acid, nor should the acid layer become colored deeper than a straw color in one-half an hour except in the case of 160 and 200° naphthas, when the acid may become colored deep red. Fractions Specific Gravity. Temperatures Noted in Distillation. 80° C.-90 C. 100° C. 120° C. -10%-90-95% dry 0% 90-92% dry 100° c. 120° C. 135° C. . 50-52% 90-92% dry 10-15% 90-95% dry 130° C. 160° C. 185° C. 0-10% 90-92% dry 160° C. 200° C. 215° C. 10-20% 90-92%, dry Flash-point 100% benzol 90% benzol 50% benzol Commercial toluol. . . Solvent or 160° naphtha 200° naphtha . 870-0 . 880 . 865-0 . 880 0.862-0.876 . 865-0 . 875 . 860-0 . 870 0.879-0.882 below 0° C. below 0° C. below 0° C. below 0° C. 22 to 26° C. 42 to 45° C. The last two are not so well washed, therefore the acid be- comes more deeply colored. CREOSOTE OR HEAVY OIL. The fraction from the tar still between 200 and 270° C, and sometimes even higher, contains most of the phenols, naphthalene, anthracene, and the accom- panying oils. Anthracene will be found in large quantities only when the distillation of the tar is carried to hard pitch. 256 ELEMENTS OF INDUSTRIAL CHEMISTRY If it is desired to remove the tar acids (phenols) the oil is agitated at a temperature of 50 to 70° C. with sufficient caustic soda solution sp.gr. 1.116, to combine with them. The alkaline liquor is allowed to settle and is drawn off, after which the oil is run into shallow tanks or pans, where a large part of the naph- thalene separates out as a mass of crystals when the oil cools. It is possible to treat the oil with successive portions of the caus- tic soda solution so as to obtain, first, an alkaline solution in which sodium phenolate preponderates; second an equally pure sodium cresylate; and third an unsaturated solution of caustic soda and sodium cresylate which is used as the first portion on the succeeding charge. The portion containing principally sodium phenolate is boiled by direct steam, and air is passed through the boiling liquid to remove naphthalene, hydrocarbon oils, and pyridine bases. In some works the distillate from the boiling carbolate is collected and worked for pyridine and naphtha, in which case the boiling is done by a fire-heated still instead of by direct steam. The distillate is collected until the purification is nearly complete, when the manhole is opened and direct steam and air blown through the liquor. After this treatment the carbolate of soda should be soluble in water without turbidity. The purified phenolate solution is allowed to become cold and is saturated with carbonic acid gas, usually obtained from the flue gases from the steam boilers. Finally, after the carbonate of soda solu- tion formed has been drawn off, the decomposition is completed, in a lead-lined tank, by a little dilute sulphuric acid, which also aids the separation of the phenol from the aqueous solution. The sodium sulphate solution is carefully and completely drawn off. The crude phenol thus obtained contains from 20 to 25 per cent water and tar. These are removed by distillation in a still similar to a tar still, although much smaller. The dry, crude phenol is fractioned in column stills heated by direct fire or super- heated steam, but otherwise the stills are similar to those used for benzols. These yield, first, a crystallizable phenol, second, a fraction not sufficiently rich in phenol to crystallize, and a third fraction containing principally cresols. The fractioning of the crude phenols is conducted at reduced pressure at some works. By this process, owing to the low temperature of the distillation, a larger yield of phenol is obtained. The crystallizable fraction is further purified by repeated crystallization with the aid of refrigeration and with the addition COAL TAR AND ITS DISTILLATION PRODUCTS 257 in the last crystallization of water to dilute the cresols present. Finally, these purified crystals are redistilled, condensed in block- tin worms and collected in tin receivers so arranged that they can be heated to melt the phenol in order that it may run in a liquid state into containers. A properly purified phenol will remain white for more than a year, showing no trace of the red color commonly seen in crystal carbolic acid. The second portion of the alkaline liquor from the treatment of the dead oil, containing largely cresylate of soda, is saturated with carbonic and sulphuric acids in the same manner as is the portion rich in phenol. It is not customary to boil the cresylate of soda to remove the oils and pyridine bases unless it is desired to make pure cresol. The crude cresol is freed from tar and water by distillation and is then marketable as 95 to 100 per cent cresylic acid. PHENOL, carbolic acid, hydroxy-benzene, CeHsOH, w T hen pure, is a white, crystalline mass, with sp.gr. 1.084 at 0° C, melting at 42° C., boiling at 182° C, having a characteristic odor and when very dilute a sweetish taste. It is soluble in all proportions in alcohol, ether, chloroform, glacial acetic acid and glycerine. It liquefies on the addition of 14 to 15 per cent of water, and thus becomes the No. 4 car- bolic acid of commerce. It dissolves in about 20 parts of water at 25° C. It is a corrosive and irritant poison. Undiluted alcohol is one of the best washes for phenol burns. Carbolic acid is largely used in medicine and surgery as an antiseptic and disinfectant and in the arts in the manufacture of dyes. It is employed in the manufacture of picric acid, trinitrophenol, which finds a large use in the manufacture of high explosives, and is also used as a yellow dye. CRESOL, cresylic acid, hydroxytoluene, C6H4CH3OH, is a mixture of three isomers, has a sp.gr. of 1.032 to 1.038 at 25° C, and distills between 190 and 205° C. It is used as an anti- septic and disinfectant and is much less corrosive than phenol and is a more efficient antiseptic. The three isomers composing cresol have the following prop- erties : ORTHOCRESOL, orthocresylic acid, ortho-oxy-toluene, ortho- methylphenol, CefeOHXCHs), with the CH3 and OH groups in the (1-2) position, is a white crystalline substance melting at 28 to 30° C, into a colorless liquid and boiling at 187 to 258 ELEMENTS OF INDUSTRIAL CHEMISTEY 189° C. It is soluble in thirty parts of water, in alcohol, ether, chloroform, and the caustic alkalies. METACRESOL, metacresylic acid, meta-oxy-toluene, meta- methylphenol, has the CH3 and OH groups in the (1-3) position and is a colorless liquid, sp.gr. 1.0498 to 1.05 at 0° C. It boils at 202° C, is soluble in alcohol, ether, chloroform, the caustic alkalies, and slightly in water. PARACRESOL, paracresylic acid, para-oxy-toluene, parameth- ylphenol, with the CH3 and OH groups placed in the (1-4) position, is a white crystalline mass, melting at 36° C, and boiling at 198° C. It is soluble in alcohol, ether, chloroform, caustic alkalies, and slightly in water. XYLENOL, di-methyl-phenol, hydroxj^-xylene. The six possi- ble isomers are probably present in the fraction of crude cresylic acid boiling between 210 and 230° C. and which has a sp.gr. between 1.02 and 1.03 at 15° C. They are on the whole con- siderably more soluble in water and less corrosive than the cresols. They are principally used in disinfectants of the " cre- olin " type on account of their high phenol coefficient, which is between ten and twelve. They are not generally separated from the cresylic acid except when pure cresols are made. NAPHTHALENE. The heavy oil fraction, if the removal of the naphthalene is desired, is run into shallow tanks or pans, either from the still or after the tar acids have been extracted and allowed to become cold, when the larger part of the naph- thalene crystallizes. The oil is drawn off and the crystals are either shoveled into piles to drain, or are passed through a centrifugal which leaves the crystals nearly dry and in com- dition for market as " drained creosote salts " or crude naph- thalene. Refining naphthalene consists in freeing it from adhering heavy oil and from unsaturated, easily oxidized compounds. The crude material should be in a coarse crystalline condition to allow of the proper extraction of the oil. If it is in a slimy state it should be recrystal'lized. The crystals are either washed with hot water in centrifugals, which removes the larger part of the adhering oil, or they are hot pressed in hydraulic presses. The latter process is more expensive and less efficient than the former. After this operation the naphthalene should have a melting-point of not less than 76° C., and will still contain from 4 to 6 per cent of oils. The partly purified naphthalene is now distilled, to remove the tarry bodies that have been COAL TAR AND ITS DISTILLATION PRODUCTS 259 carried forward from the original tar. This process is conducted in plain, externally fired iron stills, similar to tar stills, but with lead worms. The distillate is kept in a melted state and run into lead-lined agitators similar to those used for benzols, and washed with sulphuric acid, 1.835 sp.gr., several waters, and finally with caustic soda solution, of about 1.16 sp.gr. Great care must be taken to remove as much as possible of the acid before the first water is added, so as to prevent the tarry polymerization products from being redissolved by the naphthalene. The soda solution is drawn off completely, as small amounts of soda will cause the bottom of the still to be rapidly burned out. It is neces- sary to reject the first portion " heads," and the last portion, " tails," of the distillate from the final distillation of refined naphthalene, as the " heads " are discolored by the washings of the worm and with water containing dissolved bases, metallic u u u u u — o — d — cm — n — cm — n — cm a n n n n n n n n n n n L U U 11 U II UU — lLUUiiUUiiUU Fig. 89. salts, etc., while the oils are concentrated in the " tails." The sum of the rejected portions should not exceed J to 1 per cent of the distillate. The water- white refined naphthalene is run into shallow pans to cool, when it can be broken up and sold as lump, or is run Into copper tanks heated by steam, from which it is available for casting into balls, etc., or for use in the subliming pans. Sub- liming pans, Fig. 89, are large shallow iron tanks heated by steam and connected by an iron hood with a smoothly sheathed room in which the sublimed vapors condense in transparent plates, " flake naphthalene." About 150° C. seems to be the most satisfactory temperature in the subliming pans. A higher tem- perature can be economically employed in winter and a some- what lower one in summer. Naphthalene, CioHs, is a solid hydrocarbon at ordinary temperatures, melting at 79-80° C, and boiling at 218° C. Its specific gravity in the solid state 260 ELEMENTS OF INDUSTRIAL CHEMISTRY is 1.151 at 15° C. and in the liquid state is 0.9778 at 80° C. It volatilizes at ordinary temperatures and very readily on the steam bath. It crystallizes in transparent rhombic plates, which are slightly soluble in hot but insoluble in cold water. It is very soluble in chloroform, benzene, ether, alcohol, methyl alcohol and paraffine. The purity of refined naphthalene is indicated by the faint purple or pink tint when a lump is dissolved in hot concentrated sulphuric acid. If the acid is turned a deep red the sample is likely to become discolored on standing. Naphthalene is used as the starting-point of several classes of colors, including nearly all of the azo-colors and for artificial indigo, in candles, cellu- loid, as a substitute for camphor to prevent moths in woolens, and to some small extent as a gas enricher in lights of the albo- carbon type. It readily nitrates directly to mononitro naph- thalene, which crystallizes in yellow needles, with sp.gr. 1.331 at 4° C, melting at 56° C, and boiling at 304° C. It is easily soluble in alcohol and petroleum oils. Its principal uses are the manufacture of certain smokeless powders and to remove the fluorescence from petroleum oils, for which latter purpose from 2 to 3 per cent is used. ANTHRACENE. This oil is the portion of the distillate from coal tar which vaporizes above 270° C. At this temperature a cut should be made if the distillation is carried to hard pitch. This oil boils between 250 and 400° C, and has a specific gravity of nearly 1.1. Its color is yellowish-green when first made, but it darkens to almost black. It contains besides anthracene, naphthalene, methylnaphthalene, pyrene, acridene, phenanthra- cene, fluorene, etc., all of which are solids, except methylnaph- thalene, and a mixture of oils of which we know very little. The anthracene fraction is run into shallow tanks and the solid compounds separate out on cooling. This process requires from one to two weeks. Refrigeration has been tried to shorten the time, but it makes the oils more viscid and the separated crude anthracene much more impure. The semi-solid mass is transferred to bag filters or to a filter press and as much as possible of the oil driven out by compressed air. The nearly dry cakes from the bags or filter press, containing about 10 to 15 per cent anthracene, are subjected to a pressure of from 50,000 to 70,000 lbs. in hydraulic presses so arranged that they may be kept hot by steam coils or steam-heated plates. This treatment brings the anthracene COAL TAE AND ITS DISTILLATION PRODUCTS 261 content to from 25 to 35 per cent. These press-cakes are ground and purified by washing in a closed agitator with hot solvent naphtha from the fight oil. Lower boiling benzols have been used for this purpose, but they dissolve the anthracene itself. The whole charge, when thoroughly mixed, which may require several hours, is run into a closed filter and the solvent removed by compressed air. P;yridme bases are said to be a better solvent for the anthracene impurities than solvent naphtha and is said to yield 80 per cent anthracene, while 70 to 75 per cent is the limit with solvent naphtha. A somewhat more pure anthracene is produced by the sub- limation of the washed material. The subliming pans are similar to those used for naphthalene except that they are heated by fire and have jets of superheated steam impinging upon the surface of the melted anthracene. The vapors are condensed by water jets. The oil from the first crystallization of the crude anthracene is distilled in a clean still till crystals appear upon cooling the distillate, when the residue containing the anthracene is run into pans and t reated the same as the original fraction. When the oil will jdeld no more anthracene it is used to soften, " cut back," pitch, as " Carbolineum Avenarius," for the treat- ment of timber, and mixed with the creosote oil. Anthracene, C14H10, was discovered by Dumas and Laurent in 1832 and recognized as a characteristic constituent of coal tar by Fritzsche in 1867. It boils at 363° C, melts at 213° C, and has a specific gravity of 1.147 at 15° C. It crystallizes, when pure, in white or yellow rhombic plates with a blue fluorescence. It is soluble in benzene, ether, chloroform, carbon bisulphide, and in hot alcohol, but only sparingly soluble in cold alcohol. It is slowly converted by sunlight into paranthracene. It is of great importance commercially as the starting-point for the synthetical alizarines, CHAPTER XII THE PETROLEUM INDUSTRY ORIGIN OF PETROLEUM. The origin of petroleum has been the subject of much discussion among scientists throughout the world, the theories set forth being divided into two groups, the inorganic and the organic. The inorganic theories consider petroleum to have been produced by the reaction of inorganic substances. Berthelot believed it to have been formed by the action of steam and carbon dioxide on highly heated alkali metals, which, according to DaubreVs hypothesis, were supposed to exist in the depths of the earth. Mendeleeff believed it to have been formed by the action of water on highly heated metallic carbides. These theories have been supported by laboratory experiments, yet they are not in accord with the geological con- ditions under which petroleum is found. The organic theories that petroleum has resulted from the decomposition of either animal or vegetable matter, or both, comply more fully with the views held by the geologists, and have also been supported by laboratory experiments. Peckham believed that petroleum was produced by the slow distillation of animal and vegetable matter at a low temperature; Phillips and Sterry Hunt, that it was due to the decomposition of vege- table matter under water and in the absence of air. Orton con- sidered Pennsylvania petroleum to have been derived from organic matter of bituminous shale, probably vegetable; and Canadian oil produced from limestone, probably animal. CONSTITUTION. Crude petroleum consists essentially of a complex mixture of hydrocarbons of different boiling-points, often accompanied by small percentages of oxygen, sulphur, and nitrogen compounds. The oils produced from different localities often vary widely in chemical composition, but they are all refined by the same general methods. The oil refiner divides petroleum into two general classes, viz., the " parafnne-base," those yielding solid hydrocarbons of the paramne series CnH2n+2; and the "asphaltic," or those rich 262 THE PETROLEUM INDUSTRY 263 in asphalt and containing practically no solid paraffines. There is, however, no sharp line of distinction, as some of the oils from Kansas, Oklahoma, Northern Texas, and Illinois contain both asphalt and paraffine. LOCALITY. The oil from Pennsylvania, of the Appalachian field, which includes Pennsylvania, New York, southeastern Ohio, West Virginia, and Kentucky, is generally considered the best grade of petroleum produced in large quantities. This is a " paraffine-base " oil, but contains small quantities of the olefin series, C2H2H, the benzene series, C n H2n-6, and traces of the naphthene series, which are hydrogen addition products of the benzene series, and isomeric with the olefin series. The color by transmitted light varies from amber to red, and by reflected light is green, due to the so-called " bloom " or fluorescence. In specific gravity it ranges generally from .8641 to .7821 (32.0 to 49.0° Beaume). It contains very little sulphur (.06 to .084), practically no asphaltic matter, and gives a good yield of gaso- line, illuminating oils, and paraffine wax. The Canadian oil and that from Lima, Ohio, are also paraffine- base oils; but as they are high in sulphur (Lima oil, 0.6 per cent, and Petrolia, Canada, 0.98 per cent), the illuminating oils sepa- rated from them have to be desulphurized in order to make them merchantable. The petroleum from Illinois is lower in sulphur (.25 per cent to .32 per cent), much of it being refined without special treat- ment; but that from some pools contains asphalt as well as solid paraffine, as do some from Kansas, Oklahoma, and Northern Texas. The California oils are of the asphaltic type and are made up of a large proportion of nitrogen bases of the pyridin, or hydro- pyridian, and chinolin type. They also contain members of the terpene series, C n H2n-4, and the benzene series, C n H2 n -6, as does the oil from Beaumont, Texas. There are small quantities of petroleum produced in Penn- sylvania, West Virginia, and other localities, which possess lubricating qualities in their natural state, and need only to be strained before they are placed on the market; but, as the pro- duction is small, these oils are only of passing interest. Of the other countries, Russia is the largest producer. The oil from Baku differs chemically from the Pennsylvania oil in being made up largely of the " naphthene " series, which, accord- ing to Markownikow and Ogloblin, constitutes 80 per cent. 264 ELEMENTS OF INDUSTRIAL CHEMISTRY Smaller fields exist in Sumatra, Java, Borneo, Galicia, Rou- mania, Egypt, Persia, Africa, India, Japan, Mexico, Germany, Peru, and Italy. PRODUCTION. Crude petroleum is obtained by drilling through the overlying strata to the oil-producing sands beneath, proceed- ing in practically the same manner as in boring an artesian- water well. The depth of the wells depends on the locality. In Pennsylvania the depth varies from 300 to 3700 ft. It some- times happens in drilling, when the oil-bearing stratum is tapped, that the oil rushes out of the well with great force, due to confined gas; such a well is called a " gusher." Some of the big gushing wells of Russia have started producing at the rate of 200,000 barrels of oil per day. The famous Lucas well struck at Spindle Top near Beaumont, Texas, on Jan. 10, 1901, at a depth of from Fig. 90. 1029 to 1069 ft., is estimated to have started gushing at the rate of 70,000 barrels per day, and probably flowed 500,000 barrels before it could be tapped. Petroleum is transported great distances from the fields to the storage tanks (30,000 to 75,000 barrels capacity) of large refineries, through pipe lines of from 4 ins. to 8 ins. in diameter, the average line being 6 ins. The longest distance is from the Oklahoma field, via Kansas City and Chicago, to the seaboard a distance of about 1600 miles. REFINING. The first step in the separation of petroleum into its various products is fractional distillation, and this is modified according to the nature of the crude oil, and the prod- ucts desired. The horizontal steel stills used for this operation vary in construction, but those in general use in this country are cylindrical steel shells set in brickwork, as shown in Figs. 90 and 91, the upper half being exposed except for an iron jacket THE PETROLEUM INDUSTRY 265 covering. The largest stills of this type are about 42 ft. long by 15 ft. in diameter, with a charging capacity of about 1200 (42 gallons) barrels. They may be either end or side fired, the latter being preferable on account of the ease with which the still can be controlled. The fuel used may be either coal or oil, it being cheaper to burn oil in some cases, as in California Fig. 91. and Russia, where, owing to the scarcity of coal, oil is used almost entirely. The stills are usually fitted with domes at the top which are con ected with 12- to 16-inch vapor pipes, or " goose necks " that lead to condensers. The condensers consist of coils of pipe set in tanks, through which cold water is circulated. The pipes connecting the condenser coils with the "tail house/' some dis- tance away, are called the " running lines," and are usually pro- vided with traps for separating the uncondensed gas which is subjected to pressure in order to separate the light gravity gas- oline carried by it. The residual gas is utilized in gas engines 266 ELEMENTS OF INDUSTRIAL CHEMISTRY or burned under the stills. The running lines are intercepted in the " tail house " by " look boxes " enclosed with glass, so that the " stream " (distillate flowing from the condenser) can be watched by the stillman in charge. The method of distilling is dependent on the products desired. When petroleum is distilled by means of fire alone, the heavy vapors which condense in the top of the still drop back into the superheated oil, and are thereby partially decomposed. This de- / composition, or " cracking," causes oils of lower specific gravity than are normally present to be produced, and is called the " dry," or destructive distillation. This method is used when** large percentage of burning oils is -desired. The products when running on Pennsylvani^or parafnne-base crude oil, are: naph- tha (sometimes redistilled, for cymogene, rhigolene, petroleum spirit and gasolene), burning oils, gas and fuel oils, paraffine lubricating oils, wax and coke. Heretofore the practice has been first to " run " the " crude " to tar (about 9 to 12 per cent resid- uum) in the crude stills, and to distill the tar separately at the tar stills for paraffine or " tar " distillate (lubricating oil distillate containing the paraffine wax) and coke. The latest practice is to continue the distillation to coke in " tower stills " without interruption and separate the different raw products in one distillation. The " tower still "is so called on account of the tower-like aerial condensers connecting with the goose-neck, and interposed between the stills and water- cooled condensers. The office of these towers is one of fractional condensation. They usually consist of a top and bottom gas chamber con- nected by pipes, around which the air circulates, causing partial condensation. The vapor pipe or goose-neck carrying the hot vapors from the stills connects into the bottom gas chamber of the first tower and travels up through the pipes through the top gas chamber into the bottom of the second tower, and so on through the series to an ordinary water-cooled condenser, con- sisting of coils of pipes set in a tank of water. The towers and water condenser all connect in the receiving house (tail house) with " lookboxes," enclosed with glass so that the flow of the different streams may be observed and samples can be taken for gravity tests. The tower still has many advantages over the old style appara- tus. Condensation taking place in each tower separates what would otherwise be one product into as many products as there (F) Tar Distillate (30°BJ Cooled artificially and filter pressed at 20 to 24°P. etroleum S] (58^76°Beaur Acid Wax Tailings Coke 1 Slack Wax (95/l05°F.M.PJ Containing 30-40$ Oil Sweated _Poots Soft Wax Re-Sweated Hard Wax Washed with Naphtha, filter pressed. Naphtha distilled off and Wax filtered through Bone Black or Fullers Earth Soft Wax (almost free from oiD filtered through Bone Black or Fullers Earth Refined Paraffine Wax White Scale Wax SI. DiA [To face page 266.] Pennsylvania Onide Petroleum .:■! ■■;:■ *— «"*-* — . Petroleum Spirit Low Test Burnl Light Naphtha 8t<1( . t "skX°Sv"w Uiagkam Showing Products Obtatned ekom Pennsylvanza Chude taw™ «■ ■JSSST*'' Prepared by T. T. Gray for Rogers and Auberfs "Industrial Chemistry" and Rogers' Elements of Industrial Chemistry. THE PETROLEUM INDUSTRY 267 are towers, and therefore reduces further necessary redistilla- tion to a minimum. When lubricating oils of superior quality, such as spindle and cylinder oils, are being manufactured, it is necessary to prevent the decomposition of the crude oil as much as possible. This is accomplished by introducing steam (dry but not neces- sarily superheated) into the oil in the still by means of a perfo- rated coil. The atmospheric«pressure upon the mixture is divided between the hydrocarbons and the steam and the partial pressure on the hydrocarbons is less than the atmospheric pressure, consequently they disti.l over at temperatures lower than their normal boiling-points. The sfeam jets also keep the oil in con- stant state i of agitation, thereby preventing it from getting overheated at the bottom of the still next to the fire. This method is called the " steam " distillation; the products are: Naphtha, burning oils (less than when distilled destructively), gas and fuel oils, spindle oils, paramne wax and cylinder oils. Some refiners use the vacuum distillation, in conjunction with the steam distillation, where, by the aid of a pump, a partial vacuum is created in the still, and the hydrocarbons pass over at temperatures much below their normal boiling-points. The vacuum stills are of the same general type as the ordinary hori- zontal " crude stills, " but are smaller and heavier. Naphtha and Illuminating Oils. The chart on opposite page shows the different steps in the " dry " distillation of Penn- sylvania crude oil. The " stream " (distillate flowing from the condenser) begins running into the " tail house " under ordinary conditions at about 80° Be. (.6666 sp.gr.) ; it is practically water white in color, and is " run ,; into light naphtha (Fraction A) until it reaches 69° Be. (.6965 sp.gr.). From 69 to 58° Be. (.7035 to .7446 sp.gr.) the distillate is collected as heavy naphtha (Fraction B); but as it is more or less contaminated with some of the heavier hydrocarbons of boiling-points too high for use as naphtha, it has to be redistilled in a (( steam still " (a still heated by steam coils and steam jets). The upper fraction is added to the light naphtha (Fraction A), and the residue used for blending with the low-test burning oil which follows. The naphtha Fractions A and B, representing from 12 to 15 per cent of the crude oil, can be worked up in several different ways. They can be used for all ordinary purposes without further refining, or may be redistilled, the very volatile fractions 268 ELEMENTS OF INDUSTRIAL CHEMISTRY being condensed by extreme cold, and under pressure, thereby- separating cymogene, rhigolene, gasolene. In order to improve the odor of the naphtha it is sometimes treated with about 2 to 4 lbs. of 66° Be. commercial sulphuric acid per barrel of 50 gallons, by agitation in tall, lead-lined cone- bottomed tanks, Fig. 92, called agitators, of from 300 to 500 bar- rels' capacity, provided with me- chanical stirring gears, in prefer- ence to an air blast, in order to prevent loss by evaporation. The acid is allowed to settle and draw off into the sludge-acid tank. The naphtha is washed thoroughly with water by means of a spray and finally by agitation with water, and is then made alkaline with caustic soda of 4 to 10° Be., and finally washed with w r ater until neutral, when it is pumped into tanks and allowed to settle until bright. After this treatment it becomes known as " deodorized naphtha." To recur to the original distillation, from 58 to 43° (.7446 to .8092 sp.gr.), or as long as the stream runs good color (almost colorless) the high -test burning oil (Fraction C), is collected. It is " steam stilled " to 150° F. fire test, and the distillate put into heavy naphtha (Fraction B). The residue from the steam, still known as 150° W. W. Stock, is treated as described later. When the distillate begins to go " off color," due to cracking, it is " cut into " low -flash burning oil distillate (Fraction D), which is also steam stilled, ,the volatile fraction being naphtha of 70° Be. (.7000 sp.gr.), called " gas naphtha " from its objec- tionable odor. Gas naphtha contains a large proportion of unsaturated hydrocarbons, and goes into the cheaper grades of naphtha. The appearance of so low a specific gravity fraction at this stage of the distillation illustrates clearly the effect of the " cracking ". process. The burning oil stocks from the steam stills, consttutitin from 65 to 75 per cent of the crude oil charged, are treated ag Fig. 92. THE PETROLEUM INDUSTRY 269 the rate of 5 to 10 lbs. of 66° commercial sulphuric acid per barrel, in order to improve the color and odor, also to remove decomposition products which cause the flame to smoke when burned in lamps. The process is performed in agitators in much the same manner as with naphtha, only an air blast is used for agitation instead of a stirring gear. In order to get the full benefit of the acid, any water present must first be drawn off, and a small amount of acid added in order to remove all of the remaining water; this is agitated for from twenty to forty minutes, allowed to settle from the oil and then drawn off. The remaining acid is then added and the mass agitated for from one-half to one hour, allowed to settle from three to five hours, and drawn off. The acid treatment removes the tarry matter formed during distillation, also a large percentage of the unsaturated hydrocarbons and sulphur compounds. The acid is turned almost black after treatment, and is known as " sludge " acid. The " sludge " acid is allowed to settle from the oil and is then drawn off into tanks and delivered to the acid-separating plant for the recovery of the acid. After the separation of the sludge, the oil is washed thoroughly with water, made alkaline with caustic soda of from 4 to 10° Be. by agitation, and then washed with water until neutral; the wash water is separated and the oil pumped into settling tanks where it is allowed to settle until bright. SULPHUR CONTENT. Pennsylvania petroleum contains very little sulphur (.06 to .082 per cent), the burning oils made fiom it therefore requiring no further treatment; but when oils con- taining considerable sulphur, such as that from Lima, Ohio, Texas, and Canada, are being refined, a special desulphurizing is necessary in order to get rid of most of the sulphur compounds, which cause charring of the lamp wick, and burn with a smoky flame. There are many processes for affecting this, the two best known being the " litharge " and the " Frasch " methods. The litharge method consists of agitating the oil with a solution of litharge (lead oxide) in caustic soda; the sulphur is precipitated as a lead sulphide and drawn off. Although this method reduces the sulphur considerably, it is not as thorough as the " Frasch " process, where the oil is heated with finely divided copper, or copper oxide in " sweetening " stills provided with heavy stirring gears. The copper sulphide formed is after- wards roasted in order to remove the sulphur and the resulting copper oxide used for the next treatment. 270 ELEMENTS OF INDUSTRIAL CHEMISTRY LUBRICATING OILS. The residue (E) from the original distillation of the crude oil (10 to 12 per cent) is known as tar. It is from 21 to 22° Be., very dark in color and contains the paraffine lubricating oil and wax. In order to manufacture the lubricating oils known in the trade as " paraffine oils," the tar is first distilled destructively in stills of practically the same type as the " crude stills," only they are smaller in capacity (250 to 500 barrels). The process is continued until everything has passed over except the coke formed by the destructive distillation. At the latter part of the distillation, just before the still has " coked," a yellow, sticky, semi-asphaltic product passes over, which is known as " wax tailings"; on analysis this has been found to contain anthracene, chrysene, and other products formed by the " crack- ing " process. The bottoms of the stills often get red hot during the coking period. The coke resembles gas coke in appeara^ ce, but is more fragile. The yield from tar averages from 10 to 12 per cent, or about 1 per cent from the crude oil, and on account of its purity is used principally for making electric light and battery carbons, and also to some extent in metallur- gical processes. The distillate from tar, known as paraffine, or impressed tar distillate (Fraction F) is yellow in color and contains the wax and paraffine lubricating oils. It has a gravity of 30° Be. (.875 sp.gr.), and a solidifying point of about 70° F. due to the solid paraffines present. It is treated with 66° Be. commercial sul- phuric acid at the rate of 8 to 10 lbs. per barrel in the same manner as the treating of burning oils, the agitator in this case being heated by a steam jacket in order to keep the paraffine distillate liquid. After treatment it is delivered to the pressing plant, where it is chilled down to from 20 to 24° F. in steel shells containing stirring gears called " coolers " provided with jackets through which cold brine is circulated. A refrigerating plant is therefore necessary when refining crude oils containing solid paraffines. When the proper temperature (20 to 24° F.) is reached, it is pumped to a filter press, Fig. 93, which is pro- vided with plates covered with canvas; the oil passes through and drains off, and the wax is held by the canvas. The oil thus expressed is known as pressed tar distillate (Fraction G), and the wax separated, containing considerable oil (30 to 40 per cent), known as " slack wax," is removed from the canvas- covered plates, by scraping with " spuds," when it is carried THE PETROLEUM INDUSTRY 271 by means of conveyors under the press to the " slack-wax " tank. The pressed-tar distillate has a cold test (solidifying point) of 20 to 25° F., and is used for making all of the paramne lubri- cating oils. It is charged into the ik reducing stills/' which are the same type as the crude stills, but smaller in capacity (about 300 to 500 barrels); and the upper halves, instead of being ex- posed, are bricked in. Here it is " steam reduced " according Fig. 93. to the test desired, by firing underneath and at the same time introducing steam into the body of the oil by means of a per- forated coil placed inside on the bottom of the still. In making high-viscosity oils the distillation would naturally be carried farther than when making low-viscosity oils — as the viscosity increases with the boiling-point in the same homologous series of hydrocarbons. The first fraction, separated at 36° Be. (.8433 sp.gr.), is put into the low -test burning oil fraction; the second fraction down to 32.5 Be. (.8615 sp.gr.), being too high 272 ELEMENTS OF INDUSTEIAL CHEMISTRY in specific gravity for burning oils, and having practically no value as lubricating oil, is separated for " fuel oil." The third fraction, cut at 28° Be. (.886 sp.gr.), is used for making low- viscosity lubricating oils, as described by chart, and the fourth for medium lubricating oils. The residue, which is heavy lubri- cating oil stock of dark color, is pumped out of the still through a coil of cast-iron pipe set in water called a cooler, in order to prevent oxidation when exposed to the air. The cool oil is treated with from 20 to 50 lbs. of commercial 66° Be. su'phuric a id per barrel in an agitator of from 200 to 1000 barrels' capacity in the same manner as described under burning oils, except that the agitation is kept on longer — one to two hours — and it takes longer for the sludge acid to settle — four to six hours. After drawing off the sludge, the oil is transferred to a " lye " agitator, where most of the remaining acid is washed out by agitation with water. It is then agitated with caustic soda of from 1 to 6° Be. until a distinct alkaline reaction with phenol- phthalein is obtained. The " lye " containing s ilpho-com- pounds, formed by the acid treatment, is drawn off, and the oil washed well again with water, and finally with hot water, until a neutral reaction is obtained. The water is separated and the oil transferred to shallow tanks, where it is warmed to 150 to 160° F. by closed steam coils, and air blown up through it from a perforated coil until all the moisture is removed, leaving the oil clear and bright and ready for the market. PARAFFINE WAX. The slack wax expressed from the tar dis- tillate usually contains from 30 to 40 per cent of oil, which is gotten rid of by one of the fol lowing methods : it may be mixed with naphtha and cooled until the wax crystallizes out, and then refilter pressed; or it may be removed by the process known as sweating. The " sweaters " consist of tiers of pans arranged in rooms, as shown in Fig. 94, the rooms are heated by steam coils, each room being known as an oven. The pans are first filled ay Fig. 94. THE PETROLEUM INDUSTRY 273 with water to the level of a wire screen at A and the melted wax is charged in until the pans are full, after which cold water is circulated through coil B until the wax solidifies. The water is then drawn off from underneath the solid cakes of wax by valve C and warm water circulated through coil B and the rooms also heated by steam coils. The heat causes the oil to sweat out of the wax, and it drains off and runs into a tank. Tne oil, or " foots," thus separated, containing some soft wax, is filter pressed and worked up the same as the unpressed tar distillate. The sweated wax remaining in the pans is melted, drawn off, and delivered to the filtering plant, where it passes through bone black or fuller's earth contained in long cylindrical tanks called filters in rooms heated from 130 to 180° F. This operation removes practically all of the color. It is then molded into cakes either in pans or between hollow plates cooled by the circulation of water in apparatus known as the " Gray Wax Caking Machine." THE STEAM DISTILLATION. Spindle Oils and Cylinder Stocks. In making special high-grade lubricating oils, the distillation of the crude oil is carried on in the same manner as the destructive distillation until just before the " cracking " point is reached, when steam is introduced as before mentioned; by this method decomposition is practically prevented. The yield of burning oil is therefore much lower and lubricating oil much higher. The distillation is carried on until about 15 to 18 per cent remains in the still. The reduced stock, known as steam-refined cylinder stock, is pumped out through a cooler. The steam-refined cylinder stocks are sometimes further refined by filtration through bone black or fuller's earth and are then known as filtered cylinder oils. Cylinder oils are recognized by their high flash point and viscosity. After the burning oil fraction has been separated, the rest of the distillate, passing over during the distillation, is called "spindle distillate." It contains considerable wax, which is removed by filter pressing in exactly the same manner as with the unpressed tar distillated. The pressed spindle distillate is reduced in the same manner as the paraffine oils, except that the reduced spindle- oil stock, instead of being treated with acid, is filtered through bone black, or fuller's earth, contained in cylindrical filters of about 15 to 20 tons' capacity. The fuller's earth removes the asphaltic matter, and improves the color of the oil. The first oil running through the filter is almost colorless; but as the fuller's earth " adsorbs " the asphaltic matter, it soon loses in 274 ELEMENTS OF INDUSTRIAL CHEMISTRY decolorizing value and the oil runs darker until it reaches a point where it is not practical to filter any longer, when the operation is stopped. The oil held by the fuller's earth is washed out by allowing naphtha to filter through it, and the naphtha remaining in the filter is collected by steaming it out with an open steam jet, and running it through a condenser. The oil washed out by the naphtha is separated by distillation, and the fuller's earth is heated in a retort nearly to redness in order to dry it and burn off the asphaltic matter, when it is used over again. Vaseline and " petrolatum " are reduced stocks made from selected crude oil by careful reduction and subsequent filtration through fuller's earth, or bone black. Asphaltic Base Crude Petroleum. The refining of asphaltic base crude oil is substantially the same as described in the preceding methods, excepting the residue, which, instead of being tar, or cylinder stock, is asphalt. The burning oils are not of such good quality, a larger percentage of fuel oil is obtained, and the lubricating oils are of higher specific gravity and lower flash than those made from the paraffine-base petroleum. | SHALE OIL. In Scotland, and to a small extent in other countries, paraffine oils are obtained by the destructive distillation of bituminous shale. The formation of the oil is dependent on the decomposition of the organic matter present. Shale varies in color from dark gray to almost black, the products obtained being ammonia water (separated as a sulphate) , paraffine wax, paraffine oils, burning oils, and phenols. The shale is first reduced to very small pieces, and then distilled contin- uously in circular vertical retorts, by charging in the top through a hopper, and drawing the exhausted shale out at the bottom. Steam is usually introduced into the retort. The vapors pass through a condenser, and the crude shale oil and ammonia liquor are separated. The crude shale oil is dark in color, ranging in specific gravity from .86 to .89, and having a cold test of 90° F., due to solid paraffines. It is distilled by either the intermit- tent or continuous process to coke in practically the same man- ner as with the tar from crude petroleum, except that steam is introduced through perforated coils during the distillation process. The treatment of the various fractions, i.e., naphtha, burning oil, paraffine distillate (containing the paraffine wax) — consists of a treatment with sulphuric acid and alkali in the same manner as with petroleum; the alkali in this case, in addition to neutralizing the acid, removes the phenols which have been THE PETROLEUM INDUSTRY 275 formed during the first distillation. The phenols are liberated from the waste " lye " by passing carbon dioxide through it. OZOKERITE. Ozokerite, or earth wax, is, as the name implies, a wax-like substance found in small quantities throughout the world, usually associated with rock salt or gypsum. The prin- cipal deposit occurs in the neighborhood of Boryslaw, in Galicia. It consists largely of solid paraffine hydrocarbons, and is supposed to have resulted from the evaporation and decomposition of crude petroleum. Like petroleum, it is found in different ages, but principally in the Tertiary and the Cretaceous. The appearance and physical character vary, some grades being soft and others brittle, and the color ranges from yellow to black. The specific gravity averages from .85 to .89 and the melting-point from 130 to 156° C. The Galician ozokerite is mined by sinking a shaft and then following the vein. Thus mined, it often contains much earthy matter. The purest pieces are first separated by hand picking, and the remainder is dumped into tanks of cold water; the purer ozokerite rises to the surface and is skimmed off, and the earthy matter, containing some ozokerite, sinks to the bottom. This residue is then heated in boiling water, when practically all of the ozokerite rises to the surface and is separated. The earth is finally extracted with naphtha, thereby dissolving the last traces of ozokerite. Ceresin, or refined ozokerite, is used largely as a substitute for beeswax, and is prepared by treating with sulphuric acid, washing with water, and neutralizing with caustic soda, as described under petroleum refining, and sub- sequent filtration through bone black or fuller's earth. It varies in color from white to yellow, according to the degree of refining. Ozokerite is sometimes distilled and worked up for paraffine wax. ASPHALT. The name asphalt is generally applied to that class of bitumens found naturally in the earth in various parts of the world. It consists principally of compounds of carbon and hydrogen, also compounds containing nitrogen, oxygen, and sul- phur and some mineral matter, and is considered to have resulted from crude petroleum. Asphalt is black in color, and melts easily on the application of heat. It is partly soluble in petroleum spirit and completely soluble in carbon disulphide, the part soluble in petroleum spirit being designated " petrolene," and the part soluble in carbon disulphide, " asphaltene." The principal uses are for street paving, weather-proofing, paints and japans. The most important production is from " Pitch Lake," on the island of Trinidad, which is 135 feet deep at the center and originally 276 ELEMENTS OF INDUSTEIAL CHEMISTRY covered an area of approximately 127 acres, and is estimated to contain several million tons of asphalt. The asphalt residues from crude petroleum so closely resemble the natural asphalts that they cannot be distinguished with certainty. Petroleum asphalts are used principally for weather- proofing. CHAPTER XIII THE DESTRUCTIVE DISTILLATION OF WOOD For distillation purposes, usually but two classes of woods are used — the hard woods, such as oak, beech and maple, and resinous woods, such as the yellow pine and Douglas fir. The hard woods yield larger quantities of acetic acid and alcohol and the resinous woods more tar and oils. To obtain the highest yields of the various products sought, the proper kind of wood must be selected, and the supply should be large. TREATMENT OF THE MATERIAL PREPARATORY TO DIS- TILLATION. In hard wood distillation in the United States, the wood is cut into lengths of about 4 ft., like ordinary cord wood. In Europe the wood is often cut into short billets and then distilled. As the distillation of hard wood is now carried on mostly in connection with iron furnaces, large pieces of wood must be used in order to make a suitable charcoal. The practice with resinous woods is very variable. Some plants use cordwood, some billets, and some chips from a chipping machine called a " hog." In all destructive distillation processes, the finer the wood is cut the more quickly the distillation proceeds. ToMlistill very fine material special apparatus is needed on account of the tend- ency of the material to pack, thus preventing the heat from passing through. Usually, in a stationary retort the wood should not be cut in pieces less than a foot in length. As the cutting of the wood requires power, labor and apparatus, the advantages of rapid distillation are often offset by the expense of preparation. For the extraction of turpentine, the finer the particles of wood, the larger the yield, the quicker the distillation and the better the quality of the oil produced. If the residue is to be used for paper making, the chips should be of a suitable size to make the proper fiber. Manufacturing Processes. Charcoal Pit. For the pro- duction of charcoal only, the simplest and crudest form of dis- tillation is the common charcoal pit, Fig. 95. This method con- 277 278 ELEMENTS OF INDUSTRIAL CHEMISTRY sists of stacking up a lot of wood in a circle of 30 to 50 ft. in diameter and covering it with earth. These pits are made in various shapes and sizes. Often the wood is cut into billets and placed on end to form a circular stack of several layers, the diameter of each upper layer being less than the one imme- diately below it, thus forming a mound or " meiler." A passage- way is left to the middle of the pile so that a fire can quickly reach the center. The pile is covered with turf and sand, except near the bottom, where vents are left for the admission of air and also for the escape of the vapors. In this form of distilla- tion part of the wood is carbonized by the heat formed by the combustion of the other part. The water vapor is driven off first and the oxygen of the air present in the interstices of the wood is consumed. After distillation gets under way the air is Fig. 95. carefully excluded to such an extent that only sufficient is admitted thoroughly to char the wood without burning too much of it. Any part exposed by the earth falling in is quickly covered and only cracks enough allowed to permit the gases to escape. The charring is finished when the gases become light blue in color. The earth is then removed in small sections at a time and the charcoal quenched with water. Charcoal Kiln. In a charcoal kiln the wood is stacked either on end or lying down. A' firing passage is left as in the case of the charcoal pit. The kiln itself consists of a brick chamber, either beehive in shape or rectangular. It is usually made large enough to hold from 60 to 80 cords of wood. Some are lined with firebrick part way up the side. Doors are left in the top and bottom for charging the wood. Openings are left in the bottom for the admission of air, and some have a flue connec- tion with a stack so as to encourage the draft. Those having THE DESTRUCTIVE DISTILLATION OF WOOD 279 stacks can be forced so as to complete the distillation in two or three days if necessary. Usually it takes about eleven days to charge, distill and to cool. An illustration of the most common form of kiln is shown with stack in Fig. 96. The method of operating a kiln is similar to that followed with a pit. The fire is led to the middle of the pile and the whole allowed to heat slowly to drive out the water, then the holes at the bottom are closed and opened in such a manner as to cause the fire to spread over the entire kiln so as to avoid, as far as possible, the formation of brands or uncharred pieces. As with the pit, the presence of the light-blue vapors denotes the fact that most of the volatile matter has been driven off. The kiln is then closed up tightly with lime and allowed to cool. In both the pit and the kiln the vapors are lost, although Fig. 96. sometimes a condenser is used with a kiln. On account of the large amount of fire gases which mingle with the vapors, these condensers must be large and supplied with plenty of cooling water. The yield of valuable products is much less than when retorts are used. RETORTS. To save the volatile matter coming from the wood, various retorts have been devised, varying within wide limits, according to the kind of wood to be distilled. The simplest form of apparatus for saving the vapors formed by distillation consists of an inclosed vessel, called a retort, surrounded by a suitable furnace, to which heat can be applied by means of coal, wood, oil, gas or electricity, the vessel to be supplied with a vapor pipe connecting with some form of a con- denser. Some kind of tank is also needed in which to collect the condensed products. Where there is acid, the retorts are made of iron, the connecting pipes and condenser tubes of copper, 280 ELEMENTS OF INDUSTRIAL CHEMISTRY ^imirm/iii and the receiving tanks of wood or copper lined. To distill with steam to obtain turpentine, a furnace would not be required, but the other apparatus would be similar. The retorts used are of two distinct types, those placed horizontally in the furnace and those set vertically. Of the horizontal type there are two classes, the rectangular ovens and the cylindrical retorts. Of the vertical type there are three classes, >j^ the fixed retort, the re- movable retort and the fixed retort with re- movable cage. Of the horizontal re- torts the ovens are the most numerous — Fig. 97. They are rectan- gular in shape, flat on the bottom and slightly Fig. 97. arched on top. The bottom is supplied with rails. On the sides or back are one or more openings for the exit of the vapors to be condensed. The wood is loaded on steel cars holding about two cords each and rolled into the retort. The ovens are about 6 ft. wide and 7 ft. high and of various lengths to hold two, three or four cars each. One or two coolers are used with each of these ovens, of similar shape to the ovens but of lighter material, into which the car of char- coal is withdrawn soon after the end of the dis- tillation. Fig. 98. Some of the cylindrical retorts, Fig. 98, are made 9 ft. long by 50 ins. in diameter and will hold about a cord each. These retorts are charged and emptied by hand. An iron box mounted on wheels is used to hold the hot charcoal f and when full it is covered with a sheet-iron cover and the edges luted with sand or clay. THE DESTRUCTIVE DISTILLATION OF WOOD 281 Of the vertical retorts no particular type seems to have the preference. The retorts are usually made cylindrical and hold from | to 5 cords of wood. A convenient size is about 2 cords. The fixed retorts remain in the brickwork and are attached to the vapor pipe of the condenser by one or two pipes, preferably one at the top and one at the bottom. The movable retorts are so arranged that they can be pulled out of the furnace when the wood is charred and allowed to cool unopened. Instead of hoisting the retort itself some types use a retort with remov- able cage, Fig. 99. Only the cage is removed, and as the cage does not have to stand the direct heat of the fire, it can be made of lighter material than the re- tort and the removing of the cage instead of the retort saves the wear and tear of the brick- work. In addition to this the vapor pipes are not disturbed. CONDENSERS. The condensers used are generally of one type, although other kinds might be used. The most satisfactory seems to be the vertical tubular condenser, which consists of a vapor pipe, leading to an expanding chamber at the top of the condenser; the necessary condensing tubes, and a bottom chamber for collecting the condensed matter from the tubes— these parts are all made of copper. The whole is contained in an iron or wooden shell w r hich holds the condensing water. The top of the condenser is supplied with a cap or removable top fastened by means of a yoke or bolts so that the tubes can be easily reached and cleaned. To the lower chamber is con- nected an outlet pipe which is usually supplied with a " goose neck " or U bend, to hold back the gases, and a top opening to permit the gases to escape to the furnace. The bottom of the condenser is made sloping, so as to drain out the tar. Some- times a few fractioning elements are used to remove the tar from the vapors, so as to make the pyroligneous acid free from tar, thus saving one distillation when making gray acetate of lime. 282 ELEMENTS OF INDUSTRIAL CHEMISTRY Worm condensers have been used, and also tubes set one above the other, with removable ends, but they are not as sat- isfactory as the tubular condenser. Hard-wood Distillation. Using hard wood, destructive distillation is practiced, the products being charcoal, acetates and wood alcohol. Most of the lately erected, large-sized plants use the oven type of retort, while some of the earlier con- structed plants continue to use the small cylindrical type, and one or two the vertical type. Some large installations are said to have been made, using an oven type with chambers on each side of the oven for receiving and discharging cars of wood and charcoal respectively. An attempt is being made to introduce special retorts for distilling sawdust. To operate to the best advantage it is best to heat slowly after the liquid starts to flow from the mouth of the condenser, as overheating causes a loss of volatile matter. The first distillate begins to come over at about 320° F. and consists of furfural, water, and very little acid. The watery distillate is known as " pyroligneous acid." The percentage of acid increases with the temperature until the tar begins to distill, then it begins to drop off slightly. Meanwhile uncon- densable gases are formed which are piped to the furnace and burned. During the early stages of the distillation the color of the flame of the burning gases is blue, due to the carbon monoxide present, while later the color becomes yellow, due to the presence of the heavier hydrocarbons. The end of the operation is indicated by the falling off of the quantity of the distillate at the mouth of the condenser, by the temperature inside the retorts (about 800° F.), and by the color of the shell of the retort. The character of the distillate also indicates the end of the distillation, the tarry products being strongly in evidence. When cars or cages are used, the charcoal is with- drawn hot, thus saving the heat of the brickwork for the next charge. The conditions should be regulated so that each retort can be charged once every twenty-four hours. The Distillation of Resinous Wood. The distillation of resinous wood requires retorts varying in size and shape with the methods of operation and the products sought. The chief commercial products obtained by the distillation of resinous woods are turpentine, tar and charcoal. Soft woods yield an acid solution much weaker in acetic acid and alcohol than hard woods., thus the proportion of water distilled is greater. On THE DESTRUCTIVE DISTILLATION OF WOOD 283 this account the pyroligneous acid from resinous woods is not usually saved. There are several methods of treating resinous woods to obtain the various products. Of them the employment of steam distillation is the most general, although extraction by means of volatile solvents is sometimes used. The destructive distillation of hard wood is carried on in a very similar manner to the treatment of soft woods. The greatest variation seems to be in the method of extract- ing the turpentine. As this substance is apt to become con- taminated with tarry products, giving it a bad odor and color, considerable care is necessary to produce it. To avoid this contamination, some use two condensers, one for the turpentine, and the other for the tar and pyroligneous acid. Others collect the turpentine in one tank and the other products in another. Usually the change from turpentine to the other products is made when the temperature reaches 320° F., or when the wood begins to decompose. The operation is carried on at first at a low temperature so as not to char the wood. The turpentine and rosin exist already formed and are not products of the decomposition of the wood. By the influence of heat the turpentine distills, carrying with it part of the rosin. Sometimes steam is added to help carry over the vapors. As the heat increases part of the rosin decomposes and rosin oil distills over. When the wood begins to char, the pyroligneous acid begins to form and the distillation is carried on from this stage exactly as in the case with hard-wood distillation and the products all collected in one tank. THE STEAM PROCESS. To extract the turpentine which is already present in the wood it is only necessary to employ such agents as will volatilize it. A mixture of turpentine and water boils at 95° C, so if steam be passed through chipped wood in a suitable retort and the temperature maintained above 95° C, a mixture of oil and water vapor will distill and can be condensed in the ordinary manner. This is an old method of distilling finely divided wood that has been given much atten- tion recently. Much ingenuity has been used to devise suitable mechanical arrangements for carrying on the process successfully. The requirements are a wood- chipping and elevating system that will deliver the wood to the retorts; an easy method of discharge from the retorts for the steamed wood; and the 284 ELEMENTS OF INDUSTRIAL CHEMISTRY proper conveying machinery to remove the discharged chips to a bin or to the boilers. Considerable steam is needed for this process. Usually, a vertically placed or slanting retort is used with an opening on top for the entrance of the wood, and with a large discharging device at the bottom. Various forms of rotating retorts are also used. The retorts are connected to suitable condensers varying from one another in some details, but all based on the solvent power of some alkali or volatile oil. The alkali process consists in dissolving the rosin in soda solution and neutralizing the solution with acid to regain the rosin. This was tried on a semi-commercial scale but was abandoned in favor of the volatile solvent process. The alkali process was found to be cheaper, so the plant is expected to change back to the alkali process. The extraction with volatile solvents has been carried out on a large scale by one company and on a smaller scale by other companies. This process consists in grinding the wood, steaming out the turpentine, and extracting the remaining pine oil and rosin with a neutral volatile hydrocarbon such as gasolene. The gasolene solution is distilled in indirect steam heat to remove the light oils, followed by live steam to remove the heavy mineral oils and pine oils, a comparatively high temperature being main- tained by steam in a closed coil. All the gasolene is not recovered, the loss being one of the chief items of expense attending the operation. To Obtain Refined Products. The condensed liquor from the destructive distillation processes consists of three layers, the upper layer of tarry oils, the intermediate layer of pyro- ligneous acid, and the bottom layer of tar. Sometimes with resinous woods the line of demarcation is not very well defined. In such cases the separation is difficult, without distilling. A centrifugal separator could be used to advantage. The crude product coming from the wood in the steam process consists of crude turpentine as an upper layer and of water as a lower layer. In all the processes the separation is effected as far as possible by gravity, the different products being drawn off at the respective levels. CRUDE ACETATES. The pyroligneous acid contains fatty acids, chiefly acetic, varying from 4 to 10 per cent, about 1 to 12 gallons of wood alcohol to the cord of wood used, some acetone, light oil, metacetone and other ketones, aldehydes and tarry THE DESTRUCTIVE DISTILLATION OF WOOD 285 products. To obtain the various products, different means are pursued according to the quality of products to be made. These are brown acetate of lime or lead, gray acetate of lime, acetate of soda, acetic acid and refined wood alcohol. To make brown acetate of lime, the acid is simply neutralized with lime and the insoluble tarry products produced skimmed off. The solution of acetate is distilled in an iron or copper still until the wood alcohol is collected, when the remaining liquor is evaporated to dryness and partially charred to destroy tarry matters. To make gray acetate of lime, the liquor is sent to an acid still, a copper still with or without special fractionating column. The alcohol distills first and may be collected separately until the temperature in the sill approaches 100° C. or the sp.gr. of the distillate is 1. The acid is then distilled and may be passed directly as a vapor through milk of lime, or condensed and caught separately, when it is known as distilled wood vinegar. This is neutralized with lime. As some of the acid will distill with the wood alcohol, both are usually condensed together and neutral- ized with lime. The liquor is then distilled in a fractionating still to recover the alcohol. The acetate liquor is evaporated to a paste in suitable iron pans, and then spread on top of the ovens to be thoroughly dried and partially charred. Crude hydro- chloric acid is often added before evaporation and the liquor drained from the deposit so formed. The evaporating pans, made of copper, are usually provided with a set of stirrers to prevent the acetate from sticking to the bottom. The tarry matter rising to the surface is removed through a sliding door. When the specific gravity (measured hot) reaches 1.116 the separation of acetate begins and gradually the mass forms a thick paste, which is removed and spread on fiat iron pans to be dried. Some finish the drying in rooms heated by the waste furnace or retort gases. The residue in the stills is " boiled tar," and is removed at intervals as it accumulates. Acetate of soda is made in a similar manner to acetate of lime. Sodium carbonate is added, in small portions at a time to avoid too much effervescing, to distilled wood vinegar until the acid is neutralized. The tarry substances appearing on the surface are removed and the brown fluid, after clarifying by standing, is drawn off into shallow iron pans, which are heated by the fire gases from the retorts or by steam. The liquid is evaporated to 1.23 sp.gr., then crystallized in sheet-iron boxes. The crystals are 286 ELEMENTS OF INDUSTRIAL CHEMISTRY drained from the mother liquor and then centrifuged. By cal- cining these crystals, redissolving and recrystallizing, a very pure salt is obtained. Sometimes the solution is filtered through bone black or boiled with 10 per cent of bone black and after recrystal- lizing and centrifuging an entirely pure salt is obtained. WOOD ALCOHOL. The crude wood alcohol is treated with lime and settled, the clear liquor being redistilled in column stills until of about 82 per cent by volume passes over. By again distilling, a product of 92 to 95 per cent can be easily ob- tained. However, to make alcohol that is miscible with water, it is advisable to dilute the alcohol until the specific gravity reaches 0.934 and allow the mixture to rest for a few days, when the greater portion of the hydrocarbons separate as an oily layer on the top and can be drawn off. The alcoholic fluid left is distilled over lime and makes strong alcohol that does not become turbid upon the addition of water. The oily fractions are mixed together and redistilled separately, when a further quantity of alcohol is obtained. Only the portion miscible with water is saved, the other portions being worked over. The first runnings of the distillate are more or less colored, but the middle fractions are colorless and yield good alcohol. After the middle portion distills the alcohol begins to contain oil and it becomes non-miscible. Subsequently, the distillate becomes turbid and finally a mixture of oil and water comes over, which separates into two layers. None of these processes serves to remove all the acetone. To do this several methods are used. One is to form a compound of wood alcohol and calcium chloride, which is stable at 100° C. By gently heating, the acetone is driven off, and then by adding water and raising the temperature to 100° C. the calcium chloride compound decomposes and the methyl alcohol distil.s. Another method is to add caustic potash and iodine until the yellow color disappears, then to distill. The watery alcohol is repeatedly rectified over lime, and finally over metallic sodium or phosphoric anhydride to remove the last traces of water. THE CRUDE TAR. The tar from hard woods is usually burned for fuel, but that which is to be utilized is washed with water or dilute milk of lime, in order to wash out the acid. It is then ready for further treatment. The tar from resinous woods is distilled with live steam in a copper tar still until the oils are removed. If these oils contain turpentine, as they would when the distillate is collected together, they are specially refined. When thick enough the tar is ready for barreling. THE DESTRUCTIVE DISTILLATION OF WOOD 287 TAR OILS. There is a small but increasing demand for tar oils as insecticide and disinfectants. To obtain tar oil from the tar, it is distilled in a wrought- or cast-iron vessel sometimes provided with a stirrer. The general shape of the still may be similar to a turpentine still, or the still may be a horizontal cylinder set in brickwork. The still is heated slowly and the distillate collected until the specific gravity of the tar oil reaches about 0.98, when the receiver is changed. Some of the oils present in the tar distill unchanged, while the heavier products are broken up to a greater or lesser degree, forming coke and gas. Follow- ing the light oils, a heavy oil comes over, having a specific gravity of upward of 1.01 and of a yellowish-green color. The distilla- tion is sometimes carried on until nothing but coke is left in the still, but it is usually better to stop with the production of pitch, which can be drawn out hot from the still. This is run out on iron plates to cool, care being taken to prevent ignition. The condensate is sometimes divided according to the temperature of distillation, the light oils being collected up to 240° C. and the heavy oils between 240 and 290° C. The heavy oil contains most of the creosote, which is extracted from the heavy oil by means of caustic lye of about 1.2 sp.gr. The hydrocarbons are boiled out and the creosote separated by neutralizing with sul- phuric acid. The treatment is repeated and the final creosote distilled, the product coming over between 200 and 220° C. being called commercial wood creosote. To further purify it, it is oxi- dized with a mixture of dichromate of potassium and sulphuric acid and again distilled. The crude oil in the distillate from the steam treatment of pine tar is often saved. It varies in color from light yellow to brown, exposure to the air causing the color to become much darker. A number of substances are present, including the oils coming from the distillation of the turpentine and from the destructive distillation of the rosin in the wood. The crude oil also contains considerable quantities of creosote and tar prod- ucts. To remove these, the oil is redistilled in a still of similar shape and construction to the tar still — only smaller. The oil comes over with only a slight coloration. To prevent this color, the crude oil is sometimes treated with chemicals such as caustic soda, lime, permanganate, sulphuric acid and the like before being distilled. These substances usually fail to remove either odor or color to any great extent. When the percentage of turpentine in the wood oil is large, the crude oil is washed 288 ELEMENTS OF INDUSTRIAL CHEMISTRY with oil or alkali in an agitator and often distilled in a column still similar to the still used in refining wood alcohol. TURPENTINE. The crude wood turpentine caught separately when wood is distilled by any method, is usually refined in order to make a marketable article. When the oil is very impure a still with a short column is desirable. When the oil is relatively pure and almost colorless like that obtained in the steam dis- tillation, a simple distillation is all that is needed. The oil should be tested as it comes from the still and when the specific gravity reaches 0.875 the receiver should be changed or the distillation ended. The distillate is often divided into three portions, the first fraction consisting of the light oils, corre- sponding to turpentine, the second fraction being a mixture of turpentine and light pine oils and the third fraction being very heavy pine oils. The middle fraction is redistilled and yields an additional amount of turpentine. A heavy oil called pine oil remains behind, which can be distilled at a higher tempera- ture. This oil should not be mixed with the turpentine, as the mixture does not dry readily. PINE OILS. The heavy oils accompanying wood turpentine are called pine oils. They are divided into two grades, water white and yellow. The darker grades are heavier and are of the most value. They are used in medicine and as solvents. Ter- pineol is one of the chief ingredients. ACETIC ACID. This acid is not usually prepared directly from wood vinegar, although it can be with considerable trouble. It is usually prepared by the decomposition of some acetates. Some of the acetates are decomposable by heat into acetic acid and oxides, for example lead acetate. The diacetates of sodium and potassium yield a very concentrated solution of acid when heated. Usually, it is best to start with acetate of lime or soda and to distill with concentrated hydrochloric acid in a copper still, care being taken to have an excess of the salt in the still. When brown acetate of lime is used, it is previously roasted at a low temperature. The acid formed is colored and contains about 50 per cent of anhydrous acid. With dilute hydrochloric acid in the still, the acetic acid is purer, but contains only 30 per cent anhydrous acid. Often the acid is distilled in Marx vessels and filtered in towers through freshly burned charcoal. To obtain stronger acid, the weak liquor is redistilled and the stronger parts of the distillate caught separately. Any HC1 that may be THE DESTRUCTIVE DISTILLATION OF WOOD 289 found in the distillate can be removed by rectifying over acetate of lime or soda. Sulphuric acid could be used to effect the dis- tillation, but the operation is not so smooth and the distillate is apt to contain sulphur dioxide. Glacial acetic acid can be prepared by distilling 12 parts by weight of pure anhydrous sodium acetate with 11 parts of con- centrated sulphuric acid. The first portion of the distillate is rectified over sulphuric acid and pyrolusite to remove traces of sulphurous acid. The last portion, which is frequently empy- reumatic, is collected by itself. The water in the 50 per cent acid can be removed by distilling with anhydrous calcium chloride and cooling the distillate, whereby one portion crystallizes. The liquid portion is drawn off and again distilled over calcium chloride. By distilling strong acid over fused and coarsely powdered potassium acetate and changing the receiver at 120° C the glacial acetic acid will pass over in the last portion. This is again rectified over potassium acetate and the distillate cooled to about 16° C. to crystallize the acid. Stoneware vessels are needed to carry on the distillation, as the acid strongly attacks metals. ACETONE. On a commercial scale, acetone is made by the dry distillation of gray acetate of lime at !290 to 400° C. in retorts which are connected with a cooling apparatus. When brown ace- tate is used it is previously roasted at 230° C. The first runnings are weak in acetone , but the percentage increases with the tem- perature. The distillate separates into two layers, the " heavy acetone oils " on top and the lighter oils dissolved in water on the bottom. The yield is about 20 per cent of the calcium acetate. The crude acetone is treated with lime and distilled in column stills in a similar manner to wood alcohol, a nearly pure product ■ being obtained. The nearly pure acetone can be purified by treatment with sodium bisulphite and then crystallizing the compound formed. CHAPTER XIV OILS, FATS AND WAXES CLASSIFICATION OF FATS. The term oil is used for sub- stances differing widely both in composition and properties, and in this chapter the fatty oils only will be considered. Fats and fatty oils consist essentially of compounds of the higher fatty acids in combination with glycerol, and are termed glycerides. Their composition was first placed on a scientific basis by Chevreul, who in the early part of the last century showed that when a fat such as tallow or lard was converted into soap by the action of sodium or potassium hydroxide, the fat was decomposed into glycerine and fatty acids, the latter combining with the alkali to form the soap, while the glycerine, remaining free, was separated in the lyes. The three most commonly occurring glycerides are stearin, palmitin (of which tallow chiefly consists) and olein (the principal constituent of olive oil). The conclusions of Che- vreul as to the composition of fats where subsequently confirmed by Berthelot, who succeeded in producing the glycerides syn- thetically by heating the fatty acids with glycerine under pressure in sealed tubes. Heating together, for example, stearic acid and glycerine, he obtained stearin, according to the equation: 3Ci8H3502H + C3H5(OH)3 = C 3 H5(Ci8H8502)3 + 3H20. From their physical appearance it is not possible to give a definite classification, for what would be considered a solid fat in a temperate climate might be a liquid in a warmer locality. Roughly, however, we may class certain ones as liquid fats or oils, and others as solid fats, or fats. " The most convenient classification of fats (fatty oils and solid fats) for practical purposes, appears to be given by arranging them according to the magnitude of the iodine value. This principle leads, without unduly forcing it, to a natural subdivision into liquid fats and solid fats, the former being differentiated from the latter by the considerably higher iodine value, Hence, an 290 OILS, FATS AND WAXES 291 arrangement based on the magnitude of the iodine value would include the older system of classification according to consist- ency. Inasmuch as the magnitude of the iodine value stands in close relationship to the absorption of oxygen, or, in other words, to the drying power, classification on the iodine value would also include the older subdivision into drying and non-drying oils." (Lewkowitsch.) Arranged in this manner are the following subdivisions : I. Liquid Fats and Fatty Oils. A. Vegetable oils B. Animal oils 1. Drying oils 1. Marine animal oils 2. Semi-drying oils (a) Fish oils 3. Non-drying oils (b) Liver oils (c) Blubber oils 2. Terrestrial animal oils II. Solid Fats A. Vegetable fats B. Animal fats 1. Drying fats 2. Non-drying fats Classification of Waxes. Our comprehension of the generic term " wax " is based in considerable measure on the physical characeristics of the oldest known wax; namely, com- mon beeswax. It has been suggested that the term wax is defined as applied to more or less unctuous, fusible, variably viscous to solid substances, having a characteristic " waxy " luster, which are insoluble in water but usually soluble in car- bon disulphide, benzol, etc., and which are extremely suscep- tible to changes in temperature and whose origin, composition, and color are variable. Thus under this definition are included the class of waxy bodies which consist of mono or dihydric alcohols united with the higher fatty acids to form esters (beeswax, carnauba wax, etc.), as well as glycerides of a "waxy" appearance, such, for example, as Japan wax; and the hydrocarbon waxes paraffine, ceresin, ozocerite and the like. Waxes may be grouped as follows; A. Liquid waxes B. Solid waxes 1. Vegetable waxes 2. Animal waxes 292 ELEMENTS OF INDUSTRIAL CHEMISTRY CONSTITUTION OF THE FATS. The fats as stated are com- binations of glycerol with fatty acids. Glycerol being a tri- hydric alcohol, will combine with one, two, or three acid radicles, thus forming mono-glycerides, di-glycerides, and tri-glycerides. The last class, however, is the most important, as it is this con- dition which is supposed to exist in the neutral fats. The fol- lowing graphic formulas will more clearly emphasize the three possible combinations: H I Monostearin. C 1 7H3 5 COO— C— H I HO— C— H HO— C— H I H H I Distearin C17H35COO— C— H I C17H35COO— C— H I HO— C— H I H H I Tristearin. C17H35COO— C— H I C17H35COO— C— H I C17H35COO— C— H I H It will be seen that not only is it possible to have compounds in which one acid enters into the combination, but also others, known as mixed glycerides, in which two or even three different acid radicles may be joined to one glycerol group. This is thought by some to account for the fact that practically all of the common oils are mixtures, rather than smple esters. Our OILS, FATS AND WAXES 293 present knowledge, however, does not warrant any definite conclusion in this matter. The fatty acids are all lighter in weight than water. Those having less than ten carbon atoms may be distilled, and are known as the volatile fatty acids. Those containing more than ten carbons cannot be distilled without decomposition and are known as non-volatile fatty acids. The oils containing the saturated acids do not undergo any marked change when exposed to the air. On the other hand, those which contain the unsaturated acids become gummy, and in certain instances when exposed in thin layers form dry, hard films. This change is called drying, and is most marked in the case of those oils containing giycerides of linoleic, linolenic, clupanodonic and ricinoleic acids. VEGETABLE OILS. The usual method of obtaining the oils is by crushing that part of the plant richest in oil, and subse- quently pre sing the ground pulp thus obtained. Extraction with benzine or other solvent is also employed. The crushing may be secured by means of the edge-runner, or by means of heavy steel rollers arranged in vertical series. The crushed material is then placed in canvas bags, and subjected to hydraulic pressure The first pressing is usually done in the cold, as a lighter color and better quality is thus obtained. During the second pressing the pulp is heated, thereby producing a larger yield, but of an inferior quality. By further heating a final oil is obtained known commercially as " foots." The extraction process con- sists in treating the ground pulp, contained in closed vessels, with benzine, naphtha or other solvents. The extract is sub- jected to distillation in order to recover the solvents, leaving the fats in the still. Although this method gives a larger yield than is possible by pressing, it is not generally employed on account of the risk from fire, the cost of installation, and im- possibility of directly using the press cake as a cattle food. VEGETABLE DRYING OILS. Drying oils are characterized by their power to absorb oxygen from the air, thus forming an elastic film. The amount of this absorption in the main is in proportion to the iodine value; so that we may roughly judge of the drying quality of an oil from its iodine number. Perilla Oil. This oil occurs to the extent of 35.8 per cent in the nuts of the Perilla ocymordes, a plant indigenous to East India, Manchuria, and Japan. It has the highest iodine value of any known oil, and in odor and taste resembles linseed oil. 294 ELEMENTS OF INDUSTRIAL CHEMISTRY TABLE OF CONSTANTS FOR DRYING OILS Name of Oil. Perilla Linseed Tung Hemp Poppy Sunflower. . . Tobacco seed. Oil Con- tent of Seed, Per Cent. 35.8 38-40 40-41 30-35 41-50 21-22 38-40 Specific Gravity. 0.9306 9315-45 0.9360-432 0.9255-80 0.9240-70 0.9240-58 0.9232 20° C. 15° C. 15° C. 15° C. 15° C. 15° C. 15° C. Saponifi- cation Value. 189.6 192-195 193 192.5 195 193.5 170 Iodine Value. 206.1 171-201 150-165 148 133-143 119-135 118.6 Refractive Index. 1.4835 1 . 5030 1.4780 1 . 4586 1.4611 22° C. 19° C. 15.5° C. 60° C. 60° C. Its drying quality, however, is, it is claimed, inferior to linseed oil, due to its peculiar property of forming drops when spread oh a hard surface. Recent experiments, on the other hand, do not bear out this statement. Linseed Oil. This ia obtained from the seeds of the flax plant, grown extensively in Russia, India, Argentina, Canada, and the United States. On cold pressing, a light yellow oil is obtained, used to a limited extent as an edible oil. By far the greatest quantity, however, is used in the manufacture of paint and varnish. The chemical composition of Unseed oil is not well known, although indications point to about 10 per cent of glycerides of solid fatty acids, equal parts palmitic and myristic acids. The liquid glycerides consist of 5 per cent of oleic acid, 15 per cent of linoleic acid, 15 per cent of linolenic acid, and 65 per cent of isolinolenic acid. Linseed oil is now converted by hydrogenation into a solid fat, which serves as a substitute for tallow in soap making. Tung Oil. This oil is often spoken of as " Chinese wood oil." It is obtained from the seeds of Aleurites cordata, a tree indigenous to China and Japan. The oil varies to some extent according to its source. The seeds are usually roasted, broken into a powder and pressed. The cold pressed oil is pale yellow, and is known in the trade as " white tung oil." That resulting from hot pressing is dark in color, and termed " black tung oil." The raw oil has a peculiar odor suggestive of ham. Its chemical constitution differs from linseed in that it consists almost wholly of glycerides of oleic and elaeomargaric acids. Tung oil is used principally in the manufacture of varnishes and linoleum. When incorporated with ordinary rosin and suitably thinned, a varnish is obtained which is not affected OILS, FATS AND WAXES 295 readily by water, while varnish made with rosin and linseed oil alone is quickly turned white by contact with water. In con- sequence of this behavior of tung oil, it has become very popular with the varnish maker as a means of producing cheap but good varnish. When heated to 230° C. and over, the oil coagulates to a transparent solid which is elastic under compression, and this product has been recommended as a rubber substitute called factis. Hemp Seed Oil. The source of this oil is the hemp plant, Cannabis sativa. The color of the fresh oil is light green, becom- ing brownish-yellow on standing. The solid glycerides of hemp oil are claimed to be those of stearic and palmitic acids. The liquid glycerides contain linoleic, oleic, linolenic, and isolin- olenic acids. It is used as a paint oil, for making soft soaps, and low grades are employed for certain varnishes. Poppy Oil. To obtain this oil the seeds are pressed cold, thus producing a product almost colorless, or very pale golden yellow, known in the trade as " white poppy seed oil." That expressed at a higher temperature is known as " red poppy seed oil." It is cultivated largely in Asia Minor, Persia, India, Egypt, and Russia. It is used largely as a salad oil, and in the manufac- ture of artists' colors. Sunflower Oil. This oil is obtained from the seeds of the Helianthus annuus. It is of a mild taste, pleasant odor, and a pale yellow color. It is raised extensively in Russia, Hungary, India and China. It is employed in soap making, and for the manufacture of varnish. This oil does not dry as readily as those previously mentioned. Tobacco Seed Oil. The oil obtained from the seed of the tobacco plant is of a pale greenish-yellow color, and dries very readily. On account of its high price it has never found any commercial application. Vegetable Semi-drying Oils. These oils form a connect- ing link between the drying oils and the non-drying oils, although it is difficult to say to which class they belong. Chemically they differ from the drying oils by the presence at the most only of small amounts of linolenic acids; and from the non-drying oils by the linoleic acid they contain. Soja Bean Oil. This oil is also known as soy bean oil. It is obtained from the seeds of several varieties of the Soja hispida, a plant growing in China, Manchuria and Japan. The whole fruit consists of a hairy pod, containing small round, yellow seeds, 296 ELEMENTS OF INDUSTRIAL CHEMISTRY TABLE OF CONSTANTS FOR SEMI-DRYING OILS Name of Oil. Soja bean Pumpkin seed. Corn Cotton seed. . . Sesame Croton Rape" Castor Oil Con- tent of Seed, Per Cent. 18 35-37 6-10 24-26 50-57 53-56 33-43 46-53 Specific Gravity. 0.9242-70 0.9237 0.9213-55 0.9220 . 9230-37 . 9500 0.9132-68 0.9600-79 15° C. 15° C. 15.5° C. 15° C. 15° C. 15° C. 15.5° C. 15.5° C. Saponifi- cation Value. 192.7 188.4 188-193 193-195 189-193 210-225 170-179 183-186 Iodine Value. 121.7 123-130 113-125 106-110 103-108 102-104 94-102 83-86 Refractive Index. 1.4762 1.4723-38 1.4750-70 1 . 4743-52 1.4748-62 1.4768 1.4720-57 1.4799 15.5° C. 25° C. 15.5° C. 15° C. 15° C. 27° C. 15° C. 15° C. slightly smaller than the ordinary pea. Green and black varieties also exist. The seed or bean contains 16-19 oer cent of oil and the commercial yield is about 13 oer cent. The raw oil is deep brown in color and is not much improved by alkali treatment except when bleached. The odor and flavor are slight and not unpleasant, but the keeping qualities of the oil are not particularly good, and on storage a nauseous taste is likely to develop after a time. The oil is employed for edible purposes, although in a limited way. It is used in soap making, and has been tried as a paint oil, but its " greasy " properties have not led to extensive use in this field. Soja oil hydrogenates readily, forming a hard fat. Pumpkin Seed Oil. In South Russia the seeds of the Cucur- bito pepo are roasted, and the oil expressed in the hot condition. This produces a viscous product of a deep red color. The cold pressed oil has a greenish color and a slight red fluorescence. The cold pressed oil is used for edible purposes, while the inferior grades serve as burning oils. Corn Oil. This oil is obtained from the germ of the maize plane Zea mays, during the manufacture of corn starch. The freshly prepared oil has a pale yellow color, and may be readily identified by its taste, which is similar to that of corn meal. The keeping qualities of the oil are very good when refined, but the crude oil is rapidly hydrolized if meal be present. By careful refining and deodorizing with superheated steam, an edible product is obtained which has a very pleasant taste and whose keeping qualities are good. This grade of oil is used in cake and biscuit making and for oiling bakers' pans, also in mar- garine and as a salad oil. Hydrogenated corn oil serves as a OILS, FATS AND WAXES 297 satisfactory stiffening ingredient in lard compound. Corn oil is used quite extensively in soap making and to a more limited degree in the manufacture of paint. The output of corn oil is, however, almost insignificant in comparison to that of cotton seed oil. Cotton Seed Oil. This oil is obtained from the seed of the cotton plant, extensively cultivated in the United States, Egypt, East India, and other countries. The oil as it comes from the hydraulic press varies in color from yellowish brown to a dark ruby or blackish red, depending on the nature and condition of the seed from which the oil has been expressed. It contains mucilage, fine meal or " mealy matter," coloring and tarry material. Some of these impurities are due to the effect of mois- ture and heat in pressing the oil from the cooked seed. Crude oils containing under one per cent of free fatty acid and derived from selected seed are used in the manufacture of butter oils. Great care has to be taken in the preparation of butter oils to preclude the development of any unpleasant taste or odor. When about 1 or 2 per cent of fatty acid is present hi the crude oil refining is earned out to produce what is known as prime yellow oil. Above 2 per cent of fatty acids, there is more diffi- culty in removing the color, and the oil is not as suitable for edible purposes. Crude oil may contain as high as 7 or 8 per cent of free fatty acids in case the seed has become damaged by heating, etc. The losses occurring in the refining of the crude oil varies with the proportion of free fatty acids and usually runs from 7 to 10 per cent. Improved methods in refining are tending to reduce this loss. Cotton seed oil is used in large quantities for edible purposes, but ow 7 ing to popular prejudice it seldom appears under its true name. We may find it on the open market as " table oil," " salad oil," " sweet nut oil," as well as under a score of other designations. Large quantities of the cotton seed stearine are employed in the manufacture of " oleomargarine," butter com- pounds, butter substitutes, lard compounds, and lard substitutes. Cotton seed oil, being cheap, is often used as an adulterant for the more expensive oils, such as olive, peanut and other edible oils. One of its most imooitant uses is in the manufacture of toilet and laundry soaps. Sesame Oil. This oil is obtained from Sesamum orientate, extensively grown in India, China, Japan, the Levant and West Africa. The cold pressed oil is of a light yellow color, with a 298 ELEMENTS OF INDUSTRIAL CHEMISTRY pleasant taste, so that it is used to some extent for edible purposes. In some countries the legal requirement is made that sesame oil form a constituent of margarine in order to facilitate the detection of margarine in butter. The hot pressed oil is used largely in soap making. Croton Oil. Croton oil is obtained from the seeds of Croton tiglum, a tree grown on the Malabou Coast, in Southern Asia, and in China. The oil varies in color from yellow, orange or brown according to age. It has a nauseating odor, a burning taste, and a very powerful purgative action. Its chief use is in pharmaceutical preparations. Rape Oil. There are several varieties of this oil, depending upon the place of cultivation. The oil is obtained from the seeds of Brassica campestris. In the trade this oil is called colza oil. The crude oil is dark brown and may contain a considerable proportion of free fatty acids. The refined oil is pale yellow and is very viscous, depositing more or less stearine on standing. The taste is unpleasant and the odor characteristic. Refined cold drawn oil is sometimes used for edible purposes, while the inferior qualities find an outlet as lubricants and illuminants. Rape oil as well as cotton and corn oil are converted into rubber substitutes or factis by treatment with sulphur chloride or by heating with sulphur. Rape oil is also " blown " with air to produce thick- ened products. Castor Oil. This oil is obtained from the seeds of Ricinus communis, a plant grown extensively in East India, Java, the Mediterranean countries, and the United States. The cold pressed oil is used for medicinal purposes. The lower grades are used very extensively in manufacturing operations, such as leather dressings, and in the sulphonated condition is known as " soluble oil " " Turkey red oil " or " monopol oil." Castor oil is a colorless or pale greenish oil with a mild taste. It has a high viscosity and finds some application in lubri- cants, although by no means devoid of gumming properties. Sul- phur unites readily when heated with it, forming rubber-like compounds. The hydrogenated product is very hard and has found a use in the manufacture of insulating materials. A peculiar property of castor oil is its miscibility with alcohol. Unlike most other oils it does not dissolve readily in petroleum ether. By heating to a rather high temperature the oil becomes poly- merized and is then miscible with petroleum ether and mineral oils, OILS, FATS AND WAXES 299 Vegetable Non-drying Oils. The oils in this class have a lower iodine number than those of the two preceding classes. They do not become gummy when exposed to the air at ordinary temperature, although they all thicken on heating. Name of Oil. Oil Con- tent of Seed, Per Cent. Specific Gravity. Saponifi- cation Value. Iodine Value. Refractive Index. Peach kernel . . Almond Peanut Olive Olive kernel. . . 32-35 45-55 43-45 40-60 12-15 0.918 0.9215 0.9175 0.9195 0.9170- 0.9209 0.916-18 0.9184- 0.9191 15° C 15° C 15° C 15° C 15° C 191.5 199.3 191.3 185-196 183 93.3- 100.3 100.7 94.7 79-88 87.4 1.4713 1.4731 1.4766 1.4698- 1.4716 1 . 4682 15° C 15.5° C 15.5° C 15° C 25° C Peach Kernel Oil. This oil is obtained from the kernel of the peach, is of a pale yellow color, and greatly resembles almond oil. Its chief use is as an adulterant for almond oil. Almond Oil. Almond oil is expressed from bitter almonds, which yield more oil than sweet almonds, although both oils are practically identical. The source of this oil is Morocco, Canary Islands, Portugal, Spain, France, Italy, Sicily, Syria, and Persia. Its chief use is in pharmaceutical preparations. Peanut Oil. This product is also known as earthnut oil and arachis oil. It is obtained from the seeds of Arachis hypogcea, commonly known as peanut. It is largely cultivated on the west coast of Africa, India, and the United States. The nuts are shelled and the inner red skin separated as completely as possible from the true kernel. The kernels are then pressed. The oil has a golden yellow color and the edible varieties are usually bleached to a very pale color. The cold-pressed oil is nearly colorless, has a pleasant flavor and is largely used as a salad oil. The inferior qualities are used in soap making. Olive Oil. The oil is prepared from the fruit of the olive tree, both by expression and extraction. The commercial product varies from colorless to golden yellow and dark green, according to the variety of tree, degree of ripeness, manner of gathering, 300 ELEMENTS OF INDUSTEIAL CHEMISTRY and method of expression. " Virgin oil," considered the best quality for edible purposes, is obtained from the hand-picked fruit, by crushing in such a manner as not to break the kernel. The pulp is then treated with water and pressed again. By this process salad oils are obtained. The pulp is then removed from the press, treated with hot water and again subjected to hydraulic pressure, the oil obtained being employed for lubricating, soap making, and for other technical purposes. The final expression comes into the market as " olive oil foots," extensively employed in the manufacture of " castile " soap. The best quality of the oil is greenish yellow. The consistency is that of a limpid oil at ordinary temperatures and beginning to deposit " stearin " below 10° C. The oil is valued more par- ticularly on its flavor. The finest edible oil has practically no smell and very little taste, but with inferior grades there is a distinct odor and the taste becomes sharp and uupleasant, due in part to increasing proportions of free fatty acids. The best edible oil contains only 0.3-0.5 per cent of free fatty acids, and anything much exceeding this precludes its use as a salad oil. The acidity is sometimes removed by treatment with alkali, and oils treated in this way do not show the absorption bands of chlorophyll which are often clearly given by the fresh oil. Olive Kernel Oil. This oil is obtained by pressing or extracting the seeds from olive stones. The cold-pressed oil is golden yellow in color, while the hot-pressed oil has a greenish cast. The extracted oil is dark green in color, probably due to the presence of chlorophyll. This oil in a way is the by-product in the manu- facture of olive oil, and resembles it very closely in all of its properties. ANIMAL OILS. These oils are obtained by heating the fatty matter with live or dry steam in open kettles or closed digesters; the old method of heating over the open fire is now used but infre- quently. One of the most modern processes consists in heating the stock with water, at a pressure sufficiently high to cause a complete separation, but not high enough to decompose the stock. When this " rendering " is complete the contents of the digester is filtered to remove solid matter, and the liquid portion allowed to stand so that the oil may rise to the top. The liquid portion remaining after the oil has been removed may be used again, or may be concentrated for use in glue stock. The solid matter is usually dried and sold for use in fertilizers. In some forms of rendering tanks the oil is allowed to rise to the top, where it OILS, FATS AND WAXES 301 is removed by tap valves along the side. The oil obtained by the above methods is usually sufficiently pure for commercial pur- poses. If it is to be used for edible purposes, it is customary to purify it further by bleaching. This is accomplished by passing the oil or fat through bone-black or fuller's earth. Animal oils may be divided into two classes: 1. Marine animal oils. 2. Terrestrial animal oils. MARINE ANIMAL OILS. The marine animal oils are char- acterized by their high iodine values, which in a way resemble the vegetable drying oils. As with vegetable oils, we have a gradual lowering of the iodine value through drying, semi-dry- ing, and non-drying oils, until we approach the constitution of the terrestrial animal oils. The members of this class of oils are liquids at the ordinary temperature, and will be considered under the three following groups: Fish oils Liver oils Blubber oils FISH OILS. The fish oils are obtained from various parts of the body of such fish as menhaden, herring, sardine, salmon, etc. The fish, or oily portion, is placed in rendering tanks, boiled and the oil drawn off from the top. The soluble portion is used for making fish glue, isinglass, and the solid portions sold as a fertil- izer under the name of fish scrap. TABLE OF CONSTANTS FOR SOME COMMON FISH OILS Name of Oil. Specific Gravity. Saponi- fication Value. Iodine Value. Refractive Index. Menhaden Sardine Salmon 0.927-0.933 0.933 0.9258 15.5° C 15° C 15.5° C 190.6 182 '8 139-180 161-193 161.4 1.480 1.479 15° C 15° C Menhaden Oil. This oil is prepared from the body of the fish, which in appearance resembles herring, although it is somewhat larger. The time of fishing for menhaden is determined, of course, by the habits of the fish. Since they appear in northern waters in April and disappear in November, the fishing season is limited to those months. As one goes farther south, the season is lengthened ; in the Carolinas the boats are not put out of commis- 302 ELEMENTS OF INDUSTRIAL CHEMISTRY sion until the latter part of December, though fishing does not begin much earlier there than in the northern regions. In the southern region, the spring and fall fishing furnishes most of the raw material, there being a dull season in midsummer, when catches are rare and unimportant. In Florida waters the fish are present throughout the winter. Sardine Oil. This oil is obtained in the preparation of canned sardines. It is also made on a large scale in Japan by chopping the fish and subjecting them to boiling and pressing. Salmon Oil. This oil is obtained on a large scale as a by- product in the canning industry of British Columbia. It is of a pale golden yellow color, with very little odor, and not unpleas- ant taste. LIVER OILS. As the name implies, these oils are obtained from the liver of various species of fish. They form a natural group which is characterized by the large amount of cholesterol, and biliary substances present in them. The iodine values bring them between the fish and blubber oils. CONSTANTS FOR LIVER OILS Name of Oil. Specific Gravity. Saponifi- cation Value. Iodine Value. Refractive Index. Cod liver Haddock liver. . 0.9210-70 0.9298 0.9163 15° C 15° C 15° C 171-189 188.8 161 167 154.2 114.6 1.4800-52 15° C Shark liver .... Cod Liver Oil. There are many grades of cod liver oil on the market, obtained in various ways from the liver of the codfish. The purest form of oil for medicinal purposes is that prepared from fish which are brought ashore alive. The fivers are heated in jacketed kettles, the resulting oil being known as " steamed liver oil." When it is impossible to bring in the live fish, they are opened and the livers collected. Provided no decomposition has taken place the oil obtained from this stock is known as " pale cod liver oil " and is used to some extent for pharmaceutical purposes. As often happens these livers are landed in a more or less putrid condition, so that the oil from them becomes unfit for medicinal use, and is known as " light brown oil." Should the product become very putrid the resulting oil is known as OILS, FATS AND WAXES 303 " brown oil." The oil not suitable for medicinal purposes is used in the currying of leather under the name of " cod oil." What is known as dark tank cod oil comes from Newfound- land and has a specific gravity of .9296; an iodine number of 129; fatty acid content 14 per cent and saponification number 190. Dark tank cod oil is made from cod fivers and is used for tanning. Cod liver oil contains quite an amount of stearine, which, to a great extent, settles out on standing. Oils which have been freed from stearine are known as " raked " oils. Shark Liver Oil. This oil is used to some extent as an adul- terant of cod liver oil; it is obtained in a manner very similar to that employed for cod oil. It is also used in the leather industry. The oil appears on the market as " yellow strained," " red," " vellow," " yellow red," " Japanese," " crude," and "refined." Haddock Liver Oil. The oil from haddock liver closely resembles cod liver oil, to which it is added to quite an extent as an adulterant. BLUBBER OILS. Under this heading will be included those oils obtained irom the blubber of various fish. They differ from each other quite widely in their chemical composition. CONSTANTS OF SOME BLUBBER OILS Name of Oil. Specific Gravity. Saponification Value. Iodine Value. Seal Whale 0.9155-63 0.9180- 0.9300 0.9180 0.9258 15° C 15.5° C 15° C 15° C 189-196 188 197.3 195 127-145 115-155 Dolphin Porpoise 99.5 Seal Oil. This oil is obtained from the blubber of the seal. It varies in quality, depending upon the method of extraction and the length of time the oil has been left in contact with the animal tissue. The following brands appear on the market; " water white," " straw seal," " yellow seal," and " brown seal." The last named oil is the result of long contact with animal matter and extraction at high temperatures. A white steam refined oil is produced only during the month of May in Newfoundland. It resembles whale oil but is not 304 ELEMENTS OF INDUSTRIAL CHEMISTRY as " fishy." Its principal use is as a soap oil. Analytically seal oil resembles whale oil. Whale Oil. Formerly the whale blubber was worked up on board the whaler, but now it is generally brought into the " trying " station. The blubber is stripped from the flesh as completely as possible immediately when it arrives at the works. It is cut into strips, delivered to the melting pan, and boiled with steam. The best quality of the oil is of a very pale yellow color, and is known in the trade as " whale oil, No. 0." The fishy odor is relatively very slight. On further heating, the next N quality , " whale oil No. 1," is obtained, which is a little darker in color, and has more of a fishy odor than No. 0. Bleached No. 1 oil is sometimes sold as No. 0. The residue in the pan, together with the flesh of the whale, is heated in a digester under pressure of about 50 lbs. to the square inch. In this way " whale oil No. 2 " is obtained, which is of a brown color and strong fishy odor. When the bones are worked up, an oil is obtained known as " whale oil No. 3." This oil is darker than No. 2 and has a very strong odor. From the flesh which has undergone putrefaction " whale oil No. 4 " is obtained. This is still darker in color and has a very objectionable odor. Nos. 2, 3, and 4 are graded by color. No. 1 is pale yellow. No. 2 is orange. No. 3 oil in the crude state may be likened to coffee containing cream. No. 4 oil is practically a black oil. About 60 per cent of the total oil from whale is the No. 1 grade. Thirty per cent is the No. 2 grade and the remainder is Nos. 3 and 4. No. does not appear on the market in material quantities. In this country No. 1 whale oil is frequently sold with an acid guaranty of not over 2 per cent. The No. 2 oil should not contain more than about 5 per cent of free fatty acid. No. 3 will run up to 15 per cent or so of fatty acid. The specific gravity of fish and whale oils ranges from .918 to .930. The iodine number of crude whale oil is very variable and ranges between 115 and 155 for all classes of these oils. In the pressing of whale oil to secure products of the proper cold test, a quantity of so-called stearine is obtained which is used mainly in the preparation of whale oil soap and for making railway coach lubricants. No. 1 filtered whale oil has a flash point, 570° F. and burning point 640° F. The viscosity at 100° F. is 166 seconds in the OILS, FATS AND WAXES 305 Saybolt instrument. No. 3 filtered whale oil has a flash point of about 380° F. and burning point of 424° F. The maximum production of whale oil is about 60,000 bar- rels annually, this being obtained mostly in Canada, especially along the Canadian Pacific coast. Only a small proportion comes from the American Pacific coast. A very small and uncertain supply is derived from the Eastern coast, but the whaling industry which formerly made New Bedford an im- portant port no longer exists and the industry is at its height now along the Canadian Pacific shores. A small amount of sea elephant oil is brought into this country, but is usually sold as whale oil. The uses of whale oil are confined largely to the following: For hydrogenation purposes to produce edible products and fats suitable* for soap making; for tempering. It is not used in tanning to any great extent in this country, although it finds favor for this purpose in Germany. The water white and pale brands of whale oil are used for burning and for soap making, the brown quality being used for leather dressings. Dolphin Oil. The oil obtained from the blubber of the black fish, in its chemical composition is intermediate between whale oil, a glyceride, and sperm oil, a wax. There are two varieties of this oil, body oil and jaw oil. Both are of a pale yellow color, and contain large amounts of glycerides of volatile fatty acids. It is used for lubricating fine machinery, such as watches and other delicate instruments. On standing sperma- ceti deposits. Porpoise Oil. This oil is obtained by boiling the entire tissue of the brown porpoise. It is of a pale yellow color, and consists of the glycerides of valeric, palmitic, stearic, and oleic acids. There are two varieties of the oil, body oil and jaw oil. It is used as a lubricant for delicate machines. Terrestrial Animal Oils. The oils of this class have a low iodine number, and therefore belong to the non-drying oils. Sheep's Foot Oil. This oil is obtained from the feet of sheep in very much the same manner as described for neat's foot oil, it being similar to neat's foot oil, and is usually sold as such. Horse's Foot Oil. As a rule this oil is never placed on the market under its true name, but is usually mixed with sheep's foot or neat's foot oil. What is sold as horse oil is the liquid portion of horse fat. 306 ELEMENTS OF INDUSTRIAL CHEMISTRY CONSTANTS FOR TERRESTRIAL ANIMAL OILS Name of Oil. Sheep's foot, Horse's foot. Neat's foot . Egg Lard oil ... . Tallow oil . . Specific C rravity. 0.9175 15° C 0.913-27 15° C 0.914-16 15° C 0.9144 15° C 0.916 15° C 0.794 100° C Saponification Value. 194.7 195.9 194 3 184.4-190 193 Iodine Value 74.2 73.8-90 69.3-70.4 68.5-81.6 73 55.8-56.7 Refractive Index. 1.4713 25° C Neat's Foot Oil. This oil is obtained by boiling the feet of cattle with water. It is of a pale yellow color and free from odor. The commercial product usually contains small amounts of sheep's foot and horses' foot oils. On account of the high price of neat's foot oil, it is often adulterated with vegetable, fish, or even mineral oils. The most common adulterants are rape oil, cotton seed oil, corn oil, menhaden or other fish oils, and mineral oil. True neat's foot oil is an excellent lubricating oil, but its chief application is in leather manufactuie. Egg Oil. This oil may be obtained by pressure or extraction from the hard boiled yolk of hens' eggs. The pressed oil has a yellow color, while the extracted oil is of an orange shade. The nature of the solvent largely influences the properties of the oil obtained; those most commonly used being ether and petro- leum ether. In the form of egg-yolk it has very valuable prop- erties in certain tanning operations. Lard Oil. This oil is obtained by subjecting lard to hydraulic pressure. It consists in the main of olein with a small pro- portion of the glycerides of solid fatty acids, chiefly palmitic acid. The quality of the oil varies greatly according to the pressure and temperature maintained; hence, the constants will vary within a considerable range. Its principal use is as a lubricant and in cutting oils. Tallow Oil. This oil is the fluid portion which is separated on subjecting tallow to expression. The processes of manu- facture and the properties of this oil are similar to lard oil. It also resembles neat's foot oil, but contains a larger proportion of saturated glycerides and is regarded as less valuable as a lubricant. Vegetable Fats. To this class of fats belong those which remain solid at the ordinary temperature. They differ, however, OILS, FATS AND WAXES 307 very greatly in consistency, ranging from soft to very hard. This variation in hardness is dependent upon the amount of glycerides of oleic and linoleic acids present; the smaller the amount of these glycerides the harder the fat. CONSTANTS FOR VEGETABLE FATS Name of Fat. Cotton seed stearine. Palm oil Vegetable tallow Cocoa butter. . . . Palm kernel oil. Gocoanut oil. . . Japan wax Shea butter. Specific Gravity. 0.9188- 0.9230 0.921- 0.9245 0.918 0.9500- 0.976 0.9520 0.9115 . 9700- 0.9800 15° C 15° C 15° C 15° C 15° C 40° C, 15° C Saponifica- tion Value. 195 192-202 200.3 193.5 242-250 246-260 217-237.5 180-190 Iodine Value. 90-103 51.5 28-37 32-41 13-14 8-9.5 4.9-9.5 57-63 Refractive Index. 1.4510 1.4496 1.4431 1.4410 60° C 60° C 60° C 60° C Cotton Seed Stearine. This product is manufactured on a very large scale by cooling cotton seed oil, and collecting the resulting solid which separates out. It is of a light golden color, of about the consistency of butter, for which it is used as an adulterant and it is also used in making margarine. It has also been employed as a lard substitute. Palm Oil. Until recently, the only source of this oil was from the coast of Africa, but at present considerable quantities come from the Philippines. The oil is obtained from the fleshy part of the fruit of the palm tree. The process of making this oil is very crude. Either the fruit is stored in holes in the ground, when by fermentation the oil separates and rises to the top; or the oil is pressed out by hand. The kernels are not destroyed, and from them palm nut oil is obtained. The fresh oil has a deep orange yellov T tint not destroyed by saponification, a sweet- ish taste and an odor of orris root or violet, which is also imparted to soap made from it. The methods by which the natives obtain the oil are crude and depend upon a fermentation or putrefaction. Large quantities are said to be wasted because of this fact. The oil contains impurities in the form of fermentable fiber and al- buminous matter, and consequently develops free fatty acid 308 ELEMENTS OF INDUSTRIAL CHEMISTRY rapidly. Samples tested for free acid have been found to have hydrolized completely and it is seldom one obtains an oil with low acid content. Because of this high percentage of free fatty acid, the glycerine yield is small, though the neutral oil should produce approximately 12 per cent of glycerine. Since soap made from palm oil is colored orange, bleaching before saponification is usually required. Vegetable Tallow. From the fruit of the Chinese tallow tree is obtained a hard fat. The fruit is steamed in perforated vessels, in which the fat melts and is ran off. The remaining seeds are then pressed and " Stillingia oil " obtained. Another process is also employed in which the whole fruit is crushed and pressed, thus yielding a mixture of vegetable tallow and Stillingia oil. Cocoa Butter. The cocoa beans are roasted, ground, treated with sodium carbonate and hot pressed. When freshly prepared cocoa butter has a yellowish color, but it turns white on standing. It has a pleasant odor and agreeable taste, and is less likely than almost any other fat to go rancid. It is used in confec- tionery, medicine, toilet creams and soaps. Palm Kernel Oil. This oil, as indicated above, is obtained from the kernels of the palm tree fruit. After the fleshy part of the fruit is removed the kernels are collected, screened, ground to a pulp and subjected to hydraulic pressure. It is a white oil, and when fresh has a pleasant odor and nutty taste. It is used very largely for soap making, and in the pure condition it is employed for edible purposes. " Stearin " from palm kernel oil is produced commercially of a somewhat higher melting point than that from cocoanut oil, and the " olein " may have a lower melting point than that of cocoanut " olein.'* There has been a prevailing belief that the keeping properties of palm kernel products were not as good as those of cocoanut oil, but owing to improved methods of refin- ing, this difference no longer exists. Cocoanut Oil. The source of this oil is the fruit of the Cocos nucifera (the ordinary cocoanut tree). The husk of the nut is removed by hand. The nut is split in two and is dried in the sun, which requires two or three days. The shell comes off soon after the drying has commenced. The dried meat is termed copra. Large quantities of copra are prepared by drying in kilns, but the color is usually darker when so treated. The copra generally is shipped and pressed at a place near the point of consump- OILS, FATS AND WAXES 309 tion to avoid loss of oil by leakage in transit and to save the expense of containers. The oil is a solid, white fat at ordinary temperature, having a bland taste and the characteristic cocoa- nut odor. It is rarely adulterated and is very readily saponified. In recent years the price of this oil has increased materially because cocoanut oil is now being used extensively for edible purposes, especially in the making of oleomargarine and bakers' fats. Present indications are that shortly very little high grade oil will be employed for soap manufacture, since the demand for it in oleomargarine manufacture is steadily increasing and since new methods of refining the oil for this purpose are constantly being devised. The oil is found in the market under three different grades: (1) Cochin cocoanut oil, the choicest oil coming from Cochin (Malabar).* This product, being more carefully cultivated and refined than the other grades, is whiter, cleaner and contains a smaller percentage of free acid than the other grades. (2) Ceylon cocoanut oil, coming chiefly from Ceylon, is usually of a yellow- ish tint and more acrid in odor than Cochin oil. (3) Con- tinental cocoanut oil (copra). This product is generally superior to the Ceylon oil and may be used as a very satisfactory sub- stitute for Cochin oil, in soap making for example, provided it is low in free acid and of good color. Cocoanut oil has a saponification value of 246-260, an iodine value of 8-9.5 and the melting point is approximately 22° C. By pressing, cocoanut oil olein and stearin is prepared and the refined stearins are largely used as cocoa-butter substitutes in the manufacture of chocolate and biscuits, also for pharma- ceutical purposes. The refined olein finds use as a baking fat in biscuits and pastry. The whole oil is customarily used in making margarine. Shea Butter (Shea nut oil). This is a stiff, plastic fat some- what granular and occasionally of a " stringy " nature. It contains from 5 to 10 per cent of unsaponifiable matter. The refined fat, which can be rendered practically tasteless and odorless, finds an increasing use abroad for edible products. ANIMAL FATS. Under this head are included those solid fats which are derived from animal tissues. They vary in degree of hardness according to the amount of the glycerides of un- saturated fatty acids present, those with the higher amount being the softer. Although only non-drying fats will be considered it may be 310 ELEMENTS OF INDUSTRIAL CHEMISTRY well to state that certain animal fats have quite pronounced drying qualities. CONSTANTS FOR ANIMAL FATS Name of Fat. Specific Gravity. Saponifica- tion Value. Iodine Value. Refractive Index. Horse Lard. . . 0.9189 0.934-0.938 0.943-0.952 0.937 0.926-0.946 15° C 15° C 15° C 15° C 15° C 200.5 193.5 190.9 193.2-200 192-195.2 81-2 66-7 46-55 38-46 35-46 1.4510 1.4510 Beef tallow .... Mutton tallow. Butter 60° C 60° C Tallow is the name given to the fat extracted from the solid fat or " suet " of cattle, sheep or horses. The quality varies, depending upon the season, the food and age of the animal and the method of rendering. It comes to the market under the classification of edible and inedible, and is more specifically identified as beef tallow, mutton tallow or horse tallow. The better quality is nearly white and grows whiter upon exposure to air and light, though it usually has a slightly yellowish tint. It has a well-defined grain and clean odor. It consists chiefly of stearin, palmitin with some olein. Tallow is by far the most extensively used and important fat in the making of soap, but by means of the hydrogenation process, tallow-like products are now being made from vegetable oils as well as fish and whale oils, which are beginning to replace tallow in soap making. Beef Tallow. The fat from different parts of the animal are, as a rule, not kept separate during the rendering, except when the tallow is to be used in making oleomargarine. In this case selected fat is rendered at as low a temperature as possible. The oleo stock which is obtained is usually clarified, as by washing with weak brine. The oil is allowed to grain and is then pressed. The fat which is expressed sets to a soft buttery consistency and is known as oleo or oleo oil. The residue is in the form of hard cakes and is termed oleo stearin or beef stearin. In cold weather, when a more liquid oleo oil is required, the pressing is not as thorough, so that both products are softer and the yield of stearin is greater. All the other fatty portions of the animal are rendered to produce the maximum yield of fat. These form the various grades of tallow, most of which goes to the soap maker, but some of the better grades are employed for edible purposes. When OILS, FATS AND WAXES 311 fresh, beef tallow is nearly white, odorless and almost tasteless, but the lower grades have a strong odor and flavor. A con- siderable quantity of tallow finds application in preparing lubri- cating greases, and leather dressings. Mutton Tallow. As a rule mutton tallow is harder than beet tallow, although in other respects it is very similar to it. The methods of rendering are about the same as for beef tallow. Mutton tallow tends to turn rancid on keeping, and hence is not often employed in butter substitute manufacture nor preferred in high grade toilet soaps. Horse Fats. When in a fresh condition horse fat is of a yellow- ish color, of a buttery consist ency, and neutral in reaction. On being allowed to stand for some time it separates into solid and liquid portions. It is now a commercial article owing to the large consumption of horse meat. In some localities it is used for edible purposes in place of lard; its chief use, however, is in the manufacture of soap. The bleaching of tallow is often practiced and fuller's eartn is useful for this purpose. The following procedure shows, the method employed. A quantity of tallow is melted and charged into the bleaching tank. The latter is steam jacketed and is provided with a mechanical agitator or a coil for stirring by com- pressed air. The tallow is heated to 82° C. and 10 lbs. of dry salt per ton of fat is added and thoroughly mixed by agitation. The salt coagulates any albumen and dehydrates the fat. The whole mass is allowed to settle for several hours. Any brine which has separated is drawn off from the bottom and the tem- perature of the fat then raised to 71° C. Fuller's earth to the extent of 5 per cent of the weight of the tallow is added and the whole mass agitated about thirty minutes. The bleached fat containing the earth is pumped directly to a previously heated filter press and the issuing clear oil may be run directly to the soap kettle. One of the difficulties experienced in the operation is the heating of the press to a temperature sufficient to prevent solidi- fication of the fat without raising the filter press to too great a temperature. To overcome this the first plate is heated by wet steam. Air delivered from a blower and heated by passage through a series of coils raised to a high temperature is then substituted for the steam. The moisture produced by the con- densation of the steam is reconverted to vapor by the hot air and is carried on gradually to each succeeding plate, where it condenses 312 ELEMENTS OF INDUSTRIAL CHEMISTRY and again vaporizes. In this way a small quantity of water is carried through the entire press, raising its temperature to 80°-100° C. This temperature is subsequently maintained by the passage of hot air. By this method of heating, the poor con- ductivity of hot air is overcome through the intermediary action of water vapor and the latent heat of steam is utilized to obtain the initial rise in temperature. The cake in the press is heated for some time after the filtration is complete to assist drainage. After such treatment the press cake should contain approximately 15 per cent of fat. Lard. By rendering the fat which surrounds the kidneys and bowels of the pig a product is obtained known as " leaf lard." This, however, constitutes only a small portion of the product sold under this name. The following grades are recognized in the trade: Neutral lard No. 1, which is prepared by rendering the leaf in a fresh condition at a temperature of 50 ° C. This is used in the manufacture of " oleomargarine. " Neutral lard No. 2, which is obtained by rendering the back fat in the same way as No. 1. It is used by confectioners and biscuit makers. Leaf lard is obtained by subjecting the residue from neutral lard to steam heat under pressure. Choice kettle-rendered lard is pre- pared from the residue of neutral lard No. 1 by heating it, together with fat from the back, in steam-jacketed open kettles. Prime steam lard is the product obtained from other parts of the hog by rendering in tanks by direct application of steam. Lard is of a pure white color and has, at ordinary temperature, a salve-like consistence. It is often admixed with beef fat, beef stearin, cotton seed oil, cotton seed stearin, and other vegetable fats and the composition employed as a substitute for pure lard. Lard " compound " is made in enormous quantities by thick- ening edible cotton seed oil with oleo stearine so as to obtain a product of lard-like consistency. Stearin from other sources similarly may be used as a thickener or stiff ener and hydrogenated cotton seed oil or " vegetable stearin " is now being used for this purpose. Butter Fat. This product is obtained from the fat contained in cow's milk, and is used entirely for edible purposes. BUTTER SUBSTITUTES. The butter substitutes on the market consist of mixtures of animal fats and vegetable fats and oils. They are sometimes colored yellow with annatto or oil soluble yellow. More often no coloring agent is used, owing to the pure food law. The animal fats are oleomargarine, " oleo oil," or OILS, FATS AND WAXES 313 neutral lard. The vegetable oils used are, generally, cotton seed oil and cotton seed stearine. Hydrogenated oils are beginning to be used. In the manufacture of oleomargarine the freshest materials are employed, great cleanliness being necessary. Methods of preparing the oil basis as well as the procedure of working this into oleomargarine vary considerably, but the fol- lowing will illustrate the character of the operation. Kidney fat is removed from the slaughtered animal as quickly as possible, carefully selected, washed with warm water, and thoroughly cleaned. This selected fat is then rapidly cooled, cut, shredded and ground in a roller mill. The fat thus disintegrated is placed in tin-lined steam-jacketed kettles and heated to 45° C, at which temperature a portion of the fat separates. The mass is clarified by sprinkling in salt and the liquid portion is run off into shallow tin-lined pans. On cooling the bulk of the stearine crystallizes. The cooled mass is then subjected to hydraulic pressure and oleo oil is collected. The oleo oil is churned with the vegetable oils and fats and with " pasteurized " skim milk. The object of churning is to over- come the tendency of the oleomargarine to crystallize. From the churn the margarine is run into cooling tanks, where it comes in contact with ice water. The solid mass thus obtained is worked in a kneading machine to remove the water, and it is here colored and salted to taste. Some manufacturers also add " butter flavor," which consists, for example, of a mixture of propionic acid, butyric acid and caproic acid or ethers. This also makes the margarine upon analysis appear more like pure butter. LIQUID WAXES. Sperm Oil. The most important member of this class is sperm oil, which is obtained from the head and blubber of the sperm whale. The head oil, which is the more valuable, when first separated is clear and limpid, but changes to a hard mass on standing. The body oil when fresh is of a light straw color. The two oils sometimes are mixed together and allowed to stand for two weeks before refining. The solid por- tion which separates is removed from the oil by subjecting to hydraulic pressure at 32° F., whereby a clear oil is obtained known as " winter sperm oil." The press cake is then warmed to about 50° F., and again pressed, thus giving " spring sperm oil." The residue from the second pressing is allowed to stand for several days at a temperature of about 80° F. It is then subjected to hydraulic pressure, whereby " taut-sperm oil " is the result. The oils obtained from these three pressings vary in color from 314 ELEMENTS OF INDUSTKIAL CHEMISTRY pale yellow for the refined oil to brown in the last named product. No. 1 sperm oil is a high grade of body oil and is very pale, almost water white in color. No. 2 sperm oil is darker and usually has an orange color. The specific gravity of sperm oil at 15° C. varies from 0.8799 to 0.8835 (0.8820 being a fair average value), its saponification value from 125.2 to 132.6, and its iodine value from 81 to 90. It is used as a lubricating oil and in leather finishes. The extent of the latter use depends upon the price of lard oil. Sperm oil contains practically no glycerine. The term " spermaceti " is sometimes commercially used to refer either to the head oil containing spermaceti, or to the head oil with its content of spermaceti mixed with a certain amount of body oil. SOLID WAXES. Carnauba Wax. This is a very hard, sulphur-yellow, or yellowish-green substance, melting at about 84°, of nearly the same specific gravity as water, and leaving on ignition a trifling quantity of ash, which often contains iron oxide. It is a wax which exudes from the leaves of the Corypha cerifera, a palm tree growing in Brazil and a few other South American countries. The white powdery mass which is scraped off from the sun-dried leaves is thrown into boiling water, thus melting the wax which collects as a solid mass on cooling. The crude product is dark in color, but on refining becomes much lighter. It has a specific gravity of from 0.990 to .0999, the sa- ponification value being from 79 to 95, and the iodine number about 13.5. When heated the wax gives off an agreeable aromatic odor. The principal use of carnauba wax is in floor waxes, polish- ing pastes and for raising the melting point of soft waxes. It is sometimes used in phonograph cylinders and for candlemaking. Japan Wax. This is a hard tallow-like mass which surrounds the kernels of the berries of several varieties of sumach trees found in China and the western provinces of Japan. The berries are collected and stored until they have fully matured, then are crushed and winnowed to separate the husks. The powdered mass so obtained is put into sacks and subjected to pressure. The berries yield from 15 to 25 per cent of a greenish, tallow- like mass which is refined by remelting and filtration. The wax is v bleached by exposure to sunlight, just as is done in the case of beeswax. Japan wax brought to this country is usually of a pale yellow color and although quite hard has a slightly sticky feel and possesses a characteristic odor. When the wax has been OILS, FATS AND WAXES 315 kept for a long period it acquires a rancid smell. It is said that perilla oil is used as an adulterant. Japan wax consists chiefly of plamitine and free palmitic acid. The free fatty acids vary considerably, but range from 4 to 12 per cent or higher. The specific gravity ranges from 0.975 to 0.984. The saponification value is about 220 and the iodine number from 4 to 15. Being a glyceride Japan wax is readily distinguished from the true waxes by its saponification value and by yielding glycerine on saponification. The wax is some- times adulterated with a considerable proportion of water, ranging as high as 30 per cent. Its principal use is in floor waxes, as a constituent of various polishes and dressings and in finishing leather. Chinese Wax. This material, also known as insect wax, is a secretion of an insect inhabiting a variety of evergreen tree found in China. The wax is yellowish white in color and is nearly odorless and tasteless. It resembles spermaceti in appearance, but is considerably harder. Insect wax is used for making candles, for polishing purposes and as sizing for paper and cotton goods, but on account of its extensive use in China it does not find its way to our country to a large extent. Myrtle or Bayberry Wax. The wax is obtained by boiling the berries of various species of Myrica with water. The wax has a green color due to chlorophyll, but may be bleached on exposure to sunlight or air. The fatty acids of this waxy material consist chiefly of palmitic acid. The saponification value is 205 and the iodine number 2-4. The wax is prized for use in the manufac- ture of so-called bayberry tallow candles. Candelilla Wax. This wax is found coating the entire surface of a plant that grows wild in the semi-arid regions of northern Mexico and southern Texas. The plant is reported to be abun- dant over large areas of this section, where it occurs as bunches of leafless, reed-like stems 2 to 4 feet high and from one-fourth to one-half inch in diameter. The common name given to the plant by the Mexicans is candelilla. According to competent botanical authorities it is in all probability Euphorbia antisyphil- itica. The wax may be obtained by immersing the plant in boiling water, when the wax separates and rises to the surface. Obtained in this manner it is usually of a dark brown color due to the presence of minute fragments of bark or other foreign matter. When refined the wax is opaque to translucent and of a brownish-yellow color. The wax is harder than beeswax, but 316 ELEMENTS OF INDUSTRIAL CHEMISTRY not as hard and brittle as carnauba wax. The specific gravity of the well refined wax is 983, melting point 67-68, saponification value 65, iodine number 37 and the refractive index 1.4555 at 71.5° C. Candelilla, like carnauba wax, is used in polishing compositions and for raising the melting point of softer waxes. Wool Wax, Lanolin. In the scouring of wool, preparatory to spinning, a product called wool fat or wool wax is obtained. This is usually removed from the fleece with solvents. The crude product finds application in the currying of leather, while the, purified product "lanolin" is used in pharmaceutical prep- arations. The preparation of lanolin is a complicated operation and much secrecy is maintained with regard to the precise methods employed. Beeswax. This product is secreted by the honey bee, and serves as the material for building up the honeycomb. The comb is melted in hot water, strained to remove impurities, and sub- jected to hydraulic pressure. The press cake is boiled a second time and again pressed. Beeswax is of a yellow color, and practically tasteless. Spermaceti. This wax occurs in the head cavity and the blubber of the sperm whale. Its method of preparation is indicated under sperm oil, of which it constitutes the largest part of the solid portion. In the refined condition it forms white lustrous masses, is very brittle and can be easily rubbed into a powder. Its chief use is in the manufacture of candles. Shellac Wax. In bleaching shellac the raw lac is dissolved in aqueous alkali and a hard waxy material separates, which is much prized for use in polishing compositions and shoe black- ings. The wax resembles carnauba wax in polishing qualities. Shellac wax possesses a brown to yellow color and when heated gives off an odor suggestive of shellac. Montan Wax. By extraction of the lignites found in Saxony and Thuringia by means of volatile solvents, a waxy material known as montan wax is obtained. The crude wax is of a dark brown color, but by distillation with superheated steam a white or nearly white product melting above 70° C. is obtained. Mon- tan wax is finding a constantly increasing field of application as a substitute for carnauba wax. CHAPTER XV LUBRICATING OILS General Considerations. The object of lubrication is to diminish friction and thus conserve power. The shaft does not (or should not) come in contact with its box, but revolves on a thin film of lubricant. I like the conception of Southwick that the shaft rotates on the molecules of the oil, as it were upon the balls of a ball bearing. The resistance which the particles of tins film offer to being torn apart, or the shearing modulus as the engineer terms it, measures the efficiency of the lubricant em- ployed, consequently the cardinal principle underlying all lu- brication is to use the thinnest (or least viscous) oil that will stay in place and do the work. Another important consideration to be observed in choosing a lubricant is, that it should not absorb oxygen from the air, forming a gum which would increase the viscosity, or turn rancid, and attack the metals with which it is brought in contact. The liability to oxidize or gum can be shown by the gumming test, which also has been found to be a measure of the extent to which an oil will carbonize in a gas or gasoline-engine cylinder. Be- sides these two tests, which may be considered as measuring the efficiency of the oil, other tests are employed which either measure the safety, serve to identify the oil, or to determine if it be suit- able for the purpose for which it is intended. Such are the flash and fire tests, the evaporation test, the free acid test, and the test for thickeners or soap; while the specific gravity of a mineral oil, iodine, Maumene and saponification values of an organic oil serve either to identify it or indicate if it be adulterated. The cold test and friction test show its availability under conditions approximating that of use. Choice of Oils for Certain Purposes. An oil should be sufficiently fluid to flow readily between a journal and its bear- ing at the temperature of use, and not be forced out by the pres- sure under which it is running, or to which it is likely to be exposed. Any viscosity in excess of this means a needless waste of power. 317 318 ELEMENTS OF INDUSTRIAL CHEMISTRY The fact should not be overlooked that mineral oils lose their viscosity rapidly when heated, more so than the organic oils, and that the tendency of the latter is to increase the viscosity. A suitable lubricating oil should not gum or thicken on expo- sure to the air; it should not give off inflammable vapors below 300° F., nor lose more than 4 per cent on exposure for a work- ing day at the temperature of the bearing upon which it is used. It should contain no acid to attack the bearing or shaft. It should have the least possible cohesion among its own particles and the greatest possible adhesion to the metals of which the shafts and bearings are composed. Petroleum oils fulfill the first condition and animal or vegetable oils the last. WATCH OIL. For oiling the most delicate machinery, as watches and clocks, the oil obtained from the dolphin, blackfish or " snuffer " is used. This exists in the cavities of the jaw and also in the brain or " melon " of the fish. It is rendered at a low heat, chilled and filtered at a low temperature, bleached and refined by sunning in contact with lead plates to remove acid. It is a pale yellow, very fluid oil of peculiar odor. SPINDLE OIL. This is the lightest and most fluid of the lubricating oils. The gravity varies from 27-35° Be., the flash from 320 to 430° F., the viscosity 30 to 400 seconds, Saybolt at 70° F., and the evaporation test should not be over 4 per cent. From what has already been said, nowhere is the necessity for low viscosity greater than in the case of these spindle oils when the bearings are multiplied by thousands. A case is on record where the increase in the viscosity of the spindle oil stopped the engine and shut down the mill. Besides being used for spindles it is used for sewing machines, typewriters, etc. LOOM OIL. This is merely a heavy spindle oil. One which the writer tested had a gravity of 28°, flash 360° F., and viscosity of 203 seconds. Here, as in the case of spindle oils, the evapora- tion test should be low, as the hydrocarbon vapors formed have occasioned serious fires. ENGINE OILS. Engine oils are classed as light and heavy; besides being used for engines, as their name denotes, they find general employment for shafting, machinery, etc., about the mill or works. They are usually hydrocarbon oils of gravity 32-23°, flash 300 to 430° F., and viscosity from 50 to 400 seconds at 70° F. Where the duty is heavy or the bearings are rough, they are sometimes mixed with animal oils, as lard or whale oils. LUBRICATING OILS 319 CYLINDER OILS. Cylinder oils, or more accurately, steam cylinder oils, as the Germans call them, are divided into low and high pressure. Here a different problem has to be met, that of making the oil adhere to the surfaces of the piston and valves. This is accomplished by the addition of some fatty oil which adheres to the metals and the mineral oil adheres to it. The action of the fatty oils would seem to be analogous to that of a mordant in fixing dyes. Pure fatty oils, while they have been, and may now in some cases (with low pressures) be used, are open to the objection that these, being giycerides, are decomposed by high-pressure steam with the liberation of fatty acids which attack the iron of the cylinder, causing pitting and scoring. C 3 H5(St)3+3H 2 = C3H5(OH)3+3H St. 1 On the other hand, when the condensed water from the exhaust steam is used as boiler-feed water, owing to the fact that these fatty oils emulsify so well with it, renders it necessary to use pure mineral oils. The cylinder stocks, that is, the pure petroleum bases, have the following characteristics: Gravity 23-28° Be., flash 500 to 630° F., viscosity 100 to 230 seconds at 212° F. It would seem hardly necessary to state that the low-pressure oil should have the lower of these figures. The viscosity of cylinder oils should be taken at the temperature corresponding to the pressure at which they are to be used. The fatty oils used are, degras, tallow, linseed, cotton seed, and blown rape, all as free from acid as possible and in quantities varying from 1 to 25 per cent. A lubricant which seems to promise unusually well for cylinders is an artificial deflocculated graphite suspended in water. This is so fine that it will go through the pores of the finest filter paper and it seems to fill the pores of the metal, ensuring tighter fitting piston rings and at the same time possesses little cohesion. GAS ENGINE OILS. Gas engine oils, particularly for the cylinders, should possess as their chief requisite, besides that of lubrication, the property of not carbonizing at the temperatures attained. The liability of carbonization seems to be intimately connected with the amount of tarry matter yielded in the gum- ming test. For automobiles the oils of the following character- istics have yielded good results: Flash 380-450° F. (covered tester), viscosity 180-185 seconds (at 100° F., Saybolt Universal)., 1 St = Stearic acid = C17H35COOH. 320 ELEMENTS OF INDUSTKIAL CHEMISTRY gumming tests very slight or slight. For large size gas engines probably a heavier oil would be required having these char- acteristics: Gravity 26-28° Be., flash 400-475° F., viscosity 250 seconds at 70° F. GREASES. Gillett divides the greases into six classes: 1. The tallow type, a mixture of tallow with palm-oil soap with some mineral oil; this was common twenty years ago. 2. The soap-thickened mineral-oil type, a mixture of mineral oh\ usually with lime or sometimes soda soaps, the commonest type at present. 3. Types 1 or 2 mixed with graphite, talc, or mica. 4. The rosin-oil type, a mixture of rosin oil thickened with lime, or sometimes litharge, with mineral oil. They contain often 20 to 30 per cent of water and are used as gear greases. They may contain also tar, pitch, ground wood or cork, and any of the fillers mentioned in 3. 5. Non-fluid oils — oils or thin greases stiffened with " oil pulp " or " dope," i.e., aluminium oleate. 6. Special greases with special fillers. These greases show a high coefficient of friction at first, causing a rise of temperature which melts the grease, producing the effect of an oil-lubricated bearing. The graphite greases show an unexpectedly low lubricating power; the rosin greases show a high friction at first, but after the bearing has warmed up compare well with the more expensive greases. The high mois- ture content would seem to have the advantage of making them less sticky. The line soap greases (Class 2) are not as good as the tallow greases (Class 1), and are inferior as lubricants to those compounded with soda soaps. BELT DRESSINGS. Where the object is the softening of the belt they are usually mixtures of solid fat, waxes, degras, or tallow with fish oils to make the belts cling; in some cases they are mixtures either of corn or cotton seed oils, which have been treated with sulpur chloride, with mineral oil and thinned with naphtha, or they may be mixture^ of the above fats with rosin or rosin oil. These are least desirable. Preparations containing wood tar are also used. Car Oils, Reduced Oils, Well Oil, Black Oils. These are commonly crude oils from which the more volatile portions, the naphthas, and, burning oils, have been removed by distillation. Some railroad specifications require a gravity of 29° Be., flash LUBRICATING OILS 321 point 325° F., cold test 5 to 15° F., according to the season of use, and a viscosity 100 to 120 seconds at 70° F. Compressor and Ice-machine Oils. These are light spindle oils of a gravity of 26-27° Be., 60 to 100 seconds at 70° F., viscosity, 325-360° F., flash, and a cold test of to 4° F. CRANK-CASE OILS. These should emulsify but little with water, consequently should be pure mineral oils. Much seems to depend upon the water with winch the oil is mixed in the crank case, so it is difficult to predict how oils of practically the same constants will behave with different waters. An oil giving these figures has proved eminently satisfactory: Gravity 26-27° Be., flash 455° F. 3 viscosity 100° at 212° F. Milling Machine or Soluble Oils. These are usually lard, suiphonated oils, or mineral oils held in suspension by soaps or alkalies, as borax, sodium carbonate; the soaps are either ammonium, sodium, or potassium, with oleic, resin, or sulpho fatty acids. They should not appreciably attack the metals and should form a persistent emulsion. The U. S. Navy require- ments are that upon twenty-four hours' standing upon polished brass or copper it must not be turned green. German require- ments are that a steel plate, 30X30X3 mm. should not lose more than 18 mg. in a 1 or 2 per cent solution of the oil after lying for three weeks in it. NEUTRAL OIL. An oil without "bloom," of 32-36° Be., 290-318° flashpoint and 47 to 81 seconds viscosity at 70° F. " OIL-DAG." This is the term applied by Acheson, the discoverer and maker of carborundum and artificial graphite to a colloidal suspension of pure deflocculated graphite in oil, so fine that it will go through the finest filter paper. Care must be taken that the oil is free from acid, whether mineral or organic, as this causes a precipitation of the graphite. A small quantity of " Oil-dag " in an automobile oil caused it to last for 700 miles instead of 200, the usual distance with one filling without the graphite. OlLLESS BEARINGS. These are wooden blocks, often of maple thoroughly impregnated with 35 to 40 per cent of grease, which replace metal journals; the grease may be a mixture of paraffine, myrtle, or beeswax with stearine, tallow, or vase- line. SCREW-CUTTING OILS. These are often mixtures of 27° Be. paraffine, and 25 per cent fatty oil, preferably cotton seed, although pure lard was formerly used. 322 ELEMENTS OF INDUSTEIAL CHEMISTRY STAINLESS OILS. These are spindle or loom oils mixed with fatty oils — lard or neatsfoot; the fatty oil being more easily emulsified or possibly saponified in the scouring process, aids materially in washing out the mineral oil with which it is mixed. One type of these oils is compounded of 40 per cent neutral oil, 30 per cent cotton seed, 20 per cent olive, and 10 per cent first-pressing castor. TRANSFORMER OILS. These should be either pure rosin or mineral oils and be free from water, acid, alkali, and sulphur. They may be freed from the first two impurities by treatment with sodium wire after the usual method of organic chemistry. They should not lose more than 0.2 per cent when exposed to 100° C. for five hours, have a viscosity of about 400 seconds at 70° F., a flash of 340-380° F. and remain liquid at 32° F. TURBINE OIL. Steam turbines require a pure mineral oil of most excellent quality. As the oil is circulated around the bearings by a pump it should be of low viscosity and gravity and free from acid, mechanical impurities, and tendency to resinify; it should be low in sulphur contents. An oil of 30° Be., 150 seconds viscosity at 70° F., and 420° F. flash has given good results. CHAPTER XVI SOAP, SOAP POWDER AND GLYCERINE Theory of Soap-making. When tallow, lard, palm oil, corn oil or other fatty material is treated with a solution of sodium hydroxide or potassium hydroxide, a chemical change takes place, resulting in the formation of a product soluble in water, and possessing .properties entirely different from the original oil or fat employed. When the soluble product is treated with an acid the resulting body becomes insoluble. If this operation is conducted in a quantitative manner, it will be found that the insoluble substance obtained from the acid treatment is only about 90 per cent of the original weight of the fat. Something, therefore, has been eliminated during the operation. This may be recovered from the acid liquor by evaporation, and is found to possess a sweet taste, an oily consistency, and is known as glycerine. The insoluble portion recovered above has an acid reaction, when combined with alkali is soluble, and upon inves- tigation proves to be made up principally of such compounds as stearic, palmitic and oleic acids. Thus we draw the con- clusion that fats are glycerides of fatty acids; and that in soap- making the caustic alkali decomposes the fatty glycerides with the formation of salts of the fatty acids known as soap, and the separation of glycerine. In boiled soaps this glycerine is separated, while in half- boiled or cold-made soaps it is not, and remains a part of the soap. This reaction is indicated in the following equation: C17H35COOCH2 NaOH Ci 7 H 35 COONa CH 2 OH I I Ci 7 H 3 5COOCH 2 -|-NaOH = Ci7H35COONa-|-CHOH I I C17H35COOCH2 NaOH Ci 7 H 35 COONa CH 2 OH Glyceryl stearate in Caustic Sodium stearate Glycerol tallow soda (Soap) (Glycerine) 323 324 ELEMENTS OF INDUSTRIAL CHEMISTRY Although there are many substitutes for tallow which are employed in soap-making, they all require an alkali for saponifi- cation and all act in the manner above described. There are, however, some substances, such as rosin, which, when used in the production of soap, the action as stated above is modified. Rosin is an acid and unites directly with the caustic soda to make a salt. Classification of Soaps. Soaps are divided into two principal classes, namely: hard soaps and soft soaps. In the former caustic soda is employed and in the latter caustic potash is used. The term soda soap and potash soap are also some- times used to distinguish the two classes. Further, depending upon the method of manufacture, we have boiled soaps, half- boiled soaps, and cold-process soaps. Hard soaps are of various kinds, such as castile, curd, mottled, yellow, and transparent. Soft soaps come on the market as a paste or in a semi-liquid condi- tion. In some soaps both caustic soda and caustic potash are used in their preparation. As soap is used for a great va- riety of purposes, its preparation must necessarily vary. The choice of stock depends upon whether a high-grade soap is to be made,' in which the choicest materials must be selected, or whether a cheap soap is to be manufactured. Soap is used very largely in the textile and leather industries, and should be specially prepared for the purpose to which it is to be put. Boiled Laundry Soap. The melted fat and oil is pumped into the soap kettle (Fig. 100) from the storage tanks and with it a small stream of 18° caustic soda lye is run in from a separate line. Enough steam is turned on to keep the con- tents well mixed. The union of the fat and caustic soda sets up quite a little " heat of reaction " and very soon the steam may be eased off. As much boiling Fig. 100. SOAP, SOAP POWDER AND GLYCERINE 325 room as bossible is saved for finishing the saponification. The lye is kept slightly behind the stock until the fat is all pumped up. An excess of caustic can be determined by rubbing a sample taken from the kettle between the fingers until cool; a sharp taste denotes an excess of caustic. Toward the end of the saponification, the soap begins to take on a darker color, become smooth and assume a high gloss. A sample taken on a small flat piece of wood, called a paddle, is now quite trans- parent and rolls off the paddle in sheets. The lye must now be added in small lots with frequent testing as described below. An alkalinity not over .20 per cent is very desirable and a kettle which holds this alkalinity after three boilings and tests may be considered as finished for this change. GRAINING. The soap must now be separated from the free glycerine and is done by adding salt, in which solution the soap is insoluble. This is called " graining." The kettle is well boiled, dry salt shoveled in or a brine (salt) solution is run in and mixed through by boiling until a sample on a paddle shows the soap in a broad flat curd from which the lye runs freely. The steam is shut off, the soap rising to the top of the kettle and the salt solution containing the glycerine settles out on the bottom. SECOND CHANGE. The lye from the first change is drawn off from the bottom into an empty kettle until soap appears and then shut off. The soap is boiled up, a dash of 18° Be. caustic soda added and after being well boiled through, the alkalinity is tested. If an excess of .20 per cent is not shown, more caustic is run in, boiled, and tested until the soap holds this alkalinity. Water is now added until the soap shows, after boiling through, a smooth appearance. This is called "flattening out." When the water is all in, the graining is re- peated as before. ROSIN SAPONIFICATION. A straight tallow soap is rather slow in lathering and needs a softening agent, such as oil or rosin to increase its solubility. In toilet soaps oil is used and in laundry soap rosin. The rosin is incorporated in two ways, either by direct saponification in the same kettle as the first change was made, or by a separate saponification in another kettle and a subsequent incorporation. Direct Saponification. The first change soap after all the wash changes have been made and last lye drawn is boiled up, a little salt, any scrap or broken soap added and enough 35 to 326 ELEMENTS OF INDUSTRIAL CHEMISTRY 30° caustic lye run in to " open " or grain the soap. While the kettle is slowly boiling, the rosin, cracked up in small lumps, is shoveled in. From time to time samples taken from the boil- ing soap are tested for alkalinity, and if not up to .2 to .3 per cent, enough caustic is added to bring it up to the mark. While the rosin is being saponified in this way, a " second rosin " lye from another kettle is pumped in and its caustic content assists in dis- solving the rosin. An excess of caustic lye must at all times be present in this change, as no salt is to be added for graining, the free caustic doing this graining. This is the only lye which is run' away to the sewer when settled and it contains nearly all the soluble impurities. When the rosin is all in and the final test for free caustic made, the soap is allowed to settle, generally over night, so as to get out into the lye as much color and impurity as possible. Saponified Rosin. Water and soda ash (Na2COs) are boiled in a kettle to make a 12° Be. solution. One thousand pounds of rosin require 150 pounds of ash. The solution is kept slowly boiling while the rosin is shoveled in, and the solution of the rosin completed by frequent short boilings. It is finished when no more rosin is found floating on the surface after the boiling and settling. Just before it is pumped out of the kettle onto the tallow soap enough dry salt is added to make it pump well. The incorporation with the tallow soap proceeds the same as with the direct rosin saponification except that less caustic soda is used. SECOND ROSIN CHANGE. When the first lye has been drawn, the soap is brought to a boil and enough 25-30° caustic soda run in to make an alkalinity of 3-4 per cent and continued boiling while a boiled up nigre of a previous boil is pumped in to fill up the kettle. The main object of this change is to insure a com- plete saponification of the rosin. STRONG CHANGE. When the second rosin lye is off, the soap is boiled up and enough water or 4-5° caustic lye is added to smooth or flatten out the soap and get it into a condition to drop or settle out the excess caustic with the other alkaline impurities. FINISH. After a few hours, the soap will drop a heavy, slimy lye which is drawn off and the soap boiled up. # Experience alone now dictates the procedure. If the soap is thick (heavy), a little water is run in it and boiled through, which leaves the soap as it boils in a smooth, high-polished condition, and when SOAP, SOAP POWDER AND GLYCERINE 327 the steam is shut off the process of settling or clarification can readily be seen at once on the surface. SETTLING. The soap should stand about a week to be well settled. During the settling the soap separates into two layers, the upper part being the good soap, i.e., a soap containing but traces or a small amount of free alkali and about 31-32 per cent of water, which seems to be the amount of water needed to make a good settled soap, a sort of water of constitution, and a lower layer or " nigre " which is a soap with a large amount (55-70 per cent) of water, free alkali and any other alkaline impurities (Na 2 S04+NaCl) present. The purpose of the last change is to manipulate the soap, so as to concentrate these impurities in the nigre. CRUTCH-ING. After settling, the soap is pumped out of the kettle through the leg as shown in Fig. 100. The " crutcher " is a mixing-machine which derives its name from the early soap factories. This mixing was then done by hand with a wooden stick shaped like a crutch. The " crutcher " (Fig. 101) is sur- rounded by a jacket into which either steam for heating or water for cooling is introduced. It has an Archhnedean screw for the stirring and in the center a cy- linder over which the soap passes during the agitation. Any ma- terial such as sodium carbonate, sodium silicate, borax, starch, talc, grit or perfume can thus be incorporated into the soap. All laundry soaps carry some such rilling, which is by no means an adulteration and needs no apology for being present. The tem- perature at which the soap is dropped is carefully controlled in each crutcherful and regulated by introducing either steam or water to the jacket. Good results are obtained by keeping this heat about 140-144° F. When thoroughly mixed the soap, still semi-liquid, is dropped out of the bottom of the crutcher into frames. The pump is shut off when the nigre is reached and the nigre boiled up to be pumped out into a second rosin change. Fig. 101. 328 ELEMENTS OF INDUSTRIAL CHEMISTRY FRAMING. These "frames " are tight boxes supported on a truck (Fig. 102) and hold one entire charge from the crutcher. The sides are bolted together in such a manner that they may be easily taken off when the soap is hard enough. This is called " stripping." The time of " stripping " depends on the season — three days in winter and four days in summer. The soap should be stripped as soon as possible, as the soap cuts better when cool. With soap of good body, the cutting may be done the next day. SLABBING AND CUTTING. When the soap is hard enough, it is run through the " slabber " (Fig. 103). This is a machine with a cutting-head large enough to slab the whole frame at once. The cutting-head has wires drawn across it at spaces equal to the thickness of a cake of soap. Each slab is now put through the " cutting-machine " (Fig. 104) and given two cuts, one through its length and the other at right angles to it, which turns out the slab completely cut into cakes. In the power cutting machines of latest type the cut cakes fall, spaced, onto a rack which is lifted from the table and placed on a truck for transportation to the drying-room, which may be done artificially or allowed to stand in well-ventilated rooms. PRESSING AND WRAPPING. The soap stands on these racks until the surface dries over enough so that it may be handled and pressed without marring it. This is called " skinning over." SOAP, SOAP POWDER AND GLYCERINE 329 Green or fresh soap acts very badly in the presses and is easily dented in passing to the wrapping-machines (Fig. 105), which run QiifrmiQfi'pQllv ar-irl nronoroC! +V10 arvan fr»T» +V10 hnvpa ted in passing to the wrapping-machines (Fig. '. automatically and prepares the soap for the boxes. Fig. 103. Fig. 104. THE TWITCHELL PROCESS. This process is a newer method employed in some soap factories for a treatment of the stock 330 ELEMENTS OF INDUSTRIAL CHEMISTRY before soap-making, and has for its object a separation of the fat or oil into fatty acid and glycerine before it reaches the soap- kettle. It can be readily seen that the operation of making soap is then easier in the earlier or " killing " changes and re- moves the " salting-out " of soap in these earlier changes entirely, as there is no glycerine to wash out. Method. The fat or oil is first purified by steaming with about 1 per cent 60° H2SO4 for about two hours, after which the acid, impurities, and water of condensation are drawn Fig. 105, off. The melted and purified fat is run into a wooden tank, closely covered to exclude air. After heating up, 1 per cent of the " Twitchell Reagent " (sulpho-benzene stearic acid, C6H4HSO3C17H35COO) is added and the whole mass steamed for twenty-four hours with the addition from time to time of small amounts of H 2 S04< After settling, the glycerine water (15 per cent glycerine) is drawn off, neutralized with lime and evaporated to a " crude glycerine " of 88-90 per cent glycerine content. After the glycerine water is drawn off, the fatty acids are boiled with water and a small amount of lime, to remove all the soluble acids, air likewise being carefully excluded. After SOAP, SOAP POWDER AND GLYCERINE 331 this neutralization is complete, the fatty acids may then be stored in wooden tanks until ready for use. The advantages of the " Twitchell " process are: a. A larger yield of glycerine. b. A purer and stronger crude glycerine. c. A means of making rosin soaps in a crutcher without boiling the fat. a. By changing the stock into fatty acid and glycerine before the actual soap-making is begun, an opportunity is afforded to entirely free the stock of its glycerine without the use of salt. b. The crude glycerine obtained from soap lyes, called " soap lye crude,'" contains from 80 to 84 per cent of glycerol and from 7 to 10 per cent of salt. The crude obtained from the " Twitchell process," called " saponification or candle crude" carries from 88 to 90 per cent glycerol and only traces of salt. Salt is the worst part of the glycerine recovery where " soap lyes " are to be evaporated, as it keeps concentrating in the glycerine liquors during the boiling, and requires the frequent dropping of these liquors during the process of making crude glycerine to elim- inate this salt. Besides, the steam-chests of the evaporators become coated with salt during the boiling and insulates the heat. The original " soap lye " solution contains about 3 per cent of glycerol, while the " Twitchell " liquors carry about 15 per cent glycerol, thus saving a great deal of evaporation. c. With the fatty acid at hand, it is possible to make soap directly in the crutcher by the mixing of the fatty acid, alkali, saponified rosin and filling material. The fact that the fatty acids produced are somewhat darker than the original stock has been the chief objection to this method of treating fats and oils. At present there are im- provements being made in this process which claim to over- come this defect. If successful it will lead to a more general use among the soap-makers, as at present it is used chiefly by the candle-makers for producing stearic and oleic acids. SOAP OR WASHING POWDERS. These powders are mixtures of soda ash (dry Na2COs), soap (mixed in liquid condition), and water, the only difference in the many kinds on the market being in the amount of these ingredients present and the kind of soap used. According to the amount of water present, there are two general classes: those containing 10 to 20 per cent of 332 ELEMENTS OF INDUSTRIAL CHEMISTRY water being the old-style and those having 35 to 40 per cent of water, or the new-style, called usually " fluffy powders." SCOURING POWDER. This powder is made by mixing varying amounts of soap powder, silex (grit), talc, and some- times a small amount of sal ammoniac. SCOURING SOAPS. These soaps are generally made on a cocoanut-oil base. The soap after saponification is drawn to a crutcher, silex (grit) is mixed with it and the mass dropped into an asbestos-jacketed kettle or tank and run into slate molds to harden, each mold being the size and shape of the finished soap. BOILED TOILET SOAPS. The method of boiling for toilet soap is the same as for laundry soap, except that a different variety and grade of fat is employed. The raw materials consist mostly of vegetable oils to which a small amount of tallow is added. No rosin, however, is added, as the vegetable oils possess sufficient lathering quality. On completion of the boiling operation the soap is run to a continuous drying chamber, where it falls on an end- less belt and is slowly conveyed through the drying apparatus, coming out in the proper condition for the subsequent opera- tions. An older method, and one which is still used in many factories, is to crutch, frame, slab, cut, and then " chip." The " chipper " (Fig. 106) consists of an en- closed disk provided with knives which re- volve at a high rate of speed, and against which the bars of soap are pressed. The chips thus obtained are dried until brittle and are then ready for the subsequent operations. AMALGAMATOR. This machine (Fig. 107) is used for mixing the color and perfume with the chips before milling. With the use of an amalgamator a more uniform soap is obtained and at least one milling saved. In the old method of adding color and perfume to a soap, the chips were mixed in a box with color and perfume by a shovel. A uniform distribution of color and perfume was almost impossible by this method, and required five or six trips through the mill to produce the desired uni- formity. An even mixture may be obtained in an amalgamator Fig. 106. SOAP, SOAP POWDER AND GLYCERINE 333 in about fifteen minutes, and twice milling this product is sufficient. In the majority of toilet soap factories, in making up their stock, they go in the order of their color, starting with white and then making the next darker shade, like yellow, then green, pink, etc., until they finish with the darkest soap, usually tar soap. In this way the machine will only need one cleaning. MILLING. Whether the soap has been dried by the modern method or by the slower method of chipping, it is placed in a mixing ma- chine, where the necessary perfume, color, or other ingredients are added. It is then fed to the " mills." These mills con- sist of two or more rollers (Fig. 108) between which the soap Fig. 107. Fig. 108. 334 ELEMENTS OF INDUSTRIAL CHEMISTRY passes, thereby causing the added material to become well in-. corporated. The usual practice is to pass the soap between the roller six times or until the corrugated flakes have a perfectly uniform and smooth appearance. PLODDING. The milled soap is placed in the hopper of a machine known as the " plodder " (Fig. 109), where it is subjected to great pressure by means of a compression screw. In the nozzle of the plodder is a "forming plate" having an opening the size of the cake de- sired. The flaky condition of the soap as it comes from the mills is converted into a continuous bar, which may be cut to any length and stamped or pressed as desired. Milled soaps allow of the use of delicate per- fumes or other materials which would be destroyed if incorporated with the hot soap in the crutcher. The price of a soap de- pends largely upon the kind of perfume which is used to scent it, as out of the same kettle of soap may be prepared an article selling for ten cents or one dollar. Some toilet soaps are slightly superfatted, so as to over- come the harsh effect of an alkaline condition. SOFT SOAPS. Soft soaps are usually prepared by employ- ing potash as the alkali and an oil high in oleic acid as the fatty material. Saponified red oil, linseed oil, rosin, and cotton seed oil are among the chief oils used for the purpose. LIQUID SOAPS. These soaps are made in the same manner as soft soaps and are given their liquid property by addition of glycerine or alcohol. Liquid soaps are made from selected stock and the lye well settled before using. Cocoanut oil is largely used for this variety of soap. HALF-BOILED SOAPS. As the name implies, soap made by this process is not boiled. The operation is always conducted in a crutcher, the temperature of the stock being raised to about 160° F., and the lye added. The mixture of lye and fat is crutched for about five minutes and allowed to stand undisturbed Fig. 109. SOAP, SOAP POWDER AND GLYCERINE 335 for two hours. It is then crutched again until smooth, tested for excess of either fat or alkali, run into frames, allowed to set and harden as stated under boiled soaps. Half-boiled soaps con- tain all of the glycerine originally combined in the oil, and for this reason give a very satisfactory soap for toilet purposes. As there is no recovery of the glycerine it cannot be worked economically for laundry soaps. After settling and cooling, it may be chipped, milled, plodded, and pressed in the same manner as boiled soaps. COLD-PROCESS SOAPS. Soap made by this process differs from half-boiled soaps in that the oils are only heated to their melting-point and the lye added. The operation is conducted in a crutcher and the mixture stirred until smooth, when it is dumped into the frames. Floating Soaps. The soaps which float on water are prepared in the same manner as other soaps, and the specific gravny lowered by crutching at a high rate of speed, so as to pump the soap full of minute air bubbles. The same result is obtained by reversing the direction of the paddle several times during the crutching. Floating soap is never milled, but on cooling in the frames it is cut into cakes and pressed. MOTTLED SOAPS. The old-style mottled soaps were made by boiling in a kettle over the open fire and run into frames to cool. During the long process of heating, certain decompositions took place, so that when the soap cooled very slowly the excess of lye and impurities segregated to those portions which were the last to solidify. At present the same effect is produced by crutching with ferrous sulphate, ultramarine, lamp-black, or other pigment just before the soap is run into the frame. Castile or Marseilles soap sometimes have a green mottle, which changes to red on exposure. This is due to the presence of ferrous sul- phate, which has been acted upon by the lye to produce ferrous hydroxide; which in its turn is changed to ferric hydroxide by exposure to the air. CASTILE SOAP. This soap is supposed to be made from olive oil and soda lye only, but as a pure olive oil soap becomes excessively hard and brittle on standing, other oils are usually added. The oils used for this purpose vary, cocoanut, linseed, cotton seed, and corn oil being usually employed. The color of the oil influences the color of the finished product, so that we have both white and green Castile soap, due to using either a light or colored oil. Practically all Castile soap is either made by the cold or the half-boiled process. 336 ELEMENTS OF INDUSTRIAL CHEMISTRY TRANSPARENT SOAPS. These soaps are usually made by dissolving a good soda soap in alcohol, decanting away from any insoluble matter and distilling off the excess of alcohol. This leaves the soap in the form of a transparent jelly, which is dried out in molds having the form of the cake desired. Transparent soaps are also made by the cold or half-boiled process, by adding more glycerine together with a small amount of alcohol and any perfume or coloring matter which may be desired. A cheaper grade is made by adding a solution of cane sugar. SHAVING SOAPS. These are usually soda and potash com- bination soaps, made from high-grade stock. They may be made on a cocoanut-oil base with the addition of stearic acid to give body, and a gum to keep the lather from drying. Many shaving soaps contain glycerine or sugar. SHAVING CREAMS. These are potash soaps usually made on a cocoanut-oil base to which is added a certain percentage of stearic acid. TOILET POWDERS. Most toilet powders are composed largely of talc, to which varying amounts of calcium or other stearates have been added. Some powders also contain anti- septic substances such as boric acid. SOAP POWDERS FOR TOILET USE. These powders are prepared by completely drying a good grade of toilet soap and subsequently pulverizing it. They must be as near neutral as possible to avoid any irritation when used on tender skin. METALIC SOAPS. By adding soluble salts of the heavy metals to a neutral soap solution a precipitate of metallic soap is obtained. Some of these metallic soaps have very extensive application in the industries and in pharmacy. The lead soap produced by adding lead acetate to a linseed-oil soap is used as a drier in mixed paints. By boiling olive oil with lead oxide " lead plaster " is obtained. Sources of Glycerine. The world's output of crude glycerine is estimated at about 85,000 tons. It is exclusively a by-product industry of the soap and candle trades and the output depends not so much on the demand for glycerine as on the world's requirements of soap and candles. The cause of this condition is the relatively small percentage of glycerine obtainable from the fats, the theoretical amount ranging from 10.5 per cent with tallow to 13.5 per cent with cocoanut oil. In practice this is cut down by the free fatty acids always present, each 10 per cent of free fatty acids reducing the glycerine by about 10 per SOAP, SOAP POWDER AND GLYCERINE 337 cent. With the increasing use of high grade fats for butter sub- stitutes and the conversion of fatty oils to hard edible fats by the use of hydrogen and catalytic agents the soap- and candle-maker are compelled to resort to fats and oils of poorer quality than formerly. These fats are high in free acids and low in glycerine, so that the tendency seems to lie in the direction of lower yields in the future than in the past. Glycerine is a by-product of the alcoholic fermentation of sugar, the amount produced being variously stated as 3-8 per cent of the alcohol formed. At any rate, enormous quantities must go to waste in the residues from alcohol stills, as to date no commercial process has been developed for the recovery of this glycerine. Glycerine has been subject to wide fluctuations in price, the dynamite grade selling for 10 cents a pound in 1908 and 60 cents in 1916. The United States does not produce sufficient glycerine to meet its own requirements and there are from 30,000,000 to 40.000 000 lbs. of foreign crude imported annually. SAPONIFICATION. Only those industries requiring fatty acids in large amount can afford to produce crude glycerine. The candle-maker wants primarily the white, hard stearic acid. The soap-maker is after the combination of the fatty acids with soda in the form of soap and utilizes all of the higher fatty acids present. To separate the fatty acids from a fat it is necessary to break it up into its constituents. This process is called saponi- fication and is brought about by the interaction of water and fat, fatty acid being split off and glycerine being produced. The decomposition with water alone is slow and requires very high temperatures. It is greatly facilitated by the addition of a catalytic agent, which may be of an acid or alkaline character. In the soap industry caustic soda is used, the soap formed emulsi- fying the fat and exposing a large surface of fat to the action of water. In the candle industry a small percentage of lime or magnesia is used, and the reaction hastened by a high temperature obtained by the use of autoclaves under a steam pressure of 250 pounds. In the Twitchell process, used by both the soap and candle industries, the catalyzer is a sulfo-fatty acid, the hydrogen ion assisting the reaction and the sulfo-fatty acid acting as an emulsifier. SOAP-LYE CRUDE GLYCERINE. This forms the principal source of supply. After the saponification of the fat by caustic soda the soap is thrown out of solution by the addition of salt. 338 ELEMENTS OF INDUSTEIAL CHEMISTRY The mother liquor or spent lye contains 4-5 per cent glycerine. All the salt and the bulk of the impurities present in the fat is purified by the addition of a crude persulphate of iron, obtained by the action of oil of vitriol on pyrites cinder or iron ore, or by the use of aluminium sulphate. A precipitate of the hydrate is thrown down, carrying with it albuminoids and metallic soaps of the higher fatty acids. This is removed by a filter press. The purification is only a partial one, and in case low grade stock has been used large amounts of impurities remain in the dilute glycerine. The next step is evaporation, formerly considered a process of great difficulty when fire-heated kettles were used, as the salt caked on the sides of the vessel. The modern method is to con- centrate in a vacuum evaporator. At a vacuum of 27 to 28 inches the boiling point is reduced to such a degree that the salt separating does not adhere to the heating tubes, but drops into a chamber placed below. Exhaust steam may be used during the greater part of the evaporation, live steam being used to finish off. The salt is raked out on a vacuum-filter and is washed practically free from glycerine and returned to the soap-kettle. Crude glycerine when cold has a specific gravity of 1.30 or 33.5° Be. It is a saturated solution of mineral salts in glycerine and water. The salts consist largely of sodium chloride with some sulphate and the sodium salts of the lower fatty acids. It is slightly alkaline with soda. The glycerine is usually about 80 per cent. It may run down to 60 per cent in bad crudes and up to 87 per cent in highly concentrated crudes of the best quality. The organic matter not glycerine will average 2-3 per cent in good glycerines. The ash will run from 8-10 per cent in good crudes; 15 per cent and more in bad crudes and crudes carrying solid salt. Soap-lye crude may be easily recognized by its high salt con- tents when tested by silver nitrate, giving a heavy curdy precipi- tate. With basic lead acetate a heavy precipitate of oxy chlor- ide of lead is obtained. The specific gravity is high. Saponification Crude Glycerine. This is the by- product of the candle industry and the glycerine obtained when fats are split up by the Twitchell process, the fatty acids being used in the candle or soap trades. It is free from sodium chloride and practically free from mineral matter in the purer grades. The thin liquor from the autoclaves or Twitchell saponifying tanks after settling to separate the free fatty acids is treated SOAP, SOAP POWDER AND GLYCERINE 339 with a little lime or aluminium sulphate and filter-pressed. It is then evaporated to a specific gravity of 1.24 at 60° F. or 28° Be. The glycerine standard for saponification crudes is 88 per cent. In poor grades it will sometimes run down to 82 per cent and less and occasionally is as high as 90 per cent in high-grade crudes. The ash standard is 0.5 per cent and the organic residue 1 per cent, although these figures are sometimes greatly exceeded. As a rule Twitchell saponifications are inferior to the autoclave crudes, not because the process is at fault, but because the Twitchell method makes available the use of low-grade fats and greases, which cannot be profitably treated in the autoclave. A saponification crude is distinguished from a soap-lye crude by the absence of salt, as shown by the silver nitrate test, by its low specific gravity and small precipitate with basic lead acetate. The latter may be heavy in bad crudes, but is of a flocculent char- acter and easily distinguishable from the precipitate of lead oxy- chloride. Basic lead acetate affords a good method of finding the quality of saponification crudes, as a high-grade product gives only a slight precipitate. Crude glycerines produced by the fermentation process are but rarely met with. PURIFICATION. Crude glycerine contains mineral impurities, such as salt, sodium sulphate, carbonate, hydrate, acetate, buty- rate, caproate, etc., together with iron, lime, arsenic and other metals. As volatile impurities may be enumerated fatty acids split off from the sodium salts, acrolein produced during distilla- tion, ammonia and amines, sulphur compounds and trimethylene glycol. The last-named is contained in low-grade crudes derived from products subject to fermentation. There are also non- volatile organic substances present, such as albuminoids, resinous bodies and polyglycerols. The only method used for the separation of glycerine from these substances is distillation combined with fractional con- densation. By careful distillation the non-volatile substances are left behind in the still, and by careful control of the tempera- tures of the condensers the glycerine is condensed before the more volatile impurities. CHAPTER XVII ESSENTIAL OILS CRUDE DISTILLATION. Many of the essential oils are dis- tilled by unskilled natives in the various countries, and the layer of water is usually heated by direct fire placed under the still. It is now well known that this both decreases the yield and pro- duces an oil inferior in quality, as it subjects the material to the saponifying or hydrolizing influence of hot water and some small particles of the substance being distilled are sure to adhere to the bottom of the still, where they scorch, and contaminate the distillate with a burnt odor. Modern Distillation. In modern factories steam is generated in a boiler and passed into the still at various degrees of pressure. Usually the still is also heated either by means of a steam jacket or by a closed steam pipe placed inside the still, so as to prevent much condensation of the steam in the still. The degree of fineness of the charging material, the pressure, and therefore the temperature of the steam, the speed of its flow and numerous other working points must be adapted in each case to the apparatus in use, as well as to the substance that is being distilled and the product that may be expected. The odor and taste of all natural products are due in almost every case to a combination of a number of chemical bodies and it is only when these chemical individuals are assembled in the right proportion and combination, that the odor of the flower or material will be duplicated. Many of these chemical bodies are extremely sensitive to heat, which either destroys them or changes the odor completely, others are esters which are hydrolized by the action of steam and heat and many plants contain bodies which upon heating act to a greater or less extent on the other constit- uents. Consequently, steam distillation has its limitations and other processes must be utilized to extract the active principles desired. EXPRESSED OILS. That squeezing the rind of some fruits left a fragrant oil on the hands must have been early observed. 340 ESSENTIAL OILS 341 It is still the method which gives the finest oils of the citrus family and is the present commercial method of obtaining the oils of lemon, orange and bergamot. As cheap labor is available in Sicily, where these oils are made in quantities, and the pulp of the fruit is worked up for citric acid, the price remains quite low, although the method is slow and tedious. The peel is man- ipulated, crushing the oil cells and the oil is absorbed by a sponge, which is then squeezed and the oil filtered for the market. Machines have at times been tried to take the place of hand labor, but none of them have been found commercially satisfactory, excepting to a limited extent for the regularly shaped bergamot. MACERATING PROCESS. The process of macerating con- sists in placing the flowers in warm oil or fat, a method by which the modern flower pomades are produced in southern France. After the oil or fat has absorbed the odor of the flowers, it is strained off and a fresh lot of flowers added. This process is repeated a number of times, according to the strength of pomade desired. ENFLEURAGE PROCESS. It was found, however, that even the slight heat necessary in the macerating process is sufficient to destroy some of the more sensitive constituents of some flower odors, and so the cold enfleurage process resulted. Here a layer of fat is placed on a plate of glass, fresh flowers are sprinkled on it and after the fat has absorbed the odor, they are replaced by more flowers, and this process is repeated until the fat is saturated. This process is especially adapted to flowers like the jasmine blossom, which is known to produce perfume for some time after it has been picked and a much better yield results than when the flower is immersed in hot fat, which im- mediately stops the production of more flower oil by the blossom. FLOWER POMADES. This flower pomade, obtained either by maceration or by the enfleurage process, is then washed with alcohol, which extracts from the pomade the odorous substances absorbed from the flowers. VOLATILE SOLVENTS. Objection to the above processes has led to the more modern process of treatment by volatile solvents. Petroleum ether, carbon tetrachloride, chloroform, and other volatile bodies have been used for this purpose. These solvents, in passing through a layer of flowers or materials, dis- solve the odorous constituents, together with the plant resins, coloring matter, waxes and other substances present, which are soluble in the solvent utilized. By then distilling off the sol- 342 ELEMENTS OF INDUSTRIAL CHEMISTRY vent at a low temperature, usually in a partial vacuum, the odorous bodies, with the impurities mentioned, remain in the residue. As the yield from different flowers varies greatly, various quantities of wax, paraffine or some liquid odorless ester are usually added to reduce the cost and in order to market the different odors at the same price. Flower Concretes and " Absolutes." By this method the so-called " flower concretes " are made in southern France. This process has recently been improved again by eliminating from this concrete the alcohol insoluble portion. The concrete is treated with alcohol, thus extracting only the alcohol-soluble constituents and the alcohol distilled off, which gives a final product, marketed under various trade names, but usually called " absolute flower concrete " or " absolute flower essence." In another process, the waxes naturally present are precipitated, separated, and the solvent then evaporated in the usual manner. Other of these essences are obtained by washing the pomades and distilling off the alcohol. CONSTITUTION OF PERFUME AND FLAVORING MATERIALS. The complex nature of these has only been properly studied in recent years. As organic chemistry progressed and methods were found to identify and isolate from the natural materials various con- stituents present in them, it was found that almost without excep- tion every odorous material in nature is a compound. Quite frequently materials contain chemical substances or individual chemical bodies belonging to entirely different series and in no way related to each other. Some of these substances are ex- tremely sensitive to heat and chemical reagents, and therefore their isolation and identification present the greatest difficulties, but it is just this combination of different chemical individuals to which the fine odor of almost all flowers, plants, and other materials is due. As a rule, all of the definite chemical con- stituents, when used alone, give harsh odors. The delightful flowery aroma is only developed when they are present in proper combination, as they exist in nature, or as the skill of the chemist may combine them. This has led to commercial synthesis of the finer flower products. SYNTHESIS. The collaboration of thousands of chemists throughout the world, for some years past, has made a new industry possible, the industry of synthetic perfume and flavoring materials, which has come to the assistance of the manufacturer, ESSENTIAL OILS 343 by producing the same substances at a saying in cost, and by overcoming the frequent price fluctuations of the natural mate- rials, war conditions excepted. Many of the substances which naturally exist in the plants or materials may be manufactured chemically from other sources. Let us select one example, the jasmine flower, w T hich is so invaluable to the perfumer. If w T e submit the so-called " absolute jasmine-flower essence or con- crete " to a further process of purification, to eliminate the inodorous constituents present in it, we finally obtain a jasmine essence, which contains from 60 to 65 per cent of benzyl acetate. The absolute product containing this percentage, as made from the blossom, represents an actual expense of about $180 to $260 per pound, according to season. But we can obtain benzyl acetate chemically if we take toluene (methyl benzene), and treat it > with chlorine, we obtain benzyl chloride. If we now exchange the chlorine for the acetyl group, we get benzyl acetate, which, when highly purified, is identical with the product as it exists in the flower, and is marketed absolutely pure at about one hundredth the cost. This not only represents an enormous sav- ing in the industry, but makes it possible to use raw materials frequently for various purposes, where the natural product was not heretofore available, owing to its high cost. But while this syn- thetic benzyl acetate is absolutely the same definite chemical body as found in the flower oil, it is not jasmine. What we know as jasmine is nature's combination of many different constit- uents and we do not get what we call a jasmine odor until we produce each of these constituents and assemble them in the right proportion. By suitably changing the proportion of these constituents, we can obtain new odor effects, different shadings of the same flower odor. Flower oils are usually exceedingly complex. Often more than one hundred different chemical bodies must be produced and assembled to duplicate an odor known as " a simple flower odor " because each of these bodies is present in the plant and we cannot get the same odor effects unless we unite the same constituent bodies. NEW PERFUME MATERIALS. A great many chemical sub- stances have been found which have most delightful odors and flavors, and which, to our best knowledge at the present time, do not exist in nature as siich — at least, they have not been isolated from the natural materials. Many such substances are now commercially manufactured and have enriched the industry with a variety of new raw materials, which enables the manu- 344 ELEMENTS OF INDUSTRIAL CHEMISTRY facturer to produce entirely new effects. Many years ago, when the industry was in its infancy and purification processes had not developed to the present state of perfection, the synthetic materials were merely used for the purpose of diluting and cheapening the more expensive natural products, but this has wholly changed during the last few years. The synthetic materials of to-day are successfully utilized in goods of the highest grade, and many odor and flavor effects would be impossible without them. Chemical Constitution. Among the many chemical bodies which contribute their share to the odor or flavor of materials valued in the industry, we find representatives of both the aliphatic or fatty series and the aromatic or benzene series. The great majority consists of merely three elements, carbon, hydrogen, and oxygen. A smaller number of compounds, some of which are important, contain nitrogen — for instance, different varieties of artificial musk and amido bodies, derivatives of the benzoic acid series, like methyl anthranilate, one of the most valuable constituents of orange flower and many other flower oils, and the methyl ester of methyl anthranilic acid or dimethyl anthranilate, which, while present usually only in traces, contribute greatly to the flowery sweetness of many of nature's most valued blossoms. FIXATIVES. Some products which have but little odor are of value to the industry, because they are substances the perfumer calls "fixatives." In the plant, the perfume is produced con- tinuously in mere traces and is given off in infinitesimal quantities to the surrounding atmosphere. When we, however, isolate these bodies to which the odor is due, and have them in concen- trated form, their odor as given off is too intense and when we take a small amount of this concentrated material and allow it to evaporate, the odor will not last as long, because it will evapo- rate more quickly than in the plant and, furthermore, the odor being so concentrated and intense, will not be as sweet or as flowery. If we, however, use with the material various sub- stances known as fixative's, the odor is made less volatile. The perfume is only given off in small quantities at a time and we therefore duplicate the conditions existing in nature. In former times, ambergris, musk, and some of the resins were extensively used as fixatives, but most of these substances either had such a powerful odor, color, or sticky qualities (resins), that they could not always be used in sufficient proportion entirely to satisfy. ESSENTIAL OILS 345 Modern organic chemistry has given us a number of sub- stances, which, while practically of no odor value themselves, are very valuable in combination, because they not only serve as fixatives — that is, make odors with which they are mixed less volatile, but in many instances have the tendency to sweeten the odor. Among representative instances of this class we may men- tion methyl anisate, benzyl benzoate, benzyl cinnamate, and benzyl-iso-eugenol, which have but little odor. Then we have a group of very useful materials which combine a delightful odor with valuable fixative properties, as the many varieties of artifi- cial musk, phenylethyl phenylacetate, which has a charming rose-like fragrance, the various moss odors as Mousse de Chene, Mousse de Perse, Mousse d'Orient, and many other products valuable as fixatives wherever their odor harmonizes with the other constituents utilized. MUSK. Musk is perhaps one of the oldest perfume materials in existence and consists of the dried secretion of the preputial follicles of the male musk deer. This animal has been hunted so excessively that it has become practically extinct and it is now found only in the portion of Asia where the Himalaya Moun- tains rise to elevations of 8000 to 12,000 ft. Occasionally the animal may wander into lower altitudes, but the greater part of the annual production comes from the Himalaya region. In Siberia we find musk deer, allied in family, but the musk secreted by them is not valued as highly in commerce and does not have as powerful an odor. The musk pods are purchased by native dealers, carried by caravans to the seashore and marketed from Chinese seaports. Commercially the product is known as either Nepaul or Tonquin musk and is now valued at from $20 to $25 an ounce. It is becoming scarcer each year, and the time is not far distant when the musk deer will be extinct, because each musk pod means that a male musk deer has been killed. Of course adulterations are plentiful. The Chinese have excelled in this, and have for many years past sold so-called artificial musk, w r hich is a mixture of dried blood and various other substances, hard to identify, with just a trace of natural musk, marketed at prices ranging from $1 per ounce, upwards. The chemical substance to which musk ov/es its odor has never been definitely identified. Some research work of recent years seems to point to a ketone, which gives a powerful musk odor, but no chemical work of note has been done on the subject, owing to the high expense involved, and the exact chemical formula of the product 346 ELEMENTS OF INDUSTRIAL CHEMISTRY is still in doubt. Musk also contains a number of impurities, which rather detract from the true musk odor, but are always present in the natural article. SYNTHETIC MUSK. If we now turn to synthetic musk, we find that here we encounter a product differing entirely in chemical composition, imparting a musk odor, and of which many chemical derivatives have been made. The original musk marketed was a trinitro derivative of toluene, and later a trinitro derivative of xylene. Xylene, may be condensed with iso-butyl chloride, by means of aluminium chloride — that is by the well-known Friedel and Kraft reaction, to form iso-butyl -xylene. After careful puri- fication, this substance is nitrated in the usual way, by employing a mixture of sulphuric and nitric acids, and the final product is thoroughly purified by repeated crystallization. This gives us the artificial musk of commerce, trinitro-iso-butyl-xylene, C12H15O6N3, consisting of small, yellowish, needle-shaped crystals, having a peculiar musk odor. This artificial musk is utilized in many perfume compositions all over the world to-day, and while it has not the identical odor of natural musk it has replaced it in numerous instances in the soap and perfume industry. The success of these products encouraged scientific research, and as a result a number of other musk compounds have been made which have a stronger and sweeter odor. Among these we may mention musk ketone, also a nitro product, in which, however, the CO or ketone group is present. Ambrette musk and similar derivatives, made by other complicated 'chemical processes, have a more intense odor than any other artificial musk known and some of them have the advantage of being more soluble. CIVET. Civet is the secretion of the civet cat of Abyssinia, where the cat is kept for the purpose of producing a regular sup- ply. It is a substance somewhat similar to musk, but contains derivatives of indol, principally one of the methyl-indols, as active constituents. As brought into commerce, it is largely adulterated with fats and fatty substances, hairs, clay, etc. The substances present in natural civet, which give it fixative value, have been identified chemically and are produced syn- thetically. Civet materials are now available, both in liquid and crystal form, as well as the active principle to which the odor of civet is mainly due, namely, one of the methyl indols, C9H9N. AMBERGRIS. Ambergris is another product belonging to this series, and is supposed to be a decomposition product present ESSENTIAL OILS 347 in the intestines of unhealthy whales. Its use has largely de- creased in recent times, as synthetic substitutes have become available at a small fraction of the cost of the natural article, the supply of which is very irregular and uncertain. CASTOREUM. Castoreum is a product from the beaver, which has a similar odor to musk. It is now but seldom used. GUM BENZOIN. Of the fragrant gum resins known to the ancients, but few have survived. Gum benzoin is used in medicine to-day and forms a constituent of many toilet preparations. Sumatra gum benzoin has a dark brown color and is only fit for medicinal use — it should never be employed for perfumery purposes. The gum coming from Siam or Rangoon is the only variety suited for use in perfumery. It is practically colorless. Gum benzoin is chemically of interest, because from it benzoic acid was first isolated and it has given its name to the chemical benzene or benzol CeHo. Then we have gum olibanum or frank- incense, and myrrh — Arabian gums of sentimental, rather than practical, importance, although used in the manufacture of incense. STYRAX. Styrax from Asia Minor is another gum of decreas- ing importance, in which, however, important chemical bodies have been found — among them styrol previously mentioned, as well as cinnamic acid and cinnamic alcohol, both of which are of importance. BALSAM PERU. Balsam or gum Peru is improperly named, because all of it comes from the Republic of Salvador in Central America. This balsam is obtained by crude methods over a direct fire and has a rather smoky odor. It is too sticky to find application in perfumery and is employed in medicine. There is, however, the so-called oil of balsam Peru, which is separated from the balsam by chemical means, eliminating the resins, which has a very nice odor, although contaminated by the burned smoky smell, due to the phenolic constituents, which result from heating the balsam over direct fire. The product has been ana- lyzed repeatedly and synthetic reproductions are on the market, which are superior in odor to the natural. GUM LABDANUM. Then we have the old gum labdanum mentioned in some of the ancient works on perfumery, the black color and stickiness of which prevented its extended use. Chem- istry has enabled us to isolate from the gum the portion to which the real odor is due, which is now largely employed in the most modern creations and imparts all of the odor value and fixative value of the gum, without the color and stickiness. Labdanol 348 ELEMENTS OF INDUSTRIAL CHEMISTRY is indispensable in many high-grade bouquets, as it imparts a delicate softness to the odor and acts as a most excellent fixative as well. FLOWER PERFUME MATERIALS. These include our finest odors, perfumery products isolated from the flowers by means of either the enfleurage or maceration process, or synthetic repro- ductions of these materials. All of these products are exceedingly complex in character and owe their fine perfume to the proper blending of many distinct chemical bodies, produced in such lavish profusion in nature's laboratory. These materials form the most important group available for duplicating the delight- ful blossom fragrance, and include all blossom oils, concretes, " absolutes," pomades, and washings from same, and all the fine synthetic flower perfume oils. Many of the different flower odors contain a number of the same constituents, but in widely differing proportions and influenced by the odor of other bodies present. GERANIOL AND ClTRONELLOL. In the rose we find the ter- pene alcohols, geraniol and citronellol, present in large pro- portion. These are closely allied chemically. Geraniol has the formula CioHigO, and citronellol C10H20O. Citronellol has not been found alone, but is usually accompanied by geraniol. As the commercial separation of these two alcohols is only possible by destroying the greater part of the geraniol present, the use of citronellol alone, which does not exist by itself in the flower anyway, is not advantageous. Under the name of rodinol, or rhodinol, a mixture of geraniol, citronellol, and isomeric alcohols is marketed, containing the proportion of allied alcohols present in roses. It has a very sweet rose-like odor when perfectly pure and is used in quantities. Citronellol is also produced artificially from the allied aldehyde, but this product lacks that soft sweetness which is the characteristic of rodinol. The esters' of geraniol and rodinol are likewise of importance, the acetates, formates, and propionates having a very sweet flowery odor. Rose Oil and Rose-flower Products. Turkish otto is one of the highly prized perfumery products used throughout the world. Turkey does not produce even a small proportion of the crop; almost all of it comes from Bulgaria; of late Asia Minor and Persia also produce a limited quantity. As previously mentioned the oil consists largely of geraniol, citronellol, and allied alcohols with a small proportion of their esters, as well as about 20 per cent of an entirely odorless, waxy hydrocarbon ESSENTIAL OILS 349 belonging to the parafnne series. Much of the oil is impure. The official figures show the importation into Bulgaria of quan- tities of products that may be used as adulterants for oil of rose and the export of a great deal more rose oil than the statistics show has been produced. The rose-flower products have a much finer perfume than the distilled oil, or otto, and are available in many modifications. Rosa centifolia is used for manufacturing rose concretes, pomades, and absolutes. The blossom oil con- tains up to 80 per cent of alcohols, principally phenylethyl alcohol, which is almost entirely absent in the steam-distilled otto, as it passes into the rose water. Oils imparting the odor of the tea rose, red rose, moss rose, white rose, and other varieties, are available. All of these members of the rose family contain other constituents in varying proportions, hence in order to duplicate their odor we must utilize many different chemical bodies. PATCHOULY OIL. The patchouly plant is principally ob- tained from the Straits Settlements and Java, where it has been cultivated so long that it has almost wholly lost the habit of flowering. The oil, which is distilled from the leaves, increases in value on aging. By chemical methods the oil may be purified and the undesirable constituents which have a moldy, disagreeable odor, removed. The resulting products can be used without hesitation in the finest perfume combinations, but only in small proportion. If employed in too large a quantity the effect will not be agreeable. Orange-flower and Neroli Products. One of the oils which owes much of its odor value to esters of linalool is the oil of neroli, distilled from orange blossoms. Neroli oil, being made by steam distillation, does not represent the entire odor value of the flowers, but having become a commercial product many } T ears ago, is esteemed by manufacturers of cologne, and is also used as a flavor to a limited extent. " Orange-flower water " is obtained as a by-product, and contains the saponified portion of some of the constituents present in the blossom. It may be had at a fair price, considering the fact that the pur- chaser must pay for the transportation of distilled water from Europe. A number of different varieties of neroli are known, neroli petale being the finest grade, neroli bigarade coming next in quality, after which there are various inferior grades, ending with the so-called oil of petitgrain. This is imported from South America, where it is distilled by crude native methods from twigs, 350 ELEMENTS OF INDUSTEIAL CHEMISTEY leaves, unripe fruit, as well as flowers of the wild orange trees, which have spread from those planted there when Spanish friars controlled that quarter of the world. Oil of petitgrain is fre- quently used to dilute the more valuable neroli oils. Orange- flower products made by enfleurage or synthesis differ greatly in composition from distilled neroli oils as they represent all the blossom constituents. The flower oils therefore have a much sweeter and finer perfume than neroli oils and are indispensable in fine perfumery. JASMINE-FLOWER PRODUCTS. The jasmine odor is one of the most useful perfumery raw materials, indispensable in many bouquets, as it imparts great freshness and delightful odor effects. Jasmine-blossom oil contains principally the benzyl esters of acetic, formic, and propionic acids, linalool and its esters, methyl anthranilate, benzyl alcohol, geraniol, paracresol, a ketone jasmon and traces of a number of other constituents. Cape jasmine or gardenia oil belongs to the same odor class, but is less fleeting and has a more intense sweetness. YLANG YLANG OIL. Ylang ylang oil has long been one of the most valuable products of the Philippines. The distilled oil is a very complex body which differs somewhat from year to year and according to the method of production. In fact, ylang and cananga, a cheaper oil, are derived from the same tree. The best ylang ylang oil consists of the first portion of the steam distillate. It contains a larger proportion of esters. Cananga oil represents the less valuable fractions, forming the second por- tion of the distillate. Its odor is not nearly as sweet and its value is often less than 10 per cent of ylang oil. It contains benzyl alcohol, benzyl acetate, benzyl formate, benzyl benzoate, benzyl salicylate, methyl anthranilate, methyl benzoate, methyl salicylate, geraniol, geraniol acetate, linalool, linalyl acetate, eugenol, iso-eugenol, methyl eugenol, methyl iso-eugenol. This list, while long, is by no means complete, as a number of allied bodies, especially other esters, are also present. Even all these together will not give the right odor, until the characteristic constituent is added which converts the product into ylang ylang. This body is the methyl ether of para-cresol, which is enormously powerful and therefore must be used with great care. Traces of para-cresol itself and of guaiacol ethers are also present in the oil. CUMARINE. Cumarine C 6 H 4 (0)CHCHCO is the active ESSENTIAL OILS 351 principle of tonka beans and is also widely distributed in nature. It is found in quantities in the herb known as deer tongue and in small proportions is present in hay. The odor of new-mown hay in the fields is due partially to this substance. From the chemical standpoint, cumarine is interesting, because it can be made from carbolic acid or phenol. Phenol, by treatment with alkalies and chloroform may be readily converted into a mixture of two aldehydes. Ortho-oxy-benzaldehyde b is usually formed in the larger proportion and may be readily converted into cumarine by the well-known Perkin reaction, by condensing this aldehyde with acetic anhydride and anhydrous sodium acetate. After proper purification, the chemical so prepared cannot be distinguished from a properly purified cumarine obtained either from deer tongue or from the tonka bean. Purification is of prime importance because the slightest odor of the parent material, or of one of the reagents, adhering to the finished product will entirely spoil it. Cumarine is largely used in making cheap flavors, also in perfumery and in scenting soaps. Some of its chemical derivatives, the manufacture of which is more complicated, are even more valuable. HAWTHORN, AUBEPINE, NEW-MOWN HAY OILS. Para-oxy- benzaldehyde is the other aldehyde formed in smaller proportion in the reaction just mentioned. While a nearly odorless solid it can readily be transformed into the methyl derivative, an oil of powerful odor, recalling hawthorn blossoms and known as aubepine, CeH^OCH^CHO. New-mown hay perfume oils con- tain several derivatives of the constituents just discussed and should be mentioned here, as they are so valuable as sweeteners, in many perfume formulas. BIRCH OIL. Birch oil is almost entirely composed of the methyl ester of ortho-oxy-benzoic acid or salicylic acid. This is also the main constituent of value in oil of wintergreen. For this reason the U. S. Pharmacopoeia has recognized artificial methyl salicylate, made by condensing salicylic acid, and methyl or wood-alcohol. For flavoring, methyl salicylate is much inferior to ethyl salicylate, which also exists in many natural oils, as the ethyl ester gives not only a sweeter, but more lasting flavor. WINTERGREEN OIL. Oil of wintergreen represents one of the exceptions among essential oils, as it consists of practically one constituent to which the odor and flavor value is due. Almost all others are much more complex in character. Methyl sali- cylate, mixed with a little ethyl salicylate, and a trace of the 352 ELEMENTS OF INDUSTRIAL CHEMISTEY methyl ester of methyl salicylic acid, can scarcely be distinguished in flavor from the natural oil. It is not surprising, therefore, that these natural oils are so largely adulterated, for while the synthetic oils are legitimate articles of commerce, they should not be supplied where the natural product is ordered, as this is much higher in value, due to the cost of production. CAMPHOR AND SAFROL. Camphor Ci Hi 6 O is a body which, while not an essential oil, is very important, not only on account of its medicinal value, but because it is the parent sub- stance of many other chemical bodies. Japan has controlled its production, but it has also been made by synthesis, and arti- ficial camphor is now on the market. Camphor is obtained commercially by distilling with steam the wood of the camphor tree. Recently, the discovery has been made by the U. S. Depart- ment of Agriculture Experiment Stations, that small plants, just started from the seed, can be mown and distilled with a very good yield of camphor. Camphor is a solid which crystallizes from camphor oil on chilling. The crude product is imported from Japan and refined in the United States. Camphor oil, the liquid portion, is very complex, and is one of the sources of safrol, which is used commercially in medicine as artificial oil of sassa- fras, of which this is the principal constituent. SASSAFRAS OIL. As stated above, safrol C10H10O2 is the main constituent of this oil, of which it forms 80 per cent, the balance consisting of 7 per cent camphor and terpenes. It finds employ- ment in medicine and for scenting laundry soaps. Heliotropine and Heliotrope-flower Oils. Safrol is also used chemically. By oxidation it yields heliotropine or piperonylic aldehyde, CeH3(OCH20)CHO, the methylene deriv- ative of protocatechuic aldehyde. This substance has the odor of heliotrope and is one of the constituents to which the flower oil owes its perfume. Alone, however, it lacks strength and character and must be reinforced with other bodies present in the blossom. Heliotropine crystals have proven valuable as an addition for sweetening soap perfumes and for other technical applications. Heliotrope-blossom oils are among the most useful products available for perfumery, as they are much used for sweetening many other flower odors. BITTER ALMOND OIL AND BENZALDEHYDE. The essential oil of bitter almond is an illustration of the futility of the classi- fication of essential oils according to their botanical origin. The almond tree is a member of the great rose family, resembling our ESSENTIAL OILS 353 peach. There is no difference between the bitter and the sweet almond trees, and the fruits of both contain a considerable amount of fatty oil, which is also utilized in medicine as " oil of sweet almonds." A similar oil may be found in the apricot and peach fruit, but in addition, these two and the bitter almond kernel contain a body called " amygdalin," which is a combi- nation of glucose, hydrocyanic acid and benzoic aldehyde, and this breaks down into these bodies when acted upon by a fer- ment, called emulsin, which is also present in the fruit or seed, or by other hydrolizing agents. After the emulsin has acted, direct steam is applied, and a very old process in vogue among the alchemists, and named by them " cohobation," is employed. The water which has been distilled off is returned to the still after separating the oil, by which means the total amount of water used is kept down to a minimum and a much larger quantity of oil is recovered. The hydrocyanic acid must be removed from oils intended for flavoring, because it is highly poisonous, and during this and the previous handling care must be taken to prevent, as far as possible, the rapid oxidation of the principal constituent, benzaldehyde, to benzoic acid. The oil of bitter almond, deprived of prussic acid, is com- mercially known as oil of bitter almond, S. P. A. (without prussic acid). The natural oil containing the acid is very poisonous and must never be employed, excepting for medicinal purposes, when the prescribing physician specially desires its medicinal effects. ANISE OIL. Anise oil is easily obtained, as it is only necessary to steam-distil the seed until the residue is free enough fro n oil to be used as cattle food. The resulting anise oil is quite com- plex in composition, the main constituent being anethol C10H12O, the methyl ether of para-propenyl-phenol, and with it is associ- ated the corresponding allyl compound known as iso-anethol, methyl chavicol, or estragol C10H12O. These bodies are also found in almost the same proportion in an entirely different oil from a botanical standpoint, because anise is a member of the L^mbelliferous family, to which carrots and parsnips belong, while the star anise is distilled in China from the fruit of an ilex tree, which is related to magnolia, and yields an oil which can scarcely be distinguished by chemical test from true anise oil. Star anise oil is usually produced in the crudest ways by natives and is sold at a much lower price. The oil is used in medicine and some- times as a flavor. 354 ELEMENTS OF INDUSTRIAL CHEMISTRY BAY OIL. Bay oil is in no way related to the bays or laurels of classical times, but is distilled from leaves of trees native to the West Indies, belonging to the Pimenfca or Myrcia family. At early date these sweet leaves were soaked in rum, and the well- known bay-rum was the result. It was later found that an oil obtained by steam distillation could be added to alcohol, and a very similar product obtained. The oil contains eugenol and methyl eugenol as its principal constituents. It also contains chavicol C6H4(OH)C3H5, and its methyl ether, which has been mentioned previously as present in anise oil, and a little citral, which we shall consider later. In addition there are a number of terpenes, which are bodies that have only recently been inves- tigated and about which we shall have much to learn before we can understand them. They are present in many oils in consider- able proportion and in traces in nearly all essential oils that are distilled. They are a disadvantage in practically every instance, as they take up oxygen from the air, thicken the oils, give rise to unpleasant odors and have but little odor value themselves. Many of the natural oils contain a large proportion of terpenes, and therefore a purified product which eliminates these is highly to be preferred in manufacturing, because the purified oil is more soluble, has the odor of the plant or fruit in a higher degree, and is more concentrated. CITRUS OILS. The oils of the Citrus family, which include bergamot, lemon, lime, orange and bitter orange, are made com- mercially principally in southern Italy and Sicily. (Oil of orange is also made in Jamaica.) All are obtained by expression and not by distillation. BERGAMOT OIL. Oil of bergamot owes its odor principally to the esters present, consisting of linalyl acetate and allied compounds. The commercial oil usually contains from 30 to 40 per cent of ester and is valued according to ester content. It has been largely adulterated, especially since the price has risen during the last few years, and should be purchased from reliable sources. Synthetic products are available, which duplicate the odor at considerably less < cost. LEMON OIL. Lemon oil consists principally (over 90 per cent) of terpenes, which have no flavor or odor value, but which hasten the rapid oxidation of the oil, so that lemon oil will not keep very long and changes into turpentine-like-smelling deriva- tives, which are useless for technical application. The active principles of lemon oil consist of about 8 per cent, the main con- ESSENTIAL OILS 355 stituent being citral, the aldehyde of geraniol, which we shall further consider under geranium oil. Citral is usually isolated from lemongrass oil, in which it is present in far larger proportion, ranging from 60 to 80 per cent, according to quality. Lemon- grass oil contains, however, other constituents that have a dis- agreeable odor. Citral alone, even when pure, does not produce a fresh lemon flavor. It is well known that other substances are present in small proportion, for instance, small amounts of linalyl acetate, methyl anthranilate, and a number of other compounds. Lemon oil is used mainly as a flavor. Where a lemon "perfume is wanted, as in soaps, citral may be used to much better advan- tage at a large saving in cost. ORANGE OIL. The oils of bitter and mandarin oranges and limes are made on a small scale, but the oil of sweet orange has found extended application in flavors and perfumery for many years. Oil of sweet orange contains a larger proportion of terpenes, which are useless from the odor and flavor standpoint, than any of the other oils of the Citrus family. In fact, it is estimated that less than one-twentieth of the weight of the commercial oil of orange consists of the active odor or flavor- bearing portion — among these decoic aldehyde has been identi- fied as one of the constituents that contributes the main flavor, but many other items are present. GRASS OILS. From the citrus oils we pass to the East- Indian oils of the Citronella family, which include a number of aromatic grasses. They are known by various names, and while closely related botanically, produce oils of entirely different odor-effects when distilled. They include the oils of citronella, palma rosa, or East-Indian geranium, gingergrass, lemongrass and vetiver. Hundreds of tons of these grasses are distilled annually by the natives in India. CITRONELLA OIL. Oil of citronella is mostly used for technical applications and for perfuming laundry soaps. Chemically, it is a source of the important terpene alcohol, geraniol, a con- stituent of rose oil. It also contains an aldehyde, citronellol CioHigO, closely related chemically to citral, the aldehyde of lemon oil, which serves as a raw material for building up other materials by synthesis. PALMA-ROSA OIL. Oil of palma-rosa, or East-Indian gera- nium oil, is likewise of importance, as it contains a large propor- tion of geraniol, which is isolated from the oil chemically and finds extended application. The oil itself is used as a soap per- 356 ELEMENTS OF INDUSTRIAL CHEMISTRY fume. Oil of gingergrass, so called up to recent times, was thought to be an adulterated palma-rosa oil, but has been proven to be a distinct essential oil, distilled from a different species of grass. It finds application principally in scenting soaps. VETIVER OIL. This oil, also known as cus-cus, kusa or kus, is one of the oldest known perfume odors, and still enjoys great popularity. It is distilled from the root of Andropogon muri- catus or squarrosus, an East-Indian grass. The oil made in India is usually distilled with sandalwood, but the root is exported and worked up principally in European factories. The yield of oil ranges from 0.45 to 0.92 per cent. The Reunion oil is much inferior in odor and has a different chemical composition. Even the best oil contains some constituents having a disagreeable odor, furfural, diacetyl, etc. It is purified chemically and may then be used in perfumes of the highest grade. When employed in very small proportions it gives a most charming perfume effect and the fine character of many modern popular odors of the Oriental type is due to this constituent. LEMONGRASS OIL. Oil of lemongrass is of great value, because this contains, as previously mentioned, a large propor- tion of citral CioHieO. Citral is not only one of the active principles of oil of lemon to which the main flavor is due, but may be chemically converted into other derivatives which are of much greater value in perfumery. Citral may be condensed with acetone, by any alkaline-condensing agent, forming a ketone derivative known chemically as pseudo-ionone, which by treat- ment with acids is converted into ionone. Many isomeric sub- stances are produced commercially and find extended application. IONONE. Ionone C13H20O is a direct derivative of the benzene series. The acid treatment converts the chain formula of the aliphatic series into an aromatic derivative by closing the chain into a benzene ring. Ionone exists in a number of isomeric forms, each of which has a slightly different odor. Many deriva- tives of ionone have been made. The name " ionone " having been trade-marked at the time the original patent (now expired) was applied for, in 1893, these violet ketones are marketed under various trade names, as iovionol, neoviolone, ional and many others. This has caused some confusion, as different products are marketed under the same name. For instance, iralol has been used erroneously for ionone, but properly refers to methyl ionone, a constituent of artificial orris oil. The conversion of pseudo-ionone by means of acid gives rise to many impurities ESSENTIAL OILS 357 having a disagreeable odor. Consequently these ketones are on the market in all possible qualities, from those which are almost useless, on account of imperfect purification, to products which have a charming floral odor and are applicable for the finest perfumery purposes. Ionone is an isomer of irone, the active principle of the essential oil of orris root. ORRIS OIL. Orris root, or the iris of Italy, when distilled, yields an essential oil containing about 90 per cent of myristic acid and about 10 per cent of active perfume substances of which irone C13H20O is the main constituent. An absolute orris oil free from the fatty acid is also sold, being from 8 to 10 times as strong. Methyl iovionol or iralol C14H22O is a basic ketone having a very sweet and powerful orris odor. Other synthetic orris products are available which even duplicate the valuable fixing properties of the root and are entirely free from the odor- less myristic acid found in the natural oil. VIOLET ODORS. Ionone, as well as irone, popularly repre- sents the violet odor, but as a matter of fact many other sub- stances contribute to the violet perfume. The manufacturer who thinks he can get a violet by merely dissolving a basic ketone like ionone, iovionol, iralol, irone or orris oil in alcohol is doomed to disappointment, because the other substances are missing which contribute the life-like character and really produce the complex odor-effect which the public knows as violet. CASSIE OR ACACIA ODORS. These blossom oils belong to the violet series, but contain as added constituents the methyl esters of salicylic and methyl salicylic acids, methyl-eugenol and other bodies. Both natural and synthetic blossom products are available, which are used extensively and have a most delightful flower perfume. Mimosa also belongs to the cassie type perfumes. SANDALWOOD OIL. Oil of sandalwood has been known for many years and has always been highly esteemed in the Orient. Sandalwood itself is an ancient constituent of incense, and the trade in this rare w T ood is so valuable that it has been monopolized by the Indian government, auction sales being held at regular periods, under supervision of East-Indian officers. But little of the wood is distilled in the Indies; the greater part is exported to Europe and America, where the oil is produced by modern methods. The principal portion of the oil is known as santalol, a rather complex chemical substance which is both alcoholic and aldehydic in nature and consists of a number of distinct chemical individuals. 358 ELEMENTS OF INDUSTRIAL CHEMISTRY SANTALOL. Santalol is much more valuable to the perfumer than sandalwood oil because it represents only the useful por- tion of the oil, as the ill-smelling constituents have been removed. From some of the fractions of sandalwood oil, the writer suc- ceeded in isolating portions which have odors almost identical with certain fractions obtained from oil of patchouly, showing that these oils, produced in the same climate by a tree and herb which have no botanical relation, contain similar compounds. CEDAR OIL. The cedar-like odor of oil of sandalwood ,has often led to its adulteration with oil of cedar, which is much cheaper and may be had in unlimited quantities. Much cedar- wood oil is distilled from the sawdust or shavings produced in manufacturing lead pencils. A finer grade finds a limited market, being used in microscopical work. JUNIPER OIL. Cedar is a member of the Juniper family. Juniper berries and their oil have long been used for making gin and for flavoring. The berries have also a historical interest, since in some sections of Central Europe the custom prevails, when a death occurs in a house, of roasting the berries in a red- hot pan, so as to have the odor diffused throughout the rooms. Apparently this is a tradition which has been handed down from pagan times, since juniper berries formed part of the sacri- ficial offerings of the early Teutons. TURPENTINE OIL. Juniper oil contains a considerable proportion of terpene, and this brings us to the field of turpentine and allied products. Turpentine is a widely used solvent and is becoming scarcer each year, so that lately even the old stumps have been utilized to produce a cheap grade. While not a per- fume material, the oil is certainly an essential oil and it also serves as a source for some constituents of our most valued flower odors. TERPINEOL AND DERIVATIVES. Turpentine may be hydrated, forming terpene hydrate, which in turn, by treatment with acids, may be converted into terpineol. This is a terpene alcohol which exists in many of the finest flower oils, though in numerous modi- fications, widely varying- in physical properties, opcical rotation, boiling-point and melting-point and differing just as widely in odor. The common terpineol, much used as a soap scent, is a sirupy oil looking like glycerine. Purified products are also marketed and are invaluable in fine perfumery. (Terpineol Blanc, Muguet, Muguet Blanc, Muguet Ideal, etc.) Isomeric modifications of terpineol are present in lilac, tuberose, mimosa, ESSENTIAL OILS 359 ylang ylang, lily of the valley, and many other exquisite flower oils. LILAC-FLOWER OILS. Terpineol bears the same relation to these very popular blossom oils as geraniol to oil of rose. Lilac flowers contain many of the other chemical constituents we have already described. Lilac-flower products are obtainable in many shadings of this odor suitable for many different purposes. The so-called French lilac is merely a variation combining lilac and hyacinth odors. EUCALYPTUS OILS. In Australia we find various members of the Eucalyptus family. They yield oils differing very much in chemical composition and odor, and the exact species of tree from which the oil was obtained should always be mentioned. The ordinary commercial eucalyptus oil owes its medicinal effect principally , to a body chemically known as eucalyptol or cineol CioHisO. Eucalyptol is widely distributed throughout the essential oils in small proportion, but when present in large proportion, as in eucalyptus oil, or when concentrated, it has a disagreeable taste and odor. Consequently its use has de- creased considerably in recent years, as other medicinal bodies have been found which are not as unpleasant. PELARGONIUM OR GERANIUM OIL. Oil of pelargonium is one of the more modern oils and is of considerable commercial importance, as it contains about 70 per cent of terpene alcohols, that is, both geraniol and citronellol, in varying proportions, according to the source. It shows that the same plant will yield other chemical substances w T hen grown in different soils or climates. A number of varieties of pelargonium or geranium are distilled in Algeria and throughout northern Africa, as well as in some of tne French islands, especially Reunion, and to a limited extent in southern France. The plant is common with us as a house-plant, and is known as " rose geranium." The oil is used in perfumery and soap-making, and also serves as the source of the valuable terpene alcohols, which may either be isolated and used as such or changed by synthesis into derivatives having a muctThigher perfume value. The so-called Turkish or East- Indian geranium oil should not be confused with these pelar- gonium oils, as it is distilled in the East Indies from one of the grasses. See under palma-rosa oil. LAVENDER OIL. Oil of lavender is distilled from a member of the mint family, and while quantities are produced in England, the bulk of the product comes from southern France. French 360 ELEMENTS OF INDUSTRIAL CHEMISTRY lavender oil is commonly valued by the ester content, estimating the mixture of esters as linalyl acetate. The so-called Mitcham or English lavender oil contains less ester, but other constituents are present in small proportion which give a different perfume effect. The English oil commands a higher price. This is again an instance where the proportion of one constituent does not de- termine the value of a perfumery product. It is the quality of the constituents present that influences the value of the oil. Synthetic products are also marketed which impart a similar perfume to the English oil. CLOVE OIL. Cloves, one of the earliest items of trade be- tween the East and West, contain such a large proportion of oil that even the crudest methods give a fair yield. Cloves are the dried, unopened flower-buds of a beautiful evergreen tree. Clove oil is the commercial source of eugenol, which chemically is allyl- methoxy-oxy-benzene C10H12O2. This is present in the com- mercial oil to the extent of from 70 to 85 per cent. The other constituents are of no commercial importance. Eugenol may be obtained from clove oil by combining it with an alkali, removing the terpenes, setting free the eugenol, and vacuum, distilling. Its specific gravity increases on aging, owing to the formation of resinous or condensation products. Consequently, a perfectly pure material, when freshly distilled, will have a slightly lower specific gravity. By treatment with alkalies, eugenol may be converted into iso-eugenol, which on oxidation yields vanilline. VANILLINE. Chemically, vanilline C 6 H 3 (OH) (OCH 3 )CHO is the methyl ether of protocatechuic aldehyde and forms one of the main flavoring constituents present in vanilla beans. Vanil- line alone, however, will not duplicate the entire flavor of vanilla, as it merely represents one of the constituents of the bean flavor. Vanilla beans contain in addition to vanilline other substances to which the fine flavor of the beans is principally due. Popularly, and quite erroneously, it has been thought that the resinous substances which are present contribute to the flavor. As a matter of fact, the resinous bodies in the bean, when separated, tenaciously hold a small proportion of the active principles, but when perfectly pure, these resins have practically no odor or flavor- ing value. Synthetic materials are available, however, which duplicate the entire flavor of the finest beans and are free from resins or tannins which contaminate the natural bean flavor. Allspice Oil (or Pimento). Another oil which contains a considerable proportion of eugenol (65 per cent) is the oil of ESSENTIAL OILS 361 allspice or pimento, official in the U. S. Pharmacopoeia. It is used principally for flavoring. Most of the spices, herbs and other condiments utilized owe their flavoring value to essential oils. HERB AND SPICE OILS. Among these, we may mention the oils of mace, nutmeg, caraway, celery, coriander, cumin, fennel, ginger, marjoram, parsley, sage, thyme, and pepper, all of which are more or less complex in composition. Space does not allow their discussion in detail. CASSIA OIL. Another spice oil of importance is oil of cassia, improperly called in the U. S. Pharmacopoeia, VIII revision, oil of cinnamon. Oil of cassia owes its main value to cinnamic aldehyde CeHsCHiCH.CHO, which is present to the extent of about 80 per cent. This aldehyde is also produced by synthesis by condensing benzaldehyde with acetic aldehyde. CINNAMON OIL. Ceylon cinnamon oil is worth about four to five times as much as oil of cassia. It has a finer odor than cassia, and while the content of cinnamic aldehyde is lower, ranging from 65 to 70 per cent, other constituents are present which influence the odor considerably. For this reason Chinese cassia oil and Ceylon cinnamon oil should not be confused or called by the same name. The odor of cassie also should not be confused with cassia. Cassie is a member of the acacia and mimosa family and belongs to the violet group of odors. See Blossom Oils. PEPPERMINT OIL. While speaking of the aromatic oils used as condiments or for flavoring, we must not overlook pepper- mint, which is produced so extensively in America. Oil of peppermint owes its chief value to menthol, an alcohol, having the formula C10H19OH, and some of the esters of menthol, prin- cipally menthol acetate. Japanese oil of peppermint is also mar- keted, though often part of the menthol has been previously re- moved from it. CHAPTER XVIII RESINS, OLEO-RESINS, GUM-RESINS AND GUMS SOURCE. These products are all derived from exudations of plants and as a rule are oxygenated bodies. When mixed with certain percentages of the natural essential oil accompanying them, they are known as oleo-resins or balsams. If mixed with mucilaginous matter they are harder and known as gum-resins. Gums are amorphous bodies which are either soluble in or gelatin- ize with water, but are insoluble in alcohol. True resins are distinguished from gums in that they are all insoluble in water, free from odor or taste, form compact masses, and are usually of an aldehydic or acid nature. Fossil resins are found in the earth, usually in the form of irregular lumps, and often contain perfect specimens of fossil insects and leaves. AMBER. Amber is a fossil resin occurring as small masses in alluvial deposits in various parts of the world. According to Goefert, it represents the resinous exudation from about fifty different kinds of coniferous trees. It is found chiefly in Prussia along the shores of the Baltic, where it is thrown up by storms, or in some localities is even mined. Large deposits also occur in some of the lakes on the eastern coast of Courland. Small deposits have been found in New Jersey and Maryland, but not of sufficient magnitude to be of commercial importance. The largest single mass of amber ever reported weighed thirteen pounds. It is usually associated with lignite and often contains the fossil remains of insects and vegetation. Amber is a brittle solid, permanent in the air, and is suscepti- ble to a very high polish. By application of friction it becomes negatively electrified. Its color is usually from light to deep brownish yellow, although it sometimes possesses a reddish brown or bluish color. It is tasteless and odorless when cold, but gives off a peculiar aromatic odor when heated. It is generally translucent, though sometimes transparent or opaque. It is scarcely acted upon by water or alcohol. When heated in the air, it softens and finally melts at 286° C, which property makes it 362 EESIN8, OLEO-RESINS, GUM-RESINS AND GUMS 363 of value in the manufacture of varnish. When subjected to distillation several products result, among them being succinic acid, esters, and oil of amber. Amber is used in making high- grade varnish and finds extensive application in the manufacture of tobacco pipe stems and articles used for ornamental purposes. ANIME. The substance known as gum anime is a resin supposed to be derived from the Hymencea courbaril, a leguminous tree of South America. The resin exudes from wounds in the bark and is also found under ground between the principal roots. It occurs in small, irregular pieces of a pale yellow color, sometimes being of a reddish cast. It softens in the mouth, and when in a powdery condition adheres to the fingers. It readily melts on being heated, giving off an agreeable odor. It consists of two resins, one being soluble in cold alcohol and the other insoluble, and a small amount of volatile oil. Anime was formerly used to quite an extent in the preparation of ointments and plasters, but at present is only employed as incense or in the manufacture of varnish. BURGUNDY PITCH. When incisions are made in the Nor- way Spruce a sap exudes which is collected in small troughs, or holes dug at the foot of the tree. It is purified by filtering through straw and allowed to harden, subsequently being boiled with water to remove the volatile oil. Colophony or Common Rosin. This product is obtained in the preparation of oil of turpentine from crude turpentine. The latter is an oleo-resin obtained as an induced exudation from the pine tree. The sticky viscid liquid or crude turpentine is sub- jected to steam distillation, whereby about 17 per cent of the vol- atile oil of turpentine passes over, leaving a resinous matter, or rosin, in the still. Many grades of rosin are found in the market, being distinguished by letters (W.W. — water white) to designate their purity. It is also quoted as virgin, yellow dip and hard. In its purest state rosin is beautifully clear, possessing a yellow color with an olive tinge. This is obtained from the first runnings after the tree is " boxed:' The greater part of the rosin, however, comes under the head of yellow dip, which is obtained by distil- lation of crude turpentine. The hard rosin is very dark in color and is obtained from the scrapings after the juice has become too thick to run into the box. Rosin is heavier than water, having a specific gravity of 1070 to 1.080; it is easily fusible, becoming soft at 100° C, m.elts to a liquid at 152.5° C, gives off bubbles of gas at 157.5° C. and 364 ELEMENTS OF INDUSTRIAL CHEMISTRY is decomposed at red heat. It is soluble in alcohol, ether, benzol, carbon disulphide, acetic acid, fixed or volatile oils, and in solutions of potassium or sodium hydroxide. When distilled in vacuo, rosin undergoes very little decomposition ; but if heated in a retort it yields gaseous liquid and solid decomposition products. That portion of the liquid distillate boiling below 360° C. is known as rosin spirits, resembling turpentine very closely, for which it is largely used as a substitute. The portion distilling above 360° C, known as rosin oil, is much heavier and darker than rosin spirit and must be purified before use. This purification is accom- plished by treatment with sulphuric acid, followed by lime water and then distillation. COPAL. This is a resinous substance derived from the exuda- tion of several varieties of trees indigenous to the East Indies and South America, as well as parts of Africa, the Philippine Islands and other places. The gum is sometimes taken directly from deposits on the tree or is found imbedded in the earth. That variety of copal .known in commerce as gum Zanzibar is found usually under the ground. Another variety with indented goose- flesh surface, known in the English market as anime, is dug from the earth. Copal varies in appearance and properties, depending upon the source from which it is derived. It appears in roundish, irregular, or flattish pieces, often with a rough indented surface, due to sand impressions while it was in a soft condition. In color it ranges from colorless to yellowish brown; it is more or less transparent, very hard, odorless, tasteless, and has a specific gravity of from 1.045 to 1.130. It is insoluble in alcohol, partly soluble in ether, and slightly soluble in oil of turpentine. When heated it melts, giving off gases to the amount of 15 to 20 per cent of its weight. Its properties are changed by this treatment so that it becomes more soluble in alcohol, ether, and oil of tur- pentine, which characteristic renders it, like other resins, suit- able for the preparation of varnish. DAMMAR. This is a resin which exudes in drops from a coniferous tree, Agathis loranthifolia, and is collected after it dries. It is soluble in essential oils, in benzol, and to a slight degree in alcohol and ether. Owing to its light color and ready solubility in turpentine it finds extensive application in the manu- facture of light-colored transparent varnishes. DRAGON'S BLOOD. This is a resinous substance obtained from the fruit of several species of small palms growing in Siam, RESINS, OLEO-RESINS, GUM-KESINS AND GUMS 365 the Molucca Islands, and other parts of the East Indies. An exudation appears on the surface of the ripe fruit, which is sepa- rated by rubbing, by shaking in a bag, by exposing to steam, or by decoction. The finest product results from the first two methods. It comes on the market in two forms: either as small oval drops (tear dragon's blood) covered with the leaves of the plant and connected in a row like beads; or in cylindrical sticks eighteen inches long and about half an inch in diameter, covered with palm leaves and bound with slender strips of cane. An inferior product, prepared by boiling the fruit in water, is in the form of flat circular cakes (cake dragon's blood) . Dragon's blood is odorless, tasteless, insoluble in water, but soluble in alcohol and ether, also soluble in the volatile and fixed oils, forming red solutions. Its principal use is in the coloring of varnish. , ELEMI. This resin is obtained by making incisions into the trees, through which the juice flows and concentrates on the bark. Elemi comes on the market either as soft (Manila elemi) or hard (Brazilian elemi) , being of various colors, from light yellow to greenish white. It is soluble in alcohol and other solvents, its chief use being to impart toughness to varnishes made from harder resins. GUAIACUM. This resin is the concrete juice of the tree Guaiacum sanctum, obtained by several different methods. The simplest method is that of spontaneous exudation, or by making incisions in the trunk. Another method is to saw the wood into blocks, boring holes in them longitudinally, placing one end of the block in the fire and collecting the melted resin, which flows out at the opposite end. The plan most commonly used, how- ever, is to boil the chips and sawdust with a solution of common salt, and skim off the substance which rises to the surface. Guaiac appears in the market as irregular lumps, often mixed with small fragments of bark and sand. The purest form comes in small lumps, " tears," which result from natural or induced exudation. KAURI. This is an amber-like resin, varying from light cream to brownish yellow in color. It is the result of exudation from the tree Agathis australis, and is dug in large quantities from the ground in New Zealand. It is used very extensively in varnish-making, and like copal must be first heated or " run " before it becomes soluble in oils. MASTIC. This is a resinous exudation from the Pistacia lentiscus, a tree cultivated in the Grecian Archipelago. Incisions 366 ELEMENTS OF INDUSTRIAL CHEMISTRY are made in the trunk and large branches, from which the juice on exuding either hardens on the bark in tears or drops to the ground, where it is caught on cloths. It is of a light yellow color and nearly odorless. It is soluble in alcohol up to about 90 per cent, and is used to quite an extent in the preparation of spirit varnish. SANDARAC. This resin resembles mastic very closely and comes on the market in the form of tears. It is more soluble in alcohol, however, and is employed largely in the preparation of transparent varnish. OLEO-RESINS. The most important members of this class of compounds are Benzoin, Peru, Tolu, and Storax. They are all mixtures of resins with essential oils, and consequently have a much softer consistency than the resins. They are used espe- cially in pharmacy, and having practically no industrial applica- tion will not be considered in detail in this chapter. GUM-RESINS. The more important members of this class are Ammoniacum, Asafoetida, Euphorbium, Galbanum, Gamboge, and Myrrh. They are mixtures of gums and resins, form emul- sions with water, and are all largely used in pharmacy, gamboge being also employed as an orange-red pigment. ACACIA. Both Gum Arabic and Gum Senegal are included under this head, as they are derived from plants of the acacia family usually found in Africa. It forms lumps of various size, with color ranging from white to reddish brown. It is soluble in both cold and hot water and is used in the preparation of emulsions, in thickening ink, in water-colors, textile printing, sizing cloth, and in the preparation of mucilage. AGAR-AGAR. This is also known as Bengal isinglass and Japan isinglass. It is derived from certain algae, from which it is obtained by boiling in water. It comes on the market as long white masses. It is used as a sizing for cloth and as a culture medium for bacteria. ICELAND MOSS AND IRISH MOSS. These are derived from a form of seaweed which on boiling with water produces a jelly, much used in the textile and leather industries as well as for edible purposes. TRAGACANTH. This is a gummy exudation from Astragalus gummifer. It is odorless, nearly tasteless, and of a very light yellowish to white color. It usually comes into the trade in a flaky condition. Placed in water, it absorbs a certain amount and swells up very much, forming a soft adhesive paste. If the RESINS, OLEO-EESINS, GUM-RESINS AND GUMS 367 paste is agitated with more water, it forms a uniform mixture, which, however, will settle out on standing, as only part of the gum goes into solution. It is largely used in calico-printing and for other purposes where an adhesive is required. SHELLAC. A distinction should be made between shellac and lac. Lac is derived from the Indian term for 100,000 and is significant of the myriad or swarm of insects taking part in its formation. It has been erroneously stated that lac is the dried exudation of a tree, caused by the sting of the lac insect, and is similar to rosin in its origin. As a matter of fact, it is the secre- tion of the lac insect, and is a product of the assimilation of the tree sap which the insect feeds upon, just as honey and beeswax are produced by the modification of the nectar of flowers by the bee. Shellac is so called because of its shell-like form, and bears the same relation to lac that flour bears to wheat. It is a manu- factured article, and may be manipulated and adulterated, whereas lac is the original resin as gathered from the trees, and cannot be sophisticated. Lac is found only in northeastern India and, to a small extent, in the adjacent sections of Assam and Burmah. The shipping point is Calcutta. The insect producing lac belongs to the scale family (tacchardia lacca), and in the larval form when hatched is about one-fortieth of an inch in length and of a red or orange color. It has six legs, but no wings, and is too small and weak to travel far. It crawls or drops to another twig in the vicinity, but thousands are unsuccessful, through their inability to find a favorable position or a suitable soft, sappy twig which they can pierce with their beaks. As soon as the insect comes to rest it immediately begins to suck up the sap like an animated siphon, and secretes a substance which soon dries around it in contact with the air. They take up positions adjoining one another so that as the cells surrounding the insects grow larger they eventually coalesce, forming an incrustation around the twigs several times as thick as the twigs themselves. The formation of the lac is undoubtedly designed as a protective coating to shield the insect from its many enemies. Monkeys, ants and squirrels feed on the sweet incrustation. Heavy rains, hail storms, droughts, and forest fires work at times serious injuries. About two and a half months after the period of swarming the male insect matures, and after pushing up the lower edge of its cell crawls out backwards. The female stays in place. The 368 ELEMENTS OF INDUSTRIAL CHEMISTRY female is provided with three tufts of filaments covered with a white powder. As the lac gathers around, these filaments act as tubes to supply air and to permit fertilization by the male, who then dies. The female lives about three and a half months longer, continuing to feed on the sap. For this reason the female cells are larger than the male cells, and may be recognized when a cross-section is made. About a thousand eggs are developed by each female, and by the time these eggs are hatched the mother has dried up, leaving only the skin. The new brood escape from the body of the parent by the air-ducts in the lac, and another life-cycle begins. There are two generations each year, the swarming taking place in July and December. Lac may be propagated by cutting off the swarming twigs and tying them to the branches of healthy trees. Stick-lac. The in crusted twigs are broken into short sections and constitute the stick-lac of commerce. The lac is gathered twice a year by the natives. It is brought to some central point, such as Mirzapore, where it is hand-picked and graded. The principal trees bearing lac are the Kusum and Palas, but some eighty-eight varieties of trees have been recognized as hosts for the lac insect. The kind of tree and the nature of the sap fed on, as well as climatic influences, are undoubtedly fac- tors in the value of the product. Almost nothing is known of the origin of the various varieties of stick-lac. Seed -lac or grain-lac is produced from stick-lac by crushing, washing, and drying. In this way the wood and a considerable part of the coloring matter is removed. Seed-lac consists of ruby- red or orange-colored grains about the size of wheat. Lac Dye. If the wash-water from the stick-lac is allowed to settle, lac dye deposits. Before the advent of the synthetic dyes large quantities of this material were shipped to Europe (1,544,480 lbs. in 1880), where it was used as a substitute for cochineal. The trade has now entirely disappeared and lac dye is only seen as a curiosity. Shellac. To make shellac the workman fills long, narrow bags with dry seed-lac, to which a certain quantity of orpiment, and sometimes rosin, is added. The bag is heated over a charcoal fire until the lac has fused and run through the cloth. By twist- ing the bag the molten lac is forced out and is scraped off with a metal hook. It is flattened out by stretching over a cylinder filled with hot water. It is then reheated, clasped between the feet and hands, and pulled out into a thin sheet of a light to dark RESINS, OLEO-RESINS, GUM-RESINS AND GUMS 369 orange color. In good grades any imperfections are flecked out of the sheet by the finger. The edges are broken off and retnelted in the better grades. The sheets are broken into flakes and packed for shipment. This is the form in which lac is commonly seen, and is the material for sale in the paint store. Caoutchouc or India Rubber. India rubber is the coagulated product obtained from the milky juice of a large number of trees, creepers and shrubs native of nearly all tropical countries, although the finest grades (Para rubber) come from South America. The juice is collected during the months of July, August, October and November. It is coagulated by exposure in thin layers to the smoke of burning palm nuts, or it is boiled with water, with dilute acid, salt water, with lye, or with alum. , As rubber comes on the market it is very impure, containing water, sand, fibers, wood and various other materials. These impurities are removed by a washing process which is carried out in strong machines built for the purpose, consisting of corru- gated rollers, which flatten the lumps into thin sheets, thus aiding in the washing process. The sheets thus obtained are dried very thoroughly by hanging in a warm room for several weeks. Chemical Properties. Commercial washed rubber has a resin content varying from 1 to 10 per cent and 15 per cent. These resins are soluble in boiling aceton. Volatile organic solvents, such as turpentine, carbon disulphicle, benzol and petroleum naphtha, cause a swelling of the rubber to a jelly-like mass. This becomes distinctly viscous on further dilution; in fact, Fol of Delft has endeavored by numerous experiments to show the relation between viscosity, resin content, and strength in crude rubber. The most important chemical property is without doubt the fact that rubber combines with sulphur in all proportions up to a product containing about 32 per cent of sulphur. This combination of rubber with sulphur is known in practice as " vul- canization." Physical Properties. The physical properties which give rubber its value as a material of commerce are: (1) Its pale color; (2) high tensile strength, high adhesion and cohesion values; (3) great elasticity; (4) pliability; (5) impermeability to water and gases; (6) enormous dielectric value; (7) the ability to " take up " powdered minerals and form with them a homogeneous mass; (8) low specific gravity. CHAPTER XIX VARNISH DEFINITION. Varnish is a liquid designed to form films to cover surfaces, which on exposure to the air hardens and forms a more or less transparent and glossy coating, which improves or better displays the surface to which it is attached and to some degree protects it from dirt and injury. CLASSES OF VARNISH. Varnishes may be divided into two classes : those which harden by evaporation of the solvent — such are spirit varnishes, and those which absorb oxygen from the air and by chemical changes are made into hard films; these are oleo-resinous varnishes, and constitute the largest, most impor- tant and varied kind, used for a great variety of purposes. SPIRIT VARNISH. Spirit varnishes consist of suitable solids dissolved in volatile solvents. The most important is shellac, which may be regarded as typical. It consists of shellac resin dissolved in alcohol, and when spread out in a film the alcohol evaporates, leaving the resin as a thin layer over the surface to which the varnish has been applied. It will be evident that the alcohol has served practically as a mechanical means of spreading the resin in a thin and uniform film. Its cost is to be added to that of the labor and the use and wear of utensils required in applying the varnish, as all that we have at the end of the work is the film of resin. SHELLAC VARNISH. Gum-shellac, as the shellac resin is called, is usually in thin elastic flakes of a yellow or reddish or brownish-yellow color. Put a gallon of alcohol in a clean earthen- ware jar of two gallons capacity; at the close of the day's work gently drop into this three or three and a half pounds of flake shellac, without the slightest avoidable agitation; cover and let stand until the next day. Then with a clean wooden rod stir it for a few minutes, and during the day stir it for a minute at a time once an hour or so, and before night it will be dissolved. That is, the resin will be dissolved ; but shellac naturally contains a little wax (4 per cent) which is insoluble and makes the solution 370 VARNISH 371 milky or muddy and opaque; the film is, however, transparent. Shellac may be bleached by dissolving it in an alkaline aqueous solvent and then treating it with chlorine; the shellac precipitates when the alkalinity is removed, and is white. This is dried and looks much like pieces of white candy; it cannot be dissolved in the manner described, as it is in lumps and sinks to the bottom; it is therefore dissolved by agitation, usually in a revolving barrel or churn; this is indeed the way orange shellac is made on a large scale. The latter is soluble in 85 per cent alcohol, though it is more satisfactory to use stronger; but w r hite shellac already con- tains some water and requires 95 per cent alcohol. INSOLUBLE SHELLAC. White shellac is liable to pass into a modified form insoluble in alcohol; this especially is likely to occur if heated above ordinary temperatures or if kept in a dry place too long. ( For some purposes it is desirable to get rid of the 5 to 10 per cent of water in white shellac before dissolving it; it is spread on trays in a drying room, but not heated very much; it is better to use artificially dried air at ordinary temperatures; in any case it must be dissolved as soon as possible. Shellac varnish dries by the evaporation of the solvent, and appears to dry almost immediately; but some of the liquid is retained for a time, and it is not practicable to apply many coats in rapid succession, or it will be found that the whole has a waxy character, persistent and troublesome. Varnish made with " denaturized " alcohol is especially slow to dry; commercial wood alcohol is much better. DAMAR VARNISH. Alcohol is not the only solvent used in making spirit varnishes. Damar varnish is damar resin dis- solved in spirit of turpentine, and dries by the evaporation of the latter. Both this and shellac are often adulterated with common rosin or colophony. Damar may be dissolved cold in a churn; some pulverize it before dissolving, or make it with the aid of heat, preferably in a steam-heated vessel. The varnish is a milky liquid, but may be cleared by filtration or otherwise. If made hot it can be cleared more easily. Five or six pounds of resin are dissolved in one gallon (7-J lbs.) of spirit of turpen- tine. The film is transparent and practically colorless. Mastic and Sandarac Varnish. Sandarac is another resin usually dissolved in spirit of turpentine; another is mastic; both are also mostly soluble in alcohol. Amyl and methyl alcohols are for some resins better solvents than ethyl alcohol; and acetone added to alcohol greatly increases its solvent power. 372 ELEMENTS OF INDUSTRIAL CHEMISTRY Petroleum benzine is very commonly added to turpentine to cheapen it; it has the advantage of evaporating more readily and perfectly, and some of the heavier grades are for many pur- poses equal and perhaps superior to turpentine. PYROXYLIN VARNISHES. Pyroxylin varnishes are a variety of spirit varnishes. The solid part is cellulose, rendered soluble by acting on it with nitric acid, making cellulose, nitrates of various compositions. The principal solvent is amyl acetate, which may be extended or diluted with various liquids, as benzol, which have no real solvent action on the pyroxylin, but do not inhibit the solvent action of the amyl acetate, differing in this respect from the action of water on alcohol. Pyroxylin films are somewhat hard and stiff, and may be made more flexible by adding a fixed oil, as castor, cotton or linseed, to the solution. LACQUER. Spirit varnishes are often called lacquers, and are sometimes colored by aniline or other dyestuffs. Both asphaltum and coal-tar pitch are soluble in turpentine and benzene, or coal-tar naphtha, and are used as spirit varnishes; but more often with the addition of oil. Rosin is almost always added to asphaltum, but not necessarily. OLEORESINOUS VARNISHES. The greater part of the varnish made is compounded of oil, resin, and spirit of turpentine, and is of great variety of composition and uses. Almost all the oil used is linseed. A little tung or Chinese wood-oil is used, but inconsiderable in amount as compared with linseed. This oil is usually subjected to some preliminary treatment. It is as pur- chased from the makers well settled and filtered and free from cloudiness. It may be remarked that a mere trace of water causes a cloud, and the not uncommon belief that oil must be freed by some treatment from water and " mucilage " is a mis- take, as oil of ordinary good quality is quite free from such things. BREAKING. Freshly made oil if heated to 400° F. suffers a slight partial decomposition; gelatinous clots appear in it, and it is said to " break"; this is due to the phosphates it contains, and any treatment which will destroy these will prevent its " breaking." A common way is to add with agitation a little sulphuric acid; the oil is afterward washed with water, and is found to be bleached somewhat; it may be bleached more by agitating warm with fuller's earth and filtering; but not all the color can be removed by any known means. What is known as " varnish oil " has been treated in some way so that it does not break; and if such oil is heated quickly to about 500° F. and VARNISH 373 cooled, it is found to be considerably bleached. This is a com- mon practice. Sometimes a very little of some lead or manganese compounds are added before doing this. It is usually put through some such treatment and allowed to settle for a month or more before being used in varnish. WEIGHT OF OIL. A gallon of linseed oil weighs 7.75 lbs.; but in selling oil by the barrel or larger quantities it is a com- mercial practice to call 7.5 lbs. a gallon, so that in buying it one gets about 3 per cent less in fact than the nominal amount. No charge, however, is made for the barrel — an oil-barrel is usually a 50-gal. cask— the value of which is usually more than the 1J gallons lacking. In making paint or varnish the full weight or measured gallon is always the unit. RESINS. Asphaltum is a mineral, but practically all the resins used in varnish are of vegetable origin, and most of them from tropical or sub-tropical countries. They exude from trees where the bark is injured, and form lumps varying in size from very small pieces up to masses of many pounds weight. In a few cases resin which is collected from living trees is used; but for the most part the varnish resins are dug up from the ground, the trees having fallen and decayed, and the lumps of resin having become buried, sometimes as much as six feet below the surface. Having for many years been thus buried they have undergone change, become harder and better suited for use. After being dug up, cleaned, and sorted the resin is packed in boxes or bags, and in this condition market resins are bought at prices ranging from about 75 cents per pound for the choicest sorts to as little as 5 cents per pound for some inferior kinds. Probably a fair average price (1914) would be about 30 cents. The valuable qualities are clearness, hardness, high melting point, pale color, luster, and perfect solubility after melting in oil. As a rule these resins are not soluble in oil or in spirit of turpentine or benzene; but after melting they are found to be so changed that they dissolve in hot oil. MELTING RESINS. Most of them require a temperature of 550 to 650° F. to melt them properly, and in melting they lose 10 to 25 per cent of their weight ; some species lose more and some less; the best and hardest resins lose about 25 per cent. If this is done in the laboratory with proper precautions it will be found that the temperature of the melted mass is much higher than that of the vapor, showing that chemical decomposition has occurred. All light-colored resins darken on melting, some more 374 ELEMENTS OF INDUSTRIAL CHEMISTRY than others. The greater part of the distillate can be condensed to a liquid; this is not done in this country, but in England and Europe it is common, partly because by refining the liquid may be made use of as a turpentine substitute, and partly because it prevents the escape of gases which may be thought objectionable in residence sections of cities. COPAL. Copal is a popular or trivial name applied to varnish resins, about as indefinite in its meaning as the term " metal." It was originally a Central American native word, and was applied to any resin. It is now used only for varnish resins, but" does not designate any particular substance. In the varnish factory resins are commonly called " gums," although true gums, such as gum-arabic, are water-soluble. Colophony is always, and correctly, called rosin, and is never spoken of as a gum. Gum-varnishes mean oleo-resinous varnishes free from rosin. VARNISH NOMENCLATURE. One hundred pounds of resin is the conventional unit, and varnishes are described as containing so many gallons of oil to this 100 lbs. of resin, weighed before melting. Thus a 20-gal. Kauri, or 20 K., is a varnish made from 100 lbs. Kauri resin, 20 gals, linseed oil, and (probably) 30 gals, spirit of turpentine, the amount of the latter not being mentioned. Ihe grade of resin may also be mentioned; thus, " 20 Brown 3 half benzene " would be 100 lbs. Kauri of the grade known as No. 3 Brown Kauri, 20 gals, oil, 15 gals, spirit of turpentine (turps for short), and 15 gals, benzene. This is a fairly accurate description and any varnish -maker would recognize it. 100 lbs. of any resin counts for about 6 or 6 \ gals, in the batch; turps weighs 7.2 lbs. and benzene a little more than 6 lbs. per gal. So this would figure as follows : 100 lbs. resin = 75 lbs. = 6 gals. 20 gals, oil = 154 lbs. = 20 gals. 15 gals, turps = 108 lbs. = 15 gals. 15 gals, benzine = £0 lbs. = 15 gals. 427 lbs. = 56 gals. Actually it will be more like 420 lbs. = 55 gals., because at least a gallon of the thinner will be lost by evaporation. LlNOXYN. When linseed oil is exposed to the air, either by blowing air through it or by exposure in thin films, it is changed into an elastic substance, not sticky or greasy to the touch, called VARNISH 375 linoxyn. This is an oxidation product, and weighs considerably more than the original oil, probably about one -fifth more; dif- ferent experimenters have reached various results. Its specific gravity is higher than that of the oil, and it is apparent that the latter has contracted in volume as well as increased in weight. This product is insoluble in oil and in turpentine and most of the other oil-solvents, and is the elastic ingredient of oil-paints and oleo-resinous varnishes. When oil is spread out in a film and exposed to the air it does not for some time appear to change, but after a certain time it rather suddenly changes into a semi- solid, gelatinous, sticky condition. Up to this point being a liquid, any contraction which may have occurred causes no notable change; but now a somewhat solid film quickly forms, in which contraction produces a state of tension. It is obvious that if this film is at all inclined to be porous, contraction will open the pores, because it stretches the solid part of the film away from the openings; and this is probably the cause of the porosity of dry linoxyn films. POROSITY. If, therefore, we can add something to the oil which will act as a flux and postpone this preliminary setting until the compound, by absorbing more oxygen, is in a more stable condition, we shall decrease the final porosity of the film. This is probably what we do when we dissolve a resin in the oil. The resulting compound — varnish — does not take its initial set until it is more completely oxidized, and the film thus formed is more nearly free from pores than a pure linoxyn film. VARNISH FILMS. Such a film has two other advantages. First, it is harder and resists abrasion better, and it is smoother, which has the same effect; second, as the liquid varnish is more viscous than oil, it may be applied in a somewhat thicker layer, and a thick film is more lasting than a thinner one. The most obvious quality of a varnished surface is its smoothness and lus- trous appearance; its brilliancy depends not only on its smooth- ness but also on its high refractive power as regards light; those varnishes having the highest refractive indices being the most brilliant. This is increased, in general', by increasing the pro- portion of rosin. Outfit for Making Varnish. The varnish-maker's out- fit is very simple. A varnish kettle is a cylindrical copper vessel about 36 ins. in height and from 30 to 36 ins. in diameter, with a flat bottom. It has a loose cover, which is provided in the middle with an upright cylindrical outlet or " chimney " about 376 ELEMENTS OF INDUSTRIAL CHEMISTRY 5 ins. in diameter and 8 ins high; it has also a hole in it for a stirring-rod; and some styles have an opening for a large funnel. The kettle is loosely set on an iron truck or wagon with three or four wheels, so built that the bottom of the kettle, which rests on a ring only slightly less in diameter than itself, is not more than a couple of inches above the floor. There is a fireplace, consisting of a round pit sunk below the floor level lined with firebrick and having a grate, under which is an ash-pit and suit- able air-flue, and nearly over which, a little in the rear, is a spacious chimney, Fig. 110, which carries off the products of combustion Fig. 110. and also the vapor from the kettle. The fuel is coke, which burns freely and without much flame, which might set fire to the kettle vapor. The stirring-rod is of stiff steel, 5 or 6 ft. long, with a wooden handle. There is a large funnel, for use in pouring in oil, which may be put into the chimney in middle of the cover, or into a special opening in the cover near one side. VARNISH-MAKING. Into this kettle is put 100 or more, commonly 125 lbs. of resin, the kettle is placed on the wagon, and wheeled over the hot fire. As the resin melts the escaping gases cause foam, which makes it necessary that the kettle should be of considerable height and capacity. In about half an hour all the resin is melted ; some varnish-makers melt with the ther- mometer in the melting resin, others depend on feeling the dis- VABNISH 377 appearance of lumps with the stirring-rod ; and from time to time the latter may be withdrawn and the adhering resin examined. Without removing the cover, the oil, which has previously been heated in another receptacle, is added ; some previously draw the kettle from the fire, others add the oil when the kettle is still on the fire. The oil and resin are cooked together, by the aid of the thermometer, until they are so combined that they will not sepa- rate on cooling; this is tried by putting a drop on a piece of glass or slate, and if it clouds on cooling the combination is not complete. In fact it is common to cook varnish more than this; the more it is cooked the greater becomes its viscosity, and the more turpentine it will take to thin it to the proper consistency. Vis- cosity is spoken of by American varnish-makers as "body"; an American says a varnish has a heavy body wUen an English- man says it is " stout/' THINNING. When sufficiently cooked, the oleo-resinous compound is, on the wagon, wheeled off to another room, well away from the fire, and a previously measured amount of spirit of turpentine (or benzene, or both) is slowly added with constant stirring. Varnishes are more or less colloidal solutions, and if some of these oleo-resinous compounds are thinned directly with benzene they form a swollen, gelatinous mass, insoluble in excess of solvent; while if a little turpentine is first added this makes a solution which may safely be diluted with benzene if desired. Some makers add driers directly with the turpentine to the hot varnish, others wait until it is cool. These driers are compounds of lead and manganese. Proportion of Ingredients. Nothing has yet been said about the quantity of oil to be added; in most varnishes it is the predominating ingredient. The larger the proportion of oil the more elastic and durable will be the varnish; the smaller the amount of oil, the harder, more lustrous and quicker drying it will be. Varnishes for furniture, which should be hard and brilliant, and free from the least tendency to tackiness, are made with 10 to 15 gallons of oil to the hundred pounds of resin; those for interior house varnishing contain from 15 to 20 gallons of oil; and for outside work, exposed to the weather, 25 to 30 gallons. These 30-gallon varnishes require about 32 gals, of turpentine or other thinner; 10-gallon varnishes take about 25 gallons of thinner. RUBBING VARNISH. Rubbing varnishes contain 6 to 12 gallons of oil; they are so called because they become hard 378 ELEMENTS OF INDUSTEIAL CHEMISTRY enough in from 1 to 6 days so that the surface may be rubbed with powdered pumice-stone, sprinkled on a pad of felt wet with water, until all the irregularities of surface are ground away, thus forming a smooth (" level ") foundation for further coats of varnish. Those which contain even as much as 20 gallons of oil will in time become hard enough to rub; after which, by rub- bing with finer materials, they may finally be polished; but this beautiful finish is not as durable as the natural gloss, which is always left on work which is to be exposed to the weather. When one coat is applied over another it is always desirable to remove the -gloss by lightly rubbing the undercoat, as the following coat does not stick well and smoothly to a glossy surface. ROSIN. Common rosin, or colophony, is extensively used in making cheap varnishes. It is not a natural resin, but is produced in the distillation of crude turpentine, being the residue left in the retort after the spirit of turpentine is distilled off. It is an acid substance ; and before use it is made nearly neutral by com- bining with it about 5 or 6 per cent of lime (calcium oxide). This makes it harder, more brittle, less easily fusible. It is made into oleo-resinous varnishes very much as are the natural resins, but with much more drier added; these varnishes are softer and less durable than the former class, but are mixed with them to make mixed varnishes of low price and medium quality. For some purposes rosin varnishes are used alone. They have good working qualities, and a small admixture of a rosin varnish to a " gum " varnish is often advantageous. They are made at lower temper- atures than the " gum " varnishes, and the greater part of the tung or China wood-oil that is imported is used in rosin varnishes, on account of its superior drying qualities, in which it alone sur- passes linseed oil. PALE AND DARK VARNISHES. To make a pale varnish it is necessary to have pale resins, but in some cases the paler pieces are softer and less valuable. The dark grades of the better kinds of resin, such as Kauri, are of excellent quality, and for many — in fact, most — purposes moderately dark varnishes are just as good as any. Even the, dark varnishes (not black asphaltum) are transparent, and have an agreeable yellow or brownish-red color; on dark wood they have even a better effect than paler varnishes, to which they are in every other respect equal. There are, of course, some dark resins of inferior sorts; and some of the best pale resins, such as Zanzibar, are of unequaled quality. VARNISH 379 BAKING JAPANS. As the hardening of varnish is due to oxidation, it follows that with an increase of temperature the process will go on more rapidly. It is equally true that the solvent will evaporate more quickly from spirit varnishes in a hot atmosphere, so that it is generally true of all varnishes. If the temperature is high enough to melt the resin of a spirit varnish, or to keep an oleo-resinous compound in a liquid state until oxidation is nearly completed, the resulting film will be non- porous. Varnishes designed for such use are called baking varnishes or baking japans; the best of them are the black japans, in which the resin is partly asphalt urn. These form coatings of great beauty and merit, strongly resisting both chemical and physical action. They are baked at varying tem- peratures; on wood, of course, at comparatively low heat, but on metal at as high as 400° F., though 300° F. is more common. The baking usually lasts three or four hours. The objects to be japanned are commonly dipped in the varnish and put directly in the oven. Since the drying is forced by the heat it is possible to use a varnish which would not dry at all (in any reasonable time) at ordinary temperatures, and such material is likely to be somewhat indifferent to chemical action. JAPAN DRIERS. Another class of japans, having no relation at all to the preceding, are composed of linoleates or resinates of lead or manganese, usually containing free oil, and often some resinous or oleoresinous varnish, and dissolved to a thin liquid with turpentine or more often benzene. These are also called driers, and they act by catalysis, inducing the rapid oxidation of the oil or varnish to which they are added. It is well known that lead and manganese form two classes of compounds — for example, a protoxide and a peroxide— and easily pass from one to the other. If they are present in the film in the higher state of oxidation they give up half their oxygen to the oil, then take up more from the air, and so act continuously as agents to pass along oxygen from the air to the oil. Manganese is more active than lead, but each has its advantages. Driers may be made with other metals, such as nickel and cobalt, which readily pass from one state of oxida- tion to the other, but have no special advantages over lead and manganese. These compounds may be made by direct heating of the metallic oxides with oil or rosin, or by decomposing soaps with soluble salts of these metals. If by use of these compounds we introduce into oil even as small an amount as two °f its weight of these metals, the effect is very marked. The use of too much 380 ELEMENTS OF INDUSTRIAL CHEMISTRY drier is objectionable, since it is likely to continue to act, slowly of course, after the film has hardened, and in time destroy its elasticity and coherence. Driers are not used in spirit varnishes, nor usually in baking japans. BOILING OIL. Long-continued heating causes linseed oil to dry with a gloss, and oil which has been heated with a little lead and manganese oxides is called boiled oil; the untreated oil is called raw oil. Films of raw oil take 5 or 6 days to dry hard enough to be handled, while boiled oil will dry in 24 hours. For special purposes, however, oil is boiled for a longer time, and in this way is made the varnish used on patent leather and for some other uses. LITHOGRAPHIC OR " STAND " OIL. Linseed oil which has been bleached or otherwise refined so that it does not " break " is heated to a high temperature, usually 600° F., or higher, for a considerable time; it is then found to be viscid, like molasses; as it is heated without the addition of driers it is not what is called " boiled oil "; it is treated best in enameled kettles or aluminum or silver-plated copper kettles, so that it is not much discolored. This is in this country generally called lithographic oil, in Europe stand oil. It dries with a gloss, and is sometimes used for mak- ing enamel paints, being regarded as equal to a varnish. It is largely used in Europe in varnish-making, the melted resin being dissolved in it. Such a varnish requires less cooking than the more ordinary ones, and rather more turpentine or other thinner. They are pale in color; but American varnish-makers think they are less durable, the oil being too much changed, and not sufficiently combined with the resin. Stand oil is largely used in Europe in paint-making also. Driers are sometimes added to varnish after it is made. The varnish is warmed to 100 to 150° F. and agitated for several hours with powdered litharge and some powdered manganese compound, either borate or oxide. These lead and manganese compounds are dried immediately before use by heating them until it is certain that all the water is driven off. The amount used is considerable, 2 or 3 per cent, as that which is not absorbed will settle or can be filtered out, CHAPTER XX SUGAR INTRODUCTORY. Highly refined commercial sugar consists of sucrose. The word " sugar " as used in this article and com- mercial^ refers to sucrose of various degrees of purity. Sucrose is widely distributed in the vegetable kingdom; two plants, however, supply practically all of the world's sagar. These are the sugar-cane (Saccharum officinarum) and the sugar beet (Beta vulgaris) . Cane is grown throughout the tropics and in some sub-tropical regions; the beet is produced in most parts of Europe, the northern and Pacific Coast States of this country and in Canada. Very little sugar is produced in the British Islands, though excellent beets have been grown there experi- mentally. The stalks are cut close to the ground, freed of their leaves and the top joints are removed at the highest one showing signs of maturity. This point is determined by the color of the stalk. The clean stalks are removed to the factory as soon as possible after cutting. In Louisiana, however, owing to danger of frost damage late in the season, the stalks are cat and covered or windrowed and left in the fields until needed. This is not feasible in the tropics, as the cut cane would soon ferment if left in the fields, and must therefore be prompt ly milled. As the cane arrives from the fields, it is unloaded upon an elevator consisting of endless chains with projecting arms or upon a belt-like conveyor composed of endless chains and wooden slats. In several unloading devices, the loaded cane car is tilted end- wise or sidewise by hydraulic power and the load is discharged upon the elevator or conveyor. The conveyor delivers the cane into a preparatory machine called a shredder or crasher, according to its type, which tears it into shreds or crashes it. The mill rollers are so arranged that the cane is crushed twice by each 3-roll mill, and at each successive crashing the cane passes through a smaller opening than before. The last mill is usually " set " with its back or bagasse roll and 381 382 ELEMENTS OF INDUSTRIAL CHEMISTRY the top roll almost touching one another, or to use the factory term, " iron to iron." A curved knife or turn plate guides the crushed cane from one pair of rolls to the next. Notwithstanding the great strength of mill rolls and shafts these are often broken bj r the straining to which they are exposed. Water is usually applied to the crushed cane or bagasse, as it is now termed, as it emerges from the rolls of the first and second mills. The bagasse is in the condition of a sponge that has been squeezed nearly dry and quickly absorbs the water, which dilutes a part of the remaining juice. The subsequent milling of this moistened bagasse extracts more sugar than would be obtained with dry crushing. The water is often all applied to the bagasse from the next to the last mill and the thin juice from the last mill is pumped back upon the bagasse from the first. There are various modifications of this method, depending upon the number of mills in the series. In this method all the juice extracted by all except the last mill is pumped to the defecating apparatus for the next stage of the manufacture. This use of water on the bagasse is termed " saturation," " maceration " or " imbibition." The yield of juice by milling varies with the quality of the cane itself. Woody canes yield less juice than those of low fiber con- tent and immature canes more than ripe, rich stalks. By dry crushing, i.e., without saturation, 75 per cent on the weight of the cane of juice may be readily obtained with the immature canes of Louisiana, whereas in the tropics it usually requires very heavy milling and liberal use of saturation water to express an equivalent quantity. PURIFICATION OF THE JUICE. The juice as it flows from the mills is turbid and filled with impurities, both chemical and me- chanical. It is first strained through perforated brass sheets having 400 round holes and upward per square inch. The surface of the strainer is cleaned by mechanical scrapers, which deposit the fiber and trash upon one of the bagasse conveyors, to be again passed through a mill. DEFECATION PROCESS. The next stage of the purification is the defecation process. The raw juice is always of acid reac- tion. This acidity is neutralized with milk of lime, dry slaked lime, or powdered quicklime and the juice is then heated to coagu- late the albuminoids. In the ordinary method of defecation, the juice is first limed in mixing tanks to slight alkalinity or faint acidity, according to SUGAR 383 the grade of sugar to be made, and is then conducted to defecators. These are tanks fitted with steam coils or steam jacket at the bottom. Many factories lime the juice in the defecator. The limed juice is now heated with steam. The heat is continued until a heavy blanket of scum rises to the surface and breaks or " cracks." When the cracking point is reached the heat is dis- continued and the juice is left at rest for the precipitates to settle. This process separates nearly all of the albuminoids, partly by coagulation, and a part of the acids, fat, wax and gums. Some lime salts are formed and persist throughout the manufacture. A part of these salts subsequently deposit upon the heating surfaces of the evaporating apparatus. If the process is conducted with care, there is no decomposition of the sugars, but with exces- sive liming the invert sugar is decomposed in part and forms dark, bitter compounds with the lime. These lime salts impede the crystallization of the sugar. The ripe cane frequently con- tains no levulose, but this sugar always appears in the molasses, even if no sucrose is inverted, and is attributed to the action of the salts upon the dextrose. In an acid defecation, as in making white sugar, if insufficient lime is used, inversion of sucrose occurs. After allowing sufficient time, usually an hour or longer, for the subsidence of the precipitates, the clear juice is decanted from between the blanket of scum and the mud at the bottom of the defecator. The clear juice is run into storage tanks preparatory to the evaporation. The scum and mud mixed together are pumped into filter presses and the filtrate is added to the clear juice already obtained. The press-cake is used as a fertilizer or on many estates is wasted. The sugar content of the cake is reduced by either washing it with water while still in the press or by removing the cake, beating it to a cream with water and re- filtering. The unwashed cake contains from 8 to 12 per cent of sugar, according to the richness of the cane and the quantity of water used in washing the mud from the defecators, and that by refiltration or thorough washing contains about 1 per cent. Phosphoric acid or acid phosphate of lime is often used in the defecation, especially in making white and high-grade yellow sugars, to form a voluminous precipitate, which carries down much flocculent and some coloring matter. EVAPORATION. The purified juice is next evaporated to a sirup of about 54° Brix (30° Baume). The evaporation is con- ducted in multiple-effect vacuum evaporators. There are several types of these multiple-effect evaporators, but the basic prin- 384 ELEMENTS OF INDUSTRIAL CHEMISTRY ciple of all is the same. The evaporation is so conducted that a stream of juice is fed into the first vessel and flows from effect to effect, gaining in density as it travels, and finally finished sirup of the desired density is constantly pumped from the third effect. This method may be extended to four vessels, which is termed a " quadruple-effect,'' and so on. Owing to mechanical difficulties, this so-called standard type of evaporator Fig. 111. is not used with more than four vessels. The water from the steam condensed in the calandrias is used for boiler feedwater and the surplus for maceration , of bagasse and other purposes, thus utilizing its heat. Crystallization of the Sugar. The concentrated juice or sirup is pumped from the multiple effect to storage tanks preparatory to the crystallization of the sugar. The crystalliza- tion is accomplished in a single-effect vacuum pan such as is shown in Fig. 111. SUGAK 385 The vacuum or strike pan, Fig. Ill, is a cylindrical vessel, A, usually of cast iron, having a dome-shaped top with vapor pipe, B, and a conical bottom provided with a strike or discharge valve, C. The pan is equipped with large heating coils of copper, and steam and vacuum gauges, also sight glasses, D, for watching the prog- ress of the work, a proofs tick for drawing test samples and suit- able pipe connections for sirup and molasses. The steam enters a manifold, E, from which it is distributed to the coils; each of the latter has a stop valve for steam, and drainage connections for condensation water. The vapors from the boiling sugar solu- tion pass through a save-all, F, connected at the bottom with the pan, where they expand and meet baffle plates, so that sugar entrained with the vapor may be returned to the apparatus. The vapors from the evaporating liquor pass into a condenser, G, in which they meet a shower of water. The incondensable gases are led off through a pipe, K, from the lower part of the condenser to a vacuum pump. The condensing water and water of con- densation are carried off through the " leg pipe " or torricellian tube, H. The foot of the leg pipe is sealed with water in the hot well, /. The above is a description of the " dry vacuum system." It is so called because only the incondensible gases are separately removed by the pump. In the " wet system " the condensing and condensation waters and the gases are carried off by the vacuum pump. The dry system is preferred for large instal- lations. Many factories use a condenser in common for the multiple effects and vacuum pans. In crystallizing the sugar, the pan boiler proceeds as follows: Having produced a vacuum in the pan he draws in what he deems to be sufficient sirup for gaining the " strike," and evaporates it to a saturated sugar solution at the desired temperature. He regulates the boiling-point by the injection of water into the condenser, thus controlling the vacuum. When ready to form the crystals, i.e., grain the strike, he heats the liquor to a tempera- ture of from 60 to 70° C, the grade of sugar desired determining this condition. After the formation of the crystals the pan-man continues the boiling, injecting sirup by charges or continuously if he so elect, to compensate for the water evaporated and obtain a satu- rated solution, but always avoiding temperature and other con- ditions favorable to further formation of crystals. The charges must be large enough to enable the crystals to circulate freely 3S6 ELEMENTS OF INDUSTRIAL CHEMISTRY but not too large in proportion to the crystal surface. This forces the sugar to deposit upon the crystals already present, which soon grew to the desired size. The material is now concentrated to a solid content of about 92 per cent more or less, and is termed " massecuite." The steam is shut off, air is admitted to the pan, and the " strike " is discharged through the foot-valve into suit- able recipients. In making small-grained sugar, the crystals are formed when the pan is about half filled with concentrated syrup. " Low graining " produces a coarse sugar. If very large crystals are desired, a part of the strike is removed from the pan or is " cut- over " through pipes into an adjoining pan, and the boiling is resumed. If the cut-over pipe is used both pans may be filled with large-grained sugar or one strike may continue with sirup and the other be completed with molasses to form a lower grade massecuite. PURGING AND CURING THE SUGAR. The massecuite, after the completion of the crystallization, is conveyed to mixers, from which it is drawn off into centrifugal machines for the separa- tion of the molasses from the crystals. The centrifugal consists of a shallow drum or basket, having perforated walls and lined with finely perforated brass sheets or brass wire cloth. A customary size for large machines is 40 ins. diameter by 24 ins. depth. By suitable transmission a machine of this size is rotated about 1000 revolutions per minute. A charge of massecuite is run into the centrifugal, usually while the latter is slowly revolving and the speed is then increased until the molasses is thrown off by the centrifugal force and the sugar is retained by the perforated lining. In making raw sugar for refining, after the above treatment, the crystals are ready for packing and shipment. In the event, however, of the crystals not testing sufficiently near the market basis, 95 per cent or 96 per cent by the polariscope, according to market conditions, after all but the closely adhering molasses has been thrown off by the centrifugal, a little water is sprayed upon the wall of sugar, which quickly removes a part of the low- test molasses from it. Sugars polarizing approximately 96° are termed " centrifugals " and are the basis of market quotations for raw sugar. In making white sugar in the factory, the juice having been purified as has been described, the crystals are thoroughly washed in the centrifugal with water. Usually a little ultra- SUGAB 387 marine is added to the water " to kill " the yellow tinge of the crystals. Beet Sugar Raw Material and Its Preparation. The sugar beet is grown from seed. The rows are seeded thickly and the young plants are thinned to leave vigorous ones about 6 ins. apart in the rovv. The desirable beet is small, the topped root weighing about a pound, and is tapering, somewhat top-shaped, regular in form and has few rootlets. Large beets are not usually as rich as the small ones described. In preparing the beets for the factory, they are topped at the lowest leaf scar and are then hauled to the factory, where they are stored in sheds or in the open upon platforms, according to climatic conditions. When necessary to pile the beets in the field for any length of time, they are protected by a light covering of leaves and earth. Climatic conditions determine the methods of storage. In very cold, even climates in the United States very large piles of beets have been successfully stored on open platforms. The frost affects only the outer layers, and as the thawing is gradual the beets are but little damaged. The beets are flushed to the factory in flumes, waste water being used largely for this purpose. They are elevated to the washing machines by an apparatus which also removes many of the adhering stones and are thoroughly cleansed. From the wash- ing machines they are elevated to automatic scales, above the slicers, for weighing. EXTRACTION OF THE JUICE. The juice is extracted by the diffusion process. The washed and weighed roots are conveyed to the slicing machines, which cut them into more or less V-shaped slices or cossettes. The slices are packed loosely in the cells of the diffusion battery, which extracts the juice by a somewhat imperfect process of dialysis, the cell walls supplying the mem- brane. The diffusion battery consists of a number of cylindrical iron vessels, usually twelve, with suitable pipe connections, heating devices and top and bottom doors. The pipes are so arranged that the liquid may be conducted from one vessel to the next, entering at the top or bottom, at the will of the operator, and permitting any vessel to be disconnected from the series for charging with slices and discharging the spent pulp. A general 388 ELEMENTS OF INDUSTRIAL CHEMISTRY view of the upper part of a circular diffusion battery is shown in Fig. 112. In operating the battery, a vessel or diffuser is filled with beet slices, then warm water is turned into it at the bottom connection, driving out the air through a cock in the cover; by the time this diffuser is filled with water, the next one has been charged with Fig. 112. beet slices; the direction of the current of liquid in the first is reversed, the water now entering at the top, and the thin juice, as it now is, passes into the second diffuser at the bottom, expel- ling the air as from the previous vessel. The thin juice is heated in transit and passes into successive diffusers as they are filled with slices. When about ten or eleven vessels have been filled, according to the number in the battery, a measured volume of juice is drawn from the last one filled, the water pressure applied at the first diffuser of the series forcing the juice to circulate. SUGAR 389 Air pressure is used in many factories, when drawing a charge of juice, to promote economy of water and sugar. The use of water is sometimes preferable, as with it the exhausted pulp may be flushed through canals to the elevators. The spent pulp is elevated to continuous presses in which a large part of its water is expressed. The juice drawn as described is strained through depulpers and conducted to tanks for the next stage of the manufacture. The slices in the first diffuser of the series are now practically exhausted, but 0.15 per cent sucrose, more or less, remaining in them. This vessel is disconnected from the series and the exhausted pulp or cossettes discharged from it. From now on each time a vessel is charged with beet slices and juice, a measured volume of juice is drawn from it and the spent pulp is removed from the first diffuser of the series, each diffuser in regular order containing the exhausted pulp. The rate of filling the diffusers depends upon their shape, size, the number in the battery and the capacity of the factory. The usual rate of filling is a diffuser of beets every six to seven minutes. PURIFICATION OF THE JUICE. The beet juice always con- tains very fine pulp that passes the strainers of the diffusion battery. This pulp is largely removed by special strainers called " depulpers," and a part of it is carried down with the carbonate of lime in the purification of the juice. The liming is followed by the double or even triple carbona- tion process. Both the liming and carbonation are usually spoken of as the " carbonation process." Carbonic acid is forced into the limed juice through distribu- ting pipes. The lime is precipitated as a carbonate and salts of the acids of the juice. The carbonate carries down mechan- ically many of the impurities that have separated and also much of the coloring matter. The injection of carbonic acid is con- tinued until the juice retains an alkalinity equivalent to about 1 to 1.5 grams of calcium oxide per liter, using phenolphthalein as an indicator. Should this carbonation be carried too far, many of the impurities would again pass into solution. The juice foams considerably during this operation, and steam jets oil or grease are often used to beat it down. Very deep tanks are used in modern installations to obviate the use of steam, grease, etc. The use of steam is objectionable on account of its decomposing action on the sucrose in the foam. 390 ELEMENTS OF INDUSTRIAL CHEMISTRY At the conclusion of this carbonation the juice is heated to near its boiling point and is then filter-pressed. The filtrate flows into the second carbonation tanks. The juice usually still contains sufficient lime, but in some factories a small quantity, about 0.25 per cent, is added. It is again carbonated, this time at a temperature near 100° C. This is termed the " saturation." The injection of carbonic acid is continued until only slight alkalinity due to lime remains. In determining the end point the alkalinity due to other alkalies than lime must be taken into account. The usual alkalinity of the saturated juice due to lime is 0.01 per cent or slightly higher. Evaporation, Crystallization, Purging and Curing THE SUGAR. These processes and the apparatus used are practically the same as those employed in the cane-sugar industry already described. The American factories usually produce granulated sugar. The granulator is simply a dryer so arranged that the crystals of sugar are separated from one another during the progress of the drying. The granulator is a long sheet-iron cylinder, placed in a nearly horizontal position and arranged so that it can be revolved. Nar- row deflecting plates or shelves are attached to the inside walls of the cylinder and extend throughout its length. The apparatus is inclined slightly toward the discharge end, at which are attached wire screens for sifting the sugar; there is also at this end a small room, one wall of which is formed of steam coils. A steam drum extends from end to end of the dryer at its axis. At the inlet end of the apparatus there is a suction fan to draw air through it and a hopper for feeding in the moist sugar. There are several types of dryers, but all depend upon the same principles. As the sugar leaves the centrifugal machine it is elevated to a mixing floor. It is here thoroughly mixed, since all the pans of sugar and all the centrifugal charges are not of uniform color. The sugar is next fed into the granular or dryer, through which a current of hot air is drawn by the suction fan. The crystals are carried upward by the revolving cylinder and in falling from the shelves, through the heated air, are separated and dried. By reason of the inclination of the dryer the sugar travels to the dis- charge end, where it is classified by the sieves and delivered to the packing spouts. SUGAR 391 Sugar Refining RAW MATERIAL. Most cane-sugar factories make raw sugar testing from 95° to 98° by the polariscope and known commercially as 96° " centrifugal sugar." The Cuban product usually polarizes approximately 96° and that of Java and the Hawaiian Islands up to 98°. Many factories make a lower grade of sugar, a soft sugar crystallized at rest in tanks and testing about 87° and often lower. The market basis for these sugars is 96° and 89° respec- tively. There is an addition to the price for tests above and a deduction for those below these numbers. The increment of price per degree above these numbers is smaller than the deduction for those below. Similarly the price paid for the sucrose in an 89° sugar is less than that for the sucrose in a 96° sugar. These mar- ket conditions discourage the production of sugars much below 96° Of the sugars imported into New York probably over 80 per cent test above 94°. Mingling, Washing and Defecating. The raw sugar is carried by elevators to mingling machines, which mix it with sirup and form a magma. This permits spinning the sugar in a centrifugal precisely as though it were a massecuite and thor- oughly washing the crystals. This station is termed the " wash plant." The washed sugar is melted with water to form a liquor of about 60° Brix, and a coefficient of purity of about 98.5° to 99°. The washings or sirup are used in part in mingling raw sugar for subsequent magmas and the remainder is pumped to the defecators or " blow-ups." The blow-ups are provided with perforated pipes through which steam is blown into the liquors. Sufficient milk of lime is added in the blow-up to render the solutions strongly alkaline and then the alkalinity is neutralized with monocalcic phosphate solution or phosphoric acid. The reagents are used in sufficient quantity to produce a large precip- itate that separates sharply from the solution. After the addition of the reagents the liquor is heated in the blow-up to a temperature of approximately 82° C. BAG FILTRATION. The warm liquor obtained as above is run into bag or Taylor niters. These filters consist of a large number of heavy twilled cotton cloth bags about six feet long. These bags are attached to nozzles or " bottles " and suspended in a cast-iron chamber. A cotton sleeve of smaller diameter is placed over each bag. This causes the bag so to arrange itself as to give the effect of a fluted filter. 392 ELEMENTS OF INDUSTRIAL CHEMISTRY The flocculent precipitate from the defecation, consisting of tricalcic phosphate, organic lime salts, gums, etc., and carbon from the bone-black dust, are retained in the bags and a brilliant filtrate flows from them. The precipitate or " mud " is first washed with hot water while it is still in the bags partly to free it of sugar. After this preliminary washing the bags are taken from the chamber, the mud is removed and they are given a thorough and systematic washing in a series of tubs. The bags are passed through a wringer on their way from tub to tub. The mud and " mud water " are filter-pressed and the filtrate is evaporated with other " sweet water " to a sirup in a multiple effect evaporator. The " thin wash-water " from the bag filters and the washings from the raw sugar packages are evaporated with the press filtrate. CHAR FILTRATION. Animal charcoal, bone-black or " char " filters are cylindrical iron cisterns about 10 feet in diameter and 20 feet deep. These are filled with bone charcoal. High-grade bag-filtered sugar liquor, heated to about 71° C, is passed over the char and is followed successively and syste- matically by granulated sirup, i.e., the run-off sirup obtained in purging sugar to form the " granulated " grade, washings and other low-grade solutions. In making " soft white " sugars, the liquors are filtered in succession through three filters of char. The liquors flowing from the char are separated into grades according to their color and test. These grades are considered in the vacuum-pan work. When the char no longer decolorizes the solutions properly, the sugar is washed from it with hot water and is largely recovered. When the purity coefficient of the washings falls too low to admit of profitable treatment for the recovery of the sugar, the water is run to waste. The rich washings are concentrated with other sweet water. The wet char is discharged from the filters and is dried with the heat of the kilns that would otherwise be wasted. The dried char is heated or " burned "at a dull red heat in tubular retorts in kilns with exclusion of ( air from the retort. This process is termed " revivification." The organic impurities of the sugars that have been absorbed during the filtration are burned and the char is returned to filter service in practically as good condition as before use. The char may be used over and over again a great many times, a revivification following each use. The dust is removed by screening and must be compensated for by SUGAR 393 the addition of from 25 to 50 per cent of new bone-black annually. About 50 to 60 hours are required for a complete cycle of filter operations. The filtration of sugar solutions through animal charcoal is primarily for the purpose of removing their color. The char has the further property of absorbing much of the non-sugar of the raw material and thus promotes the crystallization of the sugar. A good char will absorb 85 per cent of the coloring matter, 33 per cent of the inorganic matter and 50 per cent of the organic non- sucrose contained in the raw sugar solution filtered through it. It may be seen from these descriptions that the char filter station is one that requires skill and a thorough control in its conduct. Errors of judgment here may result in an inferior product and a loss of sugar. Crystallization and Curing the Sugar. Before con- sidering this stage of the refining a few definitions are necessary : Refiners term a solution from which no sugar has been removed a " liquor," and one from which sugar has been extracted a " sirup." The " sirup " of the raw sugar factory corresponds to the liquor of the refinery and the "molasses" of the factory to the sirup of the refinery. The crystallization of the sugar is accomplished in vacuum pans in general as described in the raw-sugar section of this chapter. The liquors have a very high initial purity as com- pared with the factory sirup, and, therefore, require repeated crystallization sufficiently to impoverish the final or barrel sirup. The crystals are formed at a high temperature in boiling hard sugars such as granulated, usually above 77° C. This tempera- ture is maintained long enough to produce sharp, clean crystals. In boiling soft sugars, on the contrary, a low pan temperature and very white liquors are essential. A comparatively dark- colored liquor will yield white sugar if the crystallization is con- ducted at a high temperature, since the crystals will be hard and absorb little coloring matter from the sirup. The methods of pan boiling as above described are typical of a refinery making only hard white sugars. Where soft white and yellow sugars are to be made, the aim is to produce a product of low polarisation and good color by combining suitable liquors and sirups and usually boiling the pans at low temperatures. The sugars are purged of sirup in centrifugal machines. The subsequent stages of manufacture depend upon the grade of sugar that is required. Granulated sugar is cured as has been described 394 ELEMENTS OF INDUSTRIAL CHEMISTRY for beet sugar, by drying and separating the crystals in a granu- lator or dryer. Cube sugar is made by molding the moist sugar under pressure and then drying it in an oven. The yellow and soft white sugars are packed while moist, as they leave the cen- trifugals. Powdered sugar is obtained by grinding very coarse granulated sugar and bolting it through silk bolting cloth. Loaf sugar and tablets are cut or broken from loaves and slabs molded from a magma of white sugar and high-grade white liquor. There is a very large number of grades of refined sugar, the classification depending upon color, grain, etc. CHAPTER XXI STARCH, GLUCOSE, DEXTRIN AND GLUTEN Starch and Starch Granules. Starch is widely dis- tributed in the tissues of the higher plants, and makes up the larger part of the solids of grains and tubers. AY hen pure, it is a fine white powder having a density of 1.6 and at ordinary temperature is quite insoluble in water, alcohol, ether, or other common sol- vents. Under the microscope, starch appears as minute, white, translucent grains varying much in size and shape, but so charac- teristic that it is usually comparatively easy to determine their botanic origin. If starch is heated to about 70° C, the exact point varying somewhat according to its nature and origin, it pastes or swells up into a pasty jelly, the viscosity of which also varies much in different starches. The microscope shows this to be due to the granulose swelling through absorption of water, and bursting the granule. The granules can be gradually ruptured mechanically by grinding starch with sharp sand or in similar ways, or the " cellulose " can be removed by chemical reagents such as dilute solution of caustic alkalies or zinc chloride, when pasting occurs readily in cold water. CLASSIFICATION. Commercial starches are classified accord- ing to their pasting characteristics into thick- and thin-boiling. The old-fashioned laundry wheat-starch is typical of the first class as a 5 per cent water mixture pastes into a thin translucent sirup, scarcely gelatinous at boiling temperature. Corn starch, such as sold for food, when mixed with boiling water in the above pro- portion, forms a practically non-fluid paste and is characteristic of a il hick-boiling starch. It is now known that these variations in pasting properties of starch of different kinds are largely dependent on the conditions of manufacture and that thick- boiling starches can be made thin-boiling by suitable treatment. These properties as well as the degree of gelatinization of the cold paste are of great importance in preparing starches for cer- tain trades. In laundry work and the textile manufactures, for 395 396 ELEMENTS OF INDUSTRIAL CHEMISTRY instance, the demand for a paste thin enough to penetrate the fabric when hot without coating the surface and at the same time with body enough to give the requisite stiffness make certain types of thin-boiling starches highly desirable. Thin-boiling starches are also used extensively in confectionery. In other industries, as in paper-box making and in certain lines of textile work, thick-boiling starches are required. SOURCES. Notwithstanding the great variety and wide distribution, there are comparatively few sources of commercial starch. By far the greatest amount manufactured in the United States is made from Indian corn (maize), which averages about 55 per cent starch and of which about 40,000,000 bushels are consumed annually in the manufacture of commercial starches and derived products. Considerable potato starch is also made in this country as well as some wheat starch, the latter being prepared from flour. Tapioca and sago starches are imported to some extent from the far East, the latter used particularly in the manufacture of envelope gums. Cassava starch from Florida and the West Indies has a limited use, and is noted for the body of its paste. Method of Manufacture. The general principles of starch manufacture are: (1) Disintegrating the plant tissue in such a way that the starch grains are set free but not ruptured ; (2) separating the gluten by diluting with water the disinte- grated mixture which has previously been treated with chemicals, or subjected to fermentation, and then settling out the heavy starch by subsidence; (3) washing the starch by agitating with water in tanks, " running " or decantation; (4) recovery of the starch by draining in cloth-bottom draining boxes or in deep frame filter-presses; (5) drying the starch in kilns. The corn is shoveled from the railroad cars into conveyors, from which it is spouted into the steep tubs, which are large wooden vats containing about 2000 bushels. Here it is soaked from two to four days in warm water containing about 0.2 per cent of sulphurous acid. The water is circulated through the corn and by means of an adjoining heating tank is kept at a temperature of 50° C. (120° F.). The sulphurous acid seems to have a softening effect on the glutinous parts of the kernel and at the same time prevents undesirable fermentative changes. When the grain is thoroughly softened by the steeping so that the contents of the kernel can be readily disintegrated by moder- ate pressure, it is usually passed through a Fuss mill. This mill STARCH, GLUCOSE, DEXTRIN AND GLUTEN 397 in its essentials consists of two parallel vertical plates, rapidly revolving in opposite directions and carrying studs which project between each other. The corn dropping between these plates is thoroughly, although not finely broken up. The tough, rubbery germ at the apex of the kernel, which contains practically all of the oil, over 30 per cent of its weight, passes out entire, and is separated from the rest of the grain by passing the mass, mixed with an appropriate amount of water, through germ-separators, which are tanks containing agitators so constructed that the movement brings the germs to the surface, where they are removed by an appropriately placed spout and sieves, the heavier parts of the grain passing off below. The germs are drained and washed from adhering starchy liquor, dried, ground and the oil pressed out of the warm mass by means of oil-presses of the usual construction. This oil is used principally for soap making and for the manufacture of a vulcanized product and in rubber making, although it can be applied to most purposes to which a semi-drying oil can be put. The remaining oil cake is an excel- lent cattle food. It is ground into meal or shipped in the original cake, the latter, owing to its compactness and unalterability, being particularly adapted for export. The remaining disin- tegrated grain is mixed with water (liquor from the separators), reground in a buhr-stone mill, and the semi-liquid mass passed over the shakers. The shakers are inclined bolting-cloth sieves of about 200 mesh. The starch granules with most of the gluten are washed through the bolting-cloth by jets of water or starch liquor, while the woody portions fall off the lower end of the sieve. This process is usually repeated two or three times, the bran after each shaking being passed through roller mills such as are used for grinding flour. The bran or " wet feed " is finally passed through the slop machine, which wrings out the enclosed liquor and is either sold for cattle feed in this moist state or it may be dried, being often mixed with the gluten meal. The starch and gluten liquor from the shakers is agitated in tanks to keep the starch in suspension, and its density adjusted to 4-6° Be. It is then passed over the runs or tables, which are practically level, the incline being usually only about 4 ins. for troughs 120 ft. long and 2 ft. wide. As the liquid slowly flows down the run, the heavy starch granules, rolling over each other, are practically freed from the adherent coagulated part of the gluten and are deposited upon the bottom, the gluten being carried off the end of the trough. Men with wooden pad- 398 ELEMENTS OF INDUSTRIAL CHEMISTRY dies keep the surface of the deposited starch smooth to prevent loss of the starch through any cutting action that might be caused by irregular depositing or accidental obstruction. The deposited starch, which extends in a layer of about 1 ft. thick at the upper end of the run to practically nothing at the foot of the run, is shoveled out of the troughs into cars running on a track over the top of the trough and is then dumped into the breakers. The breakers are tanks provided with revolving agitators, by means of which the starch may be mixed to a thick cream with water and washed once or twice by decantation accord- ing to the quality desired, or it may be purified by revolving again on the tables. The gluten liquors from the tables always contain consider- able starch which cannot be recovered as commercial starch. The liquors, therefore, are settled to remove the excess of water and the residue passed through filter-presses, the 'cake thus formed being dried, ground, and sold as gluten meal. This gluten meal is often mixed with corn bran to form gluten feed. The starch milk is either lun into molding boxes, wooden frames with cloth bottoms, to drain off the water, or filter-presses with deep frames are used. DRYING METHODS. The starch is either dried in trays forming pearl starch, or boxed, packed tightly in paper-lined boxes, and then the partially dried cake transferred to the drying kiln. The kilns are of various designs. Some are in the form of wooden tunnels, through which the cars containing the starch are pushed along by the cars of wet starch entering at one end, the cars of dry starch being taken out at the other. The temperature varies considerably at different parts of the kiln and depends on local factory practice, 160-180° F. being the customary tempera- ture for pearl starch, the drying taking eighteen or twenty hours. Lump starch which is boxed is allowed to dry partially at a much lower heat, the blocks turned out of the frames being placed on shelves in a kiln the temperature of which is about 130° F. A yellowish crust which is about \ in. thick forms on the out- side of the blocks; this is removed and the mass of clean, white starch again returned to the kiln, where it is dried for several days at a temperature of about 160° F. During this drying the lumps split up into miniature basaltic-like masses, technically known as crystals. The size of the crystals can be regulated by the temperature; a low heat giving larger and more irregular lumps. STARCH, GLUCOSE, DEXTRIN AND GLUTEN ■ 399 Starch when air dried contains from 12 to 15 per cent of mois- ture, and if more thoroughly dried in the kilns it will soon absorb water when exposed to the air until the above percentage is reached. The moisture in starch varies also with the humidity of the air; starch dried by heat being one of the most hygroscopic substances known. ALKALINE STARCHES. The description given above applies specifically to the manufacture of the so-called neutral, thick- boiling starches, and in general to corn starch. In making alkali starches, caustic soda is added to the starch and gluten liquors before running so as to make the gluten more soluble. Such starches have less nitrogenous impurities but are high in ash, as it is impossible to wash all of the alkali out. Alkaline starches give thicker pastes than neutral starches made by the sweet or sulphite processes. THIN-BOILING STARCHES. Thin-boiling starches are made by subjecting the starch to a treatment with very dilute acids at temperatures below the bursting point of the granule, usually 35-50° C. This causes an incipient hydrolysis of the contents of the granule, but does not perceptibly affect the enveloping starch cellulose, the dried product being indistinguishable from the original starch, even by careful microscopic examination. A certain very small amount of the granule contents is rendered soluble and can be removed by washing the starch with cold water and filtering. The amount and nature of this soluble carbohydrate, which can be detected by adding a drop or two of a very dilute iodine solution, depends on the extent of the acid modification. Two general methods of making thin-boiling starches are used in factory practice. The first, known as the drying in proc- ess, consists in adding either sulphuric or hydrochloric acid in very dilute form, usually about 1 per cent upon the weight of the crude green or mill starch as taken from the runs mixed with water. The excess of liquid is then drained off and the starch allowed to dry gradually at a gentle heat. This process has been practically suoerseded by the in suspension process, in which case the green starch is dumped into a tank of hot water containing 0.1-0.2 per cent of acid and kept in suspension by means of agitators. When the process is complete, as shown by pasting tests, the acid is neutralized, the starch is drained and then dried in the usual manner. — This latter process has been developed largely by Duryea, who has taken out patents. These thin- 400 ELEMENTS OF INDUSTRIAL CHEMISTRY boiling starches are now made in large quan cities, having largely taken the place of wheat starch in the laundry trade. POTATO STARCH. Practically all of the starch used in Europe is made from potatoes. Potatoes contain only from 17 to 20 per cent of starch, but the actual yield per acre is more than either corn or wheat, for the reason that the potato yield is 6| tons per acre against about 25 bushels for corn and 31 for wheat, or less than a ton of grain. The potatoes are soaked in vats of water for several hours and then washed in a long trough containing a spiral stirrer which tosses them about, thus giving a thorough rubbing. Some fac- tories use revolving cylinders for the same purpose. The potatoes are then introduced into rasping machines equipped with rapidly evolving knives, the pulp thus formed being passed through sieves to remove the fiber and the filtrate allowed to settle. The lower layers of white starch are drawn off and the upper gray layers still containing some fiber are received and settled, this being repeated several times. The starch is then purified on runs and dried in a similar manner to corn starch. Potato starch is often made thin -boiling by methods analogous to those used in corn-starch modifications. Certain patented processes designed to purify the starch by oxidizing the nitrog- enous compounds by use of potassium permanganate and other oxidizers also produce thin-boiling modification. Commercial potato starch usually contains about 20 per cent of water. WHEAT STARCH. Wheat starch is usually made from flour, either by the old-fashioned method of allowing the mixture of flour and water to ferment in vats and then purifying the starch by settling, in which case the gluten is destroyed by fermentation and a thin-boiling starch results, or by the Martin process, in which the gluten is saved and a thick-boiling starch produced. In this latter process, masses of dough made by moistening the flour are placed in a special kneading machine in which the dough is kneaded by grooved rollers working in a swinging frame, the starch being washed out through sieves by jets of water, settled and passed over runs. The resulting starch when dried and finished is thick-boiling and the gluten, still containing several per cent of starch which it is impossible to remove mechanically, is recovered as a rubbery mass. COMMERCIAL GLUCOSE AND OTHER PRODUCTS OF STARCH HYDROLYSIS. Starch, according to Brown and Morris, is a highly condensed hexose carbohydrate of the formula {C^lioO^n, STARCH, GLUCOSE, DEXTRIN AND GLUTEN 401 consisting of approximately 100 anhydride groups which can be resolved by suitable hydrolytic agents into as many equivalents of dextrose, providing the hydrolysis is sufficiently prolonged. Dilute acids will produce complete hydrolysis, the rate depending on the nature of the acid and varying approximately as the con- centration, but increasing rapidly with rise of temperature. When starch paste is subjected to the action of an acid, it is gradually resolved into simpler carbohydrates, the reaction being the result of the breaking up of the numerous anhydride groups of the com- plicated starch molecule with the formation of hydroxyl radicles from the water present, the acid not going into the combination but acting catalytically. The speed at which this hydrolysis proceeds depends on the amount and nature of the acid and the temperature. If the hydrolysis is carried to completion, the final product is a glucose sugar called dextrose, although in actual practice some small quantity of decomposition products are usually formed. The intermediate hydrolytic substances are very complicated, but behave chemically and physically as molecular aggregates of three bodies — dextrose, a biose sugar known as maltose, and a dextrin with the properties of the original starch paste. This progress of the hydrolysis, or conversion of starch paste, manifests itself by characteristic chemical and physical changes. The thick paste loses its colloidal nature and rapidly becomes more limpid, the concentration of the solution increases, although the dissolved carbohydrates become specifically lighter, and the solution becomes distinctly sweeter in taste. If tested with a weak aqueous solution of iodine, the deep sapphire blue given by the original starch paste changes as the hydrolysis proceeds, passing into violet, then to a rose red, which in turn changes to a reddish brown, which grows steadily lighter until just before complete hydrolysis is reached it disappears altogether. A few drops of the solution poured into strong alcohol give a copious white precipitate during the early stages of the conversion; as the hydrolysis continues the amount of precipitate becomes less until near the end, when no precipitate is produced. If the conversion products are tested polariscopically, it will be found that there will be a progressive fall in specific rotation values from that of starch paste (202°) to that of dextrose (52.7°). The Fehling test shows no copper reduction with starch paste, at the beginning of the hydrolysis, but pro- gressively increases till the maximum reducing power is reached, 402 ELEMENTS OF INDUSTRIAL CHEMISTRY when all of the converted products are finally transformed into dextrose. Since the discovery of the process of converting starch into dextrose by the action of heat and acids, as long ago as the begin- ning of the last century, dextrose in a crude form and known as starch sugar or grape-sugar has entered more or less into commerce, but its importance as a product is small as compared to that of glucose, which latter has been developed in the past thirty years and become practically indispensable in many food products. The term " glucose " as used to define this product must not be confounded with dextrose or its isomers, but has reference to a special commercial sirup, which is always sold under this desig- nation. The name " corn sirup," which has been suggested, would seem to be a happier designation, as is the German " Starke- zucker sirop." It is a thick, viscid sirup, practically clear and colorless, or of light amber tint, and is a product of the partial hydrolysis of starch. Its composition varies somewhat, but the average product has a specific rotation of about 140°, with a Fehling reducing value of about 47 per cent that of dextrose. MANUFACTURE OF GLUCOSE. Glucose is manufactured on a large scale in this country conjointly with starch, gums, dextrins, and numerous valuable by-products. Practically all of the com- mercial product is made from corn (maize), what is known as " No. 4 " being usually taken, although all grades are used. The following diagram outlines the process and will assist in following the steps, which as far as the production of the green (crude) starch are identical with those of corn starch manufacture which has already been described. The green starch is taken directly from the tables to the con- verter, being shoveled off the runs, and mixed with water in a breaker, a tank with an agitator, to a thick cream, usually standing about 20° Be. The converted liquor is turbid from the colloidal albumi- noids it contains and has a density of about 16° Be. It is imme- diately blown out of the converter into the neutralizer, which is usually a large covered wooden tank provided with a stirrer and also having ventilating shafts for the removal of hot vapors. Here it is treated with a dilute solution of sodium carbonate, which not only neutralizes the acid, but at the same time coagu- lates the colloidal albuminoids and precipitates the dissolved iron, so that a bright filtrate is obtained. From the neutralizer, the liquor goes to bag-filters of the STAECH, GLUCOSE, DEXTEIN AND GLUTEN 403 Scheme of Glucose Manufacture Corn i Steep Tubsv ^Steep-liquor Germ Separators— Fuss Mills \ Evaporators Oil Presses Buhrstone Mills / /i i / / (Oil) Rolls / / \ 1 / (Germ-meal) Shakers— Wet-Feed (bran) Slop-machine Starch tables | ("runs") \ Filter presses (" Green " Starch) Dryers Breakers / i Mills Converter / i (Gluten-meal) Neutralizer Evaporator Bag Filters (Bag liquor) Bone-char filters (Light liquor) Evaporator (Heavy Licuor) Bone-char niters i Vacuum pan I Finished Glucose 404 ELEMENTS OF INDUSTRIAL CHEMISTRY type used in sugar refining (Taylor filters). The practically clear amber-colored bag-liquor usually goes thence to the bone- char filters for its first decolorization, but often it is first sub- jected to a further treatment with precipitants and filter-pressed before going to the bone-char. The glucose is passed twice through the bone-char filters, the first passage follows bag-filtering, resulting in what is known as light liquor. This liquor is evaporated in a multiple-effect appara- tus to a density of about 30° Be., and again goes to the bone- char filters, when the product is known as heavy liquor. The practically colorless heavy liquor coming from the bone- char filters is now ready for the final boiling down in the vacuum- pans, whence it comes as finished glucose and is run into the barrels for shipment. Glucose as used for the manufacture of table sirups is usually known as mixing glucose. Such sirups are made from cane sirups, usually refinery molasses, or from white sugar and glucose in the proportion of 85 per cent of glucose to 15 per cent of cane sirup. Table salt and sometimes small quantities of vanillin are often added. The other principal uses of glucose are in the manufacture of jellies, preserves and in brewing, although its applications are multifarious in many industries where it does not enter as a food product, as for instance, it is used in enormous quantities to fill sole leather and tanning extracts. DEXTRIN AND BRITISH GUM. Artificial gum made from starch and known as dextrins and British gums are made in large quantities both in this country and Europe, and are employed in many ways as substitutes for natural gums, such as tragacanth or gum arabic. Enormous quantities of these starch gums are used in the textile industries, for envelopes and postage stamps. These products are made by heating (roasting) starch in revolving cylinders, which are heated directly by a furnace or by an oil- bath, or in shallow trays in shelf kilns. The temperatures used vary much according to the product desired, varying from 170 to 270° C. In making dextrins, lower temperatures are used and the starch is moistened with dilute acid, usually nitric, 0.12 per cent previously to heating, so that in the earlier stages of heating considerable hydrolysis takes place. In making British gums usually no acid is used, but the temperature employed is higher, and even in this process hydrolysis first takes place to some extent, owing to the moisture and acid naturally in the starch. The time of heating varies much according to the prod- STARCH, GLUCOSE, DEXTRIN AND GLUTEN 405 uct, white dextrins taking but two hours, while British gums are heated for fifteen hours or even longer. There are no exact standards for dextrins generally recognized, color and body of the mucilages which measured quantities of these gums make are usually the best means of their valuation. These products are not definite chemical compounds, neither are they made according to fixed methods of procedure. Often different prod- ucts are blended to give the properties desired. Little is known of the chemical constitution of these products, however much has been assumed. They contain some products of acid hydrolysis, it is true, but they are not in the main identical with products of acid hydrolysis. GLUTEN. The protein matter known as " gluten, " which forms the largest proportion of the organic material associated with starch, is necessarily removed or destroyed in the process of starch manufacture. By the more modern processes the gluten is saved and formerly these semi-liquid gluten deposits were sold to the neighboring farmers for immediate feeding to their cattle. Now, in the manufacture of corn starch the gluten which is settled out of the liquor coming from the starch runs is filtered in filter-presses, and the cake dried and pulverized, making a valuable cattle food, especially when mixed with the corn bran or similar material. CHAPTER XXII BEER, WINE AND LIQUOR BREWING is the process of preparing hopped, fermented beverages, such as lager beer, ale, stout, weiss beer, the materials usually employed being barley-malt, hops, and water. MALTING. This is the process of preparing cereals, usually barley, for brewing purposes. Barley is the favorite cereal employed, chiefly because the husk acts as an excellent filtering material in the mash-tun; its endosperm is readily modified and mellowed during growth, unlike corn; and it develops a sufficiency of enzymes during the malting process. MALTING OPERATIONS. Broadly these embrace every ma- nipulation from the moment the crude grain leaves the elevator or storehouse up to the time the finished malt is conveyed to the storage bin or to the hopper to be measured into the crusher mill of the brewery. In a more confined sense, as treated here, the term is applied only to the three main operations of steeping, germination and kiln-drying. Growth. Germination as conducted on a smooth floor, con- structed of cement for this purpose, is the traditional method, the process being called " flooring," " growing," or " germinat- ing." The modern methods, however, are based on artificial or forced aeration (pneumatic malting) either on a perforated floor or in revolving drums. Another important distinction is, that by the old method the work s almost entirely done by hand, whereas the improved methods may with much propriety be called mechanical malting, most of the work being done by machinery. Floor Malting. The barley from the bins is loaded on the conveyor and carried automatically to the cleaning machine. The offal goes to feed dealers. Steeping. From the cleaning machine the barley drops into the separator underneath. The different grades, two or three 406 BEER, WINE AND LIQUOR 407 in number, go to the automatic scales, and then reach the steep- ing tank, which should be half filled with water. At first, the water should stand 1 to 2 ft. above the barley when the tank is full. The skimmings are floated off or skimmed off with a ladle. They go to a separate bin or trough, and are dried and sold for feed. Change the water twice the first day and once a day thereafter. Steep for about forty-eight hours, modifying for dryness of air, hardness and temperature of water, type and condition of barley, etc. Germinating. The grain being fully steeped, the water is drained off at the bottom and the barley dropped on the malting floor; otherwise it is loaded on trucks and wheeled to the floor, where the grain is spread and leveled to a heap or " couch " of about 8 to 10 ins. Here it is turned from time to time by hand shovels and its height gradually increased and again reduced according 1 to conditions from about 14 ins. to 4 or 5 ins. The temperatures in the air should be about 50 to 60° F., in the growing malt couch about 75°, turning to prevent too high heats and to supply aeration. Growth takes about five days for barley of the Manchuria type and eight days for Bay Brewing and two- rowed types, like the Chevalier. When the endosperm has become mellow and acrospire is three-quarters up, the " green malt " is conveyed to the kiln, which usually has two or three floors heated by open fire assisted by closed heaters; hard coal, being smokeless, is commonly used for fuel. Kilning. By a fan installed above the upper floor air is sucked through the malt together with the products of coal combustion. The temperature is kepc at about 90° F. on the upper floor, and when hand dry, usually after twenty-four hours, the malt is dumped on the lower floor, where it is kept for about twelve hours at 120-130° F., where it is kept until practically dry, when it is heated to the final temperature of 150-155° F., for pale beers, 165-180° for darker beer, and up to 220° F. for beers of Munich character. BREWING MATERIALS. The materials commonly employed wherever beer is produced are hops, malt and water. In some countries, like England, sugars and other adjuncts are used in part with malt; in the United States corn is commonly employed besides rice and sugars. In Germany the employment of any sub- stitutes for or adjuncts to malt is prohibited. Barley is the dis- tinctive cereal that furnishes malt, the exception being wheat used for weiss-beer malt. 408 ELEMENTS OF INDUSTRIAL CHEMISTRY Malt and Cereals. Malt is produced from barley by the proc- esses of cleaning, steeping in water, germinating on the floor or in compartments or drums, kiln drying. Properties of Matt. The berries should be of uniform size and shape; husk and endosperm of light color for pale beers; it should be free from other grain like wheat or oats, or seeds like mustard, rape; odor aromatic, not musty; growth uniform with about 90 per cent of acrospire three-quarters up; condition of endosperm mellow, not flinty; laboratory yield on dry basis about 72 to 74; moisture content not over 6 per cent, lest slack ness ensue; strong diastatic and peptic power for proper inver sion of starch and albumen; bushel weight not less than 34 nor more than 38 lbs. Corn is employed, with germ and husk more or less removed, in the form of grits or meal in a separate cooker or in the form of flakes in the mash-tun; rice, either broken or as meal, in the cooker; wheat in flaked condition in the mash-tun or crushed (by means of malt mill) in cooker. Malt yields about 64 to 70 per cent of extract in the brewery, of which 4 to 5 per cent are albuminoids; rice about 75 to 80 per cent; corn about 75 to 78 per cent; wheat about 65 to 70 per cent, of which 2 to 3 is albumen; rice and corn yield practically no albumen. The employment of unmalted cereals like rice and corn offers a number of advantages. They can generally be obtained at a lower price and yield more extract than malt. They lend themselves better to the production of beers of Bohemian or Vienna types than all malt, because American malt generally yields more albumen to wort and beer than European malts, due to higher albumen content of American barley of Manchuria type. Amer- ican all-malt beers are therefore apt to be more satiating than Bohemian beers with their lower albumen content. The result- ant beers are of paler color, of greater stability when pasteurized, and their brilliancy less affected by low temperatures. The employment of wheat may not be more economical, nor are the wheat beers more stable or less sensitive to low tem- peratures than all-malt beers. They have a peculiar palatable- ness that recommends them in some localities. Commercial glucose and other brewing sugars are prepared from the starch of corn through inversion by acids at high heats (under pressure). They contain dextrose and dextrin in vary- ing quantities. BEER, WINE AND LIQUOR 409 Other Adjuncts. Dark malts. For preparing a beer of dark color a malt may be used which has been subjected to special treatment in the kiln, so as to acquire a dark color, such as caramel malt, the husk of which is yellowish brown, wnile the endosperm has a decidedly brown color. In its preparation, ordinary malt of good quality is steeped for a while, so as to take up a certain amount of moisture. It is then dried, and heated in suitable vessels, first to a comparatively low temperature, in order to promote the formation of sugar, and later to higher temperatures, at which the sugar is caramelized. Black malt is dried at higher temperatures, so that both the husk and the endosperm possess a blackish-brown color. It does not have the pleasant caramel taste of caramel malt. The coloring power is very great. Malt color is an extract of black malt, filtered and evaporated to a sirupy consistency. Roasted corn is prepared from corn in the same manner as black malt from barley, i.e., by heating to higher temperatures. Its coloring power equals that of black malt. Hops. Hops as they are used in the brewery are cone-shaped formations, representing clusters of blossoms of the female hop plant. From forty to sixty flowers are grouped together on a central spindle, which is zig-zag shaped, forming a so-called hop cone or the umbel of the hop. At the time of maturity the seed of the hops and the whole lower and inner parts of the bracts are covered with a fine light- yellow dust, consisting of minute granules of lupulin, which con- tain both the bitter and aromatic principles of the hops, viz., the hop oils and resins, besides hop tannin, hop bitter acids, hop wax, nitrogenous bodies, carbohydrates and mineral substances, an enzyme (diastase) which is of special importance in ale brew- ing. Mashing. Mashing is the process of extracting the good by mixing them with water at suitable temperatures and in proper relative quantities, preparatory to boiling in the kettle. Chemically it proceeds in the main by the inversion of the starch into maltose, malto-dextrin, and dextrin, and the modi- fication of the insoluble albuminoids into a soluble form. These changes are brought about by the agency of two substances which are contained in the malt, and begin operations when the malt is mixed with water at definite temperatures. These substances are called diastase and peptase. They were formerly called chemical ferments, as distinguished from the 410 ELEMENTS OF INDUSTRIAL CHEMISTRY organic ferments, which are responsible for fermentation. At the present day the term enzymes, or soluble ferments, is more commonly applied to them. It is the function of the diastase to invert the starch, of the peptase to modify the albuminoids of malt as above indicated. The amounts, both absolute and relative, of dextrin, malto- dextrin and maltose, as well as of the modified albuminoids like albumoses, peptones and amides, finally present in the wort, are materially affected by the conditions under which the enzymes do their work. Hence, it is in the power of the brewer to control the, composition of the wort, within certain limits, by modifying such conditions. Boiling the Wort. The wort obtained by mashing is boiled for a certain period for the purpose of eliminating or rendering harmless certain undesirable constituents, Hke coagulable albu- minoids, and introducing other new bodies, like hop resin and hop oil, by extraction from the hops. Besides, during heating and boiling the wort assumes a darker shade, due to carmelization of the sugars; water evaporates, resulting in a denser liquid, and the tannic acid of the hops coagulates an additional quantity of undesirable albumen, this coagulation aiding in clarifying the wort and causing it to " break." The wort should not be allowed to rest longer than fifteen minutes, as a dark color or rank, bitter taste may result if wort is left in contact with hops too long. The hop-jack is pro- vided with a false bottom, through which the wort is drained into a pump that delivers it to the coolers. The hops remaining on the false bottom are sparged with hot water to wash out the wort they contain. If the wort remains in hop-jack very long, or if the spent hops are pressed out to obtain the wort, a rank bitter taste of the beer is apt to result. Cooling. The wort reaches the surface cooler, a large, shallow iron pan, and remains here a short period for the purpose of preliminary cooling. The wort should be cooled to 145° F., and not lower, on the surface cooler, and receive proper aeration during cooling, avoiding all sources of contamination in the meantime. Aeration of the wort during cooling has the effect of further precipitating undesirable albuminoids. Besides, the wort absorbs air, which is utilized by the yeast later on. Pitching with yeast. Fermentation is induced in the wort by adding yeast properly prepared, which operation is termed " pitching." The common practice is to mix the yeast with an BEER, WINE AND LIQUOR 411 equal quantity of finished wort or boiled first wort of about 55-60° F., rouse well to insure aeration and breaking up of cell aggregations, transfer to settling tank when the mass is in fer- mentation, mixing with it the wort as the latter runs from the cooler. Fermentation Phenomena. Within fifteen or twenty-four hours, according to the pitching temperature, little white bubbles appear around the sides of the vessel. The beer at this time is covered with a dark head of a thick consistency, composed largely of albuminoid matter, coagulated during the boiling period (sludge). The head of impurities being skimmed off, the whole surface is found to become quickly covered with a fine white froth (" whitening over "), rather higher around the rim than in the middle, denoting that carbonic acid gas is escaping through the fermentation of the sugar (maltose) . Kraeusen. The head of froth begins to move from the sides of the vessel to the middle, and assume a frizzled appearance, small cockle-shaped mounds beginning to rise all over the surface. At the expiration of twenty to thirty-six hours after pitching, the surface should be early and pure white ("young kraeusen"). From the time the froth head begins to move toward the middle, fermentation becomes more active, the head rising all the time ("high kraeusen"). At the same time the temperature rises, slowly at first, more rapidly as the activity of fermentation in- creases, while the saccharometer indication or density decreases more rapidly, the drop amounting to one-fourth to one-half of one per cent a day in the early part, and reaching one to one and one-half toward the high kraeusen stage. The curly head of froth turns a darker color while rising in height. The high kraeusen stage is reached seventy to eighty hours after pitching and is maintained for a period of forty-eight to seventy-two hours, varying according to different influences. During this time the fermenting beer is kept at a certain low temperature, 48 to 50° F., and as high as 58° F., by means of attemperators, and when the head begins to collapse is cooled slowly to 39° F. The saccharometer falls more slowly as the end of the principal fermentation draws near. When the end is reached, the fall of the saccharometer is commonly fa to -fa per cent in cwenty-four hours. The yeast, which had been kept in suspension during fer- mentation through the escape of carbonic acid gas, should now be found settled on the bottom of the fermenter: the amount 412 ELEMENTS OF INDUSTRIAL CHEMISTRY being about three to four times the quantity used for pitch- ing. Tanking the Beer. The beer is brought from the fermenting vat to the stock tank either at the temperature to which it has been cooled in the ferment er, and then it undergoes a secondary fermentation, or it is further chilled on its way to the stock cellar, passing it through a cooler, in which case no secondary fermentation is anticipated and the beer should reach the stock tank thoroughly fermented. Storage is that stage in which the beer is kept after the con- clusion of the primary fermentation and prior to final clarifica- tion for the trade package. The objects of resting the beer are to eliminate certain sus- pended matter, like yeast, thereby securing greater clearness, and certain objectionable matters, like albumins, thereby securing greater durability, especially in pasteurized bottled goods. During the storage period there should be a slight progiess of secondary or after-fermentation, unless final attenuation was reached previously. The residue of maltose and part of the maltodextrin are fermented by slow degrees, the amounts of carbonic acid and alcohol increasing. The yeast settles the more quickly the less sugar there is present and the smaller the storage vats; the albumins are the more thoroughly eliminated the better the mash was peptonized, the lower the storage temperature, and the longer the period of storage. Hence, long storage at low temperatures enhances the stability of beer after pasteurization. Starch particles do not settle on storage. Nor can dependence be placed on improving the beer through long storage in respect to number of bacteria it contains. On the contrary, bacteria may increase during storage. Low temperatures while the beer is in storage are necessary to precipitate the albumins and to check the development of bacteria. The storage cellar should be kept as near to the freezing point as possible. When sufficiently matured in storage, the beer is run or pumped into chip casks, so called from a method of clarifying beer by means of chips. Treatment in the chip cellar has a twofold object: 1. To impart to the beer the necessary life, that is, a suffi- cient amount of carbonic acid gas, so that it will foam properly when tapped. This is done: BEER, WINE AND LIQUOR 413 a. by kraeusening and bunging, or b. by charging with carbonic acid gas directly (carbonating) , or c. by both kraeusening and carbonating. 2. To make the beer brilliant. This is done: a. by the addition of chips; b. by the addition of isinglass ; c. by filtration. Kraeusening. This consists in the addition of kraeusen beer> that is, young beer in the first, or kraeusen stage of fermentation, twenty-four to forty-four hours after pitching, the amount being about 15 per cent for home draught beer, 10 per cent for export draught or bottle beer, or 5 per cent when beer is carbonated. A few days after the kraeusen have been added the finings are intro- duced and the cask is bunged, to prevent the escape of the gas generated by the kraeusen, its accumulation causing a pressure which is termed bunging "pressure and which is allowed to rise to about 5 lbs. Carbonating. Carbonic acid fermentation gas may be intro- duced into the beer at any stage after fermentation, but usually this is done while the beer is being transferred from the chip cask to the racking bench and before it reaches the filter. When beers are carbonated they are either not kraeusened at all or only with relatively small quantities of kraeusen — about 5 or 6 per cent. The gas is introduced either on the pressure principle by spraying the beer through a compressed atmosphere of gas or on the aspirator or injector principle, by forcing the gas into the beer, usually in a conduit while in motion. Clarification. Matter remaining in suspension at the end of the storage period is eliminated by mechanical means. First among them is the introduction of chips. Beer chips or clarifying chips are strips of wood, usually of beech or maple, so cut as to present a maximum of surface with a minimum of volume and weight. The chips are spread in the bottom of the chip cask, where they retain particles in suspension, reaching them as well as the sedimentation caused by the employment of isinglass. Chips must be carefully prepared by boiling in water, with an addition of soda. Fining the Beer. Brewers' finings are prepared from so-called isinglass, obtained either from fish through cleaning, rolling and drying the bladder, or from hide of calf. The finings may be pre- 414 ELEMENTS OF INDUSTRIAL CHEMISTRY pared on the cold or warm plan, their efficiency depending upon the amount of gelatinous substance the isinglass yields and which in flocculent form distributes through the beer, enveloping the suspended particles and carrying them to the bottom. One pound of isinglass is sufficient for one hundred to five hundred barrels of beer. Filtration. The process of filtering beer consists in forcing the beer on its way from the chip cask to racking apparatus, generally by means of air pressure applied at the chip cask, or through a pressure regulator pump interpolated between chip cask and filter, through one or more layers of compressed fibrous material, called filter mass, which commonly consists of cotton fiber. Beer should always pass through the filter under back pressure, as it will otherwise foam to such an extent as to pre- clude the proper filling of the trade packages. It should stand in a cold place, if practicable, in the chip cellar. Back -pressure Racking. The principle of back-pressure rack- ing is to create in the delivery package a back pressure suffi- ciently high to prevent foaming of the beer, so as to permit of readily filling the package without loss of time and without the foaming and loss of beer accompanying the practice of " gut rack- ing " which formerly obtained. WINE. The Grapes. The quality of a wine depends mainly upon the quality of the grapes from which it is made, and the latter is determined by a number of factors, such as variety of grapes, treatment of the vines, soil and its cultivation, climatic conditions and the degree of ripeness which the grapes are allowed to reach. It is only where a suitable variety of grape is grown under especially favorable conditions as to soil and climate that the high- grade wines can be produced. Under other conditions the iden- tical grape variety may give a wine of a distinctly different character. The Riesling grape, when growm in California, is different from the Riesling that finds ideal conditions for its devel- opment in the temperate climate of the sunny hills along the Rhine, and the name Riesling on the label of a California wine therefore invites a comparison that cannot but result in adverse criticism. The wine growers of each territory, when selecting and developing those varieties of grapes that are best suited to local conditions, and modifying their methods accordingly, may gradually develop wine types of their own to be judged entirely upon their own merits. BEER, WINE AND LIQUOR 415 It is important that the grapes be picked at the proper time, which usually means when fully ripe. If picked at an earlier stage they give a must containing less sugar but richer in acids. For this reason early picking is sometimes resorted to in southern countries, where the hot and dry climate tends to produce little acid and much sugar. Over-ripeness of the grapes is undesirable, as it will cause them to shrink and their skin to burst, laying open the juice to the dissolving action of rain and dew and offering breeding places to dangerous " disease " germs. The weather during the picking is not without importance. Rain will, to some extent, dilute the must; heat will accelerate, while cold will retard the subsequent fermentation. Stemming, Crushing and Pressing. After being gathered and carted to the winery, the grapes are to be prepared for the fer- mentation as quickly as possible. Any delay is likely to detract from the quality of the resulting wine. If the production of white wine is intended, the grapes, which may be either red or colorless, are crushed and pressed, only the juice (must) being fermented; if red wine is to be produced red grapes are stemmed and crushed, the whole pulp being filled into fermenting vats, where the color- ing matter is extracted during fermentation. In some cases the stems are left in the fermenting pulp, but as a rule they are removed either before or after the crushing. The device used for stemming may consist in its simplest form of a wire-screen, with meshes of a size to permit the grapes but not the stems to go through, over which the grapes are pushed by hand with a rake. Another device, intended for machine power, consists of a horizontal perforated cylinder in which a shaft with helically arranged arms revolves, thereby carrying the stems toward one end and causing the grapes to fall through the perforations. The machine in wmich the grapes are crushed usually consists of a hopper feeding the grapes to a pair of adjustable grooved rollers revolving in opposite directions and with unequal speed. The purpose is thoroughly to open up all of the grapes without crushing the seeds, from which undesirable substances would otherwise be extracted, whence the rollers are adjusted accord- ingly. Part of the must is often allowed to drain off from the crushed grapes by gravity alone and may be fermented sepa- rately and is superior to the rest of the must that is obtained by pressing. The winepresses are mostly ordinary screw-presses; sometimes, 416 ELEMENTS OF INDUSTKIAL CHEMISTEY however, hydraulic presses are used. The crushed grapes are spread in a uniform layer over the press-bed and subjected to a gradually increasing pressure. Too strong pressure should not be applied at once, lest the yield be diminished. As already stated the pressing of white wines takes place before, that of red wines after, fermentation. The Must. The grape juice is a watery solution, the main constituents of which are: 1. Sugar; 4. Flavoring substances; 2. Organic acids; 5. Pectine and mucilaginous substances; 3. Albuminoids; 6. Mineral substances. 1. The sugar during fermentation is split up into about equal parts of alcohol and carbonic acid, and only very little sugar (less than 0.15 per cent) should be left in ordinary dry wines. A must containing 16 to 17 per cent sugar will produce a table wine with an alcoholic strength of 8 to 8.5 per cent by weight; musts containing less sugar produce the light, ordinary wines; those containing more sugar result in the heavier high-grade wines. 2. The organic acids, tartaric and malic, although present in comparatively small quantities, are very essential constituents of the must. The tartaric acid mainly occurs in combination with potassium as tartrate (bitartrate of potassium), which is pre- cipitated to a large extent during the fermentation. A part of the acids is also consumed by the yeast and by certain bacteria, which accounts for the fact that a wine has less acidity than the corresponding must. The total acidity of must or wine is usually given as the apparent percentage of free tartaric acid. To make a wine palatable its acidity must be in proper ratio to its alcoholic strength and palatableness. A light wine without prominent flavor and body may appear fully harmonious as to taste with an acidity of only 0.4 per cent, but a heavier, highly flavored, wine would taste quite flat when possessed of this same acidity and may require as much as 1.0 per cent acidity to appear harmonious. A must usually loses from 0.2 to 0.6 per cent in acidity during its transformation into wine. 3. The must can contain up to about 1 per cent of albuminoids, of which only approximately one-half remains in the wine, the rest being partly utilized as nourishment by the yeast, and partlv precipitated during the fermentation. BEER, WINE AND LIQUOR 417 4. The flavoring substances of the must, upon which its quality largely depends, are present in too small quantity to be determi- nable by chemical analysis, and we possess at the present time only scant knowledge of their chemical nature. These flavoring substances increase during fermentation, the fermented must containing: (1) Those originally present in the must ; (2) others formed during the fermentation, probably mainly by decomposition of certain albuminoids (amino-acids) contained in the must, and (3) the specific flavoring substances produced by the different varieties of yeast irrespective of composition of the must. 5. The pectine and mucilaginous substances causing the thick consistency of the must are practically all precipitated during the fermentation, as they are insoluble in dilute alcohol. 6. In a normal must is found from 0.3 to 0.5 per cent of mineral substances (ash), the amount of w T hich considerably decreases during the fermentation owdng to the precipitation of potassium in the form of tartar. The wine maker tests his must to determine approximately the sugar and acidity of an average sample. The sugar is deter- mined by means of areometers, such as Oechsle's must scale, indi- cating how many grains one liter of must weighs more than one liter of water, or Balling's saccharometer, indicating the per- centage of solids in solution. Degrees Oechsle divided by 5, or per cent Balling multiplied by f gives the sugar content in per cent of an ordinary must with sufficient accuracy for practical purposes. The acidity is measured by titration with standard- ized alkaline solutions. Knowing the ratio of sugar to acidity the wine maker is in a position to carry out the subsequent opera- tions with a view 7 to either checking or facilitating the decrease in acidity according to the requirements. A direct correction as to composition may also be found desirable. If lacking in acidity the must can be corrected by the admixture of less ripe grapes or by the addition of tartaric acid. The addition of gypsum, which is sometimes used, especially in making red w r ines, has a similar effect, the gypsum reacting upon the tartar so as to form insoluble calcium tartrate and bisulphate of potassium, which latter substance, unlike the tartar, remains dissolved in the wine. This method, the so-called plastering, can only be used to a limited extent, since the laws of most wine- producing countries fix a maximum limit for sulphates contained in unadulterated wine. 418 ELEMENTS OF INDUSTRIAL CHEMISTRY If the must is too rich in acids, the acidity can be reduced by dilution with water and the proper sugar content eventually restored by addition of pure cane or grape sugar. This process, known as gallizing, is used to some extent in northern countries, especially for white wines, and is generally considered legitimate, provided it is carried out so as actually to improve, or to render marketable, the product and not with a view unduly to increase its quantity. The Fermentation. When left to itself the must will soon begin fermenting. It grows quite turbid, gas bubbles rise to the sur- face, the temperature rises and the viscosity and specific gravity decrease. At the same time the sweet taste gradually changes into a vinous one and a distinct flavor develops. Toward the end of the fermentation the turbidity gradually disappears and the completed fermentation leaves the young wine in a limpid state on top of a heavy sediment. These changes are brought about by certain microscopical plants that are always present on the skins of ripe grapes. Among them the yeasts which cause the alcoholic fermentation, splitting up sugar into alcohol and carbolic acid, are desirable and indis- pensable, while others, such as mycoderma and various bacteria, are undesirable disease germs. Between the microorganisms a struggle for life goes on in the must, each one striving to utilize the nourishment on hand for its own growth and producing substances that are injurious to its competitors. By far the most important task of the wine maker is to assist the yeast in this struggle by offering it the most favor- able conditions for its activity. His aim is to make the yeast ferment the sugar as completely as possible, which not only means little nourishment left for other organisms, but also a high percent- age of alcohol prohibiting their growth. Incomplete fermentation on the other hand results in a weak and unstable wine subject to a variety of undesirable changes. The Wine-yeasts. The alcoholic fermentation of the must is caused by small, usually unicellular budding fungi, mostly belong- ing to the different varieties of Saccharomyces ellipsoideus. Their principal breeding places in nature are the ripe juicy fruits, where they multiply abundantly during the fall. Some of them pene- trate with the rain to a certain depth into the soil, where a suf- ficient number keep alive over winter to repopulate the fruits of the following year, to which they are carried by insects, rain- splashes or the wind. Their perpetuation is facilitated by their BEER, WINE AND LIQUOR 419 power of forming spores, small resistant cells appearing under certain conditions within the vegetative cells. The yeast cells contain an enzyme, the zymase, which in contact with dissolved sugar transforms it into alcohol and car- bonic acid. This fermentation proceeds most satisfactorily at medium temperatures, the yeast becoming temporarily inactive at a few degrees above the freezing point of the water and perma- nently weakened at about 100° F. Even the most vigorous yeast can only produce about 13 per cent of alcohol by weight and this only under exceptionally favorable conditions. Besides the main products of the alcoholic fermentation smaller quantities of glycerol, succinic acid and fusel oils are also produced by the yeast during fermentation. Apart from the glycerol, that may — as far as our present knowledge goes — be derived from the sugar, the other by-products have recently been shown to originate from amino-acids (e.g., succinic acid from glutamic acid and amyl-alcohol from leucine) the nitrogen being utilized by the yeast iu the form of ammonia for building up the albumen of its own body. In all probability flavoring substances are formed by a similar process from other amino-acids, the primary products being various alcohols and acids, which during the ripening of the wine are further transformed through oxi- dation and esterification. White Wines. The white wines are produced by fermen- tation of grape juice that has been separated from the skins, seeds and stems. A fermentation of this kind offers comparatively little difficulty, but the resulting wine is decidedly more delicate than those fermented on the skins, whence its subsequent treat- ment and proper ripening require greater care. The fermentation is usually carried on in casks that are filled to -J-^- of their capacity with grape juice and the bung hole is closed so as to allow the carbonic acid to escape but no air to enter. The duration of the fermentation is from one to two weeks, depending on the temperature, which usually is 60-70° F., and on the quantity of yeast originally present. At the end of the fer- mentation the yeast sediment is sometimes stirred up again in order to facilitate the complete splitting up of the sugar and the reduction of acidity. After the fermentation is over the wine is drawn from the lees into another cask in which some sulphur has been burned to check the further activity of microorganisms. This cask is completely filled, tightly bunged and as a rule kept at a temperature of 50- 420 ELEMENTS OF INDUSTRIAL CHEMISTRY 55° F. Before the rising temperature of the following spring causes a slight revival of the fermentation, the wine is racked off from the sediment once more, and this process repeated several times during the subsequent ripening period. At each racking an oxidation takes place resulting in precipitation of certain albuminoids and further development of the flavor, until finally the wine has become sufficiently stable to be filled into bottles. In the ordinary grades of wine this ripening is generally more or less forced by means of a more thorough aeration during the racking, artificial clarification (filtration or use of finings), and, eventually pasteurization. The simplest form of wine filter is a cylindric or conical linen bag into which the wine is poured back until it runs clear. The more modern filters are closed so as to protect the wine from the air. Their filtering material is either pure cellulose or paper- pulp, packed into one or more filtering chambers or especially prepared asbestos-wool stirred up with a smaller part of the wine and pumped into the filter, where it deposits as a uniform layer on walls formed of fine wire screens. Finings are added to the wine in order to produce a very finely distributed sediment of higher specific gravity which will gradually settle to the bottom, carrying with it all suspended solid particles. For fining white wines isinglass is commonly used. It is soaked in water and at last in wine until nearly transparent and then vigorously beaten with some more wine eventually under addition of tartaric acid, filtered through linen and thoroughly distributed into the wine in the cask. One ounce of isinglass can generally fine 200-500 gallons of wine within 8-10 days. Red Wines. The red wines derive their characteristics from being fermented in contact with the skins of red grapes, from which they extract not only coloring matter but also a variety of other substances, especially tannins. Normal red wines con- tain from 0.1 to 0.3 per cent of tannin, while the percentage of this substance in white wine does not as a rule exceed 0.02 to 0.04 per cent. Owing to this high content of tannin the ripen'ng of red wines is a comparatively easy matter once the fermentat on has been properly carried through, but the presence of the skins at the fermentation on the other hand gives rise to several difficul- ties during this process. The carbonic acid carries the skins to the surface, where they form the so-called cap, which must be pushed down repeatedly in order to insure proper extraction and uniformity of fermentation. BEER, WINE AND LIQUOR 421 Closed casks are therefore less suitable and in the open tubs, which are generally used, there is great danger, however, of acetincation owing to the free exposure of the cap to the air. To overcome these difficulties the fermenting tubs are often provided with removable grates that are held in horizontal posi- tion about 5 ins. below the surface of the liquid, thus prohibiting the skins from rising to the surface. To insure proper uniformity the wine is draw T n off at intervals from the bottom of the tubs and pumped back to the surface. The temperature during fermentation of red wine is usually 65 to 85° F. As red wines are mainly produced in southern countries it is often difficult to prevent the temperature from rising too high, a considerable amount of heat being generated by the decomposition of the sugar. Too high temperature not only facilitates the growth of various bacteria but also prevents the yeast from completing the fermentation, the result being a wine of poor quality and easily subject to further deterioration. Artificial cooling is therefore often resorted to, water being circulated through cooling coils in the tubs or the wine being pumped through enclosed coolers. After being fermented the red w T ine is drawn off into casks, w T hich, however, are only sulphured in exceptional cases, because most red wines do not need this protection and would be more or less bleached by the sulphurous acid. Red wines are ripened in practically the same way as white wines, but less time and fewer rackings are required to render them sufficiently stable for bottling. The red wines are mostly fined with gelatine or white of egg. The gelatine is soaked in water over night, dissolved in wine by gentle heating, cooled, stirred up with some more wine and added to the cask. One ounce of gelatine is required for 50-120 gallons of wine. Whites of eggs are often used to fine the better grades of red wine, one white for every 8-12 gallons. They are first beaten to a foam, pressed through a heavy linen, and then stirred up with some of the wine before being added to its bulk. Sweet and Dessert Wines. The white and red wines referred to above are all dry, i.e., practically all of their sugar having been fermented. The sweet wines and the dessert wines on the other hand contain unfermented sugar besides a high or even very high percentage of alcohol. The typical sweet wines, such as Auslese, Rhine wine, sauterne, or tokay, contain much sugar, but their alcohol is produced by fermentation and con- 422 ELEMENTS OF INDUSTRIAL CHEMISTRY sequently does not exceed 13 per cent by weight. The dessert wines, such as port, sherry, madeira and malaga, are less sweet, but generally contain from 15 to 20 per cent by weight of alcohol, part of which has been artificially added. The Auslese wines and sauternes are produced from grapes attacked by a certain mold, Botrytis cinerea, which finds favorable conditions for its growth in a foggy, cool climate without too much rain. It causes the grapes to shrink and partly to dry up, the must being accordingly more concentrated and possessed of a peculiarly fine flavor. The fermentation is carried out with a view to produce enough alcohol to prevent further changes, but since sugar is left unfermented these wines are prone to after fermentation, and as a rule need heavy sulphuring to become stable. In certain territories the dry and warm climate allows the grapes to dry up similar to raisins before they are picked. These yield a very concentrated must. The tokay wines of Hungary are made from such grapes, extracted with normally fermented dry wines and pressed. Imitated tokay is made in a similar way from ordinary dried raisins or from must concentrated by boiling in vacuo. The various dessert wines contain more alcohol than can be produced by fermentation. An addition of alcohol is therefore necessary, and is often combined with an addition of condensed must or sugar. The alcohol may be added either at the end of the fermentation or at an earlier stage, in the latter case pre- venting part of the sugar contained in the must from being fermented. The addition is often made step by step, part of the total amount required being added at each racking and thor- oughly mixed with the wine. During the ripening period the dessert wines are kept at a comparatively high temperature and freely aerated. This results in the development of the peculiar flavor known as madeira flavor. Sparkling Wines. The sparkling wines are produced from either red or colorless grapes, the juice alone being fermented as usual for dry white wines. After being drawn off from the lees the wine is racked once more, a too high content of albuminoids being eventually decreased by an addition of tannin. The wine is blended in large vats or casks with a view to produce a uniform product from one year to another, and enough sugar solution is added so that a pressure of about 5 atmospheres can develop during the subsequent fermentation in bottles. Furthermore BEER, WINE AND LIQUOR 423 a culture of selected pure yeast is often added, and the wine is then bottled and corked, preferably in the spring, because the rising temperature facilitates fermentation. When bottled the wine has a temperature of 65-72° F., but the bottles are kept at about 50° F., when the fermentation has started. This tem- perature must be kept as constant as possible to avoid breakage. The duration of the bottle fermentation varies from one-half to two years. When the proper pressure is reached the bottles are placed in a slanting position on special stands, their necks being a little lower than their bottoms. A short snaking and turning movement is imparted to them once a day during about six weeks while they are gradually raised to a vertical position neck down. In this way the yeast sediment is carried down on the cork, leav- ing the wine entirely clear. This process can be greatly facili- tated by the use of a proper variety of yeast, i.e., one combin- ing a strong fermenting power with a tendency to grow in larger clusters. The bottles are now taken to the uncorking room and event- ually cooled to bind the carbonic acid more firmly. The uncork- ing requires a good deal of skill. The operator holds the bottle in a slanting position and gradually loosens the cork until it is thrown out by the pressure together with the whole sediment. At the same instant the bottle must be turned upright and preliminarily closed. Some sugar solution is added before the bottles are finally corked, the quantity varying greatly according to the requirements of the trade. The sugar solution is thoroughly distributed by shaking and the bottles preferably kept in stock for some time before being consumed in order that the taste be more harmonious and the carbonic acid more permanently bound. Imitation champagne is made by saturating white wine with carbonic acid under pressure in a suitable apparatus, but such sparkling wines are generally lacking in life and when poured into the glass do not show the same permanent sparkling as those made by the slow process of bottle fermentation. DISTILLED LIQUORS. Distilled liquors differ greatly in flavor and general character, being influenced in these respects by the materials and the methods employed in their production. Their names vary according to the nation producing them. Among the best known distilled or spirituous liquors are: Whiskey. Under the term whiskey is understood the potable spirit distilled from fermented mashes, made either from malt alone or a mixture of malt and unmalted cereals. The latter 424 ELEMENTS OF INDUSTRIAL CHEMISTRY usually are barley, lye, maize (Indian corn), oats and wheat. In some countries, chiefly Germany, potatoes are used. The malted cereals generally are barley malt, rye malt, wheat malt, and in a few instances oat malt. Genuine whiskies are of three different types: American, Scotch, and Irish. They differ vastly in flavor, body and color. American Whiskey. In the United States two distinctive types of whiskey are produced, namely, Rye and Bourbon. The grain used for manufacturing Rye whiskey is a mixture of rye or barley malt and unmalted rye. Bourbon whiskey is made from barley malt or wheat malt and maize (Indian corn) . The quantity of malt used amounts to from 10 to 15 per cent of the total weight of the materials in the lower grades of whiskies, and from 20 to 50 per cent in the better grades. Few whiskies are made from malt alone. The taste and general character of the different whiskies vary according to the materials employed, their quality — with special reference to the malt — and to the methods of mashing, fermenta- tion, distillation and aging of the distilled liquor. The finer the quality of the materials and the higher the percentage of malt, the better will the taste and flavor of the product be. Scotch Whiskey. Two different types of whiskey are made in Scotland. The one that is the characteristic Scotch whiskey is made from barley malt, and is usually termed pot-still whiskey, owing to the old-fashioned style of still used in its distillation. The other type is called patent -still, or grain whiskey. It is made from barley malt and unmalted cereals, mostfy corn imported from the United States. Rye and oats also are used. The genuine Scotch whiskies are characterized by a peculiar smoky flavor and taste, which originate from the malt. This is due to the employment of various kinds of peat as fuel for cur- ing, namely kiln-drying, the malt. This peculiarity distinguishes the genuine Scotch whiskies from all other types. They are generally stored about five years, or longer, during which time the whiskey acquires a rich, mellow taste and improves greatly in flavor. Irish Whiskey. Most of the Irish whiskey is of the pot- still type. It is usually prepared from 30 to 50 per cent barley malt, the remainder being rye, barley, oats, wheat or a mixture thereof. The malt is not peat cured and the resulting whiskies have a characteristic clean flavor and an ethereal bouquet. They are very " dry," namely alcoholic in taste. BEER, WINE AND LIQUOR 425 Kornbranntwein and Schnapps. These two liquors represent the most commonly employed distilled products in Germany. The former is prepared from malt and unmalted cereals, usually rye. Sometimes maize is used and very seldom wheat. The general process of manufacture is similar in principle to that employed for whiskey. Schnapps is usually obtained by diluting rectified alcohol manufactured from potatoes. The potatoes, after cleaning, are placed in large converters, mixed with the necessary quantity of water and heated under a pressure of 30-60 pounds, in order to pastify the starch. The mash is then cooled and a small per- centage of malt, often green malt, added, so as to invert the pastified starch. After inversion is complete, the fermentation is conducted in the same way as for whiskey. The process of distillation is such that a rectified alcohol results. Brandy. Under the name of brandy is understood those distilled liquors obtained by the distillation of grape wines, wine- lees or grape pomace. The finest brandy on the market is the so-called cognac. It represents the brandy distilled from the grape wines grown in the department of Charente, France. The town of Cognac is situated here and is the sales-point for the brandy made in this vicinity. France, with its numerous vine- yards, is the home of brandy, but considerable quantities are now being prepared in Algiers and in the United States, principally California. Genuine brandy, being prepared from the finest and purest fermented material, namely, grape wine, is conceded to be the best distilled liquor known. It is characterized by its very fine, smooth alcoholic taste and exquisite flavor or aroma. It possesses a rich golden yellow color and contains from 45 to 55 per cent of alcohol by volume. Different brandies vary in taste and flavor, and the best results are obtained when they are blended together by manufacturers or dealers skilled in this art. Gin. The word gin is a shortened form of Geneva, which is derived from the old French word " Genevre," namely juniper. It is the spirit distilled from a mash prepared from malt together with unmalted cereals, usually rye or barley, and is flavored by an addition of juniper berries during the rectification of the distillate. Some distillers at the same time also add a very slight amount of oil of turpentine and hops, in order to obtain a more characteristic flavor. Gin originated in Holland, and even to-day the finest product 426 ELEMENTS OF INDUSTRIAL CHEMISTRY is produced in Schiedam, Holland, and bears the name of " Schie- dam Schnapps." In time it was imitated extensively by English distillers and such gin is sold under the name of " London Gin." Genuine gin is a colorless liquid of delicate flavor and contains about 52 per cent of alcohol by volume. It is extensively imi- tated, by flavoring diluted alcohol with various essential oils, but such concoctions are decidedly inferior in eveiy respect to the genuine article. Rum. Among the distilled liquors consumed most commonly, rum has by far the highest alcohol content. A genuine rum never contains less than 70 per cent alcohol by weight (about 78 per cent by volume) and sometimes it is as high as 77 per cent. Rum is manufactured in Jamaica and other West Indies islands, some of the Southern States of the United States, Brazil, Madagascar, East India and some of the Indies islands; in fact in any region where sugar cane is cultivated extensively. The Jamaica rum has the reputation of being the finest in quality. The materials employed for preparing rum are the molasses, the skimmings (scum or foam) of the sugar kettles and the juice of the sugar-cane. The higher grades of rum are made from molasses, cane-sugar juice and only very little from the skimmings. Lower grades, often called " nigger rum," are prepared chiefly from the skimmings and other offal products obtained during the boiling and concentrating of the sugar-cane juice when manu- facturing sugar. Only little good molasses is employed. Such rum has a pronounced burnt, sourish taste and its flavor is coarse and rank. Slibowitz. This liquor is obtained by fermenting crushed plums and distilling the alcohol obtained by the fermentation. It is practically colorless and possesses a very clean alcoholic taste and odor. Practically no flavor of the plums (prunes) from which it was prepared is noticeable. Slibowitz is made by very many farmers, especially in Hungary and Servia, who use it as the household liquor. Arrack. The genuine arrack is a type of brandy containing about the same amount of alcohol as found in rum, namely 70 to 80 per cent by volume. It is prepared mostly in Siam, but also in East India, Java and adjacent localities, as well as in Jamaica. The materials employed are either (1) toddy, or palm wine, (2) rice and toddy, (3) rice and molasses, with or without an addition of toddy. Toddy, or palm -wine, is obtained by fermenting the sugary BEEE, WINE AND LIQUOR 427 juice of the cocoanut palm. This liquid is subjected to dis- tillation in order to obtain the desired alcoholic strength. Vodka. This is the national distilled liquor of Russia. The genuine vodka is prepared from rye, employing 15 to 20 per cent of barley malt or green rye malt in order to saccharify the starch. Some of the cheaper grades of vodka are prepared from potatoes and corn instead of rye. Vodka contains from 40 to 60 per cent of alcohol by volume; in fact, it is illegal to sell it if the alcohol is less than 40 per cent. The method of distillation is about the same as that used for patent-still whiskies. Chartreuse. Three different types are on the market, namely, green, yellow, and white Chartreuse. They have been prepared for centuries by the Carthusian monks, who have zealously guarded their secret of production even to this day. Chartreuse is prepared from a mixture of aromatic herbs and seeds, and pos- sesses a very delicate flavor and taste. Benedictine. This cordial is altogether different in taste and flavor from Chartreuse. The genuine Benedictine also is pre- pared by monks. Kirschwasser. This liqueur is colorless in appearance and is obtained from cherries. The latter, including the seeds, are crushed and allowed to undergo fermentation. The alcohol is then distilled. The finished Kirschwasser has a pleasant flavor and bouquet, slightly reminding the consumer of ripe cherries. Maraschino. This is another cherry cordial distilled from the fermented juice of Dalmatian cherries. It is sweetened by an addition of sugar-sirup. Prune, Peach, Apricot, and Cherry Brandies are prepared from these respective fruits by distillation of the fermented juices. The distillate is either placed on the market as first obtained, or it is sweetened and colored. Sometimes an infusion of the fruit in alcohol also is added to the distillate, or the infusion itself is placed on the market. They all possess the characteristic flavor and aroma of the fruit from which they are obtained. Absinthe. This cordial is very popular in France and is pre- pared by distilling rectified alcohol or brandy in which worm- wood, star-anise, green anise seed, fennel, coriander, angelica-root or other aromatics have been macerated for about a week. The resulting liqueur is greenish in color and contains a large amount of volatile oils. On account of the latter, absinthe becomes milky when water is added immediately before drinking it. The 428 ELEMENTS OF INDUSTEIAL CHEMISTRY oil of wormwood has a very powerful effect upon the nervous system, and steady tippling of absinthe causes digestive disorders, induces vivid dreams and hallucinations, and may finally cause paralysis or idiocy. Anisette. The aromatic seeds used for its preparation are green anise seed, star-anise, and coriander seed. The distillate is sweetened and sometimes also receives an addition of orange- flower water. Creme de Menthe is a sweetened liqueur, the flavor of which is obtained from fresh mint leaves, usually peppermint. It usually possesses a pronounced green color. Creme de Yvette, also called Creme de Violet, has a pronounced odor of violets and also is violet in color, artificially obtained. Creme de Roses is rose-colored in appearance and is a sweet- ened liqueur having a pronounced odor of oil of roses. Creme de Vanilla has a strong vanilla taste and odor. Crtme de Cacao is obtained by making an infusion of cocoa, alcohol and sugar-syrup. Curacao. This very fine liqueur is prepared by macerating orange peel, especially from Curacao oranges, in rectified alcohol for a week or longer. After distillation and addition of sugar- syrup and a coloring substance is added. The finest grades are prepared in Holland. Aquavit. Although this liqueur is not a cordial in the true sense of the word, a brief description is placed here. It is gener- ally used as an appetizer. Aquavit is manufactured and con- sumed extensively in the Scandinavian countries, especially Denmark. When the alcohol from grain mashes is rectified, an addition of caraway seeds and orange peel is made in order to impart their flavors to it. Kummel is obtained by distilling alcohol in the presence of the herb cumin and caraway seed. An infusion of these in alcohol also is made. The product has a pronounced taste and odor of the caraway seed and is sweetened more or less according to the demands of the trade. It is very popular in Germany. CHAPTER XXIII TEXTILES DEFINITIONS. By the term " textiles " is to be understood a class of manufactured articles prepared from " yarns " which are continuous threads composed of fibrous materials. These fibrous materials, which form the basis of textile manufactures, are of various kinds, including animal, vegetable, and mineral products; for example, wool, cotton, and asbestos. A fiber is really a filament the length of which is comparatively much greater than the diameter, and the latter is of almost microscopic proportions. This allows of several fibers being twisted together by a process known as spinning, so that a continuous and uniform thread is produced. Physically, a textile fiber must possess con- siderable tensile strength and pliability in order to yield a satis- factory thread. In the case of the shorter fibers, such as cotton and wool, the surface structure also allows of considerable cohesion between the separate fibers when twisted together. Where this cohesive property is lacking, as in silk and some of the cruder vegetable fibers, the strength of the twisted thread depends on the great length of the individual filaments. ORIGIN. The textile fibers may be classified with respect to their origin in the following manner: Animal Fibers, consisting (a) of the hairy covering of various animals, principally of the sheep, goat, cow, and camel; and (6) of the filaments spun by the silkworm for its cocoon. Vegetable Fibers, consisting (a) of the hairy covering of the seed of the cotton plant; (b) of the bast or structural part of the stem of certain plants, such as flax, ramie, jute, and hemp; (c) of the structural part of the leaves of such plants as sisal, agave, and certain palms. Mineral Fibers, of which the only representative is asbestos. Artificial Fibers, such as artificial silk, prepared from solu- tions of cellulose derivatives, spun glass, and certain metals drawn out to fine filaments. There are also metallized yarns, 429 430 ELEMENTS OF INDUSTRIAL CHEMISTRY consisting of a core of cotton, linen, or other fiber, coated with a finely divided metal and a suitable agglutinant. The great bulk of the textile fibers are comprised under the first two classes, of which the most typical representatives to be considered are wool, silk, cotton, and linen. THE ANIMAL FIBERS. In their chemical nature these fibers are essentially proteid substances of complex organic structure. The basis of wool (and the hair fibers in general) is called keratin, a nitrogenous substance containing also sulphur, while that of silk is known as fibroin, which is also nitrogenous but does not contain sulphur. In their physical structure the hair fibers are very complex, being composed of minute cells and provided with an external layer or sheath of hard, bone-like tissue or scales. Silk, on the other hand, is a continuous filament without apparent organic structure. THE VEGETABLE FIBERS. The chemical basis of this entire class of fibers is cellulose, and as this contains neither nitrogen nor sulphur, it presents a marked chemical difference to the albumi- nous substance of the animal fibers. In their physical structure the vegetable fibers as a class are comparatively simple; in the case of cotton the fiber consists of a single elongated cell; with the bast and leaf-tissues the commercial fiber consists of a more or less complex aggregate of small cells. Cotton in its natural state consists of almost pure cellulose, and requires but little purification for use in manufacturing; the other vegetable fibers, however, are associated with a considerable amount of substances other than cellulose and require a rather extensive process of purification for the purpose of isolating the pure cellulose fiber. WOOL. This fiber is the hairy covering (or fleece) of the sheep. It is a growth originating in the skin, springing from a root or hair-follicle. In its physical structure the fiber consists of three portions: (a) an inner layer of rounded elliptical cells, called the medulla, and often containing pigment matter; (6) a surrounding region of elongated spindle-shaped cells, called the cortical layer, which forms the major portion of the fiber; and (c) an external coating of flattened, hard, horn-like cells, or epidermal scales arranged in such a manner as to overlap like the scales on a fish. This latter peculiarity of structure gives to wool a characteristic, microscopic appearance, whereby it may be readily distinguished from other fibers (see Fig. 113). The character of fiber pro- duced in the fleece varies largely with the breed and cultivation of the sheep. The merino sheep (now grown principally in Aus- TEXTILES 431 tralia) gives a long, fine and wavy fiber, much prized for the manufacture of high-class clothing fabrics. The majority of the wool grown in America (chiefly known by the name of " territory " wool) is of shorter staple and coarser in quality. The arrange- ment of the epidermal scales also varies considerably with the nature of the fiber. With some wools, these scales are prominent and the free edge projects considerably, giving the fiber a serrated or saw-toothed appearance. Wool of this nature is easily felted, as the fibers become firmly attached to one another by the interlocking of the projecting scales. In other varieties of wool the external scales lie flat on the surface with very little free edge project- ing, hence the surface of these fibers is smooth and does not readily felt together. Another important physical property of wool is its waviness. Some wools (espe- Ftg - 113 - cially the fine merinos) are very wavy, and the waves (or crimps) occur with great regularity through- out the entire length of the fiber; other wools are stiff and straight with lictle or no waviness, or have very irregular waves. The wavy structure of the fiber enhances its spinning quality, as it allows of a greater coherence among the fibers when they are twisted together. A yarn composed of such fibers also exhibits greater resiliency and sponginess as well as elasti- city. SCOURING OF WOOL. In its natural state in the fleece wool is contaminated with a number of impurities. These may be classified as follows: (a) Wool grease, which occurs in large quantities as an external coating on the fiber; it is a natural exudation of the sheep and serves as a protection to the fiber, preventing it from becoming felted and mechanically injured. It differs from other animal fats in that it does not consist of the glycerides of the fatty acids, and is very difficultly saponifiable with caustic alkalies. Wool grease possesses more the chemical properties of a wax, as it is composed mostly of the higher solid alcohols known as cholesterin and isocholesterin both in the free state and as esters with the fatty acids. Though insoluble in water and not saponifi- able by alkalies, cholesterin is easily emulsified, a property on which is based the usual method of wool scouring. Wool grease, 432 ELEMENTS OF INDUSTRIAL CHEMISTRY however, is easily soluble in naphtha and other volatile sol- vents. (6) Suint, or dried-up perspiration, consisting largely of potash salts of organic acids, and soluble in water. (c) Miscellaneous dirt, such as dust, sand, vegetable matters, tar, etc. Before the wool fiber can be used in manufacturing processes it must first be cleansed from the adhering impurities. This is accomplished by scouring the dirty and greasy wool in a warm soap solution, to which more or less soda ash is added. The temperature of scouring should not be above 140° F., else the fiber will be injured by the action of the alkali. The wool grease is easily emulsified by the alkaline soap solution, whereas the suint is dissolved by the water, the other impurities being removed by the mechanical action of the water. After scouring in the soap solution the wool is thoroughly rinsed in warm water, and finally squeezed and dried. Another form of wool scouring, known as the solvent process, is becoming of great importance in this country. The greasy wool is treated with solvent naphtha in closed kiers, and the resulting solution of wool grease is trans- ferred to stills where the naphtha is recovered and the wool grease is obtained as a by-product. The latter may be further purified and utilized for the preparation of lanolin compounds. The degreased wool is next treated with a dilute warm soap solution to remove the suint and dirt. This process leaves the fiber in a much better condition and the recovered grease is of sufficient value to pay for the cost of scouring. MECHANICAL TREATMENT OF WOOL. After wool has been scoured and dried the next step is to convert it into yarn. In the first place, according to the quality of yarn desired, a close selection of the required grade of wool is made. This is the function of a special branch of the industry known as wool grading and sorting. Wool is first graded with reference to the breed of sheep, such as full-blood merino, territory, half- blood, etc. This has reference chiefly to the fineness and length of staple. The long stapled wools are suitable for combing and are used for the preparation of worsted yarns; the shorter stapled varieties are carded and made into woolen yarns. In the combing process the shorter fibers (noils) are removed from the long ones, leaving the latter to form what is called tops, a form of preparation previous to the spinning of the yarn. As the character and equal- ity of the fiber varies considerably at different parts of the same TEXTILES 433 fleece, wool is further graded by sorting the fleece into its distinc- tive portions, such as the loin, back, neck, legs, etc. Usually the fleece is sorted into nine portions. The grading and sorting of the fleece is made previous to scouring. In the preparation of yarn the first step is combing (for long staples) or carding (short staples). This is for the purpose of removing undesirable matters, such as short fibers, adhering impurities, etc., and also to lay the fibers in a parallel direction and bring the wool into a ribbon-like form so as to permit of the subsequent spinning operations. These latter processes consist in further paralleling the fibers and reducing the thread to the desired size by drawing out and twisting. Chemical Treatment of Wool. (1) Bleaching. The wool fiber in its natural state contains more or less of a yel- lowish-brown pigment. In some cases this pigment becomes greatly accentuated and the fleece may be dark brown or even black in color, but these occasional " black sheep " are of rather rare occurrence. Where it is desirable to have a per- fectly white fiber either for purposes of dyeing delicate tints or for white goods, it becomes necessary to bleach the wool. There are two general methods in use at present for this purpose. In the first, sulphurous acid, SO2, is used as the active bleaching agent. The well-scoured and moistened woolen material is placed in a suitable room and subjected to the prolonged action of fumes of burning sulphur, the time required for complete bleaching being from eight to twenty-four hours, depending on the nature and texture of the material. The process is termed " stoving," from the so called stove in which the sulphur is burnt. The bleaching room must be so constructed as not to permit of the condensed acid liquor dropping on the goods, which would otherwise be spotted and injured. This process is known as the " gas " or " dry " method of bleaching. After the bleaching is finished the wool is rinsed in a water containing a minute quantity of a blue or bluish -violet coloring matter for the purpose of tinting the white so as to furnish a more pleasing color to the eye. A " wet " process of bleaching may also be employed, the wool being steeped in a dilute solution of sodium bisulphite for some hours, and then passed through a bath of dilute sulphuric acid. The bleached white obtained on wool with sulphurous acid does not appear to be permanent, as prolonged exposure to the air will cause the yellow natural color to return. This has been ac- counted for by assuming that the sulphurous acid merely reduces 434 ELEMENTS OF INDUSTRIAL CHEMISTRY the natural pigment to a colorless compound which becomes reoxidized on exposure to the air, resulting in the formation again of the original pigment. A second process for the bleaching of wool which is coming into considerable favor, more especially for fine goods, is that which employs sodium peroxide as the bleaching agent. Hydro- gen peroxide is also employed to a considerable extent in bleach- ing. It is probably somewhat more expensive to use than sodium peroxide, but does not offer the disadvantages of the latter in the preparation of the bleaching liquor, which in the case of hydrogen peroxide is also free from sodium sulphate. Sodium peroxide, Na202, when dissolved in water acidulated with sul- phuric acid yields a solution of sodium sulphate and hydrogen peroxide: Na 2 02+H2S04 = Na 2 S04+H 2 02. The hydrogen peroxide in contact with organic substances readily decomposes with liberation of nascent oxygen: H 2 2 = H 2 0+0, and the latter quickly decomposes and destroys the coloring matters in wool. Wool may also be bleached by treatment with a cold dilute solution of potassium permanganate. The pigment in the fiber is rapidly destroyed by the strong oxidizing action of this chem- ical, but the resulting decomposition of the permanganate pre- cipitates a brown hydroxide of manganese on the fiber, hence it is necessary to pass the wool through a second bath containing a weak solution of sodium bisulphite, which removes completely the deposit of manganese compound and leaves the wool per- fectly white. Oxalic acid will also have the same discharging effect on the brown oxide of manganese, and is sometimes em- ployed in place of sodium bisulphite. This method gives a very rapid process for bleaching, but it is rather costly. The Minor Animal Fibers. In addition to wool there are also a number of other animal hair fibers employed to a limited extent in the manufacture of textiles. The woolly fibers of dif- ferent species of goats are utilized in much the same manner as wool itself. Mohair is obtained from the Angora goat. The fiber is long, fine, smooth and highly lustrous. It is largely used for the manufacture of plushes, braids, and linings. Cashmere, TEXTILES 435 alpaca and llama are also fibers from species of goats. All of these animal hair fibers are similar in chemical composition to wool; their physical structure is also very similar. SILK. Though silk is also an animal fiber and somewhat similar to wool in its general chemical properties, it differs very widely from that fiber in its plrysical structure and properties. The silk fiber is a fine continuous filament spun by the silkworm in the preparation of its cocoon. The fiber as spun by the cater- pillar consists of two filaments composed of a proteoid substance called fibroin and surrounded and cemented together by a glue- like substance known as sericin or silk-gum. The silkworms are cultivated principally in China, Japan, Italy and southern France. Their chief food consists of the leaves of the mulberry tree, hence the caterpillar is known as the mulberry silkworm, or Bombyx mori. The cocoons are irregularly ovoid in shape and the length of the fiber in them varies from 350 to 1200 meters, while its average diameter is 0.018 mm. The silk fiber as used in manufacturing is prepared by reeling from the cocoons. When the cocoons have been completed by the silkworm they are collected and heated in an oven to a temperature of 60 to 70° C. for the purpose of killing the pupa within. Or, the cocoons may be steamed for a few minutes, which serves the same purpose. The cocoons are then sorted for size, color, damage, etc., so as to obtain a uniform product. They are then placed in a basin of warm water, which softens the enveloping silk-glue and permits of the unwinding of the cocoon thread. The fibers from several cocoons are brought together and passed over a suitable reel, where they are slightly twisted together to form a thread of suffi- cient size for weaving. The adhering silk -glue becomes hard- ened again, so that the thread presents a uniform appearance. This silk is reeled into skeins of convenient size and comes into trade as raw silk. Owing to the presence of the silk-glue it is stiff and wiry and translucent in appearance. Some varieties are of a creamy white color, while others are quite yellow. This yellow .color, however, exists only in the silk-glue and is removed along with the latter. Organzine silk is prepared from the high- est grade of cocoons, and by reason of its superior strength it is employed for warps. Tram silk is weaker and is used for filling. In the reeling of silk a large amount of waste is produced. This is scoured in a solution of soap and soda in order to remove the silk-glue, and the residual fiber is then carded and combed and is used for the preparation of spun silk. 436 ELEMENTS OF INDUSTRIAL CHEMISTRY Bleaching of Silk. For most purposes silk is sufficiently white without bleaching, but where very delicate tints are to be dyed or where a very pure white fabric is desired, it is necessary to bleach out the slight tint of yellow to be noticed in natural silk. Silk may be bleached in much the same manner as wool, using either the sulphurous acid or the sodium peroxide process. The latter method is to be preferred in the case of silk, as it fur- nishes a nicer product, and the bleach is not liable to become yellow again on exposure. The extra cost of this process is not a drawback when employed for silk as when used for wool, as the comparative value of the fiber itself is far greater. Silk was formerly also bleached by treatment with dilute cold solutions of aqua regia, but as this process was very liable to cause injury to the fiber unless very skilfully conducted, it is not now employed to any extent. COTTON. The cotton fiber consists of the hairy covering of the seeds of the cotton plant, or gossypium. There are a large number of species and varieties of the cotton plant, the principal of which are the following: Gossypium barbadense, producing silky and long-stapled fibers, the principal representatives of which are the Sea Island cotton of the Southern Gulf States, Egyptian cotton and Peruvian. Gossypium hirsutum, which includes most of the cotton grown in the United States and forms the great bulk of the cotton used in trade. It is known as upland, peeler or simply American cotton. Gossypium herbaceum, including the majority of the cotton grown in India and China, as well as the small amount which is grown in Italy. The fiber is very short and inferior to that of the two preceding varieties. Gossypium arboreum comprises most of the cotton in Asia Minor. This variety grows to the dimensions of a tree in contra- distinction to the other varieties, which are all shrubs. The fiber is of poor quality, being short and coarse and of a greenish color. The seed hairs of cotton are developed in a boll as the fruit of the plant ripens, and when maturity is reached the boll bursts open, liberating a fluffy white mass of fibers. These fibers are firmly attached to the surface of the seed, and after the cotton is picked from the plant the fiber must be detached and separated from the seed by a process known as ginning. The ginned fiber is then baled and distributed to the spinning mills. The seed TEXTILES 437 which is left now forms a valuable by-product of the industry. It is first subjected to a second process of ginning for the purpose of removing the short undergrowth of fibers known as neps or linters, and these are used in the manufacture of wadding and cotton batting. The cleaned seeds are then hulled, and from the separated meal the oil is extracted bj^ cold and hot pressing and steaming. The cotton seed oil so obtained is a very valuable product, the finer qualities being used for salad oils and other culinary purposes, while the lower grades are extensively used for soap-making. The residual meal is used as a cattle food, and other residues find use as fertilizers. Before being utilized by the spinner, cotton is graded with respect to length and fineness of staple, color, cleanliness, and other qualities. The value of the fiber is determined by this classification, the basis being what is known as " middling " cotton, the various grades going up and down from this standard. Physical Properties of Cotton. The cotton fiber consists of a single cell, narrow and elongated, with one end fastened to the seed and the other tapering to a point. During its growth it is tubular, being cylindrical in shape with comparatively thin cell- walls and an inner canal or lumen. When the fiber ripens, the sap in the inner canal is absorbed, the cell-walls collapse, leading a flat ribbon-like fiber with thickened edges. By the unequal drying of the fiber it becomes twisted spirally on its axis. These spiral twists give to cotton its good spinning qualities, for when twisted together the fibers cohere to one another to give a strong thread. The different varieties of cotton exhibit considerable variation in length and fineness of staple. Sea Island cotton has an average length of about 1.6 ins. and a diameter of 0.00065 in. Ordinary American cotton varies from 1.5 to 0.75 in. in length and has a diameter of about 0.00075 in. Egyptian cotton has a staple slightly shorter than Sea Island, and of about the same fineness. The South American and Indian cottons are comparatively short and coarse, averaging about 1 in. in length and 0.00085 in. in diameter. The physical character of the fiber in any lot of cotton is very variable, hence in manufacturing it is necessary to separate the short fibers from the long by a process of combing or carding; the longer fibers being used for the better grade of yarns and the shorter fibers for the coarser yarns. The degree of ripeness of the fiber also determines its general character; unripe fibers have a very attenuated cell- wall and consequently are weak and brittle. The mature fiber has 438 ELEMENTS OF INDUSTRIAL CHEMISTRY a thicker wall and a much greater strength. Sea Island, American and Indian cottons contain very little natural pigment, being quite white in appearance; the chief varieties of Egyptian cot- tons, however, are rather highly tinged with a brownish color, which is quite distinctive. The micro- scopic appearance of cotton is quite char- acteristic and serves to distinguish it readily from other fibers either of animal or vegetable origin (see Fig. 114). The flat, twisted, ribbon-like appearance is very noticeable. Bleaching of Cotton. On account of the nature and the small amount of impurities present in the raw fiber, cotton Fig. 114. does not require a previous scouring operation to fit it for manufacturing processes. Previous to dyeing, however, cotton must be scoured or " wet-out " for the purpose of removing the waxy coating so that the fiber may be able easily to absorb the dye solutions. This is accomplished by boiling the material in a weak solution of caustic soda, soda ash, soap, or Turkey-red oil. When cotton is to be bleached, not only the waxy coating must be removed to permit of wetting-out, but as far as possible all of the impurities on the fiber must be removed. This process is termed " boiling-out." Cotton may be bleached in any form of its manufacture. It is occasionally bleached in the loose state before spinning, in which case special machines are employed which allow of the bleaching liquors being circulated through the cotton without motion of the fibers, so as to avoid matting and injury to the latter. Instead of boiling-out with alkalies, cold water is circulated through the cotton under pressure, which has the effect of removing the majority of impurities on the fiber without materially dissolving the cotton-wax. Cold bleaching liquors, wash waters, acid solutions, etc., are then circulated in the same manner. The result is a bleached cotton which still retains considerable wax,- so the spinning qualities of the fiber are not materially injured. If loose cotton is thoroughly boiled- out and bleached in the usual manner, the fiber will be harsh and will not spin well. Cotton waste and linters are also bleached largely in the loose state for the preparation of absorbent cotton. In this case, as it is not necessary to retain the spinning qualities, but to make the fiber as pure and as absorbent as possible, a very TEXTILES 439 thorough boiling out with caustic soda is given before the bleach- ing. Cotton yarn is very extensively bleached, both for white goods and as a preparation for the dyeing of delicate shades. The yarn in the form of skeins is usually bundled together and systemati- cally packed into a closed iron kier. The latter is so constructed as to permit of the circulation of a boiling alkaline solution under pressure (5 to 10 lbs.) through the yarn. The boiling-out solu- tion usually consists of a mixture of caustic soda and soda ash. Sometimes so-called " bleaching assistants " are used; these mostly consist of soda ash mixed with a small amount of caustic soda and sodium silicate. For the proper boiling-out of the yarn it is essential that the liquor be circulated evenly and thoroughly through the goods. The amount of alkali employed is about 2 to 3 per cent on the weight of the yarn, and the time of boiling varies from one and one-half to eight hours, depending on the kier employed and the pressure. Overboiling by the use of too much alkali or too prolonged a treatment will render the yarn harsh and brittle and also cause yellow stains. The presence of air in contact with the superheated yarn in the kier will also cause oxidation, resulting in weak places and stains. After the yarn has been boiled-out it is washed with fresh water, usually in the same kier, and then worked in a cold dilute solution of chloride of lime (bleaching powder or chemic) at 1-J- to 2° Tw. For this purpose the yarn is either hung in sticks and steeped in the chemic solution in ordinary dye-house vats, or better yet it is placed in a machine where it may be automatically worked in the solution. The treatment with the bleaching liquor usually lasts from three-quarters to one hour. The yarn is then rinsed in fresh water and next soured by treatment with a cold solution of sulphuric acid at about 1° Tw.; hydrochloric acid may also be used*. The acid treatment is for the purpose of decomposing the lime compounds retained by the fiber. Where sulphuric acid is used calcium sulphate is formed, which is easily removed in the subsequent washing. Hypochlorous acid and free chlorine are also liberated in the fiber, which furthers the first bleaching action of the chloride of lime solution. This is evidenced by the fact that the cotton becomes much whiter in appearance when treated with the acid, also the presence of chlorine is to be noted from its pungent odor. When hydrochloric acid is used for the souring, the very soluble calcium chloride is formed, which is very easily removed from the cotton by washing; otherwise the action of the 440 ELEMENTS OF INDUSTRIAL CHEMISTRY acid is the same. After the acid treatment, it is necessary to give the cotton a very thorough washing to remove as completely as possible the residual acid liquor and the lime compounds from the fiber. If this is not done the yarn will be harsh and tender after drying. The washing should be continued until the yarn shows no indication of acid when tested with blue litmus paper. Finally, the yarn is treated in a dilute lukewarm solution of soap or other suitable finishing compound, and if a bluish tone of white is desirable a suitable bluish-violet coloring matter is added for tint- ing purposes. The bleaching process with chloride of lime is an Oxidation process; the chlorine itself, which is the active con- stituent of the bleaching powder, does not directly destroy the coloring matter in the fiber. In the presence of water, how- ever, the chlorine liberated in a nascent condition from the chloride of lime reacts with the formation of oxygen, and it is the latter which acts on the coloring matter. Skein yarn may also be bleached by being linked together in the form of a long chain and run continuously through machines provided with squeeze rollers. Yarn in the form of prepared warps may also be bleached in a similar manner. There are also special machines for the bleaching of cotton slubbing and yarn in the form of cops and tubes, the yarn or slubbing being wound on perforated tabes and so arranged on the machine that the bleaching liquors are forced through the cotton either by means of vacuum suction or pumps. Cloth bleaching is the principal method, however, for the bleaching of cotton. There are several methods of carrying out this form of bleaching depending on the ultimate use to which the goods are to be put. When the cloth is destined to be sold as white muslin the process is known as the market bleach; when the cloth is subsequently to be dyed with alizarin colors (especially red), a so-called Turkey-red or bottom bleach is given; whereas cloth intended for printing is given the madder bleach. These names are quite old in their application and are falling into disuse as characteristic terms. In bleaching for white goods for the market it is desirable to obtain a clear white color with a bluish tint, and the appearance of the goods also depends to a considerable degree on the finishing processes given the cloth after bleaching. The Turkey-red bleach is only for the purpose of providing a white bottom for dyed colors so that the latter will appear bright and clear. The bleaching required of print cloth is by far the most complete and thorough, as it is neces- TEXTILES 441 sary to remove all impurities from the goods so as to leave the cotton not only white in color but also in the form of chemically pure cellulose so that the printing colors may be properly applied. A general outline of the various processes in this method of bleach- ing is as follows: Marking. The cotton pieces as they come from the loom are stitched together and marked with a special ink capable of resisting the bleaching operations so they may be subsequently identified. Singeing. The cloth is passed rapidly through a series of gas jets so as to burn off the loose fibers and lint from the sur- face. The singeing may be done on one side only or on both sides as required. Instead of being passed through gas jets the cloth may be passed over curved copper plates heated to redness, or over a heated revolving copper roller. Singed cloth gives a clear, even surface, so that fine and delicate patterns may be sharply and clearly printed. Gray Wash. This is a preliminary wetting out in water and has for its purpose the removal of much of the external dirt as well as the softening and removal of much of the sizing used on the warp yarns in weaving the cloth. This operation is frequently omitted. Boiling-out. This is a similar operation to the boiling-out of cotton yarn. It is usually conducted in large closed iron kiers provided with a suitable mechanism for the circulation of the liquor through the goods. The boiling is usually conducted under pressure (from 10 to 80 lbs.) for from six to eight hours. It was formerly the custom to give a first boiling with milk of lime (lime oil). The goods were passed through a solution of milk of lime and without squeezing were packed into the kier; sufficient water was next introduced and the kier boiled with superheated steam. The lime boil was considered necessary to decompose the fatty matters in the cotton with the formation of a lime soap, and also to convert the starch (or other dressing materials on the cloth) into a soluble form. Of late years, however, the lime boil is being dispensed with as a preliminary operation, and the boiling-out is done in one operation with caustic soda. When the lime boil is used it is necessary to give a thorough washing to the goods and then to pass them through a weak bath of sulphuric acid (1° Tw.), known as the gray sour. This is for the purpose of dissolving out the lime compound in the fiber as well as any iron stains which may have formed 442 ELEMENTS OF INDUSTRIAL CHEMISTRY in the kier. After the acid treatment another thorough washing process is required. After the gray sour the goods are given a second boiling in the kier (Fig 115) with caustic soda; generally mix- tures of caustic soda, soda ash, and rosin soap are employed, and from two to three boilings are given. These boilings remove all of the waxy and fatty matters and most of the pectin compounds in the fiber. The use of rosin was once considered essential to the perfect scouring of cotton for purposes of print-cloth. At the present time, however, the tendency is to omit the rosin boil: in fact, the boiling-out is reduced to the single operation of treating in the kier with caustic soda solu- tion. Washing. After the boiling-out, in whatever manner it may be con- ducted, the goods are very thor- oughly washed in order to remove, as far as possible, all of the decom- posed impurities and residual alkali. The washing is conducted in special forms of washing machines (Fig. 116) and well flushed with fresh water. Chemicking. This is the general term given to the treatment with the solution of bleach- ing powder. The strength of the solution employed is usually 1J to 2° Tw., and the liquor should be clear and free from undissolved particles or sediment. The damp cloth is saturated with this chemic solution, passed through squeeze rolls, and then piled up and left ex- posed to the air for some hours. This allows the carbonic acid of the air to react with the bleach liquor with the formation of free hypochlorous Fig. 115. Fig. 116. TEXTILES 443 acid which destroys the coloring matter present through its strong oxidizing action. Care must be had not to allow the oxidizing action to proceed too far or the cotton fiber itself will be attacked and weakened by the formation of oxy cellulose. In some methods of bleaching, instead of exposing the cloth to the action of the air, it is steeped in the solution of bleaching powder for some hours, or the cloth is packed in suitable kiers and the chemic solution is circulated through it by means of pumps. Souring. After treatment with the chemic solution the cloth contains a considerable amount of lime compounds and unde- composed chlorine derivatives. The souring, or treatment with a dilute solution of sulphuric acid 1° Tw., is for the purpose of removing or decomposing these compounds. The cotton also becomes much whiter in color after the treatment with acid, hence this process is known as the white sour (in contradistinction to the gray sour when a lime boil is used). Instead of using sulphuric acid for souring, hydrochloric acid is sometimes employed, as the lime salt with this latter acid is much more soluble; hence much easier to remove from the fiber. After souring a very thorough washing must be given the cloth in order to remove all salts and acid residue. Finishing. The final operation in bleaching cotton cloth is to give it a finish suitable to the use for which it may be intended. In the case of a market bleach, the cloth must be tinted to a proper tone of bluish white and also be starched and calendered to give it a smooth and polished surface. Cloth intended for dyeing, of course, is not tinted, and receives its special finish after it is dyed. Print-cloth is also not tinted, and it is finished in the printing operation. LINEN. This is next to cotton as a vegetable textile fiber. It is obtained from the bast of the flax plant, and differs consider- ably from cotton in its structure and appearance. In preparing the fiber the entire plant is taken and put through a rippling machine for the purpose of removing the leaves, seeds, etc. The cleaned stalks are then subjected to a process known as retting for the purpose of decomposing the woody tissue and dissolving the resinous and gummy matters so that the free fiber may be obtained. Retting is essentially a fermentation process, and a number of different methods are employed. The two chief methods are: (1) steeping in stagnant water. The flax straw is tied into convenient bundles and laid down in pools of soft water. Fermentation rapidly sets in, and 444 ELEMENTS OF INDUSTRIAL CHEMISTRY when the woody tissue has been decomposed, but before the fiber itself is attacked, the bundles are removed and spread out on the grass for a number of days, where they may be exposed to the combined action of sunlight and air. The pulpy stalks are then passed through special breaking and scutching machines for the purpose of breaking up and re- moving the decomposed matters and leaving the fiber free and clean. Flax produced in this manner has a rather dark grayish- brown color, as the coloring matters formed during the retting process are not removed. The majority of the Irish flax and some of the Russian flax is retted in this manner. (2) Steeping in fresh running water (in streams) is another method of retting by which most of the French and Belgium flax is made. The bundles of flax straw are submerged in the streams by means of crates. The fermentation proceeds more slowly than by the first method, but the coloring matters are removed by the running water, so the final product is much lighter in color, and the fiber is of a superior quality. Flax may also be retted by exposing the stalks for a number of weeks to the action of dew. There have also been a number of " improved " chemical methods proposed for the retting of flax, chiefly with the purpose of hasten- ing the fermentation and obtaining a brighter and clearer fiber, but none of these nave proved to be of any value. The linen fiber as it appears in trade is in the form of long, rather coarse, filaments of a silver or brownish color. These fibers consist of a number of comparatively small elongated cells cemented together by a glutinous intercellular substance. The individual fiber cells are about 1 to 2 ins. in length and from 12 to 25 /* in diameter. The fiber is cylindrical with thick cell- walls and a narrow internal canal. Under the microscope the fiber shows the pres- ence of peculiar cross-marks resembling joints or dislocations (see Fig. 117). FlG iYi m In its chemical properties linen is very similar to cotton, but its cellulose is less pure owing to the intercellular substances present. Linen is bleached in the same general manner as cotton, but as the fibers are more or less disintegrated into the individual cells by the bleaching process, fully bleached linen is much weaker than raw linen. On this account, linen is generally only par- TEXTILES 445 tially bleached. In its general characteiistics linen is stronger than cotton but less elastic; it is a better conductor of heat, hence linen garments are colder than those of cotton. Linen also has a higher degree of luster than cotton. JUTE. This fiber is without doubt next in commercial and technical importance to linen. It is also a bast fiber obtained from the stalks of Cor chorus capsularis, or Jew's mallow, growing in tropical and subtropical countries. The majority of the jute of commerce comes from India and the East Indian Islands. The fiber is prepared from the stalks by a simple retting in water, the fiber separating rather readily from the other tissues. As it appears in trade the fiber is from 4 to 7 ft. in length, usually of a yellowish-brown color, though some qualities are of a silver- gray color. It has considerable luster and a high tensile strength. The cell-elements of the jute fiber are rather small, being about 1.5 to 5 mm. in length and 20 to 25 ix in diameter. The fiber is composed of a rather large number of these cell elements cemented together. A cross-section of the fiber shows these cells to have a polygonal outline. The microscopic appearance of the jute fiber differs from that of linen in not exhibiting the peculiar jointed ridges running across the fiber. In its chemical composition and properties, jute differs essen- tially from the other vegetable fibers. Instead of being composed of relatively pure cellulose it appears to consist almost altogether of a modified form of cellulose known as ligno-cellulose or bastose. This is shown by the fact that the jute fiber gives a yellow colora- tion when tested with iodin-sulphuric acid reagents, whereas ordinary cellulose gives a blue color. Owing to its different chem- ical composition, jute behaves quite differently with the various classes of dyestuffs, as it combines directly with both acid and basic dyes, whereas cotton and linen require mordants for these colors. The Minor Vegetable Fibers. There are a number of vegetable fibers which are largely used for the manufacture of cordage, mats, etc., and which can scarcely be termed textile fibers in the sense of being utilized for woven fabrics. Hemp and sisal are the principal fibers used for cordage. The former is a general name for a large number of commercial fibers of similar physical appearance and properties, and obtained from a number of different plants. Sisal is a fiber obtained from the leaf tissues of the agave and other similar plants. Ramie or China-grass is a bast fiber obtained from species of the nettle 446 ELEMENTS OF INDUSTRIAL CHEMISTRY plant. It is a fine white and very strong fiber which would be very valuable commercially except for the difficulty with which it is obtained from the plant and from the fact that the surface of the fiber is so smooth that it lacks cohesion in spinning. ARTIFICIAL SILK. This is a fiber which is attaining consider- able commercial value. It is a cellulose fiber artificially prepared from suitable solutions of cellulose by forcing the liquid through fine orifices and coagulating the cellulose as it emerges in the form of a delicate thread. There are a number of methods at present used for the production of this fiber, among which the following are the most important: (1) Pyroxylin or chardonnet silk, pre- pared from a solution of guncotton in a mixture of alcohol and ether; as the thread is formed the solvent is evaporated and the nitrated cellulose becomes coagulated into a continuous filament. This thread is subsequently denitrated by treatment with solu- tions of nitric acid, ferric chloride, and ammonium phosphate. (2) Cupra-ammonium silk is prepared from solutions of cellulose in the copper-ammonium sulphate solvent known as Schweitzer's reagent. The thread is coagulated and the metallic salts removed by a treatment with a solution of sulphuric acid. (3) Viscose silk is prepared from a solution of viscose or cellulose thiocar- bonate, the thread being coagulated by passing through a solu- tion of ammonium sulphate, and subsequently washed very thoroughly to remove the sulphur compounds that are formed in the decomposition of the viscose. These artificial silks resemble true silk very closely in general appearance, possessing even a higher luster than the latter. The fiber, however, is more wiry and harsh in nature, and its strength and durability is consider- ably below that of true silk. The strength of artificial silk is also greatly lessened when wetted with water. This fiber, however, has a large use in the manufacture of braids, dress trimmings, passementerie, and ornamental fabrics of various kinds where a high luster is especially desirable. Artificial silk is dyed in the same manner as cotton. Yarns for textile purposes have also been prepared from paper pulp, the general process, being to cut the thin sheet paper pulp into narrow strips, and then twist into yarns. Such products aie Silvaline and Textilose yarns and fabrics. CHAPTER XXIV DYESTUFFS AND THEIR APPLICATIONS TEXTILE COLORING. Textile coloring may be defined as the process or combination of processes used to fix a color or colors uniformly, and more or less permanently, upon textile material. It includes both dyeing and printing. DYEING. The term dyeing is sometimes given almost as broad an interpretation as textile coloring, but to be specific, it should include only those processes in which the entire body of the material being colored is immersed in the coloring bath, a greater or less period of the time required for the coloring. TEXTILE PRINTING. Textile printing is a process by means of which the coloring matters applied may be confined, by use of a printing machine, to certain portions of the material, thus pro- ducing a definite colored design. The necessary dyestuffs and chemicals are made into a paste, with starch, dextrine, or other gums, and applied to the cloth by means of copper rollers, one for each color, the cloth being finally subjected to special aging and drying processes. By this method it is possible to produce prints containing ten or more different colors. Compounds Used by the Textile Colorist. The chemical compounds used by the textile colorist may be divided into two classes: (1) Those which possess no coloring power, but which are instrumental in the fixation or development of coloring matters upon the fiber. (2) Those which are true coloring matters. First Class. Compounds Instrumental in the Fixation of Color- ing Matters upon the Fiber, although Possessing no Coloring Power Themselves. The compounds included under this heading are frequently spoken cf as fixing agents, but when used in this broad and indefinite sense the term frequently leads to confusion rather than to enlightenment. In order to eliminate this con- 447 448 ELEMENTS OF INDUSTRIAL CHEMISTRY fusion as far as possible, we will classify the most important compounds coming under this class as follows : (1) Mordants: (a) Metallic. (6) Non-metallic, (c) Acid. (2) Mordanting assistants. (3) Chemical fixing agents. (4) Mechanical fixing agents. (5) Developing agents. (6) Leveling agents. (7) Dyeing assistants. MORDANTS. Mordants in general may be defined as sub- stances capable of uniting with certain dyestuffs to form insoluble colored compounds which under the proper conditions may be more or less permanently fixed upon textile material. They may be subdivided as metallic, non-metallic, and acid mordants. Metallic Mordants. Metallic mordants are substances, usually metallic oxides or hydroxides, which are capable of uniting with certain dyestuffs, known as mordant dyestuffs, to form insoluble colored compounds which for the most part are known as color lakes. Non-metallic Mordants. The only non-metallic mordant of importance, and this of only minor importance, is sulphur. Sul- phur is sometimes used as a mordant when applying certain basic colors, e.g., malachite green upon wool. Acid Mordants. Tannic acid and various substances rich in this acid, such as sumac, gall nuts, and various bark extracts, and less frequently various fatty acids, such as oleic and stearic acids, and Turkey red oil, are the only acid mordants of impor- tance. Of these acid mordants tannic acid and its related com- pounds are the only ones commonly used, and these chiefly in the application of the basic colors to cotton material. The acid mordants are of minor importance as compared with the metallic mordants. CHEMICAL FIXING AGENTS. Under the heading of chem- ical fixing agents we will include: First. Those substances which are instrumental in the fixa- tion of various mordants upon textile material by uniting chem- ically with such mordants and holding them upon the fiber until the proper dyestuffs may be given an opportunity to unite with them. Examples: The various antimony compounds used to fix tannic acid upon cotton fiber. Various tannin compounds DYESTUFFS AND THEIR APPLICATIONS 449 used to hold iron upon the fiber as the insoluble tannate of iron when the latter is to act as a mordant with logwood or other mordant dyestuffs. Second. Those substances which cause the actual precipita- tion of the mordant usually by the double decomposition of the- mordanting principle. Example : When cotton material saturated with nitrate of iron is passed through a solution of sodium car- bonate, the basic carbonate and oxide of iron is precipitated upon the fiber, and sufficiently fixed thereon to act as a mordant. Mechanical Fixing Agents. These are substances (such as albumen) capable of holding pigments, permanently, upon the fiber, or certain gums and starches capable of holding dyestuffs and other substances upon the fiber a sufficient length of time to permit of some desirable reaction taking place. Their action is purely mechanical. DEVELOPING AGENTS. The term developing agents is applied to organic compounds which in combination with some other organic compound already deposited upon the fiber will develop a colored compound, or if united with a dyestuff already upon the fiber will form a new coloring matter possessing a more desirable or a faster color. Examples: Beta-naphthol upon the fiber, when combined with diazotized para-nitro aniline (developing agent) will produce para red. Primuline, a yellow dyestuff, when diazotized upon the fiber by treatment with nitrous acid and then combined with beta-naphthol (developing agent) pro- duces a very bright red coloring matter. LEVELING AGENTS. Leveling agents are compounds added to the dye-bath in conjunction with certain dyestuffs to assist in bringing about the level or even deposition of the latter. Ex- ample: Glauber's salt used in conjunction with the direct cotton colors. DYEING ASSISTANTS. Dyeing assistants are compounds which, added to the dye-bath, facilitate the dyeing process and are beneficial in one way or another. Examples: Sulphuric acid and Glauber's salt in the dyeing of acid colors. CLASSIFICATION OF THE DYESTUFFS. The earliest classifica- tion of dyestuffs was made by Bancroft, who divided them into two classes, substantive and adjective. He designated as substan- tive dyestuffs those capable of producing a fully developed color upon textile material without the necessary assistance of any other combining substance, and as adjective dyestuffs those requiring an intermediate combining substance {called a mor- 450 ELEMENTS OF INDUSTRIAL CHEMISTRY dant) satisfactorily to fix and fully develop the color. This grouping is still in use, but during recent years the tendency has been to use the term direct color, instead of substantive, and mordant color instead of adjective. In general the classification holds true; but there are instances where dyestuffs are substan- tive toward one fiber, but adjective toward another. This is well illustrated by the basic colors which will dye wool directly but require a mordant upon cotton. The classification which divides the dyestuffs according to their origin is of broader application. It recognizes three groups and is as follows: (1) Natural Organic Dyestuffs. Including (a) Vegetable; (b) Animal. (2) Mineral Dyestuffs. (3) Artificial Organic Dyestuffs. Though the various subdivisions of this classification, par- ticularly of the artificial organic dyestuffs, are numerous and varied in the character of the dyestuffs they include, this general classi- fication has the advantage of conciseness, and one class does not overlap another. The natural organic dyestuffs include such coloring matters as logwood, indigo, fustic, cutch and cochineal. The mineral coloring matters include Prussian blue, chrome yellow, iron buff and a number of other inorganic pigments. The artificial organic dyestuffs are the most important, and this class may be divided into twenty or more important sub- classes. They include all of the so-called coal-tar dyes, such as magenta, benzo-purpurine, acid violet, tartrazine, and the alizarines. Natural Organic Dyestuffs. For convenience we shall subdivide the natural organic dyestuffs as follows: (1) Indigo and related compounds. (2) Logwood. (3) Natural dyestuffs, producing shades of a red character. (4) Natural dyestuffs, producing shades of a yellow to brown character. Indigo. Indigo blue or indigotin occurs in many plants, chiefly those of the genus Indigofera, the Indigofera tinctoria yielding the largest quantity. The Indigofera thrive only in DYESTUFFS AND THEIR APPLICATIONS 451 tropical climates, and for several hundred years the cultivation of the indigo plant was one of the chief industries of Southern Asia, particularly India and Java. The introduction of the artificial indigo, however, has dealt a severe blow to the natural indigo industry, particularly during the past five years, and the synthetic indigo now seems likely to replace entirely the older vegetable product. The indigo plant is herbaceous in character, grows 3 or 4 ft. high, and with a stem about J in. in diameter. Indigo blue, or indigotin, as it is known chemically, does not exist as such in the plant, but is developed through the indirect decomposition of a glucoside known as indican. When the leaves and stems are steeped in water and allowed to ferment, a clear yellow liquid results which contains the indigo as the soluble indigo white. When this liquor is violently agitated, so as to expose all parts to the action of the oxygen of the air, the soluble indigo white is converted into the insoluble indigo blue. This is allowed to settle, pressed into cakes, and when dry is ready for the market. Indigo Extracts. These are prepared by the action of concentrated sulphuric acid upon indigo blue. The resulting compounds are the indigotin sulpho acids, which are freely soluble in water, and may be easily applied to wool in an acid bath. They dye wool a brighter blue than ordinary indigo, but unfortunately the dyeings produced are extremely fugitive to light, whereas vat indigo on wool produces one of the fastest blues known. The use of the former is very much restricted for this reason. The indigo extracts are of no value for cotton dye- ing. Logwood. Logwood is the product of a large and rapidly growing tree known botanically as the Hcematoxylin campechi- anum. It is a native of Central America and the adjacent islands, Jamaica being one of the chief centers of the logwood industry. Raw logwood, as the name implies, comes in the form of rough logs, which are ground or rasped into small chips. It may be used in this latter form after it has been properly aged, bur dur- ing recent years it has been more frequently put upon the market in the more concentrated form of an extract. Logwood is in every sense of the word a mordant dyestuff, a metallic mordant being required to satisfactorily fix the dye- stuff upon any textile fiber. During the dyeing process the hsematein of the logwood unites with the mordant to form an 452 ELEMENTS OF INDUSTRIAL CHEMISTRY insoluble metallic organic compound or color lake, which becomes fixed upon the fiber. Logwood is extensively used for the production of blacks upon silk. Iron mordants are depended upon almost entirely for this purpose and tin mordants occasionally. The process usually consists in alternately treating the silk with some tannin material, and an iron or a tin compound until the silk is thoroughly filled with the metallic tannate. The silk thus mordanted is then dyed in a logwood bath. By using tin compounds in conjunction with acetate of iron it is possible to weight black dyed silk as much as 300 per cent of its original weight. Soluble Red Woods. Brazil wood, peach wood, Japan wood, and Lima wood are the principal soluble red woods. They are all mordant colors, and may be applied to mordanted cotton or wool by boiling in a plain bath of the extracted color. Insoluble Red Woods. These include barwood, Saunders wood, and camwood. On account of the insolubility of the coloring matters which they contain, the ground or rasped chips of wood must be added directly to the dye-bath. They are all mordant colors. The red woods have been replaced by coal- tar colors, which give more permanent and clearer dyeings at a lower cost. Madder. Madder root, which was known to the ancients, was for many hundreds of years the most, important of the red natural coloring matters, and was used chiefly in conjunction with Turkey reds. The active coloring principle of madder is alizarine C14H8O2, and the discovery in 1868 by Graebe and Lieber- mann that alizarine could be cheaply made from coal-tar deriva- tives, soon led to the abandonment of madder as a coloring matter except in the Oriental countries where it is native. Cochineal. Cochineal is a red mordant coloring matter obtained from the dried body of an insect which is a native of Mexico and Central America. In the past, cochineal was exten- sively used for the production of scarlets and crimsons on wool in conjunction with tin and aluminium mordants. Like most of the other natural colors, cochineal has been superseded by the artificial dyestuffs. Natural Dyestuffs of a Yellow to Brown Color. The yellow natural dyestuffs include a number of vegetable dyestuffs which vary between yellow and brown. Fustic, quercitron bark, Persian berries, turmeric, weld, and cutch are the most im- portant. DYESTUFFS AND THEIR APPLICATIONS 453 Fustic or Cuba Wood. Fustic or Cuba wood is the most im- portant of the yellow dyewoocls and is still used to some extent in wool dyeing chiefly in combination with logwood. It is a mordant dyestuff being used with chromium and aluminium mordants. It is sold in the form of ground wood, but more frequently as an extract. Quercitron Bark. Quercitron bark is obtained from the bark of a species of oak which grows in the Middle and Southern States. It is a mordant color and gives brighter yellows than fustic. Its use is limited at the present time. Persian Berries. Persian berries is the name applied to the berries of the buckthorn. In the extract form it is used to a limited extent in calico printing. Turmeric. Turmeric is the ground root of a plant which grows in Asia. It dyes cotton, wool, and silk bright shades of yellow which are extermely fugitive to light and washing. Cutch or Gambia. Cutch or gambia, a coloring matter rich in tannin, is extracted from the nuts and tender portions of various forms of acacia trees growing chiefly in India. It is used chiefly for the production of browns upon cotton, also as a tannin material in silk dyeing. MINERAL DYESTUFFS. The mineral dyestuffs as a class are of minor importance in the textile industry. Various mineral pigments are sometimes used in calico printing, but in the actual dyeing process the only mineral dyes of any importance are Prussian blue, chrome yellow, chrome green, iron buff, and khaki. Prussian Blue. Prussian blue may be produced upon tex- tile material by one of two methods. The first consists of mor- danting the material with iron oxide, and then boiling in a solu- tion of potassium ferrocyanide. The second method makes use of the fact that both the ferro and ferricyanides of potassium decompose when boiled in an acid solution and from such a boil- ing solution Prussian blue is absorbed by textile material. The first process is used chiefly with cotton, while the second is better adapted to wool dyeing. Chrome Yellow. Chrome yellow is the yellow lead chromate which may be precipitated upon the fiber by alternate treat- ments with solutions of some soluble lead salt and a chromate. Chrome Green. Chrome green is a basic oxide of chromium precipitated upon the fiber by the reaction of some soluble chro- mium salt with an alkali. 454 ELEMENTS OF INDUSTRIAL CHEMISTRY Iron Buff. Iron buff is a ferric oxide precipitated upon the fiber by the reaction of some soluble iron salt with an alkali. Khaki. Khaki is a yellowish-drab color produced by the precipitation upon the fiber of a combination of ferric oxide and basic chromium oxide. Khaki when properly dyed produces an extremely fast color. Artificial Organic Dyestuffs. The natural dyestuffs were depended upon almost wholly until the discovery of mauve by Perkin in 1856. Mauve was the first of the so-called coal- tar dyes, or better artificial organic dyestuffs. Its discovery was followed by that of many similar dyestuffs, and a new era soon began in the textile coloring industry. To-day several hundred entirely different dyestuffs of this class are at the disposal of the textile colorist,and from them we can select dyes which will answer almost every requirement of shade and fastness. Classification of the Artificial Organic Dyestuffs. The arti- ficial organic dyestuffs may be classified according to their chemical derivation, their composition, or in respect to the characteristic color-forming groups which they contain. While these classifications prove very satisfactory for the color-manu- facturing chemist, they prove of little or no value to the practical textile colorist. Another classification which groups them according to their action toward the various textile fibers is by far the most practical and valuable for the student of textile coloring, and will be followed. It recognizes ten classes of color- ing matters: (1) Basic colors. (2) Phthalic anhydride colors. (3) Acid colors. (4) Direct cotton colors. (5) Sulphur colors. (6) Mordant colors. (7) Mordant acid colors. (8) Insoluble azo colors. Produced directly upon the fiber. (9) Reducible vat, colors. (10) Miscellaneous colors. Basic Colors. Chemically the basic dyestuffs belong to the class of compounds known as substituted ammonias or amines. Like ammonia they are basic in character and hence the name. DYESTUFFS AND THEIE APPLICATIONS 455 The basic colors have a direct affinity for wool and silk, but no direct affinity for cotton, and can only be applied to the latter fiber in conjunction with some acid mordant, usually tannic acid. The basic colors are characterized by their great brilliancy and high coloring power. Their fastness to light is by no means satisfactory, but their fastness to washing in most cases is very good. The Phthalic Anhydride Colors. The phthalic anhydride colors are so called because they are directly related to this compound. They included the eosines and rhodamines, and are extensively used for the production of bright pinks, particularly in silk dyeing, and less frequently in wool dyeing. They are not used to any great extent in cotton dyeing, although sometimes used in cotton printing. The phthalic anhydride colors are characterized by their re- markable brilliancy. Acid Colors. The acid colors are so called on account of their acid character, and furthermore because they dye wool so readily in an acid bath. They are of great importance in wool dyeing, about 75 per cent of all wool dyeing being accomplished at the present time by their use. The acid colors are also exten- sively used in silk dyeing, but are of no importance in cotton dyeing. From a chemical point of view the acid colors may be sub- divided according to their composition into three classes: (1) Those which are nitro compounds, i.e., those containing the nitro or NO2 group. (2) The sulphonated basic colors, i.e., those made by treating basic colors with concentrated sulphuric acid, and thereby introducing the sulphonic acid or HSO3 group. (3) Those which are azo colors, i.e., those containing the azo or — N = N— group. The dyestuffs of the third group are the most numerous and most valuable of the acid colors. Direct Cotton Colors. The direct cotton colors, as their class name indicates, have a direct affinity for cotton. All vege- table fibers readily absorb the direct cotton colors from their simple water solution, but for practical results it is advisable to make certain other additions to the dye bath. The direct cotton colors also dye the animal fibers directly, but in most cases acid colors are preferred. The direct cotton colors having a direct affinity for both animal and vegetable fibers find extensive appli- cation in the dyeing of union material composed of cotton and wool, or cotton and silk. 456 ELEMENTS OF INDUSTEIAL CHEMISTRY SULPHUR COLORS. The sulphur or sulphide colors, as they are frequently called, are in many respects similar to the direct cotton colors, but differ so entirely in many other respects that they are grouped by themselves. In recent years they have become an important factor in cotton dyeing, on account of the fastness of the dyeings they produce, and they are now exten- sively used for the production of fast blacks, blues, browns, and compound shades upon cotton. They are called sulphur colors for three reasons: In the first place, sulphur is a constituent of all of the dyestuffs of this class; sulphur and sodium sulphide are largely used in their manu- facture; and finally, sodium sulphide is almost without exception a necessary constituent of the dye-bath during their applica- tion. Artificial Mordant Colors. The true mordant dyestuffs included under this heading cannot be permanently fixed upon cotton, wool or silk, except in conjunction with some metallic mordant. They are usually fixed upon the textile material as insoluble oxides or hydroxides of chromium, aluminium, and iron and less frequently tin and copper. During the dyeing process which follows the mordanting, the mordant dyestuffs, which con- tain either hydroxyl (OH) or carboxyl (COOH) groups in their composition, react with the mordants in much the same manner as acids react with bases, the result being the formation of insoluble metallic organic compounds of a salt-like character which are known as color lakes. This reaction takes place in situ and the color lake is thus fixed upon and within the fiber. MORDANT ACID COLORS. The dyestuffs of the group known as the mordant acid colors are intermediate in general character between the acid dyestuffs and the mordant dyestuffs. They resemble acid colors in a general way, dyeing wool directly in an acid bath, but at the same time resemble the mordant colors, in that they may be applied to advantage in conjunction with metallic mordants. INSOLUBLE AZO COLORS. A number of coloring matters of the azo type exist, the insolubility of which renders the mnon- applicable by any of the methods already described. Fortu- nately the nature of the process of their formation is such that they may be produced directly upon the fiber. Many insoluble azo colors may be produced, but only two, the so-called para- nitr aniline, and alpha-naphthylamine reds have proved to be of practical value. These have been extensively used upon cotton DYESTUFFS AND THEIR APPLICATIONS 457 during the past twenty years, the former having replaced Turkey- red to a great extent. The dyestuffs of this class are also known as developed colors, because they are developed during the process of application, also as ice colors, because ice is used to attain a low temperature during their formation. The formation of the insoluble azo colors depends upon the fact that certain diazotized amino compounds produce insoluble coloring matters when brought into contact with certain naphthols or phenolic bodies. Para-nitraniline red, the most important ex- ample, is produced by padding cotton cloth with sodium beta- naphtholate, prepared by dissolving beta-naphthol in caustic soda solution, and then passing the cloth thus prepared through a bath containing a cold solution of diazotized para-nitraniline, the latter ,being prepared by the action of nitrous acid upon para- nitraniline hydrochloride. As soon as the cloth prepared as above comes in contact with the para-nitraniline solution, a bright red develops which possesses excellent fastness to light and washing. If diazotized alphanaphthylamine is substituted for the para- nitraniline a claret red color is produced of corresponding fastness. The insoluble azo colors are not applicable to wool, owing to the fact that a strong caustic soda solution must be used in dis- solving the naphthol, which would act injuriously upon the fiber. REDUCTION VAT COLORS. The reduction vat colors have come into great prominence during recent years owing to their great resistance to practically all of the color-destroying agencies, particularly light and washing. The chemistry of their appli- cation is the same as that of indigo, in fact indigo is a reduction vat color in every sense of the word. As a class these colors are insoluble in water, but when strongly reduced in an alkaline bath they form soluble, usually colorless or almost colorless, reduction compounds, which are easily absorbed by the fiber. Upon subsequent oxidation the reduced compounds pass back to the original insoluble dyestuff which becomes fixed upon the fiber. From the point of view of composition, the reduction vat colors may be divided into two classes : first, those directly related to indigo; secondly, those related to anthracene. The former may in most cases be applied to both cotton and wool, but the latter only to cotton. Another important group of coloring matters of recent develop- ment are the so-called sulphurized vat dyes. In their properties, 458 ELEMENTS OF INDUSTRIAL CHEMISTRY they may be considered as intermediate between the vat colors and the sulphur colors. But little is known in regard to their composition. The dye-stuffs known as hydron colors belong to this group. The coloring power of the reduction vat colors is weak and a comparatively large amount must be used in must cases. ANILINE BLACK. Aniline black is usually classified as one of the miscellaneous colors, for it does not belong to any of the other groups. It is in reality an insoluble black pigment pro- duced by the oxidation of aniline. When aniline is oxidized, three consecutive products are formed: (1) Emeraldine, a greenish-colored salt insoluble in water; (2) niqr aniline, formed by the oxidation of emeraldine, and (3) aniline black proper, or ungreenable black, as it is some- times called, which is formed by a still further oxidation of ni- graniline. The composition of the final product is not definitely known. Aniline black is extensively used in calico printing and the dyeing of hosiery, but cannot be used successfully in wool dyeing. In general, aniline black is applied by preparing or printing the material with a mixture of aniline hydrochloride and certain oxidizing agents and oxygen carriers, such as potassium chlorate, potassium ferrocyanide, copper sulphide, or vanadium salts, and subsequently drying and aging it by passing through an aging chamber. Aniline black is extremely fast to light, bleaching and washing. CHAPTER XXV THE PAPER INDUSTRY RAW MATERIAL. At the present time the manufacture of paper has two principal bases of supply. One of these is rags, the other is wood. Out of rags is made the highest grades of paper. RAG PAPER. All linen and cotton rags can be converted into different grades of paper according to the kind and color of the rags. Great care is used in sorting rags before delivery to the paper mill so as to get a uniform kind of rags of the same color. Buttons, pieces of metal, sticks, stones, rubber and all foreign articles must be removed. The treatment of rags in the mill is as follows: The rags are delivered at the mill in strap iron bound bales about 3 ft. square and 5 ft. long. Often several hundred tons and sometimes two or three thousand tons are kept on hand. The rags in bales as demanded for use are taken to the rag- room, where the bales are opened by women, who make the final sorting, inspection and cutting. The finest sort goes into the best of writing paper. From this high standard to the pasteboard and cheapest wrappers are many grades supplied by the different quality of rags. A scythe-shaped knife is fastened in a vertical position to a table, by which the operator cuts the rags fine or coarse, and also separates all foreign matter that may be seen. At this stage the rags pass to the mechanical rag cutters, that cut them up into small pieces so that the duster, through which they next pass, can remove much of the loose dirt. These machines dust out oftentimes five per cent or more of the weight of the rags and also open them up so that the chemicals in the votaries or cookers into which they are placed can better penetrate and act upon them. RAG BOILERS. Rag boilers are of several types. The stationary upright cylinders are provided with a manhole on top for filling, the cover to which is bolted on or held up by yoke and bolts. By the opening of a valve, at the bottom, the contents 459 460 ELEMENTS OF INDUSTRIAL CHEMISTRY are blown out, due to the pressure (generally about 30 lbs.) main- tained during the cooking. Steam for cooking is admitted at the bottom and the liquor circulated by an outside pump. Rotaries are horizontal cylindrical-shaped steel tanks 10 to 20 ft. long and 6 to 8 ft. in diameter with heads riveted on each end, each head having a journal upon which it rests and is turned during the cooking process. Hence the name " rotary." Through one of these journals steam enters for cooking. The rotary may have one or two manholes with covers affixed, as in the upright, for filling in the stock. During the filling men go into, the rotaries and pack the stock into the ends so as to get in enough properly to fill the boiler. RAG BOILING. The chemicals, a certain number of gallons of a solution of caustic soda or soda ash and caustic lime, or a milk of lime made by slacking and boiling caustic lime in water, are added. In all cases where lime is used it should be strained in order to remove unslacked parts before being passed into the cooker. When the liquor is all in, the covers are adjusted and the steam turned on. The pressure generated (generally 15 to 30 lbs.) and the chemicals reduce the foreign matters, such as grease loading materials, dirt, etc., and open up the fibers so that in the next operation of beating they can be perfectly cleaned and reduced to the desired length. Some manufacturers blow off the cooking liquor of the rotaries and run in fresh water to wash the stock in the rotaries, but generally the stock is dumped as soon as cooked and pressure lowered by removing the covers of the manholes. Sometimes the stock is allowed to stay in piles for several days in order to ripen after it is cooked. It is eventually taken to the beater engine. BEATER ENGINE. This is a Holland invention, sometimes called a Hollander, for washing, beating and reducing the fibers of the paper stock. The beater engine is an oval-shaped tub about 20 ft. long by about 3 ft. high by about 8 ft. wide. They are made of wood or iron shell with floor of wood or cement and are often lined throughout with copper. A partition, the " mid- feather," extends as far as the rectangular part of the body. A beater roll 4 to 5 ft. in diameter with heavy knives parallel to the shaft is fitted into its face and is suspended in one of the divisions, nearly filling it. This roll which consists of a number of steel plates standing on edges bolted together, can be raised or lowered nearly onto the bedplate by the beater man. The rais- ing or lowering of the roll determines the ultimate length and in a THE PAPER INDUSTRY 461 great measure the condition of the fiber when finished. Between the roll and the bedplate all of the stock must pass. The cir- culation of the stock around the beater is given by the roll, which acts as a paddle wheel. While the stock is washing, clean water is added at one side of the roll. This is thoroughly mixed with the stock as it passes under the roll and on the other side a re- volving drum washer with a fine wire on its face is pressed into the pulp. The dirty water is thereby removed from the stock. This process is continued until the stock is clean, during which time the roll or bedplate is raised so that but little cutting is done. At this point the stock is often bleached in the beater by means of a solution of calcium hypochlorate, gen- erally called bleach. This bleach is made by mixing common bleaching powder with water and allowing the lime sludge to settle out, Only a clear bleach solution testing about 4 to 5° Be. should be used. When bleached to the requisite color the stock is either dumped to a drainer to finish the bleaching or to be thoroughly washed; or it is washed in the beater by the addi- tion of more water and oftentimes some antichlor is added to hasten the killing of the bleach. Washing is kept up until these chemicals are washed out, then the roll is gradually lowered and the pulp is reduced to the proper condition. When nearly " ready " the required color, if any, is put into the beater, then size, if it is to be engine sized, is added. The size is made with soda ash about one part, rosin about four parts, dissolved and thoroughly boiled in water, well diluted, and then alum intro- duced to set the sizing onto the fibers. The stock is run in the beaters a short time and then dropped into the stuff chest, where it is kept well stirred until it is wanted on the paper machine. JORDAN ENGINE. In its passage to the machine the stock is generally run through a Jordan engine, that reduces its fibers to final readiness for the sheet of paper. This engine is a cone- shaped plug, about 4 ft. long, made up of steel bars and hard wood, that fits into an iron sleeve or hollow cone made to receive it, being lined with a filling similar to that on the plug. Through this Jordan all the stock passes, and by the closeness of the plug to the sleeve the stock is finally reduced to the proper condition for the machine. It is then sent to the machine stuff chest, from which it is pumped to the flow box, where the right quantity of water is added to make it flow properly through the screens. The screens remove all particles too coarse to go into a sheet of paper. The stock passing through the slots, which are generally 462 ELEMENTS OF INDUSTRIAL CHEMISTRY about j 1 ^ of an inch in width, drop to the apron and then onto the wire of the machine, if it is a Fourdrinier. FOURDRINIER MACHINE. Paper may be made on the Four- drinier type, with a wire at the wet end upon which to form the sheet; the Harper type with felt and wire, or the cylinder machines; the difference being principally at the wet end, where the paper is formed. The drying ends are as a rule similar. The cylinder machines have from one to six vats, with cylinders in each, making a sheet of paper that is laid on the next in front, so that when finally they go to the felt it is a built-up sheet of one/ two or more sheets of paper according to the number of vats used to make it. When dry the whole sheet can be split up into the different sheets it is made out of. Much of the heaviest paper is made on this machine, which, however, is not a fast running one. The paper machine in general use for news and many other kinds of paper as well as rag is the " Fourdrinier/' which, while it does not make as thick a sheet as the others, can make light as well as medium weights easier, change quicker, run faster and produce a good tonnage. The wire of the Fourdrinier machine is made endless, i.e., its ends are woven together so that it will pass around the rolls like an endless belt and it is stretched out like a horizontal oblong table. It is supported by a series of brass rolls at intervals, as demanded by the work to be done. Its width varies from 36 to 200 inches, the length varying in due proportion. A rubber deckel strap about 2 in. square runs at each side to hold the pulp and water on the wire, also by the moving in or out of the deckel straps, the width of the sheet can be changed to meet the demand. The proportions of these parts are such that the sheet of paper can remain on the wire long enough to get rid of its superfluous water by draining through the wire, by squeezing out water in passing between presses, couch rolls, over suction boxes, etc. This wire is one of the most important and costly parts of the machine. Its condition means the appearance of the sheet of paper. Great care is taken to keep knots of stock, stray pieces of iron or wood or any hard foreign matter, off the wire, as a puncture, a tear, or any damage to it means a shut down of the machine until it is made as nearly perfect as possible. The wire must be kept clean so that the water can freely pass through it any- where. Should it plug up, the stock is shut off and the plugs cleaned off, as a thin spot in the sheet of paper would show each time the spotted section carried the sheet along. The sewing THE PAPER INDUSTRY 463 of the wire is a delicate piece of work and must be done so as to match the weave of the wire, and not leave a mark on the sheet of paper. The sheet of paper is fully formed on the wire. While in the forming state the fibers of the sheet are felted together by the shaking motion, which, although a very short stroke, in itself seems to make a felting of fibers that distinguish a tough Four- drinier-made sheet from a cylinder-made sheet, wherein the fibers all run in about the same direction. There is also often a dandy roll that places a name or figure in the paper, such as one can see when it is held up to the light. This stamps the name into the sheet of paper while it is wet and is sometimes called a " watermark." With all this manipulation two-thirds of the weight of the sheet of paper before going to the steam dryers is water. At the end of the wet end nearest the dryers is the last press through which the wire passes. The sheet of paper will now be well formed and leave the wire and stick to the surface of the top roll. A sharp-edged scraper, called a doctor, prevents the sheet from passing entirely around the press. At this point the back tender strips off the roll a 2- or 4-in. wide piece and carries it across the gap to the first dryer. As the speed of the machine is from 60 to 600 ft. a minute for this sheet of paper much dex- terity is required at this place. A man stands at the press roll, gradually working the strip that he started tearing off at the end of the press, across to the other end, making a diagonally cut sheet that eventually grows from the 2-in. wide strip to one the full width of the sheet of paper. The dryers are steam-heated, hollow cast-iron cylinders 3 or 4 ft. or more in diameter with a width of from 36 to 200 ins., as the machine may be built, placed one above the other. A strong cotton duck dryer felt is held up to the bottom dryers by rollers in order to hold the wet sheet up to the hot surface. The sheet of paper goes about two-thirds around the bottom dryer, up and over to the top dryer, where it comes into contact with as much of that surface as it can and drops down to the second bottom dryer. This is repeated until it has come into contact with all of the dryers of the machine (ten or sixty, according to the make) , when it leaves the machine and is passed by hand to the reel or up to the top pair and down between the others of a stack of calender rolls, between which it is run to smooth or polish the surface of the sheet. From the calender it passes to the reels; from the reels through the slitters that cut the sheet into the 464 ELEMENTS OF INDUSTEIAL CHEMISTRY width desired and then to the winders, where it is wound up into rolls. When demanded these rolls are taken to an apparatus called a supercalender, where the surface of the sheet is further polished by running between heavy steel rolls, and then it goes to the cutters, where it is cut up into any size of sheets demanded. WOOD PAPER. From the different varieties of spruce, pine, fir, hemlock, poplar, and other woods, we obtain practically all of our newspaper, nearly all even of our book paper, and a large portion of our writing papers. On the arrival of the wood at the mill, if it is to be chemically treated, it is generally piled up so that it may dry; it is allowed to thus season in the pile for one, two or perhaps three years. This seasoned wood loses much of its sap and water and requires less chemicals to convert it than the green wood directly from the forest. For the mechanical pulp a fresh green wood produces better fiber and is easier ground up than the dry seasoned wood. For any of the treatments the bark must be removed, which is done by a machine called a barker or by the hand draw-shave. In the wood paper industry the principal methods of treating wood to produce fiber are by grinding, producing ground wood or mechanical fiber, and cooking by either the caustic soda or the sulphite process. MECHANICAL PROCESS. The mechanical process consists of placing blocks of wood about 18 ins. long in apertures, called pockets, of a heavy cast-iron frame that encases a large grind- stone. This grindstone revolves at about 200 revolutions per minute, a stream of water plays against its face to keep the wood from burning, as it is pressed against the face by hydraulic pres- sure of about 30 pounds. The result of this is the reduction of the wood to a fine pulpy mass, which is called mechanical pulp or ground wood. This is floated by water on to a coarse screen, by which the pieces of wood that have not been ground up are removed. The pulp goes to a fine screen, through which the mechanical pulp, that is, the right kind to go into the making of newspaper or other papers, passes. This pulp now goes to the beaters in the beater room to be mixed with sulphite pulp or other stock, according to the grade of paper it is desired to manufacture, and from the beaters goes to the paper machine, as described under Rag Paper, or to a wet machine, which is an apparatus for getting the pulp into a state dry enough to handle. The Wet Machine is a wooden vat 6 ft. wide, 8 ft. long and 5 ft. deep, into which the mixture of water and ground wood is pumped. A THE PAPER INDUSTRY 465 bronze cylinder about 3 ft. in diameter by 6 ft. long, covered with a brass wire net of 60-mesh, is immersed in the mixture in such a manner that the water passes through the meshes of the wire, leaving the pulp sticking to its surface. A coarse woolen blanket, called a felt, is pressed against the cylinder mold by a heavy couch roll. The blanket automatically picks off the pulp from the face of the cylinder, carries it along on its surface over a suction box and between heavy press rolls, that extract quantities of water from it and leave it with from 35 to 50 per cent of pulp. One of the rolls of the press is of hard maple wood, which picks the pulp from the blanket when it comes in contact with it. As the press roll revolves, the pulp is continuously added to it from the blanket until the sheet is thick enough, in the judgment of the press tender; who then with a sharp pointed wooden pin cuts it off by passing the point under the sheet close to the wood roll, across the face of the roll. The sheet of pulp is rolled off on a table, folded up, weighed and is then ready for shipment or storage. SODA PROCESS. The caustic soda liquors are made by dissolving soda ash in water, and to this solution adding about 55 to 60 per cent of freshly burnt pure quicklime, bringing the mass to a boil, mixing it thoroughly by stirring, then al- lowing the calcium carbonate produced, to settle to the bottom. The clear caustic liquor is siphoned off, and the lime sludge washed two or three times with water to remove as much of the caustic soda as possible. Poplar wood and kindred species are principally used in the soda process, as they yield easiest to this treatment, requiring a smaller amount of caustic soda for reduction than do other woods. The well-seasoned wood is brought to the mill where it is in- spected and all bark, dirt and black knots removed, as these make objectionable color and dirt in the pulp and paper. These sticks of wood are then taken to a machine called a chipper, which slices off the wood into slices similar to a sliced onion that break into chips about f inch long by 1 inch by ^ inch. The thickness of these chips will generally be the annual growth of the wood. The chips are screened to remove the sawdust, knots and coarse pieces; the latter passed through a rechipper, to reduce to the proper size. The chips are stored in large bins over the digesters, into which they are run by gravity. The digesters for the soda process are made of steel 1 inch thick and are some- times 50 feet high by 10 feet in diameter. They are filled full 466 ELEMENTS OF INDUSTRIAL CHEMISTRY of chips and then a certain amount of the caustic soda solution of a density of 8 to 10° Be. is added, according to the character of the wood to be cooked. When filled, the cover of the digester is bolted down and steam is turned on through the bottom. In the soda digesters there is a false bottom, which allows the hot liquor to pass down through it. There is gener- ally an ejector under this false bottom, through which steam is passed, which lifts the cooking liquor at the bottom, carries it through a pipe to the top of the digester and sprinkles it over the chips, thus making a continuous circulation, that produces thorough cooking. The cooking of the chips dissolves everything except the cellulose fibers. When completely cooked, the contents of the digester will be found to have shrunk one- quarter to a third of its bulk, but at this point the chips retain their original form. A cooking pressure of 90 pounds is maintained in the digest- ers for from 8 to 10 hours, with frequent opening of the relief valve at the top to draw off gas, when a sample of pulp is drawn to ascertain if the wood is properly cooked. When the operation is completed a valve of 6 or 8 inches diameter at the lower part of the digesters is opened and the entire mass is violently blown out of the digester into a suitable receiving tank This violent action and the impact of its contents serves to shatter or destroy the original form of the chips and a pulpy mass of fiber results. The liquor which has been employed for the reduction, now called black liquor, is carefully drawn off, by repeated washing with weaker liquors or water in the wash tanks evaporated to a consistence of 35 to 40° Be. by means of some suitable evaporator, generally a yaryan, for evaporation. It goes now to a rotary furnace, where it is further dried, and tne tar and other wood products are burned up, leaving the soda mixed with charcoal. This black mass is called " black ash " and is put into the tank. The soda which it contains is leached out and is used over again with addition of fresh soda ash and caustic lime. A recovery of from 85 to 90 per cent of the original soda ash used is generally obtained and this materially reduces the cost of chemicals employed. The profits of the mill are largely dependent upon this part of the manufacture. All soda fibers when cooked and washed clean from the cooking liquors are somewhat colored, and if a white paper is desired they must be bleached to the desired whiteness. If a colored paper is demanded, the color desired can be made in many cases without THE PAPEE INDUSTRY 467 recourse to bleaching. The pulp when washed clean is passed through screens, which remove from it uncooked wood and coarse matters, and either goes to the beaters, where it is mixed with other fibers in the beaters to make the desired grade of paper, or it is bleached if required and then pumped to the wet machines previously described, to put into condition for handling in ship- ment or storage. Soda fiber is a soft stock and is largely used in the better magazine, book and writing-paper grades. It is of a soft, spongy-like feeling to the fingers and is a quality desired in paper used for books. It is a fiber that does not deteriorate by time, as the chemicals that have produced it do not have a rotting effect upon it unless it is overbleached. Its selling price when bleached is about $45 per ton. SULPHITE PROCESS. Sulphite fiber, perfected in 1885, is made by treating spruce and similar woods with sulphurous acid, combined with lime and magnesia, in special digesters made with lining to withstand the action of the corrosive acids. The largest amounts of chemical fiber is produced by this process. The spruce, fir and hemlock, from which most of this pulp is made, is piled, dried, cleaned, chipped and screened and conveyed into the chip bins above the digesters practically in the same manner as for the soda process. The digesters for this process are built of heavy 1-in. steel and are very large, being often 50 ft. high by 18 ft. in diameter, made to contain 20 to 30 cords of wood at a charge. On the inside of these digesters there is generally placed a protective lining of lead fastened to the shell of the digester or a backing of about 6 ins. of Portland cement plastered onto every part of the inside steel shell of the digester; then up against this cement is laid an inside facing of vitrefied acid proof brick laid up in a cement made of Portland cement, litharge and glycerine, be- cause the acid, if it came in contact with the steel would attack it. These digesters are loaded full to the top with chips and bisulphite liquors run into the digester to within about 3 ft. of the top. This bisulphite acid or cooking acid is made by burning sulphur in specially built furnaces. In some of the countries of Europe pyrites, on account of its cheapness, is used instead of sulphur, but it has not been found profitable to use pyrites in this country. The gas first goes through cast-iron pipes to cool it, then it enters lead pipes immersed in cold water fur- ther to reduce the temperature. It next passes successively through three or four wooden tanks containing a mixture of 468 ELEMENTS OF INDUSTRIAL CHEMISTRY milk of lime that absorbs the gas as it comes in contact with it. The milk of lime best suited for this purpose is made from dolomite, often carrying 45 per cent of magnesia. The gas enters the tank at the bottom, leaving at the top, mixing with the milk of lime in successive tanks till the sulphur dioxide is finally all absorbed and the residual air passes out of the heavy vacuum pumps that pull the gas from the furnace to them. The digester with its acid is sealed and relief pipes con- nected to the top cover. The digester has no false bottom and the steam is applied directly through its cone-shaped base. The circulation of this digester depends on the passage of the steam into the bottom, working its way up through the mass of chips and liquor, causing the sulphur dioxide to break loose from its combination with the lime and magnesia and the re- sultant gas is relieved through the escape valves and pipes on the top of the cover. In the cooking of the sulphite pulp in the digester the mass of chips shrinks as it does in the soda process. During this process a pressure of 90 pounds is maintained in the digester and the temperatures run as high as 350° F. The quick cooks are made in six to ten hours, the slow cooks are steamed from thirty-six to seventy-two hours. The slow cook produces the strongest fibers that we have and it uses a weaker strength of chemicals than the quick cooks. The vertical digesters are discharged in a similar manner as with the soda ones. The pulp on being blown out strikes a bronze plate called a target and is almost white. The cooking liquor is at once washed out of the pulp by flooding the tank into which it is blown with fresh clean water. The tank has a perforated bottom connected to the sewer with a valve so as to control it easily. The water used for this washing, strange to say, must be pure and more care taken to insure its cleanliness than with the water we generally drink. This waste liquor has been experimented on extensively, but up to the present time it is found to be of value only in tanning and as a binder for slack coal in making briquets for fuel. The cooking acid must be thoroughly washed out of the sulphite pulp, because if it is not the color of the pulp will turn pink or darken to a light gray slate color. After washing, the stock is passed through screens with mesh not finer than ^ in., through which the fiber itself passes, leaving behind the knots and uncooked pieces and coarse stuff, which are sent to the scrap heap to be ground up. When sul- phite pulp is to be shipped to another mill or piled up and stored it THE PAPER INDUSTRY 469 is run over the wet machine which has been previously described. If there is a newspaper mill connected with these plants, the ground wood and the sulphite are each pumped to it and mixed together in beater engines. For the common newspapers of to-day 75 per cent of ground wood pulp is mixed with about 25 per cent of sulphite pulp, some size and alum is added and a little pink and blue aniline to give it the required white tint. After beating in the engine from a quarter to a half hour, the stock is dropped into a stock chest, from whence it is pumped to a Jordan engine, which shortens the fiber to the proper length for the sheet of paper. From the Jordan engine it goes to the stock chest that supplies the paper machine, being the same type as the one described to make rag and writing paper, only it is much heavier, costlier and runs faster. CHAPTER XXVI EXPLOSIVES An explosive is a substance, or mixture of substances, which by s proper means may be caused to decompose with great violence in such a way as to produce useful results, such as the shattering of rock or the propulsion of projectiles. A great many substances which may be classed as explosives are now known to chemistry, but for practical purposes only those explosives which can be cheaply manufactured on a large scale are of commercial impor- tance. BLACK POWDER. Black powder, or ordinary gunpowder, was the only explosive in general use up to the latter half of the nineteenth century. It is said to have been discovered in the thirteenth century, but its origin as well as the identity of its inventor is involved in an obscurity which probably can never be cleared. The first powder mill is said to have been erected at Augsburg in 1340, and from that time to this black powder has retained, with very slight variations, the composition given to it by the first powder makers. Although inferior in strength to many explosives recently discovered it is still being manufactured on an enormous scale. For a long time after its discovery black powder was used exclusively for military purposes. Its peaceful application to the mining industry began about two hundred years ago. The Raw Materials of Black Powder. The potassium nitrate (saltpeter) used in manufacturing black powder is either " natural " saltpeter or the so-called " conversion " saltpeter. " Natural " saltpeter is obtained by subjecting nitrogenous organic matter to decay in the presence of wood ashes. It has been manufactured in this manner from early times on a large scale in India. " Conversion " saltpeter is obtained by treating a solution of potassium chloride (Stassfurt salts) with the solu- tion of a soluble nitrate, such as sodium nitrate from the Chile nitrate fields. Natural saltpeter is preferred for powder making, since the 470 EXPLOSIVES 471 conversion saltpeter frequently contains traces of potassium or sodium perchlorates, the presence of which makes the powder less uniform and less reliable. The better grades of sporting and military black powders are made from the natural saltpeter. Charcoal which has been made by charring peeled, well- seasoned willow wood is preferred for powder making, although many other kinds of wood, and even hemp, flax and straw are used. For certain kinds of powder it is required that as much as possible of the volatile matter be driven off. For other kinds the wood is only partly carbonized, when the charcoal, instead of being black, has a red or brown appearance. These brown coals are used for making sporting powders and were formerly used exclusively in military powders for large caliber guns. The sulphur used in black powder manufacture is ordinary sulphur as free as possible from impurities. Process of Manufacture. The technical process of mix- ing these ingredients involves a number of separate operations as follows: 1. Pulverizing the raw materials; 5. Drying; 2. Mixing the raw materials; 6. Dusting and sorting; 3. Compressing; 7. Polishing; 4. Graining; 8. Blending. The raw materials are first pulverized in revolving drums containing bronze balls. For this operation they are taken in pairs; that is, saltpeter and sulphur; saltpeter and charcoal; charcoal and sulphur. The different pairs are then mixed in proper proportion and further ground in the ball-mill. In this condition the powder is known as " meal " and may be used without further treatment for making fireworks or fuses. It is not, however, in a form suitable for blasting or for use in firearms. The grinding in the ball-mill serves merely as a preliminary mixing. To secure a more thorough incorporation of the raw materials, the meal is next ground in a mill provided with heavy edge runners. This is a type of mill extensively used in many industries (Fig. 6), and consists of two heavy, broad-edged wheels, connected by a short axle which is caused to revolve horizontally by an upright shaft. The two wheels or runners travel around a circular basin which contains the material to be ground, and which is subjected to a conbined crushing and grinding action. This operation lasts about four hours. Before grinding under the edge- runners about 10 per cent of water is added to the powder to 472 ELEMENTS OF INDUSTRIAL CHEMISTRY reduce the danger of explosion by friction. In spite of all pre- cautions the mass frequently explodes, and for this reason no person is allowed in the grinding room while the runners are in motion, the mills being started and stopped from a distance. After the grinding is complete the mass is pressed into sheets, and the sheets subjected to further pressure and consolidation in a hydraulic press. The pressure employed in these hydraulic presses varies from 100 to 110 atmospheres, the powder remaining in the press for from one-half to two hours. Sporting powders are pressed so as to obtain a specific gravity of 1.7 or 1.8, while the specific gravity of blasting powders is only about 1.5. The cakes are next broken up and the fragments passed through sieves of different mesh, which sort the material into grains of uniform sizes, the grains ranging from 0.3 millimeter to 1.8 milli- meters in longest dimension. The next step is to remove the greater part of the added water by means of dry air at a moderate temperature. When the moisture has been reduced so that the powder contains from 1.5 to 3 per cent, depending on the grade, it is again sifted so as to remove dust, which is returned to the grinding mill. The powder is then polished by rotating in wooden drums. This serves to rub off sharp corners. After a further sifting to remove dust, the powder is polished by shaking in the drum with a small quantity of graphite. Different grades of powder may be blended as required, after which the finished product is packed for the market in air-tight packages. NITROCELLULOSE. Nitrocellulose, or more properly speak- ing, cellulose nitrate, is now the chief material used in the manu- facture of military and sporting powders throughout the world. In conjunction with camphor and other substances it is also largely used in making celluloid. Nitrocellulose is not a nitro-compound, as chemists now understand that term, but is a true nitrate in which the hydroxyl groups of the cellulose molecules have been replaced by the nitrate radicle (NO3). The inaccurate designation, nitrocellulose, which was given to the substance by its early investigators, has, however, been so long in use that it is not likely to be supplanted by the more correct term. Nitrocellulose is manufactured by subjecting cellulose to the action of strong nitric acid under certain definite conditions. Raw Materials of Nitrocellulose Manufacture. The raw materials used in making nitrocellulose are cellulose (in the form of wood pulp, tissue paper, cotton wool, or cotton wastes EXPLOSIVES 473 from spinning mills) and sulphuric and nitric acids. For making nitrocellulose to be used in the cheaper grades of celluloid and in certain cheap commercial explosives wood pulp or paper may be used. For making smokeless powders for military use, only the best and purest forms of cellulose can be employed, such as cleaned and bleached cotton wool and spinning mill wastes. The so-called delint cotton is mostly employed. Preliminary Treatment of the Cellulose. The cotton wool or wastes must first be deprived of all impurities, such as oil, fat, or dirt. This is done by boiling with dilute alkali. This treatment is next followed by light bleaching by means of calcium hypochlorite, for the purpose of removing lignin substances that form unstable nitrates which would impair the stability of the product. Too vigorous a bleaching is to be avoided, as other- wise hydrocelliiloses or oxy-celluloses would result and give rise to unstable nitrates. Before the bleached cotton is subjected to the nitration it is dried so as to reduce its moisture content below 1 per cent. For this result exposure to a temperature of 105° C. for several hours is usually necessary. The^ Process of Nitration. Nitrocellulose is not a definite compound of invariable composition like calcium nitrate. The cellulose molecule can be made to take up about 14 per cent of nitrogen, but below this maximum products of many degrees of nitration can be obtained. Products of similar nitro- gen content prepared under closely similar conditions may differ widely in properties. For this reason practical operations have to be carried on with great attention to detail. The process of manufacture in outline consists in dipping the cotton into a mixture of strong nitric and sulphuric acids, allow- ing to stand for a short time, and then removing the acid and purifying the nitrocellulose. The degree of nitration and the prop- erties of the product are dependent on the temperature of nitra- tion, duration of the action of the acids, ratio of the mass of cotton to the mass of acids, and relative proportions of sulphuric acid, nitric acid, and water in the acid mixture. A variation in any one of these factors affects the degree of nitration. Nitrocellulose for use in military smokeless powders is made by nitrating cotton at 30° C. with a mixed acid containing 63 parts sulphuric acid, 22 parts nitric acid and 53 parts of water. A nitrocellulose thus made will have a nitrogen content of from 12.50 to 12.70 per cent and will be completely soluble in a mixture 474 ELEMENTS OF INDUSTRIAL CHEMISTRY of 2 parts of ether and 1 part of alcohol. Nitrocellulose of over 12.75 per cent is generally insoluble in the ether-alcohol mixture. Nitrocellulose containing 13.10 to 13.40 per cent of nitrogen is chiefly used for small arm powders and submarine mines. Nitro- cellulose for use in celluloid manufacture and for making artificial silk contains from 8 to 11 per cent of nitrogen. There are several forms of apparatus used in the operation of nitrating. The most general practice is to conduct the operation in a lead-lined iron pot or centrifuge. The mixed acid of the desired strength, which has been warmed to the required tempera- ture, is run in through a pipe leading from the acid reservoir, and the requisite amount of cotton is submerged in the acid. The bowl of the centrifuge is then covered and allowed to stand undisturbed for the requisite length of time. The fumes given off during the reaction are led away through a wide pipe. At the end of the nitration, the centrifuge is set in motion and the excess of acid removed from the nitrated product by centrifugal force. The nitrocellulose is taken out of the bowl with pitch- forks, thrown into large tanks filled with water, whereupon the centrifuge is ready for a new charge. The reaction whereby nitrocellulose is formed from cellulose and nitric acid is as follows : C24H4o02o+nHN03 = C24H 4 o-n0 2 o(N0 2 ) n . In this equation n represents any number between 1 and 11. The sulphuric acid, which constitutes more than three-fifths of the acid mixture, takes no direct part in this reaction, its func- tion being to absorb the water resulting from the chemical process, thereby keeping the nitric acid up to its full strength. This is the usual explanation of the reason for using sulphuric acid, although it may not be the true one. Purifying the Nitrocellulose. The nitrocellulose re- quires thorough purification in order to prevent it from under- going spontaneous decomposition at some later period of use or storage. To effect this purification it is repeatedly washed and boiled with clean water; but a simple boiling, even if prolonged, is not sufficient. The cotton fiber is hollow, and in this hollow space traces of acid and by-products may remain to cause trouble later on. To insure the complete removal of these impurities the crude nitrocellulose, after a preliminary boiling, is finely pulped in a " beater," very much like the " beaters " used in EXPLOSIVES 475 paper mills, after which it is repeatedly boiled and washed in fresh water. The attainment of a satisfactory degree of purification is recognized by heating a sample of the product, contained in a test tube in which is suspended a strip of filter paper which has been dipped in a solution of potassium iodide and starch, to 65° C. If no iodine is liberated within sixty minutes, the nitrocellu- lose is regarded as stable; otherwise the washing and boiling must be continued. The whole process of boiling, washing, and pulping usually requires several days. When finally purity has been obtained the nitrocellulose is usually worked immediately into the finished products. Where such working up cannot be at once proceeded with it is kept under w-ater, or in a very moist state, to obviate the danger of explosion. If it has to be dried, this operation must be conducted with care for the same reason. Nitrocellulose is seldom stored or transported unless it contains at least 15 per cent of w T ater. In outward appearance nitrocellulose does not differ from the cotton from which it is made, except that it has a somewhat harsher feel. SMOKELESS POWDERS. Powders made from nitrocellulose and other pure organic nitro-compounds are called smokeless powders on account of their comparative freedom from ash. Black pow r der, as has been said before, wmen burned leaves be- hind over one-half its weight of solid products, which naturally give rise to dense clouds of smoke. As the mineral matter of nitrocellulose rarefy exceeds 0.5 per cent the residue left on com- bustion of powders made from it gives rise to very little smoke. Owing to its extreme rapidity of combustion, pure nitrocellu- lose cannot be used in firearms, but must be made into a form wherein the rate of combustion is greatly reduced, otherwise the gun or cannon might be shattered. This transformation is effected by working the nitrocellulose into a stiff dough with a small amount of ether-alcohol mixture. The plastic mass thus formed is then run through a press similar to a macaroni press, which forms it into long rods having one or more axial perforations. In most cases there are seven of these perforations. These rods are then cut into suitable lengths, each length constituting a " grain " of the powder. The heavier the gun in which the powder is to be used, the larger are these " grains." For example, a " grain " of powder for a 12-in. gun is about 3 ins. long with a diameter of about f in. Not all military powders have the same form, 476 ELEMENTS OF INDUSTEIAL CHEMISTRY however, as the ordnance experts of the different countries have different preferences in the matter. The final step in making smokeless powder is to reduce the content of volatile matter, water, alcohol and ether by drying to within certain very definite limits. Instead of working the nitrocellulose into a colloidal mass with ether-alcohol, acetone may be used either alone or in con- junction with nitroglycerin, or other nitro-compounds. Nitro- cellulose powders with a nitroglycerin base are more uniform and reliable than straight nitrocellulose powders, but are more corrosive to the interior surface of the gun. The military powders for large caliber guns used by the United States, France and most other countries, are straight nitrocellulose powders. The English military smokeless powder is a nitroglycerin-nitrocellu- lose mixture, and is known as " cordite." STABILIZERS. It is customary to add to the military smoke- less powder a small amount of " stabilizer/' such as diphenyl- amine, which absorbs any nitrogen oxides which may be split off by spontaneous decomposition during the storage of the powder. In the absence of a stabilizer these free oxides are liable in time to cause spontaneous explosions, which have been attended in recent years with disastrous results to ships of war. NlTRO-STARCH. Nitro-starch, or rather starch nitrate, has lately been successfully manufactured for use as a blasting explo- sive in smokeless powders, and in general for all purposes to which nitrated cotton is put. Cassava starch is the most suitable variety for this purpose. The process of manufacture differs somewhat from the manufacture of nitrocellulose, the points of difference being in the use of stronger acids, and appropriate means for mixing the starch with the acid and separating the product therefrom. The advantage of starch over cotton is its compara- tive cheapness. The nitro-starch is more difficult to stabilize than the nitro-cotton. The methods used in making it are as yet trade secrets. However, nitro-starch has attained only relatively small importance commercially. Nitroglycerin and Dynamite. Explosives composed wholly or in part of nitroglycerin and closely related substances are at the present time the most important of industrial explosives. Nitroglycerin is formed from nitric acid and glycerin in accordance with the following reaction: C 3 H5(OH)3+3HN03 = C3H5(N03)3+3H 2 0. EXPLOSIVES 477 Nitroglycerin, like the analogous product of the interaction of nitric acid and cellulose, is a true nitrate and not a nitro-compound. The term " nitroglycerin " is therefore a misnomer, which, how- ever, is apparently too well intrenched in common usage to make way for the more appropriate name. The process of manufacture consists simply in adding the glycerine to the mixed acids as in the case of nitrocellulose, sep- arating the glycerine nitrate from the mixed acids and purifying it. The methods used in practice for carrying out this simple reaction, however, are very diverse, and for full details thereon reference must be had to larger treatises such as 0. Guttmann's " Manufacture of Explosives/' or Kedesdey's " Sprengstoffe." DYNAMITE. Nitroglycerin is a heavy oily liquid and in this form has but a limited applicability. For convenience in use it must be put into a form wherein it may be easily handled. This is done by causing it to be absorbed by various porous bodies, such as infusorial earth, or kieselguhr, which can be made to absorb three times its weight of nitroglycerin. Such a mixture of nitroglycerin and kieselguhr forms an earthy, friable mass, which can be loaded into paraffined paper cartridges and is sold under the name of 75 per cent dynamite, or No. 1 giant powder. This is the original dynamite as manufactured by its inventor, Nobel. Dynamites are generally classified according to the amount of nitroglycerin content. Thus, a 50 per cent dynamite means a dynamite containing 50 per cent of nitroglycerin. GELATIN DYNAMITE. Nitroglycerin^ has the property of dissolving nitrocellulose to a limited extent. A mixture of approx- imately 9 parts of nitroglycerin and 1 part of nitrocellulose forms a clear, jelly-like mass containing no inert matter, which con- stitutes a powerful explosive. The name gelatin dynamite is applied to this product on account of its jelly-like consistency, and not because it contains gelatin. Aromatic Nitro-compounds used as Explosives. Chief among these is picric acid, C6H 2 (OH)(N02)3, which is the trinitro derivative of phenol (carbolic acid). It is made by heating equal parts of phenol and sulphuric acid at 100-120° C, until the two substances have united to form phenol-sulphuric acid. This product is then dissolved in double its weight of water, the mixture being then poured into concentrated nitric acid. The resulting picric acid is separated in centrifuges. Picric acid, either as such or in the form of its ammonium salt, is used as a bursting 478 ELEMENTS OF INDUSTRIAL CHEMISTRY charge in armor-piercing shells for guns of high caliber. The famous " shimose " of the Japanese is simply picric acid in com- pact form, obtained by melting and pouring into the shell. The reason for employing picric acid in shells is that besides having certain other desirable properties, it is the most powerful explosive known. Picric acid, although a very powerful explosive, cannot be set off except through shock produced by special means. Its salts, other than the ammonium salt, are much more easily exploded than the acid itself. Trinitrotoluol has been used by the United States and other governments as a high explosive for military purposes. Trin- itrobenzol, trinitroanisol and other substances of similar consti- tution have also been used for the same purpose. Picric acid and trinitrotoluol are used to a limited extent as industrial explosives, but are considered too expensive for general use. SAFETY POWDERS. The necessity of adapting the composi- tion of an explosive to the conditions under which it is used is exemplified in coal mining, where there is the ever present danger of igniting the dreaded " fire damp." An explosive mixture of air and methane will ignite only when locally heated above a certain critical temperature for a sufficient time, or brought in contact with an open flame of sufficient duration. To be used with safety in a gassy coal mine, an explosive must not give rise to either of these conditions. Safety explosives of this character are now manufactured in fairly large number. A list of per- mitted explosives, which may be used with fair safety in coal mines, is published by the U. S. Bureau of Mines. FLAMELESS EXPLOSIVES. For certain purposes other than blasting in coal mines it is desirable to suppress as much as possi- ble the amount of heat and flame produced when an explosive is set off. In military operations with artillery at night a gun producing much flame would disclose the position of the battery to the enemy and, moreover, excessive heat erodes the interior of the gun, decreasing its life. To obviate these effects, which are chiefly noticeable with nitroglycerin mixtures, the powder may be mixed with substances like oxalic acid (Maxim's patent), vaseline, alkaline resinates, etc., which decompose under the effects of heat, producing much gas, which tends to dilute and thus lower the temperature of the gases evolved from the explosive proper. The amount of flame and the erosive action may thus be materially reduced without great sacrifice of ballistic efficiency. EXPLOSIVES 479 FULMINANTS, PRIMERS, OR DETONATORS. Explosives may be divided into two general classes according to the means required to set them off or bring about their decomposition with explo- sive effect. The first class includes those which are set off by^sim- ple ignition. To this class belong black powder and nitrocellu- lose. When a lighted match is applied to black powder, the part first heated begins to burn with great rapidity, the com- bustion being supported by the materials contained in the explo- sive itself, i.e., there is induced a chemical action between the potassium nitrate on the one hand and the carbon and sulphur on the other. The resulting process of combustion is rapidly propagated throughout the mass and there is suddenly produced a large volume of hot gas with an enormous expansive force. Comparatively speaking, however, the wave of combustion in black powder travels at a low speed. The force of the explo- sion, therefore, develops slowly and its rate of development is easily capable of measurement. The second class of explosives here considered are those whose explosive effects are not developed by mere ignition. Dynamite and picric acid, for example, when set on fire under certain con- ditions merely burn, without necessarily producing an explosive effect. If, however, picric acid or nitroglycerin (and under certain conditions, nitrocellulose also) be confined in a small space and struck a sharp blow, there is set up an explosive wave of decomposition, distinct from the wave of combustion, the difference between the two being that the former is propagated with practically immeasurable velocity. In order to bring about the maximum effect of such an explosive, it is therefore necessary to induce an explosive wave in its mass, and this in practice is accomplished by the use of a " priming charge," consisting of a small amount of some explosive which decomposes with extraor- dinary velocity. Such primers are the salts of fulminic acid, the most important being mercury fulminate. So great is the rate of decomposition of this substance when heated or struck that the expansion of the evolved gas has the effect of a blow delivered by a mass moving at a velocity infinitely great. The shock so produced against the adjacent mass of picric acid or similar body is translated into a wave of decomposition, which instantaneously transforms it into gaseous products. Mercury fulminate can be made to set off black powder and all other explosive mixtures. It is used in the form of caps or deto- nators in practically every instance where an explosion is to be 480 ELEMENTS OF INDUSTRIAL CHEMISTRY brought about, whether for industrial, sporting, or military pur- poses. All shells ased in modern warfare carry special detonators of mercury fulminate for setting off their bursting charges. Mercury fulminate is made by dissolving mercury in nitric acid in the presence of alcohol. Its manufacture and handling are very dangerous. A good substitute for mercury fulminate in primers is a mixture of potassium chlorate with powdered glass, and antimony tri- sulphide or various metallic thiosulphates. Such primary mix- tures are safer to handle than the fulminate, and for this reason are, growing in favor. CHAPTER XXVII LEATHER When the pelts of animals are allowed to remain moist they soon putrefy, while if dried they become hard and horny. To obviate these conditions, certain processes known as tanning are employed. The object of this treatment is to convert the putres- cible animal matter into a material which is permanent, and at the same time possessing sufficient softness or flexibility for the purposes for which it is intended. As these range from heavy sole leather to light kid, there are wide divergences in the processes employed, materials used, and the methods of their application. STRUCTURE OF THE SKIN. The skins of the various animals at first glance seem to have very little in common; on closer examination, however, it will be seen that they all have a similar structure, though on account of the difference in texture and thick- ness their practical application differs very greatly. The skins of lizards, alligators, fishes and serpents differ from the higher animals in that the epidermis becomes harder and forms scales. The skin is not merely a covering for the animal, but is at the same time the seat of the organs of sense and produces cercain important secretions. It consists of two principal layers, the epidermis (epithelium, cuticle) and the corium (derma, cutis, or true skin) . The epidermis is very thin as compared with the true skin which it covers, and is entirely removed preparatory to tanning; it nevertheless possesses important functions. Its inner mucous layer, which rests upon the true skin, is soft, and composed of living nucleated cells, which multiply by division and form cell-walls of keratin. These are elongated in the deeper layers, and gradually become flattened as they approach the sur- face, where they dry up, and form the horny layer. This last is being constantly worn away, thrown off as dead scales of skin, and as constantly renewed from below, by the multiplication of the cells. It is from the epithelial layer that the hair, as well as the 481 482 ELEMENTS OF INDUSTRIAL CHEMISTRY sweat and fat glands, are developed. Each hair is surrounded by a sheath which is continuous with the epidermis, and in which the young hair usually grows as the old one falls out. Near the openings of the hair-sheath upon the surface of the skin the ducts of the sebaceous or fat glands pass into the sheath and secrete a sort of oil to lubricate the hair. The base of the hair is a bulb, enclosing the hair "papilla, which is a projecting knob of the true skin and which by means of the blood-vessels contained in it supplies nourishment to the hair. The hair bulb is composed of round soft cells, which multiply rapidly, and pressing upward through the hair sheath, become hardened, thus increasing the length of the hair. The structure of the corium or true skin is quite different from that of the epidermis. It. is composed principally of inter- lacing bundles of fibers, known as connective tissue, which are cemented together by a substance more soluble than the fibers themselves. These fiber-bundles are more loosely interwoven in the middle portion of the skin, but become compact again near the flesh. The outermost layer, just beneath the epidermis, is also very close and compact. The skin is united to the animal by a network of connective tissue (panniculus adiposus), which is frequently full of fat cells, and is then called adipose tissue. This portion, together with some actual flesh, is removed in the process of fleshing. Ordinarily the corium or true skin is the only portion which is used in the production of leather. In order to obtain it in a suitable condition for the various tanning processes, the hair or wool, together with the epithelium, must be completely removed without damaging the skin itself; and especial care must be taken that the grain, or portion next the epidermis, does not suffer injury during the treatment. CLASSIFICATION OF PELTS. The pelts of animals come to the tanner in three conditions as green (fresh from the animal), salted (where salt has been rubbed on the flesh side), or dried (usually stretched on boards in the sun). The pelts so received are divided according to their size into three general classes, namely: hides, comprising the skins from large and fully grown animals, such as the cow, horse, camel, walrus. These form thick heavy leather, used for shoe soles, machinery belting and other purposes where stiffness and strength, combined with wearing qualities, are necessary. They are also cut into splits for use as shoe uppers, bag and case leather, automobile and LEATHER 483 carriage tops, furniture and upholstering. Kips are the skins of undersized animals of the above species. Skins are obtained from small animals, such as calces, sheep and goats. Kips and skins yield a lighter leather than hides. This is suitable for a great variety of purposes, such as uppers for shoes, pocket books, book bindings, gloves and fancy leather. Pelts vary in thickness and texture in different parts, being thicker on the neck and butt than on the flank and belly. The same species vary greatly, according to climatic conditions under which they are raised, and to their breeding and feed. They often show injury, such as cuts, brand marks, and sores caused by the bot-fly or warble. SOAKING. Whether the skins are green, salted, or dried they must first be soaked in water in order to remove the dirt and blood in the case of green skins, salt in the salted skins, and for the purpose of softening in the case of dried skins. It is very essential that the skins should be free from all foreign matter before entering the limes or other unhairing solutions, as the presence of salt greatly retards the plumping; while the presence of albuminous matter is apt to set up an undesirable fermentation in the after treatments. When perfectly soft and well washed the skins are removed from the soaks, thrown over a rounded beam, tails and ear-laps trimmed, and any adhering portions of flesh removed. The time of soaking varies from one or two days to several weeks, depending upon the thickness of the hide and the age and temperature of the soak. Putrid soaks soften much quicker than fresh ones; but great care is necessary in using them lest the decomposition attack the hide fiber itself. For heavy hides which soften very slowly it is found to be of advantage to run in a drum for a short time with water at a temperature of about 40° F., the tumbling movement thus materially aiding in the soft- ening process. The addition of small amounts of alkali or acid to the soak water has a material advantage in shortening the time of soaking as well as preventing the excessive loss of hide substance. For this purpose 0.1 per cent of caustic soda on the weight of the water is very satisfactory. Sodium sulphide, borax, and sodium car- bonate may also be employed, in which case about 0.3 per cent should be taken. During the past few years formic acid has come into use for this purpose, about 0.1 per cent of the weight of the water being introduced. 484 ELEMENTS OF INDUSTRIAL CHEMISTRY FLESHING. After being soaked, the skins are fleshed. This operation is for the purpose of removing any fat or flesh which has been left on the pelt by the butcher, and consists in working the hide over a beam in a somewhat similar manner to that described for unhairing, except that the knife employed is heavier and is sharp on both sides. In nearly all modern tanneries, however, the beam has been displaced by machines for the purpose. The type of machine employed for fleshing skins differs some- what from that used for hides, although the operation is similar in-each. The essential feature of the machine consists in a cylinder provided with spiral blades, which are arranged right handed on one side, and left handed on the other. By means of this kind of blade the flesh is easily removed, and the hide stretched in all directions. DEPILATION. By the term depilation is meant the removing of the hair and epidermis. This is necessary in all kinds of leather, except that to be used for furs, the soft mucous matter of the epidermis becoming affected, thus loosening the hair without materially injuring the true skin. Sweating. The oldest method of depilation seems to have been by means of incipient putrefaction, or as it is called " sweat- ing." The hides were allowed to remain in piles in a warm, damp room until the mucous matter connecting the epidermis with the dermis had decomposed, which thus loosened the hair without injuring the true skin. This method, however, often resulted in damaged stock and so the process was improved upon by allowing the hides to hang in a closed, damp room or cellar called a " sweat pit." Liming. Lime is the agent generally employed for unhairing, although it also has its disadvantages. In preparing the lime solution a quantity of fresh lime (calcium oxide) is slaked by placing in a shallow tank, similar to that used by builders, and adding sufficient water to thoroughly moisten it. At the end of one or two hours it becomes heated and falls to a powder. Sufficient water is added to form a thick paste, in which con- dition it may be kept for several weeks or even months without much change. When required for use a suitable amount is dug out, stirred with water to remove rocks, and then run into the pits. The usual method of liming is to lay the hides one at a time in the lime solution, taking care that each hide is well immersed before entering the next one. The hides are taken out (hauled) LEATHER 485 each day and the liquor well plunged up, in order to distribute the undissolved lime throughout the pit. They are then thrown back (set), care being taken to see that they are fully spread out. In some tanyards the hides are joined by hooks (toggled) and reeled from one pit to another, or to the same pit. Sometimes hides are suspended in the liquor, and by means of a paddle, or by blowing in air, the limes are kept in motion. The most common method, however, where it is desired to agitate the liquor, is to employ the ordinary paddle box and run it at intervals during the day. The action of lime on the hide is to swell up and soften the epidermis cells, dissolve the mucous layer and loosen the hair, so that on scraping with a blunt knife both the epidermis and hair are easily removed. The action on the true skin is very vigorous, causing the hide to become plump and swollen, and at the same time dissolving the cementing material of the fibers, thus causing them to become split up into finer fibrils. This swelling is prob- ably caused by the formation of a lime soap, due to the union of the lime with the fatty matter of the hide. Not only does the liming process remove the hair and epidermis, but it also is of value in the fleshing process, as it gives to the hide a greater firmness, which is very desirable when working with the knife or on the machine. The time of liming varies with the season of the year, with the kind of skins treated, and may be from three to fifteen days. The age of the lime has a great influence on the time of treatment as well as on the character of the finished product. Old limes unhair much quicker than fresh ones. It is often customary to place the hides in an old lime for several days, or until the hair and epidermis have started to loosen, then change them to a fresh lime, which produces the desired plump- ing of the fibers. Great care, however, must be taken that the limes do not become too old, as this condition will be very apt, especially in hot weather, to produce a transparent swelling of the tissue with destruction to the fiber. Arsenic Sulphide. When the red sulphide of arsenic, AS2S2, is dissolved in hot water and added to lime it increases its depilating effect. It is emploj-ed especially in fine leathers, to which it gives the necessary stretch, softness, and clearness of grain, without the loss of hide-substance and the loosening effect cased by ordinary liming. The amount used varies somewhat, but may be said to run from 0.1 to 0.4 per cent of realgar and 4 to 6 per cent of lime, reckoned on the weight of the green skins. 486 ELEMENTS OF INDUSTRIAL CHEMISTRY Sodium Sulphide. This substance when employed in strong solution, 5 per cent or over, has the effect of rapidly reducing the hair and epidermis to a sort of pulp, which may be easily swept off with a broom, or even washed off in the drum. The operation is usually conducted in a paddle, and takes about two hours for the complete removal of the hair and epidermis. The action on the hide-substance, and especially upon the cementing material, is very slight, although the grain is swollen and temporarily rendered somewhat tender. As this strong solution destroys the hair it is only used on such stock as goat skins, where the hair is of minor importance. On the other hand, when used in weak solutions, 0.25 per cent or less, in conjunction with lime, the hair is but little injured, the hair-roots and dirt being rapidly loosened with a result somewhat similar to that produced by arsenic sulphide. Arazym. It has recently been discovered by Dr. Otto Rohm that hides and skins can be unhaired and bated in one operation by means of tryptase in an alkaline solution; which, if it proves successful from a practical standpoint, will eliminate the old-time beam house methods. In conducting this process the soaked and fleshed stock is introduced into a 0.1 per cent solution of caustic soda for twenty-four hours to allow them to plump and thus open up the fiber bundles. The caustic soda is then drawn off, the skins washed in running water for a short time and enough sodium bicarbonate to make a 0.1 per cent solution introduced. The temperature of the water is raised to 90° F. and then sufficient arazym to give a 0.1 per cent solution added. The stock is run in this solution for twenty-four to forty-eight hours or until unhaired. UNHAIRING. When the process of depilation is complete the skins or hides are removed from the pits and allowed to drain for half an hour or more. They are then placed on the beam and the hair removed. In recent years various machines have been devised to accomplish the removal of the hair, and these have been brought to such perfection that the old method of hand work has been almost entirely eliminated in the modern tannery. The unhairing machine is provided with a spiral, blunt knife which revolves on a rubber roller. BATING. It is very essential that the lime, or other depilat- ing agent, should be completely removed when it has done its work, since its action is very harmful when brought in contact with tanning materials. The presence of lime also has a tendency LEATHER 487 to weaken the fiber and to produce a harsh-feeling product as well as to cause a loss in the materials employed in the currying and finishing processes. For most leather it is not only necessary that the lime be completely removed, but that the skin should be brought from its swollen to a soft and open condition. To accomplish this with the heavier classes of dressing leather, such as split hides, kips, colt and calfskins, the stock is run in a weak fermenting infusion of pigeon- or hen-manure. The time of immersion depends upon the strength of the liquor and upon the nature of the pelts under treatment. PUERING. This is a process very similar to bating, applied to the finer and lighter skins, such as glove- and glace-kids and mo- roccos, in which dog-manure is substituted for that of birds. As the mixture is used warm and the skins are thin, the process is com- plete in a few hours. Neither bating nor puering are very effec- tive in removing lime, but seem to act upon the hide substance by means of bacterial products, causing the pelt to fall, that is, to become soft and flaccid. Great care must be exercised in this treatment, in order to prevent possible decomposition of the hide, or what is known as " running of the grain," that is, if the action becomes local and the grain is eaten away in spots. During electrical storms the action becomes very much intensified, and may result in a complete decomposition of the pack, unless the skins are drawn out or the liquor greatly diluted. When the skins are removed from the dung infusion they are slightly alkaline in reaction from excess of lime and ammonia, which must be removed before they are ready for the actual tanning process. The neutralization is accomplished in various ways, and is known as drenching and pickling. PATENT BATES. During the past few years several patented bates have been introduced, which have replaced the older methods to a very large extent. These bates are of a chemical nature, a fermentative nature, or a combination of the two. Of all of these preparations the ones which are being used at present are the following: Oropon. This material is composed of ammonium chloride, wood fiber and dry pancreas. It is put on the market as a dry powder and has the advantage that no previous preparation is accessary. The quantity required is from J to 1 per cent of the weight of the stock at a temperature of from 90° to 100° F. The first action is the neutralization of the lime by the ammonium chloride, which causes the stock to fall at once; the enzymes then 488 ELEMENTS OF INDUSTRIAL CHEMISTRY exert a solvent action upon the cementing material of the hide, causing it to become open. Dermiforma. This is a preparation composed of whey, lactic acid and other organic acids. It comes on the market as a liquid and is used at the same temperature as other bates. Puerine. This compound must be fermented before use. Once started, however, it can be run for several months, it only being necessary to add fresh material for that which has become exhausted. CHEMICAL BATES. For certain classes of leather the use of ammonium butyrate, lactic acid or formic acid have been found to give very satisfactory results. Each of these is a very active deliming agent. Ammonium chloride has a solvent action upon the lime and is used in many of the patent bates. Boric acid is rather widely employed, as it not only has the power of removing the depilating agent, but hastens the tannage, gives a good color and a smooth grain. In all of the processes where chemicals only are employed the results obtained differ from those where bacterial bates are used. DRENCHING. Drenching is sometimes used as a substitute for bating, but usually follows the bating process. It not only serves to remove the lime completely, but tends to slightly plump the skins. The drench liquor is prepared by allowing an infusion of bran in warm water to ferment under the action of special bacteria which develop lactic and acetic acids. When a bath is once prepared it can be used continuously by drawing off part of the liquor, and adding fresh portions of bran and water. In neutralizing by this method the skins are entered, and the liquor moved occasionally to get a uniform contact. As fermentation becomes well established during the night, the skins will rise to the top, on account of the gas produced. The night watchman then forces them under again, by means of a heavy pole. On rising a second time they are free from lime, and in a soft and open condition. This open condition is very essential in soft leather, but is not desirable in harness or other kinds of firm and heavy leather. PICKLING. This method usually consists in drumming the skins in a concentrated salt solution to which a small amount of sulphuric acid is added. The ratio between salt and acid is usually 8 pounds of salt to 1 pound of acid. The solution should stand 1.060 sp.gr. (8° Be., 12° Tw., 60° Bk.). In some tanneries the pickling is carried out in the paddle, and fresh acid introduced LEATHER 489 after each pack has been removed. If the pickle has the correct acid strength 15 cc. of normal sodium hydroxide will neutralize 100 cc. of the liquor, using phenolphthalein as an indicator. The salt should be replenished by adding a sufficient amount to keep the specific gravity up to 1.060. The Tanning Operation. The term " tanning " origi- nally was applied to the treatment of hides and skins with some vegetable product containing tannic acid. With the introduction of chemical methods for preserving the hide substance the old term has still been retained; so that the process of tanning may mean either a treatment with mineral salts, oils, or aldehydes, as well as those methods in which vegetable substances containing tannic acid are employed. VEGETABLE TANNAGE. For the actual tanning operation, the liquor used depends entirely upon the nature of the skins or hides, and upon the kind of leather it is desired to produce. There are three general methods, however, which are in common use. The first method consists in suspending the stock in a solution of the tanning material. The second method is carried out in a paddle so that the stock is kept in constant motion dur- ing the whole or part of the operation. The third method con- sists in tumbling the stock in a drum or pin mill during the whole or part of the operation. In the heavy hides the time of treat- ment is of course very much longer than is the case with light skins. i Belt, Sole and Harness Leather. The hides as they come from the " beam house " are run in an acid liquor in order to neutralize the lime, and to bring them to a plump or swollen condition. They are then transferred to the stick pits or sus- penders; the name coming from the fact that the hides are sus- pended by the butts from sticks placed across the pit. The liquor in the first pit is very dilute, and nearly exhausted, having a density of about 10° Bk. From day to day the liquor is changed, so that a gradual increase in its strength is obtained. After the hides have remained in the suspenders from eight to ten days they are laid in pits called handlers, where a stronger liquor is employed. The weakest liquor from the youngest handler pit is run daily to the suspenders, a new and stronger liquor being- run into the pit holding the oldest and most tanned pack. As this pack is removed the next in age takes its place, while the young- est pack enters the pit containing the weakest liquor. In this manner each pack receives a change of liquor of graduated 490 ELEMENTS OF INDUSTRIAL CHEMISTRY strength, passing from about 20° Bk. to one of 40° Bk. In the handlers the hides are completely struck through or tanned and then pass to the layers. In the layers the hides are spread out as smoothly as possible and dusted with ground bark, and are piled up, alternating a layer of hides with a layer of bark. When the pit is full concentrated liquor is run in until the pack is com- pletely covered. The hides are allowed to remain undisturbed in this condition for several weeks, or until they have taken up as much as possible of the tannic acid and other material. BLEACHING AND RETANNING. In order to secure a better and more uniform color it is customary to " strip " or remove a part of the surface tannage by means of borax or weak alkali. This is usually carried out in the drum, and the excess of alkali neutralized with oxalic, sulphuric, lactic, or formic acids and thoroughly washed. The cleared hides are then retanned with sumac or other light-colored tanning material. Previous to the retanning it is also customary in most shops to remove a small skiver from the flesh-side so that the hides will have a uniform thickness and similar appearance. STUFFING. The object of this operation is to surround the fibers with fat and oil, which serves to lubricate them and render the leather more pliable, while at the same time it gives to the stock more body or weight. The process most commonly em- ployed consists in placing the sammied (damp) hides in a drum, heated to about 140° F. and running in the melted stuffing material through the trunnion. Many kinds of stuffing greases are used. One which gives very satisfactory results consists of a mixture of tallow and cod oil. After running for about half an hour the hides are removed and set out while in a warm condition. This setting out is accomplished on a machine similar to that described under fleshing. In the setting out the excess of grease is removed and the stock given a mild stretching treatment. FRAMING. From the setting-out machine the hides are placed on frames, where they are given as much of a stretch as possible and allowed to dry in a state of tension. FINISHING. On removal from the frames the hides are given a coat of wax, shellac, gelatin, blood albumen or other finishing substance and after rolling on the jack are ready for the market. In the tanning of heavy leather the above treatment is some- times varied by cutting the hides into " bends " and " bellies"; or into " butts " and " shoulders." The subsequent treatment LEATHER 491 is somewhat modified for the different portions. The tanning materials used for heavy leather vary, consisting either of one or several tanning products. The density of the liquor employed may also var} r within rather wide limits. SOLE LEATHERS. In the manufacture of sole leather, the process is very similar to the above. After tanning, however, the stock is filled with hot extract, bleached and loaded. It is then dried, sammied and rolled. Vegetable-tanned Calfskins. In preparing calfskins for the tanning process they should be well beamed and bated until they are soft and open. The washed skins are then sus- pended on sticks and allowed to hang in the tan liquor as described under hides. The strength of the liquor, however, may be some- what changed, although 8° Bk. is very satisfactory at the start. The strength is increased uniformly for six days, when the stock should be completely struck through or tanned. The skins are then removed from the suspenders, washed and horsed up to drain. When in the proper sammied condition they are shaved and retanned in sumac, to which a small amount of sulphurous acid, oxalic acid, formic acid or formaldehyde is added. The retanning may be carried out in a drum, but it is preferable to employ the paddle. When the retanning is complete the skins are again washed, treated with about 3 per cent of soluble oil, set out, and tacked on frames to dry. Having thoroughly dried they are removed from the boards, and are ready for the coloring and finishing operation. Vegetable-tanned Sheepskins. Sheepskins come to the tanner in the pickled condition containing sulphuric acid and salt. They are usually washed free from the pickle with a strong salt solution before they enter the tan liquor. These skins may be tanned in pits as described for calfskins, except that it is necessary to have a certain amount of salt in the solution. The tanning may also be carried out in the paddle. Vegetable-tanned Goatskins. At the present time practically all goatskins are tanned by the tw r o-bath chrome process. For certain kinds of fancy morocco leather, however, sumac or other vegetable tanning material is employed. The bating of goat skins is more difficult than other pelts and a more active substance has to be employed. CHROME TANNAGE. The action of chromium salts upon hide substance was first studied by Knapp in 1858, but his in- vestigations led him to conclude that their application was of 492 ELEMENTS OF INDUSTRIAL CHEMISTRY no practical value. Although other investigators took up the matter, it was not until 1884 that any really important advance was made. At this time Augustus Schultz patented his " two- bath process." In this process the skins or hides are treated with a solution of chromic acid, produced by the action of hydro- chloric acid upon sodium or potassium dichromate and afterward with a solution of sodium thiosulphate and hydrochloric acid. The hide substance takes up the chromic acid, which is sub- sequently converted to the basic condition by means of the " hypo." In 1893 Martin Dennis made a study' of the action of chromium salts as previously investigated by Knapp, and perfected a method for " one-bath tannage," on which he was granted numerous patents. Two-bath Chrome Process. While the details involved in the application of this process vary, yet chrome tanning is uniformly carried out either in a paddle or drum. Different kinds of leather require different percentages of the chemicals. In the drum tannage 6 per cent sodium or potassium dichromate and 3 per cent of hydrochloric acid, regulated on the weight of the wet skins, are dissolved in sufficient water for the proper handling of the stock. The skins or hides are placed in the drum and the chrome solution added, the drum being kept in motion. The hides or skins are worked in the solution until they have taken on a uniform yellow color which has completely struck through. They are now removed from the drum and freed from the super- fluous liquor by horsing up over night, or by putting out; the latter operation may be done by hand or on the machine. After standing for twenty-four hours the chromed stock is returned to the drum, and run for about one and one-half hours with a solu- tion of 12 per cent of sodium thiosulphate and 6 per cent of hydro- chloric acid. On removing from the drum the stock should have a blue-green color and be uniform throughout. If thor- oughly tanned no curling will occur when a strip is placed in boil- ing water. On removing from the drum the stock is horsed up for twenty-four hours to allow the chrome to set, neutralized by running for half an hour in a \ per cent sodium bicarbonate solu- tion, washed in running water for half an hour, horsed up, and allowed to drain. The reactions which take place in this process are represented in the following equation: Na 2 Cr 2 07+2HCl = 2NaCl+2Cr03+H20. LEATHER 493 The Cr03 produced combines with the gelatine, forming a compound with it. The sodium thiosulphate now acts as a reduc- ing agent upon the chromic oxide, converting it from the acid to the basic condition, the reaction taking place in two stages: 1. 2Cr03+6HCl+3Na2S203 = 3Na 2 S04+3S+Cr2Cl6+3H 2 0. 2. Cr2Cl6+Na2S203+H 2 = Cr 2 (OH) 2 Cl4+S02+S+2NaCl. The basic chloride of chromium held by the fiber is probably converted to Cr 2 (OH)6 by the action of the sodium bicarbonate used in washing. ONE-BATH CHROME. In this process the skins or hides, after coming from the puer, are washed in running water and run in a pickle for about one hour. The pickle is made by dissolving 8 lbs. of salt and 2 lbs. of sulphate of aluminium in a small amount of water, adding 1 lb. of sulphuric acid, and making up to a den- sity of 40 Bk. The object of this treatment is to neutralize any alkalinity of the puer or lime that may remain, and to ensure the stock being in an acid condition before it enters the tan.. The pickled skins are placed in the drum, the door closed, and one-third of the chrome solution introduced while the drum is in motion. At the end of fifteen minutes another third is added, and in thirty minutes the remainder. One-half hour after the last portion has been added \ per cent of sodium bicarbonate in solution is intro- duced, and the stock run for fifteen minutes longer. The hides or skins are then removed from the drum, horsed up over night, neutralized with sodium bicarbonate, thoroughly washed, horsed up again and allowed to drain. Chrome tannage by either of the processes given above may also be carried out in the paddle, but in this case the time of treatment is somewhat longer. The advantage of the paddle tannage is that a smoother grain is obtained with less danger of " pipey " leather. ALUM TANNAGE. This process is employed especially for white kid, glove and light-colored leather. OIL TANNAGE. The oldest tanning method of which we have any record was that in which the oil, fat and brains of animals were used to preserve the pelts in a soft and non-putrescible condition. The method as at present applied consists in kneading the goods in contact with certain oils and soft fats. As the fibers slowly dry the fats are worked in between them by means of the mechanical treatment which the goods undergo in the stocks. 494 ELEMENTS OF INDUSTRIAL CHEMISTRY Each fiber is, therefore, separated from its neighbor in a non- adherent condition, and at the same time is surrounded by a waterproofing material. Not only are the fibers surrounded by the oil, but at the same time a vigorous oxidation occurs, resulting in the formation of aldehydes and other insoluble oxidation products. The aldehydes produced, by virtue of their chemical activity, unite with the hide fiber, while the insoluble products coat the fibers mechanically. Oil tannage is used in the manu- facture of chamois, buff, and buck leathers. ALDEHYDE TANNAGE. The use of formaldehyde as a tanning material has recently been brought to the attention of the tanner but as yet it has not become widely employed. The leather ob- tained by this process resembles buff leather. It is very white, however, and needs no bleaching. The future of this method remains to be seen. Finishing of Dressing Leather. After the leather is tanned by any of the methods given above it must be finished in such a manner as to meet the requirements of the various pur- poses for which it is to be used. Only a few of the most important operations in the finishing of leather will be given. Soaking. On removing the dried goods from the boards or drying room they are dipped in water at a temperature of 110° F. and placed in piles or horsed up for some hours until evenly wet through or sammied. The goods may also be sammied by dipping in warm water and then covering with damp sawdust. While still another method is to steam the stock gently and run in a drum for a short time. Shaving. The object of this operation is to bring the leather to uniform thickness, and may be done by hand or by means of the shaving machine. Splitting. This operation has replaced shaving to quite an extent, especially for side leather, which is now almost uniformly split out of the limes. In this process the leather is sliced parallel to the grain surface, so that the split portions have the same area as the original leather. Among the numerous types of splitting machines in use the " band-knife " type is the most popular. The machine consists of an endless double-beveled knife which passes around two pulley wheels, one of which is attached to power. The sammied leather is pushed toward the knife, grain upward, by two feed rollers; the grain split passing over the knife and the flesh split under it. The thickness of the split can be varied from one-sixteenth of an inch up to the thickness of the hide, so LEATHER 495 that in some cases it is possible to obtain as many as five good splits from one hide. Fat-liquoring. This process differs from stuffing in that emul- sions of various oils as well as emulsions of soap and oils are em- ployed in place of the heavy fats. In recent years the use of soluble oils (sulphonated oils) has become common. The term fat-liquoring is usually applied to the light kinds of leather, while stuffing is applied to heavy leather. Coloring. The dyeing of leather has been greatly modified within recent years owing to the introduction of coal-tar colors, although for several shades the old vegetable colors are still in use. Glazing. To obtain leather with a high finish it is given a coat of egg albumen, blood albumen, or shellac, and then finished on the glazing jack. PATENT LEATHER. This kind of leather is made by varnish- ing ordinary leather. The usual method is to first degrease the tanned stock. It is then given a daub coat of boiled linseed oil and lampblack, thinned to the proper consistency with naphtha. The excess of the coating is removed with the slicker and a mix- ture of lineseed oil and guncotton applied. The hides are then baked and sunned, and rubbed down with pumice stone. Another coat of the linseed-oil varnish with pyroxylene is applied, baked, sunned and rubbed. Coloring matter is usually added to the varnish and sometimes several coats are applied. INDEX Absinthe, 427 Absolutes, 342, 348 Absorption system, 28 Acacia, 366 Acacia odors, 357 Acetate of lime, 285 Acetates, crude, 284 Acetic acid, 288 Acetone, 289 Acetylene, 246 Acid, cinnamic, 347 carbolic, 257 colors, 455 eggs, 76 sludge, 269 Acker process, 121 Agar-agar, 366 Aldehyde tannage, 494 Alkali earths, 195 Alkali metals, 195 Alkaline starches, 399 All-oil water gas, 243 Allspice oil, 360 Almond oil, 299 Alum, 108 ammonia, 108 potash, 108 soda, 108 Alum tannage, 493 Aluminium, 106 acetate, 106 chloride, 106 hydroxide, 107 nitride, 107 oxide, 106 sulphate, 107 Amalgamater, 332 Amber, 362 Ambergris, 346 American sienna, 216 American whiskey, 424 American zinc oxide, 214 Ammonia, 108 Ammonia liquor, 238 Ammonia soda process, 164 Ammonium alum, 108 Ammonium carbonate, 109 Ammonium chloride, 110 Ammonium nitrate, 110 Ammonium sulphate, 110 Amorphous phosphorus, 155 Amygdalin, 353 Aniline black, 458 Animal fats, 309 Animal fibers, 429, 430 Animal oils, 300 Anime, 363 Anise oil, 353 Anisette, 428 Anthracene, 260 Anthracite coal, 253 Anti-freezing solution, 119 Antimony, 110 fluoride, 110 Apatite, 115 Apricot brandy, 427 Aqua ammonia, 109 Aqua fortis, 92 Aquivit, 428 Arsenic sulphide, 485 Arazym, 486 Argon, 111 Arrack, 426 Arsenate of soda, 111 Arsenic, 111 acid, 111 trioxide, 111 Arsenical pyrites, 111 Arsenious oxide, 111 Artificial fibers, 429 Artificial graphite, 118 Artificial silk, 446 497 498 INDEX Asbestine, 215 Asbestos, 146 Asphalt, 275 Asphaltene, 275 Asphaltic base, 274 Aubepine, 351 Azo colors, 456 Azotin, 220 Azurite, 134 Bag filtration, 391 Bay liquor, 404 Barley, 406 Baking Japan, 379 Baking powders, 165 Ball clay, 187 Ball mill, 8 Balsam, 347 Balsam, Peru, 347 Barium, 111 carbonate, 112 chloride, 112 hydroxide, 112 nitrate, 112 oxide, 111 peroxide, 111 sulphate, 112, 215, 217 Barytes, 111, 215 Basic colors, 454 Bates, chemical, 488 Bates, patent, 487 Bating, 486 Bauxite, 108 Bayberry wax, 315 Bay oil, 354 Beater engine, 460 Beef tallow, 310 Bee-hive oven, 55 Beer, 406 carbonizing of, 413 clarification of, 413 fining of, 413 filtration of, 414 storage of, 412 tanking of, 412 Beeswax, 316 Beet sugar, 387 Belgian slag, 227 Belt dressings, 320 Belt leather, 489 bleaching of, 490 stuffing of, 490 Benedictine, 427 Benzaldehyde, 352 Benzoin, 346, 347 Benzol, 254 Bergamot oil, 354 Birch oil, 351 Bismuth, 112 nitrate, 112 Bitter almond oil, 352 Bittern, 167 Bituminous coal, 52 Black ash, 162 lixiviation of, 163 Black iron, 143 Black oil, 320 Black powder, 470 process of manufacture, 471 raw materials for, 470 Black tung oil, 294 Blast furnace, 140, 141 Blast furnace tar, 248 Blau gas, 245 Bleaching powder, 131 Blood, 220 Blubber oils, 303 Blue vitriol, 135 Boiled laundry soaps, 323 Boiled oil, 380 Boiled toilet soaps, 332 Boiler compounds, 34 Boiler troubles, 33 Boiler water, 31 Boiling oils, 380 Boiling out, 441 Boussingault-Brin process, 152 Borax, 113 Bone, 227 Bone phosphate, 227 Boric acid, 113 Boron, 113 Bottles, 200 Brandy, 425 Breakers, 398 Breaking, 372 Brewing, 406 Brewing materials, 407 Brick clays, 188 Bricks, building, 190 burning of, 192 drying of, 191 molding of, 191 Brimstone, 174 INDEX 499 Briquettes, 53 British gum, 404 Bromine, 113 Building bricks, 190 Burgundy pitch, 63 Burners, fines, 70 lump, 69 O'Brien, 70, 71 Wedge, 70, 72 Burnt ochre, 216 Butter fat, 312 Butter substitute, 312 By-product ovens, 55, 56, 57, 58 Cadmium, 114 sulphide, 115 yellow, 115 Caesium, 115 Calcination, 16 Calcium, 115 carbide, 115, 151 carbonate, 118 chloride, 119 cyanamide, 222 fluoride, 119 hydroxide, 119 hypochlorite, 130 nitrate, 119 oxide, 118, 195 sulphate, 119 sulphide, 119 Calf skins, 491 Calomel, 148 Calorimeter, 50 Camphor, 352 Camphor oil, 352 Canauga oil, 350 Candelella wax, 315 Caoutchouc, 369 Carbide furnace, 115, 116 Carbolic acid, 257 Carbolinium avenarius, 261 Carbon, 119 black, 217 disulphide, 120 tetrachloride, 120 Carborundum, 117 Carborundum furnace, 117 Carnalite, 146 Carnauba wax, 314 Car oils, 320 Carter process white lead, 209 Cassia oil, 361 Cassia odors, 357 Castile soap, 335 Castner cell, 123 Castner-Kellner process, 123 Castor oil, 298 Castorium, 347 Catalytic action, 81 Caustic potash, 157 Caustic soda, 160 Cedar oil, 358 Cellulose, 50 Cement, grappier, 180 La Farge, 180 natural, 180 Portland, 180 Centrifugal machine, 13 Centrifugal separators, 73 Centrifugals, 386 Ceramics, 177 Cereals, 408 Cerite, 121 Cerium, 121 Chalcopyrite, 134 Chalk, 115 Chamber system, 74, 75 reactions in, 74 Charcoal, 53, 217 kiln, 278 pit, 277 Chardonnet silk, 446 Char filtration, 392 Chartreuse, 427 Chaser, 5 Chemiking, 442 Cherry brandy, 427 Chili saltpeter, 195 Chinese wax, 315 Chinese wood oil, 294 Chipper, 332 Chlorine, 121 chemical properties of, 126 process of manufacture, 126 Chrome alum, 133 Chrome green, 216, 453 Chrome oxide, 216 Chrome steel, 132 Chrome tannage, 491 Chrome yellow, 216, 453 Chromic acid, 133 Chromic anhydride, 132 Chromite, 132 500 INDEX Chromium, 132 acetate, 132 chloride, 132 hydroxide, 132 oxide, 132 sulphate, 132 Cinnabar, 148 Cinnamon oil, 361 Cinnamic acid, 347 Circulating system, 76 Citral, 356 Citronella oil, 355 Citronellol, 348 Citrus oil, 354 Civet, 346 Clays, 108, 187 uses of, 190 weathering of, 190 Clove oil, 360 Coal gas, 63 manufacture of, 231 Coal tar, 247 Cobalt, 134 blue, 216 Cochineal, 452 Cocoa butter, 308 Cocoanut oil, 308 Cod liver oil, 302 Coffey still, 23, 24 Cognac, 425 Cohobation, 353 Coke, 54, 55 Cold process soap, 335 Cold water softening, 44 Colemanite, 113 Colophony, 363 Color lakes, 456 Colored glass, 200 Columbium, 134, 174 Column stills, 23 Colza oil, 298 Commercial glucose, 408 Common process, 97 Compressor oils, 321 Compression system, 28 Concentrated tankage, 224 Condensers, 235 Contact plant, 83 construction of, 82 process, 81 Continuous kilns, 178 Conveying gases, 27 Conveying liquids, 26 Conveying solids, 24 Coolers, 270 Copal, 364, 374 Copra, 308 Copper, 134 Copperas, 143 oxide, 134 sulphate, 135 Corium, 481 Corn, 408 Corn oil, 296 Corrosion, 32 Corrosive sublimate, 148 Cotton, 436 bleaching of, 438 boiling out, 438 physical properties of, 437 Cottonseed oil, 297 Cottonseed stearin, 307 Cracking, 268 Crank case oil, 321 Creelin, 258 Creme de cocoa, 428 Creme de menthe, 428 Creme de roses, 428 Creme de vanilla, 428 Creme de yvette, 428 Creosote oil, 255 Creosote salts, 258 Cresol, 257 Cresylic acid, 257 Croton oil, 298 Crown glass, 200 Crude distillation, 340 Crude oil, 60 Crude tar, 286 Crusher, 1, 2 Crushing rolls, 2, 3, 4 Crutcher, 327 Crutching, 327 Cryolite, 108 Cryolite process, 165 Crystallization, 15 fractional, 16 Cuba wood, 453 Cumarine, 350 Curacao, 428 Cus-cus, 356 Cutch, 453 Cut glass, 201 Cutting, 328 INDEX 501 Cyanide, 150, 222 Cylinder oil, 319 Cylinder stocks, 373 Dammar, 364 Dammar varnish, 371 Dark malts, 409 Dark varnish, 378 Day tank, 197 Deacon process, 128 Decorated glass, 201 Depiiation, 484 Dermiforma, 488 Dessert wines, 421 Detonators, 479 Developing agents, 449 Developing colors, 457 Devine dryer, 14 Dextrin, 44, 395 Diaphragm process, 125 Diaspore, 108 Direct colors, 455 Direct saponification, 325 Disintegrator. 6 Distillation, 22, 47 crude, 340 modern, 344 steam, 273 wood, 277 Distilled liquor, 423 Dolomite, 146 Dolphin oil, 305 Dragon's blood, 364, 365 Drenching, 488 Dry colors, 218 Dry fish scrap, 222 Drving, 14 Drying oils, 293 Dust prevention, 73 Dutch process white lead, 206 Dyeing, 447 assistants, 449 DyestufTs, 447 classification of, 449 natural, 450 Dynamite, 476, 477 Earth wax, 275 Eau de Javelle, 130 Economizers, 47 Eggs, 76 Egg oil, 306 Electric iron, 142 , Electric steel, 142 Electrolytic oxygen, 151 Elemi, 365 Elevating liquids, 26 Enfleurage process, 341 Engine oil, 318 Enriching oils, 243 Epidermis, 481 Epsom salts, 147 Erbium, 135 Essential oils, 340 Eucalyptus oils, 359 Evaporation, 18 by direct heat, 18 by indirect heat, 18 spontaneous, 18 under reduced pressure, 19 Evaporator, Lillie, 21 Yaryan, 20 Exhauster, 237 Explosives, 420 — Expressed oils, 340 Extraction, 15 Fat, butter, 312 Fats, 290, 311 animal, 309 classification of, 290 constitution of, 292 vegetable, 306 Fatty oils, 290 Feed water heaters, 41 Feed water heating, 46 Feldspar, 108 Fermentation, 411 Ferric chloride, 144 Ferric oxide, 144 Ferric nitrate, 144 Ferric sulphate, 144 Ferro-alloys, 142 Ferrous acetate, 143 Ferrous sulphate, 143 Ferrous sulphide, 144 Fertilizers. 219 calculations 228 expression of formula 220 market quotations, 220 materials, for, 219 stimulants, 219 terms used in analysis, 219 502 INDEX Filter, bag, 12 press, 12 ribbed, 11 suction, 12 Sweetland, 12, 13 Filtration, 11 rapid sand, 42, 44 sand, 40 slow sand, 42, 44 Fines burners, 70 Fining of beer, 413 Fire clays, 188 Fire bricks, 192 Fish oils, 301 Fish scrap, dry, 222 Fixation of nitrogen, 150 Fixatives, 344 Fixing agents, 448 Flake naphthalene, 259 Flameless explosives, 478 Flash light powder, 146 Flattening out, 325 Fleshing, 484 Floating soaps, 335 Floor malting, 406 Flour of sulphur, 174 Flow box, 461 Flower concretes, 342 Flower perfumes, 348 Flower pomade, 341 Flowers of sulphur, 173 Fluffy powders, 332 Fluorspar, 115, 119 Fluorine, 135 Foaming, 32 Foots, 273 Fourdrinier machine, 462 Fractional crystallization, 16 Frames, 328 Framing, 328 Frasch process, 173 French process zinc oxide, 214 French zinc oxide, 214 Fuels, 49 constituents of, 49 definition of, 49 solid, 50 Fuller-Lehigh pulverizer, 8 Fulminants, 479 Furnaces, carbide, 116 carborundum, 117 graphite, 118 Furnaces, muffle, 17 pot, 197 reverberatory, 16 revolving, 17 Siemens regenerative, 62 sulphur, 68 tank, 197 Fustic, 453 Gadolinium, 135 Galena, 144, 146 Galium, 135 Galvanized iron, 176 Gambier, 453 Gardena oil, 350 Gas engine oils, 319 Gaseous fuels, 61 Gas light mantles, 144, 174 Gasolene gas, 246 Gay-Lussac tower, 66, 67 reactions in, 76 Gelatin dynamite, 477 Geranium oil, 359 Geranilql, 348 Germanium, 135 German silver, 149 Germination, 406, 407 Gin, 425 Gingergrass oil, 356 Glass, 194 annealing of, 202 blowing, 199 casting of, 198 coloring materials for, 196 cut, 201 decorated, 201 heavy metals in, 195 machine made, 199 melting process, 198 pressing of, 199 Glauber's salt, 177 Glazer, 199 Glory hole, 199 Glost kiln, 193 Glover tower, 66, 67, 74 reactions in, 74 Glucinium, 135 Glucose, 395, 400 manufacture of, 402 Gluten, 395, 405 Gluten feed, 398 Glycerine, 336 INDEX 503 Glycerine, purification of, 339 saponification, crude, 338 soap lye, crude, 337 sources of, 336 Goat skins, 491 Gold, 135 Golds chmidt process, 132 Graining, 325 Grapes, 414 crushing of, 415 pressing, 415 stemming of, 415 Graphite, 217 artificial, 118 furnaces, 118 Grappier cements, 180 Grass oils, 355 Gray lime, 285 Gray wash, 441 Greases,_ 320 Green vitriol, 143 Griffin mill, 9 Grinding, 107 Guaiac, 365 Guano, 221 Gumbo clays, 189 Gum resins, 362, 366 Gums, 362 benzoin, 316 labdanum, 347 Gypsum, 115, 217 Haddock liver oil, 303 Hsematin, 451 Half boiled soaps, 334 Hard-wood distillation, 282 Harness, leather, 489 Hawthorn, 351 Heat of combustion, 49 Heavy oil, 255 Heavy spar, 111 Heliotrope flower, 352 Heliotropine, 352 Helium, 136 Hemp, 445 Hemp seed oil, 295 Herb oils, 360 Hides, 482 soaking of, 483 HoUander, 460 Hollow brick, 192 Hollow structural materials, 192 Hollow ware, 200 Hops, 409 Horizontal retorts, 231 Horn silver, 160 Horse fats, 311 Horse's foot oil. 305 Hydrargallite, i08 Hydrated lime, 179 Hydraulic lime, 180 Hydraulic main, 235 Hydrochloric acid, 137 purification of, 138 uses of, 138 Hydrogen peroxide, 136 Hypochlorites, 129 Hydroxy benzene, 257 Ice colors, 457 Iceland moss, 366 Ice machine oil, 321 Illuminating gas, 231 Illuminating oils, 367 Incense, 347 Inclined retort, 232 Incrustation, 31 India-rubber, 369 Indian red, 216 Indigo, 450, 457 Indigo extracts, 451 Indium, 138 Infusorial earth, 217 Ink grinding, 10 Insoluble shellac, 371 Intermittent kilns, 17 Iodine, 138 Iodoform, 139 Ionol, 356 Ionone, 356 Iovionol, 356 Iralol, 356 Iridium, 139 Irish moss, 366 Irish whiskey, 424 Iron, 139 Iron buff, 454 Iron liquor, 143 Iron ores, 139 Japan dryers, 379 Japan wax, 314 Jasmine blossom, 350 Jasmine flower, 350 504 INDEX Jaw crusher, 1, 2 Jordan engine, 461 Juniper oil, 358 Jute, 445 Kainite, 146, 147 Kaolin, 108, 187 Kauri, 365 Kestner lifts, 76, 77 Kestner stills, 81 Kettles, steam-jacketed, 18, 19 Khaki, 454 Kiei;, 442 Kieserite, 146, 147 Kiln, rotary, 183 Kilning, 407 Kilns, 18 continuous, 178 down draft, 192 intermittent, 177 ring, 179 up draft, 192 vertical, 178 Kips, 483 Kopper coke oven, 58, 59 Kornbrannt wein, 425 Krausen, 411 Krausening, 413 Krypton, 144 Kummel, 428 Kusa, 356 Labdanum, 347 Lac dye, 368 Lac sulphur, 174 Lacquer, 372 La Farge cement, 180 Lakes, 218 Lamp black, 217 Lanolin, 316 Lanthanum, 144 Lard, 312 Lard oil, 306 Lavender oil, 359 Lead, 144 carbonate, 145 chloride, 145 dioxide, 145 in oil, 211 nitrate, 145 oxide, 145 plaster, 336 Lead, suboxide, 145 sulphate, 146 sulphide, 146 Leather, 481 Leblanc process, 161 Lehr, 198, 202 Lemongrass oil, 356 Lemon oil, 354 Leveling agents, 449 Levigation, 11 Light oil, 254 Lignite, 51 Lignocellulose, 50 Lilac flower oils, 359 Lillie evaporator, 21 Lime, 177 Lime oil, 441 Lime stone, 115, 183 Lime water, 119 Liming, 484 Linde process, 151, 152 Linoxyn, 374 Linseed oil, 294 weight of, 373 Liquid air, 152 Liquid air, oxygen from, 152 Liquid fuels, 60 Liquid soaps, 334 Liquid waxes, 313 Liquor, 406 Litharge, 145 Lithographic oil, 380 Lithopone, 214 Liver oils, 302 Lixiviation, 15 Lock boxes, 266 Logwood, 451 Loom oil, 318 Lowe apparatus, 240 fuel used, 242 operation of, 241 Lubricating oils, 270, 317 choice of, 317 Luminous paints, 119 Lump burners, 69 Macerating process, 341 Madder, 452 Magnesite, 146 Magnesium, 146 cement, 146 chloride, 146 INDEX 505 Magnesium, oxide, 146 peroxide, 146 sulphate, 147 Maize oil, 296 Malachite, 134 Malt, 408 properties of, 408 Malting, 406 operations, 406 Manganese, 147 dioxide, 147 sulphate, 147 Maraschino, 427 Marble, 115 Marine animal oils, 301 Marl, 183 Mashing, 409 Massecuite, 386 Mastic, 365 \ Mastic varnish, 371 Matheson process white lead, 211 Mechanical process, 464 Meiler, 278 Melting resins, 373 Menhaden oil, 301* Mercuric chloride, 148 Mercuric oxide, 148 Mercurous chloride, 148 Mercurous nitrate, 148 Mercurous oxide, 148 Mercurous sulphate, 148 Mercury, 148 fulminate, 479 Meta cresol, 258 Metallic soap, 336 Milk of lime, 119 Milling, 333 Milling machine oils, 321 Mills, ball, 8 Griffin, 9 pebble, 9 roller, 10 soap, 333 tube, 10 Minium, 145 Minor animal fibers, 434 Mimosa, 357 Mineral black, 217 Mineral dyestuffs, 453 Mineral fibers, 429 Mispickel, 111 Mixing glucose, 404 Molding, 191 Molybdenite, 149 Molybdenum, 149 Monazite sands, 174 Monkey pots, 198 Montan wax, 316 Montejus, 102 Mordant colors, 456 Mordants, 448 Mortar, 179 Mottled soaps, 335 Movement of gases, 77 Muffle furnace, 17 Multiple effect system, 20 Musk, 345 synthetic, 346 Mutton tallow, 311 Myrrh, 347 Myrtle wax, 315 Naphtha, 267 Naphthalene, 258 Natural cement, 180 Natural dyestuffs, 450 Natural gas, 64 Natural waters, 30 composition of, 30 Neat's-foot oil, 306 Neodymium, 149 Neon, 149 Neovinol, 356 Neroli, 349 petals, 349 Neutral oils, 321 Neutralize^ 402 New mown hay, 351 Nickel, 149 coins, 149 matte, 149 sulphate, 149 Nigre, 327 Nitrate of iron, 147 Nitric acid, 91 charging of, 99 condensation of, 100, 101 distillation of, 99 manufacture of, 92 occurrence, 92 properties of, 91 Nitro-cellulose, 472, 473 purification of, 474 raw materials for, 472 506 INDEX Nitrogen, 149 fixation of, 150 Nitro-glycerine, 476 Nitro-starch, 476 Noils, 432 Non-drying oils, 299 Numerical standard, 35 O'Brien burner, 70, 71 Ochre, 217 Oil, allspice, 360 almond, 299 anise, 353 bay, 354 bergamot, 354 birch, 351 bitter almond, 352 black tung, 294 camphor, 352 canauga, 350 cassia, 361 castor, 298 cedar, 358 Chinese wood, 294 cinnamon, 361 citronella, 355 citrus, 354 clove, 360 cocoanut, 308 cod liver, 302 colza, 298 corn, 296 cotton seed, 297 creosote, 255 croton, 298 dag, 321 dolphin, 305 egg, 306 engine, 318 geranium, 359 gingergrass, 356 haddock liver, 303 heavy, 255 hemp seed, 295 horse's foot, 305 juniper, 358 lard, 306 lavender, 359 lemon, 354 lemongrass, 356 linseed, 294 loom, 318 Oil, lubricating, 270 maize, 296 menhaden, 301 neat's-foot, 306 oleo, 313 olive, 299 olive kernel, 300 orange, 355 orris, 357 palm, 307 palm kernel, 308 palma-rosa, 355 patchouly, 349 peach kernel, 299 peanut, 299 pelargonium, 359 peppermint, 361 perilla, 293 petitgrain, 350 pimento, 360 poppy, 295 porpoise, 305 pumpkin seed, 296 rape, 298 rose, 348 salad, 297 salmon, 302 sandalwood, 357 sardine, 302 sassafras, 352 sea elephant, 305 seal, 303 sesame, 297 shark liver, 303 sheep's foot, 305 soja bean, 295 soluble, 298 sperm, 313 spindle, 318 steam reduced, 271 sunflower, 295 tallow, 306 tannage, 493 tobacco seed, 295 tung, 294 turkey red, 298 vetiver, 356 watch, 318 whale, 304 white tung, 294 wintergreen, 351 ylang-ylang, 350 INDEX 507 Oil gas, 64 Oil gas tar, 248 Oilless bearings, 321 Oils, 290 animal, 300 black, 320 blubber, 303 car, 320 compressor, 321 drying, 293 eucalyptus, 359 fatty, 290 fish, 301 gas engine, 319 grass, 355 herb, 361 ice machine, 321 illuminating, 267 lilac flower, 359 liver, 302 lubricating, 357 marine animal, 301 milling machine, 321 neutral, 321 non-drying, 299 pine, 288 screw cutting, 321 semi-drying, 295 soluble, 321 spice, 361 spindle, 273 stainless, 322 tar, 287 terrestrial animal, 305 transformer, 322 turbine, 322 vegetable, 293 well, 320 Oleo oil, 313 Oleo resinous varnishes, 372 Oleo resins, 366 Olive kernel oil, 300 Olive oil, 299 Optical glass, 200 Orange flower, 349 Orange mineral, 215 Orange oil, 355 Organic dyestuffs, 454 classification of, 454 Oropon, 487 Orpiment, 111 Orris oil, 357 Orris root, 357 Ortho cresol, 257 Osmium, 151 Otto-Hoffman oven, 56, 57 Otto of roses, 348 Oxygen, 151 electrolytic, 151 from liquid air, 152 Ozokerite, 275 Ozone, 152 apparatus for, 153 machines, 153 Oven gas tar, 247 Paint clays, 189 Paint, grinding of, 7 vehicles, 217 Pale varnish, 378 Palladium, 154 Palm kernel oil, 308 Palm oil, 307 Palm wine, 426 Palma rosa oil, 355 Paper, 459 clays, 189 raw materials for, 459 Para cresol, 258 Paraffin base, 262 Paraffin wax, 272 Paste colors, 218 Patchouly oil, 349 Patent bate, 495 Paulie's process, 163 Paving brick clays, 189 Peach brandy, 427 Peach kernel oil, 299 Peanut oil, 299 Peat, 50 Peat filler, 228 Pebble mills, 9 Pelargonium, 359 Pelts, classification of, 482 Peppermint oil, 361 Perfumes, constitution of, 342 materials, 343 PeriUa oil, 293 Permanent vermilion, 216 Permutit, 45 Peroxides, 136 Persian berries, 453 Petitgrain oil, 350 508 INDEX Petrolene, 275 Petroleum, 60, 262 constitution of, 262 locality of, 263 origin of, 262 production of, 264 refining of, 264 sulphur content, 269 Phenol, 257 Phosphate, crude stock, 225 Phosphate rock, 225 Phosphoric acid, 155, 225 Phosphorus, 154 Photographic dry plates, 160 Phthalic anhydride color, 455 Pickling, 138, 488 Picric acid, 478 Pig lead, 145 Pigments, 203 applications of, 203 definitions of, 203 grinding, 7 Pimento oil, 360 Pine oil, 288 Pintsch gas, 245 Pintsch gas tar, 248 Pipe clay, 189 Pitch blende, 176 Plaster of Paris, 119, 186 Plate glass, 198 Platinum, 155 stills, 80 Plodder, 334 Plodding, 334 Poly sulphate, 95 Pomades, 348 Poppy oil, 295 Porcelain, 193 Porpoise oil, 305 Portland cement, 180 clays, 189 Pot clays, 189 Pot furnaces, 197 Pot stills, 98 Pots, monkey, 198 Potable water, 37 Potash, 227 alum, 108 crude stock, 227 Potassium, 155 carbonate, 156. 195 chlorate, 156 Potassium, chloride, 156 cyanide, 156 dichromate, 133 ferri-cyanide, 157 ferro-cyanide, 157 hydroxide, 157 nitrate, 157, 195 permanganate, 147 titanium oxalate, 175 Potato starch, 400 Pottery, 193 Praseodymium, 157 Prentice process, 93 Press filter, 12 Pressing, 328 Primers, 479 Prince's mineral, 217 Printing textile, 447 Process of nitration, 473 Producer gas, 61 Producer gas tar, 248 Prune brandy, 427 Prunty, 200 Prussian blue, 216, 453 Puering, 487, 488 Pug mills, 191 Pulp colors, 218 Pulverizer, Fuller-Lehigh, 8 Pumpkin seed oil, 296 Purification of water, 33, 40 Purifier, 238 Pyrites, burning of, 68 Pyrolusites, 147 Pyroxylin varnish, 372 Queretion bark, 453 Quicksilver vermilion, 215 Racking, 414 Rag boilers, 459 Rag paper, 459 Ramie, 445 Rape oil, 298 Rapid sand nitration, 42, 44 Realgar, 111 Reduced oils, 320 Red lead, 215 Red precipitate, 148 Red phosphorus, 155 Red wines, 420 Red woods, 452 Refrigeration, 27 INDEX 509 Remedies for oven troubles, 33 Resinous wood distillation, 282 Resins, 362, 373 Retort clays, 189 Retort gas tar, 247 Retorts, 279 for wood distillation, 279 Reverberatory furnace, 16 Revolving furnace, 17 Rhodium, 158 Ribbed filter, 11 Ring kilns, 179 Ring nits, 191 Rippling, 443 Rodinol, 348 Rodium, 167 Roller mills, 4, 10 Rolls, crushing, 2, 3, 4 Rose oil, 348 Rosin, 363, 378 saponification, 325 Rotaiy fine crusher, 3, 5 Rotary kiln, 183 Rowley process white lead, 212 Rubbing varnish, 378 Rubidium, 158 Rubv glass, 201 Rum, 426 Ruthinium, 158 Safetv powders, 478 Safrof, 352 dagger clavs, 189 Salad oil, 297 Salmon oil, 302 Salt, 165 denatured, 169 evaporation of brine, 168 properties of, 166 theory of deposits, 166 uses of, 168 working of deposits, 166 Salt cake, 162, 169 conversion of, 162 preparation of, 162 Saltpeter, 470 Salts of tartar, 156 Samarium, 158 Sandalwood oil, 357 Sandarac, 366 Sandarac varnish, 371 Sand filtration, 40 Santalol, 358 Saponification, 337 crude, 331 Saponified rosin, 326 Sardine oil, 302 Sassafras oil, 352 Scale, formation of, 31 Scandium, 158 Schnapps, 425 Scotch whiskey, 424 Scouring powders, 232 Scouring soaps, 332 Screw cutting oils, 321 Scrubber, 237 Sea elephant oil, 305 Seal oil, 303 Seaweed, 138 Second change, 325 Second rosin change, 326 Sedimentation, 11 Seed lac, 368 Selenium, 158 Semet-Solvey ovens, 57, 58 Semi-drying oils, 295 Semi-water gas, 61 Serpentine, 146 Sesame oil, 297 Settling, 327 Sewerpipe clavs, 188 Sha butter, 309 Shale oil, 274 Shark liver oil, 303 Shaving creams, 336 Shaving soap, 336 Sheep's foot oil, 305 Sheep skin, 491 Shellac, 367, 368 varnish, 370 wax, 316 Sienna, 217 Siemens regenerative furnace, 62 Sifting, 11 Silica, 194, 217 stills, 81 Silicon, 159 Silk, 435 bleaching of, 436 weighting of, 144 Silver, 159 bromide, 160 chloride, 160 iodide, 160 510 INDEX Silver, nitrate, 160 Singeing, 441 Sisal, 445 Skins, 482 structure of, 481 Skogeland condenser 103, 104 Slabber, 328 Slabbing, 328 Slack wax, 270 Slaughterhouse tankage, 224 Slibowitz, 426 Slip clay, 189 Slow sand filtration, 42, 44 Sludge acid, 269 Smalt, 111 Smaltite, 111 Smokeless powders, 475 Soap, 323 boiled laundry, 324 finishing of, 326 lye, 331 lye crude, 331 making, 323 mills, 333 powders, 331 theory of making, 323 Soaps, classification of, 323 Soda process, 465 Sodium, 16C alum, 108 arsenate, 111 bicarbonate, 165 bisulphite, 172 carbonate, 161, 195 chlorate, 172 chloride, 165 dichromate, 134 hydroxide, 161 hypochlorite, 130 nitrate, 169, 195 peroxide, 160 stannate, 175 sulphate, 169 sulphide, 172, 486 sulphite, 171 thiosulphate, 172 Soft soaps, 334 Soja bean oil, 295 Sole leather, 489, 491 Solid fuels, 50 Solid waxes, 313 Soluble oils, 298, 321 Solvay process, 164 Souring, 443 Sparkling wines, 422 Spermaceti, 316 Sperm oil, 313 Spice oils, 360 Spiegel, 147 Spindle oil, 273, 318 Spiral feed, 10 Spirit varnish, 370 Spontaneous evaporation, 18 Spuds, 270 Stabilizers, 476 Stainless oils, 322 Stand oil, 380 Starch, 395, classification of, 395 drying of, 398 manufacture of, 396 potato, 400 sources of, 396 wheat, 400 Starches, alkaline, 399 thick boiling, 399 thin boiling, 399 Steam distillation, 273, 283 Steam- jacketed kettles, 18 Steam reduced oils, 271 Stearin, 308 Steel, 142 Steel tub, 396 Steeping, 406 Stibnite, 110 Stick lac, 368 Still, pot, 98 Stills, Kestner, 81 silica, 81 Stannic chloride, 175 Stannous chloride, 175 Stoneware, 193 Stoneware clays, 188 Storage batteries, 145 Strausfurt deposits, 155, 156 Strike pan, 385 Stripping, 328 Strong change, 326 Strong water, 92 Strontianite, 172 Strontium, 172 nitrate, 172 Styrax, 347 Sublimed white lead, 212 INDEX 511 Suction filter, 12 Sugar, 381 crystallization, 384 curing of, 386 defecation process, 382 evaporation, 383, 390 extraction of, 387 purging of, 386, 390 purification of juice, 382, 389 refining, 391 Suint, 432 Sulphite process, 467 Sulphur, 172 burning of, 67 colors, 456 monochloride, 174 Sulphuric acid, 65 concentration of, 78, 79, 80 occurrence of, 65 outline of process, 66 purification of, 77 properties of, 65 raw materials for, 66 Sunflower oil, 295 Sweaters, 272 Sweating, 484 Sweetland filter, 13 Sweet wines, 421 Synthesis, 342 Talc, 146 Tallow, 310 beef, 310 mutton, 311 oil, 306 vegetable, 308 Tankage, 220 Tank furnace, 197 Tank liquors, 163 purification of, 163 Tannage, vegetable, 489 Tantalum, 174 Tar, 248 application of, 248 crude wood, 286 distillation of, 250 extractor, 236 oils, 287 Target, 468 Tellurium, 174 Terbium, 174 Terpineol, 358 Terra alba, 217 Terrestrial animal oils, 305 Textiles, 429 definition of, 429 origin of, 429 Thallium, 174 Thenard process for white lead, 411 Thick boiling starches, 399 Thin boiling starches, 399 Thessie du Motay-Marechal process, 152 Thomas slag, 227 Thorium, 174 Thulium, 175 Tile, 192 Tin, 175 Titanite, 175 Titanium, 175 Tobacco seed oil, 295 Toddy, 426 Toilet powders, 336 Toluol, 255 Tower acid, 74 Townsend cell, 125 Tragacanth, 366 Tram silk, 435 Transformer oils, 322 Transparent soap, 336 Tricalcium phosphate, 225 Trinitro toluol, 478 Tube mills, 10 Tung oil, 294 Tungsten, 176 Turbine oils, 322 Tonka bean, 351 Turkey red oil, 298 Turmeric, 453 Turpentine oil, 358 Twitchell process, 329 UebePs process, 94 Ultramarine blue, 216 Umber, 217 Unhairing, 486 Uraninite, 157 Uranium, 176 Vacuum dryer, 14, 15 Vacuum pan, 19 Valentiner's process, 95 Vanadium, 176 Vandyke brown, 217 512 INDEX Vanilla bean, 360 Vanillene, 360 Varnish, 370 classes of, 370 definition of, 370 films, 375 making of, 376 nomenclature, 374 oil, 372 outfit, 375 properties, 377 thinning of, 377 Vaseline, 274 Vat colors, 457 -Vegetable drying oils, 293 Vegetable fats, 306 Vegetable fibers, 429, 430 Vegetable non-drying oils, 299 Vegetable oils, 293 Vegetable semi-drying oils, 295 Vegetable tallow, 307 Venetian red, 215 Vertical kilns, 178 Vertical retorts, 233 Vetiver oil, 356 Vine black, 217 Violet odors, 357 Vitrex, 99 Vodka, 427 Volatile solvents, Ware clays, 189 Washing powders, 331 Water, 30 bacteriological qualities of, 38 chemical qualities of, 39 classification of, 35 for industrial use, 37 physical qualities of, 38 potable, 37 purification of, 40 softening, 44 uses of, 30 Water gas, 63, 240 all-oil, 243 tar, 248 Water glass, 159 W T ater mark, 463 Watch oil, 318 Wax, bayberry, 315 candella, 315 carnauba, 314 Wax, Chinese, 315 earth, 275 Japan, 314 Montan, 316 myrtle, 315 paraffin, 212 shellac, 316 tailings, 270 Wax wool, 316 Waxes, 290 classification of, 291 liquid, 313 solid, 314 Wedge burners, 70, 72 Weighting silk, 144 Weldon process, 126 Well oils, 320 Wet acid, fish scrap, 224 Wet machine, 464, 479 Whale oil, 304 Whiskey, 423 White arsenic, 111 White lead, 205 Carter process, 209 chemical changes, 207 corroding of, 206 Dutch process, 206 grinding of, 208 Matheson process, 211 Mild process, 212 Rowley process, 212 sublimed, 212 Thenard process, 211 White tung oil, 294 White waxes, 193 White wines, 419 Whiting, 215 Williamson machine, 243 Wine, 406, 414 fermentation of, 418 yeasts, 418 Window glass, 199 Wintergreen oil, 351 Wire glass, 198 Witherite, 111 Wolframite, 176 Wollastonite, 115 Wood. 50 alcohol, 286 distillation, 277 Wool, 430 bleaching of, 433 INDEX 513 Wool, chemical treatment of, 433 grading of, 432 grease, 431 mechanical treatment of, 432 scouring of, 431 sorting of, 432 wax, 316 Wort, boiling, of, 410 cooling of, 410 pitching, 410 Wrapping, 328 Xenon, 176 Xylenol, 258 Yaryan evaporator, 20 Yellow woods, 452 Ylang-ylang oil, 350 Ytterbium, 176 Yttrium, 176 Zinc, 176 oxide, 176, 213, sulphate, 176 Zirconium, 176 214 A SELECTED LIST OF BOOKS ON CHEMISTRY AND CHEMICAL TECHNOLOGY Published by D. VAN NOSTRAND COMPANY 25 Park Place New York American Institute of Chemical Engineers. Transactions. 8vo. cloth. Issued annually. Vol. L, 1908, to Vol. VII., 1914, now ready. each, net, $6.00 Annual Reports on the Progress of Chemistry. Issued annually by the Chemical Society. 8vo. cloth. Vol. I., 1904, to Vol. XL, 1914, now ready. each, net, $2.00 ASCH, W., and ASCH, D. The Silicates in Chemistry and Commerce. Including the exposition of a hexite and pentite theory and of a stereo-chemical theory of gen- eral application. Translated, with critical notes and additions, by Alfred B. Searle. Illus. 6^4 x 10. cloth. 476 pp. net, $6.00 ASHLEY, R. H. Chemical Calculations. Illustrated. 5^x7^. cloth. 286 pp. net, $2.00 BAILEY, It. 0. The Brewer's Analyst. Illustrated. 8vo. cloth. 423 pp. net, $5.00 BARKER, A. F., and MIDGLEY, E. Analysis of Woven Fabrics. 85 illustrations. 5^x8%. cloth. 319 pp. net, $3.00 BEADLE, C. Chapters on Papermaking. 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