MAIN LIBRARY-AGRICULTURE DEPHT '.COMMERCIAL ORGANIC ANALYSIS- A TREATISE ON ^ -"( THE PEOPEETIES, MODES OF ASSAYIM, AND PROXIMATE ANALYTICAL EXAMINATION OE THE VAEIOUS ORGANIC CHEMICALS AND PRODUCTS EMPLOYED IN THE ARTS, MANUFACTURES, MEDICINE, &c. ; WITH CONCISE METHODS FOR THE DETECTION AND DETERMINATION OF THEIR IMPURITIES, ADULTERATIONS, AND PRODUCTS OF DECOMPOSITION BY ALFRED H. ALLEN, F.I.G, F.C.S. PUBLIC ANALYST FOR THE WEST RIDING OF YORKSHIRE, THE NORTHERN DIVISION OF DERBYSHIRE, AND THE BOROUGHS OF SHEFFIELD, CHESTERFIELD, DONCASTER, WAKEFIELD, ETC. Secrmfc lEttitfon, Ulebtertr anU VOLUME II FIXED OILS AND FATS, HYDROCARBONS, PHENOLS, & A. CHUKCHILL 11, NEW BURLINGTON STREET ^ 37 //^ PREFACE. I FEEL that I cannot allow this volume to appear without a few words of apology, explanation, and thanks. My Apology is due to those who, misled by pro- mises which I had every expectation of being able to keep, have been long expecting the appearance of this volume. My Explanation of the delay in its publication is that, although nominally merely a new edition, the subject-matter has been rearranged and more than doubled in amount ; and that not only by the incor- poration of matter published since the appearance of the last edition, but also by the addition of the results of original experiments whenever the information on a particular subject appeared to be insufficient or of doubtful accuracy. In some cases, these investigations have been progressing during the passage of the book through the press. A further cause of delay has been that I have discovered the maximum limit of my strength. My Thanks are due to those chemists who have given me the benefit of their special experience in certain kinds of work, and by whose assistance some Vlll PKEFACE. of the more important articles have acquired an almost exhaustive character. The names of those to whom I am indebted in this way are duly mentioned in con- nection with the sections in the revision of which they have assisted. My thanks are also due to those members of my staff who have conducted many of the experiments already referred to, and who have shown great zeal and often made valuable suggestions. The arrangement of the subject-matter in numbered paragraphs has been abandoned as valueless. In the chapter on FIXED OILS AND FATS the specific gravities of bodies lighter than water are compared with water taken as 1000, in accordance with a widely-extended custom ; but I have not realised any advantage from this mode of expression, and hence in the subsequent chapters the densities are compared with water taken as unity. The growth of the subject-matter has compelled me to omit the chapters on the AEOMATIC ACIDS and TANNINS. They will form part of the Third and con- cluding Volume of the work, together with chapters on COLOURING MATTERS, CYANOGEN COMPOUNDS, ORGANIC BASES, ALBUMINOIDS, &c. Much of the matter for this volume is already written. ALFRED H. ALLEN. SHEFFIELD, October 1886. CONTENTS, FIXED OILS AND FATS. PAGE GENERAL CHARACTERS OF FIXED OILS AND FATS, ... 1 EXTRACTION AND PURIFICATION OF FIXED OILS AND FATS, . 3 Determination of Oils, 4 ; Purification of Oils, 7. PHYSICAL PROPERTIES OF FIXED OILS AND FATS, ... 10 Cohesion-Figures, 11; Absorption-Spectra, 11 ; Viscosity, 12; Specific Gravity, 13 ; Melting and Solidifying Points, 20 ; Behaviour with Solvents,. 25. CONSTITUTION AND CHEMICAL PROPERTIES OF FATTY OILS AND WAXES, 27 Saponification and Proximate Analysis, 29 ; Saponification- Equivalents, 40 ; Bromine and Iodine Absorptions, 47 ; Oxidation and Drying Properties, . 51 ; Temperature-Reac- tions, 53 ; Elaidin-Reaction, 57 ; Colour-Reactions, 58. CLASSIFICATION OF FATTY OILS, &c., 62 Tabular Arrangement of Fixed Oils, Fats, and Waxes, 63. EXAMINATION OF FIXED OILS FOR FOREIGN MATTERS, . . 74 Soap, 74 ; Free Acid, 75 ; Resin, 77 ; Hydrocarbon Oils, 80 ; Tabular Scheme for Separation of Foreign Matters, 87. IDENTIFICATION OF FIXED OILS, 88 Tabular Arrangement of Oils according to Density, 89. SPECIAL CHARACTERS AND MODES OF EXAMINING FATTY OILS, &c., 95 Olive Oil, 96 ; Almond Oil, 103 ; Arachis or Earthnut Oil, 105; Rape and Colza Oils, 107; Cottonseed Oil, 112 ; Sesame Oil, 114; Linseed Oil, 115; Castor Oil, 126; Blown Oil, 129 ; Turkey-red Oil, 130 ; Palm Oil, 131 ; Palmnut Oil, 133 ; Cacao Butter, 134 ; Cocoanut Oil, 136 ; Japan Wax, 137 ; Tallow, 139 ; Lard, 141 ; Lard Oil, 143 ; Butter Fat, 145 ; Butter, 148; Butterine, 151; Codliver Oil, 160; Shark- X CONTENTS. I'ACrE liver Oil, 164; Whale Oil, 166; Porpoise OH, 167 ; Sperm Oil, 168 ; Doegling or Bottlenose Oil, 172 ; Spermaceti, 174; Beeswax, 178 ; Carnaiiba Wax, 190. EXAMINATION OF LUBRICATING OILS, 192 Viscosimetry, 192 ; Solidifying Points, 201 ; Flashing Points, 201 ; Loss by Heating, 202 ; Drying Characters, 202 ; Free Acid, 203 ; Mineral Matters, 206. HIGHER FATTY ACIDS, 207 Tabular Arrangement of Fatty Acids, 208 ; General Reac- tions, 212 ; Recognition, Determination, and Separation, 213 ; Palmitic Acid, 226 ; Stearic Acid, 228 ; Oleic Acid, 232 ; Commercial Olein or " Red Oil," 237 ; Sulpholeic Acid, 240 ; Oleates, 241. SOAPS, 244 Assay and Analysis of Soaps, 250 ; Interpretation of the Results of Analysis, 270 ; Composition of Soaps, 272. GLYCEROL OR GLYCERIN, 276 Detection of Glycerol, 279 ; Determination of Glycerol, 281 ; Assay of Commercial Glycerin, 292 ; Nitroglycerin, 304 ; Assay of Dynamite, &c., 308. CHOLESTERIN, . 311 Detection and Isolation of Cholesterin, 312 ; Isocholesterin, 315 ; Wool Fat, 316 ; Lanolin, 317. HYDROCARBONS. TABULAR ARRANGEMENT OF HYDROCARBONS IN SERIES, . . 319 Paraffins, 323 ; Olefins, 329 ; Bromine- Absorptions of Olefins, 331 ; Acetylenes, 335 ; Separation of Hydrocarbons, 336. DESTRUCTIVE DISTILLATION, 338 Tabular Arrangement of Products of Dry Distillation, 341. CRUDE OILY PRODUCTS OF DRY DISTILLATION. TARS, . . 341 Crude Shale Oil, 343 ; Blast-furnace Tar, 349 ; Wood Tar, 350 ; Coal Tar, 352 ; Tabular View of the Constituents of Coal Tar, 354 ; Assay of Pitch, 369. CRUDE HYDROCARBONS OF MINERAL ORIGIN. BITUMENS, . 361 Petroleum, 362 ; Assay of Crude Petroleum, 369 ; Ozokerite, 371 ; Asphajtum, 373; Assay of Asphalt, 375. CONTENTS. xi PAGE PETROLEUM AND SHALE PRODUCTS, 379 Composition of Products, 382; Bromine-absorptions, 383; Mineral Naphtha, 384 ; Mineral Burning Oil, 389 ; Flashing Point of Kerosene, 391 ; Mineral Lubricating Oils, 401 ; Vaselene, 406; Paraffin Wax, 409; Paraffin Scale, 413; Petroleum Residues, 416. TERPENES AND THEIR ALLIES, . . . . ' . . . 416 Pentines or Hemiterpeiies, 417; Terpenes, 418; Cymene, 420: Terebenthene, 421 ; Cedrenes, 426; Polyterpenes, 426; Volatile or Essential Oils, 427; Oil of Turpentine, 436; Camphors or Stearoptenes, 442 ; Menthol, 444 ; Borneol, 445 ; Laurel Camphor, 446 ; Thymol, 447 ; Cantharidin, 450 ; Resins, 451; Copaiba Balsam, 456; Colophony, 458; Rosin Spirit, 460; Rosin Oil, 461. BENZENE AND ITS HOMOLOGUES, 466 Benzene, 469 ; Thiophene, 475 ; Nitrobenzene, 476 ; Toluene, 479; Xylenes, 480; Coal-tar Naphtha, 486; Assay of Com- mercial Benzols and Naphthas, 491 ; Fractional Distillation of Benzols, &c., 495. NAPHTHALENE AND ITS DERIVATIVES, 507 Naphthalene, 507; Naphthalene Oils, 509; Naphthols, 510; Dinitro-naphthol, 512. ANTHRACENE AND ITS ASSOCIATES, 512 Anthracene, 513; Anthraquinone, 515; Constituents of Crude Anthracene, 516; Reactions of Anthracene and its Associates, 522 ; Assay of Crude Anthracene, 528. PHENOLS. MONOHYDRIC PHENOLS, 534 Phenol or Carbolic Acid, 536; Detection of Phenol, 539; Bromo-phenols, 540 ; Commercial Carbolic Acid, 545 ; Car- bolic Powders, 547 ; Cresols, 550 ; Creosote Oils, 552. DIHYDRIC PHENOLS, 560 Resorcinol, 561 ; Creosote, 584 ; Assay of Wood Creosote, 567. ERRATA, 574 INDEX, 575 UN] ".SIT FIXED OILS AND FATS. UNDER the names of fixed oils, fatty oils, fats, and waxes, are classed a number of analogous bodies occurring naturally in animals and vegetables. When of definite chemical composition, they are also producible by synthetical methods. The term fixed or fatty oil is generally used for such mem- bers of the group as remain liquid at ordinary temperatures, but beyond the physical character of ready fusibility, there is no absolute distinction between the liquid and the solid fixed oils or fats. The liquid fats, however, contain a relatively large propor- tion of o 1 e i n or other glycerides of readily-fusible fatty acids. The waxes possess certain well-defined physical characters, and exhibit differences in chemical composition which distinguish them pretty sharply from the true solid fats. They are, however, in many respects closely related to the fats, and hence are conveni- ently described in the same division. The following are the general properties characterising the true fats and fixed oils :- 1. When pure, the fixed oils are usually colourless or of a pale yellow colour. Impure and commercial oils vary in colour from light yellow to red, and even to brown and black. Many vegetable oils have a distinct shade of green from the presence of chlo- rophyll, and show banded absorption-spectra, which is never the case with oils of animal origin. 2. The smell and taste of the fixed oils are often peculiar, and characteristic of their origin. As these characters become less per- ceptible the more completely the oil is purified, they are probably due to the presence of certain associated and difficultly removable foreign matters, rather than to the constituents of the true oil. 3. The fixed oils and fats are more or less unctuous to the touch, and if dropped in a liquid condition on paper they leave a perma- nent grease-spot, unless they are crystalline and hard enough to be rubbed off. 4. The fixed oils and fats are not fluorescent, and have no rota- VOL. n. A / 2 GENERAL CHARACTERS OF FIXED OILS. tory action on a ray of polarised light. Castor oil is stated to be optically active, but the statement is of doubtful authenticity. 5. The specific gravity of the fixed oils is less than that of water, varying between the limits of 875 and 970; but if certain ano- malous oils from marine animals be excluded, the lowest density for fixed oils is about 912 at a temperature of 15 C. In the fluid state, at the temperature of boiling water, the densities of the true fixed oils and molten fats ranges from 850 to about 910. The waxes and allied bodies are, when molten, still lighter, their density ranging from 808 to 845. 6. The fusing or melting points of the fixed oils vary within wide limits, and are liable to modification in an obscure manner by certain treatment. 7. The fixed oils and fats are practically insoluble in water, but they dissolve somewhat in absolute alcohol or strong spirit, espe- cially when hot, and are readily soluble in ether, chloroform, carbon disulphide, benzene, petroleum spirit (see " Castor Oil "), turpen- tine, and other volatile oils. The various fixed oils and fats are also readily miscible with each other. 8. The fixed oils and fats are composed of carbon, hydrogen, and oxygen, any nitrogen or sulphur existing in particular specimens being due to the presence of albuminous or other foreign matters. The chemical constitution of the fatty oils is discussed in a separate section (see page 27). 9. The fixed oils and fats are not inflammable at the ordinary temperature, though they may be burnt by means of a wick. As their name denotes, they are not capable of being distilled without decomposition. When heated alone they darken and evolve acrid offensive vapours; and when further heated to about 315 C. ( = 600 F.) carbon dioxide is evolved, together with peculiarly irritating vapours of acrolein, C 3 H 4 0, various volatile organic acids, and gaseous, liquid, and solid hydrocarbons. The tempera- ture at which these decompositions occur has been improperly called the "boiling point" of the oil, the phenomenon of apparent ebullition being really due to the escape of the gases formed by the decomposition. When caused to pass slowly through a red-hot tube the fixed oils are almost wholly decomposed into volatile pro- ducts, consisting of carbonic oxide, hydrocarbons, &c. 10. On distillation with superheated steam, fatty oils suffer a simpler decomposition, with formation of glycerol and fatty acids. This change may also be effected by acting on the oil with sulphuric acid or a strong base. The reaction is known as " saponi- fication," and is discussed at length in another section (page 29). 11. If air be excluded, the fixed oils may be preserved unchanged FIXED OILS AND FATS. 3 for a lengthened period, but, on exposure to air, many of them thicken with absorption of oxygen, and are ultimately converted (if exposed in sufficiently thin layers) into a yellowish, transparent membrane or varnish. 1 Such oils (e.g., linseed, walnut, hempseed, and poppy-seed oils) are called drying oils. 12. The no n- drying oils behave in a different manner on exposure to air. When absolutely free from foreign matter most of them remain unchanged, but commercial specimens gradually turn rancid, that is, they gradually lose their colour (and to a certain extent their fluidity), and acquire an acrid, disagreeable taste, and acid reaction to litmus paper. This alteration is due to the presence of certain foreign matters, such as the cellular sub- stance of the animal or plant from which the oil was extracted. These bodies act as ferments, and set free fatty acids, besides pro- ducing small quantities of certain volatile acids (e.g., butyric, valeric, caproic) of strong odour. By agitating such rancid oil with hot water, and subsequently treating it with a cold and dilute solution of sodium carbonate, the products of decomposition may often be removed and the fat restored to its original state. Such of the foregoing characters as are of importance as means of identifying, detecting, or assaying fixed oils are discussed at length in the following sections. The physical characters are described first, and then the reactions based on the chemical pro- perties of the oils. These sections are succeeded by a tabular classification of the oils, based on their physical and chemical characters. Then follow methods of examining fatty oils and waxes for foreign matters, and of identifying them. After that will be found sections describing special methods of assaying the principal commercial fixed oils and for examining lubricating oils. Lastly, in the Appendix to the Division, will be found a description of the products of the saponification of fixed oils, such as the fatty acids, soaps, glycerin, &c. EXTRACTION AND PURIFICATION OF FIXED OILS AND FATS. For the extraction of oils and fats from animal tissues it is often sufficient to allow the substance (e.g., cod-liver) to become somewhat putrid, when a quantity of oil drains from it, or is obtain- able by slight pressure. A further quantity can be extracted by 1 Under certain conditions, as when cotton- waste, shoddy, or hemp is moist- ened with oil and exposed to the air, the oxidation of the oil becomes so energetic as to lead to considerable elevation of temperature, and even actual inflammation. 4 EXTRACTION OF OILS AND FATS. warming or boiling the tissue with water, as is done with blubber. In the case of lard and tallow it is merely necessary to heat the substance alone, and strain the melted fat away from the mem- branous matter. In the case of a compact tissue like bone, the whole of the fat cannot be extracted by any means short of treat- ment with a solvent, such as carbon disulphide or petroleum spirit. The extraction of the fat or oil from vegetable tissues may be effected by boiling the crushed substance with water, or by subjecting it to powerful pressure, either at the ordinary temper- ature or between plates heated to a little beyond the fusing point of the fat. The product obtained in the last manner will usually contain more "stearin" or solid fat than the "cold-drawn" oil. In either case a certain quantity of the fat is mechanically retained by the tissues, and hence a larger yield can be obtained by the use of carbon disulphide or petroleum spirit, which on being dis- tilled off leaves the fat behind. The proportion of oil or fat yielded by any particular seed or other source depends on the nature and maturity of the seed and on the process employed for the extraction of the oily matter. According to Vohl, the average percentage of oil extracted by solv- ents from linseed is 27 ; from hempseed, 26 ; from poppy-seed, 49 ; from walnuts, 50 ; and from almonds, 52 per cent. Accord- ing to Voelcker, the proportion of oil in linseed varies from 31 to 38 per cent., the linseed cake containing from a little under 10 up to nearly 1 6 per cent. ; while the oil in cottonseed cake varies from 6 per cent, in the undecorticated to 1 6 per cent, in the decorticated. Cacao-nibs contain on the average about 50 per cent, of fat. Determination of Oils and Pats. In the laboratory, the determination of the oil in solid animal and vegetable matters is effected by treating the finely-divided and previously dried substance 1 with a suitable solvent under such conditions as to ensure complete extraction. Carbon disulphide or petroleum spirit may be employed for the purpose, but in the author's experience ether is more satisfactory for general use. It is not so unhealthy as carbon disulphide, and inflammation, due to breakage of the apparatus or other cause, is not so dangerous as when an accident occurs during the use of petroleum spirit. The exhaustion of seeds, bones, shoddy, oil-cakes, milk-residues, &c., may be effected by simply digesting the substance with the solvent at the ordinary temperature, with frequent agitation, in a 1 In the case of linseed and other substances containing drying oils, the desiccation must either be omitted or conducted in an atmosphere of hydrogen or coal-gas. SOXHLET'S EXHAUSTER. \ closed flask. After some hours, the flask should be opened, placed in hot water, and the solvent thus raised to its boiling point. The liquid is then filtered into a weighed flask, and the residue washed with the solvent. The solution is subsequently evaporated or dis- tilled by a steam-heat, and the residual oil weighed. The foregoing method is unsatisfactory, as it requires a consider- able quantity of the solvent, of which a notable proportion is likely to be lost. Hence an apparatus which will act automatically, and allow of complete exhaustion of the substance by a limited quantity of the solvent, possesses great advantages. For this purpose, no better arrangement has been devised than an ingenious arrangement due to Soxhlet (fig. 1). The substance to be exhausted of oil is enclosed in a plaited filter or cylinder of filter paper ; or if it be coarse, it is sufficient to place it loose in a large test-tube (A), having an aperture at the bottom closed by a plug of glass-wool. Thus arranged, the tube or filter with its contents is placed in a Soxhlet- tube, having a little glass-wool at the bottom, and adapted by means of a cork to a flask (B) contain- ing the solvent. A vertical condenser (C) is adapted to the upper end of the Soxhlet's tube, and the solvent kept boiling by a suitable source of heat. In the case of petroleum spirit, ether, or other volatile and inflammable solvent, this should be a tin vessel of water (D) kept hot by a small flame. As the solvent boils it is condensed and falls on the substance to be extracted, remaining in contact with it until both the inner and outer tubes are filled to the level of the siphon (E), when the solution passes off into the flask, to be redistilled and re- condensed, and so on until the process is judged to be complete. With a proper arrangement of the source of heat, the ex- traction goes on regularly and automatically. On changing the flask and replacing the inner tube by one containing a fresh sample, the apparatus is ready to be used for another extraction. Fig. 1. A very simple and convenient form of exhauster, adapted either for extraction or repercolation, has been described by Dunstan and 6 DETERMINATION OF OILS AND FATS. Short (Pharm. Jour., [3] xiii. 664). It consists of two glass tubes, the wider of which is drawn oat at one end. The narrower and somewhat shorter tube fits into the outer one with much margin, and is also drawn out in such a way as to allow the end to pro- trude from the drawn-out end of the wider tube when the smaller is inserted therein. At the point where the outer tube commences to contract it is indented on opposite sides, by which means two ledges are formed within the tube, which serve as supports for the narrower tube. 1 The inner tube serves to contain the substance to be exhausted. The lower drawn-out end of the wider tube is fitted by a cork to the flask containing the volatile solvent, while the upper end is connected with a condensing arrangement. J. West-Knights has described (Analyst, viii. 65) a form of exhauster which may be conveniently used when the quantity of material to be extracted is somewhat small (fig. 2). A percolator is made by cutting off the bottom from a test-tube of suitable size, and blowing a hole or two (AA) in the side of the tube about an inch from the top. A disc of filter paper or fine cambric (B) is tied over the lower end of the tube. The substance to be extracted is placed in the tube, and kept in its place by some glass-wool or a perforated disc of metal, and the tube with its contents then fixed by a cork to the lower end of the tube of a vertical condenser (C). This is adapted by a larger cork (D) to the neck of an ordinary flask containing the volatile solvent, on heating which the vapour passes through the holes in the side of the test-tube up into the tube of the condenser, where it is liquefied. The condensed liquid drops back into the test-tube, percolates through the substance to be extracted, and falls to the bottom of the flask, to be again vola- tilised. As the percolator is inside the flask, its contents are kept constantly at the boiling point of the solvent, and, the action being continuous and automatic, very rapid exhaustion may be effected. Other forms of exhauster have been contrived by Church, Drechsel, Angell, Thorns, Thresh (Pharm. Jour., [3] xv. 281), and 1 The indentations are made by pressing each side of the tube when red-hot with a pair of crucible-tongs. Fig. 2. DETERMINATION OF FAT IN MILK. 7 others, but those already described will be found sufficient for all purposes. To recover the oil from its solution in the ether, or other liquid employed, the solvent should be distilled off at a steam-heat, and the last traces of it removed by placing the flask on its side and heating it in the water-oven until constant in weight. In some cases the complete removal of the solvent is best effected by blowing a gentle stream of air, previously filtered through cotton- wool, through the flask while it is maintained at a temperature of 100C. In the case of liquids containing oil in the form of emulsion, a separation can often be effected by agitation with ether. The extraction of the fat from milk can be effected in this manner if the liquid be previously made slightly alkaline, but it is better to evaporate the milk to dryness at 100, and exhaust the residue with ether or petroleum spirit. 1 Purification of Oils. The refining or purification of fixed oils is effected in various ways, according to their origin and the impurities it is desired 1 The determination of the fat in milk has considerable practical interest. Various methods of effecting it have recently been investigated by a Committee of the Society of Public Analysts (Analyst, x. 217, xi. 1), who recommended a process devised by M. A. Adams, which, with some modifications by the writer, is as follows : A strip 22 inches long and 2| inches wide is cut from a sheet of white demy blotting paper. This is then rolled up, together with a piece of thin string, which serves to prevent contact between the concentric folds of the coil. The string is conveniently passed through holes in the paper, having been previously boiled with water containing some sodium car- bonate, to remove size and resinous matters. A cap of filter paper is then placed on one end of the coil, and secured by the ends of the string. Thus arranged, the paper forms a coil 2 inches high by about 1 inch in diameter, and before being used should be deprived of traces of fat, resin, &c., by exhaustion with ether in a Soxhlet-tube, the ether being subsequently driven off. The coil is then suspended by some simple means, the capped end being downwards, and 5 c.c. of the milk to be tested, and the density of which is known, is run on to the upper part from a pipette. The milk is rapidly absorbed by the paper, and none filters through the paper cap. The coil is then dried in a water-oven for an hour or two, and then placed in a Soxhlet-tube, in which it is exhausted with ether, at least twelve syphonings being necessary. The ether is then distilled off in the usual way, and the residue of fat dried till constant in weight. The method is applicable to sour milk if a known weight be taken instead of a definite measure, and a few drops of ammofeia be added before pouring the milk on the coil. Milk of fair quality should yield by this pro- cess at least 3 per cent, of fat, the average proportion obtained from genuine whole milk approaching 4 per cent. This proportion exceeds that yielded when other processes of extraction are employed. 8 PUEIFICATION- OF OILS. to remove. The following is an outline of the methods of most general application. They may be modified in detail, or combined in a manner suited to any special case. ACTION OF LIGHT. Simple exposure of a fixed oil to light for a period varying from a few days to as many months will often effect a remarkable improvement. Linseed and seal oils afford good examples of the success of this treatment. ACTION OF HEAT. By rapidly heating palm oil to about 240 C. ( = 464 F.), and maintaining it at that temperature for ten minutes, it is very effectually bleached, and the same is the case if poppy oil be kept at 90 to 95 C. for four or five hours. The same treatment can be advantageously employed in other cases. FILTRATION. Some oils are greatly improved by treatment with animal or wood charcoal. Kaolin, steatite, plaster of paris, and other substances may often be employed with advan- tages to effect a semi-mechanical clarification. After such treat- ment the oil usually requires filtration through canvas bags, which also serves to separate spermaceti, stearin, &c., deposited by cooling the oil. WASHING WITH WATER. A very general method of purification consists in agitating the oil with water. This is often conveniently effected by driving in steam through a false bottom or perforated pipe. This treatment can be combined or alternated with any of the others, and if desired, chemical reagents can be added to the water. TREATMENT WITH ACIDS. A method of very general applica- bility, and one which, when carefully conducted, is remarkably efficacious, consists in violently agitating the oil, previously heated to about 40 C., if necessary, with from 1 to 2 per cent, of concen- trated sulphuric acid, which attacks and chars the impurities without materially affecting the oil. The acid is then allowed to settle, and the supernatant oil well washed with water ; or steam is blown into the mixture for a short time, and the acid water allowed to separate from the oil. For 100 gallons of oil, about 10 Ibs. of sulphuric acid are usually required, diluted with an equal bulk of water. In some cases hydrochloric acid is substituted for sulphuric. Treatment with acid is very suitable as a means of refining most seed oils (e.g., rape and linseed oils), and greatly improves some of the fish oils, but the refined product is apt to contain traces of unremoved mineral acid, and an undesirable proportion of free fatty acids. These impurities are of no disadvantage if the oil is to be employed for soap-making, but acquire importance if it is to be used for burning or lubrication. Treatment with sulphuric or PURIFICATION OF OILS. 9 hydrochloric acid also serves to remove the lime which is present in bone-fat. TREATMENT WITH ALKALIES. Cottonseed oil, olive oil, sperm oil, and some others, are advantageously purified by treatment with a solution of caustic soda, the quantity of which must be regulated according to the proportion of free fatty acids and impurities present in the oil. Cottonseed oil contains a notable proportion of a resinous matter which produces a fine blue colour with the alkali. The oil loses considerably in refining, and the proportion of alkali used should be regulated according to the indications of a preliminary laboratory trial. A specific gravity of 1*10 is a suitable strength for the ley. Cottonseed oil expressed in England from decorticated seed often contains so large a propor- tion of free acid that purification with alkali becomes practically impossible. 1 Ammonia, sodium carbonate, magnesium car- bonate, or milk of lime may sometimes be used with advantage to remove acids from oils. The use of alkali instead of acid for purification is to be preferred in the case of oils intended for use as lubricants or for cooking. The refined cottonseed oil now ex- tensively used for cooking, &c., is remarkably free from acid. TREATMENT WITH OXIDISING AGENTS. A remarkably effective means of clarifying certain fish oils consists in heating the liquid by means of steam to a temperature approaching the boiling point of water, and then blowing a current of air of a similar temperature through the liquid. The treatment must be cautiously conducted, or the rise of temperature may be so great as to cause a notable change in the density and viscosity of the oil, such as occurs purposely in the manufacture of "oxidised" or "blown oil" (p. 52). Another very efficient oxidising agent, especially suitable for the treatment of palm oil, is chromic acid, as produced by the reaction of potassium bichromate with a suitable amount of sul- phuric or hydrochloric acid. The oil is melted, strained if necessary, and then agitated at about 50 C. with about 1 per cent, of potas- sium bichromate previously dissolved in water. To this is added sufficient acid to react with the salt to form potassium and chromic chlorides or sulphates, a slight excess of acid being rather advantageous than otherwise. Some oils, when treated in this manner, retain chromium compounds with remarkable persistency. 1 The writer found a sample of oil from decorticated cottonseed, expressed in Liverpool to require 14 -1 per cent, of KHO to neutralise the free acid. This corresponded to 70*5 per cent, of free acid calculated as oleic. 10 PHYSICAL PROPERTIES OF FIXED OILS. TREATMENT WITH REDUCING AGENTS. In the case of linseed and other drying oils, exposure to light in contact with a de- oxidising agent affords a very efficient means of clarification. Strips of metallic lead may be employed, or finely-divided precipitated lead, as recommended by Livache. A strong solution of ferrous sulphate also answers the purpose, especially if assisted by exposure of the oil to light for some weeks, and accompanied with frequent agitation. TREATMENT WITH PRECIPITANTS. Fish oils and some others are greatly improved by violently agitating them with a hot solution of oak-bark or other tannin-matter. Steam and air can be blown in at the same time. After deposition, the clear oil should be treated with a solution of acetate of lead or aluminium, to remove any excess of tannin, and is afterwards dried by treat- ment with plaster of paris. Other metallic solutions or reagents forming insoluble compounds with gelatin or albumin, may be employed with advantage in certain cases. PURIFICATION BY PRESSURE. This sketch of the principal methods of refining oils would not be complete without a refer- ence to the widely applied use of hydraulic pressure for separating the solid from the liquid constituents of oils. The solid fats thus separated are commercially known as "stearin," though they are frequently far from approximating to the pure glyceride of stearic acid. Similarly, the liquid expressed oils are conveniently termed "oleins," though of very complex composition. The follow- ing are some of the chief instances in which commercial fats and oils are separated by pressure into solid and liquid portions : Original Oil. Olive oil. Cottonseed oil. Cocoanut oil. Tallow. Lard. Whale oil. Sperm oil. Liquid Product. Purified olive oil. Purified cotton oil. Cocoanut olein. Tallow oil. Lard oil. Purified whale oil. Purified sperm oil. Solid Product. Olive oil stearin. Cotton oil stearin. Cocoanut stearin. Tallow stearin. Lard stearin. Whale stearin. Spermaceti. PHYSICAL PROPERTIES OF FIXED OILS AND FATS. The general characters of the fixed oils have already been described. Some of their physical properties are of importance for their recognition and determination, this being especially true of their density, melting and solidifying points, absorption-spectra, COHESION-FIGURES OF OILS. 11 viscosity, and behaviour with solvents. These characters, and the methods of observing them, are described in detail in the following sections. The determination of the refractive indices and electrical con- ductivities have been proposed as methods of differentiating oils, but the figures thus obtained do not appear to possess any practical value. Cohesion-Figures of Oils. The surface-tension of oils is a character which in certain cases is capable of useful application, though its value has been much exaggerated. To obtain the cohesion-figures which depend on the surface-tension, it is necessary to allow a drop of the oil to fall gently on the surface of still water contained in a flat evaporating basin or soup-plate. In order to ensure success, and to obtain bold, well-defined figures, it is necessary that the vessel con- taining the water should be chemically clean ; that the surface of the water should also be clean and free from organic matter ; that the temperature should not be below 15 C. ; and that the sur- face of the water should not be too limited. The time required to produce the characteristic figures should be carefully noted. When a drop of olive oil is placed on the water, it slowly spreads out into the shape of a large disk with slightly recurved edges. The cohesion of the oil, however, soon causes the disk to contract, the edges first testifying the return of the cohesive force ; a number of little spaces begin to appear round the edges, causing them to resemble a chaplet of beads. The spaces between the beads soon open out, and the edges become toothed, the detached portions in some parts reuniting themselves to the main sheet of oil, enclosing polygonal spaces bounded by fine beads and covered with an excessively fine dew of oil, which it requires a sharp eye to detect. This succession of changes occurs in about thirty-five seconds. Oil of sesame, treated in the same manner, begins by forming a well-defined sheet. Contraction soon takes place, the final figure being a central spot with distinctly marked rays, between which other smaller rayed spots appear, the whole recalling the aspect of a spider's web loaded with dew. The phenomenon is complete in about sixty seconds. Mixtures of olive with sesame* oil give figures approaching more or less to the typical, according as one or the other is in excess. Other oils also give more or less characteristic cohesion-figures. Absorption-Spectra of Oils. The absorption-spectra of the fixed oils occasionally afford valuable 12 ABSORPTION-SPECTRA OF OILS. indications of their purity. For observing them a micro-spectroscope may be used, but in many cases the light must be caused to pass through several inches of the oil to be examined. Although many vegetable oils give exceedingly striking absorption-bands, the posi- tion of these is not capable of employment for their discrimina- tion in many cases, as the absorption is not a property of the oils themselves, but of the chlorophyll and impurities contained in them. Hence the purification or clarification of an oil tends seriously to reduce the characteristic nature of the absorption- bands, which, indeed, may disappear altogether if the oil be long exposed to sunlight. In one particular, however, the absorption- spectrum furnishes important information. Thus, no oils of animal origin give definite absorption-bands, the spectrum being merely obscured at the more refrangible end, whilst in many vegetable oils the absorption-bands of chlorophyll are exceedingly well marked, especially a band having about the same refrangibility as the Fraunhofer line B. By applying this fact it is easy to detect the presence of rape }> olive, or linseed oil in sperm, cod, or lard oil. Castor and almond oil, on the other hand, give no well-defined bands, and the band at B in the case of sesame oil is but very faint, though there is strongly marked absorption of the whole of the red nearly up to that point. 1 Viscosity of Oils. A useful physical test for oils is based on their relative " body " or viscosity, a property which may be regarded as the converse of fluidity. The viscosity is usually compared with 1 The absorption-spectra of fixed oils of vegetable origin have been recently investigated by Doumer and Thibaut (Corps Gras Industriels), who classify them in the following manner : a. Oils exhibiting no selective absorption of the spectrum ; sweet almonds, bitter almonds, castor. b. Oils which absorb all rays of greater refrangibility than the green, but the spectra of which show no absorption lines ; colza, rape, mustard, and linseed. c. Oils showing the absorption-spectrum of chlorophyll ; olive, arachis, nut. d. Oils, the (photographic) spectrum of which shows three broad bands in the more refrangible part, which bands are exactly in the position of the corre- sponding absorption-bands of chlorophyll ; but the less refrangible bands characteristic of chlorophyll are wanting ; sesame, arachis, poppy, rape. These observations were made on the freshly expressed oils. They are not entirely in agreement with the statements made in the text, and it is evident that their practical value is seriously reduced by the change likely to be pro- duced in the spectra by keeping, and by the different processes of refining which may have been employed. SPECIFIC GRAVITY OF OILS. 13 that of rape oil, but it may also be referred to water or glycerin as a standard. The viscosity of an oil is determined by ascertaining the time a certain weight or measure takes to flow through a given aperture, but the results obtained vary not inconsiderably with the con- struction of the apparatus employed. The subject is fully discussed in the section on the " Examination of Lubricating Oils." Specific Gravity of Fixed Oils. The density of the fixed oils and fats is a property largely dependent en their constitution, and hence is more or less characteristic of each particular oil. As a rule, the specific gravity of different samples of the same kind of oil varies within very narrow limits, but it is liable to be affected by the treatment to which the oil may have been subjected in the process of refining, the presence of free fatty acids, the age of the oil and the amount of oxidation it has undergone, and by other circumstances. The specific gravity of fixed oils may be ascertained by the usual methods, but great care is necessary. Owing to the high coefficient of expansion of oils (page 19) the temperature at which the obser- vation is made should be carefully noted, and in accurate deter- minations the thermometer employed should be an instrument the indications of which have been verified. When a sufficient quantity of the sample is available, and results of extreme accuracy are not required, the determination of the density can be made very readily and satisfactorily by means of an accurate and delicate hydrometer. In any observations, save those of the roughest kind, the oil should be brought accurately to the standard temperature by immersing the hydrometer-glass in water, cooled, if necessary, to 15'5 C. ( = 60 F.) by dissolving in it some sodium thiosulphate (hyposulphite) or oxalic acid. The hydro- meter should be immersed in the oil for five or ten minutes, and the temperature again observed before taking a reading of the density, as the use of a warm hydrometer may cause an increase of several degrees in the temperature of the oil. Of course, in taking the density by a hydrometer, the accuracy of the instrument employed is presupposed, but many of the instruments sold are inaccurate to the extent of several degrees. Another very satisfactory method of determining the density of fixed oils is by means of Westphal's hydrostatic balance. A counterpoised thermometer suspended from a piece of platinum wire is attached to one end of a graduated lever. On immersing the thermometer in a liquid it loses a certain weight. The equili- 14 WESTPHAL'S HYDROSTATIC BALANCE. brium is restored by hanging on the lever a series of riders which are adjusted in weight so as to make the reading very simple. Fig. 3 shows the instrument in its usual form. The plum- met displaces exactly 5 c.c. of liquid, and hence the weight re- quired to restore equi- librium is that of 5 c.c. of the fluid of which the density is required. Differences of 0'2 de- gree are appreciable, so that the indications are equal in delicacy to those of the specific gravity Fig. 3. bottle, and considerably more accurate than the readings of a hydrometer. As the em- ployment of a thermometer as a plummet renders the instrument unsuited for determinations of densities at 100 C. or other high temperatures, the writer substitutes, in practice, a plummet of thick glass rod, having a displacement of exactly 5 c.c. 1 1 It is evident that a special balance and rider for taking densities by a plummet are by no means essential. If a plummet of known displacement be suspended from one arm of a balance and duly counterpoised, on immersing it in a liquid it will lose a portion of its weight equal to the weight of an equal volume of the liquid employed, and this loss being ascertained by adding weights sufficient to restore equilibrium, the specific gravity of the liquid will be found by dividing the weight in grammes employed by the volume of the plummet in cubic centimetres. If a plummet of 10 c.c. displacement be em- oloyed, the density of the liquid will be one-tenth of the weight in grammes required to restore equilibrium. The glass plummet may be brought approximately to the desired bulk by noting its displacement. Its specific gravity is then carefully determined by weighing'it in distilled water, when the exact weight of 5 or 10 c.c. is readily calculated, and it is brought to this weight by careful grinding or filing. Mr E. Casella, of 147 Holborn, E.G., supplies accurately adjusted glass plummets and counterpoises for employment with an ordinary balance. The use of a plummet of exactly 5 or 10 c.c. displacement facilitates calcula- tion, but in its absence a plummet of any known measure could be employed, and this measure can be ascertained by dividing its weight in grammes by its specific gravity. The weight lost by the plummet on immersing it in any liquid, divided by the measure of the plummet, gives the specific gravity of the liquid. The experience of the writer convinces him that the Archimedean or plummet method of taking the specific gravities of liquids deserves a wider application than it has hitherto received. DETERMINATION OF DENSITIES OF OILS. 15 The specific gravity bottle and Sprengel-tube (vol. i. page 5) may also be employed for ascertaining the densities of oils, and allow of more ac- curate determinations than can possibly be made with a hydrometer. The weight of distilled water which fills the bottle or tube at a temperature of 15*5 C. ( = GOT.) is usually (at least in England) taken as the unit of comparison in stat- ing the density of fixed oils. 1 As many of the fixed oils are solid or semi-solid at the ordinary temperature, their densities are not directly compar- able with those of the fluid oils. This difficulty may be obviated by observing the specific gravity in a molten state at some higher temperature. This is done by J. Bell and J. Muter at 100 F. ( = 37'8 C.), 2 but C. Estcourt (Chem. Netos, xxxiv. 254) has recommended Fig. 4. that the determination be made at the boiling point of water, which, for many reasons, is a preferable temperature. The density at this temperature may be observed by the hydrometer or hydrostatic balance, if the glass cylinder containing the oil be kept for a suffi- cient time in a bath of boiling water before a reading be taken. With a specific gravity bottle the manipulation is somewhat less easy, but with a Sprengel-tube the densities of oils at the boiling point can also be determined with great accuracy. The weight of 1 Oil merchants frequently use a hydrometer with a scale on which water marks and rape oil 28. 2 Dr Muter (Span's Encyclopaedia of the Industrial Arts, p. 1469 et seq.) gives the following figures as representing the "actual densities " at 100 F. of various oils as commonly met with, water at the same temperature being taken as 1000 : Olive oil, Almond oil, . Arachis oil, . Eape oil, Nut oil, Cottonseed oil (brown) . Cottonseed oil (refined), Poppy-seed oil, Hempseed oil, Linseed oil (raw) . These figures in most cases differ by 9 to 11 degrees from those expressing the densities of the same oils at 60 F. ( = 15 '5 C.). 907-0 Linseed oil (boiled), 938-0 905-6 Castor oil, . 955-8 908-5 Sperm oil, 872-4 9067 Whale oil, . 906-0 908-4 Seal oil, 915-0 917-6 Codliver oil, 917-9 913-6 Lard oil, 907-8 915-4 Neatsfoot oil, 907-0 919-3 Butterine, . 903' to 906-0 925-2 Butter-fat, . * 912' to 914-0 16 DETERMINATION OF DENSITY BY THE PLUMMET. the Sprengel-tube and that of water contained in it at 15*5 C. being known, the tube should be completely filled with the oil, by immersing one of the orifices in the liquid and gently sucking the air from the other orifice of the tube. The tube is then placed in the mouth of a conical flask (D, fig. 4), containing water kept in rapid ebullition, and the cover of a porcelain crucible (E) placed over it. As the oil gets hot it expands, and is expelled in drops from the horizontal capillary orifice (C) of the tube. When the expansion ceases, any oil adhering to the orifice is removed by cautious applica- tion of filter paper, the tube removed from the bath, wiped dry, allowed to cool, and weighed. The weight of the contents, divided by the weight of water at 15'5 C. previously known to be con- tained by the tube, will give the density of the oil at the tempera- ture of the boiling water, water at 15' 5 C. being taken as unity. 1 When the amount of oil or fat at disposal is sufficient, the Sprengel-tube may be advantageously replaced by the Westphal- balance, 2 the use of which leaves nothing to be desired on the score of rapidity, accuracy, or ease of manipulation. In taking densities by the plummet at the boiling point of water, it is desirable to employ a cylindrical bath of ^icual (fig. 5), the top of which is per- forated by two orifices. One of these is fitted with an upright tube, which serves to convey the steam away from the neighbour- hood of the balance, while into the other a test-tube, 6 inches in length and 1 inch in diameter, fits tightly, the joint being made perfect by a ring of cork or india-rubber. The test-tube is filled with the oil, the density of which is to be ascertained, and the plummet immersed in it. The water in the outer vessel is then kept in constant ebullition, 1 For several reasons the figure thus obtained is to be preferred, though, if desired, the weight of water at the boiling point, contained by the tube, may be ascertained, which determination affords the means of calculating the density of an oil at the boiling point of water, compared with water at the same tem- perature. There is no necesssity to make any correction for the expansion of the glass, as all the determinations are comparative. 3 The application of the Westphal-balance to the determination of the DENSITIES OF OILS. 17 until a thermometer, with which the oil is repeatedly stirred, indicates a constant temperature, when the plummet is attached to the lever of the balance, and counterpoised in the usual way. The following table gives the densities, as determined in the author's laboratory, of a number of samples of oil at the tempera- ture of boiling water. Some of the observations were made with the Sprengel-tube and others by the plummet ; but in certain cases, where both methods were employed, the results showed such a close concordance that it is a matter of indifference, so far as the figures are concerned, which method is employed. In most cases the density of the same sample was taken at the ordinary tempera- ture in addition, some of these latter observations being made by a hydrometer : Natui e of Oil. Specific Gravity of Oil ; Water at 15 5 C. (= 60 F.) being 1000. At 15-5 C. (=60 F.). At 98* to 99 C.i ( =208 to 210 F.). Arachis oil, ..... Rape oil, ...... Neatsfoot oil, ..... ^ Cottonseed oil, .... ^Sesame oil, ..... Cocoanut olein, .... 922" 915- 914" 925' 921- 926-2 867-3 863-2 861-9 872-5 867-9 871-0 Nigerseed oil, ..... Linseed oil, ..... 927' 935- 873-8 880-9 Castor oil, ..... Whale oil, 965-5 9307 926- 924- 927-5 932- 909-6 872-5 871-4 873-3 874-2 877-4 Porpoise oil, ..... Seal oil, ...... Codliver oil, Menhaden oil, ..... Sperm oil, DcBgling (Bottlenose) oil, 883-7 880-8 830-3 827-4 density of butter and other fats at the boiling point of water was originally recommended by Chas. Estconrt (Chem. News, xxxiv. 254), and the apparatus shown in'fig. 5 is a modification of that devised by him and illustrated in a paper on the method published by J. Carter Bell (Chem. News, xxxviii. 267). 1 It will be observed that the densities in the third column of the foregoing table are recorded as obtained at a temperature of 98 to 99 C. In the author's laboratory water ordinarily boils at 99 C., and oil immersed in a vessel of boiling water rarely reaches a temperature exceeding 98 '5 C. VOL. II. B 18 DENSITIES OF MOLTEN FATS. The next table shows the specific gravity at two different tem- peratures of various molten fats and other bodies which are solid at the ordinary temperature. The densities were ascertained by the plummet method, and in each case the observations at the two different temperatures were made on the same sample of the sub- stance. A column is added showing the difference in density corresponding to a change of 1 C. Nature of Fat, &c. Specific Gravities of Melted Fats, Several degrees. Spermaceti, . 43'5 to 44-3 43 -4 to 44 -2 Yellow beeswax, 63-4 61 '5 to 62 '6 White beeswax, 61-8 61-6 Stearic acid, . 56-0 to 56'6 557 to 55-8 A rise of temperature during solidification was observed in the case of artificial mixtures, as well as in that of the natural glycerides. It was exhibited by mixtures of spermaceti with stearic acid, and of paraffin with stearic acid, being probably due to the constantly varying composition of the liquid remaining after partial solidification. The usual melting and solidifying points of various oils, fats, waxes, '&c., are given in the tables commencing on page 63. FIXED OILS AND SOLVENTS. 25 Relations of Fixed Oils to Solvents, The fixed oils are, without exception, wholly insoluble in water and aqueous liquids generally. In cold alcohol the fixed oils are but little soluble, as a rule, and the solid fats and waxes still less so. In boiling alcohol, however, some of the fluid oils dissolve to a considerable extent, especially if the solvent be anhydrous. Quantitative statements respecting the solubility of oils in alcohol are, however, generally unreliable, the solubility recorded being, in many cases, merely a rough indication of the proportion of free fatty acid which happened to be present in the sample examined. The following statements cover all the general principles and reliable facts respecting the solubility of the fixed oils in alcohol : 1. Those oils containing the glycerides of lower fatty acids (e.g., porpoise oil, cocoanut oil, butter fat) exhibit exceptional solubility in alcohol. 2. Those oils containing the glyceride of linoleic acid (e.g., linseed and other drying oils) are comparatively readily soluble in alcohol. 3. Castor and croton oils dissolve with facility in alcohol, and are sharply distinguished by this character from the majority of oils. In ether, chloroform, carbon disulphide, benzene, and oil of tur- pentine the fixed oils dissolve with great facility, being in many cases miscible with those solvents in all proportions. Petroleum spirit acts, in the majority of cases, like the solvents just mentioned ; but castor oil constitutes a remarkable excep- tion to the general rule, being practically insoluble in petroleum spirit and other petroleum products (see " Castor Oil "). The behaviour of various fixed oils with glacial acetic acid has been recently investigated by E. Valenta (Dingl. polyt. J., cclii. 296 ; Jour. Chem. Soc., xlvi. 1078). Equal "parts" of the oil and of glacial acetic acid of 105 6 '2 specific gravity are mixed, 1 and gra- dually heated with continuous shaking, until complete solution takes place or the acid begins to boil. A thermometer is then immersed in the liquid, the tube allowed to cool slowly, and the temperature recorded at which the liquid becomes turbid. The writer has tried this test on a number of oils. He finds a slight variation in the strength or proportion of the acid employed is not of importance ; and the temperature at which turbidity occurs with 1 3 c.c. of the sample of oil, previously melted if necessary at a gentle heat, and an equal measure of glacial acetic acid are convenient quantities to employ. 26 FIXED OILS AND SOLVENTS. any particular specimen is readily observed and fairly constant. Unfortunately the writer's experience is not in accord with that of Valenta as to the turbidity-temperatures of particular oils, a fact that renders it probable that a more extended experience will prove that different specimens of the same description of oil give results showing considerable variations. The discordant figures obtained by Valenta and the writer for palm oil are probably due to the different proportions of free acid in the samples ; and the same explanation probably applies to Valenta's figures for green and yellow olive oil. The following table shows the results both of Yalenta and the author : Tempera- Tempera- Kind of Oil. ture of Turbidity Observer. Kind of Oil. ture of Turbidity Observer. Green olive oil, 85 Valenta. Palm oil, 23 Valenta. Yellow 111 Laurel oil, 26-27 Almond oil, 110 Nutmeg butter, 27 Aracliis oil, 112 Cocoanut oil, . 40 > 87 Allen. Palmnut oil, . 48 Apricot-kernel oil, . 114 Valenta. Bassia oil, 64-5 Neatsfoot oil, . 102 Allen. Butter fat, . 61-5 Allen. Sesame" oil, 87 }j Porpoise oil, . 40 i 107 Vaienta. Melonseed oil, . 108 Palm oil, 83 Cottonseed oil, 110 M Butterine, 98 " Lard, . 96-5 Nigerseed oil, . 49 Allen. Beef tallow, . 95 Vaienta. Linseed oil, 57 Pressed tallow, 114 Cacao butter, 105 Menhaden oil, . 64 Codliver oil, . Shark-liver oil, Sperm oil, 101 79 105 98 Valenta. Allen. Olive-kernel oil, ) Castor oil, . V Colophony, . I Completely soluble at the ordinary tempera- ture. Allen. Bottlenose oil, 102 >t Stearic acid (com-) 36 Not com- mercial), . f M pletely dis- solved at the boiling point of Valenta. Oleic acid (com-) mercial), . j 27 acetic acid. From an inspection of the above table it would appear that olein is only with difficulty soluble in glacial acetic acid, and that the same is true of stearin. The discrepancy between the figure of Valenta and that of the author for the turbidity-tempera- ture of palm oil makes the solubility of palmitin uncertain ; but it is evident that the glycerides of fatty acids lower than palmitic (as contained in porpoise oil, butter fat, cocoa- nut oil, laurel oil, nutmeg butter, &c.) dissolve with comparative facility. The author obtained remarkably constant results from several samples of butter, and it appears probable that further experience may prove the method to afford a simple means of CONSTITUTION OF FATTY OILS AND WAXES. 27 distinguishing butter from butterine. The incomplete solubility of rape oil and other oils from the cruciferce, even at the boiling point of acetic acid, is noteworthy, as are the low figures found for linseed oil, nigerseed oil, and menhaden oil, as compared with those for the non-drying oils. Valenta has also proposed to employ glacial acetic acid at 50 C. for distinguishing mineral oils from rosin oil, the former being sparingly and the latter readily soluble in that reagent. CONSTITUTION AND CHEMICAL PROPERTIES OF FATTY OILS AND WAXES. In chemical constitution, all fixed oils and waxes of animal and vegetable origin consist of ethers of the higher fatty acids. (See tables on page 31.) The alcohol-radical with which the fatty-acid- radical is associated to form the natural fixed oils is the triad radical glycyl, C 3 H 5 . Thus the fixed oils are glycyl ethers, or glycerides, and have a constitution expressed by the formula: In this formula F represents the radical of one of the fatty acids, and may have the general formula, C n H 2n _ 1 0, as the radical of stearic acid, CjgH^O.OH ; C n H 2n _30, as the radical of oleic acid; C n H 2n _50, as the radical of linoleic acid; or C n H 2n _ 3 2 , as the radical ofricinoleic acid. Thus, glycyl tristearate, which has the composition is also called tri-stearin, or simply stearin, and is the chief constituent of mutton-fat. Similarly, triolein is the principal component of almond, olive, and lard oils, and t r i p a 1- m i t i n of palm oil : while the glycerides or glycyl ethers of (homo) linoleic and ricinoleic acids respectively constitute the chief parts of linseed and castor -oils. Olein and linolein, being liquid fats, are found most largely in the fluid oils, while stearin and palmitin constitute the major portion of most solid fats. With a few probable exceptions, the natural glycerides appear to contain three atoms of acid-radical, but glycyl monostearate or mono-stearin, glycyl distearate or di-stearin, and similar ethers, can be obtained artificially by heating glycerol under pressure with the requisite proportion of fatty acid. Japan wax appears to be an example of a natural glyceride containing only 28 CONSTITUTION OF FATTY OILS AND WAXES. two atoms of the acid-radical, C 3 H 5 : , (F) 2 OH, and researches now in progress appear to indicate the existence of other natural bodies of a similar kind. Experiments by James Bell render it probable that in butter fat the same molecule of glyceride contains the radicals of several different fatty acids. The constitution of certain of the natural fixed oils is still uncertain, and it is possible that some of them are the ethers of homologues of glycyl, or may have a constitution of a wholly different nature. While the various vegetable and animal fixed oils and fats consist, as a general rule, of glycerides or glycyl ethers, the waxes proper contain the ethers of higher alcohols of the ethylic series. Thus, spermaceti consists chiefly of cetyl palmitate, C 16 H 33 .O.C 16 H 31 0; whilst Chinese wax, beeswax, and carnaiiba wax contain still higher monatomic alcohols, and the last substance apparently a diatomic alcohol in addition. Sperm oil and bottle- nose oil are chiefly composed of bodies having a constitution similar to that of the waxes. In addition to the glycerides or other ethers which constitute the essential portions of the various fatty oils, most natural oils and waxes contain more or less of free fatty acids, and small propor- tions of colouring, odorous, resinous, and other matters, to which the characteristic colours, smells, and tastes of many of the oils are mostly due. Small proportions of cholesterin and other bodies exist in certain oils, and the list of these principles will probably be much extended as accurate examinations of fatty oils become more common than has hitherto been the case. FREE FATTY ACIDS in natural oils are usually products of the spontaneous decomposition of the glycerides, owing to the presence of mucilaginous or albuminous matters. Thus, ordinary butter, which contains putrescible casein, readily turns rancid and then contains free butyric acid; but if all casein and water be removed by melting and filtering the butter, the resultant pure butter-fat may be kept unchanged for a long time. Over-treat- ment w r ith sulphuric acid in the process of refining oils often results in the formation of free fatty acids, and many commercial oils which have been refined by this process are apt to retain traces of free mineral acid. The proportion of free fatty acids in oils is best determined by titration in presence of alcohol with standard alkali and phenol- phthalein in the manner described on page 76. The proportion of free fatty acids present in commercial oils is often very considerable far larger than is commonly sup- posed. Thus, in palm oil the free acid, calculated as palmitic SAPONIFICATION OF OILS. 29 acid, usually varies from 12 to nearly 80 per cent. In eighty-nine samples of olive oil intended for lubricating use, L. Archbutt (Analyst, ix. 171) found from 2'2 to 25*1 of free (oleic) acid, the mean being 8*05 per cent. 1 In the superior grades of olive oil the proportion of free acid is much smaller. In rape oil the per- centage of free acid is generally from 1 '5 to 6 per cent. ; but cottonseed oil, which is refined by means of alkali, is gene- rally free from any trace of free acid. 2 Further information on the proportion of free fatty acids present in commercial oils will be found in the sequel (see also W. H. Deering, Jour. Soc. Cliem. Ind., iii. 540). The presence of free acid in an oil is doubtless the main, if not the only, cause of its tendency to act on metals, and therefore seriously affects the suit- ability of the oil for use as a lubricant. 1 Burstyn found that the extent of the action of olive oil on brass was regularly and directly proportional to the percentage of the acid present. The subject is considered more fully in the section on " Lubricating Oils." Saponification and Proximate Analysis of Fixed Oils. When fatty oils are heated with water under a pressure of 8 to 12 atmospheres, or are distilled with superheated steam, they react with the elements of water, and are decomposed into fatty acids and glycyl alcohol, glycerol, or glycerin, ac- cording to the equation This method of decomposing fats has met with an enormous appli- cation in the industrial production of fatty acids and glycerin. Many natural oils and fats have a tendency to decompose spon- taneously into fatty acids and glycerin, especially in presence of traces of albuminous and other foreign matter. The considerable proportions of free fatty acid often present in commercial palm oil, olive oil, and tallow are due to this cause. A similar reaction occurs when a fatty oil is heated to 110 C., with about 7 or 8 per cent, of concentrated sulphuric acid. On 1 L. Archbutt found that free acid, if present in greater proportion than about 3 per cent., unfitted olive oil for burning in railway lamps, the wick becoming charred. 2 In a sample of porpoise oil which had been brought home in contact with the blubber, and which had drained therefrom at the ordinary tempera- ture, the author found 9'02 per cent, of free oleic acid, and in oil (from the same cargo) extracted by boiling the blubber with water, the free acid amounted to 22 '65 per cent. 30 SAPONIFICATION OF OILS. washing the product with hot water, the sulphuric acid and glycerin are removed, and the fatty acids separate in the form of an oily layer. A parallel reaction takes place when a fatty oil is treated with caustic potash or soda. The change occurs much more readily with some oils than with others, and is greatly promoted by employing heat and using an alcoholic instead of an aqueous solu- tion of the alkali. A potassium or sodium salt, or "soap," of the fatty acid is produced, glycerol being likewise formed : C 3 H 5 /// (OF) 3 + 3NaOH = C 3 H 5 "'(OH) 3 + 3NaOF. By heating fatty oils with milk of lime, or oxide of lead and water, similar reactions occur, and insoluble soaps are formed, together with glycerol. 1 When a 'wax is similarly treated with a base it yields a soap of the fatty acid, together with a higher monatomic alcohol, instead of glycerol. The decomposition is usually effected with difficulty, and alcoholic potash or soda should always be the agent employed. Whenever an ether is split up into an acid and an alcohol, the change is called "saponification, "no matter whether the agent effecting the change be water, an acid, or a base. The term is even extended to the decomposition of ethers which do not yield fatty acids at all. QUANTITATIVE EESULTS OF SAPONIFICATION. It is evident, therefore, that the saponification of fixed oils by alkalies is a perfectly definite chemical reaction, precisely analogous to the decomposition of the salts of the heavy metals by the same reagents. Thus the saponification of stearin by caustic potash is parallel to the precipitation of bismuth hydrate (hydroxide) from a solution of the nitrate. Thus 3K(C 18 H 35 2 ); and Bi'"(N0 3 ) 3 +3K(OH)= Bi'"(OH) 8 Similarly, the saponification of sperm oil resembles the reaction of caustic potash with silver nitrate : (C 12 H 25 )(C 18 H 33 2 ) + (K(OH) = (C 12 H 25 )(OH) + K(C 18 H 33 2 ) ; and AgN0 3 + K(OH) = Ag(OH)* + The following table shows the composition of the leading proxi- 1 The method of saponification now most extensively practised on a large scale consists in treating the fat in a closed vessel with 2 or 3 per cent, of lime, and driving in steam at a pressure of 8 to 10 atmospheres. In some works magnesia or oxide of zinc is substituted for the lime. * At low temperatures AgOH is said to be formed, this readily splitting up into Ag. 2 + H 2 0. SAPONIFICATION OF OILS. 31 mate constituents of fatty oils, and the theoretical proportions of fatty acid and glycerol resulting from their saponification : Products of Mole- Saponitication Glyceride. Chief Sources. Formula. cular of 100 parts. Weight. Fatty Glyce- Acid. rol. Glycyl tributyrate Butter-fat, C 3 H 5 (C 4 H 7 2 ) 3 , 302 87-44 30-46 (butyrin), Glycyl trivalerate (valerin), Porpoise oil, whale oil, C 3 H 5 (C 5 H 9 2 ) 3 , 344 88-96 26-77 Glycyl trilaurate Cocoanut oil, C 3 H 5 (C 12 H 33 2 ) 3 , 638 94-04 14-42 (laurin), palmnut oil, Glycyl tripalmitate Palm oil, lard, C 3 H 5 (C 16 H 31 2 ) 3 806 95-28 11-41 (palmitin), Glycyl tristearate Tallow, lard, C 3 H 5 (C 18 H 3 50 2 ) 3 890 95-73 10-34 (stearin), cacao butter, Glycyl trioleate (olein), Olive oil, almond oil, lard oil, C 3 H 5 (C 18 H 33 2 ) 3 , 884 95-70 10-40 Glycyl tribrassiate Eape oil, C 3 H 5 ( 033114302)8, 1052 96-39 8-75 (brassiin), Glycyl tri-linoleate Linseed and dry- C 3 H 5 (C 16 H 27 2 ) 3 , 794 95-21 11-58 (linolein), ing oils, Glycyl trihomolinole- Linseed oil, C 3 H 6 (C 18 H 31 2 ) 3 (?) 878 95-67 10-48 ate (homolinolein), Glycyl triricinoleate (ricinolein), Castor oil, C 3 H 5 (C 18 H 33 3 ) 3 , 932 95-92 9-88 The following table gives similar information respecting the more important fatty bodies or waxes having the constitution of ethers of monatomic alcohols : Products of Mole Saponification of Ether. Chief Source. Formula. cular of 100 parts. Weight. Fatty Monatomic Acid. Alcohol. Cetyl palmitate, Spermaceti, CieHss.CjgH^O^ 480 53-33 50-42 Myricyl palmitate, Ceryl cerotate, Bees' wax, Chinese wax, C 30 H 61 .C J6 H 31 2 , C 27 H 55 .C 27 H 53 2 , 676 788 3787 52-03 64-79 50-25 Dodecatyl oleate, Dodecatyl doeglate, Sperm oil, Bottlenose oil, C 12 H 25 .C 18 H 33 2 , ^is^as-^ig^ss^j 450 464 62-67 63-79 36-88 35-78 From an inspection of the first of these tables, it will be observed that, with the exceptions of butyrin and valerin, neither of which glycerides ever occurs in a state even of approximate purity in natural fixed oils, all the glycerides which form the chief proximate constituents of natural fatty oils yield approximately equal amounts 32 PRODUCTS OF SAPONIFICATION. of fatty acids on saponification, the proportions, if laurin be excepted, being constant within a range of about 1 per cent. Similarly the proportions of glycerin yielded by these same glycerides range within comparatively narrow limits. Hence it may fairly be asserted that the majority of fixed oils yield, on saponification, from 95 to 96 per cent, of fatty acids, and a proportion of glycerol approximating to 10 per cent. Oils containing the glycerides of butyric, valeric, lauric, or brassic acid such as butter fat, porpoise oil, cocoanut oil, and rape oil respectively show this peculiarity of constitution in the products of their saponification, and in the case of the three first of these oils, the proportion of glycerol resulting from their saponification is correspondingly, high. On the other hand, the bodies formulated in the second table yield, on saponification, much smaller proportions of fatty acids, and, instead of glycerin, give large proportions of higher alcohols of the ethylic series as solid bodies insoluble in water. It ^ evident that the nature and proportion of the products of saponi- fication sharply distinguish the oils from the sperm and bottle-nose whales from all other fluid fixed oils of commercial interest. Not only the proportion but the nature of the fatty acids produced on saponification is of importance in distinguishing the various fixed oils. Thus the drying oils yield chiefly linoleic acid, C 16 H 28 2 , or probably its homologue, C 18 H 32 2 , as a liquid product having a strong affinity for oxygen and combining with a large proportion of bromine or iodine, but not solidified by the action of nitrous acid. The liquid non-drying oils mostly contain oleic acid, which has comparatively little affinity for oxygen, and takes up less bromine or iodine than linoleic acid, but is solidified by treatment with nitrous acid. Eape oil contains brassic acid, which is not solidified by nitrous acid, and has . a very high molecular weight. All the foregoing acids, as likewise their homologues, form lead salts soluble in ether. On the other hand, the higher fatty acids of tjie stearic series form lead salts insoluble in ether; they are solid at ordinary temperatures, and they do not assimilate bromine or iodine. The lower members of the series (e.g., butyric and valeric acids) are soluble in water, and some of the intermediate numbers (e.g., lauric acid) volatilise to a notable extent in a current of open steam. Butter fat, porpoise oil, and cocoanut oil are instances of oils containing glycerides of these soluble or volatile fatty acids and consequently, as already stated, they yield larger proportions of glycerol than the majority of fixed oils. The proportions of fatty acids actually obtained on saponifying the various fixed oils fully bear out the foregoing theoretical views SAPONIFICATION OF OILS. 33 of their constitution, but owing to the difficulty which, till recently, attended its accurate determination, very discordant statements have been made respecting the proportion of glycerol actually formed by the saponification of fixed oils, and various ingenious theories have been advanced to account for the supposed deficiency. Wanklyn and Fox (Chem. News, xlviii. 49) assume the existence of hypothetical iso-glycerides in fatty oils. On saponifica- tion, these isoglycerides would yield isoglycerin, this instantly splitting up into a fatty acid and water, thus : CH 3 .CH 2 .C(OH) 3 = CH 3 .CH 2 .COOH + H 2 0. The only reaction tending to prove the existence of these isoglycer- ides is the production of ethylic butyrate when butter fat is heated with alcohol and a limited amount of caustic potash, but this for- mation is susceptible of another explanation. The statement made o,, TVanklyn and Fox that manufacturers never obtain more than 5 per cent, of glycerin on saponifying fats, is contrary to the ex- perience of some of the largest firms, who recover 7 '5 to 8 per cent., and take no notice of the considerable loss of glycerin by evapora- tion during the process of concentration, besides which the process of saponification is often far from complete. The following table gives the percentage of glycerol produced by the saponification of various oils and fats, as ascertained by the permanganate process (see "Glycerol"): 1 Glycerol per cent. Glycerol per cent. Kind of Oil. Kind of Oil. Benedikt and Zsigmondy. A. H. Allen. Benedikt and Zsigmondy. A. H Allen. Dcegling (Bot->^ tlenose) oil, .> Northern whalef ... 3-10* 11-96 Olive oil, Rape oil, Sesame oil, 10-1 to 11 -4 9-82* 9-94* Porpoise oil, Menhaden oil, ::: 11-09 11-10 Cottonseed oil, Linseed oil Castor oil, 9 -4 to 10-0 9-50* 9-39 9-13 Lard, 10-83 Oat-fat, . ... 8-35 Tallow, . 9-9 to 10-0 Butter fat, 10-2 to 11 '6 11-06 Cocoanut oil, 13-3 to 14:5 12-11 Palmnut oil, 11-70 Palm oil . 9-71 Japan wax, 10-3 to 11-2 11-6 to 14-7 Beeswax, none. ... Myrtle wax, ... 13-38 1 It is of interest to compare the figures in the table with the following results of M. E. Chevreul, given in his classical Recherches Chimiques sur les * The palm oil analysed contained a considerable quantity of free fatty acid. The figures marked with an asterisk were obtained in the author's VOL. II. 34 SAPONIFICATION OF OILS. These figures are very instructive. They negative the state- ment of Kb'nig, who could obtain no glycerin by saponifying oat- fat, 1 and but little from linseed oil. They also controvert the extra- ordinary assertions of Hammerbocker and Lehmann that cocoanut oil consists chiefly of free fatty acids, this fat actually yielding more glycerin -than the majority of oils, owing to the presence in it of glyceride of lauric acid and other fatty acids of comparatively low atomic weight. 2 The proportions of glycerin obtained in the author's laboratory by the analysis of Japan wax are higher than have been observed in the case of any other natural fat. To EFFECT SAPONIFICATION of fatty oils for general purposes of Corps Cfras d'origine animale, published in 1823. The glycerin was extracted and weighed as such after being purified by alcohol, dried in a vacuum, and the ash left on igniting it deducted from the gross weight found. The results are doubtless low, owing to unavoidable volatilization during concen- tration of the aqueous liquid. PRODUCTS OF SAPONICATION OF ANIMAL FATS Chevreul. Fat. Glycerin Non-Volatile Fatty Acids. Barium Salts of Volatile Fatty Acids. Human, 9-66 9618 trace. Pork, 8-82 95-90 trace. Beef, . 8-60 96-00 trace. Mutton, 8-00 96-50 3 Butter fat, 11-85 88-50 5-0 Porpoise oil, 14-00 82-20 16-0 The 5 per cent, of barium salts of volatile fatty acids from butter fat cor- responds to 2 '83 percent, of butyric acid, and the 16"0 per cent, from porpoise oil to 9 -63 per cent, of valeric acid. A sample of dolphin oil analysed by Chevreul gave 34 '6 per cent, of barium salts, but whale oil only 0*3 per cent. 1 The oat fat analysed was prepared in the writer's laboratory by extracting oatmeal with ether. It contained free fatty acid corresponding to 46 "3 per cent, of oleic acid. The total fatty acids amounted to 95 '18 per cent., and had a combining weight of 291'7. 2 Messrs Price & Co. now manufacture glycerin from cocoanut oil on a con- siderable scale. laboratory by the use of methyl alcohol, which experiment subsequently showed was not of satisfactory purit} 7 . Hence these results are probably somewhat in excess of the truth. The other figures of the author were obtained with aqueous potash, and have a tendency to be below the truth. Benedikt and Zsigmondy used methyl alcohol. Fox and Wanklyn recom- mend saponification in presence of ethyl alcohol, which would give excessive results, but they have not published any figures. SAPONIFICATl'ON OF OILS. 35 chemical analysis an alcoholic solution of caustic potash is by far the most convenient reagent. As the process is frequently employed, it is desirable to describe it once for all. An alcoholic solution of alkali is prepared by dissolving 80 grammes of good caustic potash in 1 litre of methylated spirit, which has been previously redistilled with a little caustic alkali. It is desirable to dehydrate the spirit by keeping it over a large excess of dry potassium carbonate. About 5 grammes of the clarified fatty oil is exactly weighed in a 4-oz. wide-necked flask, treated with 25 to 30 c.c. of the solution of alkali in spirit, and the flask closed with a cork fitted with a long tube. The flask is heated over boiling water, and as soon as the spirit boils the contents are mixed by circular agitation. In most cases the whole of the oil will rapidly disappear, forming a clear solution of soap, which may be further heated for a short time with occasional agitation, to ensure the complete saponifi cation of the fat. The cork is then removed, and the alcohol evaporated off. In the presence of unsaponifiable oil the contents of the flask should be allowed to boil until nearly dry, and the residue treated with 25 c.c. of spirit, and again boiled down. In cases where there is no danger of loss of hydrocarbon oils, or ethers of lower fatty acids, by incautious treatment, the saponifi cation and subsequent evapo- ration can be satisfactorily conducted in a hemispherical porcelain basin, placed over a small naked flame. The liquid is well stirred with a glass rod, and the liquid kept gently boiling until the alcohol is nearly driven off and the residual liquid froths strongly. By this time the whole of the oil should have disappeared, but, if incomplete saponification be suspected, 10 c.c. of alcohol may be added, and the evaporation repeated. To ensure the saponification of butter fat, codliver oil, the waxes, and other substances difficult to decompose, it is better to place the sample and alcoholic solution in a strong 6-oz. bottle, closed by an india-rubber stopper firmly fastened by wire. The bottle is then kept at 100 C., and fre- quently agitated during half an hour, or until no globules of oil can be seen, when it is opened, and the contents rinsed into a basin and evaporated over boiling water till the alcohol is expelled. Special precautions for insuring the saponification of waxes are described in the section on " Beeswax." SEPARATION OF THE PRODUCTS OP SAPONIFICATION. The solution of soap, freed in the foregoing manner from alcohol, should then be diluted with warm water till it measures 70 to 80 c.c. A per- fectly clear solution will usually be obtained if a pure fatty oil has been saponified and the process of saponification has been success- fully conducted, but waxes, and mixtures containing hydrocarbon 36 SEPARATION OF SAPONIFICATION-PRODUCTS. oils and certain other foreign matters, will give a solution contain- ing solid matter, or oily globules in suspension. These admixtures may usually be removed and determined by agitating the soap solution in a glass separator, with an immiscible solvent, ether being the most generally suitable for the purpose. 1 The ethereal layer is then separated, evaporated, and the residue weighed. The best method of manipulation is described on page 83. Cholesterin and other unsaponifiable matter are present in small proportion even in some of the purest fatty oils. 2 If ether has been employed, it should be got rid of by keeping the soap solution at a gentle heat for some time. On then treat- ing the soap solution with almost any acid, dilute sulphuric acid being generally preferable, a milky precipitate is produced, which, either at once or else on warming the liquid, will collect into globules, which rapidly rise to the surface and form an oily layer. This layer is not due to a re-formation of the original oil, but consists of the fatty acids produced from the oil. These fatty acids differ from the original glycerides in being soluble in alcohol, the solution having a more or less marked acid reaction. They also readily decompose the carbonates of the alkali-metals, liberating carbon dioxide and forming soaps. In most cases, these fatty acids are almost wholly insoluble in water and not sensibly volatile at 100 C., but by the saponifica- tion of butter fat, cocoanut oil, palmnut oil, porpoise oil, &c., pro- ducts are obtained which consist to a notable extent of the lower fatty acids, and hence the mixed fatty acids from these exceptional sources are partially soluble in water, and capable of distillation with vapour of water at 100 C. 1 Owing to the limited solubility of myricyl alcohol in most solvents, the method described in the text is attended with practical difficulties in the case of beeswax and carnaiiba wax, though it is admirably adapted for the analysis of spermaceti. If the removal of the separated higher alcohol by an immiscible solvent be found impracticable, the solution of the soap should be treated with acetic acid in quantity just sufficient to destroy the pink coloration produced by phenol-phthalein, and the solution precipitated by lead acetate. The precipitate should be washed, dried, mixed with sand, and the wax-alcohol dissolved by boiling petroleum spirit. 2 In rigidly accurate experiments it is desirable to treat the unsaponified residue in the same manner as the original oil, as traces of fat are liable to escape saponification by a single treatment. If the residue left on evaporating the ethereal solution be treated with a little hot alcohol, the solution filtered hot, and the filtrate cooled, and, if necessary, allowed to evaporate spontaneously, crystalline plates of cholesterin will often be deposited. "Wool fat contains a considerable proportion of cholesterin, and the writer has proved its presence, by the above method, in butter fat, codliver oil, &c. , SEPARATION OF SAPONIFICATION-PRODUCTS. 37 For the separation of these soluble or volatile acids from oils con- taining these glycerides, the soap solution is acidulated with sul- phuric acid in the manner already described. The aqueous solu- tion is separated from the layer of fatty acids, and the latter several times boiled up with a considerable quantity of water in a flask furnished with a long tube or inverted condenser. The aqueous liquids resulting from these operations are separated from the in- soluble fatty acid's, which it is desirable to again boil with a moderate quantity of water, whilst driving a current of steam through the flask in which they are contained, collecting the dis- tillate, and treating it like the washings. 1 The acidulated aqueous liquid first separated from the layer of fatty acids is then distilled to a low bulk, and the distillate exactly neutralised with a standard solution of pure caustic soda or baryta, using phenol-phthalem as an indicator. The first washings from the insoluble fatty acids are then added to the contents of the retort, and the liquid again dis- tilled to a low bulk, the process being repeated with the succeed- ing washings. The different distillates obtained should be titrated separately with decinormal standard alkali and phenol-phthalein, as, in this manner, with but little extra trouble, the progress and completion of the washing, &c., can be followed, and useful infor- mation obtained as to the probable nature and relative proportions of the lower fatty acids present. The several neutralised distillates may now be united and evaporated gently to dryness, the residue^ being dried at 100 C. till constant. It consists of the sodium or barium salts of the fatty acids which passed over in the preceding distillation. If the total volume (in c.c.) of normal caustic soda employed for the neutralisation be multiplied by 0'022, or the volume of normal baryta solution by 0'0675, and the number so obtained be sub- tracted from the gross weight (in grammes) of the dry residue, the difference will be the weight of the volatile fatty acids. Their mean combining equivalent will be found by dividing their weight by the volume (in c.c.) of normal alkali required for their neutral- isation. A further examination of the volatile fatty acids can be made by distilling the barium or sodium salts with phosphoric or diluted sulphuric acid, and examining the distillate as indicated in vol. i. p. 405 et seq. A very useful method of examining fatty oils for volatile acids 1 When cocoanut or palmnut oil is treated in this manner, the distillate will be found to contain lauric acid, which, though almost insoluble in water, is volatile in a current of steam. It may be separated from the more soluble volatile fatty acids by filtering the distillate. 38 INSOLUBLE FATTY ACIDS. has been devised by Rei chert. It consists in distilling over an aliquot part of the acidulated solution of the saponified sample, and titrating the distillate with standard alkali. The details of the manipulation and the results yielded by different oils will be found on pages 45 and 46. Although necessarily described at some length, the foregoing method of isolating the lower fatty acids is not in practice so tedious as might be supposed ; and it may be remembered that in cases where the oil under examination is known not to contain any appreci- able quantity of .glycerides of the lower acids, the treatment for their isolation may be wholly omitted, and the insoluble fatty acids are practically identical with the total fatty acids liberated on adding a ^dilute mineral ^& to the aqueous solution of the soap. The oily layer thus obtained should lie .shaken several times with warm water, or until, after separation, the aqueous liquid is found to be free from acid reaction to litmus. The subsequent treatment of the insoluble fatty acids will depend on the nature and extent of the information required. In some cases it will be sufficient to add alcohol and titrate with standard alkali and phenol-phthalem, as described on page 76. If the fatty acids are to be weighed, the best mode of operating is to run them from the separator into a small paper filter previously wetted with hot water. The funnel containing the filter is placed in the mouth of a small dry beaker, and the whole heated in the water-oven. As the filter dries, the greater part of the fatty acids will pass through the paper into the beaker. When no more drops through, the funnel is removed to a small dry flask, and the fatty acids adhering to the separator or other vessels removed by means of ether, carbon disulphide, or gasolene. The solution thus obtained is poured into the filter and caught in the flask below. A fresh quantity of the solvent is used to effect complete solution and removal of the fatty acids from the filter, these washings also being allowed to run into the flask. The solvent is then distilled off by immersing the flask in hot water, and the residual fatty acids further dried by blowing a current of air through the flask till they come to lose weight, or till all odour of the solvent has disappeared. The weight of fatty acids thus determined is added to that of the main quantity con- tained in the beaker, and the sum gives the insoluble fatty acids in the amount of fat employed for the analysis. 1 In most cases the 1 The method of treating the insoluble fatty acids described in the text possesses several advantages. Thus the greater part is at once obtained in a filtered and perfectly dry state, without having been subjected to prolonged heating and without the use of any solvent, the last traces of which are apt to be retained with tenacity. The process recommended is especially suited to PROXIMATE ANALYSIS OF OILS. 39 determination of the total insoluble fatty acids is sufficient, but, if desired, a further proximate analysis can be made by the methods indicated in the section on " Higher Fatty Acids." The acidulated aqueous liquid remaining after the isolation of the insoluble fatty acids, and the removal of any volatile fatty acids by distillation, contains glycerol, which may be isolated by exactly neutralising the free acid with potash, evaporating the solution to dryness on the water-bath, and exhausting the residue with alcohol. On filtering and evaporating the alcoholic solution, the glycerol is obtained as a sweet syrupy liquid, which may be further purified by treatment with a mixture of alcohol and ether and evaporation of the filtered solution. Although glycerin result- ing from the saponification of oils may be readily isolated in this manner, the results obtained are only very roughly quantitative, owing to the loss of glycerin during the several evaporations. 1 The determination of the glycerol produced by saponification is most accurately effected by determining the oxalic acid produced by its oxidation with permanganate, as described in the section on " Glycerol." The following table shows in a .condensed form the general process, just described, for the separation of the products of saponification of genuine fixed oils. The method of detecting and determining foreign additions to fixed oils (e.g., resin, hydrocarbon oils, soap, &c.) are described in a separate section (page 74) : Saponify the oil with alcoholic potash, evaporate off the alcohol, dissolve the residual soap in water, and agitate the solution with ether. ETHEREAL SOLUTION contains cholesterin, hydrocarbons, unsa- ponijfied oil, and higher alcohols, (from waxes, sperm oil, Tallow, K., D. 9 19 -32 to 19 -80 Dripping, . K. 2 19-65 to 19-70 Butterine, . Goose fat," . M., A. V. large 19-35 to 19.65 19-26 j, 277 to 294 Bone fat, . V., LA. 2 19-09 to 19-71 Palm oil, . M., V. 3 19-63 to 20-25 Cacao butter, . V. 1 19-98 - G. FLUID WAXES Sperm oil, . S.,D., A. 10 12-34 to 14-74 380 to 454 Bottlenose oil, . A., LA., D. 5 12-30 to 13-40 419 to 456 H. SOLID WAXES Spermaceti, H. 3 12-73 to 13-04 432 to 441 Beeswax, . H., HI., A. large 9-2 to 9-7 Carnaiiba wax, H1.,V.,H.,LA 4 7 -90 to 8-51 SAPONIFICATION-EQUIVALENTS. 43 Nature of Oil. Initial of Observer. No. of Samples. Percentage of KHO for Saponi- fication. Saponification Equivalent. I. UNCLASSED Shark-liver oil, A. 6 14-00 to 19 -76 284 to 400 Wool fat' (suint), . V. 1 17-00 330 Olive-kernel oil, V. 1 18-85 298 Castor oil, . S., D.,A., V. 6 17 -60 to 18 -15 309 to 319 Japanese wood oil, . Davies. 1 21-1 266 Japan wax, H.,H1.,V.,A. 8 21 -01 to 22 -25 252 to 267 Myrtle wax, D. A. 2 20 -57 to 21 -17 265 to 273 Blown rape oil, LA., A. 3 19-8 to 20 -4 275 to 284 Colophony, H., A., D. 4 17-0 to 19-3 290 to 330 On inspecting the results recorded in the foregoing table, it appears that the oils of Group A, consisting of olein with com- paratively little stearin or palmitin, neutralise appreciably equal quantities of potash, and that whether of animal (like lard oil) or vegetable origin (e.g., olive and almond oils). On the other hand, the oils of Group B, all of which are derived from cruciferous plants, neutralise sensibly less alkali than those of Group A, a fact which is explained by the presence of a considerable propor- tion of brassic acid, or other higher homologues of oleic acid, in rape oil and its allies. In the case of the drying oils, the saponifi- cation-equivalents are not characteristic, but they point to the probability of linoleic acid having a higher atomic weight than that commonly attributed to it. (See " Linseed Oil.") The marine animal oils, Group D, do not yield very characteristic results, except in contrast with the figures of Group G, the oils of which are not glycerides, but consist essentially of ethers of monatomic alcohols. Porpoise oil is remarkable for the notable proportion of valerin contained in it, and hence for its comparatively high neutralising power. 1 Of the solid fats, those of Group E resemble porpoise oil in containing glycerides of lower fatty acids, and hence possess lower saponification-equivalents than the oils of Group F, which consist essentially of variable mixtures of palmitin, stearin, and olein. The peculiar constitution of the true waxes (Group H) is indicated by their limited power of neutralising alkali, while the figures recorded for the unclassed oils are equally instructive, and are discussed at greater length in the special sections dealing with these bodies. 1 The glyceride of valeric acid also exists to a considerable extent in whale oil, blackfish oil, and dolphin oil. Chevreul obtained from the last-named oil as much as 20 '9 per cent, of valeric acid. 44 SAPONIFICATION-EQUIVALENTS. As hydrocarbon oils do not react with potash, the proportion of these oils in admixture with fatty oils can be deduced from the amount of alkali requisite for the saponification of the sample. Thus, if a sample of so-called "linseed oil" require only 9 '5 per cent, of KHO for its saponification, instead of 19*0 per cent., it may be safely assumed to contain 50 per cent, of hydrocarbon oil. The Determination of the Saponification-Equivalent of an oil is best effected in the manner described by Koettstorfer (Zeits. Anal. Chem., 1879, p. 199; Analyst, iv. 106), who applied it originally to the analysis of butter. The following are the details of the operation : -About 2 \ grammes weight of the oil, accurately weighed, is treated with 25 c.c. of approximately seminormal solu- tion of caustic potash in alcohol, 1 in a flask fitted with a long vertical tube. The flask is heated on |he water-bath for about half an hour, or until complete solution of the fat takes place, and the saponification is judged to be complete. The operation is greatly expedited by subjecting the contents of the flask to frequent rotatory agitation. 1 c.c. of an alcoholic solution of phenol-phtha- lein is then added, and the liquid titrated with semi-normal hydro- chloric acid ; 25 c.c. of the same alcoholic potash, very carefully measured, should then be similarly treated without addition of fat, and titrated with hydrochloric acid in the same way as before. The difference between the volumes of standard acid used in the two testings gives the number of cubic centimetres corresponding to the alkali neutralised in saponifying the oil. Each cubic centi- metre of semi-normal hydrochloric acid (=18*25 grammes HC1 per litre) thus employed represents 0'02805 of KHO, whence the percentage of caustic potash required to saponify the oil can readily be ascertained. The saponijication-equivalent of the oil is found by dividing the weight of the sample employed, expressed in milligrammes, by the number of cubic centimetres of normal (not semi-normal) acid corresponding to the alkali neutralised by the oil. 2 If the percentage of potash required be known, the 1 The alcohol employed for making the solution should be previously dehydrated by keeping it over an excess of dry potassium carbonate. Methylated spirit may be used if it be first distilled with a little caustic potash. 2 Thus, if 3100 grammes of oil have been employed, and the volume of semi-normal acid corresponding to the alkali neutralised was 21 '3 c.c. ( = 10 '65 normal acid), then : =291-1 16-65 2911i REICHERT'S DISTILLATION PROCESS. 45 saponification-equivalent can be found by dividing this percentage into 56 10. 1 A further refinement of Koettstorfer's process consists in ascer- taining separately the amounts of alkali required for neutralising the free fatty acids (see page 76), and for saponifying the neutral glycerides or other ethers of the sample. A notable instance of the value of this mode of examination is the assay of beeswax by Hehner's method, which modification of the process is described in the sequel. It should always be employed when a wax or other substance difficult to saponify is under treatment. In employing Koettstorfer's simple and ingenious method of examining fatty oils, it is necessary to use alcoholic alkali as free as possible from colour, as any yellow or brownish tint materially affects the delicacy of the acid-reaction with phenol-phthalein ; while, under favourable conditions, the change from pink to yellow is very sharply marked. Carbonic acid, however, seriously in- fluences the reaction; and hence the saponification and titration should be conducted with as little access of air as possible. It is absolutely necessary to ascertain the strength of the alcoholic alkali from day to day, as such solutions rapidly alter, and the mere heating is liable to cause a slight change in the neutralising power. Standard sulphuric acid cannot be conveniently substituted for the hydrochloric acid recommended for the titration, as its 'employment causes a precipitation of sulphate, which masks the end of the reaction. KEICHERT'S DISTILLATION PROCESS. Instead of ascertaining the proportion of alkali required to unite with the fatty acids of an oil, which is practically what is effected in Koettstorfer's process, a very useful practical method of examining fats consists in determining the amount of alkali required to neutralise the volatile fatty acids. This method of examination is due to Eeichert (Zeits. Anal. Chem., xviii. 68), who suggested its use for the assay of butter. Its value has been fully confirmed by other chemists, including the writer; but as the process is an arbitrary one, only about foiir- fifths of the entire volatile fatty acids of butter being found in the distillate under the conditions of operation, it is necessary to adhere to the following mode of operation : Saponify 2 '5 grammes of the fat with 25 c.c. of approximately seminormal alcoholic potash, by heating it in a closed bottle or flask fitted with a long tube, as described on page 44. Transfer the product to a porcelain rcent. ; and KH per C6nt = sap. -equivalent milligrammes of fat employed Also, Sap-equivalent^^ of normal alkali neutralised by it. 46 EEICEEET'S DISTILLATION PROCESS. basin, and evaporate off the alcohol completely at a steam heat. Dissolve the residual soap in water, add dilute sulphuric acid in slight excess, dilute the liquid with water to 75 c.c., add some fragments of pumice coiled round with platinum wire, and distil gently till 50 c.c. have passed over. Filter the distillate, if not quite free from white flakes or oily globules, wash the filter with a little hot water, and titrate the clear solution with decinormal caustic alkali, using phenol-phthalem as an indicator. 1 The following table shows the results yielded by several fatty oils when assayed by Reichert's distillation process. In the first column of figures is given the number of centimetres of decinormal alkali required to neutralise the volatile acids in the distillate from 2 '5 grammes of oil, and |n the second the parts of potassium hydroxide neutralised by the distillate from 100 grammes of oil. The second number is obtained by multiplying the first by 0'2244. Fatty Oil. No. of c.c. of *** required. KHO required by 100 of oil. Observer. Butter or Milk-fat ; Cow's, Ewe's, . ,, Goat's, . Porpoise's, Cocoanut oil, .... Palmnut oil, .... Palm oil 12-5 to 15-2 13-7 13-6 11-3 3-5 to 37 2-4 0-8 2 -80 to 3 -41 3-07 3-05 2-51 0-78 to 0-83 0-54 0-18 Reichert, Cald- well, Moore, Allen, &c. ' Schmitt. Allen. Eeichert, Moore, Allen. Allen. Moore Cacao butter, .... Butterine and Oleomargarine, Whale oil 1-6 0-2 to 1-6 37 0-36 0-04 to 0-36 0-83 CaYdwell, Moore, Allen. Allen. 12-5 80 Porpoise oil, . . . . Sperm oil . 11 to 12 1-3 2-47 to 2-69 0-29 ? Bottlenose oil, .... Menhaden oil, .... Codliver oil, .... 1-4 1-2 1-1 to 2-1 0-31 0-27 0-24 to 0-47 ) Sesame oil, .... Cottonseed oil, .... Castor oil 2-2 0-3 1-4 0-48 0-07 0'31 Moore. Allen. 1 When the acidulated soap from cocoanut or palmnut oil is distilled, a notable proportion of lauric acid passes over and solidifies in the condenser or on the surface of the distillate. This should be removed by filtration, or the distil- late will be found to neutralise so large a volume of alkali as considerably to diminish the practical value of the process, especially as a means of distinguish- ing butter from butter-substitutes. By adding water to the contents of the retort, again distilling, and repeating this process several times, a very con- siderable proportion of volatile fatty acids can be obtained from cocoanut oil. BROMINE-ABSORPTIONS OF OILS. 47* From these results it is evident that the fats of different kinds of milk (butter fats) are sharply distinguished from nearly all other fats by the large proportion of soluble volatile fatty acids they yield by Eeichert's process. The most remarkable exception is that of porpoise oil, and sometimes whale oil, in the former of which the writer found 5 per cent, and Chevreul -as much as 9 '6 3 per cent, of valeric acid, the glyceride of which acid appears to replace in porpoise butter the butyrin of the butter of terrestrial mammals. Bromine and Iodine Absorptions of Fixed Oils. Another method of examination based on the chemical consti- tution of the fixed oils, and which is occasionally of considerable service, is dependent on the percentage of bromine or iodine taken up by the oil under conditions intended to ensure the formation of additive compounds only. The fatty acids of the acetic or stearic series are saturated bodies, which do not form additive compounds with iodine or bromine, while the acids of the acrylic or oleic series combine with two atoms of a halogen and those of the pro- polic or linoleic series with four atoms of a halogen, as expressed by the following equations. Thus Stearic Acid, C 18 H 36 2 , does not combine with bromine or iodine. Oleic Acid, C 18 H 34 2 , forms C 18 H 34 Br 2 2 , and C 18 H 34 I 2 2 . Homolinoleic Acid, C 18 H 32 2 , forms C 18 H 32 Br 4 2 , and C 18 H 32 I 4 2 . The glycerides of the acids of these three series behave similarly to the free acids, so that a determination of the percentage of bromine or iodine assimilated gives a measure' of the proportion of olein against palmitin and stearin in a fat, and of the linolein of a drying oil as compared with the olein of a non-drying oil. THE BROMINE- ABSORPTIONS of various fixed oils have been deter- mined by Mills, Snodgrass, and Akitt (Jour. Soc. Chem. Ind., ii. 435 ; iii. 366), the method of operating ultimately adopted being shortly as follows : About O'l gramme of the oil, previously deprived of all trace of moisture by heating or filtration through paper, is placed in a stoppered bottle of about 100 c.c. capacity, and dissolved in 50 c.c. of carbon tetrachloride, previously dried by calcium chloride. An approximately decinormal solution (8 grammes per litre) of bromine in dry carbon tetrachloride, having an exactly known strength, is then added gradually to the solution of oil, until there is, at the end of fifteen minutes, a permanent color- ation. This is compared with a coloration similarly produced in a blank experiment, and thus a measure of the bromine-absorption is obtained. If great accuracy be desired, an excess of bromine may be used, aqueous solution of potassium iodide and starch added, 48 IODINE-ABSORPTIONS OF OILS. and the solution titrated back with a standard solution of sodium thiosulphate ; or the excess of bromine may be determined by titrating back with a standard solution of /3-naphthol in carbon tetrachloride, which reacts with bromine in the ratio Br 2 : C 10 H 8 0. When the brominated product has a yellow colour, as happens with some fish oils, the point at which the bromine is in excess is best observed through a solution of neutral potassium chromate. THE IODINE- ABSORPTIONS of various fixed oils have been deter- mined by Baron Hiibl (Dingl. Polyt. Jour., ccliii., 281; Jour. Soc. Cliem. Ind., iii. 641), who, for several reasons, prefers this estimation to that of the percentage of bromine assimilated. When employed alone, iodine reacts very slowly, and hence Hiibl uses an alcoholic solution of iodine in conjunction with mercuric chloride, in the proportion of 1 molecule (I 2 ) of the former to at least 1 (HgCl 2 ) of the latter. It is prepared by dissolving 25 grammes of iodine in 500 c.c. of nearly absolute alcohol (free from fusel oil), and 30 grammes of mercuric chloride in an equal measure of the same solvent. The latter solution is filtered, if necessary, and then added to the tincture of iodine. The mixed solution should be allowed to stand for twelve hours before being used, as, owing to the presence of impurities in the alcohol employed, it is liable to undergo considerable reduction in strength, and must in all cases be restandardised immediately before or after use. The strength is ascertained by titration with decinormal solution of sodium thiosulphate ("hyposulphite"), which in its turn is set by a solu- tion of resublimed iodine in the usual way. The mercurial iodine solution reacts with ease at ordinary temperatures on either free unsaturated fatty acids or their glycerides to form chloro-iodo- addition products, the total proportion of halogen assimilated being estimated in terms of iodine. For the purpose of determining the iodine-absorption of an oil, from 0*2 to 0'3 gramme of a drying oil, 0*3 to 0'4 of a non-drying oil, or from 0'8 to I'O gramme of a solid fat, should be weighed accurately, and dissolved in 10 c.c. of chloroform. The solution is mixed in a stoppered flask with 20 c.c. of the standard solution of iodo-mercuric chloride, and if the liquid is not quite clear after agitation a further addition of chloroform is made. If the mixture becomes decolorised, or nearly so, after standing a short time, a further addition of 5 or 10 c.c. of iodine solution must be made. To ensure accurate results, the excess of iodine must be consider- able, and hence the liquid ought still to be quite brown after stand- ing for two hours. 1 After that time, from 10 to 15 c.c. of a 10 1 Hiibl found that when dealing with free fatty acids the reaction was com- pleted when only a small excess of iodine was present, but that with glycerides IODINE-ABSORPTIONS OF OILS. per cent, aqueous solution of potassium iodide should be added, and the whole diluted with about 150 c.c. of water. The free iodine, part of which exists in the aqueous and part in the chloro- formic solution, is then determined by titration with thiosulphate, the contents of the flask being frequently agitated, and starch solution being added just before the end of the reaction. A blank experi- ment with the same quantities of chloroform, iodine solution, &c., is made side by side with the actual test, so as to correct for any impurities in the reagents and to ascertain the true strength of the iodine solution. The additional thiosulphate required in the ex- periment in which the oil was employed is then calculated into its equivalent of iodine, and this to units per cent, of the oil. The product formed by the action of iodo-mercuric chloride on pure oleic acid is a greasy substance, which is colourless at first but gradually turns brown from liberation of iodine. Determina- tions of the chlorine and iodine, as also of its saponification- equivalent, show the compound to be a chloro-iodo-stearic acid of the formula C 18 H 34 2 , IC1. The similar products formed by the action of the iodine solution on glycerides are colourless, viscous, or resinous masses, which in general resemble the original fats. It was found that in order to render the whole of the iodine available, the presence of mercuric chloride in a ratio not less than HgCl 2 : I 2 was essential. Hiibl states that, when tested by the foregoing process, chemi- cally pure oleic acid assimilated from 89 '8 to 90'5 per cent, of iodine, the theoretical proportion required for the reaction C 18 H 34 2 + 1 2 = CjgH^IgC^ being 90'07 per cent. On the other hand, most of the non-drying vegetable oils assimilate a notably larger proportion of iodine than corresponds to the percentage of olein present, and the difference cannot in all cases be attributed to the presence of linolein or its homologues. Mills states that olive oil, purified by filtration after long deposition in the cold, washing, and drying over oil of vitriol, assimilated 54'0 per cent, of bromine, against 5 4 '3 per cent, theoretically required to form the brominated compound C 3 H 6 f(C ]8 H 33 Br 2 0.0) 3 . Hiibl's process has been examined by E. W. Moore (Amer. Chem. Jour., vi. 6; Chem. News, li. 172), who finds it most con- a larger excess must be employed, otherwise the results obtained will be too low. In presence of a sufficient excess of iodine, variations in the concentra- tion of the fatty solution and in the amount of mercuric chloride present do not affect the results. The reaction should be allowed to continue for at least two hours (or, according to Archbutt, six hours), but an extension of the time of treatment to twenty-four or forty-eight hours does not influence the ab- sorption. VOL. II. D 50 HALOGEN-ABSOEPTIONS OF OILS. venient and expeditious, and the transition-point of the final reaction extremely sharp. Archbutt, who has also used the pro- cess, agrees with Moore in recommending that a very considerable excess of iodine should be employed. The following table shows most of the results of Mills, Hiibl, and others in juxtaposition. The bromine- absorptions found by the first chemist have been calculated by the writer into the equi- valent percentages of iodine, so as to allow of more ready com- parison with the direct iodine-absorptions of Hiibl and others. The iodine-absorptions can be calculated into the equivalent percentages of t r i o 1 e i n by multiplying them by the factor 1 '1 52. Nature of Oil. Bromine-absorption; per cent. Mills. Iodine-absorption ; per cent. 127 -g-Q- Br-absorption. Hiibl. Other observers. Almond (sweet) Almond (bitter) 53-7 26-3 . 85-3) 41 -8 f 97-5-98-9 98-1* Peach-kernel , 25-4 40-4 Apricot-kernel, 70 -OJ 111-1J 99-102 ... Olive-kernel, 81-8 Olive, . 54-6-60-6 85-9-96-4 81-6-84-5 83 : 0* Earth-nut (Aracl is), 46-2 73-3 101-105 87-4* Rape, . . 69-4 110-4 97-105 101-104*+ Sesame, 47-4 75-2 105-108 102-7* Cottonseed, 50-0 79-5 105-108 106-109*+ Poppyseed, 56-5 89-9 135-137 134-0* Nigerseed, . 132 -9f Linseed (raw), 76-0 120-8 156-160 155-2* Linseed (boiled) Castor, 102-4 58-3 162-8 92-7 148 84-0-84-7 84 : 3+ Menhaden, . 147 -9f Cod-liver, . 81-6-86-7 129-5-137-6 ... Ling-liver, . 82-4 131-0 Seal, . . . 57-3-59-9 91-2-95-3 ... Whale, 50-9 80-9 . Bottlenose, 48-7 77-4 , 80 : 4+ Sperm, -. . ... ... 84-3+ Neatsfoot, . 66-0 71 -9f Palm, . 34-8-35-4 55-3-56-3 50-4-52-4 50-3* Cocoanut, . 5-7 9-1 8-9 8-9* Cacao butter, 34-0 Japan wax, 1-5-2-3 2-4-3-7 4-2 Butter fat, . 24-5-27-9 38-9-44-4 26-0-35-1 19-5-38-0* Butterine, . 36-3-39-7 57-7 63-1 55-3 50-0* Lard, . 37-3 59-3 59-0 61-9* Tallow, 40-0 Beeswax, . 0-6-0-54 0-6-0-86 ... Carnaiiba wax, 33-5 53-3 ... These figures are very instructive. They indicate that the drying oils, containing linoleic acid, assimilate the largest propor- tions of the halogens, and their capacity in this respect might * R. W. Moore. + L. Archbutt. T. Maben. OXIDATION OF OILS. 51 probably be employed as a measure of their drying powers. It is remarkable, however, that while Mills attributes a considerably higher absorption to boiled than to unboiled linseed oil, Hiibl dis- tinctly states that a sample of linseed oil which showed an iodine- absorption of 156 when raw, after boiling required only 148 per cent. The fish-liver oils, however, fully equal the vegetable drying oils in their assimilating powers for halogens. The results of Hiibl may be regarded as in the main confirming those of Mills, but there is an exception in the oil expressed from bitter almonds, which is usually supposed to be nearly pure olein, and hence to have a similar composition to olive oil,' but if Mills' figures be correct, this is clearly not the case, and such almond oil must consist largely of glycerides of saturated (solid) fatty acids. Similarly, the oils from peach-kernels and apricot-kernels might be expected to be of sub- stantially similar nature, but this does not appear by the table. On the other hand, even in non-drying oils like olive, which are presumably free from glycerides of the linoleic series, the propor- tion of olein, corresponding to the halogens assimilated, exceeds 100 per cent., a fact which is difficult to explain in the face of the statement that pure olein and oleic acid absorbed the amount of halogen required by theory. Hiibl's figure for cacao butter indi- cates that this fat is not approximately pure stearin, as commonly represented. The low figures of both Mills and Hiibl for Japan wax are remarkable, as is also the difference between the absorptions of carnaiiba and bees' wax. The results of Moore prove the general accuracy of Hiibl's observations. The process devised by the latter chemist is of great value and extensive utility, and its use for discriminating between different oils is at once apparent. Oxidation of Oils Drying Properties. As stated shortly on page 3, many of the liquid fixed oils thicken on exposure to air, and, under favourable circumstances, gradually dry up into yellowish transparent varnishes or resins. The oils which possess this property are termed drying oils, and appear to contain the glyceride of linoleic acid or its homologues. For testing the drying properties of an oil, a definite number of drops of the sample may be placed in a watch glass or flat porcelain capsule, and exposed to a temperature of about 100 C. for twelve or twenty-four hours, side by side with samples of oil of known purity. Olive oil will be scarcely affected by such treatment, and rape oil will only thicken somewhat. Cottonseed oil will be considerably affected, while good linseed oil will form a hard skin or varnish, which can only with difficulty be ruptured by pressure 52 OXIDISED OILS. with the finger. In some respects, a preferable plan is to flood a slip of glass with the oil to be tested, in the manner in which a glass-plate is covered with collodion. The glass with the adhering film of oil is then kept at 100, and the progress of the drying watched by touching, at intervals, successive parts of the plate with the finger. Another useful method is to soak a definite measure of thick filter paper in the sample of oil, and then expose it to 100 or 130 C. for some hours, side by side with samples of oil of known purity. Gellatly has pointed out the close relationship which exists between the drying properties of oils and their tendency to inflame spontaneously when exposed to the air in a finely divided condi- tion. He found that when a handful of cotton-waste was imbued with the oil to be tested, and placed somewhat loosely in a paper box in an air-bath kept at 80 C., the mass entered into active combustion after a time dependent on the nature of the oil used. Thus, with boiled linseed oil inflammation occurred in little more than an hour, while raw linseed oil required four hours, and rape oil nine or ten to reach the same stage. Equal parts of seal oil and mineral oil refused to ignite, and even 20 per cent, of mineral oil materially delayed the ignition. The facts noted by Gellatly are interesting, and some of them have been confirmed by Renouard (Jour. Soc. Chem. Ind., i., 184) and other observers, but the method has no claims to quantitative accuracy, even of the roughest kind. Other methods of testing the oxidisability or drying character of linseed oil are described in the special section treating of that important oil. Although frequently grouped as "drying" and "non-drying" oils, there is no sharp distinction between the two classes. Omit- ting the oils from marine animals, some of which dry rapidly, the chief commercial liquid fixed oils possess drying properties in the order of the following list, the most rapidly oxidisable being placed first : Linseed oil, cottonseed and fancy seed oils, rape oil, arachis oil, olive oil, animal oleins. The tendency of the fixed oils to dry or oxidise is in the direct order of their capacity for absorbing bromine or iodine, and of the rise of temperature produced on mixing them with concentrated sulphuric acid. OXIDISED OIL. BLOWN OIL. During the last few years there have appeared in commerce certain articles known as "oxidised oils," "blown oils," or "base oils." These are produced by blow- ing a stream of air through a fatty oil, rape, cottonseed, or linseed oil being usually chosen for the purpose. A certain initial tem- perature is necessary to start the reaction, but afterwards the heat TEMPERATURE-REACTIONS OF OILS. 53 produced by the oxidation is amply sufficient to maintain the temperature required. By proper regulation of the process, products can be obtained which closely simulate castor oil, and fully equal that body both in density and viscosity. Methods of distinguish- ing the blown oils from true castor oil are given in the section treating of the latter product (page 129). Temperature-Reactions of Oils. The rise of temperature which ensues on treating a fixed oil with concentrated sulphuric acid, concentrated nitric acid, bromine, &c., is, of course, a measure of the extent and intensity of the chemical reaction which ensues. The only reaction of oils which is practically available for the purpose in question is that with concentrated sulphuric acid, the use of which was originally proposed by Maumene' (Compt. rend., xxxv., 572). The test has been in- vestigated by Fehling, Faisst and Knauss, J. Muter, L. Archbutt, J. Baynes, and other chemists, who have arrived at very different opinions as to the value of its quantitative indications. The dis- crepancies observed have certainly been largely due to insufficient care being taken to ensure exactly similar conditions of working. Foremost among the sources of error is unnoticed variation in the strength of the acid. Thus Maumene' obtained such a much higher rise of temperature on employing recently heated sulphuric acid that he imagined the existence of an isomeric variety of this body. Until recently the specific gravity of concentrated sulphuric acid was regarded as a sufficient evidence of its strength, but Lunge and Naef have shown that acid of 96 per cent, and of 99 per cent., and even of 95 per cent, and 100 per cent., have almost exactly the same density. Further, L. Archbutt has found that commercial concentrated sulphuric acid varies considerably in strength, the samples examined by him ranging in strength from 92*7 to 97*4 per cent, of H 2 S0 4 , as ascertained by very careful titration with standard alkali. He gives the specific gravity of 97 per cent, acid as 1-8440 at 60 F. ( = 15'5 C.). L. Archbutt finds that if the acid employed be much weaker than 97 per cent, of H 2 S0 4 , the increase of temperature is not only notably less, but the reaction is inconveniently slow. On the other hand, the initial temperature of the oil and acid does not affect the extent of the rise on mixing them, but care must be taken that they are both at the same temperature, or an erroneous result will obviously be obtained. The following method of performing Maurnene's test is that recommended by Archbutt, and employed by the writer : 50 grammes of the oil is weighed into a 7 ounce beaker, and the latter immersed in a capacious vessel of 54 TEMPERATUKE-KEACTIONS OF OILS. water, together with the bottle of strong sulphuric acid, until they are both at the same temperature, which should not be far from 20 C. The beaker containing the oil is then wiped, and placed in a cotton-wool nest previously made for it in a cardboard drum, or a wider beaker. The immersed thermometer is then observed, and the temperature recorded. 10 c.c. of the concentrated sul- phuric acid should then be withdrawn from the bottle with a pipette, and allowed to run into the oil. During the addition of the acid, which should occupy about one minute, the mixture must be constantly stirred with the thermometer, and the agitation con- tinued till no further rise of temperature ensues. This point is readily observed, as the indication remains constant for a minute or two, and the temperature then begins to fall. The results obtained from a particular oil are remarkably con- stant when the acid is of a uniform strength, and a denned method of manipulation is rigidly adhered to, but apparently insignificant differences in the mode of operation result in serious discrepancies in the results. Thus, Archbutt observed a rise of 78'5 when the oil was stirred till all the acid was added, and the thermometer then held stationary in the middle of the oil, but when the stirring was continued till no further rise of temperature was observed, the increase was only 73'd . 1 In the view of the writer, the object sought to be attained by Maumene"'s test is a determination of the intensity of the chemical action between the oil and the acid when employed in the propor- tions prescribed. It is evident that there may readily be local overheating, and that the uppermost strata of oil, and the froth on the surface are likely to be at the highest temperature, but the information sought is the maximum temperature attained by the whole mixture, taking care to avoid loss as far as possible by 1 The effect of stirring has also been observed by J. Baynes, who, in a com- munication to the author, recommends that the experiment should always be commenced at 20 C. ; that the acid should have a density of 1 *845 ; and that the mixture be effected in a cylinder If -inch wide, tightly packed in fibrous asbestos, instead of in a beaker in a nest of cotton- wool. He adds the acid during one minute, stirring continuously, and for a further period of five seconds only. The bulb of the thermometer is then held as closely as possible to the top layer of the froth, for if lowered a considerable fall in the temperature will be observed. Should the mixture show a tendency to froth over, it may be kept down by stirring, but the thermometer should be observed before doing so. J. Muter first brings the oil and acid to a temperature of 28 C., and operates in a wide tube of thin glass mounted on a foot. The acid is added to the oil at the rate of 1 c.c. per five seconds, and the stirring continued during the addition, and for thirty seconds afterwards. TEMPERATURE-REACTIONS OF OILS. 55 surrounding the vessel with a non-conducting medium. These conditions are best attained by using a thin vessel, well surrounded with cotton-wool, mixing the oil and acid as completely as possi- ble, and taking as the true determination the highest temperature indicated by the thermometer, and maintained for more than a few seconds, ignoring any abnormal temperature which may be momentarily reached, but which the rapid fall on more perfect mixing shows to have been due merely to local action. The writer has recently adopted a device which secures a more perfect admixture of the oil and acid thaji is readily obtained by stirring with a thermometer alone. A piece of thin tin-plate, of the size shown in fig. 8, is bent into the form of a screw-paddle and fastened to the thermometer by passing the bulb of the latter through two longitudinal slits. The arrangement forms a simple and efficient mechanical stirrer, and by rotating the thermometer and attached paddle between the finger and thumb, a very complete agitation of the contents of the beaker can be obtained. Owing to the notable differ- ence in the rise of temperature caused by comparatively . slight variations in the mode of operat- ing, recorded figures obtained by Maumene's test have but little actual value. Hence it is desirable to compare a sample with one or more oils of known purity under exactly similar conditions. The figures in the table on page 56 show the kind of result to be expected from various oils, but, as just ex- plained, they must not be relied on too rigidly. From these figures it will be seen in the case of certain mix- tures, as, for instance, those of olive with cottonseed oil and rape with linseed oil, the rise of temperature on treatment with sul- phuric acid is not only a valuable test for the adulterant, but affords a useful means of forming an approximate estimate of the proportion of admixture. Thus, if the mean rise of temperature with rape oil be taken at 58, and that of linseed oil at 110 C., a sample giving a rise of 90, and known to consist of a mixture 56 TEMPERATURE-REACTIONS OF OILS. of the two, may reasonably be asserted to contain approximately 38'5 of rape, and 61*5 of linseed oil. 1 Kind of Oil. Rise of Temperature with Sulphuric Acid ; C. Maumene". Baynes. Dobb. Archbutt. Allen. Olive oil, .... 42 40 39-43 41-45 41-43 Almond oil, . . 52-54 35 Rape and colza oils, . 57-58 60-92 54-60 55-64 51-60 Arachis oil, 67 ... 47-60 Beechnut oil, 65 ... ... ... Sesame oil, 68 ... ... 66 Cottonseed oil ; crude, ... 84 6l" 70 67-69 ,, ; refined, . 77 ... 75-76 74-75 Poppyseed oil, . , 74 ... 86-88 Nigerseed oil, . 82 .. . 8l" Hempseed oil, 98" Walnut oil, 101 ... Linseed oil, . 103 104-124 ... ... 104-111 Cocoanut olein, , 26-27 Castor oil, 47" ... ... 46 ' 65 Lard oil, . 41 Tallow oil, 41-44 ... ISTeatsfoot oil, . ... 43' Horsefoot oil, , 51 ... ... ... "Whale oil ; northern, 91 ,, ; southern, ... 85-86 92" Porpoise oil, Seal oil, . ... ... ... 50* 92 African fish oil, 156" Shark -liver oil, 90" Codliver oil, . 102-103 lie" 113 Skateliver oil, 102 ... Menhaden oil, . ... ... 123-128 126" Sperm oil, , 51 45-47 Bottlenose oil, , ... ... ... 42 41-47 Oleic acid, . . . ... ... 37 38i In the case of linseed and some fish oils, the reaction with sulphuric acid is so violent as to render loss probable, unless the experiment be carefully conducted. In such cases, dilution of the sample with an equal weight of olive or lard oil will suffice to bring the reaction within bounds, (See Ellis, Jour, Soc. Chem, Ind., v., 150.) 1 110 - 58 = 52 ; or 0'52 C. (or about degree) in excess of 58 for every 1 per cent, of linseed oil present in the mixture. Hence the sample in question would contain 90-58 = 32 ; and 82 * 10 - 61 '5 percent; or, more vTt roughly, 32 x 2 = 64 per cent. ELA1DIN-KEACTION. 57 Elaidin-Reaction. When oleic acid is treated with a few bubbles of nitrogen trioxide (nitrous acid gas), it is gradually changed into the isomeric body elaidic acid, which is solid at ordinary temperatures. The glyceride of oleic acid undergoes a similar transformation with production of the solid isomer e 1 a i d i n, as also do such oils as consist of true olein in a state of approximate purity. On the contrary, the drying oils, which consist chiefly of linolein and its homologues, are not visibly affected by treatment with nitrous acid, and other oils, which probably consist of mixtures of olein with more or less linolein, give less solid products with nitrous acid than the approximately pure oleins. No explanation of the peculiar power of nitrous acid in isomer- ising oleic acid and olein appears to have been attempted, but it has been proved that the effect can be produced by the gas evolved on heating starch or arsenious oxide with nitric acid; by a mixture of a nitrite with a dilute acid ; by dissolving copper or mercury in nitric acid under a layer of the oil ; by agitating the oil with a freshly prepared solution of mercurous nitrate ; by the direct use of nitric acid of yellow or reddish colour, and therefore containing lower oxides of nitrogen; and lastly, by heating the oil with nitric acid until chemical action sets in and gaseous oxides of nitrogen are evolved. The proportion of the isomerising reagent requisite to produce the change and the influence of the proportion used on the rapidity and completeness of the reaction are almost unknown, and indeed no really scientific study of the formation of elaidic acid or elaidin appears to have been attempted. Of the various methods of obtaining the elaidin reaction, the following, due to P o u t e t, and the indications of which have been thoroughly studied by L. Archbutt, is one of the best in practice. It depends on the remarkable power of retaining nitrous acid possessed by a solution of mercurous nitrate. 1 c.c. of mercury should be dissolved in 12 c.c. of cold nitric acid of 1'42 specific gravity. 2 c.c. of the freshly-made deep green solution is then shaken in a wide-mouthed stoppered bottle with 50 c.c. of the oil to be tested, and the agitation repeated every ten minutes during two hours. When treated in this manner, oils consisting of approximately pure olein, or of mixtures of olein with the solid glycerides such as palmitin and stearin, give a solid product of greater or less consistency. Olive oil is remarkable for the canary or lemon -yellow colour and great firmness of the elaidin yielded by it. After twenty-four hours, the hardness of the product is such that it is impervious to, and sometimes rings when struck with, a glass rod, but this character is also possessed by the 58 COLOUR-REACTIONS OF OILS. elaidins yielded by arachis and lard oils. In making the elaidin test, it is important to note the time required to obtain a " solid " product, which will not move on shaking the bottle, as well as its ultimate consistency. Also the temperature should be kept as nearly as possible constant, or very erratic results may be obtained and comparison of different oils becomes impossible. The behaviour of the more important liquid fixed oils, when tested in the foregoing manner, is as follows : a. A solid, hard mass is yielded by olive, almond, arachis, lard, sperm, and sometimes neatsfoot oil. b. A product of the consistence of butter is given by neatsfoot, bottlenose, mustard, and sometimes by arachis, sperm, and rape oils. c. A pasty or buttery mass ivhich separates from a fluid portion is yielded by rape (mustard), sesame", cottonseed, sunflower, niger seed, codliver, seal, whale, and porpoise oils. d. Liquid products are yielded by linseed, hempseed, walnut, and other drying oils. L. Archbutt has also recently made some experiments with a new reagent, which is easily prepared and appears to possess certain advantages. It is made by passing a stream of sulphur dioxide (most readily obtained from a Boake's syphon) into nitric acid (specific gravity 1'420) kept cold. When substituted for the mercurous nitrate, Archbutt's reagent yields, after a time, solid products with rape and cottonseed oils, in addition to the oils ordinarily giving solid elaidins. The cottonseed and rape oil products are at first red, ' and that from olive oil a bright green, but these tints soon fade. In practice, the elaidin-test receives its most important applica- tion in the assay of olive oil, with which it gives a very charac- teristic reaction. The subject is further discussed in the sections treating of olive and rape oils. Colour-Reactions of Oils. Many fatty oils give, when treated with chemical reagents, products which are often strongly coloured. To a certain extent these colour-reactions are characteristic of the oils by which they are produced, and hence may be employed for their identification. It must be borne in mind, however, that the albuminous, resinous, and other foreign matters, on the presence of which the colour- reactions in most cases depend, are more or less completely removed or modified by the process employed for refining the oil. Hence, considerable variation is observed in the behaviour of different samples of oil with the same reagent, and the value of the . COLOUR-REACTIONS OF OILS. 59 reactions is still further reduced by the modifications produced by the presence of free fatty acids in the oils. Still less are the indications to be trusted when mixed oils are examined. Not- withstanding these drawbacks, colour-tests, when carefully applied, are often capable of furnishing valuable information, and some- times render the positive identification of an oil, or its detection in a mixture, possible, when no other means are available. Colour-tests for oils have been devised by Calvert and various other observers, the most complete series of observations" being those of Chateau, published in 186 1. 1 Many of those proppsed have very little value. Certain of them are useful as special tests, and are described in the sections treating of the oils for the detection of which they are of use. The reactions with strong sulphuric and nitric acid have a more general value, and require a fuller description. In employing colour-tests for oils, it is very desirable to examine specimens of oils of known purity side by side with the sample, instead of trusting too implicitly to the reactions described. SULPHURIC ACID COLOUR-TEST. Of colour-tests, that with concentrated sulphuric acid is one of the most valuable and readily applied. It has been recommended by various chemists, some of whom employ several different strengths of acid, whilst others modify the proportion, that used by Chateau being in excess of the amount desirable. With care, the violet colour produced by the fish-liver oils is highly characteristic, as also are some of the other reactions. The table on next page shows the effect produced on placing a drop or two of sulphuric acid in the centre of about twenty drops of the oil, and observing the colour both before and* after stirring. The reactions described include those produced by the generality of hydro-carbon oils. As already stated, the colours produced by different samples of the same kind of oil are liable to considerable variation. The reactions of the oils with concentrated sulphuric acid are in some cases complicated or rendered indistinct by the charring action exerted by the reagent. , This may be avoided by dissolv- ing one drop of the oil in twenty drops of carbon disulphide, and agitating the solution with a drop of strong sulphuric acid. Whale oil when thus treated gives a fine violet coloration, quickly changing to brown, whereas with sulphuric acid alone 1 Chateau's tests, with some modifications by J. Muter, are described in Spon's Encyclopaedia of the Industrial Arts, &c., p. 1472 et seq. The writer published them in a tabular form in the first edition of this work, but does not consider them of sufficient value to warrant their reproduction. 60 SULPHURIC ACID COLOUR- TEST. a mere red or reddish-brown colour changing to brown or black is obtained. Oil. 1 or 2. drops of strong Sulphuric Acid to 20 of the Oil. Before Stirring. After Stirring. Vegetable Oils Olive oil, , Yellow, ^ green, or pale Light brown, or olive brown*. green. Almond oil, , Earthnut oil, . Rape oil, crude, Colourless, or yellow. Greyish-yellow to orange. Green, with brown rings. Dark yellow, olive, or brown. Greenish, or reddish -brown. Bright green, turning brownish. refined, . Yellow, with red or brown Brown. rings. Mustard oil, . Dark yellow, with orange Reddish-brown. streaks. Cottonseed oil, crude Very bright red. Dark red, nearly black. refined Reddish- brown. Dark reddish-brown. Nigerseed oil, . Yellow, with brown clot. Reddish or greenish-brown. Poppyseed oil, Yellow spot, with orange Olive or reddish-brown. streaks or rings. Linseed oil, raw, Hard brown or greenish- Mottled, dark brown. brown clot. ~ : boiled, . Hard brown clot. Mottled, dark brown. Castor oil, Yellow to pale brown. Nearly colourless, or pale brown. Animal Oils Lard oil, Greenish yellow, or brown- Mottled or dirty brown. ish, with brown streaks. Tallow oil, , Yellow spot, with pink Orange red. streaks. Whale oil, Red, turning violet. Brownish-red, turning brown or black. Seal oil, , Orange spot, with purple Bright red, changing to streaks. mottled brown. Codliver oil, * . Dark red spot, with purple Purple, changing to dark streaks. brown. Sperm oil, * . Pure brown spot, with faint Purple, changing to reddish yellow ring. or dark brown. Hydrocarbon Oils Petroleum lubricating Brown. Dark brown, with blue oil, fluorescence. Shale lubricating oil, Dark reddish-brown. Reddish-brown, with blue fluorescence. Rosin oil, brown, Bright mahogany brown. Dark brown, with purple fluorescence. pale, Mahogany brown. Red-brown, with purple fluorescence. NITRIC ACID COLOUR-TESTS. The colour-reactions of the fixed oils with nitric acid have been described by various observers, but unfortunately hardly any two of these apply the test in the same manner. Omitting minor variations, the following modes of procedure may be adopted : a. Hauchcorne's test as extended by Stoddart. Agitate to- gether from 3 to 5 measures of the oil with 1 of nitric NITRIC ACID COLOUR-TESTS. 61 acid of 1'32 specific gravity. Heat the tube for five minutes in boiling water; then take it out and allow it to stand. Observe the colour of the oil from time to time up to an hour and a half. &. Massie's test. Agitate 3 measures of the oil for two minutes with 1 measure of colourless nitric acid of 1'40 specific gravity. Observe the colour of the oil after separation. c. Gldssner's test. Pour the oil cautiously into an equal measure of red fuming nitric acid, and observe the colour of the oil and of the zone which forms between the oil and the acid liquid. When tested respectively in the foregoing manners, the follow- ing reactions are said to be produced : Oil. a. b. c. Olive oil, . Colourless or tran- Colourless, yellow- Broad bright sient yellow. ish, or greenish. bluish-green zone. Almond oil, Nearly colourless, changing to solid white mass. Colourless, or slight- ly greenish. Narrow, bright green zone ; oil . flocculent or opaque. Arachis oil, . ... Reddish. ... Peach-kernel oil ... Immediate red lini- ... ment. Rape oil, . Red or orange. Reddish or orange. Brown-red ; green- ish below. Sesame oil, ... Yellowish or orange. ... Cottonseed oil, . Red or orange. Brown, or brownish- ... red. Nigerseed oil, . Red or orange. ... ... Linseed oil, Red or orange. Red or orange. Green zone ; oil red. Poppyseed oil, . ... Reddish. Dark-green zone; oil pink. Hempseed oil, ... Brownish-red. ... Castor oil, Transient yellow. Yellowish or orange. ... Lard oil, , Colourless or tran- ... ... sient yellow. Whale oil, Dark red. ... ... Seal oil, . Dark red. ... ... Codliver oil, ... ... Brown-red. Rosin oil, . . Reddish-brown. ... ... Mineral oil, Dark red. ... Methods in which the nitric acid test is specially applied to the detection of adulterations of olive oil are described on page 100. 62 CLASSIFICATION OF FATTY OILS, CLASSIFICATION OF FATTY OILS, &c, In studying the characters of fixed oils, and identifying oils of unknown nature, valuable assistance is obtained from a suitable arrangement of the oils in classes or groups. Such a classification can be made on several principles, but the one adopted by the writer, and the convenience of which has been established by experience, is based on a joint consideration of their origin, physical characters, and chemical constitution. Thus it is not found desirable, in practice, to place in the same class an oil of animal origin (e.g., lard oil) with others of vegetable production (e.g., almond and olive oils), although in its physical and chemical characters it may closely resemble them. Similarly, the oils from fish and marine mammals are advantageously arranged in a separate class from the oils of terrestrial animals. It is evident that the melting point of an oil is chiefly dependent on its chemical composition, oils of which palmitin and stearin are the leading constituents being solid at ordinary tempera- tures, while in the liquid oils olein or linolein predominates. The specific gravity of the fixed oils is also closely dependent on their chemical constitution, and this becomes more evident when the determination is made at a temperature at which all oils are liquid. Under these circumstances, the waxes are the least dense, then follow the molten fats, the non-drying oils, the drying oils, and lastly, castor oil, which is the densest of all. The figures relating to specific gravities in the following tables giye the range of density commonly observed in various oils as usually met with in commerce, and the same remark refers to the melting points. 1 On the other hand, specimens of genuine "oils of certain 'kinds are occasionally met with having densities and melting points outside the limits given in the tables, and this is especially liable to occur in. the case of oils which have been long kept, or which have undergone some treatment resulting in their oxidation (see "Blown oils," p. 52). Similarly, the saponification-equivalents are those observed up to the present time, but further experience in such determinations may necessitate revision of certain 'of the figures given, especially in the case of oils of which only a small number of samples have hitherto been examined. 1 The specific gravities of the fluid fixed oils are given for the ordinary tem- perature only ; but in the case of the solid fats and waxes their densities in the molten state at the temperature of boiling water are also stated. The density of many fluid oils at the boiling point of water, and their rates of expansion, are given on p. 17 et seq. OLIVE OIL GROUP. 63 r ._ fi| o o g ' r^ .22 > .3 - - ~ . it>o -*e c- i if l*& |Ji r* 3 o3.2 45:3 5 A d ^ O ak an Pit! i i|H -3^ M w -gll^ll 1|^I^ .^Pll IS bco . ^^ S 1 ^ ri'pnS "^ rt 2jn ^ oo sls.1 c c3 c 11*1 L 5 I a I SJ PQ filial o> o> d ^ g ^5 P d, d > PH '^ i^llljl i C4 - j 'S "3 !> Q O r CB > ^5 T!i ^ aponiflcation Equivalent. s 1 *i CO I I 3 3 * o + I *" F-5 ^ * T 3 5' 5 5-2 3 OS OS OS OS OS OS 3 5 OS ^ ^-T*O "o "d j^ "g^ 1 if :< ^ a o 64 COTTONSEED OIL GEOUP. oa m ao _(-; ^ rt O -"t- O o S * & ?l|il fl ^ 60 V^'a c^ rH g -3 O ?o^'2 s!S|J p ^>-i 388K i l^^.^ NISI 2 I o 2-S ^ & ^ ^ *S C 05 *0 _I M $ So rdn g 2.t3 o ^ g^ ^ ^^-s^ 5 tsii Itlll ra ^n ^ 9 fil ujj . ^ & 1 S 2 o ^ Othe Com II a in f 1.,-s ii n n ll. "S^ d .-S p^'d o ii ll aT^ m i5 'S It i S, lfi o 3 I I LINSEED OIL GROUP. 65 HI 3 -t-5 -*J ^ 03 * " I- r o H scbc - 0) fl i - r .s? la i i lili 3gS a "'8 gs & b_: E-s-s III g&3 i i 3 3 S 3 i i 3 3 ! I I I i 1 H fc VOL. II. 66 CASTOR OIL GROUP. PALM OIL GROUP. 67 ll CO. CO 3 S i s s m S : s, 3 68 COCOANUT OIL GROUP. ^ S ' 8 Q Si a r^^ ers, &c. fac . ? P II -i > * c S -is* fei ti 1 1 O> ^i (C *a I 1 1 s_ "* 55 > *- Qi g ,iai|$iK II M !, S II I' 1 fc O i s ^-s B: &3 a!Sgs! - fe S "3 S -^ i ,g 3 S3 bO< t) 3 2 a a i, -SS^s S-3 * i s r5 S S * 3 t-. O Q 2 2 C^ i-i O ** 2222 5 52 * bo III 8^ 3 a" LAUD OIL GROUP. 69 tfS a-S 2 18 5 3 1.s| -243 g O ^ 1.11 il! Jlfr I; a : o p-5r= -1.81 K C O ifs II If I II P ^ * -' ! 70 TALLOW GROUP. rs, c. g white to cy of lard ariable in asant smell. tlrnn lard. ntains lime. ," page 69. owish-brown. ble quantity rin. Takes r. :i|g^H ip }iw . J^iJU S cit>-s>|?l|19 .S5.g.S5 H'111!fld* fl l $3 la S * 43 S 58- a^ !/! o;sfcco k- cii &l S^stw-S^S ^^ o o-gPOoo 0^ ^n> Prepared by incorporating various purified fats with milk and salt. See p. 151. The melting point is high. Closely resembles hard tal- low or suet. Must not be confused with stearic ac. Grey, .brown, or black ; veiy variable ; often contains wool-fat. I! 3 3 So a i p WHALE OIL GROUP. 71 d o I a ll : 'S S I m '8 jd' '3 53 *s|- >^ o *0 >^fl 0^3 O *^s cc *[3 S*8 11^ 85 g ^5 g,a^ &Jg. . ll s|^^ "FH r^l o r & r T3 S o 43 .-s g s :tia ^_o^ g-| rt . rt ^ , II |: G b |1 ^ S| F 1* w qj ^ ^O "4 c:g d CQ a 5 ^ o- l^^S"^ 88*>.a o 5/rt -^ S S *s a -M o> Ml-il ! *M o .^ ^Hjl 5-1 S S * ^ S g SH fl^ o g^ ^ g bC P- PH.+- I.^^^ MS- 4 ' 8 %' - s s g^ >-S3 l-a I H gs^^l " .^, a Ml! 3) O C3 O IFf ^*tt p -H 1 ^ i eS o3 1 lj 5 o 03 ^f|||o^|| 1 | * 5 - af g S, "" J3 * 3 5 | S iirri-g|llj p s 1 i&isiSiijsii ^ c ^ 05 CQ CO ^ 1^ CC ^gi --0^ A-g rf i-g^ i|g ^^S p,^P( ^03^ ^0303 E a * ^54 1 S ft s -tf| -2 a x " -2 S .s" x 1 7, *' ^* -Ss p 1 s as5^adB *Sa o o o K h g -rtB I ! I j-' ; 00^ c 1 -< >>*u a O 2 o Q a3 o;pos 1 W -M O'kj.o ^OtT? * > < c? ?i o ** iL 1 "* O ' M ^-^ |l ^f|| ' s-l s lll fa rd O ^w o*i J o . n IP 00 S* 1 s S s : 2 O5 CO 00 1* ^ ai oo 11 1 S 9 | eg 3 222 : : 1 2 o 2 o C?3 2 00 00 00 p g 1 s 22: : * o IM OJ 3 S g , ource of Wax. iljill iITL " Oa32' G> 'n 1 8 rf ^ 1 ^? |?ll-s-e illlil ji$ ffifllll O H OH W fa X " of >T . 1 1 S 11 i l! 1 0> "7 * -gi CO CO (I, O ! JW 74 FOREIGN MATTERS IN FIXED OILS. EXAMINATION OF FIXED OILS FOR FOREIGN MATTERS. By the term foreign matters used in this connection it is not intended to signify the traces of cholesterin, chlorophyll, gummy and albuminous matters, colouring matters, &c., which are natural constituents of the animal and vegetable fixed oils and fats; but the term is applied to large proportions of free fatty acids and to intentional admixtures of resin, soaps, hydro- carbon oils, water, and mineral matter. These bodies are often added to oils, either as adulterants or with the view of giving them some special property. When used in small quantity the detection of some of them is attended with 'considerable difficulty. In the case of butter, lard, and palm oil, more or less water, curd, salt, &c., are not unfrequently present. The methods of detecting and estimating such of these admixtures as are peculiar to each of these are described in the sections devoted to the fats in question. A fluid oil, if clear, may be regarded as free from such extraneous matters, and their presence in a solid fat may be at once detected by melting the sample. If an opaque or opales- cent oil result, or one containing visible particles of suspended matter or globules of water, it should be purified from these by filtration through dry paper before proceeding to search for resin, fatty acids, soap, or hydrocarbon oils. Soap is sometimes directly added to an oil, but its presence is more frequently due to the use of alkali employed to increase the density and viscosity of the article. Soap is readily detected by dissolving the oil in about three times its measure of ether or freshly-distilled carbon disulphide, adding a little water, and agitating the whole thoroughly in a tapped separator. The soap will dissolve in the water, while all other foreign matters will dissolve, together with the oil, in the ether or carbon disulphide employed, and may be recovered therefrom by distilling off the solvent. The soap may be determined by evaporating the aqueous liquid and weighing the residue after drying at 100 C. The proportion of soap may also be inferred from the amount of carbonate of alkali- metal left after igniting the oil. INSOLUBLE SOAPS of aluminium and certain of the heavy metals are not unfrequently present in oils, waste greases, and pharma- ceutical preparations (" oleates "). They differ from the soaps of the alkali-metals by being insoluble in water, but they are soluble in many cases in ether, petroleum spirit, &c. They may be decomposed by agitating the mixture with dilute sulphuric acid, FREE ACID IN OILS. 75 when the acid liquid will contain the metal of the soap x and a corresponding quantity of free fatty acid will be formed, and will be dissolved by the oily layer. Hence, in cases where it is desired to ascertain the proportion of free fatty acids originally existent in the oil, a titration with alkali should be made both before and after shaking with dilute acid. The difference between the two estimations represents the fatty acid produced by the treatment. Free Acid in Oils. Commercial oils and fats very frequently contain notable proportions of free acid, which may either be mineral acid, as a result of incomplete separation after refining, or free fatty acid resulting from unskilful refining or from the natural decomposition of the oil. MINERAL ACIDS are only accidentally present in fixed oils, and usually exist in very small proportions. Very small quantities are highly objectionable in oil intended for lubricating, but are harm- less when the article is to be used for soapmaking. Mineral acids may be readily recognised by agitating the oil with warm water, separating the aqueous liquid, and testing it with a solution of methyl-orange, which will give an orange or red coloration if any mineral acid be present. The nature of the mineral acid, which is most commonly sulphuric, can then be ascertained by testing the aqueous liquid with barium chloride, silver nitrate, and other appro- priate reagents. Oils which, from over-treatment with acid during refining, contain a conjugated acid or sulphonate, must be boiled with water for some time, in order to decompose the compound. FREE FATTY ACIDS are often normally present in oils (see page 28), and in some (e.g., olive and palm oils) may exist in very large proportion. Free oleic acid is largely used as a lubricant in wool- spinning, and free palmitic and stearic acids are employed for making candles and night-lights. All three acids are used for soapmaking. The fatty acids differ from neutral fats or glycerides in having an acid reaction in alcoholic solution ; in being converted into soaps by treatment with alkaline carbonates or borax ; and in being freely soluble in alcohol, even if the latter be somewhat dilute. The simple detection of free fatty acid in an oil may be effected by shaking the oil with alcohol, and adding an alcoholic solution of lead acetate to the spirituous liquid. If a notable quantity of free fatty acid be present, a white precipitate will result. Eesin and soap produce the same reaction. A more delicate mode of detecting free fatty acid in an oil, and one which can be applied to the accurate determination of the quantity present, consists in titrating the alcoholic solution with standard caustic alkali, using phenol-phthalein as an indicator. 76 DETERMINATION OF FREE FATTY ACIDS. The method was first proposed by Hausamann, and test- analyses by G r o g e r of artificial mixtures of known composition have fully established its accuracy. The following mode of operat- ing is applicable to the determination of free fatty acids in oils in whatever proportion they may be present : Some methylated spirit is purified by redistillation with a little caustic soda, a little alcoholic solution of phenol-phthalein added, and then dilute caustic soda added drop by drop till the liquid retains a faint pink colour after shaking, this preliminary treatment being intended to secure the absence of any trace of free acid. An accurately weighed quantity of the sample, varying from 5 grammes of fatty acid to 50 grammes of an ordinary oil, is then introduced into a flask or bottle furnished with a glass stopper. From 50 to 100 c.c. of the neutralised spirit is then added and raised to the boiling point, either by immersing the bottle in hot water or by direct application of a flame. The contents are thoroughly agitated to effect as complete a solution of the fatty acids as possible. If the sample of oil be wholly free from acici, the pink colour of the spirit will remain unchanged, but otherwise it will have dis- appeared. In the latter case, a semi-normal solution of caustic soda ( = 20'0 grammes of NaHO per litre) is gradually added to the warm contents of the flask, which is thoroughly agitated after each addition. The addition is continued until a pink coloration is obtained, which persists after vigorous shaking. The reaction is as well defined, and the neutralisation-point as easy to perceive, as in the titration of mineral acids ; but owing to the very high com- bining weights of the fatty acids, great care is necessary. 1 Thus, 1 c.c. of normal caustic alkali used corresponds to 0'256 of free palmitic, 0'284 of free stearic, or 0*282 gramme of free oleic acid in the quantity of the sample examined. For determining small proportions of free acid, it is desirable to employ decinormal alkali, while in the case of samples containing much free acid, the 1 The method described in the text combines the advantageous points of the two methods of operating recommended by L. Archbutt (Analyst, ix. 170) and W. H. Deer ing (Jour. Soc. Chem. Ind., iii. 541), both of which chemists have had considerable experience of the process. It has also been extensively employed in the writer's laboratory, where it has been found that there is no practical difference between the results obtained by titrating with aqueous alkali and those given with alcoholic alkali. It might be supposed that the proportion of free fatty acid found by the process would be liable to be in excess of the true amount present, owing to the alkali having a tendency to saponify and be neutralised by the neutral oil ; but such a suspicion is negatived by the fact that an oil once freed from acid by the process of titra- tion shows no trace of free acid when again treated. RESIN IN OILS. 77 quantity taken for the assay should be correspondingly reduced. In assaying palm oil, which is itself often of a red colour, the titra- tion may still be made by employing 5 grammes of the sample and 20 c.c. of spirit, the flask being placed on a white surface. Any rosin acids present in the sample will be estimated by the above process as free fatty acids. Their separation from the latter is described on page 78. Free mineral acids will affect the accuracy of the results unless duly allowed for, or previously sepa- rated by repeatedly agitating the oil with water. The presence of soap and hydrocarbon oils does not interfere with the process. The foregoing method of estimating free fatty acids by titra- tion may be advantageously supplemented by a gravimetric deter- mination. This is effected by separating the resultant alcoholic liquid from the oil, evaporating off the alcohol, and adding water. This solution is then agitated with a little petroleum spirit (not ether) to dissolve suspended oil, the aqueous liquid separated, and the fatty acid liberated from the soap solution by adding dilute sulphuric acid. On agitating with ether, separating, and evaporating the ethereal solution to dryness, the fatty acids can be weighed. This plan should always be adopted in cases where the presence of resin acids is suspected. In their absence, the deter- mination should be fairly concordant with the result of the titration. Soap, if present, must be previously separated as described on page 74. Free mineral acids and hydrocarbon oils do not interfere. An areometrical method of estimating the proportion of free acid naturally present in olive oil is described on page 97. Resin is an addition to fixed oils the detection of which is attended with some difficulty, while its determination is trouble- some and occasionally impossible. Common rosin or colophony, the chemical and physical characters of which are described in a special section (see " Resins "), is added to oils to impart certain properties, but its employment often wholly unsuits them for their intended purposes. One of the simplest methods of detecting rosin in oils is based on the brown colour it imparts to caustic soda. The original sample is saponified, the alcohol boiled off, and the liquid treated with sufficient caustic soda ley to cause precipitation of the soap. The solution, separated from the soap by decantation or filtration through glass-wool, is found to have a dark brown colour if resin were present. The same reaction serves for the recognition of rosin in soap, any previous saponifi cation being of course superfluous. The above method of treatment with caustic soda solution may also be applied to the mixture of fatty and resin acids separated from the oil in the manner described in the table (page 87). The dissolved 78 RESIN IN OILS. resin may be recovered from the alkaline liquid by acidulating it with hydrochloric acid, when a precipitate of resinous odour will be formed. The resin may be isolated by agitating with ether and evaporating the ethereal layer to dryness. It may then be identified by its physical and sensible characters. In the absence of free fatty acids, resin may be isolated from fixed oils by agitating the sample with moderately strong alcohol, separating the spirituous solution and evaporating it to dryness. It may also be isolated, and approximately estimated, by titrating the alcoholic solution of the sample with caustic alkali and phenol-phthalein as described on page 76. As the several acids of which ordinary colophony is essentially composed are not present in constant proportions, the neutralising power of resin is variable, ranging from 0'330 to 0*290 gramme of colophony for 1 c.c. of normal alkali employed. The rosin subsequently extracted from the acidulated aqueous liquid, and left on evaporating the ethereal solution to dryness, is readily recognisable by the taste and smell on heating, and in favourable cases has the physical characters of rosin. In the last method of operating, the resin is obtained in admix- ture with any free fatty acids the sample of oil may have contained. These modify the physical properties of the extracted resin very materially, and render the method useless for quantitative purposes. In such cases, if there is sufficient material for the purpose, a good indication of the relative proportions of fatty and resin acids in the mixture may be obtained by observing the density at the temperature of boiling water, as described on page 1 6. As, however, rosin varies considerably in density and the fatty acids derived from various oils exhibit similar variations, the method furnishes but very rough results unless the source of the fatty acids be definitely known. A method of separating fatty from resin acids based on the solubility of the barium salts of the latter in alcohol has been de- vised by J e a n and modified by K e m o n t. Similarly, B a r f o e d (Zeits. Anal. Chem., xiv. 20, and Jour. Chem. Soc., xxix. 773) treats the sodium salts with ether-alcohol, which dissolves chiefly the resin acids. 1 These methods have been to a great extent superseded by a process due to T. S. Gladding (Amer. Chem. Jour., iii. No. 6; Chem. News, xlv. 159), who has described a method of separating fatty and resin acids which is based on the ready solubility of silver resinate in ether, and the almost complete in- solubility of silver oleate, &c., in the same menstruum, even in presence of a small quantity of alcohol. About 1 gramme of the mixed fatty and resin acids is dissolved in 35 to 40 c.c. of 1 A modification of Barfoed's method is described in the section on ' ' Fatty Acids, " GLADDING S RESIN METHOD. 79 absolute alcohol. A drop of phenol-phthalein solution is added, and then a saturated solution of caustic potash in absolute alcohol is dropped in till the liquid acquires a permanent pink tint, indicating the neutralisation of the acids. Another drop or two of alkali solution should then be added and the flask heated for ten minutes to ensure the saponification of any trace of neutral fat. The liquid is then cooled and poured into a stoppered glass cylinder, graduated to 250 c.c., and furnished with a tap in the side (fig. 9). 1 Sufficient dry ether is next added to bring the volume of the liquid to exactly 200 c.c., and then about 1 gramme of neutral silver nitrate is added in fine powder. The contents of the cylinder are thoroughly agitated for ten minutes, or until the precipitated silver oleate coagulates and leaves the liquid clear. 150 c.c ( = f of the whole), or some other exactly measured quantity of the ethereal liquid, is then run off" into a tapped separator (fig. 10) in which it is shaken with a small additional quantity of silver nitrate, to ensure that the whole of the fatty acids have been precipitated. If any floc- culent precipitate be produced, the liquid should be returned to the cylinder, shaken with more silver nitrate, and a known volume again removed by means of the tap. The measured ethereal liquid in the separator is then vigorously shaken with about 10 c.c. of hydrochloric acid and 20 of water, whereby silver chloride is precipitated and the liberated resin acids remain dissolved in the ethereal layer. This is separated from the aqueous liquid, evaporated to dryness, and the Fig- 9 - residue weighed. Gladding directs that the weight obtained shall be corrected by subtracting 2 '35 milligrammes for each 10 c.c. of ethereal liquid removed by the tap ( = 0'0352 gramme for 150 c.c.), this being an allowance for the slight solubility of silver oleate in the ethereal liquid. Alder Wright and Thompson find, however, that Gladding's correction is excessive when either stearic or oleic acid is alone present (with resin acids), though approximately accurate for mixtures of the two. They further find that the correction is insufficient in the case of fatty acids of other kinds, and especially with the acids from castor oil. The following results were obtained by Wright and Thompson : 1 This apparatus was devised by J. Muter and is obtainable from J. Orme & Co., Barbican, E.G. 80 DETECTION OF HYDROCARBON OILS. Milligrammes of Fatty Acids in 10 c.c. of Solvent. Maximum. Minimum. Average. Pure oleic acid, 1-5 0-9 1-20 Pure stearic acid, 1-6 0-8 I'M Mixed stearic and oleic acids, 2-2 1-8 1-91 Acids from cottonseed oil, 3-4 2-0 2-69 Acids from castor oil, 6-2 4-9 5-39 Acids from cocoanut oil, 2-3 1-3 1-80 Acids from linseed oil (Allen), ... 2-31 Gladding's method is fairly simple and gives very good results, when the nature of the fatty acids is known. In the case of soap, 2 grammes of the sample can be at once dissolved in 40 c.c. of hot absolute alcohol, and the solution made up with ether to 200 c.c. Gladding employs half these quantities. Hydrocarbon Oils. The extensive production of various hydrocarbon oils suitable for lubricating purposes, together with their low price, has resulted in their being largely employed for the adulteration of animal and vegetable oils. The hydrocarbons most commonly employed are : 1. Oils produced from petroleum and by the distillation of bituminous shale. (See " Mineral Lubricating Oils." 2. Oil produced by the distillation of common rosin, having the nature and properties detailed in the section on " Rosin Oil." 3. Neutral coal oil; being the portion of the products of the distillation of coal-tar boiling above 170 C., and freed from phenoloid bodies by treatment with soda. 4. Solid paraffin, employed for the adulteration of beeswax and spermaceti, and used in admixture with stearic acid for making candles. The presence of hydrocarbon oils in fatty oils is detected by the altered density of the sample, which is decreased by oils of the first class, and increased by rosin and coal-tar oils ; by the dimin- ished flashing and boiling point of the sample as com- pared with genuine oil of the same sort ; by the fluorescent characters of the hydrocarbon oils of the first two classes ; and by the incomplete saponification of the oil by alkalies. The taste of the oil and its odour on heating are also valuable indications. Specific gravity is a character of some little value for detecting and approximately estimating hydrocarbon oils in fat oils, but in practice the indications obtained are apt to be rendered valueless by the employment of a mixture of mineral and rosin oil of the same density as the oil to be adulterated. DETECTION OF FLUORE The tendency of an admixture of hydrocarbon oil with a fat oil is to reduce the flashing and boiling point of the sample, and in some cases a distinct separation may be effected by frac- tional distillation. Fluorescence is a character of considerable value for de- tecting the presence of hydrocarbon oils in fat oils. If undoubtedly fluorescent, an oil certainly contains an admixture of some hydro- carbon, 1 but the converse is not strictly true, as the fluorescence of some varieties of mineral oil can be destroyed by chemical treat- ment, and in other cases fluorescence is wholly wanting. Still, by far the larger number of hydrocarbon oils employed for lubricating purposes are strongly fluorescent, and the remainder usually become so on treatment with an equal measure of strong sulphuric acid. If strongly marked, the fluorescence of a hydrocarbon oil may be observed in presence of a very large proportion of fixed oil ; but if any doubt exist, the hydrocarbon should be isolated in the manner described on page 83. As' a rule, the fluorescence may be seen by holding a test-tube filled with the oil in a vertical position in front of a window, when a bluish " bloom " will be perceived on looking at the sides of the test-tube from above. A better method is to lay a glass rod, previously dipped in the oil, down on a table in front of a window, so that the oily end of the rod shall project over the edge, and be seen against the dark background of the floor. Another excellent plan is to make a thick streak of the oil on a piece of black marble, or glass smoked at the back, 2 and to place the streaked surface in a horizontal position in front of, and at right angles to, a well-lighted window. Examined in this manner, very slight fluorescence is readily perceptible. If at all turbid, the oil should be filtered before applying the test, as the reflection of light from minute particles is apt to be mistaken' for true fluores- cence. In some cases it is desirable to dilute the oil with ether, to which an exceedingly small amount of mineral oil is sufficient to impart a strong blue fluorescence. 3 It must be borne in mind that the fluorescence is not perceptible 1 L. Archbutt states that genuine rape oil sometimes exhibits fluorescence. This may be due .to the accidental presence of an insignificant proportion of mineral oil, as fluorescence becomes stronger with dilution of the fluorescent substance. 2 Either of these is infinitely superior to the polished tinplate usually recom- mended. In short, the background should be black, not white. See also vol. i. p. 15. 3 This fact is of service for the examination of very dark oils, as by solution in ether the colour is reduced, and so causes less trouble without the intensity of the fluorescence being correspondingly decreased. If the colour of the oil VOL. II. F 82 HYDROCAKBON OILS IX FAT OILS. by gaslight, but may be brought out by burning a piece of mag- nesium ribbon in the proper position. The quantitative analysis of mixtures of fat oils with hydro- carbon oils was, till a few years ago, very uncertain, the published methods professing to solve the problem being for the most part of very limited applicability, and in some cases wholly untrust- worthy. a. When the hydrocarbon oil in admixture happens to be of comparatively low boiling point, it may often be driven off from the sample by exposing it to a temperature of 120 C. till it ceases to lose weight. The estimation thus effected is generally too low, and in many cases is quite untrustworthy. By previously saponify- ing the oil and employing a higher temperature (160 C.) more complete volatilisation is secured ; but if this trouble be worth taking it is better to make an accurate separation of the hydro- carbons as described below. b. The following method is the only one hitherto published which combines the necessary qualifications of rapidity, certainty, tolerable accuracy, and pretty general applicability, and at the same time enables the hydrocarbon oils to be obtained in a condition fit for further examination. It has been thoroughly studied and largely used by the author, and is based on the following principles : The hydrocarbon oils, of which the determination is desired, agree in the general property of being unaffected by alkalies, whereas all animal and vegetable oils and waxes undergo the de- composition known as " saponification " (page 29). If the alkali employed for the saponification be potash or soda, the resultant soap is soluble in water. The hydrocarbon oils, though insoluble in water and unaffected chemically by alkalies, dissolve with greater or less facility in concentrated solutions of soap, and are very im- perfectly separated even on dilution. They may, however, be dis- solved out from the dry soap, mechanically divided by admixture with sand, by the use of suitable solvents, such as ether, chloroform, carbon disulphide, benzene, or petroleum spirit. In some cases, a very perfect separation is obtainable by such means, but in others not only the hydrocarbon oil but a considerable quantity of soap passes into solution, especially if the solvent be employed at a tempera- be very dark, as in the case of a dark Gallipoli or brown rape oil, it is neces- sary to refine it before applying the above test This may be effected by agitating the sample successively with small proportions of concentrated sul- phuric acid, water, and solution of carbonate of sodium, and subsequently filtering the clarified oil. In some cases decolorisation may be effected by warming the oil and agitating it with freshly-burnt animal charcoal, the liquid being subsequently filtered. SEPARATION OF HYDROCARBONS FROM FATTY OILS. 83 ture approaching its boiling point. This tendency of the soap to undergo solution may be wholly avoided by treating its aqueous solution with the solvent, instead of exhausting the dry soap. The following are the details of the manipulation : Five grammes weight of the sample of oil is saponified by alcoholic alkali in the manner directed on page 35. The solution of the resultant soap, freed from alcohol, 1 is transferred to a pear-shaped or cylindrical separator (fig. 10) of about 200 c.c. capacity, fur- nished with a tap below and a stopper at the top. The tube below the tap should be ground or filed off obliquely, so as to prevent any liquid from remaining in it. The liquid is then diluted with water till it measures from 70 to 100 c.c. From 50 to 60 c.c. of ether should next be added, the stopper inserted, and the whole thoroughly shaken and allowed to rest for a few minutes. As a rule, the liquid will readily separate into two well-defined layers, the lower one brownish and consisting of the aqueous solution of soap, while the upper layer consists of ether contain- ing any hydrocarbon oil in solution. Sometimes separation into layers does not occur readily, the liquid remaining apparently homogeneous, or assum- Fig. 10. ing a gelatinous consistency. In such cases, separation may be induced by thoroughly cooling the contents of the separator ; by adding caustic potash solution ; by adding more ether and re- agitating ; or, if all these means fail, a few cubic centimetres of alcohol may be added, and a gentle rotatory movement imparted to the liquid, avoiding complete admixture, when a very rapid separa- tion of the ethereal layer almost invariably occurs. Separation being effected, the aqueous liquid is run through the tap into a beaker. About 10 c.c. of water and a few drops of caustic alkali solution are added to the ether which remains in the separa- tor, and the whole agitated. The washings are then run off in their turn, and after repeating the treatment with water, which is removed by the tap as before, the ethereal solution is poured off through the mouth into a tared flask. The aqueous liquid and washings are then returned to the separator, and agitated with a fresh quantity of ether, which is washed and poured into the flask as before. The agitation of the soap solution is repeated once more, when the extraction of the hydrocarbon oil may be relied on as being complete. As a rule, the ethereal solution obtained will be strongly fluorescent. The flask containing the ethereal solution 1 If the alcohol be completely eliminated the ethereal layer is apt not to separate from the aqueous liquid at the next stage. 84 HYDROCARBON OILS IN FAT OILS, of the hydrocarbon oil is then attached to a condensing arrange- ment, and the greater part of the ether distilled off by immersing the flask in a metallic vessel containing water kept boiling by a flame. When distillation ceases the condenser is detached and the flask placed on the top of the water-oven, where the rest of ether is soon dissipated. Sometimes the hydrocarbon oil will contain globules of water, in which case the flask should be held horizontally, and rotated rapidly so as to spread the oil over the sides in a very thin layer, and facilitate the evaporation of the water. When no more water is visible and the smell of ether is scarcely perceptible, the flask is placed on its side in the water- oven for ten or fifteen minutes and weighed, 1 when the increase of weight over the original tare gives the amount of hydrocarbon oil extracted. Prolonged heating should be avoided, as many classes of hydrocarbon oils used for adulterating fixed oils are sensibly volatile at 100 C. This is notably the case with coal-tar oil, and hence, in analysing mixtures containing it, the heating in the water-oven should be wholly dispensed with. With rosin oil, paraffin wax, and the denser mineral oils there is but little danger of loss by volatilisation at 100 C. The foregoing process has been extensively employed by the author, and has been proved to be accurate on numerous mixtures of fatty oils with hydrocarbon oils. The results obtained are correct to within about 1 per cent, in all ordinary cases. 2 In cases' where extreme accuracy is desired, it is necessary to remem- ber that most, if not all, animal and vegetable oils contain traces of matter wholly unacted on by alkalies. In certain cases, as butter and codliver oil, this consists largely of cholesterin, C 96 H 44 0, which may be obtained in characteristic crystalline tablets by warm- ing the ethereal extract with alcohol, and allowing the solution to cool. The proportion of unsaponifiable matter soluble in ether which is naturally present in fixed oils and fats rarely exceeds 1 J per cent., and is usually much less. Sperm and bottlenose whale oils, however, constitute an exception, yielding about 38 to 40 per cent, of matter soluble in ether. This peculiarity has little prac- 1 Sometimes it is very difficult to obtain a constant weight by the means indicated in the text. In such cases, instead of heating the flask on the water- oven, it should be kept on the bath of boiling water and a moderate current of air, filtered by passing it through a tube containing cotton-wool, should be blown through it by a second tube passing through the cork. The fittings are then detached, and the flask heated for a short time in the water-oven. 2 Traces of fatty oils which had escaped saponification and traces of soap are apt to pass into the ethereal solution, and hence the proportion of unsaponifiable matter found is often slightly reduced on treating the ether-residue with alcoholic potash, and again extracting the solution of the soap with ether. NATURE OF THE ETHER-RESIDUE. 85 tical effect on the applicability of the process, as sperm oil being among the most valuable of commercial fixed oils, it is rarely present without due acknowledgment of the fact. An unknown oil may be recognised as sperm or bottlenose oil by the characters detailed in the section relating to them (see "Sperm Oil"). Spermaceti and the other waxes yield after saponification large percentages of matter to ether, and hence the process is not available for the determination of paraffin wax in admixture with these bodies, though it gives accurate results with the mixtures of paraffin and stearic acid so largely employed for making candles. The following table indicates the behaviour of the constituents of complex mixtures of fats, oils, and waxes when the aqueous solution of the saponified substance is shaken with ether : Dissolved by the Ether. Remaining in the Aqueous Liquid. Hydrocarbon Oils; including Shale and Petroleum Oils, Rosin Oil Hydrocarbons, Coal-tar Oil, Paraffin Wax and Ozokerite, Vaselene. Neutral Resins. TJnsaponified Fat or Oil. Unsaponifiable matter, as Cholesterin, from liver oils, &c. Dodecatyl Alcohol, from Sperm and Bottlenose Oils. Cetyl Alcohol, from Sperma- ceti. Myricyl Alcohol, from Bees- wax. Colouring matters, as from Palm Oil. Fatty Acids. Resin Acids. Carbolic and Cresylic Acids, and other phenols. Glycerol (Glycerin). Excess of Caustic Potash. In the form of potas- sium salts. The hydrocarbon oil having been isolated by saponifying the sample and agitating with ether, its nature may be ascertained by observing its density, taste, and smell, behaviour with acids, bromine, &c. The specific gravity may be determined by means of a very small specific gravity bottle or Sprengel-tube. If the proportion of hydrocarbon oil be small, it may be necessary to operate on a larger quantity than 5 grammes of the sample. A very fair approximate estimate of the density of the extracted hydrocarbons may be made on Hager's principle (page 18), by adding a drop of the oil to very dilute alcohol, or ammonia, and adjusting the strength of the liquid so that it may be identical with that of the drop of oil. The specific gravity of the dilute 86 DETERMINATION OF HYDROCARBON OILS. alcohol is then ascertained in the usual way. The fluorescence of hydrocarbon oils is best observed in the manner described on page 81. It often becomes intensified by treating the extracted hydrocarbon with an equal measure of strong sulphuric acid. The smell and taste of the hydrocarbon oils are often highly characteristic of their origin. The smell of coal-tar oil is readily observed ; and the taste, especially the after-taste, of rosin oil is not to be mistaken. The smell produced on strongly heating a drop of the oil in a platinum capsule is also highly charac- teristic. Further details respecting the behaviour of various hydrocarbon oils with tests are given in the section on " Mineral Lubricating Oils." The higher alcohols from sperm and bottlenose oil may be separated from hydrocarbon oils by treating the ether-residue with rectified spirit, which dissolves the alcohols without notably affect- ing the hydrocarbons. If the aqueous liquid separated from the ethereal layer be treated with dilute sulphuric acid, the fatty acids are liberated, and may be weighed, titrated with standard alkali, or otherwise examined. (See page 37.) c. When it is merely desired to ascertain approximately the proportion of hydrocarbon oil in a mixture, and not to isolate it and examine it further, there is no occasion to extract the solution of the saponified oil with ether. Instead, the aqueous liquid may be at once acidulated with dilute sulphuric acid, a little ether added to promote the separation of the mixed hydrocarbon oils and fatty acids, the aqueous liquid tapped off, and the oily layer repeatedly agitated with water till the washings are no longer acid to litmus. Rectified spirit and a few drops of phenol-phthalein solution are then added, and the liquid titrated with decinormal caustic alkali in the manner directed on page 76. The oleic acid thus deduced, multiplied by 1'053, gives the amount of glycerides in the sample, and the difference may be regarded as unsaponifiable matter. The latter represents the hydrocarbon oils, and the former the fatty oils of the mixture, provided that waxes, including sperm and bottlenose oils, are absent. d. When the nature of the fatty oil is known, and it is merely desired to estimate the proportion of hydrocarbon oil present, and not to ascertain its exact character, a very fair approxi- mation to the truth can be obtained by ascertaining the saponifica- tion-equivalent of the sample, as described on page 44. The following table gives an outline of the processes described in the foregoing section : DETERMINATION OF FOREIGN MATTERS. 87 .2 -a o fl li I! ^d: fi o il "S'd !l s 2 O ft !" w g II 3U il T3 a It ii 11 H fulfill IcSSl-g 1 11-s^I^ S IfrssS l!l*! &kj*?* "^Sff|i9> hiliiM J.o 3 * -Sn-t "S3 8-<3 is! 0.-S &Sb2 *u g^s :n il., Wl g oo CO o n^iftniT^ftiii! -i a ^|fl s fs,8^il*ls l^^ajl^l^l^giS-Sft^ i^i s iii!isi z ii s i lorfj^. L|'^"t -'0^ ^ll^SS-SlS^^Ssa;^ 'flillilllllllll Ht rrt !- |i*t-si, |*|: 58^-gglSA |||M3'gS|- 1 J|lll|a iipriiiiifit 5.31* 88 IDENTIFICATION OF FIXED OILS. IDENTIFICATION OF FIXED OILS. The recognition of an unmixed animal or vegetable oil may usually be effected by a careful application of the methods of examination already described. Various systematic schemes for the purpose have been devised by different chemists, but no such method can be implicitly relied on, owing to the variable nature of the oils themselves. In particular, any positive recognition based on the colour-reactions of an oil is of little value, unless confirmed by the indications of other tests. In examining oils for the detection of adulteration, the relative commercial value of the different kinds should never be lost sight of, and it must be remembered that in addition to the adulteration of the more valuable fatty oils with the cheaper, their sophistica- tion by admixture with the hydrocarbon oils obtained by the distillation of petroleum, shale, coal, rosin, &c., is also extensively practised. 1 Practically, it is often of less importance to know whether an oil has the origin attributed to it than to learn whether its characters are such as will allow it to be safely used as a substitute for the genuine oil. This may be ascertained with tolerable certainty, and in some cases the nature of the adulterants definitely detected. Although it is not possible to lay down any general scheme which shall be available for the identification of any unmixed fatty oil, the recognition is much facilitated by conducting the examination on a systematic plan. By proceeding in the following manner, positive identification of a particular oil may generally be effected, and so much information gained as to the probable constituents of a mixture that special tests for the oils suspected to be present may then be successfully applied : 1. Place a drop of the oil on the back of the tongue by means of a glass rod and taste it carefully, avoiding too hasty a decision. 1 The following is a list of the principal commercial fluid oils, arranged by. Mr T. Duggan as nearly as possible in the order of their usual commercial value, which in some cases is liable to considerable fluctuations : 1. Olive oil. 2. Sperm oil. 3. Neatsfoot (real) (a) Bottlenose oil. 4. 1 (b) Lard oil. (c) Castor oil. Cod oil. (a) Arachis oil. 8. <[ (b) Sesame oil. (c) Poppyseed oil. 11. Colza and Rape oil. 12. Seal oil. 13. Nigerseed oil. 14. Linseed oil. 15. Whale oil. 16. Cottonseed oil. 17. Menhaden oil. 18. Japan fish oil. 19. Mineral oils. 20. Rosin oil. SPECIFIC GRAVITY OF OILS. 89 In this manner marine animal oils, linseed oil, croton oil, mineral oil, rosin oil, and some others may generally be detected. Eosin oil is remarkable for the nauseous after-taste of rosin produced by it. Rancidity of an oil may easily be recognised by the taste. 2. Heat a portion of the oil in a porcelain or platinum capsule to about 140 or 150 C., and observe the odour carefully. When sufficiently cool, pour a little of the oil into one hand, rub with the other, and smell again. A little practice will allow of vegetable oils being readily distinguished from animal oils, and the products of fish and marine mammals from those of terrestrial animals. The odour on heating will also frequently permit the recognition of mineral and rosin oils, and, if the remainder of the oil be strongly heated till it ignites and the flame then blown out, the vapours will often have a highly characteristic odour. 3. Ascertain the specific gravity of the sample at 15 '5 C. ( 60 F.) if fluid at that temperature, but at the boiling point of water (page 16) if solid at the ordinary temperature. This test is a very valuable means of recognising individual oils, but if the sample be very old, if much free acid be present, or the sample be a mixture of several oils, its indications are less reliable. The following table enables an unmixed oil to be arranged in one of nine groups, according to its specific gravity and physical state at the ordinary temperature. More precise determinations of the densities of the fatty oils are given in the tables commencing on page 63. OILS, LIQUID AT THE ORDINARY TEMPERATURE (15 to 16 C.), ARRANGED ACCORDING TO THEIR SPECIFIC GRAVITY. Speciflc Gravity at 15 to 16 C. (= 59 to 61 F.). Class of Oil. a b. C. d. e. 875 to 884. 884 to 912. 912 to 920. 920 to 937. 937 to 970. Cotton- $ seed "3 & Sesame bcS" * Sunflower B Vegetable Oils, None. None. Olive Almond Ben Arachis Rape and Colza Mustard on-drying oils (] Hazelnut Poppy- seed Hemp- seed Linseed (raw) More or less dry (pages 64 and Japanese wood. Croton. Castor. Manufactured. Boiled linseed. Blown oils. fe Walnut L Manufactured. Cocoanut olein. 90 SPECIFIC GRAVITY OF OILS. Class of Oil. Specific Gravity at 15 to 16 C. (= 59 to 61 F.). 875 to 884. 6. 884 to 912. c. 912 to 920. d. 920 to 937. e. 937 to 970. Terres- ( Neatsfoot. Bone. trial Animal ~j None. None. Manufactured. Lard oil. None. None. Oils, [^ Tallow oil. Whale. Sperm. Bottlenose. None. Shark-liver. Porpoise. Seal. Menhaden, None. Codliver. Shark-liver. Free } Fatty V Acids, J None. Oleic acid. Linoleic acid. ( Ricinoleic \ acid. Hydro- ( carbon < Oils, \ Shale products. Petroleum products. Shale products. Petroleum products. Heavy petroleum products. None. None. OILS, &c., PASTY OR SOLID AT ORDINARY TEMPERATURES (15 to 16 C.), ARRANGED ACCORDING TO THEIR SPECIFIC GRAVITY WHEN MELTED. Class of Oil. the corresponding (calculated) iodine-absorption is obtained. (See page 47.) The colour-test with sulphuric acid, described on page 59, gives further useful information. (See " Codliver Oil.") Porpoise oil and some varieties of whale oil contain a notable proportion of glycerides of lower fatty acids, and hence give very characteristic results with Reichert's distillation-test (page 46). 1 This figure is not due to Hiibl, but is the mean of several determinations by L. Archbutt. Hiibl's melting and solidifying points were determined by introducing the fatty acids into a narrow test-tube, gently agitating with a thermometer, and noting at what point the whole contents become either quite clear or slightly cloudy. IDENTIFICATION OF FIXED OILS. 93 The following table shows the behaviour of the principal fish oils with the foregoing tests. For convenience of comparison, sperm and bottlenose oils are included in the table : Hal ogen-absorption. Oil. Saponifica- tion- CQ uiv&lcnt. Turbidity- temperature. Temperature with H 2 S0 4 . Bromine. Iodine. 127 Brx w Direct. Sperm . j 380 to 454 98 45 to 47 56 89 84 Bottlenose 419 to 456 102 41 to 47 49 78 80 Whale . 250 to 296 31 to 83 85 to 91 51 81 Porpoise 256 to 260 40 50 Seal . 286 to 296 72 92 57 to 60 91 to 95 Menhaden 292 64 123 to 128 148- Cod-liver 303 79 to 101 103 to 116 81 to 87 129 to 138 Ling-liver Haddock-liver 82 110 131 175 Skate-liver 102 109 to 123 173 to 195 .. Shark-liver 316 to 400 105 90 84 134 e. The oils of a density exceeding 937 are few in number and easily distinguished. Croton and castor oil are purgative and readily soluble in rectified spirit, but have little further resem- blance. Boiled linseed oil and Japanese wood oil have a density between 937 and 950, dry very rapidly on exposure, and give a firm brown or black clot with sulphuric acid. Blown oils closely resemble castor oil, but may be readily distinguished as described in the section treating of that oil. (See also page 66.) Eosin oil has a density exceeding 970, and is not saponified to any considerable extent by alkalies. It is readily identified by its strong after- taste, and the terebinthinous odour developed when the sample is heated till it catches fire, and the flame then blown out. Mixtures of rosin oil with fatty oils may be analysed as described on page 83. /. The solid hydrocarbons having a density below 800 at the boiling point of water are described under " Paraffin Wax." g. The distinctions between the various waxes are fully indi- cated in the table on page 73, and in the special sections on "Spermaceti," "Beeswax," and "Carnaiiba Wax." Free fatty acids are at once distinguished from the waxes by their solubility in alco- hol, behaviour with alkalies, and their saponification-equivalents ; from each other by their melting points and combining weights. Yaselene and similar hydrocarbons are sharply distinguished from the waxes and fatty acids by being incapable of saponification. h. The solid vegetable fats of low density are 94 IDENTIFICATION OF FIXED OILS. somewhat numerous and have not been much studied, but very few of them are commonly met with. The colour, taste, and odour suffice to distinguish many of them, and further information is afforded by Valenta's acetic acid test (page 26) and the deter- mination of their melting and solidifying points. The animal fats may be distinguished by similar means. i. The vegetable fats of high density are readily differentiated. Cocoanut and palmnut oils are soft, melt very readily, and have low saponincation-equivalents. Japan and myrtle wax are hard wax-like bodies of comparatively high melting point. (See "Japan Wax.") Palmnut oil is distinguished from cocoanut oil and cocoanut stearin by its taste and smell. Butter fat is the only fat of animal origin (except wool fat) having a density higher than 863. Its odour, taste, and behaviour with Reichert's test (page 46) are highly characteristic. The oil having been more or less satisfactorily identified in the manner already indicated, further confirmation of the result may be obtained by referring to the tables commencing on page 63. The principal commercial oils are described at greater length in the following sections. In the case of a sample consisting of a complex mixture of wholly unknown oils, the identification of the constituents is often a problem of extreme difficulty, but when the leading component is known or can be recognised, the detection of the others be- comes more feasible. It must, however, always be borne in mind that in most cases oils cannot be recognised by distinct and specific tests, such as exist for the different metals, and that in arriving at a conclusion as to the composition of any sample of mixed oils, the analyst must be content to be guided in a great measure by circumstantial evidence, and a careful consideration of probabilities. The foregoing methods of examination are of course employed, and in addition such special tests as will be found described under the various heads. The sub-articles de- scriptive of the more important commercial oils contain a list of the admixtures most commonly found in each oil and special tests suitable for their detection. The following facts, which depend on the chemical nature of the oils, are of importance in the examination of complex samples, and to a less extent for the identification of unmixed oils : Much information may be obtained by saponifying the oil and determining the products formed by the reaction. Thus most fixed oils are split up into a fatty acid and glycerin, but sperm oil and the waxes yield products differing from glycerin in being insoluble in water but soluble in ether (see page 3 1 et seq.). Sperm and bottle- IDENTIFICATION OF FIXED OILS. 95 nose oils only yield some 63 per cent, of fatty acids, while most other fixed oils (not the waxes) give about 95 per cent. Butter fat, porpoise oil, and the oils from cocoanut and palmnut yield a notable proportion of acids which are volatile or soluble in water, but in the case of almost all other oils the whole of the fatty acids are practically insoluble (page 30 et seq.). Resin gives 100 per cent. of resin acids and no glycerin, but mineral and rosin oils do not undergo saponification at all, and so can be dissolved out of the solution of soap by agitating with ether (see page 83). The physical properties and combining weights of the fatty acids afford important information. The acids from rape and castor oils neutralise sensibly less alkali than those from most oils. Lard, tallow, and neatsfoot oils yield fatty acids of much higher melting point than the non-drying vegetable oils which they other- wise resemble. Cottonseed oil yields fatty acids solid at the ordinary temperature, while most drying and semi-drying oils yield liquid acids. Any admixture of resin acids tends greatly to increase the density of the fatty acids, at the same time lowering their melting point. When it is intended to examine the charac- ters of the fatty acids, it is highly important that the aqueous and alkaline solution of the soap should be previously agitated with ether until nothing more is removed, as any admixture of wax or hydrocarbon oil would profoundly modify the properties of the fatty acids The details of the method of separating these admixtures and of determining the fatty acids will be found on page 78 et seq. The drying oils are heavier but less viscous than the non-drying oils, apparently in proportion to their drying tendency. The non- drying oils give solid elaidin (page 57), the product becoming less and less firm as it is derived from a more strongly drying oil. Similarly, the heating produced by mixture with sulphuric acid, the solubility in glacial acetic acid, and the iodine-absorption appear to bear a direct relationship to the drying properties of a vegetable oil. By a careful application of these facts an approxi- mate estimate of the proportions of different oils in a mixture can often be made. SPECIAL CHARACTERS AND MODES OF EX- AMINING FATTY OILS AND WAXES. The methods of examining oils hitherto described have been mostly general, but the following sections contain more detailed information respecting the specific characters and modes of assaying the more important fatty oils and waxes. 96 OLIVE OIL. Olive Oil. French Huile d' Olives. German Olivenb'l. (See also table on page 63.) Olive oil is extracted from the fruit of the olive by pressure, and of late years by solution in carbon disulphide. 1 Olive oil varies somewhat in its physical characters according to its quality. The finest kinds have a pale yellow colour, with a tinge of green, are almost whollyfree from odour, and possess a mild and agree- able taste. Inferior qualities have a greenish-yellowish or brownish- yellow colour, an unpleasant odour, and a decidedly acrid after-taste. The absorption-spectrum of fresh olive oil shows well-defined chlorophyll bands, which become changed or altogether destroyed on exposing the oil to sunlight or heating it with caustic alkali. When cooled to about 10 C., olive oil deposits a white granular fat. At it solidifies to a product which can be separated by pressure into a solid tallow-like fat, consisting chiefly of t r i-p a 1 m i t i n, and about 70 per cent, of a fluid oil, composed essentially of tri- o 1 e i n. By saponification olive oil yields glycerin, and soaps of oleic, palmitic, and smaller quantities of s t e a r i c and arachidic acids. Traces of cholesterin are sometimes present, and usually more or less free oleic acid (see page 29). Olive oil is the type of a non-drying vegetable oil. It does not thicken materially, even on prolonged exposure to air, but gradually becomes rancid, a change which appears to be dependent in great meas- ure on the presence of certain albuminous and mucilaginous matters. 1 Of the commercial varieties of olive oil, Provence and Tuscan oils are among the most esteemed. The finest oil in the market is "finest cream sublime olive," which is imported from Leghorn. Oils of other origin, in the order of their commercial value, are "Sublime," Gallipoli, Sicilian, Spanish, Portuguese, Levant, and Mogadore. Oil, usually of inferior quality, is now imported from Sfax, a port on the coast of Tunis. The oil now sold in the so-called "Florence flasks" is usually of very inferior quality. Lucca and Gallipoli oils are well-known brands, and much excellent oil is now expressed in Spain, and exported from Malaga and Seville. The variations in the quality of olive oil are largely dependent on the manner in which the olives are treated, as e.g., the care with which the fruit is plucked, the length of time it is stored before being crushed, and other con- ditions which affect the colour, smell, and appearance of the oil expressed. In some countries olive oil is an important article of diet. It is employed in the manufacture of woollen cloth, and in dyeing fabrics turkey-red, though its application for these purposes is decreasing. The inferior varieties are em- ployed in soapmaking. Olive oil is highly esteemed as a lubricant, and is largely consumed for this purpose when the price is moderate. The quantity used in this way depends much on the price of rape oil, which is usually much cheaper, and, though more liable to "gum " than olive oil, is less apt than the latter to become rancid. ASSAY OF OLIVE OIL. 9? The specific gravity of olive oil ranges from about 914 to 917 or to 918 as an extreme maximum. Samples containing much free acid have the lowest density (see page 98). When heated to about 120 olive oil becomes lighter, and at 220 nearly colourless and at the same time rancid. At 315 C. (= 600 F.) it "boils" and suffers decomposition, producing a disagreeable odour of acrolein. Olive oil, if free from acid, is only slightly soluble in alcohol, but dissolves in about 1 J times its weight of ether, and is miscible in all proportions with carbon disulphide, chloroform, and hydro- carbons. ASSAY OF GENUINE OLIVE OIL. Many samples of genuine olive oil contain a notable quantity of free fatty acid, the proportion of which increases by keeping and exposure. In 89 samples of olive oil, intended for lubrica- tion, and the other characters of which proved them to be genuine, L. Archbutt (Analyst, ix. 171) found proportions of free fatty acids (calculated as oleic acid) ranging from 25'1 to 2 '2 per cent., the average being 8'05 per cent. He found the presence of an excessive proportion (above 5 per cent.) of free acid to render olive oil unsuitable for burning in lamps, especially the roof-lamps of railway-carriages, by causing a serious charring of the wick. In olive oil intended for table use the proportion of free acid should be very trifling. For soap-making the presence of free acid is no detriment, and for turkey-red dyeing a very acid oil is preferred. The proportion of free fatty acid in olive oil can be ascertained with ease and accuracy by titration in presence of alcohol with standard caustic alkali and phenol- phthalein, in the manner described on page 76. M. Burstyn (Dingl.polyt, /., ccxvii. 314; Jour. Chem" Soc., xxix. 769) has described the following method for estimating the free acid in olive oil. It is intended for rapid technical investiga- tions, for which purpose the process appears well suited, though the volumetric method described on page 76 will be rightly preferred by chemists. The oil is shaken with an equal measure of rectified spirit of 830 to 840 specific gravity. After the oil has separated, the density of the spirit is accurately observed by a gravity-bottle, plummet, or delicate hydrometer graduated from 825 to 850. The density of the original alcohol must also be accurately known. If the density be observed by a plummet or hydrometer, there is no occasion to note the temperature, provided the specific gravity of the original spirit be taken side by side with that with which the oil has been agitated. Burstyn finds that an oil, 100 c.c. of which contains free acid in quantity sufficient VOL. II. 98 EXAMINATION OF OLIVE OIL. to neutralise 1 c.c. of normal alkali (= '282 per cent, of oleic acid), will raise the density of the oil from. 830 '0 to 832'5, and that each additional 1 c.c. of alkali neutralised causes an increase of '3 in the density of the spirit. Hence it may taken that the increase due to the solution of a trace of neutral fat in the spirit is 2*2, and that each iinit of increase of density beyond this number represents 2 ~- = '094 gramme of free acid per 100 c.c. Burstyn states that the action of olive oil on brass is regularly and directly proportional to the percentage of free acid present. In examining olive oil intended for cooking or table use the flavour and odour should be carefully observed, as many specimens of apparently genuine oil, which are fairly free from acid, are un- satisfactory in this respect. EXAMINATION OF OLIVE OIL FOR ADULTERANTS. Owing to its superior commercial value, olive oil is very liable to adulteration, the sophisticated sample being sometimes coloured to give it the appearance of green olive oil. Cottonseed oil is perhaps the most frequent adulterant ; but arachis, sesame, poppy, and rape oils are also used. Poppy oil is said to be a favourite addition, on account of its sw^eet taste and slight odour. Fish oils are occasionally employed, menhaden oil being said to be used frequently. Lard oil is largely used when the price permits of it, " superfine Lucca oil " being stated sometimes to contain as much as 60 to 70 per cent. Hydrocarbon oils are also used. In examining olive oil, the most important indications are the density, the saponification-equivalent, the iodine-absorption, the rise of temperature on treatment with 'sulphuric acid, the elaicliri- test, and certain colour-reactions. Certain sophistications require the application of special tests for their detection. The specific gravity of olive oil varies very sensibly with the quality, the most acid specimens having the lowest densities. The range allowed by the German and United States pharmacopoeias is between 915 and 918, at 15 C. Of upwards of eighty samples of genuine olive oil examined by L. Archbutt the specific gravity at 15'5 C. ( = 60 F.), compared with water at the same temperature, never exceeded 917 '0, and was rarely as high. The lowest density observed was 913'6, the sample containing 24*5 per cent, of free oleic acid. Hence it is evident that the proportion of free acid should be taken into account in judging of the genuine character of olive oil from its density. Taking the density of genuine neutral olive oil as 917*0, it appears that each 5 per cent, of free acid diminishes the specific gravity of the sample by about 07. Adulteration of olive oil with rape oil will tend slightly to reduce the density of the sample, whilst addition ion ELAIDIN-TEST FOR OLIVE OIL. 99 of the oils of Groups II. and III. will increase it. A judicious admixture of rape and cottonseed oils will not affect the density of the sample, but the presence of any considerable proportion of rape oil will sensibly raise the saponification equivalent of the sample. The iodine-absorption (page 48) is a valuable means of detecting adulterations of olive oil. Genuine samples show an absorption varying from 81 to 85 per cent, as extremes, while rape, sesame, and cottonseed oils all assimilate upwards of 100 per cent., and poppy seed, hempseed, and linseed oils from 134 to 160 per cent. Earthnut oil is not so distinctly indicated. The rise of temperature on treating the sample with sulphuric acid, as described on page 53, is a valuable indication of the purity of olive oil. Almost all oils, except cocoanut oleiii and tallow and lard oils, produce more heat than olive oil, so that a rise of temperature of more than 44 C. may at once be consi- dered as indicating probable adulteration, and in some cases (see page 55) it allows of an approximate estimation of the extent of the sophistication. The elai din-test (page 57) is one of great value for detecting sophistication of olive oil. With pure olive oil the mixture becomes so solid in less than two hours at 15 to 20 C. that it cannot be displaced by shaking the bottle, and in twenty-four hours a perfectly solid and sonorous mass of pale yellow or nearly white colour is produced. 1 With adulterated samples, the elaidin is orange or dark red, and liquid or imperfectly solid. Not unfre- quently a distinct liquid layer is formed on the surface of the solid elaidin. The above test is applicable to the detection of sesame, rapeseed, cottonseed, poppyseed (as little as 5 per cent.), linseed, and other oils of Groups II. and III. when in admixture with olive oil. (See also a paper by L. Archbutt, Jour. See. CJiem. Ind., May 1886.) Exposure to air under the conditions prescribed on page 51 is also a test for an admixture of the drying oils. The colour-reaction with nitric acid is a useful test for adulterants in olive oil. By careful application of the 1 According to Moschini, exposure to sunlight deprives olive oil of the prc- perty of forming a solid elaidin by the action of nitrous acid. L. Archbutt has observed a similar change in the temperature-reaction with sulphuric acid produced by exposure to light. Two portions of the same sample of pure olive oil were examined with the following results : Portion kept in darkness. Portion exposed to light. Colour of oil, . . Yellow. Bright green. Free acid, . . . 4 '0 per cent. 4 '6 per cent. Rise of temperature, . 41 '5 C. 52*5 C. 100 COLOUR-TESTS FOR OLIVE OIL. tests described on page 61 nearly all admixtures except the oils giving hard elaidins (e.g., almond oil, lard oil) can be detected. When testing for cotton oil more especially, Zecchini recommends an acid of 1*40 specific gravity, and states that it must be free from nitrous compounds, or a reddish colour will be produced, even with pure olive oil. Equal measures of the oil and acid are briskly agitated together for half a minute, and the tube then allowed to stand at rest in a vertical position for five or six minutes. (If left much longer, pure olive oil may give a coloration.) In presence of cottonseed oil a golden-yellow colour is produced, changing to a deep coffee-brown, the depth of tint indicating the proportion of admixture. Acid of a less density than 1*40 produces with cottonseed oil only a light-coloured liquid, scarcely distinguishable from the colourless or straw-coloured mixture, changing to grey with a yellowish reflex, which is produced by olive oil. O. Bach applies nitric acid to the detection of oils liable to be used for the adulteration of olive oil in the following manner : Agitate 5 c.c. of the sample with an equal volume of nitric acid, of 1*30 specific gravity, and note any coloration which may be pro- duced. Then heat the test-tube in boiling water for five minutes, and again observe the effect. On heating the oil and acid together a more or less violent reaction may be produced, even resulting, in the case of cotton and sesame oils, in the mixture being projected from the tube. After standing for twelve or eighteen hours the appearance of the mixture is again noted. The following reactions are observed at the three stages of the process described : Kind of Oil. After agitation with Nitric Acid. After heating for 5 Minutes. After standing 12 to 18 Hours. Olive oil Earthimt oil Pale green. Pale rose. Orange-yellow. Brownish-yellow. Solid. Solid. Rape oil Pale rose. Orange-yellow. Solid. Sesame oil . White. Brownish-vellow. Liquid. Sunflower oil Dirty white. Reddish-yellow. Buttery. Cottonseed oil Y ello wish-brown , Reddish-brown. Battery. Castor oil . Pale rose. Golden-yellow. Buttery. Mixtures of olive oil with small proportions of cotton or sesame oil are stated to solidify on standing, after 24 to 36 hours separat- ing into a brown liquid floating on a pure yellow mass. It is evident that Bach's mode of operating is an attempt to combine the elaidin-test with the nitric acid colour-test. 1 1 Massie agitates 10 grammes of oil with 5 of nitric acid (sp. gr. 1'40) COLOUR-TESTS FOR OLIVE OIL. 101 M. Conroy (Pharm. Jour., [3], xi. 933) prefers to agitate 18 c.c. of oil with 2 c.c. of nitric acid of 1*42 specific gravity and pour the mixture into a capacious porcelain dish. A gentle heat is then applied until the chemical action is fairly set up, when the source of heat is removed and the mixture stirred till the action ceases. Pure olive oil, when thus treated, sets into a pale straw-coloured mass in an hour or two, while cottonseed and other seed oils give a deep orange-red product which does not set like that from olive oil. By comparing the colour and consistency of the product with that yielded by a mixture of known composi- tion, a very fair approximation to the extent of the adulteration is said to be obtainable, at least in the case of cottonseed oil. According to A. Audoynaud (Compt. Rend., ci. 752; Jour. Ghem. Soc. t 1. 182) adulterations of olive oil may be detected by the following test : 2 c.c. of the sample is vigorously shaken in a graduated tube with O'l gramme of powdered potassium di- chromate, sufficient " nitre-sulphuric acid " added to bring the volume to 4 c.c., and the mixture again agitated. After a lapse of two minutes 1 c.c. of ether is added and the liquid mixed by agitation. Red fumes are evolved, and on standing the mixture separates into two layers, the upper one of which acquires a charac- teristic colour. If pure olive oil has been employed the upper stratum is green, but in presence of even 5 per cent, of sesame, poppy, arachis, or cottonseed oil the colour is modified, varying from greenish-yellow to yellow or even reddish-yellow according to the proportion present. The colour is more readily observed if an equal measure of water be previously added to the mixture. The melting and solidifying points of the fatty acids will often allow the nature and proportion of an admixture with olive oil to be inferred, and 0. Bach has suggested the use of J. David's process of separating stearic and oleic acids (see " Oleic Acid") for detecting adulterants. According to Bach, if 1 c.c. of the fatty acids from genuine olive oil be treated with 15 c.c. of David's and 1 gramme of mercury, and observes the colour of the product after one hour, and also the time required for solidification. Thus : Minutes Minutes Oil. Coloration. for Solidi- Oil. Coloration. for Solidi- fication. fication. Olive, . . Pale yellowish- green. 60 Rape, . Cottonseed Orange. Orange-red. 200 105 Hazelnut, Almond, . White. White. 60 90 Sesame", Beechnut, Yellowish-orange. Reddish-orange. 150 360 Arachis, . Pale reddish. 105 Poppy, . Red. fluid Apricot, . Rose. 105 Camelina. Reddish-orange. fluid 102 ADULTERATIONS OF OLIVE OIL. alcoholic acetic acid, perfect solution takes place at the ordinary temperature, while the acids from cottonseed oil are insoluble, and if solution be effected by warming the liquid the solution obtained gelatinises when cooled to 15 C. The fatty acids from sesame and earthnut oil are stated to behave similarly, while those from sunflower oil dissolve on warming, but separate as a granular precipitate at 15 C. The acids from rape oil are com- pletely insoluble and float on the surface of the liquid. Olive oil containing 25 per cent, of sesame or cottonseed oil yields acids which form a granular precipitate, but smaller proportions cannot readily be detected. Sesame oil in admixture with olive oil may be recognised by the cohesion-figure produced when a drop of the sample is placed on clean water as described on page 11. It may also be detected by agitating 10 c.c. of the sample for at least ten minutes with 5 c.c. of hydrochloric acid of 1*17 specific gravity in which 0*1 gramme of sugar has been previously dissolved. The acid, on separation from the oil, assumes a rose colour if oil of sesame be present, the intensity of the tint increasing with the proportion of the adulterant. The agitation must be continued for at least the time prescribed, when even 1 per cent, of sesame oil can be detected. The test may be modified by dropping fuming hydrochloric acid on a lump of sugar, and agitating the sugar with the oil. (See also page 61.) Aracliis or earthnut oil has about the same density as olive oil, but solidifies somewhat less readily. It may often be recognised by its well-marked taste of kidney beans, but more certainly by the test described on page 106. It gives a red colour with nitric acid, but yields slowly a solid elaidin with nitrous acid. A sample of so-called " green olive oil, from Malaga," was found by Cailletet to consist solely of arachis oil coloured with acetate of copper. Lard oil is difficult to detect with certainty in olive oil, but its presence may be inferred from the altered viscosity of the sample, the diminished intensity of the absorption-bands, the higher melting point of the fatty acids, and, in some cases, by the odour of lard developed on warming the sample. Fish oils will be detected by the smell on warming the sample ; by the red colour produced on heating the oil with solution of soda ; by the brownish colour developed with sulphuric acid ; and by the darkening produced on agitating with hydrochloric acid or passing chlorine. Hydrocarbon oils may be detected and determined by the methods described on page 80 et seq. OLIVE-KERNEL OIL is now extracted by a solvent, usually carbon disulphide. It is of a dark greenish-brown colour, and has about the TUKKEY-RED OIL. 103 same saponification-equivalent and iodine-absorption as olive oil; but the density is about 920, and it is stated by Valenta to be soluble in an equal measure of glacial acetic acid at the ordinary temperature. The oils extracted by carbon disulphide from pressed marc (" sulpho-carbon oils ") resemble olive-kernel oil in their behav- iour with acetic acid, usually yield no solid elaidin, have an iodine-absorption of 79 to 80, and are characterised by their dark colour and unpleasant smell. TURKEY-RED OIL. In dyeing cotton turkey-red a necessary stage consists in treating the cloth with oil. The oil employed for this purpose in England is frequently the variety of olive oil known as " Gallipoli oil." Although it is not essential that olive oil should be used, it is important that it should be thoroughly non-drying, and this is ascertained by the elaidin-test in the manner described on page 57. A good sample will give elaidin not only solid and firm, but nearly white. A yellow, soft, or semi-fluid product indicates undesirable admixtures. Oil suitable for turkey-red dyeing is prepared from somewhat un- ripe olives, which are steeped for some time in boiling water before being pressed. This treatment causes the oil to contain a large proportion of extractive matter, and hence it soon becomes rancid. Another plan is to agitate oil which has been some time in store for several days at a temperature of about 40 C., air being allowed free access. A third method is to add oleic acid as such to the oil. Turkey-red oil should form a white emulsion when agitated with a dilute solution of caustic or carbonated alkali. To test its quality one part of the sample of oil should be beaten up with from thirty to forty parts of seminormal caustic soda solution (2 to 2J parts of caustic soda, NaHO, per litre). If, after standing six hours, the mixture be still found to be homogeneous, without any sign of separation of the oil, the sample is fit for its intended use. An entirely different preparation, now extensively used as a turkey-red oil, is prepared from castor oil. (See page 130.) Almond Oil. French Huile d'Amandes. German Mandelol. (See also table on page 63.) Almond oil is the fixed oil expressed from either sweet or bitter almonds. 1 It is largely 1 Practically, nearly the whole of the almond oil of commerce is expressed from bitter almonds, the marc of which is then distilled with water to obtain the essential oil. Sweet almonds are commonly consumed as such at table. Fixed oil of almonds must not be confounded with the essential oil of bitter almonds, a product which is described in the section on " Benzoic Aldehyde." 104 ALMOND OIL. employed in the preparation of ointments and emulsions, for which it is better adapted than olive oil. Almond oil is a thin, oily fluid, nearly odourless, of a straw- yellow colour and bland taste. It does not solidify till cooled to about 20 C., 1 some samples only becoming turbid at that temperature. The density ranges from 914 to 920. It is soluble in 24 parts of cold alcohol or in 6 parts at the boiling point. Chemically, the fixed oil of almonds consists chiefly of triolein, more or less tripalmitin, and probably its homologues, being also present. It is said also to contain traces of c h o 1 e s t e r i n, and to be distinguished by this fact from poppy, sesame, rape, and olive oil. Almond oil readily turns rancid when exposed to the air, but is not siccative. COMMERCIAL ALMOND OIL. Almond oil is not unfrequently adulterated with, and some- times entirely substituted by peach-kernel or apricot-kernel oil, which is sold in England as "foreign almond oil." Olive, arachis, sesame, rape, poppy, and lard oils are also liable to be employed. Many of these additions may be detected by observing the absorp't ion-spectrum of the sample, almond oil differing from most vegetable oils in not giving either a banded spectrum or producing strong absorption in the red or the violet. The elai din-test serves for the detection of poppy and rape oils, the solidification being much retarded by those adulterants. The nitric acid colour-tests described on pages 61 and 100 also serve for the detection of several foreign oils. According to the German Pharmacopoeia, if 15 parts of the oil be well agitated with a mixture of 3 parts of fuming nitric acid and 2 parts of water, the mixture should be whitish, not brown or red (absence of cottonseed, earthnut, sesame, &c., oil), and after several hours should form a solid white mass (absence of drying oils), the aqueous liquid being nearly colourless. The test also detects the presence of peach or apricot oil. J. D. B i e b e r recommends that 5 parts of the sample should be agitated with 1 part of a cold mixture of equal weights of strong sulphuric acid, water, and fuming nitric acid. When thus treated almond oil gives a white or yellowish-white liniment; sesame oil a product which is at first green or pale yellowish-red, but changes very rapidly to a dirty orange-red ; and peach-kernel oil a reddish 1 According to the German Pharmacopeia, almond oil should remain clear when exposed to a temperature of - 10 C. PEACH AND APRICOT OILS. 105 or peach-blossom colour, changing to dark orange. 5 to 10 per cent, of these foreign oils is said to be recognisable. T. Maben (Pharm. Jour., [3], xvi. 797) gives the following comparative reactions shown by samples of almond, peach, and apricot oils examined by him. A negative reaction with the zinc chloride test suffices to prove the absence of peach and apricot oils : Almond. Peach-kernel. Apricot-kernel. Specific gravity at 15 -5 C.> (=60 F.), . . F 918-0 923-2 920-4 Consistency at -20 C., (Opaque and ) l viscid ; Slightly viscid. Slightly viscid. Bromine-absorption, . Ela'idin-test ; product, (See page 50.) White ; hard. 77 Citron-yellow ; 70 Light yellow; soft. hard. " Nitric acid colour-test,! Slight action. Dark brown. Coffee-brown. Sulphuric acid colour -test, . Yellow to orange. Dark brown. Light brown to reddish-brown. Zinc chloride colour-test, 2 . No change. Purple-brown. Muddy brown, with shade of purple. Pure oil of almonds gives a homogeneous and very firm mass when shaken with one-ninth of its measure of strong ammonia, while the sample is merely clotted in the case of the sample being adulterated with poppy oil, the presence of which would be further indicated by the elaidin-test, the increased temperature developed with sulphuric acid, and the abnormal iodine-absorption. Lard oil and olive oil are indicated by the formation of a white granular deposit when the sample is exposed to a temperature of 5 C. for 20 minutes. Lard oil will be further indicated by the odour developed on warming the sample, and by the high melting point of the fatty acids, and olive oil may usually be detected by the banded absorption-spectrum. An increased saponificatio n-e quivalent indicates the presence of rape oil. Arachis Oil. Earthnut Oil. Peanut Oil. French Huile de pistache de terre. German Erdnussol. (See also table on page 63.) Earthnut oil is obtained from the nuts of Arachis hypogcea, a herb indigenous to America and now cultivated in various countries, the oil being expressed chiefly in France. The seeds contain about 45 per cent, of oil, which in 1 5 c.c. of the sample was shaken vigorously with an equal measure of pure nitric acid of 1 "42 specific gravity, and the coloration observed at the end of five minutes, an hour, and five hours. 2 The zinc chloride was prepared by making a saturated solution of zinc oxide in strong hydrochloric acid. 5 drops of the reagent and 10 of the sample are stirred well together with a glass rod, and any coloration noted. 106 ARACHIS OR EARTH-NUT OIL. India is called katchuny oil, and is largely used as a substitute for olive oil. Arachis oil is pale greenish-yellow, and of a peculiar nutty flavour and smell, resembling peas or kidney beans. A bleached earthnut oil now manufactured in France, and used for adulterating lard oil, is nearly colourless, and almost free from taste. Arachis oil becomes turbid at about 3, and solidifies at about 5 C. The density of the finest oil is 916, and that of the last runnings as high as 920. in chemical composition, earthnut oil is peculiar, as the com- moner glycerides, palmitin and olein, are partially replaced by the homologous glycerides of a r a c h i d i c, C 20 H 40 2 , and hypogoeic acid, C 16 H 30 2 , the properties of which are described in the section on " Higher Fatty Acids." Arachidic acid presents a close resem- blance to stearic acid, from which it differs in its higher melting point (=75 C.) and in being practically insoluble in somewhat dilute alcohol. These characters are utilised for its isolation, and are employed in the process for the detection of arachis oil in olive oil described below. Hypogoeic acid closely resembles oleic acid,and may be separated from arachidic acid by treating the lead salts with ether. Arachis oil is chiefly employed as an adulterant of and substitute for olive oil, its employment for this purpose being apparently not unfrequent in America. With the elaidin-test it behaves much like olive oil, but gives a reddish coloration with nitric acid, and may likewise be recognised by its taste. It may also be detected and approximately estimated by the following modification of a pro- cess devised by A. Renard (Compt. Mend., Ixxiii. 1330), based on the isolation of arachidic acid. From 12 to 15 grammes of the sample should be saponified, and the resultant soap decomposed with dilute acid (page 35 et seq.). 9*5 grammes of the fatty acids obtained (=10 grammes of oil) are dissolved in 50 c.c. of warm rectified spirit, and the liquid precipitated by an alcoholic solution of acetate of lead. 1 When the solution has become cold, the lead soaps are filtered off, washed with a little spirit, transferred to a flask, agitated several times with ether, and then further washed with ether until the washings are no longer coloured brown when shaken with sulphuretted hydrogen water. The ether dissolves the oleate and hypogoeate of lead, leaving the palmitate and arachidate unchanged. The residue is treated with hot diluted hydrochloric acid, and the liberated fatty acids allowed 1 Baudrimont recommends direct conversion to lead soaps by boiling the sample with 5 grammes of finely divided litharge and 100 c.c. of water. There is an objectionable tendency to the formation of a basic oleate of lead, only with difficulty soluble in ether. ARACHIDIC ACID. 107 to solidify, and separated from the solution of lead chloride. The cake is next dissolved in 50 c.c. of hot rectified spirit. On cooling the solution, abundant crystals of arachidic acid will be deposited if the sample contained earthnut oil. The liquid is filtered, and the crystals washed twice with 10 c.c. of cold rectified spirit, and then with spirit of 890 specific gravity, in which they are completely insoluble. The arachidic acid is next treated on the filter with boiling absolute alcohol, by which it is dissolved, and the resultant solution is evaporated to dryness and the residue weighed. To the amount thus found is added '0025 gramme for each 10 c.c. of rectified spirit used in the crystallisation and wash- ing of the acid, if the manipulation was conducted at 15 C. ; or a correction of *0045 gramme per 10 c.c. if at a temperature of 20 C. The fusion-point of the arachidic acid obtained in the above manner is 71 to 72, that of the pure substance being 7 5 '5. Renard obtained from 4 '5 to 5'0 per cent, of arachidic acid from earthnut oil, and the writer has isolated 5*5 per cent. Hence twenty times the weight of acid found (duly corrected for solubility as already described) will approximately represent the amount of the adulterant in the 1 grammes of the sample employed for the test. The process requires considerable skill to ensure accurate results. It proved unsuccessful with a mixture containing less than 4 per cent, of earthnut oil, but with one containing 10 per cent, of the adulterant the result was within 1 per cent, of the truth. Rape Oil. Colza Oil. French Huile de Navette. German Eapsbl; Kolsatol. (See also table on page 63.) This oil is prepared from the seeds of several species of the genus Brassica, belonging to the natural order Cruciferse. The seed is commonly subjected to steam-heat before pressure, to coagulate the albuminous matter and facilitate the extraction of the oil. When freshly expressed, rape oil is a yellowish-brown or brownish-green viscid liquid, of a peculiar odour and pungent taste, owing to the mucus and other foreign and colo.uring matters invariably present. These impurities become separated to some extent by keeping the oil, but cannot be removed wholly by pas- sive treatment. The foreign matters lessen the combustibility of the oil, and occasion much smoke during its burning. Brown rape oil or sweet rape oil is the commercial name for the oil as expressed from the seed. It is usually refined by treat- ment with sulphuric acid, sometimes supplemented by agitation with alkali, and of late years a current of steam has been success- fully applied. The refined oil is light yellow and almost odourless. 108 RAPE OIL. Some writers distinguish winter from summer rape oil, and both of these from colza oil, but these refinements are nearly obsolete and have but little practical interest. 1 Rape oil stands on the border-land between drying and non- drying oils. It does not thicken readily when heated and exposed to the air, 2 and yet gives but an imperfectly solid elaidin with nitrous acid. In non-drying characters, rape oil is decidedly inferior to olive oil, but superior in its smell and appearance to the lower qualities of the latter. Notwithstanding a slight tendency to gum, rape oil is extensively used for engine and machinery lubrication, as well as for burning in railway and safety lamps. Kape oil differs from the majority of vegetable fixed oils in consisting largely of the glyceride of brassic acid, to which the formula C 22 H 42 2 is attributed, and which is generally re- garded as a higher homologue of oleic acid. The relationship is, however, somewhat doubtful, the true analogue of oleic acid being more probably e r u c i c a c i d, an acid apparently isomeric with brassic acid, the glyceride of which is contained in the fixed oil of mustard. It is uncertain, however, whether brassic and erucic acids have been correctly described, and it is possible that they are really identical. At any rate, all the oils from the Cruciferx agree in containing glycerides of acids of very high 1 By some authorities the term colza oil is restricted to the finest and lightest kinds of oil expressed chiefly from German or East Indian seeds. The following differences exist between the varieties of rape oil, according to Schiibler and Lefebvre : Spec. Grav. at 15 C. Solidifying Oil Point C TJ i Scliiihler. Lefebvre. Schiibler. Winter rape 912-8 915-4 Below Summer rape . 913-9 9157 -8 to -10 More viscid than winter rape. Winter colza Summer colza . | 913-6 915-0 916-7 } - 6 { Produced largely in France. 2 C. T. Kingzett (Analyst, ix. 15), prepared the barium salts of the fatty acid from a sample of rape oil of 915 sp. gr. They fused when dry and were sol- uble in carbon disulphide, benzene, and ether, being precipitated from the last solution by ether. On boiling the reprecipitated barium salts with methylated spirit a portion remained undissolved, and from this a solid fatty acid was prepared. The portion soluble in boiling spirit gave on cooling a nearly white barium salt containing 18 '33 per cent, of Ba. Barium oleate contains 19 '59, and barium brassiate 16 '86 per cent, of Ba. The free fatty acid prepared from the barium salt showed no tendency to absorb oxygen ASSAY OF KAPE OIL. 109 atomic weight, and hence have corresponding high saponification- equivalents. (See pages 41 and 42.) Rape oil and other oils from the Cruciferae, are commonly stated to contain sulphur compounds, and to give rise to black silver sulphide on treating their ethereal solutions with a few drops of alcoholic silver nitrate. If the oil be boiled with a 10 per cent, solution of pure potash, an immersed silver coin becomes blackened. Although sulphur is undoubtedly present .sometimes, its existence appears to be due to accidental conditions. ASSAY OF COMMERCIAL RAPE OIL. Rape oil is subject to numerous adulterations, the more important of which can be detected with tolerable certainty. The spec rffe~g-r a v i t y of genuine rape oil averages 915 at 15 '5 C ( = 60 F.). Of 51 samples of genuine rape oil examined by L. A r c h b u 1 1, 7 had densities below 9 14*0, 25 between that point and 915*0, and 19 between 915*0 and 916*0. The extreme ranges of variation were 912*3 and 915'9. Boverton Redwood has communicated to the author the results obtained by the very careful determination of the density of 30 samples of brown rape oil known to be genuine. The figures range from 914*5 to 915*4, the average being 914*9. The experience of these observers and of the writer himself confirms the results of Archbutt and Red- wood, so that 91 6*0 may be regarded as the maximum for the density of genuine rape oil at 15*5 C. 1 The density of rape oil is a valuable indication of its purity, as all the ordinary adulterants are denser than the genuine oil, with the exception of mineral oil, which can be detected and estimated with accuracy by the method described on page 82. Foreign seed oils of more or less drying character, as sesame", sunflower, cress-seed, hempseed, cottonseed, or linseed oil, or possibly cocoanut olein, all have a density ranging between 920 and 937. Hence if the sample have a density of 918, it may possibly contain even 50 per cent, of these oils, while the smell and colour will be little affected. Seed and nut oils deteriorate rape oil by increasing its gumming properties, with the exception of earthnut oil and cocoa- nut olein, and the addition of either of these is improbable. Earthnut oil could be detected as in olive oil (page 106), and cocoanut olein would be indicated by the lowered saponification- equivalent of the sample. The viscosity of rape oil is a valuable indication of its 1 North German (Baltic) rape oil is usually somewhat denser and less pure than the French and Belgian products. The seed crushed in England, im- ported from the East Indies and all parts of Europe, gives an oil varying in density from 913 to 916. Black Sea rape oil is usually of inferior quality. 110 EXAMINATION OF EAPE OIL. purity, as it is moderately constant and exceeds that of any oil likely to be used as an adulterant. The sample should always be compared with a specimen of rape oil known to be genuine, or with pure glycerin diluted to 1226*0 specific gravity, which at 15'5 C. has the same viscosity as average rape oil. The solubility in acetic acid (page 25) of genuine rape oil ;s so slight that equal measures of the two liquids are not miscible at 120 C. This peculiar behaviour distinguishes the oils from the Cruciferae, from all other fixed oils hitherto examined by the test. The saturation-equivalent of genuine rape oil, as ascertained by operating strictly in accordance with the instruc- tions on page 44, averages 324, and ranges from 330 to 318, as an extreme and rarely met with figure. The presence of certain admixtures can therefore be assumed if a still lower figure is obtained. On the other hand, if the saturation-equivalent exceed 330 a hydrocarbon oil is probably present, and should be searched for as on page 8 1. 1 The iodine-absorption (page 48) of rape oil ranges from 97 to 105 per cent., being slightly less than that of cotton or sesame oil, and considerably below T that of the more strongly drying oils. On exposure to heat in a watch glass at 100 C. for several days (see page 51) genuine rape oil slowly thickens and becomes darker, drying gradually at the edges. After continuous heating during four or five days it becomes very viscous but still remains fluid except at the edges. By comparing in this way, side by side in the water-oven, the sample with a rape oil of known purity, a very useful indication is obtainable. 2 The increase of temperature on treating genuine rape oil with strong sulphuric acid in the manner prescribed on page 53, averages 59 C., the extreme variations being, according to L. Archbutt, from 55 to 64. B. Redwood, doubtless owing to some difference in the method of manipulation, finds an average rise of 66 C. Any greater rise than corresponds to that normally 1 Refined rape and colza oils have been frequently adulterated with purified mineral oil. This addition greatly interferes with the burning qualities of the oil, causing it to smoke and form much deposit on the wick. The unsaponifiable matter naturally present in rape oil was found by B. Redwood to range from 0'18 to I'OO per cent. L. Archbutt has occasionally found a somewhat larger proportion. 2 L. Archbutt found that genuine rape oil exposed in a thin film on a slip of glass, at the ordinary temperature, was still liquid, though viscous, at the end of two years. ADULTERATION OF RAPE OIL. Ill yielded by rape oil under the conditions of the experiment may be due to an admixture of cotton, hemp, or linseed oil. If the nature of the admixture can be otherwise ascertained, the proportion of the adulterant can be deduced with tolerable accuracy from the rise of temperature. With the el ai din- test (page 57) rape oil behaves in a peculiar and somewhat characteristic manner. Solidification occurs very slowly, but after 50 to 60 hours the oil is fre- quently converted into a pasty mass, which is sometimes yellow, and in other cases orange-red or mottled. Frequently a separation into a solid portion and oily liquid occurs. The results are much influenced by the temperature. At 10 C. many samples become solidified in appearance, but on being touched with a glass rod are seen to be a peculiar mixture of solid' and liquid. On im- mersing the bottle containing the product formed at 10 for a short time in water at 15 C., the elaidin forms a thick liquid. The colour -tests with sulphuric and nitric acids (pages 59, 61, and 100) and certain other reagents are of value for the detec- tion of certain admixtures, such as linseed and fish oils. Eichter states that on shaking 5 c.c. of the sample with 1 c.c. of a solution of soda of 1*34 specific gravity, pure rape oil forms a dirty white milky fluid; honjt nil a brownish-yellow thick soap ; and train oil a dark red solution. The melting point of the fatty acids from rape oil affords a valuable indication in some cases. The acids from genuine oil fuse at a temperature of 18 to 21 C., and solidify at about 12. An admixture of linseed oil renders them more fusible, while the acids from cottonseed oil have a much higher melting point. Fish oils are recognisable in rape oil by their taste and odour on warming, and by the colorations developed with soda and sulphuric acid. Tram oil is said to be best detected by agitating 100 drops of the oil with 1 of sulphuric acid, when the depth of the red coloration will follow the proportion of the adulterant present. Cottonseed oil is one of the commonest adulterants of rape oil. It lowers the saturation- equivalent, raises the melting point of the oil and the derived fatty acids, reduces the viscosity, and increases the density and the temperature on treatment with sulphuric acid. If refined cotton oil, previously deprived of its stearin, has been used as the adulterant, the higher melting points of the oil and fatty acids will be less marked. Linseed oil is a very common and objectionable adulterant of rape oil, from 10 to 50 per cent, being often added before re- fining. Its presence is recognisable by the increase in the density, solubility in acetic acid, drying characters, temperature 112 COTTONSEED OIL. with sulphuric acid, and iodine-absorption of the sample, and by the decreased viscosity and saponification-equivalent. The fatty acids are more readily fusible, and the colour-reaction with sulphuric acid is modified. Hedge-mustard oil (from Raphanistrum arvense), according to E. V a 1 e n t a, is used for adulterating rape oil, which it closely resembles. The most characteristic reaction is said to be the pro- duction of a green colour when the oil is treated with a quantity of alcoholic potash insufficient for its complete saponification, and the filtered liquid strongly acidulated with hydrochloric acid. Oleic acid is the only adulterant (except mineral oil and hedge- mustard oil) which could be added to rape oil without tending to increase the density. The proportion of free (oleic) acid naturally present in rape oil ranges from 0*5 to 5 per cent. Hence, if it be determined as on page 76, any excess above 5 per cent, may be regarded as due to adulteration. The presence of even a compara- tively small proportion of free acid has an injurious influence on the burning qualities of rape oil, especially in certain kinds of lamps. Free mineral acid (page 75) is not unfrequently present in rape oil, owing to its imperfect removal during purification. Its presence is highly objectionable in oil intended for lubrication or for greasing steel goods. Cottonseed Oil. French Huile de Coton. German Baumwollensamenol. (See also tables on pages 64 and 92.) Cottonseed oil is now expressed in enormous quantities in the United States, on the Continent of Europe, and in Great Britain. CRUDE COTTONSEED OIL has a density ranging from 928 to 930. The oil as expressed from the seeds contains in solution, often to the extent of 1 per cent., a peculiar colouring matter which is characteristic of this oil and its seed, and which gives the oil a ruby -red colour, sometimes so intense as to cause the oil to appear nearly black. Crude cottonseed oil gives a very bright red coloration with strong sulphuric acid (page 59). When boiled with an alkaline solution, alcoholic potash being preferable for laboratory experi- ments, crude cottonseed oil is saponified, and the resultant soap rapidly oxidises on exposure to air with production of a fine purple or violet-blue coloration. 1 This reaction is characteristic of crude 1 "Cottonseed blue" is stated by Kuhlmann to have the composi- tion of C 17 H 24 4 . It is amorphous ; readily destroyed by oxidising agents ; in- soluble in water, diluted acids, and alkalies ; sparingly soluble in carbon disulphide and chloroform, but more readily in alcohol and ether ; and dis- solves with purple colour in strong sulphuric acid. The unoxidised colouring COTTONSEED OIL.^^^TL v V**^^\ 1 a cottonseed oil. The colouring matter causes crude cottonseed oil to produce stains, and hence is removed by a process of refining. This is usually effected by agitating the crude oil at the ordinary temperature with 10 to 15 per cent, of solution of caustic soda of 1060 specific gravity, when the alkali combines with the colouring matter and saponifies a portion of the oil. The mixture becomes filled with black flocks which deposit on standing, 1 and leave the oil but slightly coloured. The loss in refining is usually from 4 to 7 per cent., but occasionally amounts to 12 or 15. Hence it is desirable, before purchasing crude cottonseed oil for refining, to ascertain by a laboratory experiment what the percentage of loss is likely to be. Frequently the treatment with alkali is only carried far enough to remove the major part of the colouring matter, the oil being then boiled with a solution of bleaching powder, and subsequently treated with dilute sulphuric acid. 2 EEFINED COTTONSEED OIL is of a straw or golden-yellow colour, or occasionally nearly colourless. The density ranges from 922 to 926, and the solidifying point from 1 to 10 C. By subjection to cold and pressure a certain proportion of stearin is separated, the melting point of the residual oil being correspondingly lowered. Kefined cottonseed oil is usually very free from acid, and when properly prepared is of pleasant taste and admirably adapted for edible and culinary purposes, for which it is now extensively em- ployed, both with and without its nature being acknowledged. It is now substituted for olive oil in some of the liniments of the United States Pharmacopoeia, but its principal applications are in soapmaking and the manufacture of factitious butter. Cottonseed oil gives but an imperfectly fluid elaidin with nitrate matter of cottonseed oil has been recently examined by J. L o n g m o r e, who, in a communication to the author, states that it is a pungent golden-yellow product, insoluble in water, but soluble in alcohol and alkaline solutions, and precipitated from the latter on addition of acids. It dyes well and per- fectly fast on both wool and silk. 1 The deposit thus formed, consisting of colouring and albuminous matters, alkali, and partially saponified oil is technically called " mucilage." It is decomposed with a slight excess of acid, and the resulting dark-coloured grease is heated to a temperature of 120 C. (= 250 F.) with concentrated sulphuric acid, which renders insoluble the colouring matters, &c., while the impure fatty acids rise to the surface. On distilling these with superheated steam, a mixture of fatty acids is obtained which is separated into stearic and oleic acids by pressure. The " cottonseed stearin " thus obtained is employed for making soap and composite candles, as also for adulterating tallow, &c. 2 This method of treatment is economical, but causes the oil to acquire an unpleasant taste and smell which cannot be removed. VOL. II. H 114 SESAM^ OIL. of mercury. The fatty acids produced by its saponification have a remarkably high melting point (38 C.). The colour-reactions with sulphuric acid and alkali so characteristic of crude cottonseed oil are produced imperfectly or not at all by the refined oil, according to the treatment to which it has been subjected. Cottonseed oil is not itself very liable to sophistication, but the means of identifying it have a special interest and importance, owing to' the frequency with which it is employed to adulterate other oils, especially olive, rape, and linseed oils. It may be detected in either of these by the density, aided by the colour-tests given above and on pages 61 and 100. The results of the elaidin- test, with determinations of the iodine-absorption, rise of tempera- ture with sulphuric acid, and melting point of the fatty acids, enable the proportion of cottonseed oil in a mixture to be approxi- mately determined. COTTONSEED STEARIN is, properly speaking, the solid fat sepa- rated from cottonseed oil by cooling and pressing. A product so obtained is stated to be employed for the manufacture of butter- surrogates, and to have nearly the same density as butter fat. But by far the greater part of the article known in commerce as " cottonseed stearin " is simply impure stearic acid from cotton- seed oil. This is commonly obtained by the method given in outline in the footnote on page 113. The crude oil expressed from decorticated cottonseed is sometimes very rancid and semi-solid at the ordinary temperature from the separation of solid fatty acids in the free state. By pressure it would yield a product similar to that obtained by distillation. Sesame Oil. Teel Oil. Gingili Oil. French Huile de Sesame. German Sesamol. (See also tables on pages 64 and 92.) Sesame oil, sometimes called benne oil, though distinct from the oil of ben or ~behen, has a yellow colour, usually of a deeper hue than expressed almond oil, is thinner than the majority of oils, is nearly odourless, and has a bland and agreeable taste. The oil expressed from the seeds congeals at about 5, but that extracted by solvents at about + 5 C. Sesame oil consists of about 76 per cent, of olein, with smaller proportions of myristin, palmitin, and stearin. A small quantity of a peculiar, probably resinous, substance may be extracted from the oil\jby agitation with alcohol or glacial acetic acid. The acetic solution has a blue colour, changing to greenish-yellow, on addition of a cold mixture of equal weights of sulphuric and nitric acids. Sesame oil is an imperfectly drying oil, and does not readily LINSEED OIL. 115 turn rancid. It resembles cottonseed oil, but is distinguished by its behaviour with colour-tests (pages 61, 100, and 102), that with sugar and hydrochloric acid being especially delicate and charac- teristic. Concentrated sulphuric acid converts it into a brownish- red gelatinous mass. German sesame oil is a name sometimes given to came- lina oil (page 64). Linseed Oil. French Huile de Lin. German Leinol ; Leinsamenb'l. (See also table on pages 65 and 92.) Linseed oil is the oil expressed from the seeds of Linum usitatissimum or flax-plant. Flax is commonly grown in India as a mixed crop with mustard and rape, and hence the oil from Indian linseed is never perfectly pure. In the Black Sea ports it is the practice to add 1 measure of hemp to every 19 of linseed, and adulteration is also conducted in much more considerable proportions. The varieties of linseed oil recognised in commerce are raw, refined, artist's, and boiled oil. Linseed oil is usually refined by agitating the raw oil in lead-lined tanks with about 1 per cent, of concentrated sulphuric acid (specific gravity 1845), and washing the product by boiling it with water, with or without open steam. After settling, the water and foots are run off from the refined oil. 1 Boiled oil is described on page 119. Freshly expressed linseed oil is a brownish or yellow liquid, having a smell and taste suggestive of linseed. 2 The specific gravity of the pure oil is generally about 935, but may vary from 932 to 937. It becomes thicker when cooled, and solidifies at about 27 C. to a yellowish mass. Linseed oil imparts a yellow 1 To prepare artist's oil, raw oil is allowed to stand for weeks or even months to cause impurities to settle, and then treated with litharge or lead acetate. It is then bleached by exposure to sunlight. Various secret methods of treatment are employed. Sulphate of iron or zinc is sometimes used, and is said to hasten the deposition of impurities. The lead is often separated by sulphuric acid, which forms a precipitate of lead sulphate which carries down the impurities. Livache treats the oil with metallic lead and removes the lead which passes into solution by means of a solution of sulphate of zinc, man- ganese, &c. , whereby lead sulphate is precipitated, and an oxide of the other metal remains in solution. 2 The oil obtained from the seeds by cold pressure has a golden yellow colour and a peculiar bland taste ; that obtained by hot pressure varies in colour from amber-yellow to yellowish-brown, has a more or less acrid taste, and possesses a stronger odour than the cold-pressed oil. 116 LINOLEIC ACID. colour to alcohol when agitated with it, and dissolves in about 40 measures at the ordinary temperature or in 4 or 5 at the boiling point of the spirit. Linseed oil produces great heat when treated with concentrated sulphuric acid, and is inflamed by fuming nitric acid. It does not yield a solid product under the influence of nitrous acid. Linseed oil is the most important of the class of drying oils. Its applications in the arts, as in the manufacture of paint, varnish, oilcloth, printing ink, &c., are all based on its property of drying on exposure, a character which is more fully considered on page 119. In consequence of its tendency to combine with oxygen, linseed oil evolves much heat when exposed to the air in a finely divided condition, the action being sometimes so violent as to cause the inflammation of cotton-waste or similar material saturated with the oil. Linseed oil is said to consist of about 80 per cent, of linolein, with smaller proportions of olein, myristin, and palmitin, the two latter fats together amounting to about 10 per cent. 1 The linolein, or tri-linolein, which is the characteristic constituent of linseed and probably other drying oils, is the glyceride of linoleic acid. LINOLEIC ACID was isolated by Schiller in the following man- ner: Linseed oil was saponified with solution of caustic soda, and the soap purified by repeatedly salting out. The aqueous solu- tion of the soap was then precipitated by calcium chloride. 2 From the well- washed precipitate the calcium linoleate was dissolved out from the salts of the solid fatty acids by ether. The ethereal solution was decomposed by agitation with cold hydrochloric acid, and the ethereal layer separated and distilled at as low a tempera- ture as possible in a current of hydrogen. The residual acid had a dark-yellow colour, and was further purified by dissolving it in alcohol, saturating the solution with ammonia, and then precipitating with barium chloride. The barium linoleate thus obtained was washed, pressed, and repeatedly recrystallised from ether, and then converted into the acid by a treatment corresponding to that de- scribed for the calcium salt. The acid was dried in a vacuum over sulphuric acid and a mixture of ferrous sulphate and lime. Linoleic acid is a thin oily liquid, of faint yellow colour. It is stated to remain liquid at 18 C., and at 14 C. has a density of 920'6. It is said to possess a faintly acid reaction, and to have 1 P o p p y oil has a similar constitution to linseed oil. Walnut oil is said to be free from solid glycerides. 2 Oudeaianns precipitates the sodium soap with calcium chloride in a strongly ammoniacal solution. HOMOLINOLEIC ACID. 117 a taste which is at first pleasant and afterwards harsh. Linoleic acid does not form a solid product on treatment with nitrous acid. With nitric acid it swells up considerably and yields a greasy resin, suberic acid, C 8 H 14 4 , and a little oxalic acid. The formula attributed by Schuler to linoleic acid from linseed oil is C 16 H 28 2 , and his results were confirmed by Mulder, while Oudemanns" obtained from poppy oil an acid of the same composi- tion. Although this may have been the formula of the pure acid analysed by these chemists, there is good reason to believe that the acid, the glyceride of which constitutes the principal portion of linseed and other drying oils, is a higher homologue of linoleic acid, probably containing 18 atoms of carbon, and hence having the formula C 18 H 32 2 . For this hypothetical acid the author suggests the name of homolinoleic acid. 1 On exposure to air linoleic acid is said to absorb oxygen, becom- ing thick and ultimately so viscid as scarcely to flow, but remains i Carbon. Hydrogen. Oxygen. C 16 H 28 2 requires ... 7619 ... 1111 ... 1270 Ci 8 H 32 2 requires ... 77'U ... 11 '43 ... 11 -43 There is, therefore, only a difference of 1*05 per cent, in the carbon and 0'32 per cent, in the hydrogen of the two acids. Both Schuler and Oudemanns found that the linoleates usually contained less than the theoretical proportion of base, a fact which they attributed to the formation of acid salts, but which may have been due to the combining weight of the fatty acid having been under-estimated. By titration with standard alkali the writer has found the fatty acids from several samples of linseed oil to have mean combining weights ranging between 282 and 295, the combining weight of an acid of the composition C 18 H 32 2 being 280, while that of the 16-carbon-atom acid is only 252. In one in- stance the linseed oil acids, prepared with great care in an atmosphere of coal-gas, had a combining weight of 307 '2 (C 20 H 36 2 = 308). Further, the proportion of glycerol produced by the sapoiiification of linseed oil (see page 33) ranges from 9 '4 to 10 '0 per cent., the theoretical quantity producible from triliuolein being 11 '58, and from trihomolinolein 10 '48 per cent, (page 31). Again, the molecular weight of the glyceride C 3 H 5 ;(O.C 16 H 27 0) 3 would be 794, and its saponification-equivalent (page 40) 264 '67, the corresponding figures for olein, myristin, and palmitin being respectively 294 '67, 226 '67, and 268-67, the mean of the three being 263 '34. The saponification-equivalent of linseed oil is found in practice to range from about 287 to 300 (see page 42), and the equivalents of other drying oils are all contained within the same limits. The saponification-equivalent of "homolinolein," C 3 H 5 \ (O.C 18 H 31 0) 3 , is 292*67, so that its presence in linseed oil as the leading con- stituent is extremely probable. The following figures show the ultimate percentage composition of linseed 118 LINOXYN. unchanged in colour. 1 The change is not attended with evolution of carbon dioxide. When spread in a thin layer on wood and exposed to the air, linoleic acid forms a varnish, but on glass only becomes tough. The product is said to have the composition of a hydrate of oxylinoleic acid, C 16 H 26 3 ,H 2 0. When heated to 100 this gives off 6 '7 per cent, of water and becomes blood-red. By prolonged contact with air, and more quickly if frequently moist- ened with ether, colourless oxylinoleic acid loses its viscid consist- ence, and is converted into a body called 1 i n o x y n. LINOXYN on analysis yields figures corresponding to the formula C 32 H 54 11 . It is a neutral, amorphous, highly elastic mass, re- sembling caoutchouc. It is heavier than water, and is insoluble in water, dilute acids, alcohol, or ether; but swells up and dis- solves in a mixture of alcohol and chloroform. In warm solution of caustic potash, and more slowly in ammonia, it dissolves to a red liquid, which, when supersaturated with an acid, yields a yellowish-red, flocculent precipitate, soluble in alcohol, and still more in ether, exhibiting the composition and properties of oxy- linoleic acid. LINOLBATES. The salts of linoleic acid are difficult to obtain pure. They are white, mostly uncrystallisable, become coloured on exposure to air, and are soluble in alcohol and ether. Linoleate of potassium or sodium, containing an excess of alkali, absorbs oxygen greedily and becomes yellow and dry when exposed in a finely divided state to the air. It then dissolves in water with dark brownish-red colour, and gives, on addition of hydrochloric acid, a brown greasy resin. The ethereal solution of lead linoleate, when evaporated on a glass plate, leaves a white amorphous residue of and poppy oils as ascertained by combustion, compared with the theoretical figures yielded by the pure glycerides. Carbon. Hydrogen. Oxygen. Tripalmitin (C 51 H 98 6 ), Triolein (C 57 H 104 6 ), ... Trilinolein (C 51 H 86 6 ), ... 75-93 77-38 77-08 12-16 11-76 10-83 11-91 10-86 12-09 Trihomolinolein (C 57 H 98 6 ), 77-90 11-16 10-94 Sacc ; linseed oil, 78-11 10-98 10-93 Konig ; linseed oil, 77-40 11-10 11-50 Cloez-; linseed oil, 77-57 11-33 11-10 ,, poppy oil, 77-50 11-40 11-10 These figures are not very satisfactory, but they agree quite as well with homo- linolein as with liuolein. The probability is that several homologous acids are frequently present, that with 18 carbon atoms predominating in most cases. 1 W. Fox (Analyst, viii. 116) states that crude linoleic acid absorbed no trace of oxygen when kept for six days at 105 C. BOILED LINSEED OIL. 119 the lead salt of oxylinoleic acid. The acid separated from this salt by sulphuretted hydrogen, and dissolved in alcohol, remains on evaporation as a nearly colourless viscid mass, which becomes blood-red without change of composition when heated to 100 or treated with acids or alkalies. The colourless alcoholic solution of oxylinoleic acid is not altered by carbonates of alkali- metals at the boiling heat, but caustic alkalies turn it red even at ordinary temperatures. OXIDATION OF LINSEED OIL. The most characteristic and valu- able property of linseed oil is that of taking up atmospheric oxygen, and becoming thereby converted into a tough or hard varnish. The tendency of linseed oil to oxidise is much enhanced by heating it to a high temperature (from 130 C. upwards) while passing a current of air through or over the oil, and subsequently increasing the temperature until the oil begins to effervesce from evolution of products of decomposition. The heating is sometimes effected by direct application of a fire to the bottom of the metallic vessel containing the oil, but a preferable and safer plan is to employ steam. The process is termed "boiling." The oil thus treated is called "boiled oil." By continued "boiling," the oil becomes very thick and may be drawn out into elastic threads, which are very sticky, but do not produce a greasy stain on paper. This product is used in the manufacture of printing ink. By adding litharge, red-lead, ferric oxide, or manganese dioxide or hydrate during the process of boiling, the oxidation and consequent drying of the product is still further facilitated. The nature, pro- portion, and mode of adding these substances is usually kept jealously secret. Lead acetate and manganous borate are among the most approved. (See Oil and Colourman's Journal, iv. 560.) The action of some at least of these "driers" (e.g., compounds of man- ganese) seems to be that of carriers of oxygen, while litharge dissolves in the oil and acts partly as a carrier of oxygen and partly as the base of certain salts which oxidise very rapidly. W. Fox suggests that driers hasten the decomposition of the linoleic acid with formation of secondary products of acid character which possess the power oi combining with metals without evolving hydrogen. It is to those secondary products he attributes the absorption of oxygen. The chemical changes which occur in the boiling and drying of linseed oil are very imperfectly understood. According to M u 1 d e r, part of the linolein is decomposed during the boiling with forma- tion of linoleic anhydride. 1 The glycyl-radical is said to 1 Or more probably a more highly oxidised body, such as oxylinoleic acid. According to W. Fox (Oil and Colourman's Journal, v. 1404) the 120 OXIDATION OF LINSEED OIL. be oxidised with formation of carbon dioxide, water, and acetic and formic acids, and finally an elastic mass remains, consisting of 1 i n o x y n, mixed with oxylinoleic acid, and more or less changed oleic and other fatty acids. 1 In presence of metallic oxides the varnish will also contain linoleates or oxylinoleates. The state- ments of Mulder are probably too sweeping. Thus the writer has found, by the permanganate method, 9 '9 4 per cent, of glycerin to be produced by the saponification of genuine linseed oil which had been boiled by the steam process ; and from the same sample he isolated 8*8 per cent, of nearly pure glycerin. From the elastic skin produced by the drying of linseed oil the author isolated, with some trouble, 4'9 per cent, of impure glycerin, while the same sample analysed by the permanganate process yielded oxalic acid equivalent to 15*5 per cent, of glycerin. The change of composition undergone by 100 grammes of lin- seed and poppy oils by exposure to air during 18 months was found by C 1 o e z to be as follows : Linseed Oil. Poppy Oil. C. H. 0. C. 77-50 71-38 H. 11-40 10-64 0. Composition of original oil, Composition after 18 months, . . Difference, . 77-57 72-27 11-33 10-57 11-10 24-16 11-10 25-08 -5-30 -0-76 + 13-06 -6-12 -0-76 + 13-98 The quantity of oxygen absorbed was greater than that given off in the form of carbon dioxide, water, &c., and the oil finally showed a considerable increase in weight. The action of light is not essential, but was found considerably to facilitate the change, the more refrangible rays having the greatest influence. In the dark, the chemical change is induced very slowly, but when once begun it proceeds rapidly. 2 glycerides of the oil are decomposed during the boiling, oxidation products are formed by the fatty acids, and the glycerin splits up into acids of the acrylic series, forming the irritating vapours which always accompany oil-boiling. Acetic and formic acids are prominent constituents of these vapours. 1 The insoluble fatty acids are lowered to a considerable extent by oxidation, the soluble being increased. 2 According to Mr T. Duggan, to whom the writer is indebted for numerous specimens and much valuable information on linseed oil and allied subjects, the oil thickens in the dark, but loses its drying power in some measure, regaining it on subsequent exposure to light and air. ASSAY OF LINSEED OIL. 121 Livache (Compt. Rend., xcvii. 1311 ; Jour. Ch&m. Soc. t xlvi. 532) finds that the oxidation of a drying oil is accelerated at a temperature of 50 to 60, partly because the oil becomes more fluid, and partly because its affinity for oxygen is greater. When a drying oil containing oxide of manganese in solution is dissolved in an equal measure of benzene, and agitated with air in a closed vessel, rapid absorption of oxygen takes place, especially at a temperature of 40 to 50 C. If the supply of air be repeatedly renewed, the liquid becomes thick, and on distilling off the solvent a residue is obtained which solidifies on cooling to a dry and per- fectly elastic solid. By limiting the oxidation, various inter- mediate products are obtainable. 1 ASSAY OF GENUINE LINSEED OIL. Linseed oil is often sophisticated, but even when perfectly genuine its quality varies within wide limits. In practice, the best oil is that which dries most perfectly, but the rapidity of drying, and the consistency of the ultimate product, are most important factors in judging of the quality of linseed oil. 2 Thus the dried oil may be tough, very elastic, hard and brittle, or rotten. An oil giving a hard product is to be preferred, as elasticity can be readily imparted in the after-treatment if required. 1 The last product is characterised by its remarkable elasticity, and its absolute insolubility in water, alcohol, and ether. It is almost instantly saponified by caustic potash in the cold ; and on subsequent separation of the fatty acids it is found that the solid acids have undergone no alteration, whilst the liquid fatty acid has almost entirely disappeared, and has been con- verted into viscous products, characterised by their solubility in water and by the various salts which they form. 2 It has been pointed out by W. Fox (Oil and Colourman's Jour., iv. 214) that linseed oil of the best quality is less readily obtainable than formerly, probably partly on account of the seed being badly dressed, and hence con- taining an unusual admixture of seeds yielding non-drying oils, but that the chief cause of the deterioration is the changed practice of the crushers, who now by using improved machinery leave only some 5 or 6 per cent, of oil in the expressed linseed-cake, whereas it was formerly usual for the cake to contain from 10 to 12 per cent, of oil. The oil last expressed is of inferior quality, and Fox suggests that it should be kept separate from the rest of the oil. He further points to differences in the temperature of the vessels in which the seed is heated prior to pressing as causing probable variations in the quality of oil by affecting the proportion of so-called "albuminous matters" contained in it. These albuminous matters are coagulated when the oil is subsequently "boiled," and unless the process is unduly prolonged are liable to cause loss by frothing and boiling over. Fox states that the " albuminous matter " contains no nitrogen. 122 ASSAY OF LINSEED OIL. Raw oil, intended for making pale boiled oil or varnish, should not have a density much below 935, or it will be apt to contain a notable proportion of foreign seeds, &c.; 3 per cent, of such admixtures is the maximum allowable in linseed to be used for producing this class of oil. Various methods of judging of the quality of linseed oil have been proposed, but few, if any, are thoroughly satisfactory. The most rational, perhaps, are those in which an attempt is made to imitate the practical application of the oil by a laboratory ex- periment. W. Fox recommends that 50 c.c. of the oil should be heated in a beaker to 260 C. ( = 500 F.), when 2*5 grammes of powdered and dried ferric oxide (rouge) should be carefully stirred in, and the temperature then increased to 288 C. ( = 550 F.), l when the oil is allowed to cool to about 232 C. ( = 450 F.), and filtered through a dried filter. He then dries 0'2 gramme of the oil on a slip of glass in the water-oven, and notes the increase of weight, which may vary from O'OOl to 0'016 gramme. The small quantity of oil oxidised necessitates great care in the manipulation and weighing, and, in the opinion of the writer, the mere deter- mination of the increase in weight, or, as proposed by Fox in a subsequent paper, the measurement of the oxygen absorbed, is not a trustworthy indication of a drying oil ; for it is evident that an oil which has already taken up a considerable proportion of the possible oxygen (or, in other words, is well advanced on the way to dry- ness) will be indicated as inferior, though it may actually be a better oil than one absorbing more oxygen through being fresh. J. Muter tests the drying characters of linseed oil by flooding a plate of glass with the oil (which, if desired, may have been previously boiled and treated with oxide of iron) in the same manner as is done with collodion. The slip of glass, which is ten inches long by two broad, is then exposed in a suitable drying chamber to a temperature of 38 C. ( = 100 F.), a good current of air being caused to pass over it, and the time noted which is necessary to cause the oil to set so that the coating will not come off when lightly touched with the finger. By applying the finger at intervals to successive portions of the film the progress of the drying can be readily observed. A simple practical test for linseed oil is to mix the sample wit three times its weight of genuine white lead, and cover a perfectly clean glass or metal surface with the paint. An exactly simil experiment is made simultaneously with a standard sample, an< 1 An oil unsuited for floorcloth -making will not bear heating to 550 F. without boiling over. EXAMINATION OF LINSEED OIL. 123 the rates of drying and characters of the coating of paint com- pared. Very small admixtures of rape or other non- drying oils retard the drying considerably. The iodine-absorption (page 48) of an oil appears to increase with its drying powers, and hence the determination could probably be employed with advantage for ascertaining the quality of linseed oil. The temperature-reaction with sulphuric acid appears to vary somewhat with the character of a linseed oil. Thus J. Baynes (see footnote on page 54) has communicated the fol- lowing figures to the author : Rise of Temperature C. Baltic linseed oil, two years old, extra good for varnish, &c., 124 Another similar sample, . . . . .123 Old sample, from English seed, . . . .115 Russian oil, ...... 113 La Plata oil, ...... 112 Fresh oil, from East Indian seed, . . . 104 The nature of the driers added to linseed oil can be generally inferred from an examination of the ash left on burning 100 grammes of the sample, a little at a time, in a porcelain dish. The residue should be specially tested for lead, copper, zinc, iron, manganese, borates, &c. Sulphates, acetates, borates, and most other salts may be detected by agitating the original oil with a solution of sodium carbonate, separating the aqueous portion, and examining it for salt-radicals in the usual way. DETECTION OF ADULTERATIONS OF LINSEED OIL. Linseed oil is liable to be adulterated in a variety of ways. Of foreign seed-oils, cotton and nigerseed oils are most used; menhaden and other fish oils are not unfrequently added ; mineral and rosin oils, often both together, are largely used ; and rosin itself is also added. The drying and oxygen-absorption tests de- scribed on the previous page are valuable as indications of quality, and hence probable adulteration, but it must be borne in mind that genuine linseed oil varies much in its behaviour under these tests. The density of genuine raw linseed oil lies between 932 and 937, while that of the boiled oil varies from 939 to 950. Mineral and all foreign seed oils are lighter than linseed oil, while sin and rosin oil are much heavier. By the judicious use of a 5uitable mixture of mineral and rosin oils, extensive adulteration ian be effected without alteration of the density. The solidifying point of pure raw linseed oil is about 27 C., but samples containing other seed oils solidify at a TO. 124 ADULTERATIONS OF LINSEED OIL. higher temperature. The same remark applies to the relative fusibility of the fatty acids, those prepared from cottonseed oil having an exceptionally high melting point. The iodine-absorption (page 48) is a valuable test for, and method of determining the proportion of, a seed oil in linseed oil, provided that other adulterants are absent. Thus raw linseed oil assimilates from 155 to 160 per cent, of iodine, while cottonseed oil takes up only 105 to 109 per cent. Certain fish oils absorb fully as much iodine as does linseed oil. The rise of temperature on treating the oil with strong sulphuric acid (pages 53 and 123) is also a useful test for linseed oil, which gives more heat than any other seed oil; though it is equalled and even exceeded in this respect by some of the fish oils. The sulphuric acid colour-test described on page 59 is a useful indication of the purity of linseed oil. With a genuine sample a dark-brown clot is formed ; if rosin oil or fish oil be present a reddish-brown spot quickly forms, which in the former case retains its red tint for a long time, whilst a peculiar scum forms over it. This test is also applicable to the detection of rosin oil in boiled linseed oil, while the reaction is more rapid. Fish oils may also be detected by the darkening produced by passing a rapid stream of chlorine through the oil, and by the reddish colour produced by boiling the oil with an alcoholic solution of caustic soda. They are further recognisable by the taste and the smell of the sample on warming, and by the peculiar scum which rises when such oil is heated to boiling. As a test for cod oil, which is not unfrequently used in the case of linseed oil intended for the preparation of printing ink, A. Mo re 11 recommends the following test : 10 grammes of the oil are well agitated with 3 grammes of common nitric acid, and the whole left to stand. With pure linseed oil the colour will change during the stirring to a sea-green colour, afterwards becoming dirty greenish-yellow, whilst the acid assumes a light yellow colour. In presence of even 5 per cent, of cod oil, after standing some time the oil is said to acquire a dark brown colour, while the acid is tinged orange or dark yellow, according to the proportion of the adulterant present. A similar test has been described by A. Conrath for the detection of rosin oil. Chinese or Japanese wood oil (page 66) is distinguished by the very hard black clot it gives with sulphuric acid, by its low saponification-equivalent (266), and by yielding a highly coloured semi-solid product with the elaidin-test. If heated for a short time to about 300 C., the oil becomes a nearly solid transparent jelly, the change occurring either at once or on cooling. ROSIN IN BOILED LINSEED OIL. 125 Hydrocarbon oils are largely employed for adulterating linseed oil. They may be determined with accuracy as described on page 83. A mixture of mineral and rosin oil is frequently used, rosin itself being sometimes added in addition. The mineral oil is usually of low density (865 to 880), as the heavier oils are of too greasy a nature. The rosin oil employed for adulterating linseed oil is free from smell even when heated, but has a peculiar taste which is not masked by the linseed oil. The presence of rosin oil causes linseed oil to remain " tacky " for a long time, and prevents it ever becoming hard. The analysis of a sample of boiled linseed oil which, in addition to containing various mineral additions and free fatty acids, is also adulterated with rosin, rosin oil, and mineral oil, is a very complex problem of proximate chemical analysis. The general method to be pursued in examining such mixtures is indicated in the table on page 87, but the following plan is better adapted for the analysis of boiled linseed oil. The substantial accuracy of the results yielded has been established in the author's laboratory. 25 grammes of the sample of oil should be shaken in a separator (fig. 19, p. 83) several times with dilute hydrochloric acid. The aqueous liquid, which may contain lead, zinc, manganese, borates, and other mineral additions, is separated from the oily layer, and the latter is washed by agitation with water till the washings no longer redden litmus. The oil is then treated with rectified spirit, and the free fatty and resin acids titrated with standard alkali and phenol-phthalein as described on page 76. The neutral point having been reached, the alcoholic layer is separated from the residual oil, which consists of the neutral fatty oil (glycerides) and hydrocarbon oils of the original sample. These may be separated as described on page 82. The alcoholic solution is then concen- trated, water added, and any globules of oil dissolved by agitating with petroleum spirit. After separation from the aqueous liquid and evaporation of the solvent, the small residue of neutral oils may be weighed, and the amount found added to the main portion. The aqueous solution is then acidulated with dilute hydrochloric or sulphuric acid, when an oily layer is obtained, consisting of the free fatty and resin acids of the original sample, together with such additional amount as may have been formed by the decomposition of metallic soaps in the first stage of the process. This is separated from the aqueous liquid, washed with a little water, and filtered through wet paper. On subsequently drying the filter in the water-oven, the fatty acids pass through, and can be collected in a small tared beaker, the portion remaining on the filter being dissolved in ether, and treated as described on page 38. 126 CASTOR OIL. After weighing the fatty acids in the beaker, 1 gramme is treated by Gladding's process for the separation of fatty and resin acids (page 78). The weight of resin acids obtained is corrected by deducting 2 '31 milligrammes for each 10 c.c. of ethereal solution evaporated, this being a correction for the solubility of the silver compound of the acids from boiled linseed oil. 1 The resin isolated by the foregoing process is often viscous instead of hard, but its nature is distinctly indicated by its taste and the characteristic odour produced on heating it till it ignites and then blowing out the flame. The amount of resin thus found, subtracted from the mixed fatty and resin acids, gives that of the fatty acids alone. By agitating the original sample with alcohol, separating the spirituous solution for the undissolved oil, and titrating the former with standard alkali, the sum of the fatty and resin acids originally existing in the oil can be ascertained. Castor Oil. French Huile de Kicia German Eicinusol. (See also table on page 66.) Castor oil is the fixed oil expressed from the seeds of Ricinus communis, of which it constitutes nearly half the weight. If not perfectly clear, the oil is filtered, or treated with a small proportion of magnesia and animal charcoal. Castor oil is a transparent, colourless, or pale greenish-yellow liquid, having a faint odour and disagreeable taste. At a low temperature it thickens and deposits white granules, and at or about - 18 C. ( = F.) it solidifies to a yellowish mass. Castor oil is distinguished in its physical characters from all other natural fixed oils (except perhaps certain little-known oils from allied plants) by its very high density and viscosity, and by its ready solubility in alcohol and insolubility in petroleum spirit. These characters are of value for the assay of commercial samples, and are described below. Castor oil is stated to be optically active, some samples rotating to the right and others to the left. None of the specimens examined by the writer have possessed any optical activity. 1 The following is an example of the method of calculating the percentage of resin. 25 grammes of the sample gave 2'035 grammes of mixed fatty and resin acids. 1 gramme of these dissolved in 200 c.c. of ether, &c., gave a solution of which 120 c.c. yielded a residue of '354 gramme of impure resin by Gladding's process : Weight of residue, 354 '0 mg. Correction 2 '31 x 12, 277 Pure resin, 326'3 326-3 200 2-035 100 1000 X 120 X POOO X ~25 = 4 <42 P er Cent f KICINOLEIC ACID, 127 In its chemical composition castor oil is distinguished sharply from all other fixed oils, except curcas oil, and perhaps some other little-known oils. It consists of a mixture of solid fat, which is probably ordinary tripalmitin, with the glyceride of ricinoleic acid. 1 KICINOLEIC ACID, C 18 H 34 3 = C 17 H 33 O.COOH, may be prepared from castor oil by the method employed for the preparation of oleic acid from oils. Or castor oil may be saponified, and the solution of the soap fractionally precipitated with calcium chloride. The first third contains calcium palmitate, and should be rejected. The later fractions are purified by crystallisation from alcohol, and decomposed by dilute hydrochloric acid. Ricinoleic acid is a thick oily liquid, which solidifies below 0. It is insoluble in water, but is miscible in all proportions with alcohol and ether. The alcoholic solution has an acid reaction, an unpleasant, persistent, acrid taste, and does not oxidise in the air. Like oleic acid, it combines with Br 2 , and by treatment with nitrous acid is gradually converted into ricinelaidic acid, a body crystallising from alcohol in white needles, melting at 50 C., and forming an additive-compound with Br 2 . When heated with phosphorus, iodine, and water, ricinoleic acid yields an iodo-acid of the formula C 18 H 83 I0 2 . This is a yellow oil, which by the action of nascent hydrogen (hydrochloric acid and zinc) is con- verted into stearic acid, C 18 H 36 2 . "When distilled in a partial vacuum, ricinoleic acid yields oe nan thai or normal hep toi c aldehyde, C 6 H 13 .COH, and an acid of the acrylic series, C U H 22 2 . The reaction may be used for the detection of castor oil. For this purpose the oil should be saponified, and the fatty acids liberated and rapidly distilled in a small retort. The distillate is shaken with a saturated solution of acid sodium sulphite, the resultant crystals pressed, dissolved in a solution of carbonate of sodium, and the liquid distilled in a current of steam. The oenanthal will collect on the surface of the distillate as a highly refractive liquid, of peculiar aromatic odour, boiling at 154. QEnanthal is also produced by sub- jecting the alkali-metal salts of ricinoleic acid to dry distil- lation, but, if caustic soda be present in addition, sodium s e b a t e, C 10 H 16 Na 2 4 is formed, and methyl-hexyl c a r- binol, C 6 H 13 .C(CHV)H.OH, and methyl-hexyl ketone are found in the distillate. 1 C. R. A. Wright finds the mixed fatty acids from castor oil to have a mean combining weight ranging from 293 to 299, that of ricinoleic acid being 298. A sample of castor oil, analysed very carefully in the writer's laboratory, gave 9 '13 per cent, of glycerol, and 96 '17 per cent, of mixed fatty acids, of 306 "5 mean combining weight and 950*9 density at 15 '5 C. 128 ASSAY OF CASTOR OIL. Ricinoleic acid forms a series of salts, many of which are soluble in, and may be crystallised from, alcohol or ether. COMMERCIAL CASTOR OIL. The peculiar physical characters of pure castor oil distinguish it sharply from most other oils, but it is liable to certain adultera- tions, which, if not in excessive proportion, are difficult to detect. The, most probable adulterants are poppy oil, lard oil, cocoanut oil, seal oil, rosin oil, and the oxidised or " blown " oil now manu- factured from rape, linseed, or cottonseed oil. The density of castor oil is exceptionally high. It usually ranges between 960 and 964, and any sample having a less density than 958 is open to grave suspicion. The only other commercial fixed oil having as high a density as castor oil is blown oil. Rosin oil has often as high a density as 998, but it can be detected and determined with accuracy as described on page 83. The viscosity of castor oil at the ordinary temperature exceeds that of all other natural fluid fixed oils, but is approached by rosin oil and blown oil. The solubility of castor oil in alcohol is much greater than that of any oil likely to be used as an adulterant. According to the British Pharmacopoeia, it is entiiely soluble in an equal mea- sure of absolute alcohol, and in twice its measure of rectified spirit. This description is faulty ; at a temperature of 30 C. it is strictly correct, provided the strength (specific gravity 838) and volume of rectified spirit and temperature prescribed be rigidly adhered to ; but the use of a slightly weaker spirit, the addition of a very trifling proportion of water, or a slight reduction of temperature, causes the castor oil to be thrown out of solution. It is perhaps prefer- able to use 4 measures of rectified spirit at 15 C. than half that proportion at the higher temperature. If any considerable pro- portion of adulterant be present, the liquid separates on standing into three layers, of which the lowest is usually the foreign oil, and its volume will afford an approximate indication of the pro- portion of the admixture. If the adulterating oil can be identified by its chemical or physical characters, or referred to its proper group, the altered specific gravity of the sample will also afford a means of approximately estimating the proportion present. Oleic acid would not be detected by the alcohol test, but it can be determined with accuracy by titrating the sample with standard alkali (page 76). The behaviour of castor oil with petroleum spirit is highly characteristic. As far as has been recorded, all other fixed oils dissolve with facility in petroleum spirit, and are probably miscible BLOWN OIL. 129 in all proportions therewith, and with mineral lubricating oil. On the other hand, castor oil is not soluble in petroleum spirit, though it is itself capable of dissolving its own volume of that liquid. With the heavier petroleum and shale products castor oil behaves in a similar manner, at least in a qualitative sense. In cases where it is desired to make a mixed oil for lubricating purposes, the castor oil must first be dissolved in an equal measure of lard or tallow oil, and the heavy mineral oil subsequently added. If the proportion of this does not exceed that of the castor oil employed, no separa- tion will occur on standing. Castor oil is readily soluble in glacial acetic acid. It is easily miscible with an equal measure of that solvent at the ordinary temperature, whereas most other fixed oils, except croton oil, are only dissolved on heating, and yield solutions which become turbid before they have again cooled to the ordinary temperature. Another useful test for the purity of castor oil is the determina- tion of its saponification-equivalent in the manner de- scribed on page 40. 1 The number for castor oil is about 315. The values found by the author for blown rape oil varied from 275 to 284. Most other oils require a larger proportion of alkali than castor, and this is especially the case with cocoanut oil, the pre- sence of which the test is well adapted to recognise. Kefined rosin oil, which has been extensively emplttyed for the adulteration of castor oil, neutralises no alkali, or only a trifling quantity, and may be determined with accuracy by the process described on page 83. The formation of sebacic acid, when the sample is distilled alone or with a quantity of alkali insufficient for its complete saponification (page 127), may be employed as a test for foreign fixed oils in castor oil. OXIDISED OIL, BLOWN OIL, or BASE OIL, is manufactured by blowing air through warm rape, cottonseed, linseed, or other oil. Great heat is developed, and the oil gradually increases in density and viscosity till it presents a close resemblance to castor oil. The product can. be varied by arresting the process at any particular point. Blown oil is usually of a clear yellow colour, with a disagreeable smell and taste suggesting its origin. It is very viscous, and is as dense as castor oil, from which it differs by not readily dissolving in alcohol, and in being soluble in petroleum spirit. It yields sebacic acid on dry distillation, and contains but an insignificant proportion of unsaponifiable matter. The odour, taste, and colour-reaction with strong sulphuric acid afford an indication of its origin. 1 A sample of castor oil foots, containing much stearin, was found by the writer to have a saponification-equivalent of 295 '3, the density being 939 '4. VOL. II. I 130 TURKEY RED OIL. Oxidised oil is now manufactured largely for mixing with mineral oil, with which, unlike castor oil, it is perfectly miscible. ALIZARIN OIL. TURKEY-RED OIL. In dyeing cotton goods red with alizarin, the employment of a fatty acid at one stage of the process is essential. Experience has shown that the best results are obtained by employing the ammonium salt of sulpho-ricinoleic acid, C 18 H 33 (HS0 3 )0 3 , a body which is obtained, mixed with unaltered glycerides and with the products of its decomposition (see " Sulpholeic Acid "), by the action of sulphuric acid on castor oil. The details of the method of preparation vary with each work, 1 and are generally kept jealously secret, but a common plan is to treat castor oil with strong sulphuric acid, preferably diluted with about one-third of its bulk of water, and leave the mixture overnight. The excess of sulphuric acid is then removed by agitating the product with a solution of common salt, and the oily layer of crude sulphoricinoleic acid is neutralised with ammonia, or with a mixture of ammonia with potash or soda. The product consists chiefly of ammonium sulphoricinoleate, and constitutes " alizarin or turkey-red oil," sometimes called "red oil" or "olein oil." Turkey-red oil, if properly prepared from pure castor oil, when largely diluted, even with hard water, 2 will bear the addition of ammonia to alkaline reaction without showing any turbidity on standing for several hours. A turbidity or precipitate indicates the presence of smaller or larger quantities of solid fats, and indicates the employment, for making the turkey-red oil, either of very impure castor oil (e.g., castor oil foots) or of more or less rape, cottonseed, olive, or other oil containing stearin or palmitin. A further indication of these oils having been employed is obtained by boiling the sample for some time with dilute sulphuric acid, and observing the solidifying point of the mixture of glycerides and free fatty acids constituting the oily layer. The alcohol-test, de- scribed on page 128, is also available, for the oil layer will be wholly soluble if castor oil alone was used for the preparation of the alizarin oil, while the liquid will be turbid, and globules of undissolved glycerides will gradually separate, if other oils had been used. The test becomes more delicate if the alcohol be cautiously diluted. 1 An entirely different product, which finds its special application in the old process of turkey-red dyeing, is described on page 103. The sulphoricin- oleates are chiefly employed for producing alizarin reds by the quick process. 2 A pure turkey -red oil from castor oil can dissolve small proportions of calcium salts. If the oil be acid, a white precipitate may be produced on diluting it even with distilled water, but this will immediately disappear on adding excess of ammonia. ASSAY OF ALIZARIN OILS. 131 The proportion of fatty acids, &c., present in alizarin oil varies considerably. It may be as low as 40, and occasionally reaches 65 per cent., the usual proportion being about 50 per cent. A method of assay which is well suited for comparative experi- ments, though making no pretension to scientific accuracy, consists in treating 30 grammes of the sample with about 70 c.c. of water and 25 c.c. of sulphuric acid of 1520 specific gravity. The opera- tion is most conveniently conducted in a flask, the body of which holds 150 c.c., and the neck which is long, narrow, and graduated an additional 50 c.c. The liquid is carefully boiled for a time and then made up to the 200 c.c. mark with hot water, and the volume of the separated oily layer observed after an interval of half an hour. If separation does not occur readily, the contents of the flask should again be shaken up and allowed to stand. The results by the last method are liable to be below the truth, owing to the solubility of the sulphoricinoleic acid. They would probably be materially improved by saturating the aqueous liquid with common salt. E. Williams (Jour. Soc. Chem. Ind., v. 73) treats 25 grammes of the sample in a porcelain dish on the water- bath with sufficient dilute acid to decompose it, 75 c.c. of a satur- ated solution of common salt, and 25 grammes of white wax. The sulphoricinoleic acid is insoluble in brine, and hence rises to the surface and dissolves in the melted wax. After cooling, the cake of wax is removed, dried as completely as possible with filter-paper, and then gently heated or dried over sulphuric acid to remove the last traces of water. The excess of weight over that of the wax taken gives the weight of fatty acids in the quantity of the original oil taken. B r ii h 1 recommends the extraction of the liberated fatty acids with ether. The oil is treated with sufficient dilute sulphuric acid (1 : 10) for its decomposition, and is then shaken with ether. The ethereal layer is separated, evaporated at a gentle heat, the residue dried at a temperature not exceeding 70 C., and then weighed. R. Williams considers this process to give results in excess of the truth, in consequence of the ethereal extract being contaminated with water and mineral matter (usually sodium sul- phate). The ethereal layer cannot be purified by agitation with water without some of the sulphoricinoleic acid passing into the aqueous liquid. Palm Oil. French Huile de palme. German Palmol ; Palmfett. (See also table on page 67.) 1 Palm oil is the product of 1 The author is indebted to Mr A. Norman T a t e for much valuable information on the subject of palm oil. 132 PALM OIL. several species of palm, but particularly of Elais Guineenis. Palm oil proper is obtained from the outer fleshy coating of the seed, the palmnut or palm-kernel oil having distinct characters (page 133). Palm oil varies in consistency from that of soft lard to that of the hardest tallow, and its melting point is correspondingly vari- able. In colour the oil ranges from the brownish-yellow common in the Salt-pond and Grand Bassa brands through various shades of red and orange to the orange-yellow of new Calabar oil. The colour becomes pale after keeping the oil for some time, especially if it be exposed to light and air, the oil at the same time becom- ing rancid. The odour of some of the better oils, such as Calabar, Brass, Benin, &c.,. is not disagreeable, but some of the irregular oils, such as Salt-pond, have a more or less disagreeable smell, especially when warmed. In chemical composition fresh palm oil consists essentially of a mixture of tripalmitin and triolein, the former constituent predominating. Old and rancid samples contain a considerable proportion of free fatty acid. Palm oil is a common constituent of railway carriage grease (see footnote on page 192), and is largely used for making soap and, according to Muter, factitious butter. Palmitic acid, ex- tensively employed for making candles, and oleic acid, often called olein, are obtained by saponifying palm oil under high pres- sure with water and a small proportion of a base (see page 30), and subjecting the resultant mixture of fatty acids to hydraulic pressure. COMMERCIAL PALM OIL. Palm oil as met with in commerce varies greatly in quality. It almost always contains more or less water and solid impurities. 1 Some of the irregular oils occasionally contain 25 or 30 per cent, or even more of such foreign matters, but the usual range is from 2 to 16 per cent., while most of the regular oil does not contain more than 5 or 6 per cent. The water is best determined by exposing 10 grammes of the sample to a temperature of 110 C. for an hour or two, and noting the loss of weight (see " Lard "). If the residual oil be then dissolved in warm petroleum spirit, the solid impurities will settle to the bottom, and can be filtered off, washed with a little ether, dried, removed from the filter, and weighed. After weigh- ing, the residue may be ignited, when the ash will indicate with sufficient accuracy the proportion of sand and mineral matters, and loss of weight will give that of the organic matter. In many cases 1 It is usual to sell palm oil on the assumption that 2 per cent, of such foreign matters are (almost unavoidably) present, but any excess over this proportion is taken into account, and allowed for when selling. ASSAY OF PALM OIL. 133 the water can be determined with sufficient accuracy by noting the measure of the aqueous layer which separates when the imdried sample is dissolved in petroleum spirit, or simply kept melted in a graduated tube immersed in hot water. Palm oil often contains a considerable proportion si free fatty acids, the amount increasing as the oil gets old. The free acid raises the solidifying point of the oil, and causes it to exercise a very corrosive action on iron and steel. A strip of bright steel will soon become discoloured if immersed in palm oil containing free acid, and if left for some time in the oil will be found to be deeply pitted in places. (L. A r c h b u 1 1, Analyst, ix. 172.) The following proportions of free fatty acid, calculated as palmitic acid (see page 76), have been found in palm oil : Palmitic Acid, Palmitic Acid, Kind of Oil. per cent. Kind of Oil. per cent. Archbutt. A. N. Tate. L. Archbutt. Salt-pond, 78-9 84'0 Fernando Po, 40-5 Unknown, 72-0 Half-jack, . 357 Refined, 55-8 Half-jack, . . 24-4 Brass, 53-2 65-0 Bonny, . 21-5 New Calabar, 52-2 49-0 Lagos, . 11-9 The following results obtained by the analysis of typical samples of palm oil, from which the water and impurities were removed, have been communicated to the author by A. Norman Tate. Brass. Benin. Lagos. New Calabar. Old Calabar. Grand Bassa. Specific gravity at 15 C.,i Saponification-equivalent, Fatty acids ; percentage, ,, solidifying point, 921-3 280-2 96-97 44-4-45-8 922-8 282-9 96-96-5 45-0-45-5 920-3 285-4 '94-97 44-5-45-5 926-9 280-9 94-97 44-2-45-5 920-9 284-5 94-2-95 44-2-45-5 924-5 278-8 95-5-96.5 41-5-42-3 ,, combining weight, 273-4 273-7 272-7 273*2 273-2 273-0 PALM OLEIN is obtained by subjecting palm oil to hydraulic pressure in the same way that lard oil is made from lard. It usually has a density of about 914, and solidifies at 10 C. With sulphuric acid it gives a greenish-yellow spot, which changes to a mottled brown on stirring. PALM-NUT OIL or PALM-KERNEL OIL presents marked distinc- tions from palm oil. It varies from white to primrose yellow or 1 Determined by filling a gravity-bottle with the melted oil, and carefully working the stopper in when the contents had cooled to 15 C. 134 PALM NUT OIL. pink in colour, with a characteristic odour, recalling that of violets, but not unlike that of cocoanut oil, which it resembles closely in every respect. The density is high, ranging from 866 to 873 at 99 C. (compared with water at 15'5 as 1000). The melting point is from 26 to 30, solidification occurring at 18 to 20, and the temperature again rising pretty constantly to 25 or 26 C. Palmnut oil contains a large proportion of glycerides of lower fatty acids, the composition of a sample analysed by u d e- mans (Jour. Pract. C/iem. [2], ii. 393 ; Watts' Diet. Chem., vii. 890) being : Glyceride of oleic acid, 26 '6 per cent. Glycerides of stearic, palmitic, and myristic acids, ... 33 '0 ,, Glycerides of lauric, capric, caprylic, and caproic acids, 40 '4 lOO'O It is worthy of notice that all the fatty acids of which the glycerides are said to be present contain an even number of carbon-atoms. The same remark applies to cocoanut oil, which has a very similar composition (see page 136), but usually contains a somewhat larger proportion of lower fatty acids. Thus, the saponi- fication-equivalent of palmnut oil usually is about 227, but varies somewhat with the mode of preparation, as if it be extracted from the palm-kernels by a solvent instead of by pressure the propor- tion of glycerides of higher fatty acids is increased, and the melting point and saponification-equivalent of the product are raised in proportion. Palmnut oil is stated to be sometimes adulterated with or substituted by lard or tallow, coloured with turmeric and scented with orris root. With modified figures for the saponification- equivalenfc and distillate-acidity (page 46), the method of examining cocoanut oil for such adulterants fully applies to palmnut oil. Cacao Butter. Oil of Theobroma. French Beurre de Cacao. German Kakaobutter. (See also table on page 67.) This oil is expressed from the cacaonut, Theobroma cacao, from which ordinary cocoa is ob- tained, and must not be confused with cocoanut oil from Cocus nucifera. Cacao butter is a yellowish fat, gradually turning white on keeping. At the ordinary temperature it may be broken into fragments, but softens in the hand and melts in the mouth. It fuses between 30 and 33 (rarely at 29) to a transparent yellowish liquid, which congeals again at 20 '5, the temperature rising to about 27. Cacao butter has an agreeable odour, tastes like choco- late and does not readily become rancid. It dissolves in 20 parts CACAO BUTTER. 135 of hot alcohol, separating almost completely on cooling, and is also dissolved by ether, acetic ether, &c. Cacao butter contains glycerides ofstearic, oleic, and a little lauric, palmitic, and arachidic acids. C. Kingzett obtained from cacao butter an acid of the formula C^HjggOg, which he named theobromic acid. EXAMINATION OF CACAO BUTTER. Cacao butter is liable to adulteration with tallow, lard, and other fats. Observations of the melting point and density of the sample do not furnish satisfactory means of detecting such admix- tures. E. Bensemann finds the fatty acids from different kinds of cacao butter to have a very constant melting point. When the determination is made in the manner recommended by him (page 22), they commence to melt at 48 to 50, the temperature of perfect fusion being 51 to 53 C. Tallow is said to be capable of detection by saturating a cotton thread with the oil, allowing it to burn for a short time, and then blowing it out, when the odour of tallow becomes perceptible. A better test for tallow and other adulterants of cacao butter is to dissolve 2 grammes of the fat in 4 grammes of ether at 17 C., and then immerse the closely corked test-tube in ice-cold water. Granules will separate from pure cacao butter in not less than 3, and more frequently in from 5 to 8 minutes ; while if tallow or suet be present a turbidity will appear at once or within 2J minutes, according to the proportion of the adulterant, of which 5 per cent, may thus be detected. On exposing the solution to a temperature of 14 to 15, it will gradually become clear again if the sample was pure, but not if it was adulterated. This test is due to Bjorkland, and is adopted in the United States Pharma- copoeia. Its value has been confirmed by other observers, of whom Lamhofer has pointed out that petroleum ether may be employed with similar results, except that the cacao butter separates rather more slowly than from ether, the deposit being always granular, while other fats render the entire liquid cloudy. The solution of cacoa butter in two parts of ether will remain clear for a whole day if maintained at a temperature of 12 to 15. This modification of the test is prescribed by the German Pharmacopoeia, and is due to Ramsperger, who states that aniline may be substituted for the ether. According to E. D i e t r i c h, a very reliable test for the purity of cacao butter consists in warming the sample with an equal quantity of " paraffin oil " (? kerosene). A drop of the mixture is placed on a slip of glass, a thin cover applied and slightly pressed down, and the slide then exposed for twelve hours to a tempera- ture not exceeding 5 C. When then examined with polarised 136 COCOANUT OIL. light under a magnifying power of 20 diameters cacao butter appears crystallised in a form; resembling palm-leaves, showing a fine play of colours with solvents. An addition of 10 per cent, of beef tallow causes the fat to crystallise in tufts of needles, which exhibit a black cross ; while, if mutton tallow be the adulterant, it is stated that no cross can be seen. Cocoanut Oil. Coco-nut Oil. French Beurre de Coco. German Kocosnussol. (See also table on page 68.) Cocoanut oil has the consistency of butter or soft lard. It is white or but slightly coloured, and has a characteristic taste and odour of cocoanut. It is liable to become rancid, and has then a less pleasant flavour. The melting point is variable, and the density at 98 to 99 C. ranges from 868 to 874, being greater than that of the majority of vegetable fats. Cocoanut oil has a peculiar and highly complex chemical com- position. It is largely composed of the glyceride of lauric acid, C 12 H 24 2 , and contains even lower homologues (e.g , capric, caprylic, caproic) capable of distillation in a current of open steam, and to some extent soluble in water (see pages 37 and 46) ; but the glycerides ofmyristic, palmitic, and stearic acids are also present in notable proportion. On the other hand, the low iodine-absorption (page 50) shows that comparatively little o 1 e i n or its homologues can be present. 1 Cocoanut oil forms a soap, the aqueous solution of which is not readily precipitated by common salt, and hence is available for use with sea-water. Cocoanut oil is alleged to be liable to adulteration with suet, beef marrow, and other animal greases, as also with almond oil and wax. All these apocryphal adulterations would be detected by the reduced density at the temperature of boiling water, the increased saponifi cat ion-equivalent (page 42), and the reduced amount of alkali neutralised by the distillate obtained by Reichert's process (page 46). Indeed, there is no addi- tion likely to be made in practice, excepting that of palmnut oil, which, if practised in notable proportion, would not be detected by these tests. The same methods if used with discretion will equally serve to determine the approximate proportion of the adulterant. 1 C. R. A. Wright (Jour. Soc. Arts, xxxiii. 1122) states that the mixed fatty acids from cocoanut oil have a mean combining weight ranging between 196 and 204, that of pure lauric acid being 200. The saponification-equivalent of cocoanut oil varies from 209 to 228, the corresponding mean combining weights (calculated) of the mixed fatty acids ranging from 1957 to 2147. COGOANUT OLEIN. 137 Palmnut oil cannot be detected by the above or any other satis- factory method, but as it is employed for the same purposes as cocoanut oil, the substitution has little practical importance. COCOANUT OLEIN and COCOANUT STEARIN are products obtained by submitting cocoanut oil to hydraulic pressure. The following figures, obtained in the author's laboratory from samples furnished him by Price's Patent Candle Company, show the relative physical and chemical characters of the two products : Olein. Stearin. Sp. gravity (water at 15'5 = 1000) : 'At 98-5 C., 871-0 869-6 At 60-0 C., ... 895-9 At 15-5 C., 926-2 Solid. Melting point ; C., ... 28 '5 Solidifying point ; C., 4'0, rising to 8'0 21 '5, rising to 26 '0 Saponification-equivalent, ... ... 215 217 No. of c.c. alkali by Reichert's test, 5-6 3-1 * Japan Wax. French Cire Japonoise. German Japanisches Wachs. (See also table on page 68.) Japan " wax " is contained between the kernel and outer skin of the berries of several species of Rhus, the most important of which is Rhus succedanea, which flourishes chiefly in the western provinces of Japan, and is now also cultivated in California. The crude wax forms a coarse, greenish, tallow-like mass, which is purified by melting, pressing through canvas, bleaching in the sun, &c. Purified Japan wax is a yellowish-white, straw-yellow, or greenish-yellow waxy substance, having a smell recalling at once that of tallow and of some kinds of beeswax. Under ordinary circumstances it fuses at 51 to 53 C., but a recently solidified sample melts at a considerably lower temperature. Its solidify- ing point is about 41, the temperature rising to 48-49 in the act of solidification. The specific gravity of Japan wax at the ordinary temperature is about 990, while in a molten state at a temperature of 98 to 99 C. it has a density of 873 to 877, compared with water at 15 '5 C. taken as 1000. Thus, in the solid state, Japan wax equals in density the true waxes ; and in the molten state it is considerably denser either than the true waxes or the ordinary vegetable fats. Japan wax is completely soluble in boiling alcohol or ether, but is almost completely deposited on cooling. 138 JAPAN WAX. Japan wax is stated to be frequently adulterated with water, with which it is capable of forming a sort of emulsion when agitated with it a little above its melting point. Japan wax is readily and completely saponifiable, yielding fatty acids and glycerol, and hence is distinct in constitution from the true waxes, which yield higher monatomic alcohols when saponified (page 31). It is usually stated to consist essentially of tripal- m i t i n and trilaurin, with more or less free palmitic and lauric acids. The following figures were obtained in the author's labora- tory by the examination of three samples from different sources. For convenience, the results yielded by a sample of myrtle wax are placed in juxtaposition : - Japan Wax. Myrtle Wax. No. 1. No. 2. No. 3. Specific gravity of solid wax at 15-5 ft., .... ... 993 984 ... Specific gravity of molten wax, at 98-99 0., .... 875 877 876 875 Melting point (method a, page 21), . Solidifying point (method d, page 23), 51-5 52-0 41-0 40-5 39-5 , , temperature rising to Free fatty acid, per cent, (in terms of 48-5 39-5 palmitic acid), .... 9-03 1272 8-96 0-12 Saponification-equivalent, = Percentage of KHO required, . 2587 21-68 252-9 22-13 261-2 21-44 265-2 21-15 Products of saponification : Glycerol, per cent. , 13-50 14-71 11-59 ]3-38 Insoluble acids ; sp. gr. at 98-99 C. 848 848 837 ,, melting point, . 57-0 56-0 47-5 solidifying point, 56-5 53-0 46-0 ,, combining weight, Soluble acids (as C 8 H 16 2 ), p. cent., 259-3 257-5 8-40 243-0 The density of the insoluble acids, considered in conjunction with their mean combining weight, renders it doubtful whether these fatty acids really consist of palmitic acid with more or less of its homologues, or of fatty acids isomeric with these. The proportion of glycerol, as determined by the perman- ganate process, produced by the saponification of Japan wax is notably in excess of that required to form a triglyceride of the fatty acids present, and this is especially true of No. 2, the glycerol from which sample was several times determined with great care. Whether the high proportion of glycerol be real, or due to some unusual constituent which renders the determination by permanganate inaccurate, has not been positively ascertained. That the constitution of Japan wax is peculiar is evident from TALLOW. 139 the study of the products of its saponification, and is shown also by its high density both in the solid and liquid state, in which characters it differs widely from the majority of solid fats. The author has the constitution of Japan wax and certain allied products still under investigation. Tallow. French Suif. German Talg. (See also table on page 70.) Tallow is commercially classed as " beef " and " mutton " tallow, but each of these comprises the fat of other animals besides the ox and sheep. Pure tallow is white and almost tasteless, but much of that imported has a yellow colour and disagreeable rancid flavour. In chemical composition, tallow is very similar to lard, consisting essentially of a mixture of the triglycerides of palmitic, stearic, and oleic acids. According to A. Schuller (Ann. Phys. Chem. [2], xviii. 317; Jour. Chem. Soc., xliv. 546), tallow can be distilled in a vacuum ; if distilled with superheated steam it yields oleic, pal- mitic and stearic acids, and glycerin. The relative proportions of oleic and solid fatty acids yielded on saponification affect the value of tallow (see next page). By pressure, a considerable portion of the olein of tallow can be removed, and forms a product known as "tallow oil" (page 141), the solid portion constituting "tallowsteari n." EXAMINATION OF COMMERCIAL TALLOW. The tallow of commerce frequently contains a sensible pro- portion of free fatty acid, the amount of which can be ascer- tained with accuracy by titration with standard alkali and phenol-phthalein, as described on page 76. The percentage of potassium hydroxide (KHO) required for neutralisation, when multiplied by 5, gives with sufficient accuracy the percentage of free acid. W. H. Deering (Jour. Soc. Chem. Ind., iii. 540) found that in 24 out of 25 samples of tallow from different sources the free acid ranged from 0'85 (in an Australian mutton tallow) to 12 '20 per cent, (in a Russian tallow), while one sample ("town tallow ") which had been kept in store for six years contained 25 per cent, of free fatty acids. The free acid in thirty-six samples of Australian tallow examined by A. N. Tate ranged from 1*20 to 4*70 per cent. Large proportions of free acid are apt to be due to the tallow being adulterated with wool grease acids, or stearic acid from cottonseed oil. 1 Tallow frequently contains more or less water, infusible matters, 1 In a trial at Manchester it was admitted that 30 per cent, of cottonseed stearin had been added to a quantity of tallow ; and it was contended on behalf 140 EXAMINATION OF TALLOW. and mineral impurities, and has been occasionally purposely adul- terated with starch, china clay, whiting, barium sulphate, &c. Fats of greater fusibility, especially bone fat, may be present, and wool grease acids and cottonseed " stearin " have been extensively used. 1 Cakes of tallow are said to have been met with, the interior of which consisted of inferior fats. The presence of water, starch, and insoluble substances gene- rally can be detected, and their proportion estimated, as described under "Lard." 2 If bone fat be present, the calcium phosphate, which is a characteristic constituent of it, is not separated by simple fusion, but will be left with any other mineral impurities on igniting the tallow in a muffle. For the detection of calcium phosphate and other impurities, 10 grammes of the tallow may be dissolved in carbon disulphide or petroleum spirit, filtered, the residue washed with a little ether, and dried at a moderate temperature. The insoluble matter may be examined under the microscope, when starch, gelatinous matter, or fragments of tissue 3 will be readily recognised. Starch may also be detected by boiling the residue with water and testing the solution with iodine. Lime soap will be detected by warming the residue with dilute hydrochloric acid, when globules of fatty acids will rise to the the top of the liquid, and the latter, after filtration, may be neutral- ised, and tested for calcium with ammonium oxalate. Any effer- vescence of the residue, on addition of hydrochloric acid, will pro- bably be due to whiting. Cottonseed stearin (as distinguished from the stearic acid from cottonseed oil) may be sought for as in lard. 3 The varying quality and frequent adulteration of tallow some years since caused the French candle-manufacturers to adopt a process of assaying samples for the relative proportions of oleic and solid fatty acids. This they effect by Dalican's method, which consists in determining the solidifying point of the mixed fatty acids produced by saponifying the fat, 4 by method d, page 23. The lowest permissible solidifying point of the acids is often fixed at 44 C., corresponding to a mixture of oleic and solid fatty acids in equal proportions. The following table by F. D a 1 i c a 11 shows the of the adulterator, who gained the case, that this fat mixture might still be regarded commercially as tallow of a certain quality ! 1 Vide footnote, p. 139. 2 The insoluble matter present in samples of tallow representing large lots is usually under 0'2 per cent., and the water rarely exceeds 1 to 1'5 per cent. 3 Tallow which has not been washed and purified, and which therefore con- tains particles of blood, &c., acquires a light brown colour when agitated in a melted state with one-fifth of its measure of nitric acid (sp. gr. 1 '38). This reac- tion was formerly erroneously ascribed to the presence of cottonseed stearin. * For the method of preparing the fatty acids, see footnote on page 215. DETECTION OF WOOL FAT. 141 approximate yield of solid fatty acids ("stearic acid") from 100 parts of tallow or other fat. The corresponding oleic acid may be found by subtracting the percentage of solid acids from 95*00. Solidifying Solid acids; Solidifying Solid acids; Solidifying Solid acids; point ; C. per cent. point; C. per cent. point; C. per cent. 40-0 35-15 43-5 44-65 47-0 57-95 40-5 36-10 44-0 47-50 47-5 58-90 41-0 38-00 44-5 49-40 48-0 61-75 41-5 38-95 45-0 51-30 48-5 66-50 42-0 39-90 45-5 52-25 49-0 71-25 42-5 42-75 46-0 53-20 49-5 72-20 43-0 4370 46-5 55-10 50-0 75-05 Tallow has been occasionally met with which has been largely adulterated with the distilled fatty acids from wool grease, and L. Meyer (Dingl. polyt. J., ccxlvii. 305) has described a sample which consisted almost exclusively of such fatty acids. It smelt strongly of wool grease, yielded only 0'2 per cent, of glycerin on saponifi- cation, and when the aqueous solution of the resultant soap was shaken with ether, and the ethereal solution separated and evapo- rated, a considerable amount of cholesterin was obtained, which gave a violet coloration changing to blue when evaporated with concentrated hydrochloric acid and ferric chloride. Meyer states that 5 per cent, of wool grease can be detected in tallow by this method. The fatty acids separated from the soap formed in the above process turned yellow in a few days, and after several months had acquired a deep orange-yellow tint. TALLOW OIL, or Tallow Olein, is obtained by submitting tallow to hydraulic pressure. It much resembles lard oil, but is usually of inferior quality. The name " tallow oil " is sometimes incorrectly applied to crude oleic acid. Lard. French Axonge ; Saindoux. German Schmalz. (See also table on page 70.) Lard is the fat of the pig, melted and strained to separate tissue and impurities. The kind known as " bladder-lard " is usually prepared solely from the amentum or fat surrounding the kidneys. "Keg-lard" is made from the fat of the entire animal, and usually melts between 28 and 38 C., and solidifies between 24 and 31 C.; hence it melts at a lower temperature than that from the omentum, which fuses at 42 to 45 C., and alone has the strict right to be called lard. The mixed fat from the entire animal would be more appropriately termed 142 ADULTERATIONS OF LARD. " hog-dripping," and evidently bears the same relation to lard proper that mutton or beef dripping bears to suet. The Adeps prc¶tus of the British Pharmacopoeia is directed to be prepared from " the internal fat of the abdomen of the hog, per- fectly fresh "; and is stated to melt at about 100 F. ( = 37*8 C.). A. Percy Smith (Chem. News, Hi. 200) states that lard of high melting point is essential for making light pastry. By subjecting lard to a moderate temperature, combined with hydraulic pressure, most of the olein is separated, and forms lard oil (see next page), while the stearin and palmitin remain in the form of a solid cake of high melting point. EXAMINATION OF COMMERCIAL LARD. Pure lard should contain no foreign matter of any sort. A little salt is a legitimate addition when the lard is intended for cooking, and not for use in pharmacy. A common practice is to add a little carbonate of sodium to the lard in a melted state, with a view of whitening the product. Milk of lime, used in the proportion of from 2 to 5 per cent., gives a pearly white product, with which a large amount of water can be incorporated by stirring during cooling. Potato-starch and alum have been occasionally mixed with lard. Pure lard is wholly free from taste or smell, and forms a perfectly clear liquid when melted by immersing the tube containing it in hot water. If either lime, sodium carbonate, water, or any similar addition has been made, the melted fat will be more or less opaque. The most common adulterant of lard is water, which is intro- duced in quantities varying from 1 or 2 up to as much as nearly 30 per cent, of the weight of the lard. Even the lowest propor- tion affords a. remunerative return to the operator on a large scale. By keeping the sample in a molten condition, the water gradually settles out, and, if the experiment be conducted in a graduated tube, its volume may be measured. The method is apt to be tedious, and fails wholly with some samples. A better plan is to keep 1 grammes of the sample at a temperature of 110 C. till no more globules of water can be seen, when the loss of weight gives the amount of the adulterant. 1 Cocoanut oil has been employed for adulterating lard, and tallow and sesame oil are also said to have been used. J. Muter (Analyst, vii. 93) has described an adulteration of lard by cotton- seed stearin. The presence of either this adulterant or cocoanut oil would be indicated by the increased specific gravity of the sample, as will be seen by the following figures : 1 J. Muter heats a known quantity of the lard in a porcelain dish to about 105, and stirs with a thermometer till the water is driven off. LAUD OIL. 143 Lard. Cocoanut Oil. Cottonseed Stearin. Density at 98 to 99 C. (water at 15 -5 C. =1000), . 1 860 to 861 868 to 874 ... Density at 100 F. (water at 100 F. =1000), .... 1 905 to 907 910 to 916 911 to 912 Melting point ; C. . 33 to 45 20 to 28 32 Saponification-equivalent, . 286 to 292 209 to 228 285 to 294 Iodine-absorption, . 59 to 62 9 The cottonseed stearin is stated to give a red or brown colour with strong sulphuric acid (page 59) and with nitric acid, and to remain fluid for some time at a comparatively low tem- perature after being once melted, so that a sample containing it, when allowed to cool after fusion, does not set so solid as at first. Other adulterants of lard will remain on dissolving the sample in petroleum spirit. Mineral additions will be left on igniting the lard, a little at a time, in a porcelain dish. Salt, alum, and other soluble mineral additions can also be dissolved out by agitating the melted lard with hot water, and identified by testing the aqueous liquid with suitable reagents. Lime may be detected by triturating the sample with calomel or a solution of mercurous nitrate, when more or less darkening will ensue if lime be present. Lime soap may be detected as in tallow (page 140). The presence of gelatinous matter has been observed in lard by several chemists. It is probably usually a product of the alkali employed in refining on the albuminous matters present ; but appears in some cases to have been derived from Irish moss. 1 LARD OIL. When lard, and especially the softer kind, is subjected to hydrau- lic pressure, it yields a considerable quantity of a fluid called " lard oil," or " lard olein," while the solid portion constitutes "pressed lard," or "lard stearin." Consequently, the melting point and other characters of lard oil depend much on the temperature at which the pressing is conducted, winter-pressed lard oil naturally containing less of the solid constituents of lard than that expressed at a higher temperature. Lard oil consists of triolein, with variable proportions of p a 1 m i t i n and stearin. It varies in tint from light yellow to colourless, and has but little odour. It usually thickens at about 1 A s t a i x states that he found, in lard imported from New York, 25 per cent, of a jelly which was neither nitrogenous, amylaceous, nor pectic, but which offered a close resemblance to vegetable mucilage, particularly to the gelatinous matter furnished by Iceland or Carrageen moss. The jelly was insipid, insoluble in ether and alcohol, swelled in cold water, and was not precipitated by tannin, or coloured blue by iodine. 144 ADULTERATIONS OF LARD OIL. 4 C., and becomes solid at 4 C., but some samples exhibit wide departures from these limits. A specimen of pure winter-pressed oil examined by J. H e n r y began to deposit flakes at 8, was thick at 10, and solid at 12 C. It did not remelt com- pletely till the temperature reached 4-7 C. In many of its reactions, as in its chemical composition, lard oil closely resembles olive oil, which it simulates in its behaviour with nitric acid, the elaidin-test, and the temperature produced by strong sulphuric acid. Lard oil is extensively employed as a lubricant, as well as for soap-making, &c. The chief adulterants affect its viscosity and non-drying characters, and therefore its value for lubricating. Lard oil should not show any notable proportion of free acid when examined as on page 76. In America, lard oil is employed for burning in lighthouse lamps, and a small percentage of free acid has been found to affect its quality for this purpose very injuriously. The specific gravity of lard oil is about 915, and should not exceed 916 at 15 '5 C. ( = 60 F.). If heavier, the specimen is probably adulterated with fish oil, cocoanut olein, or cotton or other seed oil. Fish oils can be detected by the odour on w r arming the sample, by the increased temperature with sulphuric acid, and by the colour-reactions with sulphuric acid and caustic alkali ; cocoanut olein may be recognised by the taste and modified saponi- fication-equivalent of the sample ; and cotton and other seed oils may be detected, as in olive oil, by the elaidin-test, and their colour- reactions with nitric acid (page 100). Rape oil has nearly the same density as, and a colour not very dif- ferent from, some samples of lard oil. It may be detected by the modified elaidin-reaction and colour-reaction with nitric acid ; by the increased temperature developed on treating the sample with sulphuric acid ; by the increased saponification-equivalent ; and by the behaviour of the sample when heated to about 200 C., and then allowed to cool to 30. Lard oil is deodorised by this treat- ment, whereas the peculiar penetrating smell of rape oil is enhanced. Lard oil has recently been adulterated with a highly refined earthnut oil, manufactured in France. The admixture will be indicated by the behaviour of the sample with nitric acid (page 100 et seq.), and by the process described on page 106, depending on the isolation of arachidic acid. The presence of many vegetable oils in lard oils is indicated by the appearance of a well-defined band in the absorption- spectrum, near the line B. Genuine lard oil gives a spectrum showing no trace of absorption-bands. 4 Hydrocarbon oils can be detected and determined as described on page 80. MELTING POINT OF BUTTER FAT. 145 Butter Fat. Milk Fat. French Gras de Beurre. erraaw -Butterfett. (See also table on page 70.) Butter fat is the fat of milk or butter. "When used without qualification the term " butter fat " is always to be understood as applying to the fat from cows' milk, but the milk of other animals yields a very similar product. Butter fat can be prepared direct from milk by rendering the liquid faintly alkaline with caustic soda, and then agitating it with ether. After standing at rest for some time the ether separates, and can be removed and distilled, when the butter fat remains. The fat may also be prepared by evaporating the milk to dryness at 100, and exhausting the residue with ether or petroleum spirit. Butter fat is, however, more conveniently prepared from butter in the manner described on page 152. Butter fat has the well-known colour, taste, and smell of butter. The melting and solidifying points vary considerably in different samples. According to J. Bell, the melting point usually ranges between 29'5 and 33'0 C. (85 and 90 F.), the maximum being 347 ( = 94'5 F.). 1 The specific gravity of butter fat is higher than that of the majority of fats, a fact which is of value for its identification (page 153). Butter fat has a very peculiar and highly complex composition. It consists of a mixture of various glycerides, with traces of cholesterin or cholesteric ethers. Wein found in butter fat more or less of the glycerides of palmitic, oleic, stearic, myristic, arachidic, normal caprylic, capric, normal caproic, and butyric acids. Glycerides of acetic and formic acids were also found, but not those of propionic, valeric, osnanthylic, or pelargonic acids. The greater part consists of the glycerides of oleic and palmitic acids, that of stearic acid being usually present in smaller quantity. But the characteristic constituent of butter fat is b u t y r i n, the glyceride of butyric acid, which is present together with those of certain of its higher homologues. James Bell obtained the following products by saponifying 100 parts of butter fat 2 : 1 The melting point of butterine is stated to be between 25 "5 and 28 C. Bell's melting points were determined by suddenly cooling the melted fat by immersing the platinum capsule containing it in ice- water. A fragment of the fat was then taken up on a loop of platinum wire, and gradually heated in water in close proximity to the bulb of an immersed thermometer. 2 (Analysis and Adulteration of Foods, ii. 48.) The fatty acids soluble in water were regarded as butyric acid. Those soluble in hot water only appear in the analysis as caproic acid, &c., the combining weight being deduced from the amount of BaC0 3 left on igniting their barium salts. VOL. II. K 146 COMPOSITION OF BUTTER FAT. Butyric acid, . . 6 '13 Caproic, caprylic, and) 2 . 09 (mean combining weight = 136) capric acids, . . j Myristic, palmitic, and ^ AQ*AR ' stearic acids, . . j 35.55 Oleic acid, . . 3 6 '10 Glycerol (calculated), . 12 '5 4 106-32 The proportion of butyric acid and its immediate homo- logues produced by the saponification of butter is now well known, and ranges between 5 and 8 per cent. Muter obtained, from two samples of butter fat, 40'4 and 34'8 per cent, of oleic acid, and 47'5 and 52'1 per cent, of mixed myristic, palmitic, and stearic acids. The proportion of glycerol produced by the saponification of butter was first determined in 1823 by Chevreul, who obtained 11 '8 5 per cent, by direct weighing of the isolated glycerol, and Liebschiitz has recently isolated 13 '7 5 per cent. By oxidising the glycerol with permanganate, and determining the oxalic acid formed, Benedikt and Zsigmondy have recently found* from 10'2 to 11 '6 per cent, of glycerol to be formed by the saponification of butter, and the author's figures fully confirm these. These analytical results show that butter fat is essentially a mixture of various tri-glycerides, those of butyric, palmitic, and oleic acids being the leading constituents. These bodies have the following composition : C 3 H 5 '" : (O.C 4 H 7 0) 3 - C 3 H 5 '" I (O.C 16 H 31 0) 3 C 3 H 5 '" j (O.C 18 H 33 0) 3 Tributyrin. Tripalmitin. Triolein. Some experiments of James Bell indicate that the glycerides contain several acid-radicals in the same molecule, and therefore the butyrin cannot be separated by any process of fractional solution from the less soluble glycerides of palmitic and oleic acids. Hence butter fat probably contains complex glycerides of the following character : C 3 H 5 '" O.C 4 H 7 O.C 16 H 31 O.C 18 H 33 0. Such a complex glyceride would yield, on saponification, fatty acids and glycerol in the same proportions as would be obtained from a mixture of butyrin, palmitin, and olein in the proportion of their molecular weights. CONSTITUTION OF BUTTER FAT. 147 By treating butter with only half the quantity of alcoholic soda necessary for its complete saponification, and precipita- ting the liquid with water, Bell obtained an oil which solidified at 4'4 C., and on saponification yielded 88'1 per cent, of in- soluble acids, but no soluble fatty acids. This result agrees with the composition of a d i-g 1 y c e r i d e of the following char- acter : COM C.H'": S- c i6 H u. F. Riidorff. Various. Dietrich. Various. Melting Point. Solidifying Point. Melting Point. Beeswax, yellow, ,, bleached, 973 963-964 j 959-969 62-0-62-5 62-0-62-5 ( 63-64 \ 69-70 Spermaceti, 960 942-946 44-0-44-5 44-0-44-5 43-49 Carnaiiba wax, . 995-1000 83-85 Japan wax, 975 984-1000 52-5-54-5 41 -0, rising to 46 42-53 Tallow, . 952-961 925-940 42-5-50-5 33-0-39-5, rising 36-49 4-5 Stearic acid. 971-972 964-986 58-65 Colophony, 1045-1108 1070-1090 Paraffin wax, Cerasin, 913-914 918-922 j 868-915 ... 48-72 A further insight into the nature and proportion of the adulter- ants which the foregoing tests may have indicated to be present in a sample of beeswax can be obtained by a careful determination of the percentages of caustic potash required for the neutralisation of the free acid, and for the complete saponification of the sample. The method of operating is described on page 181 et seq. The following table, drawn up from the results of Hehner, Hiibl, and the writer, showj the behaviour with caustic alkali of such probable adulterants of beeswax as are soluble in oil of turpentine : Substance. Average Percentage of KHO required. Ratio of A:B. A. For Neutralisa- tion of Free Acid. B. For Saponifica- tion of Ethers. A +B. Total. Unbleached beeswax, 2-0 7'5 9'5 1:3-75 Chemically bleached beeswax, 2-4 7-1 9-5 1:2-96 Spermaceti, . traces 12-8 12-8 Carnaiiba wax, 4- -8 7-6 8-0-8-4 Tl9'0 1: ] 9-5 Chinese wax, . traces 6-3 6-3 Japan wax, . 2-0 19-5 21-5 1: 975 Myrtle wax, . 0-3 20-5 21-8 1:68-3 Tallow and stearin, 1-0 18-5 19-5 1:18-5 Stearic acid (com- mercial), 20-0 none 20-0 Colophony, 18-0 1-0 19-0 'l8 :1 Paraffin wax, Cerasin and ozo- none none none ... kerite, Spermaceti is not usually a probable adulterant of beeswax, but there have been occasions of late when its substitution would have been profitable and is said actually to have been practised. It is ANALYSIS OF WAX MIXTURES. 187 the only adulterant which would cause the sample to show less free acid, and yet require an increased proportion of alkali for its saponification, at the same time yielding less glycerin, and reducing the density and melting point. In the absence of carnaiiba wax, a direct indication of the presence and proportion of sper- maceti may be obtained from a determination of the melting point of the higher alcohols of the sample. From an inspection of the table, it appears that carnauba wax requires for complete saponification a proportion of alkali not 'very different from that required by beeswax, but is distinguished from the latter by the smaller (but very variable) proportion of alkali required by the free acid. An admixture of carnauba wax will be further indicated by the increased density and higher melting point of the sample, but the most striking distinction appears to be furnished by a determination of the halogen-absorption of the sample (page 50), for while beeswax is said by Mills to assimilate but a trifling quantity of bromine, carnauba wax combines with one-third of its weight. Hence the percentage of carnauba wax present in a mixture of that substance and beeswax would be three times the percentage of bromine absorbed. 1 Another proof of the presence of carnaiiba wax is obtainable by removing free acid by alcohol and alcoholic potash (page 181), saponifying the separated neutral wax (page 182), precipitating the solution with lead acetate and exhausting the precipitate with petroleum spirit (page 179), and decomposing the lead soap with hot hydrochloric acid. Beeswax, when thus treated, yields a product which is chiefly palmitic acid (melting point, 62 C.), while the product similarly obtained from carnauba wax is largely cerotic acid (melting point, 79 C.). If the proportion of alkali required for total saponification exceed 9 '5 or, at the outside, lO'O per cent, of the wax, the presence of some adulterant is certain. Japan wax, myrtle wax, tallow, and stearin all require proportions of potash not far from 20 per cent. Hence each O'l per cent, of KHO required in excess of the normal proportion 9 '5, indicates the presence of about '95 per cent, of one of these adulterants. Japan and myrtle wax are denser than beeswax, and tallow and stearin somewhat lighter, but they all agree in having a notably lower fusing point than pure beeswax, and yield glycerin on saponification. In doubtful cases, a determination of the glycerin by the permanganate process may be resorted to, when the amount 1 The method requires to be verified before it can be considered trustworthy. Japan wax, stearic acid, and hydrocarbon waxes resemble beeswax in taking up very little bromine, but tallow takes up a considerable proportion. 188 ADULTERATED BEESWAX. found multiplied by 10 gives the approximate weight of the adul- terant (page 33). The presence of glycerides is also indicated by the qualitative tests with borax and sodium carbonate (page 184). Free stearic acid is readily distinguished from the neutral fats by the large proportion of alkali required in the first stage of the process ; in fact, the percentage of this adulterant may be calcu- lated by multiplying by 5 any excess of potash required for sapon- ification above the normal proportion of 2 per cent. ' Stearic acid is also indicated by the sodium carbonate test. It is employed less frequently than other adulterants of beeswax, as it notably diminishes the malleability of the substance. Colophony or rosin requires somewhat less potash for its neutralisa- tion than is taken by stearic acid, and the proportion is not very constant. Its presence is further indicated by the increased density of the sample. It may be detected with certainty, even if present to the extent only of 1 per cent., by boiling 5 grammes of the sample for 1 minute with 20 c.c. of nitric acid of 1'33 specific gravity. When cold, the liquid is diluted with an equal volume of water and agitated with excess of ammonia. With pure wax a yellow solution is produced, but, if resin be present, nitro-compounds are formed which impart to the liquid a blood-red or reddish-brown tint, varying in intensity with the proportion of the adulterant. Cases have been recorded of factitious beeswax composed of 60 per cent, of paraffin and 40 of yellow resin, covered with a thin layer of genuine beeswax. On boiling the sample with 15 times its weight of alcohol of 870 specific gravity, the paraffin was left in fused colourless globules having a density of 910, while the solution yielded the resin on evaporation. Such a residue would give a marked resinous odour when heated, but if the proportion of the sample soluble in alcohol be only small, such a test must not be regarded as absolute proof of the presence of added resin, as many specimens of genuine beeswax behave similarly. Paraffin, cerasin, and ozokerite are the only adulterants of bees- wax which tend to reduce in a notable degree the proportion of potash required for saponification. They also reduce the density in a marked manner, but this indication has little more than a qualitative value. In a sample consisting solely of beeswax and hydrocarbon wax the proportion of the former may be deduced with considerable accuracy from the results of the saponification, each O'l per cent, of KHO required representing 1*053 per cent, of beeswax in the sample. In more complex mixtures the proportion of hydrocarbon waxes may be determined by the following process : 5 grammes of the sample should be heated to about 130 C. in a capacious flask with ANALYSIS OF WAX MIXTURES. 189 50 c.c. of concentrated sulphuric acid. The fluid froths arid rises considerably, large quantities of sulphur dioxide and other gases are evolved, and charring takes place. After about 10 minutes the mixture becomes almost solid, when it is allowed to cool, the acid removed by washing with water, and the residue treated with a little cold alcohol to remove adhering water. The filter with the contained black residue is then exhausted with hot ether, prefer- ably in a Soxhlet's tube, when the ether yields the hydrocarbon wax on evaporation. It should be weighed, and then again treated with sulphuric acid, and the residue exhausted with ether, &c., as a little beeswax is liable to escape decomposition during the first operation. The percentage of hydrocarbon wax in any wax-mixture having been thus ascertained, the proportions of myricin, glycerides, cerotic acid, and free acids from ordinary glycerides (palmitic, stearic) may be calculated by the following method, which is a modification of that originally proposed byO. Hehner (Analyst, viii. 26). A = percentage of KHO required to neutralise the free acids of the sample. B = percentage of KHO required to saponify the ethers of the sample. H = percentage of hydrocarbon wax as previously ascertained. C = percentage of cerotic acid neutralising 13'68 per cent, of KHO. F = percentage of fatty acids neutralising 20 per cent, of KHO. M = percentage of myricin saponified by 8*30 per cent, of KHO. G = percentage of glycerides saponified by 1 9 per cent. KHO. From these data the following equations may be constructed : 73100 -3655A-3847B-7-31H (3) F = 5A -0-684C (4) G=100 -H-M-C-F A, B, and H being known, the values of M, C, F, and G are easily found. The sum of the cerotic acid and myricin reduced from equations 1 and 2 gives approximately the percentage of beeswax in the sample, but a more accurate determination will be obtained if 2* a be deducted from the amount thus found. 1 The ratio of cerotic acid to myricin is assumed to be constantly 1 : 6 '12, which is the average ratio in which they exist in beeswax, according to 0. Hehner. 190 CARNAUBA WAX. Carnaiiba wax will be estimated as beeswax, but the result obtained from, mixtures containing it must not be regarded as more than a rough approximation to the sum of the two waxes. Stearic and palmitic acids will be determined pretty accurately by the value obtained for F, while the figure obtained for G will approximately represent the neutral fats. If other tests have shown that the neutral fat present exists in the form of Japan wax, one-tenth of the percentage of that substance indicated by G may be advan- tageously deducted from F, to obtain a more correct estimate of the palmitic or stearic acid introduced as such into the mixture. Spermaceti, if present, would invalidate the calculations by the foregoing formula. By introducing two fresh factors, namely, the proportions of ether-residue and glycerin yielded on sapomfication, the formula might be modified to include spermaceti, but it is not of sufficient practical interest to justify the complication. Carnaiiba Wax. Canauba wax. Carnahuba wax. (See also table on page 73.) This wax is a very hard, sulphur- yellow, or yellowish green substance, melting at about 84, nearly as dense as water, and leaving, on ignition, a trifling quantity of ash, which often contains oxide of iron. Carnaiiba wax has a very complex composition. It consists of a mixture of higher fatty acids and alcohols, together with the ethers of these bodies. Berard found free cerotic acid (page 179) in the portion of the wax soluble in hot alcohol, while Story-Maskelyne found myricyl alcohol (page 180) in the same solution. This result is confirmed by H. Stiirke, 1 who has recently investigated the chemistry of carnaiiba wax in a very thorough manner (Annalen, ccxxiii. 283; Jour. Chem. Soc., xlvi. 1280; Jour. Soc. Chem. Ind., iii. 448). He states the alcoholic solution to contain myricyl alcohol, and a small quantity of myricyl cerotate, C 30 H 61 .C 2 ^H 53 2 , which is soluble in boiling alcohol to the extent of 0'82 gramme per litre. The free myricyl alcohol and that obtainable by saponifying the myricyl cerotate of the wax together amount to 45 per cent, of the entire wax. 2 1 The researches of Story-Maskelyne and Stiirke, while demonstrating the presence of free inyricyl alcohol, do not prove the absence of free cerotic acid from carnaiiba wax. Hehner and Hiibl have shown the presence of a free acid equivalent to from 3 or 6 per cent, of cerotic acid. The myricyl cerotate of carnaiiba wax may have the same tendency to hydrolysis as the palmitin of palm oil. Myricyl alcohol and free cerotic acid may be, and probably are, simultaneously present in carnaiiba wax. 2 By saponification of carnaiiba wax, S tiirke obtained the following bodies : 1, a crystalline paraffinoid hydrocarbon, melting at about 59 ; 2, ceryl alcohol, C 27 H 55 OH, a crystalline body melting at 76, and converted by heating with DETECTION OF CAKNAUBA WAX. 191 Carnaiiba wax when in a separate state is readily recognised by its physical characters and the results of its saponification (see page 186). It is sometimes employed as an adulterant of bees- wax, in which its presence may be recognised by the high density and melting point of the substance, by the high bromine-absorption, and by the melting point of the fatty acids produced by the saponi- fication of the neutral ethers of the sample (see page 187). The presence of carnaiiba wax in soap is best recognised by mixing the sample with sand, drying thoroughly, and exhausting the mixture with petroleum spirit (boiling at about 100) or hot toluene in a Soxhlet's tube. The residue left on distilling off the solvent is then treated in the manner directed on page 180 for the preparation of myricyl alcohol from beeswax. The weight of myricyl alcohol divided by 0"45 gives approximately the amount of carnaiiba wax in the quantity of soap employed. E. Yalenta has found carnaiiba wax in a number of com- mercial cerasins and paraffins which were characterised by their high melting points and great hardness. It is employed to impart these properties, and to give a peculiar lustre to the wax. Valenta gives the following figures showing the influence of carnaiiba wax, melting at 85 C., on the melting point of mixtures containing it. Melting point ( C.) of substance or mixture. Carnaiiba Wax. With With With Stearic Acid. Cerasin. Paraffin Wax. 58-50 7210 60-15 5 6975 79-10 73-90 10 7375 80-56 79-20 15 74-55 81-60 81-10 20 75-20 82-53 81-50 25 75-80 82-95 8175 These results show a very marked increase in the melting point of the substances by the addition even of 5 per cent, of soda-lime into cerotic acid. Fractions 1 and 2 did not exceed 1| to 2 per cent, of the entire wax ; 3, myricyl alcohol (page 180), to the extent of 45 per cent. ; 4, a diatomic alcohol, C 23 H 46 (CH 2 OH) 2 , melting at 103 '5, and converted on heating with soda-lime into an acid melting at 102*5, and having the com- position C 23 H 46 (COOH) 2 ; 5, an acid of the formula C 23 H 47 .COOH, melting at 72'5, and isomeric with lignoceric acid ; 6, cerotic acid (page 179), the chief acid of carnaiiba wax, melting at 79, or an acid isomeric therewith ; 7, a hydroxy-acid of the formula CH 2 OH.C 19 H 38 .COOH, yielding on heating with soda-lime the acid C 19 H33.(COOH) 2 , melting at 90. 192 THEORY OF LUBRICATION. carnaiiba wax. Further additions increase the melting point in a much diminished ratio. The proportion of carnaiiba wax existing in admixture with the foregoing bodies, or with japan wax, can be ascertained by deter- mining the percentage of potash required for the neutralisation of the free acid and for the saponification of the ethers of the sample (page 186). EXAMINATION OF LUBRICATING OILS. Lubrication has for its object the reduction of friction between moving surfaces. In the sliding friction of solids the magnitude of the resistance is, up to the point of abrasion, de- pendent on the character of the surfaces, and proportional to the force with which they are pressed together, though when the pres- sure is very low the resistance may be principally due to the ad- hesion, in the case of lubricated surfaces. In fluid friction, on the other hand, the resistance is proportional to the area of velocity of the surface exhibiting it ; and to the density and viscosity of the liquid. In the practical application of lubricants to the rub- bing surfaces of machinery in motion, the friction is usually com- pounded of the friction of solids and of fluids in proportions varying in each case. 1 In cases, however, in which it is practi- cable to float the moving part in the lubricant, fluid friction alone is concerned ; while in the case of slowly moving heavy machinery the resistance is chiefly due to the friction of solids. In theoretically perfect lubrication the resistance would be independent of the pressure. The more viscous the lubricant the greater the pressure which can be sustained without squeezing out the film of lubricant from between the moving surfaces ; but unnecessarily high viscosity creates unnecessary fluid friction, and the viscosity of the lubricant should therefore be proportional to the pressure. In other words, the lubricant should have just sufficient " body" or viscosity to keep the moving surfaces apart, under the maximum pressure. Hence for heavy machinery a highly viscous or even solid lubricant must be employed, 2 while the thinnest oils are suitable for delicate movements, such as exist in clocks and watches, and for the light and fast-running spindles 1 The description of the theoretical action of lubricants given in the text is in great measure condensed from a paper by Boverton Redwood (Jour. Soc. Chem. Ind., v. 121), who has ably reviewed the statements of previous writers, and done much to place the subject of viscosity on a sound basis. 2 For heavy machinery, oils are not unfrequently wholly or partially re- placed by graphite, steatite, sulphur, or soft metal. In some cases the vis- cosity of the oil is increased by an admixture, or what amounts to the same MECHANICAL TESTS FOR LUBRICANTS. 193 of cotton-spinning machines, but would be quite unsuited for oiling heavy machinery. On the whole, it must be remembered that a thick oil takes a greater power to drive, and develops a higher temperature than an oil of low viscosity ; and, as a rule, the lubricant should be as thin as is consistent with the weight of the machinery and the temperature to which the oil will be sub- jected. When the driving power is ample it will be found better and more economical to use a moderately thick oil for heavy machinery, particularly where the temperature is high, but if the driving power be inadequate it may be necessary to use a thinner oil than would otherwise have been advisable. Although the foregoing is the main principle governing the choice of lubricants, the amount of viscosity required is also dependent on the fit of the bearing surfaces and upon the character of the motion, and these conditions vary largely in each case. It is very difficult to predict the behaviour of a particular oil in practice from its trial in a mechanical testing machine. On this account, as also from the more efficient of them necessitating the use of steam-power, the ingenious machines for testing lubricating oils which have been devised by Thurston and others have not come into general use, or justified the anticipations of their inventors. The only rational plan of applying such tests is to use a series of standard spindles for testing spindle oils, standard bearings for axle lubricants, and so on for cylinder oils, &c. The necessity of so doing is practically prohibitory of the use of mechanical testers in the ordinary laboratory, and hence it is fortunate that a close relationship has been proved to exist between the viscosity of an oil and its characters as a lubricant. In other words, if a certain oil has given satisfactory results under given conditions of fit, pressure, speed, and temperature, it may be predicted with toler- able certainty that another oil of the same nature, having a similar viscosity, will yield equally good results. thing chemically, by adding alkali. The following table shows the composition of three mixtures used for lubricating the axles of railway carriages : ENGLISH. GERMAN. Summer. Winter. Tallow, Palm oil, . Rape oil, Sperm oil, . Caustic soda, Water, 504 280 22 120 1370 420 280 "35 ]26 1524 246 98 11 "52 593 Rosin grease is a mixture of similar consistency, largely employed for lubri- cating the wheels of carts, colliery trucks, &c. VOL. II. N 194 EXAMINATION OF LUBRICATING OILS. The characters which should be taken into consideration in forming an opinion 011 the suitability of a lubricating oil for a par- ticular class of work are : 1 . The viscosity or " body " of the oil at the temperature at which it is to be used ; 2. The temperature at which the oil thickens or actually solidifies; 3. The flashing point, or temperature at which the oil gives off inflammable vapour in notable quantity (see "Petroleum"); 4. The volatility or loss in weight which the oil suffers on exposure in a thin film to an elevated temperature ; 5. The "gumming" character, or tendency of the oil to become oxidised. 6. The proportion in which the fatty and hydrocarbon o i 1 s of a mixture are present ; 7. The proportion and nature of the free acid, if any, in the oil ; 8. The tendency of the oil to act on metal s. 9. The presence of mineral matters, such as the metallic bases of soaps, &c. Viscosimetry. As already stated, the viscosity or "body" of an oil is the most important criterion of its suitability as a lubricant under certain conditions, and hence great interest attaches to its satisfactory determination. It has acquired greater importance of late years owing to the rapidly increasing employment of mineral lubricating oils as substitutes for the fatty oils formerly used. Thus differ- ent specimens of any given fixed oil, such as sperm oil -or rape oil, vary in viscosity only within comparatively narrow limits at a given temperature, and hence an engineer accustomed to use a given fixed oil would, in purchasing such oil, derive little advantage from a knowledge of the viscosity of a particular sample of such oil. On the other hand, mineral lubricating oils may be manufactured of any required viscosity within comparatively wide limits, and hence it is very important that an engineer should be able to ascertain whether further supplies of this class of lubricant are of a viscosity similar to that of batches of oil previously employed. It was formerly assumed that the viscosity of an oil bore a tolerably definite relation to its density, but the fact that the specific gravity of an oil is wholly worthless as an indication of its lubricating properties is now becoming generally recognised. 1 1 Krause observed the following rates of flow at 15 C. for four varieties of mineral oil of identical specific gravity (883) : Saxony oil (paraffin), . 170 seconds. I American, . . . 550 seconds. Oelheim, . . . 355 ,, ( Scotch, , . . 585 INFLUENCE OF TEMPERATUKE ON VISCOSITY. 195 The influence of temperature on the viscosity of an oil is very considerable, and is evidently greatest in those oils which are solid or partly so at ordinary temperatures, the thicker animal oils con- taining much stearin being most sensitive to an increase of heat. Many mineral oils, however, though fluid at ordinary temperatures, decrease in viscosity so rapidly when heated as to have quite differ- ent characters at high temperatures. This fact must be borne pro- minently in mind when an oil is to be used in an engine cylinder or under similar conditions. As the temperature of a given friction surface is liable to vary considerably, preference should be given to an oil which shows the least variation in viscosity within the limits of temperature to which it is likely to be subjected. The following figures by J. Veitch-Wilson show the decrease in vis- cosity by rise of temperature of certain typical fatty lubricating oils : Number of Seconds require 1. Kind of Oil. At 15-5 C. At 49 C. At 82 C. (=60 F.) (= 120 F.) ( = 180"F.) Sperm oil, Olive oil, . 47 92 30| 37f 351 284 Lard oil, 96 38 28 Rape oil, . 108 41| 30 Neatsfoot oil, 112 40k 29i Tallow oil, 143 37 25 Engine tallow, Solid 41 26J The following are similar figures obtained in the author's labor- atory : Number of Seconds required. TCinH nf Oil Density at jvinti 01 un. 15-5 C. At 15-5 C. At 50 C. At 100 C. (=60 F.) (=122'F.) (=212F.) Sperm oil, 881 80 47 38 Seal oil (pale), 924 131 56 43 Northern whale oil, 931 186 65 46 Menhaden oil, 932 172 40 Sesame oil, . 921 168 65 50 Arachis oil, . 922 180 64 Cottonseed oil (refined), 925 180 62 40 Nigerseed oil, 927 176 59 43 Olive oil, 916 187 62 43 Rape oil, 915 261 80 45 Castor oil, 965 2420 330 60 196 VISCOSITY OF VAKIOUS OILS. Boverton Redwood (Jour. Soc. Chem. Ind., v. 128) has determined by his standard viscosimeter (page 197) the compara- tive rates of flow of a number of oils for every rise of 10 F. The following figures are the number of seconds required for 50 c.c. of each oil to flow through an orifice out of which an equal measure of water at 60 F. ( = 15'5 C.) ran in 25 J seconds : Temperature; F. Refined Rape Oil. o 1 3 1 i Refined Rape Oil. Refined Rape Oil. Beef Tallow. Sperm Oil. Neatsfoot Oil. American Mineral Oil. Sp. gr,=885. American Mineral Oil. Sp. gr.=913. American Mineral Oil. Sp. gr.=923. Russian Mineral Oil. Sp. gr.=909. Russian Mineral Oil. Sp. gr. =915. Russian Mineral Oil. Semi-solid. 50 7124 620 145 425 1030 2040 2520 60 540 177 470 105 295* 680 1235 1980 70 80 405 326 406 405* 407 137 113 366 280 90 73 225 171 485 375 820 580 1320 900 90 260 96 219 63* 136 26'2 426 640 100 110 213* 169 ... ... ... 80* 70* 175 147* 54* 50 111 89* 200 153 315 226 440 335 1015 739* 120 130 147 123* 146 147 147* ... 60* 57 126 112 47 44| 78 63* 126 101 174 135* 245 185 531 398* 140 150 105* 95* 106* 106* 106 ... 51 49 88* 75* 41 37* 58 52 82 70* 116 95 145 115 317* 250 160 85 47 i 70 46 63 l 83* 93* 200 170 76 46 62 58 70* 77* 161 180 69 441 56i 52* 61* 67* 134* 190 64* 43 53 47* 56* 61 115* 200 210 58* 54 57* 57* 58* 54* 42 41 50* 484 42 40 48* 54 99 sr> 220 54 39 17 38 77 230 47* 37 46 704 240 45} 36 44i eil 250 43* 40 35 44 5* 260 . 34 431 54 270 33 " 4gi 280 290 i?j e ... 32 31 a* ... ... 46* 46 300 ris 30 38 424 ^ ' On examining the results recorded in the foregoing table, it will be observed that sperm oil is remarkable for the compara- tively slight reduction in its viscosity caused by increase of temperature, a property to which the value of this oil as a lubri- cant for use under very varied conditions is probably due. The Russian mineral oils lose their viscosity with an increase of temperature more rapidly than American oils of the same specific gravity, but in both classes the reduction is most rapid in the case of the most viscous oils, and, as the Russian oils have a higher viscosity than the American, a more rapid reduction in the former case might be anticipated. The viscosity of oils is usually determined by ascertaining the DETERMINATION OF VISCOSITY. 197 time that a certain weight or measure of the sample takes to flow through a given aperture. 1 The elementary form of apparatus for determining viscosities consists of a glass tube drawn out to a narrow orifice at the lower end. The tube is supported in a vertical position and filled with the oil to a certain mark, the orifice being closed by the finger. The oil is then allowed to flow out till a lower mark is reached, or till a definite measure has been received in a graduated vessel, the number of seconds required being noted. The viscosity of oils being affected to an important extent by very slight variations of temperature, it is very desirable to sur- round the viscosity-tube with an outer tube or cylinder containing water at the desired temperature; for high temperatures a less volatile liquid than water might be substituted. It is desirable in all cases to compare a sample of oil with others of known quality and origin, as the viscosity-figures obtained by the use of one apparatus of the above kind are not directly comparable with, or even capable of strict conversion into, those yielded by others. A simple method of determining viscosities, applicable to small quantities of oil, has been recently described by E. J. Mills (Jour. Soc. Chem. Ind., v. 148). With a view of avoiding the irregularities and discrepancies due to the use of the ordinary form of apparatus for determining vis- cosities, Boverton Eedwood has recently devised an improved instrument (fig. 11) which is capable of being standardised, and is likely to come into extended use. 2 The viscosity tube (A) is made of copper thickly electroplated, and is 3J inches high by If inch internal diameter. In practice, however, it is invariably filled to a height indicated by the contact of the surface of the contained oil with a bent wire soldered to the side of the tube, and having its point (B) projecting vertically upwards. The orifice is a hole 1 A viscosimeter, based on an entirely different principle, has been devised "by Napier & Strong, and improved by E. G. Cockrell. A small paddle-wheel is caused to revolve in the oil by means of a falling weight, and the number of seconds required by the latter, after reaching a uniform speed, to fall a certain distance expresses the viscosity of the oil. The results are readily obtained and are exceedingly constant, and for technical use by oil-merchants and others the apparatus is likely to be found very useful. The method has the advantage of being independent of the density of the oil, and is applicable to samples containing suspended matter. On the other hand, the figures are complicated by the friction of the wheel-work, and it is doubtful if different apparatus could be constructed to give identical results. 2 See Jour. Soc. .Chem. Ind., v. 126. The apparatus, properly standardised, may be obtained from James How & Co., 73 Farringdon Street, B.C., who are the sole makers. 198 REDWOOD'S VISCOSIMETER. of a definite size drilled in agate (c), but glass might doubtless be substituted without affecting the accuracy of the indications. The friction of the flowing oil against the sides of a long tubular orifice Fig. 11. notably affects the indications of the instrument, and hence the tubular portion of the orifice is made as short as practicable. The upper surface of the agate is cup-shaped, so as to fit the bulb of the REDWOODS VISCOSIMETER. 199 thermometer (D), which can thus be used as a plug, but the instrument is also supplied with a spherical plug of electroplated copper attached to a wire. The viscosity-tube is surrounded with a cylindrical reservoir of copper (E), which can be filled with water or other fluid, and readily brought to and maintained at any desired temperature. For temperatures below 100 C., water is the most convenient fluid to use in the reservoir. Above that temperature, paraffin or mineral lubricating oil of high boiling point may be used. The fluid in the reservoir can be heated by a gas-flame placed under the projecting portion F, and can be agitated by gently moving the inclined paddles by means of the handle H. When the temperature employed is considerably above that of the laboratory, the agitator should be kept in gentle motion through- out the experiment. Care must also be taken that the temperature of the oil in the inner cylinder is maintained constant, as a differ- ence of 1 or less will make an appreciable difference in the rate of flow of some oils. In using Redwood's viscosimeter, the liquid in the reservoir should first be brought to the required temperature, and the oil to be tested, previously brought to the same temperature, should then be poured into the inner cylinder until the level of the liquid just reaches the point of the gauge (B). A narrow-necked flask, hold- ing 50 c.c. to a point marked on the neck, is placed beneath the jet in a vessel containing a liquid of the same temperature as the oil. The ball-valve is then raised, and the number of seconds required for 50 c.c. of the oil to flow out is carefully noted in the usual way. At least two experiments should be made, and the results should be closely concordant. Before determining the viscosity of an oil, the sample should be filtered if not perfectly clear, as any suspended matter or globules of water will be liable to partially obstruct the orifice, and so cause a false result to be obtained. If the oil-cylinder requires to be wiped out, paper rather than cloth should be employed, as filaments of the latter may be left adhering. In employing Ked wood's or the older forms of viscosity appara- tus, it is essential that the oil at the commencement of each experi- ment should stand at a constant height, and that the same measure of oil should be allowed to flow out. If these conditions be not observed strictly, most discordant results will be obtained, owing to the influence the pressure or head of oil has on the rate of flow. To obviate this, the writer makes an addition to Redwood's apparatus, by which a constant head of oil, and consequently perfectly regular flow, is obtained. For this purpose, it is merely necessary to fit to the oil-cylinder an air-tight cover, as shown in 200 APPARATUS WITH CONSTANT HEAD. figure 12. The cover is perforated by two holes fitted with short tubes, one of which (A) is furnished with a tap (B), while the other has another tube screw- ing air-tight in it. This tube c is prolonged on two sides in contact with the agate-orifice, while the angles of the inverted V-shaped slits cut on each side terminate at D, exactly 1J inches higher. The cylinder is com- pletely fined with oil before commenc- ing an experiment, the tap B closed, and the orifice opened till the oil sinks to the level of D in the inner tube. Air then bubbles regularly in at D, and when this is observed to happen, the oil is collected in a grad- uated cylinder. Any volume from 10 to 50 c.c. may be allowed to run out, as the oil gradually falls in the upper part of the cylinder, but is maintained constantly at the level D. Fi g- 12.; Experiments made in the author's laboratory prove the flow to be extremely regular ; and the modi- fication has the additional advantage of allowing the viscosity to be determined from the flow of a very moderate measure of oil, whereas if 50 c.c. be of necessity the volume collected the observation sometimes becomes a very tedious one. The results obtained by the comparative testing of different oils by the closed test agree with those yielded by the open apparatus. The temperature at which the viscosity of an oil should be determined is evidently dependent on the conditions under which it is to be employed; but it is desirable to test each sample at two different temperatures tolerably widely separated, so as to obtain an indication of the extent to which the viscosity of the oil diminishes on heating. For oils to be used for lubricating bearings exposed to the air, 20 C. and 60 C. are suitable temperatures, but cylin- der oils may be advantageously tested at 100, 120, and 150 C. In recording the viscosities of oils it has hitherto been usual simply to state the number of seconds required by the oil to run through a certain orifice at a given temperature, and, to render such figures comparative, they have usually been referred to rape oil as a standard. As, however, different samples of rape oil differ sen- sibly in viscosity, the results obtained by different observers have, for this and other reasons, not been capable of accurate comparison. COMPARISON OF VISCOSITIES. 201 If, however, a perfectly defined and constant apparatus such as Redwood's be employed, it becomes a simple matter to refer different samples to a standard. Water possesses too little vis- cosity to make it a desirable liquid with which to compare lubri- cating oils. Glycerin can be diluted with water to any required viscosity, and the specific gravity of the standard liquid being once ascertained a fresh standard can always be prepared at will. It is evident, however, that if the average viscosity of rape oil be once determined by the careful testing of a number of specimens, the average thus obtained can be regarded as the viscosity of a standard rape oil, and if a constant apparatus be employed, the results can always be expressed in terms of such standard. Red- wood has therefore determined the viscosity of a considerable number of samples of genuine rape oil, and finds that the average time required for 50 c.c. of the oil at 60 F. (=15 '5 C.) to flow out of a Redwood's viscosimeter is 535 seconds, 1 water under similar circumstances running out in 2 5 '5 seconds. Taking therefore the viscosity of standard rape oil at 100, the viscosity of any other oil of the same density will be found by multiplying by 100 the time in seconds required for 50 c.c. to flow through the orifice, and dividing the product by 5 3 5. If the density of the sample be different from that of rape oil, the figure thus obtained should be multiplied by the specific gravity of the sample at the temperature of the experiment, and divided by 915 (the specific gravity of refined rape oil at 60 F.). The rule is expressed by the following equation : Seconds of flow X 100 X sp. gr. of sample 489525 - THE SOLIDIFYING POINT of a lubricating oil can be determined as described on page 23. It is a character of such obvious im- portance in judging of the suitability of a lubricating oil for a particular purpose that nothing need be said of it here except that, as a rule, an oil is required to remain liquid at the temperature at which it is employed. THE FLASHING POINT, or temperature at which an oil gives off a notable quantity of inflammable vapour, may be determined in the manner described in the section on " Petroleum." The flash- 1 The author finds that pure glycerin (Price's), diluted with water till it has a density of 1226 '0 at 15 '5 C. ( = 60 F.), requires 535 seconds to run out of Redwood's apparatus, and hence has a viscosity equal to that of his standard rape oil. 2 For Poiseuille's formula for calculating the absolute viscosity of liquids, see Jour. Soc. Chem. Ind. t v. 148. 202 FLASHING POINTS OF OILS. ing and boiling points of the fatty oils are so high as to be beyond the temperature to which they are subjected in use ; but as many lubricating oils are now composed largely or entirely of hydrocar- bon oils of low volatility, the flashing point becomes a character of importance. A low flashing point is generally due to the presence of naphtha. Some oils, sold for lubricating purposes, have flash- ing points so low as to bring them under the legal definition of " petroleum." As a rule the flashing points of the pale lubricating oils manufactured in the south of Scotland from bituminous shale range from 130 to 180 C. ; and of the darker oils and greases from 180 to 230 C. In the case of oils employed for engine cylinders, the flashing point should certainly not be lower than 200 C., nor the boiling point below 260 C. The importance of a high flashing point is twofold in such cases. There is less chance of inflammation, and the india-rubber packing of the cylinders is less liable to be destroyed. THE Loss BY HEATING the oil is also an indication of the pre- sence of volatile constituents, which may cause a serious increase in the amount of oil consumed in practice. To observe the behaviour of the oil, a known weight should be placed in a watch-glass, wide beaker, or flat porcelain dish, and exposed for twenty-four or forty-eight hours in an air-bath to a temperature similar to that to which it will be exposed in practice, and the residual oil weighed. The test is chiefly of value for mineral lubricating oils. THE OXIDISABILITY or DRYING CHARACTER of an oil is likewise indicated by the test last described, the increase in the weight of different samples when exposed under the same conditions being a measure of their tendency to oxidise. The method of making the test may be varied (see pages 51 and 122), but comparison between different oils is difficult unless the mode of operating has been identical. 1 " Gumming," or tendency to dry, if existing to any notable extent, renders an oil unfit for use as a lubricator. The hydrocarbon and terrestrial animal oils are practically free from 1 The following furnishes a useful practical means of ascertaining the tend- ency of an oil to dry or gum : A plate of smooth iron or glass having parallel grooves on it, or a piece of corrugated zinc, such as is used for roofing, about six feet in length, is supported so that one end is raised an inch above the other. Equal measures of the oils to be tested are then taken up with a pipette, and placed, as nearly as possible at the same time, at the upper end of the inclined plane. The rate of flow of each oil is then observed from day to day. Some keep ahead at first, but gradually lose speed owing to their tend- ency to gum or dry. A good lubricating oil will continue to flow for six or eight days ; while a drying oil, like linseed, though making good progress at first, will soon become stationary. The following table, taken from Apple- ton's Dictionary of Mechanics, shows some actual results obtained in the GUMMING AND ACIDITY OF OILS. 203 drying tendencies ; but " fish " oils are less perfect in this respect, with the exception of sperm and bottlenose oils, which have pecu- liarities which distinguish them from all others (see page 169). a The vegetable oils differ greatly in their drying properties, but even the so-called non-drying oils, like rape and olive (see page 110), are not wholly free from a tendency to thicken. An admixture of hydrocarbon oil notably reduces the tendency of a vegetable oil to thicken, and correspondingly diminishes its liability to generate sufficient heat to cause spontaneous combustion. On the other hand, the presence of resin causes a notable increase in the gum- ming tendency of an oil. THE FREE ACID of an oil and its tendency to act on metals are characters which are closely related. A perfectly neutral oil has no action on metals at ordinary temperatures, and experiment shows that the corrosive action increases in direct proportion with the quantity of free acid present (see page 98). Many cases of so-called " clogging " or commonly attributed to oxidation, are really due to the action of the free acids on the metal bearings of the machinery, with conse- quent production of soaps. The corrosion of bearings by oils has not received the attention it deserves, as the wear and tear of the metal and the thickening of the oil have been attributed to other causes. Liquid oils appear to corrode metals very evenly, so that the effect is not readily observed, but with solid fats it is very different. 1 manner described. The figures give the length of run of each oil in inches. It will be observed that the sample described as " common sperm oil " gave better results than that classified as " best " : " gumming " of oils, Best Sperm Oil. Common Sperm Oil. Gallipoli (Olive) Oil. Lard Oil. Rape Oil. Linseed Oil. First day, . 32 19 10 io; 14 17* Second day, 50 45 14 104 18 18 Third day, 53 55 18 10| 19 18 Fourth day, 54 59 isi loi 19 18* Fifth day, 54 62 19* 111 191 18i Sixth day, 54 64 20^ still ]9i still Seventh day, 54 67 21 19* Eighth day, 54 674 214 ... still ... Ninth day, 68 21| 1 In a case observed by Archbutt, a steel rod which was immersed in axle-grease made with soap, water, tallow, and palm oil containing a good deal of free acid, became deeply pitted in several places in a few days, and stained all over. In another instance, a mixture of 1 part of mineral oil with 9 of olive oil which contained 4 '7 per cent, of free acid was employed in. 204 FREE ACID IN LUBRICATING OILS. Although, when freshly manufactured, an oil may be free from any trace of acid, it is not unlikely to acquire a very sensible acidity in time. This is true of many animal and vegetable oils, which have a tendency to become acid by keeping, through a partial splitting up of the glycerides into glycerin and free fatty acids. Hydrocarbon oils are wholly free from this tendency, but it must be remembered that either a fatty or a hydrocarbon oil which has been over-refined by means of sulphuric acid may develop serious acidity by keeping or exposure to heat. 1 The presence or formation of free acid in an oil being the chief if not the only cause of its tendency to act on metals, the results published by various observers, showing the amounts of iron and copper dissolved in equal times by different oils, have no interest or meaning apart from the particular samples of oils examined, the action on the metals being simply a function of the free acid the oils happened to contain. Although, at the time of using, an oil may be wholly free from acid reaction, it may, if of animal or vegetable origin, readily become acid, and hence corrode the metallic surfaces it is employed to lubricate. This is notably the case when the oil is exposed to the action of high-pressure steam, as under such conditions all the fat oils suffer decomposition more or less readily, with formation of free fatty acids and glycerin (see page 29). The free fatty acids formed by the hydrolysis of the oil readily act on the metal of the cylinder and produce an iron soap which clogs up the machinery in a very troublesome manner. It is a curious fact that the soaps of iron and other of the heavy metals (especially the oleates) are soluble in hydrocarbon oils, though insoluble in water, the reverse being the case with the soaps of the alkali-metals. As a consequence of this, the iron soap produced in engine-cylinders lubricated with tallow, castor oil, or other fatty oils, gets dissolved out whenever a change is made to a mineral lubricating oil. This fact is well known to engineers, but it has often been wrongly attributed to an abundant production of " gummy matter " by the mineral oil itself. In consequence of the tendency of fatty oils to become decom- posed by high-pressure steam they are ill-suited for use in engine- the axle-box of a railway carriage. After being in use for about three weeks, although no erosion was "noticed," the oil had become very viscous. After removing a good deal of hair and dust, the clarified oil was still viscous, and of a deep green colour. On agitation with ether and dilute acid a solution containing much copper and zinc was obtained, while on evaporating the ethereal layer the residual oil was found to have the same colour and viscosity as the original oil before use. PRODUCTION OF FREE ACID IN OIL. 205 cylinders, at any rate in an unmixed state, and in many instances they may be wholly replaced with advantage by mineral oils of low volatility and high viscosity. In some cases it is found difficult to obtain mineral oil having a sufficiently high viscosity at the temperature at which it is intended to be employed, and an addition of castor oil is conse- quently made. There then arises the practical inconvenience that mineral and castor oil are mutually soluble only to a very limited extent, but by addition of some other oil, such as tallow oil, per- fect union can be effected. The " blown oils " now manufactured as substitutes for castor oil (page 129) are readily miscible with mineral oil, but their use is not to be recommended. A mixture of mineral oil with fatty oil, when used in an engine- cylinder, appears to exert a less corrosive action on metals than a fatty oil alone, or than might be anticipated from the proportion of fatty oil in the mixture, the mineral oil appearing to prevent the decomposing action of the steam on the fatty oil. It is evident from the foregoing considerations that, in making an examination of a lubricating oil, its tendency to act on metals should be tested as far as possible under the circumstances and at the temperature of its use in practice. Thus, not only should the nature and proportion of free acid present in the original oil be ascertained, as described on page 75, but in some cases this deter- mination should be supplemented by a titration of the oil after it has been exposed to a high temperature in contact with water. 50 grammes of the oil and an equal measure of water should be heated in a closed bottle immersed in boiling water. The contents are frequently agitated, and after six or eight hours the bottle is opened and the oil and water separated. They are then titrated separately with decinormal alkali and phenol-phthalein (page 76). The acidity of the aqueous liquid will generally be due to free sulphuric, acid, produced by the decomposition of sulphonates in the original oil, and, if found in notable quantity, proves the oil to be of an objectionable character. The acidity of the oily stratum will represent the fatty acids formed by the action of the water, plus the fatty acids previously present, which latter can be ascer- tained by titrating the original oil. In the case of cylinder oils it may sometimes be desirable to heat the oil and water in a sealed tube contained in a bath of boiling saturated solution of calcium chloride, which will give a temperature corresponding to an internal pressure of 10 atmospheres, or about 150 Ibs. per square inch, but in most cases a temperature of 100 C. will suffice. Useful and interesting results can be obtained by exposing samples of lubricating oil in flat porcelain dishes. Bronze coins, 206 ACTION OF OILS ON METALS. or coils of copper or iron wire, are partially immersed in the oils. When copper is employed, in the course of a day or two many samples of oil acquire a bright green colour from dissolved oleate of copper, but in other cases the extent of the action is much disguised by the brown colour of the oil itself. If, however, the oil be transferred to a separator (page 83), and shaken with ether and dilute sulphuric acid, the dissolved metals pass into the acid liquid. On separating this from the ethereal layer and adding excess of ammonia, the depth of the blue coloration produced is a fairly accurate measure of the action of the oil on the copper. If iron wire has been employed, the depth of the red coloration produced by adding a thiocyanate instead of ammonia, will serve to indicate the extent of the action. The method, which is due to Archbutt, is capable of being applied quantitatively, and gives use- ful comparative results when employed under constant conditions. In some cases useful results are obtainable by exposing oils in contact with metals at an elevated temperature, and then ascertain- ing the extent of the action as just described. W. Fox (Analyst, viii. 116) considers that the value of a lubri- cating oil is inversely as its tendency to absorb oxygen when heated to 100 C. in contact with a metal, such as finely-divided lead. His figures show, however, that the drying tendency of the oil employed is the chief factor concerned, though, for reasons pointed out on page 122, the amount of oxygen absorbed is not an accurate criterion of this property. MINERAL MATTERS can be detected in the residue left on igniting the oil. Free alkali can be determined by titrating the oil in presence of alcohol with standard acid and phenol-phthalein, and that existing as soap by using methyl-orange as an indicator. Aluminium palmitate and oleate are now added to mineral oils to increase the viscosity. On agitating such oil with ether and dilute acid, and separating the aqueous layer, a white gelatinous preci- pitate will be thrown down on adding a slight excess of ammonia. APPENDIX TO THE CHAPTER ON FIXED OILS. The products resulting from the saponification of the various fixed oils have been described generally on page 30 et seq., but some of the more important require more detailed consideration. The following four sections treat of the "Higher Fatty Acids," " Soaps/' " Glycerol," and " Cholesterin." Some other saponi- fication-products, such as cetyl and myricyl alcohols, have already been described, as have certain of the fatty acids themselves. FATTY ACIDS OF HOMOLOGOUS SERIES. 20 7 HIGHER FATTY ACIDS. Under the denomination of "fatty acid s," used in its widest sense, are included the whole series of homologous acids of which formic acid is the lowest member, together with the various homo- logous acids of the acrylic or oleic series, the peculiar acids ob- tained by the saponification of castor and linseed oils, and many others. The lower acids of the formic, acetic, or stearic series have been fully considered in Volume I. page 404 et seq. The following tables give some particulars respecting such higher fatty acids as are of interest or importance as constituents of the fixed oils or fats. The members containing an even number of carbon atoms in the molecule appear to occur more commonly than the intermediate acids of the series. Some information as to the analytical characters of caprylic, pelargonic, and capric acids will be found in Volume I. Palmitic, stearic, and oleic acids are so important and of such frequent occurrence that they are described at length in subsequent sections. Further information respecting arachidic, brassic, linoleic, and ricinoleic acids will be found in the sections treating of the oils of which they are especially charac- teristic, namely, earth-nut oil, rape oil, linseed oil, and castor oil. The methods of detecting or determining the lower homologues of the stearic series are described on pages 37, 45, and 156. It will be noted that the acids of the stearic series become less fusible with an increase in the number of carbon atoms. Baeyer has shown, however, that the rise in the melting point is not strictly regular, inasmuch as an acid of the stearic series containing an uneven number of carbon atoms always possesses a lower melting point than the preceding member of the series containing an even number of carbon atoms. The fact is evident from the melting points recorded in the table on next page. In a similar manner, the boiling points of the acids of the stearic series rise with an increase in the number of carbon atoms. 1 The higher members cannot be distilled under the ordinary atmospheric pressure without suffering more or less decomposition, but they may be distilled without alteration under diminished pressure. The table shows the boiling points of some of the acids of the stearic series under a pressure of 100 millimetres of mercury. 1 According to Kingzett, however, cacao butter contains the glyceride of theobromic acid, to which he attributes the formula C 64 H 130 2 (Jour. Chem. Soc., xxxiii. 38). As the melting point of this acid is only 72 C., it is clearly of anomalous character. 208 ACIDS OF THE STEARIC SERIES. tained by yl alcohol, , and boils c a ing id a . so-oct oxid is at II r-lj: 411 Jijtl-si ; o+aoa>5fc4c6 * *B * joffe 18 ill ^ ,u S S I"" 1 CO .S c6 -*-> i^j'ss^t?*!' . Jlillisilll ilcjM 1 *!! 1 ! ^ ^ o 1* so o ric acid, from oil elts at 52-53. from spermaceti. cid, from oil of er, melts at 55. Agaricus integer, Benomarg of ben, Ceta'c acid Iso-cetic medicin Acid from iifii I! Hilt ill 33 d^-3 6 i.2 *H" Jill -rf? 15 ^i^lrf.^l If S'o 1| S-S aS HP 4 S ^5-s s .o 'a> c wj ^toMS 611 ^" 22J8- illfil ill ""o S^' "08 o^' g-c3^ gj^ 55 ^ S^TJ 5.2 rt -|l !!il I flSSB s-e S iijic -il-^i fa. 03 ^ C 4-- illjv a^5l?9 fcllw c? ACIDS OF THE STEARIC SERIES. 209 ^ > D ty < Is" 5 .' 830 3 - -PI o> <$i3 g? 32 *a OJ D ^ O ri -S S-u. ! Ill 1 1:1 irilfl P 9 S S feHi -H .ps^ ^^-S CC e\* 1J . i l! 1 ^ i 5?.n sift * =S P* *l!if g ^^l^lg^gla -Illjill ||| %! 11 ! I : o i a; C 18 H 36 2 w C 20 H 40 2 C 21 H 42 2 o" a ?j o o C 26 H 52 2 ZO W H :Z O B VOL, II. 210 ACIDS OF THE OLEIC SERIES. c c 4 b d |l S c* 5 -"So pi i i I | 3 I 1 * i 2.c '5 Ho f S Mf .i i H 1 |a 1S M -S1|= = ; jj illl p|illii|8 O O Q M II! S 5 : ^ -' w i Vi sg II n ^=0 I El * e! ** ^^ c 3 05.2 OS. & "S E 6 ACIDS OF THE LINOLEIC AND RICINOLEIC SERIES 211 . o o ! !i f |jfi | II Jllsf, af ; 05 tie .s.s -s P so -a i ^* . t! 111 212 CHARACTERS OF FATTY ACIDS. General Reactions of Fatty Acids. All the fatty acids named in the foregoing tables are practically insoluble in water, but are mostly soluble in alcohol, ether, and fixed oils. In alcoholic solution they usually exhibit a more or less marked acid reaction, and both in solution and in the molten state decompose the carbonates of the alkali-metals. ' The resultant salts are commonly called "soaps." The fatty acids of the different series formulated in the foregoing tables present certain marked points of difference and general reactions of interest, of which the following are the chief : A. The higher acids of the stearic series are solid at the ordinary temperature. They are saturated bodies, and hence do not form additive-compounds with bromine and do not react with Hiibl's reagent (page 48). They may be heated with caustic potash to a very considerable temperature (e.g., 300 C.) without change. They are equally unacted on by treatment with phosphorus and hydriodic acid. The lead salts of the acids of the stearic series are insoluble in ether. B. The higher acids of the oleic series have lower melting points than the acids of the stearic series containing the same number of carbon-atoms. They form additive-compounds with bromine of the formula C n H 2n _ 2 Br 2 2 , and react sharply with Hiibl's reagent to form analogous compounds. When gradually heated with caustic potash to about 300, they yield potassium acetate and the potas- sium salt of an acid of the stearic series containing a number of carbon-atoms two less than the original acid of the oleic series employed :C 18 H 34 2 + 2KHO = C 2 H 3 K0 2 + C 16 H 31 K0 2 + H 2 . Heated rapidly with excess of alkali, certain of the acids of the oleic series yield sebacic acid, C 10 H 18 4 , as a characteristic pro- duct (page 234). A remarkable reaction of oleic acid and its true homologues is the formation of an isomer of higher melting point under the influence of nitrous acid. This reaction is common to their glycerides (page 57), and is also exhibited by ricinoleic acid and its glyceride. The imperfect reaction of brassic acid and its glyceride (contained in rape oil) with nitrous acid renders it doubtful if their constitution is properly understood. The acids of the oleic series form lead salts soluble in ether. C. Linoleic acid and its homologues combine with either Br 2 or Br 4 , and react with a larger proportion of Hiibl's reagent than do the acids of the oleic series. They have a very low melting point, are not visibly affected by nitrous acid, and form lead salts soluble in ether (see also page 116). D. Ricinoleic acid combines with Br , does not oxidise in the TITRATION OF FATTY ACIDS. 213 air, is gradually solidified by nitrous acid, and forms a lead salt soluble in ether (page 127). Recognition and Determination of Fatty Acids. The methods available for the detection and to some extent for the determination of the higher fatty acids, are based on the characters just described. In many cases it is unnecessary to Affect an actual separation of the fatty acids of a mixture, it being sufficient to ascertain their joint amount, or to determine indirectly and approximately the proportion of the acids of different origins known to be present. METHODS NOT INVOLVING SEPARATION. a. Free fatty acids can be accurately determined by titration in alcoholic solution with standard caustic alkali, using phenol- phthalein to indicate the point of neutrality. The mode of operat- ing is fully described on page 76. Glycerides, hydrocarbon oils, and other neutral bodies do not interfere, but free mineral acids must first be removed by agitation with water, or determined by titration in alcoholic solution with methyl-orange as indicator, and resin acids must by separated or duly allowed for. In the case of a mixture of several fatty acids the result is best expressed in terms of the principal or most characteristic acid present, and in most cases such a mode of statement gives a close approximation to the true total of the free fatty acids present. Conversely, when the substance under examination consists wholly of a mixture of fatty acids, titration with standard alkali suffices to ascertain the mean combining weight of the mixed acids. This is found by dividing the number of milli- grammes of fatty acids employed for the titration by the number of cubic centimetres of normal alkali required for neutralisation. 1 In cases of a mixture of two homologous acids, the nature of which 1 The mean combining weights found in the author's laboratory for the fatty acids from various oils are given on page 215. The following results have been communicated by other observers : Source of Fatty Acids. Combining Weight. . Observer. Tallow, lard, or olive oil, Castor oil, 270 to 285 290 to 295 C. R. Alder Wright. 196 to 204 Palm oil .... 273 A. Norman Tate. Palmnut oil ... 211 E. Valenta. Cottonseed oil, .... Sesam.6 oil . . 275 286 i* 214 TITEATTON OF FATTY ACIDS. is known or can be ascertained by other means, the result of the titration gives the means of ascertaining the proportions in which the two constituent acids exist in the mixture. An example of the application of the method to this purpose is given on page 220. b. The method ofKoettstorfer (page 40) may be regarded as a process of approximately ascertaining the mean combining weight of the fatty acids of an oil without actually isolating them. If the saponification-equivalent o$ the oil be multiplied by 0'95 the mean combining weight of the acids will be obtained with tolerable accuracy. The method is, of course, only applicable to oils yield- ing approximately 95 per cent, of fatty acids on saponification. With oils like shark and sperm oil and the true waxes the process is quite useless. On the other hand, in the case of the pure glycerides it is in some respects preferable to a titration of the previously isolated fatty acids, as there is less danger of altera- tion by oxidation or the loss of soluble fatty acids in the course of preparation. c. The titration of a mixture of oleic acid with acids of the stearic series by means of Hiibl's reagent (page 48), allows the former constituent to be determined with considerable accuracy. As 282 parts of oleic acid, C 18 H 34 2 , assimilate 254 parts of iodine, I 2 , the iodine-absorption divided by 0'9 gives the percentage of oleic acid present. Linoleic acid and its homologues assimilate I^ 1 and hence their presence renders the determination of the oleic acid excessive, but the method is still applicable if the mode of calculation be modified accordingly. Oleic and homolinoleic acids have so very nearly the same molecular weight (282 :280), that the latter may be regarded as absorbing twice as much iodine as the former, or 180 per cent, against 90. Hence, if 90 be- sub- tracted from the observed iodine-absorption of the mixed acids, and the difference be divided by 0*9, the dividend will be the number of parts of homolinoleic acid in 100 parts of the mixture. If acids of the stearic series are also present, they must be sepa- rated or duly allowed for in making the calculation. 2 d. Much useful information respecting the fatty acids present in 1 The iodine-absorption of pure linoleic or homolinoleic acid has not been hitherto ascertained, but the mixed acids from genuine linseed oil gave the value 160, which would represent about 89 per cent, of homolinoleic acid, a highly probable result. 2 Thus, if the percentages of stearic, oleic, and homolinoleic acids in a mix- ture of the three be represented respectively by the symbols s, o, and Ti, and iodine-absorption by A, the proportions of the liquid acids present will found by the following equations : sis known : o*= 200- I'll A : and A = 100-o-s. FATTY AHIDS FROM VARIOUS SOURCES. 215 a mixture can be obtained by determining the melting point or solidifying point of the substance. When the mixture consists merely of two acids of the stearic series, the determination affords a means of approximately ascertaining the relative propor- tions of the two constituents. The melting points of various mix- tures of the homologous acids of the stearic series fiave been deter- mined by Heintz, and are given in a tabular form on page 221 et seq. The melting and solidifying points of the fatty acids from different fixed oils are more or less characteristic of their origin, as also are their specific gravities and mean combin- ing weights. The following table gives a number of data of this kind obtained in the author's laboratory i 1 Characters of Separated Insoluble Fatty Acids. Kind of Oil. Specific Gravity. Melting Point ;C. Solidifying Point ; C. Combining Weight. At 15'5C. At 98-99C. r Olive oil, solid 843-0 26-0 21-0 279-4 Arachis oil, . solid 846-0 29-5 28-0 281-8 Rape oil, solid 843-8 19-5 18-5 321-2 Cotton oil (pressed), Sesame oil, . solid solid 8467 35-0 23-0 32-0 18-5 337-2 286-5 Linseed oil, . 923-3 861-2 24-0 17-5 307-2 Castor oil, . 950-9 896-0 306-6 Palm oil, solid 836-9 50-0 45-5 269-6 Cocoanut oil, solid 835-4 24-0 20-5 ... Japan wax, . solid 848.2 56-0 53-0 265-3 Myrtle wax, . solid 837-0 47-5 46-0 243-0 Lard, . solid 844-5 44-0 39-0 278-0 Northern whale oil, 907-6 859.5 2987 Sperm oil, 899-0 ... ... 289-4 Bottlenose oil, 896-5 ... ... 294-6 1 The fatty acids were prepared from the oils in the manner described on page 38. That is to say, the oil was saponified with alcoholic potash, the alcohol evaporated, and the residual soap dissolved in hot water and decom- posed by dilute sulphuric acid. The liquid having been well boiled, the separated fatty acids were filtered through paper. The higher alcohols of the sperm and bottlenose oils were removed by agitating the solution of the soap with ether, the ethereal layer separated, and the ether dissolved in the aqueous liquid got rid of by warming, before liberating the fatty acids. In the case of the other oils the trifling proportion of unsaponifiable matter was ignored, anl !I li-II 03 g g-C M rfg 5= J3 r S3 S 'O aJ 3 | 5 < s 252 WATER IN SOAPS. From the preceding list of the numerous substances occurring as frequent or occasional ingredients of commercial soaps, it is evident that the complete analysis of soap is sometimes a difficult and tedious operation. In the great majority of cases, however, the examination may be restricted to a determination of the leading constituents, and of these some have a greater or less import- ance according to the purpose for which the soap is intended to be used. Manufacturers' Soaps should be tested for the proportions of water, total alkali, and crude fatty acids ; while the percentages of caustic alkali, alkali as carbonate and silicate, combined fatty and resin acids, and free fatty acids and unsaponified oil are secondary determinations which are frequently of considerable importance. Household and Laundry Soaps should be tested for the pro- portions of water, alkali as soap, alkali in other forms, and total fatty acids. Carbolic acid should also be determined in soap said to contain it. Toilet and Fancy Soaps should be tested for water, alkali as soap, alkali in other forms, fatty and resin acids, glycerin, sugar, and insoluble matters. Medicated Soaps should be specially examined for the propor- tion of the active or quasi-active constituent said to be present, such as carbolic acid, thymol, coal tar, vaselene, &c., &c. The table on page 251 exhibits a systematic scheme for the complete analysis of soap of a very complex kind. 1 With the sub- sequent detailed instructions and extensions it includes methods of determining or detecting the great majority of the substances met with in commercial soaps. The plan of procedure is so arranged as to permit of the examination of ordinary soaps being very simply conducted, while allowing any special ingredient to be sought for and determined. A. DETERMINATION OF WATER. The determination of the proportion of water in soap is import- ant, and requires considerable care to ensure accurate results. If the soap be a solid one, a fairly representative sample should be reduced to fine shavings by scraping with a knife. A known weight is then exposed for some time to a temperature of 40 or 50 C., the heat being gradually raised to 100 C., and continued 1 The table itself is mainly based on the scheme drawn up by C. R. Alder Wright and C. Thompson (Analyst, xi. 47), which is a modification of that of A. Leeds (Chem. News, xlviii. 67), who appears in great measure to have derived his method from the first edition of this work. UN SAPONIFIED MATTERS IN SOAP. 253 at that temperature as long as loss of weight is observed. The soap should not be allowed to melt. A better method is to dis- solve about 2 grammes of the soap in the minimum quantity of hot strong alcohol, and to pour the liquid on a known weight of clean dry sand, which is then exposed with frequent stirring to a temperature of 110 C. 1 The water in soap may also be deter- mined rapidly, and with ample accuracy for most purposes, in a manner recommended by W atson Smith (Jour. Soc. Dyers and Colourists, i. 31). From 5 to 10 grammes of the finely divided sample should be placed in a large porcelain crucible, set in a sand bath which is heated by a small Bunsen flame. The soap is continually stirred with a glass rod (weighed with the crucible) having a roughed and jagged end, a peculiarity which greatly facilitates the stirring and breaking up of the lumps of soap formed towards the end of the operation. The operation is usually complete in 20 to 30 minutes, and is known to be at an end when a piece of plate-glass placed over the crucible (the flame being removed) is no longer bedewed with moisture. Care is required to prevent burning of the soap, but the odour thus developed is so characteristic that the manipulation is easily con- trolled. Smith finds the results trustworthy to 0*25 per cent. The proportion of water in soap varies enormously. In the so-called " dry soaps, " and in some of the best kinds of curd soap, it does not exceed 16 to 20 per cent., while in inferior soaps made from cocoanut oil it sometimes reaches 70 to 80 per cent. B. SOLUTION IN PETROLEUM ETHER. Under ordinary circumstances, the matter dissolved from dry soap on treatment with petroleum ether consists merely of un- saponified glycerides or of free fatty acids. Insignificant propor- tions of unsaponifiable matter natural to fixed oils may also be present, and nitrobenzene and essential oils used for scenting the soap will also be dissolved. If Yorkshire grease has been used in manufacturing the soap, the residue may contain cholesterin. Cetyl alcohol from spermaceti and myricyl alcohol from beeswax and carnaiiba wax will also be present if these waxes have been employed. If added to the made soap, of course the unsaponified waxes will be dissolved out, instead of simply the solid alcohols resulting from their saponification. If the presence of waxes is suspected beforehand, or from the amount or appearance of the 1 The traces of alcohol present in transparent toilet soaps which have been purified by solution in spirit are volatilised with the water, and if 50 or ] 00 grammes of the sample be mixed with sand or powdered pumice, and gradually heated in a retort to 120, the alcohol may be deduced from the density of the distillate. 254 UNSAPONIFIED MATTERS IN SOAP. residue obtained on evaporating a portion of the solution, the residual soap should be further exhausted with boiling toluene, which dissolves the wax- alcohols better than petroleum ether. The residue from medicated soaps may also contain oleates of aluminium and heavy metals, free carbolic and cresylic acids, thymol, and hydrocarbons, such as vaselene and other neutral petroleum and tar products. When the nature or amount of the residue obtained on evaporat- ing a small aliquot part of the petroleum ether solution indicates the desirability of further examining it, the unevaporated portion should be treated in the manner directed in the following table : SYSTEMATIC SEPARATION OF UNSAPONIFIED MATTERS FROM SOAP. Agitate the solution in petroleum ether with dilute hydrochloric acid, and separate. a.Acid Solution. Examine for heavy metals (e.g., Pb, Hg, Cu, Zn, &c.) and alu- minium, which, if found, must have existed in the soap as oleates. Potas- sium and sodium oleates may also have been dissolved if the soap con- tained much hydro- carbon. If metals are found at this stage, the amount of fatty acids dis- solved by petroleum ether must be cor- rected to ascertain the fatty acids exist- ing in the soap in a free state. 6. Petroleum Solution. Wash free from mineral acid by repeatedly agitating with small quantities of water. Add some alcohol and titrate liquid with standard alkali and phenol-phthalei'n for estimation of fatty acids (page 76). Separate and agitate petroleum ether several times with small quantities of aqueous soda, separating as before. c. Petroleum Solu- tion. Evaporate at a low tempera- ture and observe odour, especially towards the end. Weigh residue and then determine un- saponified fat by Koettstorfer's pro- cess (page 40). In absence of waxes, the KHO required divided by 0'19 gives the weight of glycer- ides,which,deducted from whole residue, gives that of the hydrocarbons, wax- alcohols, &c. If de- sired, these may be isolated as on page 83, and further ex- amined. d. Alkaline Solution. Evapor- ate to small bulk, dilute with three measures of strong brine, and filter. e. Precipitate consists of sodi- um salts of fatty ncids existing in the soap either in the free state or as oleates of aluminium and heavy metals. /. Solution. Acidulate with dilute sulphuric acid, and separ- ate layer of phenols, or ti- trate portion of diluted solution with bromine, &c. (See also page 255 and "Creosote Oils.") Hydrocarbon oils, such as petroleum, vaselene, and coal-tar oils, are sometimes introduced into soap to a considerable extent. Although quite incapable of undergoing saponification, they may nevertheless exist in soap in notable proportion without their presence being suspected; for if not used in excessive amount, and especially if carnaiiba wax be also added, they remain in per- fect solution when the soap is dissolved in water or alcohol, and, on decomposing the solution with an acid, they pass wholly into the oily layer of fatty and resin acids. ASSAY OF CARBOLIC SOAP. 255 The presence of hydrocarbon oils in soap may sometimes be detected by the fluorescence exhibited by the ethereal solution of the fatty acids. If in considerable quantity, they may be partially separated by subjecting the dry soap to a gradually increasing heat, when the hydrocarbon oils will distil off, together with any other volatile matter which may be present. The most satisfactory means of detecting and determining hydrocarbon oils in soap is to extract them by agitating the aqueous solution of the sample with ether and caustic alkali as described below. Any unsaponijied fat will, however, be simul- taneously dissolved by the ether, and must either be separated by saponifying the ether-residue with alcoholic potash, and again agitating the solution of the resultant soap with ether, or the original soap may be evaporated with alcoholic potash, and the residue dissolved in water and treated with ether. The directions given in the foregoing table do not require further comment, except in the case of the method indicated for the determination of phenols. Although carbolic acid, cresylic acid, &c., are dissolved on treating the soap with petroleum ether, and can be separated from the admixed fatty acids by precipitating the alkaline solution with brine, the method is faulty in practice for the following reason : soaps, and especially common household and soft soaps, are liable to contain free caustic alkali which will react with the coal-tar acids added to form phenate, cresylate, &c., which bodies are not dissolved by petroleum ether, and hence the phenols which appear there are only that portion not taken up by the free alkali which happened to be present in the soap. The assay of carbolic soap for the percentage of phenols and other coal-tar products is most conveniently and accurately effected by the following process, which has been exten- sively employed in the author's laboratory : 5 grammes weight of the sample is dissolved in warm water with addition of from 20 to 30 c.c. of a 10 per cent, solution of caustic soda, according to the proportion of phenols believed to be present. The cooled solution is then agitated with ether, and the ethereal layer separated and evaporated at a low temperature. The weight of the residue gives the amount of hydrocarbons, fyc., in the quantity of the sample taken. The odour towards the end of the evapora- tion and that observed on heating the residue will give considerable information as to the nature of the admixture. Odours suggestive of gas-tar and burning gutta-percha are very common. The alkaline liquid separated from the ether is then treated in a capacious separator with excess of strong brine, which completely precipi- tates the fatty acids as sodium salts, while the phenols remain in 256 ASS AT OF CARBOLIC SOAP. solution. The liquid is well agitated to cause the soap to filter, and is then passed through a filter. 1 The precipitated soap is washed twice by agitating it with strong brine, the washings being filtered and added to the main solution, which is then diluted to 1 litre. 100 c.c. of this solution ( = 0'5 gramme of the sample of soap) is then placed in a globular separator, and acidulated with dilute sulphuric acid, when it should remain perfectly clear. 2 Standard bromine water is then added from a burette, the stopper of the separator inserted, and the contents shaken vigorously. More bromine water is then added, and the agitation and addition repeated alternately until the liquid acquires a faint but permanent yellow tint, showing that a slight excess of bromine has been used. If crystallised carbolic acid had been employed for making the soap the addition of the bromine water causes the precipitation of tribromophenol, C 6 H 3 Br 3 0, in snow-white crystalline flocks, which allow the faintest yellow tint due to excess of bromine to be observed with great facility. If cresylic acid be the chief phenol present the precipitate is milky and does not separate well from the liquid, but the end of the reaction can still be observed. The addition of a solution containing a known amount of crystallised phenol is a useful device in many cases, as the precipitate then curdles readily, and the yellow coloration can be easily seen. The bromine solution is made by mixing in a separator one measure of saturated bromine water with two measures of water. 3 This solu- tion is approximately 1 per cent., and should be run out from the tap of the separator into the Mohr's burette used for the titration. The burette should be closely covered, and the last few c.c. of the solution contained in it should never be employed for the titration, as it is apt to have become weak. The bromine water must be standardised immediately before or after use, by a solution of Calvert's No. 2 or No. 5 carbolic acid, according to the kind of acid the titration has indicated to have been present in the soap. This solution is made by dissolving 0'5 gramme of the coal-tar acid in 20 c.c. of a 10 per cent, of caustic soda, together with 1 In cases where the soap refuses to coagulate, an addition of a small quantity of tallow or palm oil soap, previously dissolved in water, will usually be successful. 2 A precipitation at this stage indicates the incomplete removal of the fatty acids. In such case, 200 c.c. of the alkaline solution should be treated with common salt in powder, the solution filtered through a dry filter, and 100 c.c. of the filtrate acidified as before. 3 The bromine solution and the mode of conducting the titration may be modified in any of the various manners proposed by various chemists, but the method of operating described in the text is quite accurate enough for the purpose in view, and has several practical advantages. ASSAY OF CARBOLIC SOAP. 257 5 grammes of a non- carbolic soap. The solution is then precipi- tated with brine in the same manner as the sample, the filtrate diluted to 1 litre, and 100 c.c. acidulated and titrated with the bromine used for the sample. The volume of bromine solution used is that required by 0'050 gramme of coal-tar acid of approxi- mately the same quality as that contained in the soap. The remaining portion of the liquid filtered from the precipitate of soap may be evaporated to a small bulk, acidulated with dilute sulphuric acid, and the separated phenols measured (see " Creosote Oils"), but the quantity is not sufficient to make the method satisfactory. It is generally better to employ the solution for the isolation of the bromo-derivatives. For this purpose it is acidu- lated with dilute sulphuric acid (without previous concentration), and bromine water added in slight excess. From 5 to 10 c.c. of carbon disulphide is then added, the liquid well agitated, and the carbon disulphide tapped off into a small beaker. The aqueous liquid is agitated with fresh quantities of carbon disulphide (of 5 c.c. each) till it no longer acquires a red or yellow colour. The carbon disulphide is then allowed to evaporate spontaneously, when a residue is obtained consisting of the brominated derivatives of the phenols present in the soap. If crystallised carbolic acid of fairly good quality was introduced into the soap, the bromo-deriva- tive is obtained in fine long needles having very little colour, and, if all heating was avoided during the evaporation of the carbon disulphide, the weight of the residue multiplied by 0'281 gives a fair approximation to the amount of carbolic acid ; but if a crude liquid article has been employed, consisting mainly of cresylic acid (e.g., Calvert's " No. 5 carbolic acid "), the bromo-derivative will be deep yellow, orange, or red, with little or no tendency to crystallise, and the weight will not afford even a rough indication of the amount of coal-tar acid present. 1 C. RESIDUE INSOLUBLE IN PETROLEUM ETHER. The portion of the sample not volatile at 100 and insoluble in petroleum ether really constitutes the soap proper. In analysing soap of known origin and general composition, it is often wholly unnecessary to go through the previous operations of drying and exhaustion with petroleum ether. In such cases it is evidently preferable to weigh out 10 grammes of the original soap and at once treat it with hot water. D. AQUEOUS SOLUTION OF THE PURIFIED SOAP. In most cases soap will dissolve almost completely in boiling 1 The following table shows some of the results obtained in the author's laboratory by the assay of representative samples of commercial carbolic soap. The descriptions of the soaps given by the manufacturers are strictly adhered VOL. II. K 258 ASSAY OF CARBOLIC SOAP. water, but if a large quantity of the solvent be employed hydro- lysis occurs to a serious extent, and if such a liquid be filtered a notable quantity of acid soap may be removed. Hence it is better when possible to separate any insoluble matter by decantation. When the proportion of insoluble matter is inconsiderable there is no occasion to separate it at all, as with proper management it will not interfere with the subsequent operations. An exception occurs in the case of calcium carbonate, which, if not removed, will neutral- ise acid and render the determination of total alkali excessive. In many cases the aqueous solution of the soap may be advan- tageously agitated with ether at this stage. Such treatment obviates the necessity of previously extracting the dried soap with petroleum ether, while it removes hydrocarbon oils, unsayonified oil, free fatty acids, &c., in a very satisfactory manner. The ethereal layer having been separated (see page 83), the aqueous liquid is again shaken with ether, which is separated as before. The ethereal solution may then be treated in exactly the same manner as is directed for the petroleum ether solution on page 254, while the aqueous liquid can be at once titrated with standard to, and in cases where two samples are described in the same words they were manufactured by different firms : Description of Soap. Phenols. Ether-residue. Per- centage. Nature. Per- centage. Odour on Heating. 1. Medical carbolic soap ; 20 / pure, 2. Medical carbolic soap ; 20 / pure 3. Carbolic toilet soap ; 10 %, 4. Carbolic toilet soap ; 10 / , 5. Transparent carbolic soap, 6. Transparent coal-tar soap, 7. Domestic carbolic soap, 8. Domestic carbolic soap, 9. No. 1 carbolic soap, 10. No. 2 carbolic soap, 11. Carbolic soap, 12. Carbolic soap, 30-5 17-0 3-6 3-4 3-2 1-5 4-8 6-4 5-4 3-5 1-1 0-5 9-9 8-2 0-16 none 0-75 Pure phenol Pure phenol Pure phenol Pure phenol Pure phenol Pure phenol Pure phenol Common carbolic Common carbolic Common carbolic Common carbolic Impure carbolic Common caibolic Common carbolic Common carbolic Impure carbolic 4-2 2-0 1-0 i'-o 4*'-6 4-6 Gutta-percha Cayenne Gutta percha Coal-tar oils Coal-tar oils 13. Carbolic soft soap; 10 %, 14. Carbolic soft soap ; 10 %, 15. Carbolic soft soap, 16. Disinfectant soap, 17. Sanitary soap, It will be observed that in No. 1 sample, described as containing 20 per cent, of crystallised carbolic acid, 30 '5 percent, was actually found, which result was confirmed by weighing the tribromo-phenol, which crystallised in beauti- ful colourless needles. In some cases the proportion of phenols found was notably less than the amount stated to be present, and this was especially the case with both No. 3 and No. 4, though these soaps were made by different firms. It must, however, be borne in mind that a loss of 2 or even of 3 per cent, of carbolic acid is liable to occur through evaporation. SEPARATION OF FATTY ACIDS. 259 acid, though for convenience of subsequent manipulation of the fatty acids it is desirable first to remove the dissolved ether by boiling the solution in a capacious flask. E. SEPARATION OF FATTY ACIDS. For decomposing the aqueous solution of the soap, normal sulphuric acid possesses some advantages, and should be used in moderation, an excess of 5 to 10 c.c. beyond that necessary to com- bine with the alkali present being sufficient. Alder Wright and Thompson prefer to substitute standard nitric acid, as it enables the sulphates to be determined by barium chloride in one portion of the nitrate, and the chlorides by silver nitrate in another. The method of manipulation for the separation of the oily layer of fatty acids from the aqueous liquid depends on circumstances. When the soap is chiefly a stearate or palmitate, as that made from tallow or palm oil, the liberated fatty acids are solid when cold, and in such cases there is no better plan than to effect their precipitation in a beaker or vessel, of such shape that the cake can be directly removed, wiped with blotting-paper, and weighed. Precipitation in a conical flask, as described on page 157, is advantageous in some cases. If the fatty acids are liquid at the ordinary temperature, or form a cake deficient in consistency, a known weight of dry, bleached beeswax or stearic acid may be added to the hot liquid. The fatty acids become amalgamated with the melted wax, and, on cooling, a firm coherent cake is formed, which may be at once wiped and weighed. The weight of wax added (which should be about the same as that of the soap employed) being deducted from that of the cake, the weight of the crude fatty acids is at once found. As a rule, the author prefers to affect the decomposition of the soap solution in a tapped separator, running off the aqueous liquid through a wet filter, and subsequently allowing the fatty acids also to run on to the filter, where they are washed with boiling water, and subsequently treated as described on page 38. This method of treatment is the best when it is desired to make a further* examination of the separated fatty acids. In analysing cocoanut and palmnut oil soaps, the fatty acids consist largely of lauric acid, and lower homologues, not wholly insoluble in hot water, are also present. In such cases the pre- cipitation of the fatty acids should be conducted in a tolerably concentrated liquid, which may be advantageously saturated with common salt. The washing of the separated acids should be restricted, and brine may be advantageously used, while the dry- ing should be effected with as little exposure to heat as possible. 260 SOLUBLE FATTY ACIDS. F. SOLUTION SEPARATED FROM THE FATTY ACIDS. The method described in the table for determining the total alkali of soap is, in most cases, highly satisfactory. The result is not affected by the omission to treat the soap with petroleum ether before dis- solving it in water, and ordinary insoluble matters do not interfere. If, however, an earthy carbonate be present, it will neutralise acid, and must be separated, or the estimation of alkali will be excessive. (See page 266.) Instead of at once adding an excess of standard acid, then titrating back, and thus ascertaining the volume required to neutralise the alkali of the soap, the standard sulphuric acid may be added gradually to the soap solution, until the neutral point, as indicated by methyl- orange, is reached. An excess of acid is then added, and the fatty acids separated as before. (See also page 266.) The volumetric method of determining the alkali does not dis- tinguish between potash and soda, and hence, if the nature of the alkali present be unknown, the determination is not absolute, but simply an expression of the alkali in terms of potash or soda. If further information be required, the examination must be made as described on page 267. The solution separated from the fatty acids, and neutralised with standard alkali, will, of course, contain sulphates of alkali metals. In addition, it may contain sodium chloride, soluble fatty acids, glycerin, sugar, dextrin, starch, gelatin, and other matters. For the detection and determination of these it is necessary to operate on separate aliquot portions of the solution. 1 a. Sodium chloride may be determined by titration with deci- normal silver nitrate, or deduced from the weight of the silver chloride precipitate. b. Soluble fatty acids rarely require determination in soap. If the precautions on page 259 are adopted in separating the fatty acids from cocoanut and palmnut oil soaps, only insignificant quantities of soluble fatty acids will remain in the aqueous liquid. If desired, these may be determined by distilling the acidulated solution, as described on page 37, but their amount may also be ascertained in the following simple manner. Titrate a certain volume of the solution with standard alkali, using phenol-phthalein as an indicator. Titrate another portion of equal measure with the same alkali, using methyl- orange to indicate the point of neutrality. The alkali consumed in the second case corresponds to the free mineral acid only, while the difference between this 1 If nitric acid has been used instead of sulphuric acid at the previous stage of the process, the sulphates of the soap may be determined by precipitating an aliquot part of the solution with barium chloride. GLYCERIN AND SUGAR IN SOAP. 261 and the first determination gives the volume of alkali required to neutralise the soluble acids present. 1 c.c. of normal alkali corresponds to 0'144 gramme of caprylic acid, CsH^C^. 1 c. Glycerin may exist in the solution of a decomposed soap in very variable amount. In the absence of sugar, it may be determined with considerable accuracy by the permanganate pro- cess described on page 289, but the presence of sugar renders the method wholly useless, and one of the following plans must be adopted. d. Sugar is rarely present except in transparent toilet soaps, but in these it sometimes exists to the extent of 20 to 30 per cent, of the entire weight, or in a proportion approaching that of the anhydrous soap present. Such soap is sometimes sold as " glycerin soap," though wholly destitute of glycerol. For the determination of glycerin in presence of sugar, the methods described on page 283 may be employed. The sugar is insoluble in the mixture of alcohol and chloroform, but may be dissolved out of the residue by rectified spirit. The solution obtained is evaporated, and the sugar weighed; or the residue may be redissolved in water, and the sugar determined by the polari- meter, or inverted and determined by Fehling's solution. Sugar may be determined by Fehling's solution, after inversion, without previously separating the glycerin, but the solution should be dilute and the boiling very limited in duration, or the glycerin will probably cause some reduction. In an aqueous liquid containing no other bodies than sugar and glycerin, such as may be approximately obtained by the means indi- cated 011 page 283, the amount of glycerin may be deduced from the density of the liquid. The sugar having been previously determined by Fehling's solution or other means, its effect on the density can be readily calculated ; and this being deducted from 1 A possible method of determining the total fatty acids in cocoanut and palmnut oil soaps is as f olio ws : Separate the fatty acids in the ordinary manner, but in as concentrated a solution as possible. Agitate the aqueous liquid with a little ether, separate, and extract any dissolved fatty acids from, the ether by agitating with dilute caustic soda solution. Employ the alkaline solution obtained to neutralise the main quantity of fatty acids, and add a few drops of phenol-phthalein, and then more caustic soda solution drop by drop till the pink colour just remains permanent. Then precipitate the hot liquid with a slight excess of magnesium sulphate, filter, wash with hot water, dry the precipitate at 100 C., and weigh. Ignite the precipitate and weigh the residual MgO. The difference is the weight of fatty anhydrides forming insoluble salts with magnesia. Evaporate the filtrate, dry the residue at 100 C. , and weigh. Ignite and weigh again. The difference is the weight of fatty anhydrides forming soluble salts with magnesia. 262 GLYCERIN IN SOAP. the observed density, gives that due to the glycerin present in the liquid. The composition of a weighed residue consisting of sugar, glycerin, and neutral salts can be determined as follows, provided that both sugar and glycerin are present in reasonable proportion. Dissolve the residue in 9 times its weight of water that is, use as many c.c. of water to effect solution as there are grammes of residue. Ascertain the density of this solution, and then evaporate it to dryness, ignite the residue gently, moisten with acetic acid to reconvert any carbonate into acetate, dry at 100, and weigh. Then dissolve the residue in such a quantity of water as will pro- duce a solution of the same measure as that evaporated. Ascer- tain the density of this solution, and subtract it from that of the solution of the original residue, when the difference will be that due to the glycerin and sugar present. As 10 per cent, of glycerin increases the density of water by 24'0, and 10 per cent, of sugar by 40*3, the proportion of each present in 100 parts of the residue may be found by the following equations, in which g is the per- centage of glycerin, s that of sugar, a that of neutralised ash, and d the difference between the density of the 10 per cent, solution of the original residue and that of the solution of the ash made up to the same volume : 40-3-'403-d 9= . -; and s=100-a g. C. KAlderWright (Jour. Soc. Arts, xxxiii. 1123) finds that a fairly accurate valuation of the glycerin present in the alcoholic extract from a decomposed soap may be obtained by rendering it strongly alkaline with solution of caustic soda, and then adding a dilute solution of copper sulphate, drop by drop, with continual agitation, until the blue precipitate of cupric hydroxide produced by the reagent no longer dissolves. The filtered blue solution is then compared colorimetrically with a standard solution of glycerin which has been treated side by side in the same way (see page 288). Where sugar is simultaneously present, the alcoholic extract must be heated for some time with dilute acid to invert the sugar, the fluid then rendered strongly alkaline, and cupric sulphate solution added drop by drop to the boiling liquid as long as reduc- tion occurs, when the solution is filtered and the colorimetric estimation of the glycerin proceeded with as before, the comparison being made with a solution containing known amounts of sugar and glycerin which has been treated in a precisely similar manner. Indifferent organic matters, such as starch, dextrin, gelatin, &c., may be detected by special tests ; but their recognition is more NATURE OF FATTY ACIDS FROM SOAP. 263 easy and certain in residue L, left on treating the purified soap with alcohol. G. EXAMINATION OF THE OILY LAYER OP FATTY ACIDS, &c. The separation of the liberated fatty acids, &c., from the acidu- lated aqueous solution of the decomposed soap has already been described. If wax or stearic acid has been employed for the purpose of obtaining a solid cake, the further treatment of the fatty acids is practically limited to drying them and determining their weight. In many cases, however, it is of interest or im- portance to make a further examination of the oily layer, which in that case should be treated as described on page 38. The oily layer is liable to contain a variety of. fatty acids from fixed oils, the acids of resin or colophony, coal-tar acids which existed in the original soap in combination with bases, and other bodies of acid character and limited solubility in water. If the treatment with petroleum ether has been omitted, the oily layer may also contain various hydrocarbons, waxes and wax-alcohols, unsaponified fat, &c. In such a case the proximate analysis is best made as indicated in the table on page 254. When only fatty and resin acids are to be determined, they may be separated by Gladding's method (page 78), or by the modified Barfoed- Gladding process described on page 225; but it must be remem- bered that any unsaponified oil is liable to contaminate the resin acid and be determined as such. Coal-tar acids may be determined by the bromine-titration process described on page 255. It is often important to ascertain the origin of the fatty acids present in a soap. This is sometimes a difficult problem, but in other cases may be satisfactorily solved by a study of their physical and chemical properties. Thus the melting and solidify- ing points of the fatty acids from various sources are given on pages 215 and 216, and L. Archbutt has communicated the following determinations of the densities of the acids from various oils. The observations were made at the boiling point of water by means of a Sprengel-tube (page 15), and the figures ex- press the densities of the fatty acids at the boiling point of watef, compared with water at 15 '5 C. ( = 60 F.) taken as 1000. Source of Fatty Acids. Specific Gravity. Source of Fatty Acids. Specific Gravity. Olive oil, genuine, 842-2 Niger seed oil, 854-6 840-4 Linseed oil, 858-3 w Gallipoli, j average, . \ 842-3 Train oil, Lard oil, 858-0 843-8 Colza oil, 844-8 Tallow, 836-4 Rape oil, 842-3 Palm oil, 8367 Cottonseed oil, 847-8 264 NATURE OF FATTY ACIDS FEOM SOAP. Much information can be gained by determining the combin- ing weight of the fatty acids as described on page 213. The figures yielded by the acids from various oils are given on pages 213, 215, and in other cases they may be calculated from the saponificatio n-e quivalents recorded on page 42. The combining weight of the insoluble acids is usually less than the saponification equivalent of the oil by about 13 to 14. This statement only applies to those oils yielding about 95 to 96 per cent, of insoluble fatty acids on saponification. Similarly, the iodine-absorptions of the insoluble fatty acids (page 214) are more or less characteristic of their origin, but are subject to the same limitations as are stated above to apply to the saponification-equivalents. In cases where the fatty acids of a soap are practically wholly insoluble in water, a titration in alcoholic solution with standard alkali and phenol-phthalein affords a simple and accurate means of ascertaining the proportion of alkali existing in combination with the fatty and resin acids, as it is evident that the amount of alkali required for neutralisation of the separated acids must be the same as that with which they had been previously in combination. The fact that the soaps produced by the saponification of cocoa- nut and palmnut oils are not readily precipitated by solution of common salt may, according to "W. Lant Carpenter, be employed for detecting the presence of these oils in soap. A sufficient quantity of the soap should be dissolved in hot water, and the fatty acids liberated by acidulating the solution, and separated without special washing or the use of ether. Carpenter then directs 10 grammes of the fatty acids to be treated with 39 to 40 c.c. of a normal solution of caustic soda, or a volume just sufficient to dissolve them completely. The whole is then boiled, and the weight of the liquid brought to 50 grammes by evapora- tion or cautious addition of water. A saturated solution of common salt (previously boiled with a few drops of sodium car- bonate and filtered from any precipitate) is then run in gradually from a burette, the liquid being constantly stirred and kept gently boiling. The addition is continued until the soap suddenly pre- cipitates, a point which is usually sharply marked. The soap from ordinary oils is precipitated when from 8 to 10 c.c. of the salt solu- tion has been added, but that from cocoanut oil requires an addition of more than 50 c.c. Mixtures of the fatty acids from cocoanut or palmnut oil with* those from other oils will of course require a volume of brine intermediate between these two limits. I. EXHAUSTION OP THE SOAP WITH ALCOHOL. If the original soap be tolerably dry, ordinary rectified spirit is FREE ALKALI IN SOAP. 265 usually sufficiently strong for the treatment at this stage ; but if the sample contain much water, absolute, or nearly absolute, alcohol should be used, or the solution will have an objectionable tendency to gelatinise during filtration and other inconveniences will arise. 1 The treatment with alcohol can be effected either in the Soxhlet- tube, or by boiling the soap with the solvent, and filtering and washing in the usual way. K. EXAMINATION OF THE ALCOHOLIC SOLUTION. a. The determination of the free caustic alkali existing in soap can be effected very simply and accurately by the method of C. Hope described in the table, the error rarely exceeding 0'25 per cent, of the total free alkali present. 2 Each 1 c.c. of normal acid neutralised, represents 0*0471 grammes of K 2 0, 0'0561 of KHO, 0-031 of Na 2 0, or 0'040 of NaHO. Should it be desired to ascertain whether the free alkali consist of potash or of soda, the method described on page 267 must be employed. The determination of the free caustic alkali in soap has been recently investigated by C. R. Alder Wright (Jour. Soc. Chem. Ind.jiv.Q3l), who finds Hope's process decidedly preferable to either of two other methods which have been somewhat extensively used. 3 It is possible to have a negative alkalinity shown at this stage. This result is due to the presence of free fatty acid or a diacid salt, but acidity of the spirit may produce the same effect. The volume of standard alkali required to be added before a pink 1 It is recommended by both Leeds and Wright that the portion of the soap to be treated with alcohol should be a part of that previously exhausted with petroleum ether, but, as pointed out by C. Hope, it is not possible to dry soap effectually without a notable conversion of the caustic alkali into carbonate. 2 The test may be applied qualitatively, by dropping an alcoholic solution of phenol-phthalein on to a freshly cut surface of the soap, when a red colora- tion will be produced, the intensity of which increases with the proportion of the alkali present. Caustic or carbonated alkali will also be indicated by the black or grey coloration produced by dropping mercurous nitrate on the freshly-cut surface. 3 One of these methods consists in determining the total alkali by titration, and deducting from it the amount of alkali found to be requisite for neutral- ising the isolated fatty and resin acids of the soap. The difference will clearly include the alkali present as carbonate and silicate, as well as that present in the caustic state. The other method examined by Wright had been found by C. Hope to be open to far larger errors. It consists in precipitating the aqueous solution of the, soap with excess of brine, and titrating the liquid filtered from the precipitated soap with standard acid. The results obtained by this process are vitiated to an intolerable extent by the fact that the addition of excess of water to a perfectly neutral soap decomposes it more or less into a basic and an acid soap. The extent of the change depends on the extent of the dilution and the nature of the fatty acids present (see footnote, page 245). 266 ALKALI IN SOAP. colour appears should be calculated to its equivalent of oleic acid, which is stated in the analysis as existing in the free state. Any difference between this amount and that found in the petroleum ether solution is due to a partial neutralisation of the free acid coexisting in the imperfectly mixed soap. 1 It is necessary to avoid confusion between the alkali existing in a soap in the form of caustic potash or soda, and that existing therein as a carbonate, silicate, or borate of alkali-metal. If the determina- tion be made in the alcoholic solution, as recommended, the caustic alkali alone will be present, the other compounds capable of neu- tralising alkali being insoluble in spirit. On the other hand, the standard acid required to neutralise the aqueous solution of the soap (page 260) includes that corresponding to any carbonate, silicate, and borate or aluminate of alkali-metal, and any soluble lime which may be present in the sample. The alcoholic solution of the soap rendered neutral to phenol- phthalein may be conveniently employed to determine the alkali existing in combination with the fatty and resin acids of the sample. To effect this, it is merely necessary to add a few drops of methyl- orange solution to the neutralised liquid, and then at once titrate with standard sulphuric or hydrochloric acid. 2 The point of neu- trality is sharply marked by the production of a pink colour, and the accuracy of the results are all that could be desired. 1 The following method of treating the alcoholic solution of a soap in such a manner as to allow of the determination of the leading constituents in a very rapid manner has been communicated to the writer by Mr C. Hope : 2 grammes of the soap is dissolved in hot absolute alcohol, a drop of phenol- phthalein solution added, and carbon dioxide passed till any pink coloration is destroyed. The liquid is then filtered, the residue, consisting of total impurities, washed with hot alcohol, weighed, and then titrated with decinormal acid and methyl-orange to find the alkali not existing as soap. The alcoholic solution is evaporated to dry ness at 100, and the residue of dry soap weighed when constant. It is then ignited gently, treated with water, and the solution titrated with decinormal acid and methyl-orange to find the alkali existing as soap. The difference between this and the total residue before ignition gives the fatty anhydrides, which, multiplied by 1*03, gives the fatty acids. The water is found with sufficient accuracy by subtracting the sum of the weights of the impurities and dry soap from 100 '00. 2 In order to prevent misunderstanding, the volumetric methods of ascer- taining the proportions of alkali existing in soap in various conditions may be recapitulated as follows : In alcoholic solution of soap. 1. Acid required to establish neutrality to phenol-phthalein corresponds to free caustic alkali, and is calculated to NaHO, KHO, Na a O, or K 2 0, according to circumstances. 2. Acid subsequently re- quired by same solution to produce neutrality to methyl-orange represents the alkali existing as soaps of fatty and resin acids. NATUEE OF ALKALI IN SOAP. 267 The volumetric determination of the alkali in soap gives no information as to its nature, that is, whether potash or soda, or a mixture of these. To ascertain this it is necessary to separate the sulphates or chlorides of the metals in a pure form. This is best effected by treating the alcoholic solution of the soap which has been used for the determination of alkali, and is neutral to methyl- orange, with strong baryta water, until the formation of a per- manent pink tint shows that the liquid is distinctly alkaline to phenol-phthalein. A saturated solution of barium chloride is then added, as long as further precipitation occurs, when the liquid is filtered from the barium sulphate and barium soap. The filtrate is evaporated to dryness, and the residue cautiously ignited at the lowest possible temperature. The residue is dissolved in water, the solution filtered, and treated with ammonia and ammonium carbonate, the precipitate filtered off, the filtrate again evaporated to dryness, and the residue gently ignited and weighed. In the mixed chlorides of alkali-metals thus obtained, the potassium and sodium may be indirectly deduced from the percentage of chlorine present, or the potassium may be directly determined as potassium chloroplatinate, in the manner described in all works on inorganic chemical analysis. The determination of the chlorine by dissolving the residue in water, and carefully titrating one-half of the solution with decinormal silver nitrate, using neutral potassium chromate as an indicator, will usually give sufficient information, and will, at any rate, suffice to show whether the residue consists essentially of potassium chloride or of sodium chloride, or, if a mixture of the two, the approximate proportions in which they are mixed. 1 In residue insoluble in alcohol. 3. Acid required to produce neutrality to methyl-orange corresponds to alkali existing as carbonate, silicate, and borate. In aqueous solution of soap. 4. Acid required to produce neutrality to methyl-orange corresponds to total alkali, whether existing as hydroxide, fatty acid soap, resin soap, carbonate, silicate, borate, aluminate, and soluble lime. This determination should therefore agree with the sum of 1, 2 and 3, or if any two of these have been determined the third will be the difference between their sum and the total alkali (4). 1 Potassium chloride contains 47 '53 per cent, of chlorine, and sodium chloride 60 '66 per cent., or 13 '13 per cent. more. Hence, every 1 percent, of sodium chloride in the mixture will raise the percentage of chlorine by 0'1313. Therefore the excess of chlorine above 47*53, divided by 0'1313, or multiplied by 7 '616, gives the percentage of sodium chloride present. Hence a residue showing 55 per cent, of chlorine will contain 64 '51 per cent, of sodium chloride, thus : 55-00 -47-53 268 ALKALI AS CAKBONATE, ETC. L. KESIDUE INSOLUBLE IN ALCOHOL. After drying and weighing the residue obtained at this stage, a minute quantity of it may be advantageously examined under the microscope. The characteristic structure of oatmeal, bran, sawdust, &c., will suffice for the detection of these bodies, and for the recognition of the kind of starch. By employing iodine solu- tion the starch corpuscles will be coloured blue, and thus rendered more distinct. If starch be found under the microscope it is sometimes desir- able to treat the residue with cold water, and examine the solution thus obtained separately from that subsequently obtained by the use of boiling water. Starch and gelatin will be contained in the latter only, but sodium silicate may be present in both solutions, a circumstance which is apt to occasion an undesirable complication. M. EXAMINATION OF THE AQUEOUS SOLUTION OF THE KESIDUE. Before dividing the aqueous solution and titrating one half with standard acid in the manner described in the table, it is sometimes desirable to make a direct determination of the carbon dioxide evolved on treatment with acid, so as to obtain a means of calculating the amount of carbonate of alkali-metal present. This is necessary when the soap contains borate or silicate in addition, but otherwise the carbonate can be deduced with accuracy from the titration of the solution with standard acid. To determine the carbonate directly, the concentrated solution should be treated with a moderate excess of standard acid in a carbonic acid apparatus, and the evolved carbon dioxide ascertained by the loss of weight, precipitation as barium carbonate, or measurement in a nitrometer. 44 parts of C0 2 correspond to 138*2 of K 2 C0 3 , or 106 of NagCOg. 1. After expelling the last of the carbon dioxide by warming the acidulated liquid, the solution should be divided into two or more equal parts, in one of which the excess of acid is determined by titrating back with standard sodium carbonate and methyl- orange, and hence the sum of the alkali existing in the four forms of carbonate, silicate, borate, and aluminate ascertained, while the other portion is examined for borate, silicate, and aluminate as in 2. The solution which has been employed for the determination of the total alkali of the residue may then be divided into two or more equal parts, which may be employed for determining sulphates by precipitation with barium chloride, starch by the methods de- scribed in vol. i. page 342 et seq., and to test for gelatin by means of tannin. If gelatin be found, it is best determined by treating another quantity of the soap with alcohol, and igniting the residue SILICATES AND BORAXES IN SOAP. 269 with soda-lime. 21 parts of ammonia formed correspond to 100 parts of gelatin. 2. The other half of the aqueous solution of the residue in- soluble in alcohol should be rendered distinctly acid with hydro- chloric acid, and exaporated at 100 in porcelain. A slip of tur- meric paper should be immersed in the liquid towards the end of the operation, and allowed to remain until the evaporation is complete. If a borate be present, the paper will become brownish- red in colour, and will be changed to green, blue, violet, or black on addition of caustic soda solution. The residue is treated with hydrochloric acid, water added, and the solution filtered. The residue of silica is washed, dried, ignited, and weighed. As the sodium silicate present in soap is not of constant composition, though usually approximately corresponding to the formula Na 2 0, 2Si0 2 , it is not possible to deduce the amount of alkali existing as silicate from the weight of the silica found; but, in the absence of borates, it may be ascertained by determining the carbon dioxide evolved on treating the aqueous solution of the resi- due insoluble in alcohol with dilute acid. This estimation will give the means of calculating the alkali existing as carbonate, and the remainder of the alkali of the residue must exist as silicate (or aluminate). The filtrate from the silica may be conveniently employed for determining sulphates by precipitation with barium chloride, or of aluminium by precipitation with ammonia and calcium in the filtrate by precipitation with ammonium oxalate. C. Hope states that free lime is not unfrequently present in soap, and may be be detected and determined at this stage. Its presence would tend to increase the " alkali " of the residue insoluble in alcohol. N. RESIDUE INSOLUBLE IN PETROLEUM ETHER, ALCOHOL, AND WATER. After drying the residue at 100 and noting its weight, it is desirable to examine it under a low microscopic power, with a view of recognising characteristic organic structures, &c., which can be seen much more distinctly after the removal of the soluble matters. Whether any further examination of the residue is requisite necessarily depends on its amount and nature, and the object of the analysis. Among the various constituents of such a residue the following list comprises those most likely to be present : 1. Insoluble Organic Matters; such as sawdust, bran, woody- fibre from oatmeal, &c. 2. Mineral Pigments and Colouring Matters; as red ochre, burnt umber, various other ferruginous materials, red lead, ver- milion, Scheele's green, chrome green, ultramarine, &c. 270 STATEMENT OF SOAP ANALYSES. 3. Mineral Matters used as Scourers; such as sand, powdered pumice, kieselguhr, &c. 4. Mineral Matters used as Adulterants or "Fillings" ; such as china clay, steatite, barium sulphate, chalk, whiting, &c. The systematic recognition and determination of these and other possible additions belong to inorganic analysis. It is sufficient here to indicate the following simple method of classification, with a view to facilitate further examination. Organic matters may be approximately determined by igniting an aliquot portion of the residue. The loss will include the volatile constituents of china clay, whiting, red ochre, &c., as well as any vermilion which may be present. By treatment with dilute hydrochloric acid, the original or ignited residue may be divided into soluble and insoluble con- stituents. The former include whiting, chalk, ultramarine, Scheele's green, oxide of iron, and the greater part of the ferru- ginous pigments ; while barium sulphate, steatite, sand, pumice, kieselguhr, china clay, chrome green, and vermilion are but little acted on. Interpretation of the Results of Analysis of Soaps. An ordinary " soap " may be regarded as the hydrated alkali- metal salt of a higher fatty acid, or a mixture of such salts. When a soap is decomposed by a dilute mineral acid, as occurs in the course of an analysis, free fatty acids are produced, together with a chloride or other salt of the alkali-metal. Thus in the case of sodium stearate, which is a typical soap, the reaction is as follows : NaC 18 H 35 2 + HC1 = NaCl + HC 18 H 35 2 . Calculating from this formula, it is found that, on decomposition with acid, sodium stearate yields 92*8 per cent, of stearic acid. Similarly, the alkali in the soap would be stated to be 10*13 per cent., so that the analysis would be Stearic acid, . . . . 9 2 '81 per cent, Soda (Na 2 0) . . . 10'13 102-94 This statement shows an excess of nearly three per cent., owing to the hydrolysis which takes place in decomposition. It is evi- dent that if the basic constituent of a soap be stated as anhydrous alkali, a correction must be made in the actual weight of fatty ANALYSES OF SOAPS. 271 acid found to bring it to the corresponding quantity of an- hydride. 1 568 parts of stearic acid, C 18 H 36 2 , correspond to 550 of stearic anhydride, C 36 H 70 8 , and the proportions of the respective anhydrides corresponding to palmitic and oleic acids are not very different from the above. Hence in soaps made from palm oil, olive oil, and tallow, the necessary correction of the observed weight of fatty acids to the corresponding quantity of fatty anhydrides may be made by multiplying by the factor '97, 100 parts of C 18 H 36 2 representing approximately 97 of C 36 H 70 3 . But in the case of cocoanut and castor-oil soaps, and many others made with mixed oils, this factor is far from accurate, and hence it is in all cases decidedly preferable to determine the mean combin- ing weight of the isolated fatty and resin acids, as described on page 213, and calculate the corresponding weight of fatty an- hydride therefrom. The mean combining weight of the anhydride is always 9 less than that of the corresponding acid. The usual figures for the fatty acids isolated from various fatty oils are given on pages 213 and 215. A considerable number of analyses of soaps have been published, but there are comparatively few on which much reliance can be placed. In the great majority of cases the observers appear to have been content to state the amount of fatty acids and alkali as deduced from the ash, the remainder being entered as "water, &c." Such meagre and inexact information as is supplied by such " determinations " is of very little value. The author is indebted to Mr Cornelius Hope for the very valuable analytical data contained in the following table. Samples 10 and 18 were prepared by the " cold process," and hence contained the glycerin produced by the 1 In a complete analysis of a soda soap, the constituents should be stated in the following manner : Per cent. Per cent. *Fatty anhydrides, .... tSoda existing as soap, Silica, ..... tSoda existing as silicate, tSodium carbonate, .... tSodium hydroxide (caustic soda, NaHO), . Sodium sulphate, .... Sodium chloride, .... Lime, ..... Oxide of iron, &c., . Water, . * = Fatty acids per cent. t = Total detergent alkali, as NajO, per cent. 272 COMPOSITION OF SOAPS OF COMMERCE. CO OO CO CO J^ rH p CO ^- O O O OS O O O OS (N(Mi-iCOO5ur5COOOOOO CO OS O5 O OS O5 O5 OS O Ci OS O OS rH COr-lO l>. CO t^ CO (M C<1 O OS o5 t-l CO CO rH r" _* B: .' -I c2 s ss JllHll o rH- ., fc-fll o ft^- - I s all IB I --a as^ C'^'S 1 Th 2 As with a CHOLESTEEIN. 311 CHOLESTERIN. Cholesterol. Cholesteryl Alcohol. C^O = C 26 H 43 .OH. Cholesterin is a substance which occurs very frequently, both as an animal and a vegetable product. It is present in the brain, yolk of eggs, perspiration, the liquid of ovarian tumours, &c. It is a product especially characteristic of the liver, biliary calculi being sometimes almost wholly composed of it. In shark-liver oil the author has found it in considerable quantity, and has also isolated it from codliver oil, butter fat, &c. It is also said to occur in various vegetable fixed oils, but in some of the observed cases it is not improbable that an allied substance was mistaken for choles- terin itself. Cholesterin exists in considerable proportion in the fatty matter of sheep's wool, in which it seems to occur in the form of ethereal salts of acids of the stearic and oleic series. Cholesterin is deposited from its solution in chloroform in anhy- drous needles, having a specific gravity of 1'067. It is tasteless and odourless. It melts at 144146 C., and if carefully heated may be sublimed unchanged at a higher temperature. When sub- jected to dry distillation it yields a carbonaceous residue and a neutral oil insoluble in potash, from which a second distillation with water separates a volatile oil having an agreeable odour of geranium. Cholesterin is quite insoluble in water, even when boiling. It is sparingly soluble in cold alcohol, but readily in the boiling liquid, and is easily dissolved by methyl alcohol, ether, chloroform, carbon disulphide, benzene, turpentine, and petroleum spirit. It is also soluble in fixed oils, purified bile, and solutions of soap. The alcoholic solution of cholesterin is neutral in reaction. It is laevorotatory, the specific rotation for the sodium ray being 3 6 '6, according to Dragendorff, or 31 '6 according to Linden- meyer. Cholesterin is deposited on gradually cooling its hot alcoholic solution in crystals containing 1 molecule of water. The crystals are silky needles, or, more frequently, nacreous laminae, of a highly characteristic appearance (see next page). Cholesterin is unacted on by dilute acids or concentrated alka- line solutions, but is decomposed when fused with caustic potash. If anhydrous cholesterin be dissolved in carbon disulphide, and a dilute solution of bromine in the same menstruum gradually added, a cholesterin dibromide, C 26 H 44 . Br 2 , is obtained. This body crystallises in small colourless needles, melts at 147, and is reconverted into cholesterin by the action of nascent hydrogen. 312 CHOLESTERYLIC ETHERS. By oxidation with chromic acid mixture, cholesterin is converted into a white amorphous acid, having the composition of oxycholic acid, C 26 H 40 6 , small quantities of acids of the acetic series being also produced. ETHERS OP CHOLESTERIN. In its chemical relationships, cholesterin behaves as a mon- atomic alcohol. On adding sodium to its solution in purified petroleum, sodium cholesterylate, CggH^.ONa, is formed with evolution of hydrogen. By the action of phosphorus penta- chloride, or by heating it with concentrated hydrochloric acid, cholesteryl chloride, C 26 H 43 C1, is obtained as a crystalline substance melting at 100. Cholesterin also reacts with organic acids to form a series of ethereal salts, of which the acetate and benzoate are the most interesting. Cholesteryl Acetate, C 26 H 43 .C 2 H 3 2 , is formed by the action of acetyl chloride on sodium cholesterylate, or of acetic anhydride on cholesterin (see pages 314 and 316). It crystallises in small, colourless needles, which melt at 92, and are nearly insoluble in cold and with difficulty in boiling alcohol, but are soluble in ether. Cholesteryl Benzoate, C 2 6H 43 .C 7 H 5 2 , is obtained by heating cholesterin with benzoic acid under pressure (page 315). It crys- tallises from ether in small glistening rectangular tables, melting at 150-151 C. On treating the various cholesteric ethers with alcoholic potash, they readily undergo saponification, and, after evaporating off the alcohol and treating the residue with water, the cholesterin can be extracted from the aqueous liquid by agitating it with ether. Detection of Cholesterin. When existing in a moderately pure state, cholesterin is easily recognised by its highly characteristic crystalline form. The sub- stance to be tested should be boiled with alcohol, the solu- tion filtered while hot, and allowed to cool slowly. Either immediately on cooling or after previous concentration, the cholesterin will be depo- sited in crystals, which, viewed under a moderate microscopic F ig- 13 - power, with a diaphragm hav- ing a small aperture, appear as thin, very transparent, rhombic REACTIONS OF CHOLESTERIN. 313 plates (fig. 13), the angles of which are extremely well defined, and constantly measure 79 30' and 100 30'. The formation of the characteristic acetate and benzoate, with determinations of the melting points of these ethers, will some- times afford valuable means of identifying cholesterin, as also of isolating it from other bodies (pages 314 and 315). Cholesterin gives a number of well-marked colour-reactions, of which the following are the chief : If a crystal of cholesterin be treated with a mixture of 5 volumes of concentrated sulphuric acid and 1 volume of water, and the whole gently heated and examined under the microscope, the crystal is seen to have become a fine carmine-red colour at the edges, and after an hour or two the red tint changes to violet. With a mixture of 3 measures of acid to 1 of water, a violet coloration results, and with more dilute acid the edges appear of a lilac colour. If cholesterin be triturated with a little concentrated sulphuric acid, and chloroform added, a blood-red solution is produced, which, on exposure to air, becomes successively violet, blue, green, and ultimately colourless. To obtain the last reaction, Salkowski proceeds in the following manner: About 10 milligrammes of cholesterin is dissolved in 2 c.c. of chloroform, and the solution shaken with an equal measure of strong sulphuric acid. The chloroform layer immediately becomes coloured, passing from blood-red to cherry-red and purple, which last tint it retains for several days. A cautious addition of fuming nitric acid to the mixture causes these changes to occur rapidly. Iodine acts in a very similar manner to nitric acid. The sulphuric acid which separates from the chloroform acquires a well-marked green fluorescence. If some of the chloroformic solution be poured into a capsule, the colour rapidly changes to blue, green, and yellow, the changes apparently being due to traces of moisture. On addition of water the solution becomes paler, then blue, and finally nearly colourless, while showing a fine green fluorescence. If cholesterin be heated cautiously with a drop of concentrated nitric acid, and the pale yellow product treated with ammonia before it has completely cooled, a fine yellowish-red tint is produced. If a mixture of 3 measures of concentrated hydrochloric acid and 1 of a solution of ferric chloride be evaporated with a little cholesterin, a reddish-violet coloration changing to blue is produced. Similar treatment with sulphuric acid and ferric chloride leaves a residue of a carmine colour, which gradually passes to violet, and becomes scarlet on treatment with ammonia. 314 ANALYSIS OF ETHER-RESIDUES. Isolation and Determination of Cholesterin. For the separation of cholesterin from animal and vegetable matters containing it, the dried substance should be exhausted with ether, as described on page 5, the ether distilled off, and the residue saponified by alcoholic potash (page 35), the alcohol evaporated, and the cholesterin extracted from the aqueous solu- tion of the resultant soap by agitation with ether, in the manner described on page 83. When oils or fatty matters are to be examined, they may be at once saponified by alcoholic potash. When no other unsaponifiable matter is present, the ether- residue will consist solely of cholesterin, which therefore may at once be weighed, but more frequently a further purification is necessary. To ensure the complete absence of saponifiable matters it is desirable to repeat the treatment with alcoholic potash, and re-extract the aqueous solution of the evaporated product with ether. The bodies most frequently occurring with cholesterin, in the " unsaponifiable matter" of which the ether-residue is composed, are isocholesterin (page 315), wax-alcohols from sperm oil, wool fat, &c., and various hydrocarbons. A partial separa- tion of these bodies may be made by boiling the ether-residue with about three times its measure of alcohol, and filtering the liquid while hot. Hydrocarbons, e.g., petroleum products, vaselene, &c., remain chiefly undissolved. On cooling the alcoholic filtrate, with or without previous concentration, the cholesterin will be mostly deposited in crystals, while the higher alcohols from sperm and bottlenose oils will remain in solution. A more perfect separation of the constituents of a complex ether-residue, such as that yielded by " recovered grease " or the crude oleic acid obtained by distillation of such products, may 'be made by the following method (Schulze, Jour. f. prakt. Chem.j cxv. 163): The ether-residue is boiled for an hour or two with an equal weight of acetic anhydride, in a flask furnished with an inverted condenser. The hydrocarbons, such as petroleum, vaselene, and paraffin, are not dissolved, but form an oily layer on the surface of the acetic anhydride, which latter should be separated while still hot from the hydrocarbons and boiled two or three times with water. This treatment removes the excess of acetic anhydride. The residue consists of acetates of the solid alcohols, and if boiled with sufficient alcohol will dissolve entirely, but on cooling the solution the cholesteryl acetate will crystallise out almost completely. The acetates of the alcohols from sperm oil and the waxes (as also any isocholesteryl acetate) remain in solu- tion, and are precipitated as an oily layer by pouring the liquid into hot water. ISOCHOLESTERIN. 315 Further information respecting the nature and probable source of the acetates can be obtained by ascertaining their melting points and saponification-equivalents (page 44), as also the melting points of the recovered alcohols resulting from their saponification. 1 Thus : Acetate. Alcohol. Melting Point. Sapon. -equivalent. Melting Point. Dodecatyl, C 12 H 25 , . Tetradecyl, C 14 H 29 , liquid 13 228 252 24 38 Cetyl, C 16 H 33 , 22 to 23 284 49'5 Ceryl, C 27 H 55 , Myricyl, C 30 H 61 , . Cholesteryl, C 26 H 4 ,, 92 438 480 414 82 85 to 86 144 to 146 Isocholesteryl, C^H^, below 100 414 137 to 138 ISOCholesterin. Isocholesterol. This body is isomeric with ordinary cholesterin, and occurs together with the latter in wool fat. To separate the isomeric alcohols, the mixture should be heated for 30 hours in a sealed tube to 200 C., with four times its weight of benzoic acid or benzoic anhydride. The product is then repeatedly boiled with rectified spirit, when the excess of benzoic acid dissolves and the cholesteryl and isocholesteryl benzoates remain. By crystallising them from ether, the former is obtained in shining rectangular plates and the latter as a light crystalline powder which can be separated by decantation and elutriation. Cholesteryl benzoate melts at 150-151, and the isomer at 190-191 C. By saponify- ing the ethers with alcoholic potash, and diluting the solution with water, the cholesterin and isocholesterin are precipitated. So prepared, isocholesterin resembles the ordinary body, but melts at 137-138, and solidifies on cooling to a brittle vitreous mass. A mixture of cholesterin with isocholesterin melts at a lower temperature than either body separately. Isocholesterin separates from its dilute solution in absolute alcohol in flocks, but a concentrated solution solidifies 011 cooling to a translucent jelly. From its ethereal solution it is deposited in needles. 1 The acetates of the wax-alcohols saponify very readily, and the decomposi- tion of cholesteryl acetate, which is more gradual, is completed when the solu- tion becomes clear. The alcohols will be separated on acidulating the solution of the soap, while the fatty acid (acetic) remains in solution, the behaviour being exactly the reverse of that characteristic of saponified fats. 316 WOOL FAT. When evaporated with nitric acid and afterwards treated with ammonia, isocholesterin gives the same reaction as cholesterin (page 313), but it gives no colour-reactions with sulphuric acid and chloroform, or with ferric chloride and a mineral acid. Hot acetic acid dissolves isocholesterin readily, forming an un- stable compound which loses its acetic acid on fusion. The true isocholesteryl acetate is obtained by digesting the alcohol with acetyl chloride till the evolution of hydrochloric acid ceases, and then heating the mixture to 100 in a sealed tube. On re- moving the excess of acetyl chloride by evaporation, isocholesteryl acetate is obtained as an amorphous substance, melting below 100 and readily soluble in alcohol (compare " Cholesteryl Acetate," page 312). Wool Fat. "Wool Grease. Suint. French Suint. German Wollf ett ; Wollsctiweissf ett. Sheep's wool contains a large amount of fatty matter of very peculiar character. It is excreted by all parts of the animal, but is found most abundantly about the breast and shoulders. The crude " yolk," as it is called, is largely soluble in water, and hence is removed by washing the wool, but the wool fat or suint proper remains, and can be extracted by carbon disulphide, petroleum spirit, alcohol, or other suitable solvent. Thus obtained, wool fat is a yellow or brownish grease, having a peculiar, disagreeable smell. It melts between 39" and 43 C., and has a density of about 973 at 15 C. It possesses the remark- able property of forming a very perfect emulsion with water, which when kept at the ordinary temperature exhibits no tendency to separate into its constituents. Chemically, wool fat has a very complex and peculiar composi- tion. It contains considerable proportions of cholesterin and isocholesterin, together with s t e a r i c and palmitic ethers of these alcohols. Ceryl cerotate and its homologues are also present, and probably cholesteryl cerotate. Besides these characteristic constituents, wool fat contains a certain proportion of ordinary glycerides, as also of glycerides of lower fatty acids, including valeric acid, and the potassium salts of various fatty acids. 1 The analysis of wool fat requires a departure from the usual 1 When the composition of wool fat, and of 'the recovered grease (degras) of which it often forms the greater part, is considered, it is not surprising that "practical" men have been disappointed in their efforts to saponify it com- pletely with the view of making it into soap. Three samples of recovered grease from wool-washing were found by C. Kawson to contain respectively 25 '5, 34*7, and 42 '5 per cent, of unsaponifiable matter. LANOLIN. 317 methods. The potassium and other mineral constituents can be determined in the ash obtained on igniting the suint. On saponi- fying the fat with alcoholic potash, evaporating, and agitating the aqueous solution of the resultant soap with ether, the solid alcohols (including cholesterin and its isomer) are dissolved, and may be recovered by evaporating the ether and examined as described on page 314. 1 On acidulating the aqueous solution of the soap, a precipitate of higher fatty acids will be obtained, while the lower fatty acids can be determined by distillation, &c., in the usual way (page 37). In the liquid separated from the layer of fatty acids, the glycerin can be determined by the permanganate process (page 291), and ten times the weight found may be regarded as the amount of glycerides. " LANOLIN " is the name given by B r a u n and L i e b r e i c h to a purified wool fat, recommended for compounding ointments and salves. 2 A sample examined by W. Chattaway in the author's laboratory, after being deprived of its water by heating, gave the following results : Specific gravity at 98'5, . . . 901'7 KHO required for saponification, . 9 '8 3 per cent. = Saponification-equivalent, . . 5 70 '9 Free fatty acids (in terms of stearic acid), 5*98 The original sample gave the following results on analysis : Water, 21 '30 per cent. Mineral matter, . . . . 0'35 Solid alcohols ( = ether-residue), . 46'50 ,, Volatile fatty acids (as C 5 H lp O 2 ), . 2'15 Non-volatile soluble fatty acids, , 0*80 Non-volatile insoluble fatty acids, . 3 8 '00 1 The separation of the ethereal layer from the aqueous solution of saponified wool fat and recovered grease is apt to be very troublesome, and intermediate stratum of a very persistent nature being formed. In such cases the follow- ing plan, suggested by C. R a w s o n, may .be advantageously adopted : The sample is saponified with alcoholic potash in the usual way, and the resultant solution is evaporated in a porcelain basin placed over a small flame. Towards the end of the operation some powdered sodium bicarbonate is stirred in to neutralise the excess of alkali, and some sand is also added. The residue is then dried at 100 and exhausted with ether in a Soxhlet-tube. The ethereal solution is then evaporated to dryness, the residue boiled with water, and the solution agitated with ether ; or the ethereal solution is at once agitated with water containing a little caustic soda to dissolve any soap it may contain, and then evaporated to dryness and the residue weighed. 2 According to the patent, lanolin is prepared by acidulating the clarified leys from wool-scouring, and kneading the resultant precipitate in a stream of 318 DISTILLED WOOL GREASE. The insoluble fatty acids had a combining weight of 319, and gradually assumed a yellow colour, which subsequently deepened to orange. The sum of the constituents is considerably above 100*00, an anomaly not wholly accounted for by the hydrolysis which accompanies saponification. It is not improbably due to the hydration of the solid alcohols. DISTILLED WOOL GREASE is a product obtained by distilling the grease with the aid of steam. It consists almost wholly of free fatty acids, mixed with cholesterin and other solid alcohols. It has been employed for adulterating tallow (see page 141). A sample used for this purpose, and the fatty acids obtained there- from, gave L. Meyer the following results : Grease. Fatty Acids. Melting point ; C., .... 421 41*8 Solidifying point; C., . . . 40*0 40*0 KHO required for saponification; per cent., 169*8 170*8 = Saponification-equivalent, . , 330*4 328'5 The fatty acids were at first white, but gradually turned yellow and orange, and acquired a smell exactly like that of wool fat. H ii b 1 states the iodine-absorption of distilled wool grease at 36*0. water as long as soluble matters are removed. The washed " lanolin " is then heated with water, when it is rendered anhydrous, and can be skimmed off and further purified, if requisite, by the usual methods. The water which the finished product contains is apparently introduced at a later stage, and varies considerably. HYDROCARBONS. THE numerous compounds of carbon with hydrogen which modern organic research has made known to chemists are classed together under the general name of hydrocarbons. Hydrocarbons are conveniently grouped according to the relative number of atoms of hydrogen and carbon present in the molecule. In this manner they may be arranged in various natural orders or series, of which the following table contains the most important. It will be seen that the generic formula of each series of hydro- carbons differs by H 2 from that of the preceding series. Thus, while the hydrocarbons CH 4 , C 2 H 6 , C 3 H g , &c., are said to be homologous, the hydrocarbons C 2 H 6 , C 2 H 4 , and C 2 H 2 form an isologous series. While the members of the paraffin series, C n H 2n+2 , are extremely indifferent to chemical agents, and refuse to form additive-compounds, the "olef ins" unite with Br 2 , the acetylenes with Br 4 , valylene with Br 6 , and d i p r o p a r- gyl with Br 8 . Thus the capacity of the hydrocarbons for combining with the haloid elements increases regularly with the removal of hydrogen. The hydrocarbons of series I., Ila., III., IVa., Va. constitute, therefore, a complete isologous series, the carbon-atoms probably forming " an open chain." In the case of the terpenes and the hydrocarbons of the benzene series the law of combining-capacity is completely altered, a fact which has led to the useful hypothesis of the " benzene chain." Thus, while the olefins, acetylene, valyl- ene, and dipropargyl combine with bromine in the dark readily, and in some cases even violently, benzene enters into direct com- bination with chlorine -or bromine with some difficulty, and only under the influence of light. Indeed, in many of their reactions the benzene hydrocarbons simulate the paraffins, though differing from that series in other important respects. Thus the series Va., VI., and VII. stand to each other in much the same relationship as subsists between the paraffins, olefins, and acetylenes, and a similar analogy may be traced between some of the members of the series IX., X., and XI. The assumption that the hydro- carbons in question are formed from the members of series I., II., and III. by the introduction, in place of hydrogen, of monad 320 HYDROCARBON SERIES. ll o "^ 1*3 d" If vi noS 111 S"* | O M SU < gsa P! b s. t3T3 O P li tillation us shale. m. dis in petrole largely in ble synthet sis. in Russian y Fo l r h e * 1 1 *j "S S3 II S3 h o Synthesis. Found larg tines and 11 ' "cs ? a I 1 ! yi tii 2 la IMS 11 *|1 |*4 I ->S 2^S l rt r | i- 3 ^l fl .& -3 S I! S.I el $TS S * .1 II 9fQ 5 IS o-.. 2S 1 s U& 'S.W * S ^r? Si -2 o" a -a o> < o 3 II II il HYDROCARBON SERIES. 321 i = 6 o it M . ^3 2 c 1 1 'a Pn-g g O "S 1 *-' <2 D g Tj 11 a X B U ^d 1 a |o Ij 1 | a |l | a 3 1 o g| s g I 1 j "3 | | g . ~ > r O a a 'ft * W O II 4 1 i 1 1 Cfl 1 1 3*8 "Si o 3 71 o o i a i .2 cS 1 a Hi go By dry distillation tial. Present lai By dry distillation By dry distillation i c By synthesis ; and By synthesis ; and 1 a I By synthesis ; and By synthesis. Exists in the minei lignite tar, and leum. Present in coal-tar i g a a B" oT a eS sS 3 a S E B "S 1 i 1 B ft ixT ... = 2 v. W oT w* u W 2 i 5a? 2^ & 1 0* | W c? J 5 s a-g, 5 * cs a fs" o af ;, |1t= 1 "a *: c? 1 "S 1 s 2 ; 5 IB S 1 1 2 r o 3 JJJ1 1 i & 1 t s ! S 1^ 1 1 1 d 1 d f .2 .2 1 1 M 1 1 d 1 1 e OJ "a o 1 ^ g I 1 I I j 2 T a i 1 ! I to Q 3a fl I & s s S * 4. i 4 SJ S g a s j r | | ] 1 I i i i d d a B d s B d 1 c B ^' u c5 c5 Q o ^ H K ^ ^ _; ^ ^ M J PJJ 11 M >< S M M. X! H 1 VOL. II. 322 BENZENOlD HYDROCARBONS. radicals derived from benzene or its homologues at once furnishes an explanation of their behaviour. Certain hydrocarbons, such as naphthalene, diphenyl, anthra- cene, phenanthrene, pyrene, chrysene, and dinaphthyl, exhibit properties which show that they have little resemblance to the paraffins, but are closely related to benzene, the carbon-atoms forming one or more closed chains. Benzene, naphthalene, anthra- cene, phenanthrene, and chrysene appear to form a series, the terms of which differ by C 4 BU. These hydrocarbons combine with fewer atoms of bromine or chlorine than benzene does, though the compounds are produced far more readily, and do not require light for their formation ; but the power of forming these additive-com- pounds becomes less with each member of the series, until chrysene forms no additive-compound with bromine. 1 The hydrocarbons of Series I. strongly resist the action of con- centrated sulphuric or nitric acid (see page 326), and do not under any circumstances form additive-compounds with them. The olefins and acetylenes, on the other hand, combine directly with sulphuric acid, and also often suffer polymerisation, but they do not yield characteristic products by the action of nitric acid. The terpenes appear to combine with sulphuric acid, but the resulting compounds are extremely unstable, and therefore the treatment usually ends in their being polymerised ; by nitric acid they are violently attacked, but do not yield characteristic products. Ben- zene and its homologues, as also most of the hydrocarbons of the remaining isologous series, yield substitution-products by treatment with strong sulphuric or nitric acid, one or more atoms of hydrogen being replaced by the corresponding number of S0 3 H or N0 2 groups ; the replaced hydrogen-atoms being always attached to carbon- atoms which form part of the closed chain. Any further consideration of the theoretical relationships of the hydrocarbons would be out of place here. On the other hand, a description of the generic properties and behaviour with reagents of the more important series is of interest from an analytical stand- point. The individual members of the paraffin, olefin, and acetylene 1 It is remarkable that all the hydrocarbons iu which the carbon-atoms are united BO as to form a closed chain containing two or more loops joined to- gether at two points (such as naphthalene, fluorene, acetnaphthene, anthra- cene, phenanthrene, pyrene, and chrysene) combine with picric acid, and that no such compound is produced by hydrocarbons such as diphenyl, in which there are two loops, but united only at one point. Similar compounds are also wanting in the case of the paraffins and other open-chain hydrocarbons. PARAFFINS. 323 series of hydrocarbons are not usually met with in commerce in an unmixed state, and hence their special properties have less im- portance than the general characters common to all the members of the series. On this account, it will be sufficient to describe the general properties of the paraffins, olefins, and acetylenes, while, on the other hand, the great practical importance of representative members of other series of hydrocarbons (e.g., oil of turpentine, benzene, naphthalene, and anthracene) renders it necessary to describe them and their allies in detail in separate sections. Paraffins. Methanes. Fatty Hydrides. C n H 2n+2 = C n H n2+1 .H. The hydrocarbons having a composition expressed by the above formula are known by the generic name of paraffins, and may be regarded as the hydrides of the m o n a t o m i c alcohol- radicals. All the members of the series above propane, C 3 H g , are capable of isomeric modification, the iso-varieties having somewhat different boiling points and densities from the normal paraffins ; they also yield different products on oxidation. 1 Above nonane, the normal and iso-varieties have not been satisfactorily differentiated. The percentage of carbon in pentane is 83'33 per cent., and the proportion rises very gradually with the number of carbon-atoms, candle-paraffin of the composition C 25 H 52 containing 85 '2 3 per cent, of carbon. The hydrocarbons of the paraffin series are especially character- istic of petroleum, in which product every known normal member of the series has been found, as well as some iso-paraffins. The minerals known as ozokerite, hatchettite, mineral tallow, mineral w a x, and c e r a s i n also consist essenti- ally of higher members of the paraffin series. 1 In (1) the normal paraffins, the carbon-atoms are connected together by simple linkage, no one atom being connected with more than two others ; in (2) the iso-paraffins, one atom of carbon is connected with three other carbon- atoms, the other carbon-atoms of the molecule being joined by simple linkage ; in (3) the meso -paraffins, there are two or more carbon-atoms which are con- nected with three other atoms of carbon ; and (4) in the neo-paraffins, one atom of carbon is connected with four other carbon-atoms. Thus, for example, the following paraffins all contain C 6 H 14 : Name. Formula. Boiling Point. 1. Normal. Amyl-methane, CH 3 .CH 2 .CH .CH 2 .CH 2 .CH 3 70 (CH 3 2. Iso. Dimethylpropyl-methane, CH \ CH 3 62 (C 3 H 7 3. Meso. Tetramethyl-ethane, pS 3 \ CH. CH \ ^ 58 4. Neo. Trimethylethyl-methane, C CH 3 CH 3 CH 3 C 2 H 5 45 C 324 PREPARATION OF PARAFFINS. Paraffins are also contained more or less largely in the gases and tars obtained by the distillation of Boghead and cannel coals, bituminous shale, lignite, peat, wood, rosin oil, menhaden oil soap, &c. Normal heptane has been obtained by Thorpe from the turpen- tine of Pinus sabiniata (Jour. Chem. Soc., xxxv. 296). By the solution of the variety of white cast-iron known as spiegeleisen in hydrochloric or sulphuric acid, Cloez (Compt. Eerid., Ixxxv. 1003, and Jour. Chem. Soc., xxxiv. 481) obtained various hydrocarbons of the ethylene series, absorbable by bromine and combining easily with hydrochloric acid ; and, besides these a number of paraffins. 1 In addition to the foregoing natural sources and modes of form- ation, paraffins are produced by the following laboratory reactions among many others : a. The action of water and metallic zinc on the iodides of the corresponding alcohol-radicals : 2C 2 H 5 I + Zn 2 -f- 2H 2 ZnH 2 (X + ZnI 2 + 2C 2 H 6 H. b. The action of zinc alone on the iodides of the corresponding alcohol-radicals. In this oase a portion of the product suffers de- composition with formation of lower paraffins and olefins : Butane. and: C 4 H 10 = C 2 H 4 + C 2 H 6 . Butane. Ethylene. Ethane. c. The electrolysis of the fatty acids : 2C 2 H 4 2 = (XH 6 2C0 2 . d. The action of lime or baryta on the salts of the fatty acids, 1 The paraffins were isolated by treatment with sulphuric acid, decantation, and drying first with caustic potash and then with metallic sodium, the purified oils being then fractionally distilled. The following are the boiling points and densities of the products obtained : Formula. Boiling Point. Sp. Gravity. C 10 H 22 155 to 160 '760 C U H,4 178 to 180 -769 C 12 H~ 6 195 to 198 782 C 13 H 28 215 to 220 793 C 14 H 30 234 to 238 '812 C 15 H 32 258 -830 C 16 H 34 276 to 280 '850 In connection with the formation of paraffins by the solution of cast-iron in acid, it is interesting to note the suggestion of II e n d el e j e f f that petroleum may have its origin in the action of steam or water on heated carbide pf iron in the interior of the earth. Silvestri has found 1 per cent, of petroleum in the lava of Etna. BOILING POINTS OF PARAFFINS. 325 at a high temperature : 2KC 2 H 3 9 + CH 4 . e. The action of excess of hydriodic acid on the corresponding alcohol, when an iodide of the alcohol-radical is first formed, and this reacts with the excess of hydriodic acid to form the paraffin and free iodine. By adding phosphorus at intervals to convert the liberated iodine into hydriodic acid, the higher fatty acids may be readily converted into the corresponding paraffins, which separate as an oily layer on adding water to the product of the reaction. The lower members of the paraffin series are permanent gases, and the intermediate ones liquids, their viscidity, density, and the temperature of ebullition l rising with each increase in the number of carbon-atoms, till the paraffin C. 20 H 42 and the still higher homo- logues are crystalline solids. The paraffins are saturated hydrocarbons incapable of entering into direct combination. This fact, and their resistance to the action of reagents, originated the name paraffin (parum affinis}^ which was at first employed to designate paraffin wax, but is now extended, generically, to all the members of the series. The paraffins are unaffected by chlorine or bromine in the dark, a character which distinguishes them from hydrocarbons of the ethylene and acetylene series. In sunlight the paraffins are acted on by chlorine or bromine with production of hydrochloric or hydrobromic acids and of chloro-orbromo-substitution- pro ducts. The paraffins are, however, more readily acted on 1 Formal butane, C 4 H 10 , boils at to 1 C., and normal pentane, C 5 H 12 , at 37 to 39 C., but the difference between the boiling points of each successive pair of the series decreases by about 4 C. , till it reaches the normal difference of 19 C. for each addition of CH 2 . According to Goldstein, the above expression is not strictly correct. As the difference between each successive pair of boiling points continually decreases, some other factor must be involved besides increase of molecular weight. Goldstein finds this in the decrease in the ratio of the number of hydrogen-atoms to the number of carbon-atoms. Thus, in CH 4 , C : H = 1 : 4 in C 2 H 6 , C : H = 1 : 3 in C 2 H 8 , C : H = 1 : 2f and in C 4 H 10 , C : H = 1 : 2 Hence the ratio is continually decreasing. Any paraffin boils at 19 + a higher than the hornologue immediately below OCA it: a>=r f -yr, the value of which is smaller as the value of the number of carbon-atoms (n) increases. E. J. Mills (Destructive Distillation, 3rd ed. p. 41) gives the following table of calculated melting points and boiling points of the normal paraffins. The figures to which asterisks are appended are substantially confirmed by the 326 BEHAVIOUK OF PARAFFINS WITH REAGENTS. by chlorine at their boiling points than in the cold. Cold heptane readily absorbs chlorine in diffused daylight, becoming yellow. The liquid suddenly becomes very hot, and evolves torrents of hydrochloric acid. From this point it remains colourless, absorbs the chlorine quietly, and evolves hydrochloric acid continuously. In presence of a little iodine the action continues in the dark, but secondary products are readily formed. The substitution-products obtained by the action of chlorine or bromine on the paraffins reproduce the original bodies under the influence of nascent hydrogen, and are converted into the cor- responding alcohols on treatment with alkalies. Iodine has no direct action on paraffins, but substitution-products containing iodine can be obtained by indirect means. Thus, tri-iodo-m ethane, or i o d o f o r m, CHC1 3 , is a product of the simultaneous action of iodine and an alkali on various organic bodies, such as alcohol, sugar, &c. Concentrated sulphuric acid has but little action on hydro- carbons of the paraffin series. The lower homologues of the paraffin series are unaffected by nitric acid, though interesting, nitro-substitution-compounds ("nitro- paraffins") may be obtained indirectly. The higher members of the series are but little affected by cold nitric acid, even when fuming and mixed with concentrated sulphuric acid, but paraffin results of experiment, but in other cases there are somewhat wide departures from the results of observation : 1 g : Melting Boiling I Melting Boiling o ,5 * Melting Boiling Hi Point ; Point ; * o Point ; Point ; 2 j; 5 Point ; Point ; c. 'C. c. C. I* 5 C. c. 4 5 +2-3* 39T X 16 17 + 17-2* 22-1* 256 265 28 29 (52-4 64-1 350 M53 I 70-7* 18 27-7* 277 30 67-0 360 7 98-7* 19 32-3* '2b5 31 68-2* 3fi3 8 124-0* 20 36-7* 2C6 32 71-1 369 9 5*2-3* 145-8 21 40-7* 02 33 71-8 371 10 -31-2* 166-8 22 44-3* 312 34 74-8 378 11 -25-S* 184-1* 23 47-9* 317 35 75-1* 380 12 -11-4* 201-8* 24 50-9* 326 ocodd 134-2 552-6 13 - 5-8* 215-8 25 54-1 330 oc even 140-6 555-7 14 + 4-4* 231-1 26 57-2 339 15 + 9-7* 242-5 27 59'4* 340 From this table it appears that the hydrocarbons containing an even number of carbon-atoms form a separate sub-series from those containing an uneven number of atoms, a case which is parallel to that of the acids of the stearic series (page 207). It also appears that no paraffin can boil at a temperature above 556 U , or melt at a higher temperature than 140 '6 C. ACTION OF HEAT OX PARAFFINS. 327 wax is attacked by hot nitric acid, even if dilute, 1 and it is also slowly acted on by chromic acid mixture, a small quantity of acetic acid being among the products. When the higher paraffins are heated in a sealed tube, or other- wise subjected to a high temperature, they suffer more or less complete decomposition, with formation of a lower paraffin and olefin ; thus : C 2o H 32 = C 5 H 12 + C 15 H 30 = C 7 H 16 + C 13 H 26 = &c. Hence, the actual product is a mixture of various paraffins and olefins. 2 Thorpe and Young (Jour. Cliem. Soc., xxvi. 260) found that when paraffin wax is repeatedly distilled it yields liquid paraffins, apparently normal, the whole series from C 5 H 10 to C 17 H 36 being present, while at the same time the corresponding olefins are produced. L. Prunier (Ann. Cliim. Phys., [5], xvii. 5; and Jour. Cliem. Soc. t xxxvi. 1025) finds that bromine absorbs nothing from the gas obtained during the first part of the process of distilling crude petroleum, but large quantities of unsaturated hydrocarbons are disengaged when the bottom of the retort is nearly or quite red hot. Among the bodies recognised were the ethylenes from C 2 H 4 to C 5 H 10 , and several members of the acetylene series, including crotonylene, C 4 H 6 . Among the solid hydrocarbons recognised were anthracene, pyrene, chrysene, fluoranthene, acetnaphthene, "petro- cene," and " carbopetrocene " (q.v.). METHANE, CH 4 , =CH 3 .H, is the first member of the paraffin series, and constitutes the greater part of the gas evolved by the decomposition of vegetable matter in presence of moisture, whence its name of "marsh gas." Fire-damp and the gas from petro- leum wells also consist chiefly of methane, though smaller quantities of ethane and other gases are also present. Methane also consti- tutes the greater portion of ordinary illuminating gas, and is a constant product of the destructive distillation of organic matter. ETHANE, C 2 H 6 = C 2 H 5 .H or CH 3 .CH 3 . This gas may be regarded 1 Schorlemmer obtained succiuic acid and other products by the action of boiling fuming nitric acid on octane from petroleum. 2 This reaction has an industrial application in the "cracking" of the heavier and denser of the petroleum oils. By this means, J. Merrill of Boston, Mass., found it possible to obtain "a continuous production of light distillates having a specific gravity of '818, effected from hydrocarbon oils of specific gravity '880, in an apparatus holding 1000 gallons, by properly regulating the heat applied ; the other products being only uncondensed gases and deposited carbon left in the apparatus at the end of the distillation." American Chemist, ii. 11, 444. 328 DETERMINATION OF PARAFFINS. either as ethyl hydride or di-m ethyl. It occurs in ad- mixture with methane in coal-gas, fire-damp, and the permanent gases which escape from petroleum wells. PROPANE, C 3 H 8 , and BUTANE, C 4 H 10 , are met with to a consider- able extent in petroleum gas. The latter paraffin forms the greater part of the petroleum product known as "cymogen e." PENTANE, or Amyl Hydride, C 5 H 12 = C 5 H lr H, has a density of 645 at C., and boils at 37 to 39 C. It occurs, together with isopentane, boiling at 30, in the most volatile portions of petroleum spirit, and in the products of the distillation of cannel coal and bituminous shale. HEXANE, C 6 H, 4 ; HEPTANE, C 7 H 16 ; OCTANE, C 8 H 18 ; and certain of their isomers constitute the greater part of the liquid known in commerce as petroleum naphtha or "benzoline." Normal hexane boils at 69 to 70, heptane at 97 to 98, and octane at 123 to 125 C., their respective isomers boiling in each case from 6 to 8 below the normal paraffins. Normal heptane has also been met with in a state of approxi- mate purity in the liquid obtained by distilling the terebinthinous exudation of the Pinus sabiniata (Jour. Chem. Soc., xxxv. 296). The higher paraffins require no separate description. 1 DETECTION AND DETERMINATION OF PARAFFINS. Paraffins in the vaporous or gaseous state can be separated from hydrocarbons of the ethylene and acetylene series by treatment in the dark with excess of bromine. The paraffins remain unaffected, while the admixtures are converted into liquid bromine compounds. The same principle is also applicable to liquid mixtures of paraffins and olefins. The unchanged paraffins may be separated from the olefin bromides by distillation in a vacuum. When paraffins are heated with bromine and water for some time in sunlight, they are converted into bromo-substitution-com- pounds, half the bromine which enters into reaction being after- wards found as hydrobromic acid. This reaction is peculiar to paraffins, and may, under favourable circumstances, be employed for their recognition and quantitative determination. Liquid paraffins may also be separated from hydrocarbons of other series by treating the mixture first with sulphuric acid, as long as the acid becomes coloured, and then with fuming nitric acid, avoiding rise of temperature. Other bodies are oxidised, or con- verted into nitro-compounds which remain dissolved by the acids or are much less volatile than the unaltered paraffins. After 1 A number of them have been prepared and described by F. K r a f f t (Ber., xv. 1687 ; Jour. Chem. Soc., xlii. 1271) and G. Lemoine (Bull. Soc. Chim., xli. 161; Jour. Chem. Soc., xlvi. 1106). CHARACTERS OF OLEFINS. 329 washing with water, drying over caustic potash, and rectification over sodium, a distillate of pure paraffins is obtained. A practical use of this principle is sometimes made in analysis. OlefinS. defines. Ethenes. C n H 2n . The hydrocarbons of the above general formula form a homolo- gous series of which ethylene or olefiant gas, C 2 H 4 , is the first term. All the members are known up to C 16 H 32 , and several still higher in the series have been isolated; but, as a rule, the properties of the olefins have been very imperfectly studied. The first three members of the series are gaseous at ordinary tem- peratures, and the remaining known members liquid, with the excep- tion of cerylene, C 2 yH 54 , and myricylene, C 30 H 60 , which are solid crystalline bodies. Olefins are not met with in the pure state in commerce, but occur largely in petroleum and the products of the dry distillation of coal and bituminous shales, especially the latter, and are also producible by the following definite reactions, among others of less importance : a. By the dehydration of alcohols, as in the formation of ethylene by heating ordinary alcohol with concentrated sul- phuric acid, phosphoric anhydride, or chloride of zinc : C 2 H 6 I). By the action of strong bases on the chlorides or iodides of monatomic alcohol-radicals, as when the vapour of ethyl chloride is passed over heated soda-lime or oxide of lead : * C 2 H 5 C1 + NaHO = KaCl + H 2 + C 2 H 4 . c. By the action of the copper-zinc couple on the olefin dichlor- ides or bromides dissolved in warm alcohol: C 5 H 10 Cl 2 -f-H2 = 2HC1 + C 5 H 10 . The olefins which are liquid at ordinary temperatures are more or less volatile oily bodies of less density than water, their specific gravities and boiling points increasing regularly with their mole- cular weights. The olefins have no strongly marked smell or taste, and are insoluble in water, but they are miscible in all pro- portions with ether, chloroform, carbon disulphide, benzene, and fixed and volatile oils. They are not readily affected by dilute acids or alkalis, but are far more susceptible of chemical change than the corresponding hydrocarbons of the paraffin series. By 1 The same decomposition is produced by heating the haloid ethers of moil- atomic alcohols with alcoholic potash. The secondary and tertiary compounds readily undergo decomposition in this way, and some of the latter even decom- pose spontaneously at temperatures considerably above their boiling points. The primary haloid ethers are attacked with greater difficulty, and always yield a mixed ether together with the olefin. 330 EE ACTIONS OF OLEFINS. the action of nascent hydrogen the olefins are converted into the corresponding paraffins. By treatment with hydrochloric, hydrobromic, or hydriodic acid in saturated aqueous solution, the olefins are converted with more or less facility into the corresponding haloid ethers of the alcohol- radicals. Thus b u t e n e , C 4 H 8 , when heated with hydriodic acid, forms iso-butyl iodide, C 4 H 9 I . The reaction occurs most readily with hydriodic acid, and least so with hydrochloric acid. With hypochlorous and hypobromous acids the olefins unite, forming monochlorinated alcohols (e.g., C 2 H 4 + HC10 = C 2 H 4 C1.0H.), which are converted into alcohols of the ethylic series by nascent hydrogen. By treatment with chlorine, bromine, or iodine, even in the dark, the olefins are immediately converted with evolution of heat into additive-compounds containing two atoms of the halogen. This important reaction is common to the whole series of olefins. The compounds produced are oily liquids of much higher boiling points than the original olefins. The reaction is of value for the detection and estimation of olefins in presence of other hydrocar- bons (see next page). By treating the bromides of the olefins with acetate of silver or potassium, olefin acetates are formed, which on distillation with an alkali yield the corresponding diatomic alcohols or glycols. By treatment of the lower olefins with sulphuric acid, sul- phates of monatomic alcohol-radicals are produced with more or less facility. Thus, by the action of sulphuric acid on ethylene, ethyl-sulphuric acid, C 2 H 5 .HS0 4 , is formed. These compounds, on distillation with water, yield monatomic alcohols. Sulphonic acids are also formed by treating the higher olefins with sulphuric acid, but the reaction is complicated by oxidation of the olefins, and by their tendency to become poly- merised. The formation of polymers occurs to a considerable extent when shale oil is treated with sulphuric acid of 1'70 specific gravity. Acid of 1 '845 density acts as a powerful oxidising agent, at the same time partially converting the oil into crystallisable sulphonates soluble in cold water, but decomposed on heating. By treatment with fuming nitric acid, olefins suffer oxidation with more or less facility, forming in some cases unstable nitro- compounds. The reaction with nitric acid may be employed for separating olefins from paraffins. When the olefins are oxidised by potassium bichromate and dilute sulphuric acid, they decompose in a similar way to the secondary or tertiary alcohols, and the division of the molecules, except in the case of ethylene, always takes place where the DETERMINATION OF OLEFINS. 331 double linkage occurs. A 4 per cent, cold aqueous solution of potassium permanganate reacts on the normal olefins thus : (CnH 2n+1 )CH : CH 2 + 4 = (C n H 2n+1 ),COOH + H.COOH. DETERMINATION OF OLEFINS. The only method practically available for the direct and accurate determination of olefins, when in admixture with hydrocarbons of other series, is based on the facility with which they unite with the halogens, especially bromine. For the estimation of the gaseous olefins, as existing in coal-gas, a known measure of the gas is introduced into a graduated Cooper's tube, care being taken that the water which is displaced has been previously saturated with gas of the same quality. Bromine is then dropped into the water which remains in the curved part of the tube, the tube closed with a stopper or the thumb, and the contents well agitated. On opening the tube under water, the diminution of the volume of the gas will indicate that olefins have been absorbed, and, on observing the water, oily globules of C 2 H 4 Br 2 will be perceived. These should be red or yellow in colour; if colourless, more bromine must be added and the agitation repeated. The tube being again opened under water, a small piece of caustic soda is added to absorb free bromine, and the tube agitated once more. The tube is then immersed in a cistern having glass sides, so that the volume of the residual gas can be read off when the water in the cistern is on the same level with that in the tube. The loss of volume, duly corrected if necessary for temperature, &c., gives the ethylene and other hydrocarbons absorbable by bromine. Highly satisfactory determinations of the olefins of coal-gas can be made by means of Hempel's gas-burette or Lunge's nitrometer, instead of employing a Cooper's tube. When the proportion of olefins is small a known measure of the gas can be caused to bubble through a solution of bromine in carbon disulphide. For the determination of the olefins in liquid hydrocarbons the bromine reaction is still available, but the method of operating must be modified. The following modification of the process of Mi 11s and Snodgrass described on page 47 has been exten- sively employed in the author's laboratory and found very useful for the examination of commercial products from shale and petro- leum. An approximately decinormal solution of bromine is made by dissolving 2 c.c. of bromine in 750 c.c. of recently-distilled carbon disulphide. This solution, which keeps well in the dark, is rendered perfectly anhydrous by the addition of some lumps of dry calcium chloride. An accurately weighed or measured quantity of the dry 332 DETEKMINATION OF OLEFINS. hydrocarbon, weighing between 0'3 and 1 '0 gramme, or a measure of a solution of the oil in carbon disulphide containing a known weight of the hydrocarbon, is then placed in a perfectly dry stoppered flask or separator, the solution diluted, if necessary, with carbon disulphide (kept over calcium chloride) to about 25 c.c., and then 25 c.c. of the carbon disulphide solution of bromine added. The flask is then closed, and the contents agitated. If the liquid is distinctly red, sufficient bromine has probably been added, but should the solution be nearly or quite decolorised, a further addition of a known measure of the bromine solution should be made without delay. The flask is then at once placed in the dark and kept there for a quarter of an hour, when an excess of an aqueous solution of potassium iodide is poured in, the contents agitated, the flask removed to a light place, and the solution titrated with a decinormal solution of sodium thiosulphate (hypo- sulphite, 24'8 grammes of crystallised lNra 2 S 2 3 per litre). The end of the reaction is indicated by the decolorisation of the carbon disulphide, and may be rendered still more sharp by adding a few drops of starch solution towards the end of the titration. Twenty-five c.c. of the carbon disulphide solution of bromine is then placed in a similar flask, potassium iodide solution added, and the titration with thiosulphate conducted as before. The difference between the volume of standard thiosulphate now required and that previously employed for the titration in presence of the hydrocarbon is the measure of thiosulphate corresponding to the bromine which has combined with the olefins and other unsaturated hydrocar- bons of the sample. One c.c. of decinormal thiosulphate (hyposul- phite), if of accurate strength, corresponds to '0080 gramme of bromine. 1 It is absolutely necessary not to expose the hydrocarbon to the action of bromine in presence of strong light. Even a very mode- rate diffused daylight is prejudicial, but gaslight has no sensible effect. 2 In the above description it is recommended that 15 minutes be allowed for the completion of the reaction. This time should be adhered to, for if much exceeded secondary re- 1 If the sodium thiosulphate be of good quality, and the crystals be crushed and pressed between blotting paper before the quantity required for the pre- paration of the standard solution is weighed out, the solution will be sufficiently accurate in strength for most purposes, without requiring to be "set" by means of iodine. The bromine solution keeps for a considerable time without change, and hence the verification of its strength is only occasionally necessary. 2 A sample of shale kerosene which showed a bromine-absorption of 50 '8 when the presence of light was avoided, gave an absorption of 66 '9 in strong diffused daylight. TITRATION OF OLEFINS BY BROMINE. 333 actions are liable to occur, which produce results in excess of the truth, more or less hydrobromic acid being usually produced, and the amount increasing with the time allowed for the reaction. 1 On the other hand, the reaction with bromine does not appear, in all cases, to become complete immediately. The foregoing process gives tolerably concordant results, and has been adopted by the writer in place of a method described by himself, in which the bromine was employed in aqueous solution. In its simplest form this process is conducted exactly in the man- ner of that just described, except that approximately decinormal aqueous bromine is used, 2 instead of a carbon disulphide solution of that element, and the iodide of potassium solution is added directly after the oil has been thoroughly shaken up with the bromine water. 3 This method gives fairly constant results, but they do not represent simply the bromine assimilated by the olefins, &c., of the sample, as oxidation also occurs to a very sen- sible extent. 1 The results yielded are therefore in excess of those 1 The occurrence of this secondary action is proved by the fact that, when the excess of bromine has been reduced by thiosulphate, the filtered solution is found to have a decidedly acid reaction, and the volume of standard alkali required for its neutralisation is a measure of the amount of hydrobromic acid pro- duced. If the addition of potassium iodide be delayed, and the solution be exposed to light, a further formation of hydrobromic acid will occur from the action of the bromine on the hydrocarbons of the paraffin series. 2 The first suggestion of the use of bromine for examining oils seems to have appeared in the second edition of Ronald's and Richardson's Chemical Technology, and an unsatisfactory process was described by Cailletet in 1857. It has been stated by Messrs Mills and Snodgrass (Jour. Soc. Chem. Ind., ii. 438) that the bromine-water method or moist process of examining oils was communicated by one of them to the writer on October 7, 1880. This allegation is incorrect, but why the statement should have been made is a mystery. Mr Jas. Snodgrass was quite unknown to the writer, even by name, and repeated applications to Dr E. J. Mills, couched in the mbst courteous terms, have failed to elicit a reply of any kind. That the allegation made by Messrs Mills and Snodgrass is wholly without foundation is evident from the fact that the writer gave a description of the results obtained by the process before the Pharmaceutical Conference in August 1880, while a description was published in outline in the Pharmaceutical Journal for September 25, 1880, or twelve days before the process is alleged to have been communicated to the writer. This fact has also been brought to the notice of Dr Mills and Mr Snodgrass, but it has not resulted either in the tender of an apology or any attempt to ex- plain or defend their disproved statement. 3 If the bromo-compounds formed are viscous and adhere strongly to the sides of the flask, so as to hinder the action of the bromine water, a few centi- metres of carbon disulphide may be added, when the oils will be dissolved, and can readily be brought in contact with the bromine water by agitating. 334 BROMINE- ABSORPTIONS. obtained by the carbon disulphide process, but they are fairly comparative, and, for works-assays of shale and petroleum pro- ducts the method will be found of service. Owing to the complex character of commercial hydrocarbon oils, a. determination of the amount of bromine combining with them does not give the means of calculating the percentage of olefins contained in them. If, however, a fraction of constant boiling point were prepared, and its vapour-density ascertained, its mean combining weight could thence be deduced, and then a determina- tion of its power of assimilating bromine would give a means of obtaining a close approximation to the proportion of olefins con- tained in the fraction. This suggested method assumes that the fraction consists essentially of paraffins and olefins. Any admix- ture of hydrocarbons of other series would further complicate the problem. On this account, it is preferable in practice to express the results of titrations as bromine- absorptions, that is, in grammes of bromine assimilated by 1 00 grammes of the oil. If a known measure of the sample has been employed, the number of grammes of bromine taken up by 100 c.c. must be divided by the density of the sample to ascertain the bromine assimilated by 100 grammes. It must be borne in mind that, besides olefins, many other sub- stances, both hydrocarbons and oxygenated bodies, assimilate bro- mine, and hence the " bromine-absorption " of a complex mixture is contributed to from several sources. Nor does the bromine assimilated by bodies other than olefins bear a constant relation to their molecular weight. Thus the hydrocarbons of the acetyl- ene series absorb either Br 2 or Br 4 , and the latter proportion is also assimilated by oil of turpentine and other terpenes. Oleic acid reacts with Br 2 , linoleic acid with Br 4 , and phenol with Br^ a bromo-substitution-product being formed in the last case. The results yielded by these bodies are described in the sections on oleic acid, turpentine oil, phenol, &c. ; and determinations of the bromine-absorptions of shale and petroleum products, rosin oil, and resins, will also be found duly recorded. Instead of ascertaining the bromine-absorption of a hydrocarbon by one of the methods described, it is possible to determine the iodine -absorption by HiibPs method (page 48), which gives results comparable with those obtained by bromine if the former be multiplied by the factor '6 3 = ( T 8 ^). In the experience of the writer, however, Hiibl's process is not well adapted for the examination of hydrocarbon oils, as the reaction cannot be relied on as complete under 24 hours, while that with bromine is perfect in as many minutes. ACETYLENES, 335 Hydrocarbons of the Acetylene Series. C n H 2 n-2. The e t h i n e s, or hydrocarbons of which ordinary acetylene is the type, are never met with in an unmixed state unless specially prepared. Acetylene itself is present in coal-gas, and some of its homologues exist in coal-tar, especially in that from cannel coal ; while several higher members of the series have been recognised in shale oil, and are probably present in certain kinds of petroleum. The greater number of hydrocarbons of the series have been ob- tained only by synthetical means, and possess interest merely from a theoretical standpoint. A general method for the preparation of the hydrocarbons of the acetylene series consists in heating the haloid ethers of the dyad alcohol-radicals with alcoholic potash, when the reaction takes place in two stages. Thus, ethylene dibromide first yields brom- ethylene, which reacts with more potash to produce acetyl- ene and potassium bromide : C 2 H 4 Br 2 + KHO = C 2 H 3 Br + KBr + H ; and, C 2 H 3 Br + KHO = C 2 H 2 + KBr + H 2 . The hydrocarbons of the general formula C 2 H 2n -2 may be arranged in three sub-groups, according to their molecular constitu- tion. Thus : GROUP A. The members of this class are the true homologues of acetylene, and contain carbon-atoms trebly linked, 'as in methyl- ethyl-acetylene, CH 3 .C ; C.C 2 H 5 . GROUP B. These hydrocarbons are derived from the haloid ethers of olefins in which treble linkage of the carbon-atoms cannot occur, as in d i m e t h y 1-i s o a 1 1 e 11 e, (CH 3 ) 2 : C : C : CH 2 . GROUP C. The members of this class contain two groups of doubly - linked carbon-atoms. D i a 1 1 y 1, CH 2 : CH.CH 2 .CH 2 .CH : CH 2 , and perhaps i s o p r e n e, C 5 H 8 , are the only members of the series at present known. All the hydrocarbons of the acetylene series have characteristic unpleasant odours. The higher members are readily polymerised by treatment with sulphuric acid of 1'70 specific gravity. They combine with Br 2 , to form bodies having the characters of d i b r o m- inated olefins, C n H 2n -2Br 2 , and with an additional propor- tion of bromine to form tetrabromides, C u H 2n _ 2 Br 4 (see page 337). The hydrocarbons of group A form compounds w r ith cuprous and argentic oxides, the production of which furnishes the most characteristic reactions for acetylene and its homologues. The hydrocarbons of groups B and C contain no hydrogen replaceable by metal's, and hence do not react with argentic and cuprous salts. 336 DETECTION OF ACETYLENES. To prepare the cuprous compounds, a solution of ammonio- cuprous oxide should be made by treating copper turnings in a separator with strong ammonia in presence of a limited quantity of air, until the blue liquid first formed has become colourless. The reagent is then run from the tap into a U-tube fitted with a tube bent twice at right angles and the open end of which dips under water, so as to prevent contact of air. On causing the vapour of the substance to be tested to bubble through the cuprous solu- tion, a yellow or red precipitate will be produced if any ethines be present. 1 If the precipitate be filtered from the liquid and treated with strong hydrochloric acid, the ethiiie will be liberated and may be recognised by its strong and peculiar odour, suggesting that pro- duced by a bunsen burner which has "lit down." This reaction furnishes the most convenient means of isolating acetylene and its true homologues in a condition of purity. On treating the cuprous compound with ammonia and metallic zinc, the corresponding olefin will be produced, and may be identified by the proportion of bromine with which it unites (see page 331). The silver-derivatives of the ethines are white precipitates which may be obtained in a similar manner, substituting a solution of argentic oxide in ammonia for the corresponding cuprous solution. A solution prepared by dissolving cuprous or argentic chloride in ammonia absorbs acetylene and its homologues equally well with the solutions of corresponding oxides, but some of the hydrocarbons are not precipitated by such a reagent, owing to their metallic derivatives being soluble in a solution of ammonia containing ammonium chloride. Separation of Various Hydrocarbons. The separation of individual hydrocarbons from complex mix- tures is often effected by processes of fractional distillation, fusion, &c. Basic substances may be removed by agitation with diluted sulphuric acid, and phenolo'id and acid bodies by treatment with caustic soda. The residual hydrocarbons, even when of perfectly constant boiling and melting point, often contain, however, several isomeric hydrocarbons of the same series, as well as members of several isologous series. 1 By causing a current of ordinary coal-gas to bubble through a cuprous solution in the manner indicated, a copious copper-red precipitate is readily produced, the probable formula of which is C 3 H 2 Cu 2 0, having apparently the constitution of cuproso-acetyl hydroxide, CH j C.Cu.Cu.OH. By passing a current of hydrogen through warm coal-tar naphtha, shale naphtha, or "first runnings," and bubbling the resultant gas through the cuprous reagent, a yellow precipitate, consisting chiefly of the cuprous compounds of crotonylene and valylene, is formed. SEPARATION OF HYDROCARBONS. 337 The analysis of mixtures of hydrocarbons of different series is, in many cases, exceedingly difficult, especially when their fusing and boiling points are approximately the same, in which case the methods of fractional fusion and distillation are not available. The following principles may in many cases be successfully applied to the analysis of complex mixtures of hydrocarbons which have been previously treated by fractional distillation, &c., so as to reduce them to approximately parallel products : l a. The hydrocarbons of the paraffin series are not acted on by bromine in the dark or diffused daylight ; whereas the olefins and the hydrocarbons of most other series form compounds having higher boiling points than the original bodies. 2 Hence the paraffins may be separated from the resultant bromo-compounds by frac- tional distillation, preferably conducted in vacuo, under reduced pressure, or in a current of steam. The olefins are remarkable for the facility with which they combine with bromine to form dibromides, C n H 2n Br 2 (page 331). From these bromides, as also from the bromides of other series, the original hydrocarbons may be regenerated by warming with alcohol and a copper-zinc couple. b. By treatment with bromine and water in sunlight, the paraffins are converted into monobromo-substitution-products, the aqueous liquid containing an amount of bromine in the form of hydrobromic acid equal to that which has entered into the hydro- carbon (C n H 2n+ 2 + Br 2 = C n H2n+iBr + HBr). By separating the aqueous liquid, removing free bromine by agitating with shale naphtha, and estimating the hydrobromic acid formed, a deter- mination can be made of the amount which has combined with the paraffins present. (See also footnote, page 333.) c. By treatment in the cold, or at any rate at 100 C., with con- centrated sulphuric acid of 1'845 specific gravity, all hydrocarbons except those of the paraffin series 2 are oxidised, polymerised, or converted into sulphonic acids. On subsequently adding water or solution of soda, separating the residual oil from the aqueous liquid, and distilling the former, the unchanged paraffins will pass over, while the polymerised olefins, terpenes, &c., will not distil 1 See a valuable'paper by Armstrong and Miller (Jour. Chem. Soc., xlix. 74) on the isolation and identification of the hydrocarbons contained in oil-gas, &c. 2 The para/enes, or hexahydrides of the hydrocarbons of the benzene series, and the naphthenes, which are identical or isomeric with these, simulate the paraffenes in their behaviour with bromine and cold concentrated nitric and sulphuric acids ; but by warming with fuming nitric acid or a mixture of strong nitric and sulphuric acids, they either yield nitro-compounds of benzene homologues or are oxidised without forming characteristic products. VOL. II. Y 338 SEPARATION OF HYDROCARBONS. till a much higher temperature is reached. From the aqueous liquid, acidulated if necessary, many of the hydrocarbons which form soluble sulphonic acids (e.g., benzene, toluene, &c.) may be recovered by distillation with steam. In many cases, it is better not to employ very concentrated sulphuric acid, but to treat the hydrocarbons repeatedly with a mixture of 2 measures of strong acid (sp. gr. 1'845) to 1 measure of water till no further action takes place, and then with a stronger acid (4 acid : 1 water). d. All hydrocarbons except those of the paraffin series are readily attacked by warm nitric acid of 1'45 specific gravity. In some cases nitro-compounds are formed, while in others products of oxidation result. The nitro-compounds distil at a higher temperature than the hydrocarbons from which they are derived. e. Acetylene and some other hydrocarbons of that and the next series form metallic derivatives on treatment with an ammoniacal solution of argentic or cuprous chloride, or of argentic nitrate. These metallic derivatives are solid bodies, insoluble in water, but decomposed by hydrochloric acid with liberation of the original acetylene or similar hydrocarbon. /. The hydrocarbons of the eighth and many of the subsequent series (page 321) form characteristic crystalline compounds with picric acid, which compounds may be decomposed by alkalies with formation of the original hydrocarbons. Various instances of the application of these and similar prin- ciples will be found in the succeeding pages. DESTRUCTIVE DISTILLATION. When non-volatile organic substances are subjected to heat in a close vessel they undergo destructive distillation. Many substances, which can be distilled without decomposition when cautiously heated, undergo destructive distillation when heated rapidly, or in admixture with inorganic matters such as sand or clay. The presence of oxygen, sulphur, nitrogen, &c., in the substance heated gives rise to products containing these elements. When the heat is applied gradually, the products first obtained usually contain the largest proportion of oxygen, the distillates becoming more highly hydrogenated and carbonated as the temperature rises. The nature of the decomposition which takes place on heating is indicated by the term cumulative resolution, first sug- gested by E. J. Mill s, who has done much for the theory of destructive distillation. A familiar instance of this action occurs in inorganic chemistry, when manganese dioxide is heated to full redness. Three units of the substance then decompose in partner- ship, thus : 3Mn0 2 = Mn 3 4 + 2 . Another example is furnished DESTRUCTIVE DISTILLATION. 339 by the action of heat on ordinary phosphate of sodium (hydrogen- disodium phosphate): 2Na 2 HP0 4 = Na 4 P 2 7 + H 2 . In a similar manner when glycerin (glycerol) is heated, polyglycerins are formed by the loss of the elements of water. A parallel mode of decomposition is common to all poly-alcohols. Thus, in the case of woody fibre (cellulose) we may have the following series of changes : C 6 H 10 5 -H 2 = C 6 H 8 4 C 6 H 8 4 -H 2 = C 6 H 6 3 C 6 H 6 3 -H 2 = C 6 H 4 2 C 6 H 4 2 -H 2 = C 6 H 2 C 6 H 2 -H 2 = C 6 . In practice, the bodies formed are not those indicated by the above formulae, but polymers of these. The above changes, complicated by other reactions, occur in the natural formation of coal from cellulose, as also in the artificial distillation of wood. By analogous reactions occurring simultaneously with the above, oxides and hydrides of carbon are formed, and are condensed in the receiver or pass away as permanent gases. The nature and proportions of these bodies obtained will be largely dependent on the character of the substance distilled, the temperature of the retort, and other conditions. When the heat is very moderate, the hydrocarbons produced are chiefly of the series known as the paraffins, having the general formula C n H 2n+ 2, of which marsh gas is the first member ; but as the higher members of this series readily split up into lower members and hydrocarbons of the formula C n H2n, the latter bodies are always simultaneously obtained. By further degradation, hydrocarbons allied to acetylene are formed, whilst benzene and its homologues contain a still smaller propor- tion of hydrogen. When the temperature is very high, hydrogen, acetylene, benzene, and naphthalene are the chief unoxygenated products. Thus, coal being distilled at a high temperature for the manufacture of coal- gas, the non-gaseous hydrocarbons consist chiefly of benzene and its homologues, and naphthalene. At a somewhat lower temperature the hydrogen and acetylene disappear, together with most of the naphthalene, while chrysene and a larger proportion of benzene are formed. At a dull red heat, such as is employed for the distillation of bituminous shale, the liquid products are wholly free from benzene and naphthalene, whilst little or no hydrogen or acetylene is pre- sent in the gases. On the other hand, the liquid products are rich 340 DESTRUCTIVE DISTILLATION. in paraffins and olefins, with some anthracene and chrysene ; and it is a remarkable fact that the oxygenised and nitrogenised products consist chiefly of substances of the formula C n H 2n -70H, and other phenolo'id bodies, and bases of the formula C n H 2n _ 5 ]Sr (pyridine bases), although the corresponding hydrides, C n H 2n . 7H, i.e., benzene and its homologues, are wholly or almost wholly absent. It has been suggested with much probability that the oxygen- ated bodies present in the low-temperature products split up at higher temperatures with formation of water and hydrocarbons. When mood is subjected to dry distillation, the volatile products are practically free from compounds of nitrogen and sulphur. Hence the watery portion of the distillate from wood has an acid reaction owing to the presence of acetic acid, and the same is true of the distillates from peat and lignite. In other respects the pro- ducts of the distillation of wood, as ordinarily conducted, are a mixture of low- and high-temperature products. As a rule, when the temperature of the distillation is low, a large yield of liquid products is obtained, together with a low yield of gas of high illuminating power. At a high temperature, a maximum production of gas of low illuminating power results, while the proportion of liquid products is small. The higher the temperature of the retort, the larger the percentage of solid carbon- aceous residue (coke or charcoal) left in it. 1 The three cases afforded in practice by the treatment of coal, shale, and wood may be regarded as typical of the changes attend- ing the destructive distillation of organic substances, though others, such as bone, rosin, and oil, yield special products of some prac- tical interest. But too much stress cannot be laid on the fact that the nature of the products depends not only on the nature of the substance treated, but also on the circumstances under which the operation is conducted with regard to temperature and other conditions. The following table indicates the general nature of the more prominent volatile organic products of the dry distillation of coal (for the manufacture of illuminating gas), bituminous shale, and wood, as the processes are carried on in practice. To facilitate comparison, the leading constituents of American petroleum are shown in juxtaposition with the products of the various artificial destructive distillations : 1 E. J. M i 1 1 s considers that the results of all kinds of destructive distil- lation are of a definite nature, that they cannot be susceptible of indefinite variations, and that the mean elementary composition of the products varies only according to the proportion of carbon remaining as coke, which again is dependent on the temperature (Jour. Soc. Chem. Ind., iv. 325). PRODUCTS OF DISTILLATION. 341 Organic Products. Coal. Bituminous Shale. Wood. Petroleum. Hydrogen, .... large traces large present Gaseous Hydrocarbons. Marsh gas and homo-> logues, . . . . f large large large present Olefins, .... large large considerable present Acetylene, . . present none ... ... Liquid and Solid Hydro- carbons. Liquid paraffins, . Solid paraffins, . . small traces large considerable absent present very large moderate Liquid oleflns, small very large ... considerable Liquid pseudolefins, Liquid acetylenes(ethines), present present ::: present Benzene and homo-> logues, . . . . ) large trace moderate present Naphthalene, . large none moderate none Anthracene, . moderate trace ... present Chrysene, . . . moderate considerable present present Oxygenated Bodies. Acetic acid, . present present large ,. . Methyl alcohol, none ... considerable .. Phenols, .... large considerable moderate Oxyphenols (Creasote), none (?) large large Nitrogenised Bodies. Ammonia, considerable considerable none Aniline bases, present none ... Pyridine bases . . considerable considerable ... Acridine, . . . Cavbazol, . present present ... ;;; Sulphur compounds, . present present none present It will be seen from this table that the products of the distilla- tion of each of the raw materials contain certain characteristic bodies. Thus, oxygenated products are found most largely in the products of the distillation of wood ; paraffins are especially characteristic of petroleum; olefins, and, to a lesser extent, paraffins, of the distillation of shale ; whilst coal tar, as Obtained in the manufacturing of illuminating gas, is remarkable for the comparatively large proportion of benzene and naphthalene contained in it. CRUDE OILY PRODUCTS OF DESTRUCTIVE DISTILLATION. TARS. By the destructive distillation of organic bodies and bituminous minerals three chief crude products are generally obtained, namely, gas, an aqueous liquid, and a viscid, dark-coloured o i 1 or tar. The methods of assaying the gaseous products do not come within the scope of this work. The aqueous product from wood, peat, and lignite is acid, and its examination has been described in Volume L The watery liquid from the distillation of coal, shale, 342 CHARACTERS OF TAE. and bones is strongly alkaline, the first of these constituting the " ammoniacal liquor " of the gas-works. TAR is a brown or black, viscid, oily liquid, of an unpleasant and more or less characteristic odour, according to its origin. The composition of tar varies widely according to the substance from which it was derived, and the temperature and other conditions of its distillation. .The tars produced by the distillation of wood, peat, and lignite are acid in reaction, while those from coal, bitu- minous shale, bones, &c., are alkaline. On repeatedly agitating the tar with water, the soluble matters to which! the acid or alka- line reaction was 'due may be more or less completely removed. Although consisting largely of hydrocarbons, all tars contain more or less oxygenised and nitrogenised bodies, and sometimes these constituents form a considerable proportion ; of , the whole tar. All tar being of extremely complex composition, and consisting in the main of volatile bodies, the most instructive method of examining it consists in subjecting it to careful distillation, collect- ing apart the distillates obtained at different temperatures, and subsequently fractionating these products with the view of effect- ing a. more perfect proximate analysis of the material. Towards the end of the distillation, the tar remaining in the retort becomes more and more viscous, and if allowed to cool sets to a solid, brittle, jet-black mass known as pitch. If the distillation be pushed further, actual coke is obtained. A considerable proportion of water is frequently contained in tar, and should be separated as far as possible before commencing the distillation. This is best effected by giving the tar an occa- sional gyratory motion, and removing each quantity of water by decantation as it separates. The presence of much water causes the tar to froth in a very inconvenient manner during distillation. For the method of conducting the distillation, no general instruc- tions can be given, as so much depends on the character of the tar, the nature of the information required, the scale on which the operation is to be conducted, and other conditions. But it may be regarded as a rule that the process should be conducted in the simplest suitable apparatus, and the distillate collected in a very moderate number of fractions, all refinements of fractional distilla- tion being reserved for the further treatment of the crude products first obtained. It must not be forgotten that in the first distilla- tions the more volatile constituents are retained in the retort by those of higher boiling point, and it is only after being separated tolerably perfectly from these that they distil at temperatures approximating to their true boiling points. The separation by fractional distillation having been carried out ANALYSIS OF TAE. 343 as far as appears desirable, a further proximate analysis of the dif- ferent fractions may be made into basic, acid, and indifferent bodies. Thus, by agitating one of the fractions with dilute sul- phuric acid, any basic bodies (e.g., ammonia, methylamine, pyridine , acridine, &c.) will be dissolved out, and can be recovered from the acid liquid by appropriate means. On agitating the residual oil with caustic soda, first in dilute solution and then somewhat con- centrated, any organic acids, phenols, or phenoloid bodies will be dissolved, and. can be recovered by separating the alkaline liquid and adding a slight excess of dilute sulphuric acid. The neutral bodies which have not undergone solution either by the treatment .with acid or with alkali consist essentially of hydrocarbons, the nature of which will depend largely on the particular fraction under treatment, the origin of the tar, and the temperature employed in the distillation which produced it. Particular processes are suit- able for special purposes. Thus benzene may be crystallised out by subjecting the more volatile fraction of coal-tar naphtha to a freezing mixture ; naphthalene readily separates from oils contain- ing it, especially after removal of the phenols by caustic soda ; while the presence of anthracene can be inferred from the forma- tion of anthraquinone by the oxidation of a certain high boiling fraction of the tar. The hydrocarbons of the different series may be successfully differentiated in many cases by their behaviour with reagents, especially with bromine, nitric acid, and strong sulphuric acid in the manner indicated on page 337. The following sections contain detailed descriptions of the char- acters and methods of examining tar from bituminous shale and coal. Tars of some other origins are also shortly described. Shale Tar. Crude Shale Oil. The crude oily liquid obtained in the South of Scotland by the destructive distillation of bituminous shale is an olive-green, strongly- smelling, viscous liquid. The specific gravity of the product from the old form of retorts is '890-' 8 9 4, and from the new kind '865 to *870. The composition of shale oil has not been so thoroughly in- vestigated as that of coal tar, but it has been proved to be of ex- tremely complex nature, the following being among the more characteristic and important substances hitherto recognised in it : Hydrocarbons of the Paraffin series, C n H 2n +2 ; most of the mem- bers from C 4 H 10 to C 30 H 62 being probably present. Hydrocarbons of the Olefin series, C n H-2 n ; most of the members from C 4 H g to C 20 H 40 being probably present. Hydrocarbons of the Pseudacetylene or Crolonylene series, C n H 2n _ 2 ; e.g., C 6 H 10 , C 7 H 12 , and C 8 H 14 . 344 COMPOSITION OF SHALE OIL. Hydrocarbons of the Benzene series, C n H2 n -6 ; present only in minute amount, and probably often wholly absent. Hydrocarbons of other series. Only doubtful traces of naphthalene and anthracene are contained in shale tar, but notable quantities of pyrene and chrysene occur. Nitrogenised bodies. Besides ammonia, shale tar contains a con- siderable proportion of pyrroline and bases of the pyridine series, CnH2n-sN (especially coridine, rubidine, and viridine), but neither aniline nor any of its homologues has been detected. Oxygenated bodies. Besides traces of acids of the acetic series, shale tar contains a notable proportion of phenols, C n H 2n _7.0H, and oxyphenols of a nature analogous to those present in wood tar. f3- and ^-thymols have also been found in the fraction distilling between 215 and 290, together with analogous bodies and a very small proportion of a-thymol. Sulphuretted bodies exist in shale tar, but their exact nature has not been ascertained. Shales containing much sulphur give little paraffin wax on distillation, and a low yield of other products. 1 The method of treating shale tar on a large scale varies in detail in each particular works, but it consists essentially in repeated fractional distillations, alternated by treatment of the several frac- tions with oil of vitriol and solution of caustic soda, and sometimes sodium carbonate, together with refrigeration of the high-boiling fractions to cause the crystallisation of solid paraffin. This is separated from the adhering oil by pressure, and the crude paraffin scale which results is purified by appropriate methods. 2 1 Mr R. Tervet has observed the deposition of crystals of sulphur from shale naphtha on cooling. 2 The following is an outline of the usual method of treating shale oil on an industrial scale, but it is subject to various modifications in detail, according to the practice of the works, the state of the market, and the exact nature of the oil under treatment (see page 348) : The crude oil is redistilled, either with or without the aid of steam, the first runnings being sometimes collected apart, but otherwise the whole distillate up to the point of coking is collected intact. "Water comes over during the whole process, and especially towards the end of the distillation, when the oxygenised bodies suffer further decomposition. The distillate is repeatedly agitated with small proportions of brown oil of vitriol, the lower layer of acid tar being drawn off after each treatment. The oily layer is next agitated with a strong solution of caustic soda, to remove phenoloid bodies, and is then redistilled. The receiver is changed when the distillate acquires a density of '828, and again when it reaches '877. The lighter fraction is treated with acid and alkali as before, and is again distilled, when it yields a low-boiling fraction or naphtha having a density of about 730, a burning oil which when again washed with acid and soda is of about *805 specific gravity and a fraction of '860 to '865 density which is added to ASSAY OF SHA ASSAY OF CRUDE SHALE OIL. The examination of crude shale oil is frequently required, in order to ascertain the proportions of naphtha, burning oil, lubricating oil, and " scale " or crude paraffin wax it is likely to yield on the large scale. The assay is best made by treating a known quantity of the oil as nearly as possible in the same manner as that employed in the manufacturing process. For the following description the author is indebted to Mr K,. Tervet : A. 1000 c.c. of the crude oil should be employed for the assay. The specific gravity should be previously observed, and the specific gravity and volume of the various products should also be noted at each stage of the process. 1 The oil is distilled to dryness with the aid of a current of steam, the distillate being collected in a capacious separator. The residue consists of coke. B. The distillate or " once-run oil " is warmed to about 40 C. by immersing the separator in warm water. Any water which separates is tapped off, and the oil is treated with 5 per cent, by measure of sulphuric acid (specific gravity 1*70) and agitated for not less than ten minutes. Any notable rise of temperature must be avoided by immersing the separator in water at about 35 C. After standing at this temperature for half an hour the " acid tar " will have separated, and may be run off through the tap. C. The acid-washed oil is next washed with 16 to 20 c.c. of soda (specific gravity 1*30), and again kept warm for half an hour to allow the " soda tar" to separate, when it is run off. D. The once-purified oil is then measured and its density ob- served. It is next transferred to a clean still, and again distilled to dryness, but the distillate is collected in two or more fractions, the next product. The fraction of the washed crude oil having a density between '828 and *877 is similarly distilled, when it yields "mineral colza," and other burning and lubricating oils. The oils of higher density than '877 thicken on cooling, from the formation of crystals of solid paraffin. This is separated by freezing and pressure, the oil which drains away being known as "green oil." The crude paraffin scale is melted and dissolved in the naphtha or most volatile fraction of the shale tar, allowed to crystallise out, and then subjected to hydraulic pressure. This process is repeated several times. The paraffin is then again melted, and steam forced through it to get rid of the last traces of naphtha. Finally, when perfectly free from moisture, it is melted and fdtered through animal charcoal. 1 All statements of quantities refer to measures, and the paraffin scale is similarly expressed, the volume being calculated from the weight. When not otherwise described the term "acid" signifies sulphuric acid of 1 '85 specific gravity, and the term "soda" a solution of caustic soda of the density stated in the appended parenthesis. The percentage proportions of acid and soda pre- scribed refer to 100 measures of the fraction to be treated, and not to 100 parts of the crude oil. 346 ASSAY OF SHALE OIL. according to circumstances. These are (E) naphtha, (F) light oil, (G) heavy oil, and (H) still-bottoms. For the first product, which is only yielded at this stage by certain crude oils, the receiver should be changed when the distillate has a density of '780. The process is then continued till a drop of the distillate, caught on a well-cooled spatula as it falls from the neck of the retort, shows signs of solidifying, when the receiver is changed. The product up to this point (F) is " crude light oil." Towards the end of the distillation for heavy oil (G), a thick viscid product of a brown or yellow colour is sometimes obtained, containing a large proportion of chrysene. When this product (H) makes its appearance, the receiver should be again changed, for if allowed to get into the heavy oil it would prevent the paraffin scale from crystallising properly, and would effectually prevent the oil from being separated from . the scale by pressure. The best plan is to add these objectionable still residues to the crude light oil (F), where it will be again treated with acid and alkali, which removes the chrysene, and the intermixed heavy oil will go back to the main quantity. I. The crude light oil (F) from the last distillation is agitated with 2 per cent, of strong sulphuric acid, the acid separated, 1 and the oil washed with excess of soda (sp. gr. 1'36), and the alkaline solution separated. J. The washed light oil, after observing its measure and density, is distilled to dryness, the distillate being collected in three frac- tions as before, namely: naphtha (up to density *750) (K), light oil (M), and heavy oil (N). The last product should be added to G. K. The naphtha may either be added to that obtained at a pre- vious stage (E), and the density and total measure of the product observed ; or, if not in large quantity, it may be added to the light oil (M). 0. The light oil, or crude burning oil (M), resulting from the redistillation of K, after being mixed with any fractions (U and perhaps V) obtained by redistilling the heavy oil, is washed with 2 per cent, of acid (specific gravity X'845), 1 and then agitated \vith excess of dilute soda (specific gravity 1'020), when its specific gravity and volume are recorded as the yield of finished burning oil (P). Q. The crude heavy oil (G), together with the heavy fraction (N) obtained by redistilling the light oil, should next be poured into a flat-bottomed capsule or plate, and allowed to cool very slowly, in 1 The mixture should not be warmed to promote the separation of the acid. The operation should be conducted at the ordinary temperature. ASSAY OF SHALE OIL. 347 . order that the crystals of paraffin may have time to develop. It is then further cooled to a temperature not exceeding 3 C., and preferably as low as 12 C. The cooled cake is next wrapped up in a closely woven linen cloth which has been previously saturated with lubricating oil. A gentle pressure is then applied until the bulk of the oil has drained out, after which the pressure should be increased till no more oil can be obtained. The paraffin scale (R) is then detached from the cloth and weighed. S. The "blue oil" separated by pressure from- the paraffin scale is washed first with 3 per cent, of strong acid, then with excess of soda (specific gravity 1'33), measured and distilled to dryness, the products being burning oil (U), intermediate oil (V), and un- finished lubricating oil (W). The first of these is added to M for further purification. V. The intermediate oil produced in the last process may either be added to the unfinished burning oil (0), or may, if thought requisite, be purified by washing in succession with 2 J per cent, of concentrated sulphuric acid and excess of weak soda (specific gravity TO 20), when the measure gives the yield of finished inter- mediate oil, having a density of about *850. W. The unfinished lubricating oil is similarly purified by treat- ment with 3 per cent, of sulphuric acid (specific gravity T845) and excess of soda (specific gravity 1*020), when the gravity and volume are noted as those of the finished lubricating oil. The tabular arrangement on next page shows the process in a con- cise form, together with the densities and volumes of the products actually obtained in the assay of a sample of crude shale oil. Thus the finished products from the sample examined were : Product. Per cent. ; by measure. Sp. Gravity. Melting Point. Naphtha, 4-0 765 Burning oil, 33-0 809 ... Intermediate oil, 1-6 850 Lubricating oil, Paraffin scale, . 21-0 10-6 887 49 : 5 Total, 70-2 If the naphtha obtained at the second stage (K) and the inter- mediate oil (V) were added to the burning oil, the volume of this would be increased to 3 6 "6 per cent, without sensible alteration of the density, while the yield of naphtha would be only 2 per cent, of 780 density. This is an unusually high density for naphtha, '730 being about the average. 348 TREATMENT OF SHALE OIL. II ^11 I 1 i 1 | c a J i 1 h 1 6 33 1 |* C p i 8- G -tf 9 -^2 ^ O 'o " | |p ^^ g C o 1 ~te i 1 i 1 s ^ K, 0? * x; c s " S JJ 9 ^ S s^ 1 id (sp. gr. a, .L hi g 3 =5 fc? S i 5 J 03 1 33 M & 'o be >> 1 . . O 4H 2 o ^ci ^ . O"OT r^ il to dryn o i SQ o ifi 9 CN op w cp "I". p i-i 8> IB ^ 05 do 1 C 1 ^ ej 00 Treat with e to dryness. ? g 00 nn 1 | II ^* i sf 1 = S'S - -S^i-'S- Pro's 5 5| rning oil (U), S eT t ' CO i 5 'o G. c = | Sf ^ fils -f.-l o_ ft fl Xv U, CO 3 S i i" i - * 1 'o i ^g |- g 2 "o f 5 ^3 Q i i ^ -1 o ~ c. 1 * BLAST-FURNACE TAR. 349 The method of assay described represents very closely the process of treating shale oil adopted in many works, though on reference to the footnote on page 344 differences in detail will be observed. Instead of employing the foregoing complicated and tedious method of assaying shale oil, it is sometimes sufficient to make a fractional distillation of the sample, collecting the distillate in portions of 5 per cent, each, and noting the density of each fraction and the solidifying point of the high-boiling fractions. The methods of examining the naphtha, burning oil, lubricating oil, and paraffin scale which form the proximate products of the distillation of crude shale oil are described in the section on ", Petroleum and Shale Oil Products." BLAST-FURNACE TAR. The tar produced by cooling waste-gases from blast furnaces consuming bituminous coal has been examined by Watson Smith (Jour. Soc. Cliem. Ind., ii. 495). The sample had a density of '954, and on distillation gave the following results : Percentage of Products. Specific Gravity. Distillate below 230 C., , ( Water 30 '6 by volume. ( Oil, 2'9 1-007 889 ,, from 230 to 300, 7-0 971 ,, from 300 till oils solidify, 13-0 994 , , solidifying on cool- ing, or soft paraffin scale, Coke, .... 167 21 '5 by weight. 987 Loss, ..... 5'5 ... On further fractionation, and treatment with sulphuric acid and caustic soda, the following products were obtained : Per cent, by volume. Tar bases, soluble in sulphuric acid, . . . 10 '6 Phenols and tar-acids, soluble in caustic soda, . . 5*6 Neutral oils, 18 '2 Soft paraffin scale, . . , . , . .5*7 (Yielding solid paraffin, *54 per cent.) The phenoloid bodies are further described under the head of " Blast Furnace Creosote." Of the neutral oils only an insignificant fraction distilled below 180 C. The density of successive fractions rose from '858 to '980. No naphthalene could be separated from an appropriate fraction by cooling it with ice and salt. The intermediate oils are 350' / WOOD TAR. not specially good as lubricants, nor are they suitable for burning in lamps. The fractions distilling between 250 and 350 C. possessed a deep green fluorescence, and closely resembled heavy lubricating oil from shale. On treating the soft paraffin scale with glacial acetic and chromic acids, solid paraffin wax was obtained, and a large proportion of a pitchy deposit was formed, but no anthraquinone, produced by the oxidation of anthracene, could be detected. TAR FROM JAMESON COKE-OVENS. In the recovery of secondary products from coking coal accord- ing to the Jameson process, a tar is obtained which in its leading features resembles the blast-furnace tar and shale oil just described. The neutral oils have very little viscosity, and are unfit for burn- ing in lamps. Toluene and xylene are present in trifling propor- tion. No naphthalene or anthracene appears to be present, but a notable quantity of paraffin wax is obtainable. The phenoloid bodies exist in considerable proportion. They contain little or no carbolic acid, and the higher fractions give unstable colouring matters on exposing their alkaline solutions to the air ("Watson Smith, Jour. Soc. Chem. Ind., ii. 499). Wood Tar. The products of the destructive distillation of wood are very numerous, and vary much with the nature of the wood arid the temperature at which the process is conducted. But under all circumstances the volatile products are characterised by the large proportion of oxygenised products contained in them, 1 and by the absence of sulphur compounds and sensible quantities of ammonia. Among the gaseous products the most abundant are carbon dioxide, carbon monoxide, and hydrogen, some methane being also present. The aqueous portion of the liquid distillate, or crude pyroligneous acid, usually forms from 2 8 to 50 per cent, of the weight of wood distilled, and contains acetic acid, methyl alcohol, 'allyl alcohol, and acetone as its chief con- stituents, though many other bodies are present in smaller propor- tion (see volume i. pages 44 and 384). The "tar," or oily portion of the crude distillate from wood, averages from 7 to 10 per cent., and is a complex mixture of 1 The products obtained at the lowest temperature are those richest in oxygen, such as water and acetic and carbonic acids. Next are formed com- pounds containing less oxygen, such as methyl alcohol, acetone, and creosol ; while, at a still more elevated temperature various hydrocarbons are pro- duced, such as toluene, xylene, and the different paraffins, while, as the tem- perature approaches redness free hydrogen is the leading product. STOCKHOLM TAR. 351 various liquids holding solid matters in solution. On distillation between 70 and 250 C., Russian wood tar yields oils of a density ranging from "841 to '877, and leaves a residue of pitch, which contains solid paraffin ; various resinous matters ; and pyrene, chrysene, and other hydrocarbons of high boiling point. On redistillation, the tar-oils yield the following products : Below 100 C.; fatty acids, syl vane (C 5 H 6 0), methyl alcohol, benzene, &C. 1 Between 100 and 150; benzene homologues, &c. Between 150 and 200; benzene homologues, phenols, and oxyphenols. Between 200 and 250 ; phenols and oxyphenols, lignoceric acid (C 24 H 48 2 ), naphthalene, retene, paraffin wax, &c. The lower paraffins appear to be absent from the tar, but the permanent gases produced by the distillation of the wood contain methane. 2 STOCKHOLM TAR, so largely used in shipbuilding, is the product of a rude distillation of the resinous wood of the pine. 3 The tar thus obtained contains a considerable admixture of resin and turpentine, and has applications for which the tar obtained in the manufacture of pyroligneous acid cannot be substituted. It has a density of 1 '04, and on standing usually deposits a granular crystalline matter consisting mainly of pyrocatechol. "Water agitated with the tar acquires a light brown colour and sharp, bitterish, taste. The aqueous liquid is coloured transiently green by ferric chloride, owing to the presence of pyrocatechol, and lime water acquires a permanent brownish-red colour. When Stock- 1 The light oils of wood tar have been examined by G. Thenius (Jour. Chem. Soc., xxxiv. 664). If the oils of wood tar are exposed to a high temperature they are partially converted into heavy gaseous hydrocarbons. " Wood gas " is manufactured in this manner, and contains, when purified Hydrogen, 487 to 187 Methane, 35 '3 to 9 '4 Ethylene and its homologues, . . . 10 '6 to 6 '5 Carbonic oxide, 61 '8 to 22 '3 2 80 per cent, of the more volatile portion of Swedish wood tar consists of a mixture of two terpenes: a ustralene, boiling at 155 ; and sylvestrene, boiling at about 175. The most important product from wood tar is the mix- ture of phenol oid bodies known as creosote, the method of examining and nature of which are described in the sequel. 3 The wood is arranged in large holes having the shape of inverted cones. The wood is ignited on the top and partially covered with earth so as to allow of a slow combustion without flame. The tarry products collect in a cavity or ditch at the base of the pile. 352 TREATMENT OF COAL TAR. holm tar is heated, water, acetic acid, and impure turpentine oil are volatilised and ordinary pitch remains. A distinction between wood-tar pitch and coal-tar pitch will be found on page 377. Coal Tar, Coal tar, as obtained as a bye-product in the manufacture of illuminating gas, is a black viscid fluid of characteristic and dis- agreeable odour. The specific gravity ranges from I'lO to 1'20, being usually between 1'12 and 1*15. Coal tar is a product of extremely complex composition, and contains many bodies the exact nature of which is still unknown, though it has been the subject of numerous researches. As coal tar is always more or less mixed with ammoniacal liquor, the constituents of the latter liquid are present in addition to those of the tar proper, and the constituents of the illuminating gas itself are also present in a state of solution. The first treatment of coal tar on a large scale consists in dis- tilling it in iron retorts, and collecting the distillate in three or four fractions. The temperatures at which the receivers are charged vary considerably with the practice of different works, and hence the products are far from being strictly parallel. The follow- ing table represents three methods of fractionation which are largely employed : A. B. C. Product. Distilling Point ; C. Product. Distilling Point ; C. Product. Distilling Point ; C. Crude naphtha, or light oils, . Heavy oils, dead oils, or creo- sote oils, to 170 170 to 270 First runnings, or first light oils, Second light oils, Carbolic oils, . Creosote oils, . to 110 110 to 210 210 to 240 240 to 270 Light naphtha, Light oil, . Carbolic oils, . Creosote oils, . to 110 110 to 170 170 to 225 225 to 270 Anthracene oils, Pitch, above 270 Anthracene oils, Pitch, r above 270 Anthracene oils, Pitch, 270 to 360 The arrangement on the following page, taken with certain alterations from a table published by E. J. Mills, shows the general method of treating coal tar in a work employing method C. of original fractionation. During the first part of the process permanent gases are given off", while the fluid distillate consists of ammoniacal water and the most volatile constituents of the tar proper, together with sensible traces of less volatile bodies, carried over mechanically or volatilised TREATMENT OF COAL TAR. 353 s'H 60 4. 1 ml .9 '3 is bo- 'I-' I 5 "3 i fi a * .1 S a g I 1 K* |i3 VOL. II. 354 TABULAR VIEW OF Tl Paraffin Series, CnH2n+2. Olefin Series, Crotonylene Series, C n H2n-2. Benzene Series, CnH2n-2. Naphthalene am its Allies. C 4 H 10 , Butane, C 4 H 6 , Crotony- C 5 H 12 , Pent- C 5 H 10 , Amyl- lene, 23 C 5 H 8 , Terene ane, 38 ene, 39 1 COHJ4, Hexane, 69 C 6 H 12 , Hexyl- ene, 67 C 6 Hio, Hexoyl- ene, 80 C 6 H 6 , Benzene, 81 g rt b C 7 H 16 , Hept- C 7 H H , Heptyl- C 7 H 8 , Toluene, 111 .G ""J ai.e, 97 ene, 96 IF "o-S C 8 H 18 , Octane, 124 (C 9 H 20 , Non- ane, 146) 0ttH (p. 136 Xylenes, 1 ^ JJ| SMesitylene, 3-3 II cane, 167 163 Pseudocu- mene, 166 IP 3 1 C 10 H 14 , Durene, 190 C 10 H 12 , Naphtha ene tetra-hydrid 190 OT- C 10 H 10 , Naphthf s-i 2 ene dihydridt o s 200-210 ll "C S3 C 10 H 8 , Naphtha ene, 218, m.p. 79 f! J&* C M?thyl- j-^ naphtha!- ) fl 9 , ene ( p< 1-2 C 12 H] 2 , Diniethy naphthalene, 25: "1^ 270 1 .S d | o *^ , "o C n H2n+3, Solid PH 41 Paraffin d 1 OB 6 [STITUENTS OF COAL TAR. 355 'Hydrocarbons of other Series. Isitrogenised Bodies. Oxygenated Bodies. Sulphur Compounds. /-Methyl E[ 3 X, Ammonia (C 2 H 6 S, Methyl sulphide, 41) (C 4 H 10 S, Ethyl sul- phide, 91) } 6 H 12 , Hexahydro- benzene, 69 1 isocyan- C 2 H 3 N,J ide, 60 1 Acetoni- \. trile, 81 C 2 H 6 0, Alcohol, 78 (C 2 H 6 S, Ethyl sulphydrate, 36) CS 2 , Carbon di- sulphide, 46 C 7 H 14 , Hexahydro- toluene, 97 C 4 H n N, Butyl- ainine, 75 H 2 0, Water, 100 C 4 H 4 S, Thiophene, 84 C 8 H 16 , Hexahydro- meiaxylene, 118 C 4 H 5 N, Pyrroline, 130 C 5 H 5 N, Pyrid- C 2 H 4 2 , Acetic C 5 H 8 S, Thiotolene, 113 ine, 116 acid, 119 C 6 H 8 S, Thioxene, C 6 H 7 X, (o. 124 137 Picol- 4 CgHg, Cinnamene, ine, (???. 140 145 C 7 H 9 ?T, Lutid- ine, 154 C fl H 14 , Nonone, 174 C 8 H H N, CoUid- . ine, 170 C 7 H 7 ^, Aniline, 182 9 C 6 H 6 0, Phenol, 182 C 9 H 13 N, Parvol- f. P TT C\ ( ' 18 ine, 188 p. 7 i -s "i. 198 ^3 \ P. 201 C 8 H 10 0, Xenol/212 C 10 H 15 ^, Corid ine, 211 (C 9 H 12 0, Cumenol) C 9 H 7 N, (2201 C n H 17 X, Rubid- Leucoliue, ( 238 ine, 230 C ]2 H 10 , Diphenyl, 254, m.p. 70-5 C 10 H ]Sr, (254 Lepidine, "( 268 CjsHjgN, Virid- ine, 251 C 7 H 6 0, Benzoic acid, 250, m.p. 120 (Cj.>H 12 , Acetnaph- thene dihydride, C-nHuN, Crypt- idine, 272 260) C 12 H 10 , Acetnaph- thene, 285, m.p. 95 C 12 H 13 ?T, Tetra- coline, 292 C 10 H 8 0, (a. 278-280 thol, ' Picene, m.p. 338 Benzeryth rene, m.p. 307 356 DISTILLATION OF COAL TAR. in company with the steam, &c. The ammoniacal liquor forms a lower layer which can be readily separated from the first light oils. The point when the shoot should be changed is indicated pretty accurately by a " break " or comparative cessation of distillation, together with a peculiar noise known as " the rattles." On further heating, the distillation recommences and the second light oils come over regularly. The point for again changing the shoot is in some works that at which a sample of the distillate sinks in water, while in other cases the solidification of the distillate on cooling, from the crystallisation of naphthalene, is the indication relied on. At a higher temperature, a distillate is again obtained which remains liquid on cooling. The commencement of the anthracene oil period may be ascertained by the thermometer immersed in the vapour, but is commonly deduced from the quantity of the distil- late. It may also be considered to commence at the point when the distillate again deposits solid matter on being completely cooled. Sometimes the anthracene oils are subdivided into first and second "green oils," and "red oil." The distillation is sometimes stopped when the oil sets to the consistence of butter on cooling, but is now usually pushed as far as possible short of actual coking, the residue remaining in the retort consisting of pitch, which, after cooling, is run out into tanks. The proportions of the various products obtained necessarily vary largely with the character of the tar distilled and the details of the mode in which the operation is conducted. These differ in each works and in the same works at different times. A com- parison of the general yields of London arid country tars will be found on page 358. The general composition of the various fractions obtained by the distillation of coal tar will be regulated chiefly by the boiling points of their leading constituents, but the vapour-densities, vapour-tensions, and relative abundance of the constituents of the tar also largely affect their behaviour in the still. Thus, naphthal- ene is found in notable quantity in all the fractions from second light oils to anthracene oil, and is even, deposited from the purified illuminating gas itself. The table on pages 354 and 355 gives the names, formulae, and boiling points l of the numerous bodies the presence of which in coal tar may be considered to be fairly well established, while other more volatile products of the distillation pass wholly into the gas. The presence in coal tar of certain other compounds which do not 1 The figures appended to the names of the constituents are their boiling points on the Centigrade scale. In the case of most of the compounds of very high boiling point the melting points are also added. ASSAY OF COAL TAR. 357 appear in the table is strongly suspected ; while of the constituents of the large fraction of coal tar distilling between 240 and 270 C., and of the anthracene oils, much still remains to be learned. Of the composition of the residue or pitch still less is known. ASSAY OF COAL TAR. The assay of coal tar is usually limited to a laboratory operation, in which the various fractions are collected as nearly as possible under the same conditions as those which pertain to the large scale, though the details will necessarily vary with circumstances. With practice, good results are obtained with as small a quantity as 10 ounces of the tar, the yields corresponding closely with those given on a large scale ; but the chief value of such laboratory operations is for comparing different samples of tar. The follow- ing mode of operation is that recommended by B. Nickels. 1 250 c.c. or 10 ounces measure of the tar is placed in a retort which it only one-third fills, so as not to spoil the distillate if there is much frothing during distillation. The retort should be supported on a cup-shaped piece of coarse wire-gauze, placed in an aperture in a sheet-iron plate. Over the retort is placed a dome, made by removing the bottom from a tin can or bottle, and cutting out a piece of the side to allow the neck of the retort to pass through. This contrivance confines the heat, and prevents the distillate or heavy vapour from falling back ; indeed, without some such arrangement a satisfactory assay of coal tar in glass is nearly impossible. The products obtained by the distillation are: (1) ammoniacal liquor; (2) total light oils; (3) creosote oil ; (4) anthracene oils ; and (5) pitch. In obtaining these frac- tions, the character of the distillate is amply sufficient to indicate the point at which the receiver should be changed. No thermo- meter is necessary, nor need any condensing arrangement be attached to the retort. The lamp being lighted, 2 the ammoniacal liquor and naphtha are collected together in a graduated cylinder, which is changed when a drop of the distillate collected in a test- tube of water begins to sink. After standing, to allow perfect separation of the ammoniacal liquor and light oils, the volume of each is observed, and, if desired, the strength of the former can be ascertained in the usual way by distillation with lime and titration of the distillate. The quantity of light oils is too small to allow of any further fractionation for benzols, &c. The next fraction of the distillate consists of creosote oil. At 1 The author is indebted to Mr Nickels for the communication of a number of valuable facts and methods connected with coal-tar products. 2 A powerful bunsen should be used, as towards the close of the operation it is necessary to maintain the wire-gauze at a red heat. 358 ASSAY OF COAL TAE. first it will contain much naphthalene, and will probably solidify in white crystals on cooling, but afterwards a more fluid distillate is obtained. At a still later stage, a drop of the distillate collected on a cold steel spatula will be found to deposit amorphous solid matter of a yellow or greenish-yellow colour, when the receiver is again changed, the fraction measured, and, if desired, assayed for carbolic acid and naphthalene, as described in the section on " Creosote Oils." With modem London tars this fraction is usually semi-solid, and must be measured whilst quite warm. The next fraction of the distillate is rich in anthracene, and not unfrequently condenses in the neck of the retort as a yellow, waxy substance, which may be melted out by the local application of a small bunsen-flame. The collection of anthracene oil is complete when no more dis- tillate can be obtained, and the pitch intumesces and gives off heavy yellow fumes. The distilled fraction is then measured and cooled thoroughly, and the resultant pasty mass pressed between folds of blotting paper, weighed, and assayed for real anthracene by the anthraquinone test. The result is calculated into crude anthracene at 30 per cent., a standard which is generally adopted by manufacturers. When the distillation for anthracene oil is complete, the retort may be allowed to cool, and when almost cold its body should be plunged into cold water. This produces a rapid surface-cooling and shrinking of the pitch from the glass, which may then be broken away and removed by gentle tapping, leaving the cake of pitch clean and ready for weighing. The following figures, communicated by B. Nickels, show the results obtained by the assay of four representative samples of London tar. The apparent excess is due to the tar having been measured and the pitch weighed: A. B. C. D. Ammoniacal water, . 2'5 37 80 5'0 Total light oils, . . 2 '5 3 "4 0'5 3 "2 Carbolic and creosote oils, 21 '3 17'0 S3'0 20'0 solid solid solid solid Anthracene oils, . . 17'0 17'0 13'0 13'0 semi-solid semi-solid semi-solid semi-solid Pitch (grammes per 100 c.c.), 59 '4 60 '0 58 "0 62 "0 102-6 lOl'l 1022 103-2 Pressed anthracene, 4'0 ... 1 '5 Containing real anthracene, 13'4/ 25 '68% - 30% crude anthracene in tar, 1 '8 1 '47 1 '3 The following table shows the mean composition of the fore- going samples in juxtaposition with the general yield of English country tar : COAL-TAR PITCH. 359 London. Country. Ammoniacal water, . . 4*5 per cent. 4 per cent. Total light oils, 2'4 ,, 3 ,, Carbolic and creosote oils, 20 '3 ,, 22 ,, Anthracene oils, . . 15 '0 ,, 4 ,, Pitch (grammes. per 100 c.c.), 59'9 ,, 67 1021 100 The methods of further examining the various fractions ob- tained in the first distillation of coal tar will be found fully described in the sections on " Commercial Benzols," " Naphthal- ene," "Anthracene," and "Creosote Oils." COAL-TAR PITCH. This is the residue remaining in the still after the first distilla- tion of coal tar, and usually amounts to about two-thirds of the weight of tar operated on. Its physical characters depend some- what on the kind of coal distilled and the point at which the distillation was arrested. Thus, soft pitch is obtained if the process is stopped when the oils distilling have a density of about 1'090, and hard pitch if it is continued till the specific gravity of the products distilling reaches 1*120. In order to obtain a large yield of anthracene, the distillation is often pushed as far as possible, and the residual hard pitch diluted with a certain propor- tion of creosote oil or anthracene oil, whereby a product of any requisite softness can be obtained. A compounded pitch of this sort will yield a notable quantity of liquid oils when distilled, and, possibly, naphthalene, which last is much objected to. Soft pitch can be easily kneaded between the teeth, but mod- erately hard pitch with difficulty only, while hard pitch crushes to powder. Soft pitch is blacker and more, lustrous than hard pitch, which often has a greyish tint and is somewhat porous. In the latter case it is partly coked, and is unfit for making patent fuel, for which pitch of but moderate hardness is preferred. The specific gravity of hard pitch ranges from 1'275 to 1'300. Soft pitch softens at 40 C., and melts at about 60. Moderately hard at 60 80. Hard at 80 120. Contract-notes for pitch intended for exportation to the Conti- nent often stipulate that a sample is to " twist fairly after immer- sion for two minutes in water at 60 C., but not under 55 C. ; must contain at least 53 per cent, of volatile organic matter; and must be free from any extraneous matter, such as sand or grit." The twisting point and melting point of pitch are ascertained by F. G. Holmes by fixing several pieces of the sample (about J inch cube) on wires, by heating the ends of the 360 ASSAY OF COAL-TAR PITCH. wires sufficiently to press them into the pitch, and suspending them, side by side with a thermometer, in a beaker containing 500 c.c. of water, which is heated at the rate of about 5 C. per minute. The pitch is taken out from time to time, and the twisting point taken as the temperature at which the fragment can be fairly twisted round several times. The melting point is the temperature at which the pitch melts off the wire, avoiding premature dropping. The proportion of volatile organic matter in pitch ranges from 47 to 64 per cent. It is determined by gradually heating 1 gramme of the carefully-sampled and powdered pitch in a platinum crucible until distillation ceases. The operation should occupy about fifteen minutes, and must not be hurried, or the pitch may swell up and even boil over the sides of the crucible, leaving a very porous residue. A cover with a small aperture in the centre is then placed on the crucible, which is placed in a crucible-jacket and further heated for ten minutes over a powerful bunsen, and finally for ten minutes over a blast-flame. The residual coke, which should be dense and graphitoidal, is then weighed, and the volatile organic matter calculated from the loss. With care and attention to details the test gives constant results, but otherwise very discordant figures may be obtained. The coke may be burned and the propor- tion of a s h ascertained if the presence of sand or grit is suspected. According to H a b e t s, the ultimate percentage composition of good, hard coal-tar pitch is 75'32 of carbon, 8'19 of hydrogen, 16'06 of oxygen, and 0*43 of ash. Small proportions of nitrogen and sulphur are also present. The proximate composition of coal-tar pitch is very imperfectly understood. It always contains some of the high-boiling hydrocarbons of coal-tar, such as anthracene, phenan- threne, pyrene, chrysene, &c., together with "bitumene," and probably free carbon. 1 The form in which the oxygen exists is not known. Coal-tar pitch is wholly insoluble in water, but soluble to a greater or less extent in alcohol, and more completely in benzene and carbon disulphide. In cold petroleum spirit it is but little soluble, but by the boiling solvent it is somewhat more acted on, though the greater part remains undissolved. This behaviour dis- tinguishes coal-tar pitch from wood pitch and natural asphalt, for which it is sometimes substituted without acknowledgment. Methods of distinguishing coal-tar pitch from these materials are given on page 376. 1 "When pitch which remained after all oils of a density up to 1'120 had distilled over was treated successively with cold benzene, earbon disulphide, boiling benzene, and boiling alcohol, B e h r e n s obtained 23 '54 per cent, of a black powder resembling anthracite, and containing 91 to 92 per cent, of carbon, 3'1 of hydrogen, and 0'4 to 0'9 of ash. NATURAL BITUMENS. 361 The determination of anthracene in coal-tar pitch is described in the sequel. TAR FROM SIMON-CARVE COKE OVENS. This tar is the product of the distillation of coal at a high tem- perature, and hence approaches in composition the tar obtained in the manufacture of illuminating gas from Newcastle coal. The proportion of benzene and toluene is low, probably owing to im- perfect condensation, but the tar is very rich in naphthalene and anthracene, though the proportion of intermediate and anthracene oils is very small (W atson Smith, Jour. Soc. Chem. Ind., ii. 500). CRUDE HYDROCARBONS OF MINERAL ORIGIN. BITUMENS. Mineral products consisting essentially of a complex mixture of hydrocarbons are found in numerous localities, and under very varied circumstances. These products, of which petroleum may be regarded as the type, occur in all parts of the world, and, like coal, are not confined to any one geological formation. The natural hydrocarbons present every variety of aggregation, from the state of gas, as evolved from coal and petroleum, through the conditions of a thin mobile liquid like the naphtha of Persia, the viscous t a r of Rangoon, the elaterite or mineral india-rubber of Derbyshire, the wax-like ozokerite of Galicia, to the brittle, pitch-like asphaltum of Lake Trinidad. The origin of the bitumens or mineral hydrocarbons is, in many cases, very obscure. The subject has been treated in an able and exhaustive report by S. F. P e c k h a m. 1 The natural bitumens may be subdivided into a large number of species and varieties, but for the purpose of this work it is suffi- cient to classify them in a more general manner under the heads of petroleum, ozokerite, and asphaltum. The con- 1 Report on the Production, Technology, and Uses of Petroleum and its Pro- ducts, to the Hon. C. W. Seton, Department of the Interior, U.S. America. Professor Peckham (Report, page 67) concludes that all bitumens have, in their present condition, originally been derived from animal or vegetable remains, but that the manner of their derivation has not been uniform. He therefore excludes chemical theories of their formation, and points out that natural bitumens may be arranged in four classes : (1) Those bitumens which form, asphaltum and do not contain paraffin; (2) those bitumens that do not form asphaltum and contain paraffin ; (3) those bitumens that form asphaltum and contain paraffin ; and (4) solid bitumens that were originally solid when cold or at ordinary temperatures. Bitumens are not the product of the high temperature and violent action of volcanoes, but of the slow and gentle changes at low temperatures due to nieta- morphic action upon strata buried at immense depths. 362 CRUDE PETROLEUM. sideration of the different varieties of c o a 1 is beyond the scope of this treatise. Petroleum. Rock Oil. Mineral Oil. Liquid Bitumen, French Petrole ; Huile de Pierre. German Erdol ; Steinol. Petroleum is a natural oily liquid occurring in the earth at very varied depths, and in a great many localities. It is not confined to any particular geological formation. Thus the petroleum of the great Pennsylvanian field is derived from the Devonian and Carbon- iferous limestone formations, while that of California and Russia is found in Tertiary rocks. It does not follow, however, that petroleum is indigenous to the strata in which it is found, as, in some instances at any rate, it has undoubtedly undergone distil- lation. Petroleum is now obtained on a very considerable scale in the Caucasus, on the shores of the Caspian Sea, and smaller quantities are produced in Canada, Galicia, Hanover, and other localities, but by far the largest quantity is obtained from the Paleozoic rocks of the United States. The last source so completely overshadows all others, from a commercial point of view, that the following description applies chiefly to the American product : Crude natural petroleum is an oily liquid, varying in density from '78 to '97, the Pennsylvanian product ranging between '79 and '83. It has a characteristic odour, which is sometimes, but by no means invariably, disagreeable, and its colour varies from straw- yellow to brownish black (see footnote, page 381). Its coefficient of expansion varies considerably with its specific gravity, as is shown by the following table : l Specific Gravity at 15 9 C. Expansion -coefficient for 1 C. Under '700 '00090 700 to -750 -00085 750 to -800 -00080 800 to -815 -00070 over '815 '00065 Petroleum is insoluble in water, and but slightly soluble in alcohol, but it is miscible in all proportions with chloroform, ether, carbon disulphide, and hydrocarbons. It readily mixes with ordi- nary fixed oils, castor oil being an exception (page 128). CHEMICAL COMPOSITION OP PETROLEUM, Chemically, crude petroleum consists of a mixture of a consider- able number of hydrocarbons, not unmixed with small quantities of 1 On a stock of 1,000,000 barrels of petroleum, the shrinkage in winter amounts to 7,000 to 10,000 barrels. COMPOSITION OF PETROLEUM. 363 sulphuretted, nitrogenised, and oxygenised bodies. 1 All varieties of petroleum are combustible liquids, burning with a luminous, more or less smoky flame. Petroleum has an exceedingly variable composition, and is more or less volatile and mobile according to its content of bitumen and solid bodies. In general, it contains about 85 per cent, of carbon and 15 of hydrogen, but its elementary composition gives no idea of the variety of hydrocarbons contained in it. In short, the constituents of petroleum present the following varieties of character : (a) Their volatility is very different, for they extend from per- manent or nearly permanent gases to solids which do not boil except at very elevated temperatures (370 and 420 C.). (b) The volatility of these hydrocarbons is usually inversely as their density, the lightest oils being the most volatile. (c) The inflammability is of course a function of the volatility, the more volatile constituents taking fire on approach of a flame at any temperature, while the denser and less volatile oils require to be heated considerably before they can be inflamed or made to give off inflammable vapours. The hydrocarbons of petroleum belong to several series, the paraffins largely predominating in American petroleum, while members of other series are present in relatively large amount in the petroleum of other regions. Pennsylvanian petroleum has been most completely studied. A complete series of paraffins, from CH 4 to C 16 H 34 have been obtained from it; and the solid members, C 25 H 52 , C 2 .j.H 56 , and C 30 H 60 , are also present, especially in the oils from the Bradford 1 The proportion of nitrogen in petroleum from Mecca, Ohio, is 0'23 per cent., while in that of the Hay ward Petroleum Company, California, it reaches 1 '11 per cent. Peckham states (Report, p. 69) that fresh Californian petroleum soon becomes " filled with the larvae of insects to such an extent that pools of petroleum become pools of maggots." It is well known that Canadian petro? leum contains sulphur, but the Pennsylvanian and West Virginian oils are remarkably free from it. An oil from the Kirghish Steppe is said to contain 1 '87 per cent, of sulphur, and to be purified with great difficulty. A sample of Californian petroleum examined by Peckham contained sufficient sulphur to form a deposit in the neck of the retort in which it was distilled. To detect sulphur in petroleum the oil should be heated to boiling for some time with a fragment of metallic sodium, in a flask furnished with an in- verted condenser. After cooling, water is added drop by drop to the contents pf the flask till the sodium is oxidised. More water is then added, the aqueous liquid separated, and the solution tested with a drop of sodium nitroprusside, which will produce a fine violet-blue coloration if the petroleum contains sulphur. 364 AMERICAN PETROLEUM. district. 1 Is o-p araf f ins, as well as the normal hydrocarbons, exist in American petroleum. 2 The paraffins from CH 4 to C 4 H 10 are gaseous at ordinary temperatures, and hence escape in admix- ture with hydrogen from petroleum wells, or when the petroleum is stored or gently heated. 3 The hydrocarbons of the paraffin series from C 5 H ]2 to C 15 H 32 constitute the greater part of the liquid portion of American petroleum, one of the most characteristic con- stituents being h e x a n e, C 6 H 14 , a hydrocarbon which is closely allied to cellulose, C 6 H 10 5 . The o 1 e f i n s from C 10 H 20 to C 12 H 24 have been isolated by Warren from American petroleum, and doubtless other of the higher members of the series are pre- sent. Gaseous olefms also occur. Pseudo-olefins, similar to these characteristic of Russian petroleum, are also present. Ben- zene and its homologues exist in traces in American petroleum, 4 1 To extract solid paraffin from crude petroleum, S. P. Sadtler mixes the oil with several times its volume of ether, and places the liquid in a freezing mixture, when "almost all the dissolved paraffin will separate and can be filtered off." 2 Schorlemmer considers that petroleum consists chiefly of an inextricable mixture of isomeric and homologous paraffins, in which, however, the normal paraffins predominate. 3 Petroleum gas from the " gas-wells" of Pennsylvania has been found to contain from 40 to 94 per cent, of methane, CH 4 , with smaller proportions of hydrogen and ethane, CH 6 , and traces of higher homologues. Small proportions of olefins are also present. On the other hand, the liquid obtained by J. J. C o 1 e m a n, by the action of cold and pressure on the gases produced in the distillation of bituminous shale, consisted chiefly of butylene, C 4 H 8 , amylene, C 5 H 10 , and hexylene, C 6 H 12 ; that is, members of the olefin series. S. P. Sadtler passed petroleum gas through ab- solute alcohol, which does not dissolve hydrogen, and methane only slightly, ethane, propane, and higher homologues being soluble in increasing amount. The absorbed gases are subsequently driven out by heating the alcohol, and were collected over mercury and analysed, when they proved to be chiefly ethane and propane. By passing the petroleum gas through bromine, neutral- ising the excess with soda, and diluting, colourless oily globules of dibromides of olefins were separated. Petroleum gas is employed for metallurgical purposes in the iron and steel works of Pittsburg, and the town of Bradford, Penn., is illuminated with it. 4 The method pursued by Schorlemmer for the detection of the hydrocar- bons of the benzene series was as follows : The portion of oil distilling below 150 C. was treated with concentrated nitric acid. The acid liquid was diluted, and the water separated from the heavy nitro-products, which possessed the odour of bitter almonds. These nitro-compounds were treated with tin and hydrochloric acid, and the solution thus obtained was distilled with caustic potash. The aqueous distillate, in which some drops of an oily liquid were suspended, had the odour of aniline, and gave with a solution of bleaching powder a most distinct violet coloration. The rosaniline reaction could be obtained by heating one of the oily drops with mercuric chloride. RUSSIAN PETKOLEUM. 365 and among the less volatile constituents anthracene, chrys- ene, pyrene, fluoranthrene, and thallene exist in small quantity. 1 Canadian petroleum contains various hydrocarbons of the paraffin and olefiii series, and is richer in aromatic compounds and poorer in gaseous paraffins than the Pennsylvanian product. It con- tains a notable quantity of sulphur compounds and yields about 3 per cent, of solid paraffin. Russian petroleum has of late acquired considerable commercial importance. It is chiefly obtained in the neighbourhood of Baku on the Caspian Sea, but is also found in other parts of the Caucasus. A fraction of given boiling point has a higher density than a similar fraction of American petroleum or Scotch shale oil, and the viscosity is more readily decreased by heat. It usually yields no solid paraffin. Caucasian petroleum is scientifically interesting from its peculiar composition. Beilsteiii and Kurbatow (Ber., xiii. 1813; Jour. Chem. Soc., xl. 159) could not obtain any products of constant boiling points, even after nine distillations, nor were they able to extract any benzenoid hydrocarbons by treatment with fuming nitric acid nor any olefins with bromine. Their researches, as extended by Schiitzenberger and I o n i n e (Compt. rend., xci. 823 ; Jour. Chem. Soc., xl. 705) and by Markownikoff and Oglobini (Jour. Chem. Soc., xlii. 390 ; xlvi. 1276) have shown that Caucasian petroleum consists chiefly of a mixture of pseudo-olefins, having the general formula C n H2 n . These hydrocarbons, called n a p h t h e n e s, are isomeric with the olefins, and apparently also with the hexahydrides of the benzene hydro- carbons or paraffenes, C n H 2n -6H 6 , obtained synthetically by Wreden. 2 With the exception of the hydrocarbon C 13 H 26 , all the naphthenes from C 8 H 16 to C 15 H 30 have been separated from Caucasian petroleum. They boil at somewhat lower temperatures than the isomeric olefins and the normal paraffins containing the same number of carbon-atoms, and at approximately the same temperatures as the synthetically-prepared paraffenes; but the densities of the Caucasian hydrocarbons are notably greater than those of the isologous paraffins from American petroleum. Thus, while normal octane, C 8 H 18 , boils at 124 C. and has a density of *7188 at 0, octo- 1 Sadtler found crude petroleum to strike a deep blood-red colour with picric acid, like the colour of its compound with anthracene, &c., while the purified oil gave no such reaction. 2 Dr Kramer, of Berlin, considers that the available methods of examin- ation fail to show whether the naphthenes are definite compounds or mixtures of paraffins with benzenoid hydrocarbons, but he inclines to the latter opinion. 366 CAUCASIAN PETROLEUM. naphthene, C 8 H 16 , boils at 119 and has a density of '7714. Similarly, C 10 H 26 boils at 202 and has a density of '7655, while C 12 H 24 boils at 196 and has a density of '8027 at 17. The naphthenes do not form nitro-derivatives, and resemble the paraffins in not yielding additive-compounds and in being con- vertible into chlorinated derivatives from which alcohols are obtain- able. When oxidised, the naphthenes form oxidation-products, or are converted into higher isologues. The higher boiling portions of Caucasian petroleum probably contain hydrocarbons of the acetylene and higher series, while 10 per cent, of the petroleum consists of benzenoid hydrocarbons belonging to known series, and also a series of hydrocarbons isomeric with styrolene and its isologues. These compounds form brominated derivatives, but no additive-compounds ; their benzenoid character is exhibited in the formation of nitro- and sulpho- derivatives. 1 The petroleum also contains neutral and acid oxy- genated bodies. A petroleum examined by Markownikow yielded a fraction boiling between 220 and 230 C., which contained 5'25 per cent, of oxygen. The investigation of Russian petroleum is very difficult, owing to the facility with which the constituents break up into other bodies on distillation, especially during the latter part of the process. 2 Galician petroleum, according to Lachowicz (Ann. der Chem., ccxx. 188; Jour. Soc. Chem. Ind., ii. 473), contains a number of paraffins and also a large series of aromatic hydrocarbons. 3 The 1 A petroleum from near Tiflis, examined by Beilstein and K u r b a t o \v Jour. Chem. Soc., xl. 1020), yielded a fraction of lower boiling point contain- ing the paraffins C 4 H 10 to C 7 H 16 , with a little benzene and toluene. By treat- ing the fraction of a Caucasian petroleum boiling between 180 and 200 with fuming sulphuric acid, Markownikoff and Oglobini found that various sulphonic acids were formed, while the hydrocarbons of the formula C n H2n were left unchanged. Isomerides of cymene, metamethyl-propylbenzene, and pro- bably durene, were present. The 240 to 250 fraction contained a modification of propylnaphthalene (C 13 H ]4 ), then C 12 H U and C n H 14 (the last probably be- longing to the cinnamene series), and finally C 15 H 30 (? C 15 H 10 ) (Jour. Chem. Soc., xlii. 390; xlvi. 1276). 2 When passed through an iron tube heated to bright redness, Caucasian petroleum yields an abundant deposit of carbon, Avhich soon chokes the tube, the metal itself being strongly corroded. The volatile products consist largely of benzene and its homologues, with naphthalene and anthracene. This reaction has been recently utilised for the production of benzene and anthracene from Russian petroleum. 3 Pawlewski (Ber., xviii. 1915) found in a petroleum from Kleczany about 2 per cent, of aromatic hydrocarbons, consisting chiefly of benzene and para- xylene. PETROLEUM DISTILLATION. 367 fraction boiling between 97 and 100 C. consists chiefly of heptane with some hexahydrotoluene, but the presence of hexahydroxylene was not established. The first six fractions obtained by distilling the crude petroleum on the large scale are not acted on by bromine, but the seventh and higher fractions absorb bromine with evolution of heat. Hence it is probable that olefins do not pre-exist in the petro- leum, but are formed during the distillation by the decomposition of paraffins (see also page 327). Hell and Meidinger have isolated from Wallachian petroleum an acid forming alkali-salts re- sembling soft soap. Other homologous acids are probably present. Hanoverian petroleum, according to C. E n g 1 e r (Jour. Soc. Chem. Ind., i. 314), contains hydrocarbons both of the paraffin and olefin series, besides notable quantities of aromatic hydrocarbons (e.g., pseudocumene, mesitylene, and probably hexahydrometa- xylene). Sulphur compounds are also present. Rangoon tar is a heavy variety of petroleum, of a semi-solid con- sistency, owing to the presence of about 40 per cent, of solid paraffin (see page 380). By fractional distillation, Warren and S t o r e r proved the presence of the paraffins from C 7 H 16 to C 9 H 20 , olefins from C 9 H 18 to C 13 H 26 , besides xylene, cumene, and naphthalene. The composition of the petroleums from other sources has been but very imperfectly ascertained. The behaviour of some of them on distillation is described in the sequel * (See also B. Redwood, Jour. Soc. Arts, xxxiv. 878.) 1 The following is an outline of the usual process of petroleum distillation as conducted in America: The oil is heated in large stills holding from 600 to 1200 barrels. The more volatile portions soon come over ; they are either burnt or condensed by artificial cold and pressure. The liquids thus obtained are known as "cymogene" and "rhigolene." After these, products condensible by cold water are obtained, the first portions having a density of "636, the product becoming heavier as the distillation proceeds. (The distillate obtained in this part of the operation is usually again distilled, when it yields "gasoline," ' ' naphtha," and ' ' benzine. ") When the liquid passing over acquires a density of 725 to "750 according to the works' custom the stream is diverted from the "naphtha" tank to the "kerosene" receiver, where it is collected till its gravity reaches '840 to '845. The residue is then transferred to other stills^ and generally to other works, where it is distilled to dry ness to obtain lubri- cating oils and paraffin. The residue in the still is only combustible with difficulty, but is used as fuel. In some cases the operation is arrested before actual coking occurs, in which case the residue has the consistency and characters of thick tar. The purification and fractionation of the first products are conducted in much the same manner as with shale oil (page 344). On the Caspian Sea, the distillation of the petroleum is conducted as a con- tinuous process, a stream of oil flowing through the entire series of twenty-five stills. This method is peculiarly suited for the treatment of Russian petroleum, since it yields comparatively little burning oil, and the residue is almost as 368 TREATMENT OF PETROLEUM. The method of treating crude petroleum for the manufacture of commercial products varies considerably with the character of the crude article and the practice of the works, but it is always essentially a process of fractional distillation, sometimes supplemented by a decomposing action in the still induced by the injection of super- heated steam. The character and proportion of the various pro- ducts obtained depend largely on the nature and source of the oil and the details of the mode of treatment, which is capable of con- siderable variation in detail (see page 380). As a rule, the lighter and more volatile portions are fractionated into a number of products, known commercially as cymogene, rhigolene, gasolene, naphtha, and benzine or benzole ne; but in many cases the proximate separation of the products of the distillation of crude petroleum is less complete, only three principal products being made, namely, naphtha, kerosene, and lubricating oil. By the present system of manufacture, with some " cracking " of the heavier oils (see page 327), about 75 per cent, of burning oil, flashing at 68 F. by Abel's test, may be obtained from crude American petroleum. The yield of higher class oils (such as would pass English inspection) is proportionately smaller, and of "water- white oil" only from 12 to 20 per cent, is obtained. The proportion of naphtha obtainable from American oil varies from 9 to 18 per cent., according to the age of the oil-producing territory. Caucasian petroleum yields very different proportions, the proportion of burning oil flashing at 32 C. and of "821 specific gravity being only about 27 per cent.; but a much larger percentage of oil of lower flashing point or higher specific gravity can be obtained. 1 The fluid as the crude oil. The distillate is collected in three fractions : light benzine (754), heavy benzine or "gasolene" (787), and kerosene ('820 to '830). The residue has a density of '903, and yields on distillation about 30 per cent, of lubricating oil and 15 of "solar oil" (sp. gr. '860, flashing point 105 C.), the remainder being commonly used as fuel (B. Redwood, Jour. Soc. Chem. Ind., iv. 74). Of late, however, promising attempts have been made to employ the astatki for the production of benzols and anthracene by subjecting it to a full red heat. Baku petroleum contains little or no paraffin wax or other solid hydrocarbons, but that obtained on the other side of the Caspian yields as much as 6 per cent, of solid hydrocarbons. 1 B. Redwood (Jour. Soc. Chem. Ind., iv. 74), who gives the above figures, also states that the Caspian Company manufacture three qualities of the burn- ing oil, of the following characters : Quality. Specific Gravity. FlashPoint; C. Yield per cent. 1 815 30 20 2 820 25 33 3 821 to -822 22 38 ASSAY OF CRUDE PETROLEUM. 369 proportions and densities of products from Russian petroleum obtained by Kagosine & Co. will be found on page 402. The fractions of the crude petroleum obtained by distillation are purified by treatment with a limited quantity of strong sul- phuric acid, and then washed with caustic soda and finally with water. In some works they are then redistilled over caustic soda. In Canada, the burning oil is treated with a solution of litharge in caustic soda, to remove sulphur-compounds. ASSAY OF CRUDE PETROLEUM. According to a definition adopted by the New York Produce Exchange in 1879, "crude petroleum shall be understood to be pure natural oil, neither steamed nor treated, free from water, sediment, or any adulteration, of the gravity of 43 to 48 Baume " ( = 8092 to '7865 specific gravity). 1 The usual range in the specific gravity of the New York crude oil is between '790 and '800. Each parcel is usually a mixed product from a number of wells. The water and sediment are usually determined by mixing the sample with an equal quantity of petroleum spirit, and keeping the mixture at 49 C. (=120 E.) in a graduated glass vessel for at least six hours, after which the liquid is allowed to cool and settle for a period of not less than 2 hours for light grade oils, increasing to 18 hours for the heaviest qualities. Besides this test and the determination of the specific gravity, the ordinary characters relied on as commercial tests of the quality of crude American petroleum are : its specific gravity, its odour and colour, its feel when rubbed between the fingers, and the percentage of naphtha yielded on fractional distilla- tion. 2 The crude oil of the New York market will generally furnish from 12 to 15 per cent, of naphtha of '700 specific gravity, and the proportion should not exceed 17 per cent. It will yield, in addition, from 9 to 12 per cent, of benzine of "730 gravity and about 60 per cent, of burning oil at '795 specific gravity. The 1 In using Baume' s hydrometer for petroleum and other liquids lighter than water : Specific Gravity = ^J and Degrees Baume- -130. 130 + B ' sp. grav. 2 Crude American petroleum was formerly frequently adulterated with petroleum spirit. As this was less valuable than the heavier and less volatile kerosene oil, it not unfrequently found its way back to the wells, to be repumped as crude petroleum, or was even directly added to the latter in the tanks. The difference in the commercial value of the products is not now sufficiently great to afford much inducement to continue this practice, which, however, has extended to Baku. Excess of the lighter oils reduces the density of the oil, and causes it to give off inflammable vapour at a lower temperature, while the percentage of naphtha yielded on distillation is increased. Hence the best petroleums give only a moderate percentage of naphtha. VOL. II. 2 A 370 ASSAY OF CRUDE PETROLEUM. residue contains a quantity of dry paraffin scale equal to about 2J per cent, of the crude oil. 1 For the assay of crude petroleum by distillation 250 or 500 c.c. should be employed, and the operation conducted in a retort furnished with a good condensing arrangement, in the same manner as is directed for the examination of " Commercial Benzols." The cylinders in which the distillates are collected should be surrounded with water kept constantly at 15 C. A small hydrometer con- tained in the cylinder in use will indicate when the thoroughly mixed fraction acquires the standard density, at which point the flame is withdrawn from the retort, the condenser allowed to drain, and the volume of the distillate carefully observed. By employing a thermometer-plummet (page 13) instead of the hydrometer, more accurate results are obtainable, and the distillation can be conducted on a smaller quantity of petroleum. Some useful hints on the assay of crude petroleum have been published by Nawratil (Dingl. polyt. Jour., ccxlvi. 328, 423 ; Jour. Soc. Chem. Ind., ii. 37, 129), who has examined a number of Galician petroleums. He distils 500 c.c. in a glass retort. The distillate collected below 150 C. is regarded as light oils or naphtha, that from 150 to 300 as burning oil, and that from 300 to 400 as heavy oils. The densities of the original samples (18) ranged from '902 (Harklowa) to '799 (Kenczany), and the proportions of the several fractions showed similar variations. The 1 The density of the first ninety fractions, of 1 per cent, each, obtained by distilling the average petroleum oil of the New York market, has been deter- mined by Bourgongnon. The following table shows the density of every tenth fraction obtained, the original oil having a specific gravity of 7982 at 15 C. :- 1st Fraction 10th 20th 30th ,, 40th Sp. Gr. 679 50th Fraction 705 60th 728 70th ,, 750 80th ,, 765 90th Sp. Gr. 777 790 815 829 825 The products yielded by the distillation of the same crude oil were : naphtha at 700, 17% 5 benzine at 730, 9% ; burning oil at 783, 64% ; residue and loss, 10% ; and the residue contained about |th of its weight of solid paraffin. The results obtained by the distillation of petroleum on a laboratory scale are not strictly identical with those yielded in practice, as a large propor- tion of the heavier fractions are often "cracked" into burning oil. Thus the Standard Oil Company, at their New Jersey works, obtain from 6 to 15 per cent, of naphtha, from 75 to 80 per cent, of burning oil of two qualities, and a residue of 8 to 10 per cent., which by subsequent distillation yields lubricat- ing oil. OZOKERITE. 371 light oils varied from 43*5 to 3*4 per cent., the 150-300 fraction from 45'4 to 29'2, and the heavy oils from 56'7 to 22*8 per cent. The flashing point of petroleum is an indication of con- siderable importance, but is more especially connected with the examination of refined petroleum or kerosene, under which head the subject is fully discussed. Ozokerite. This substance, known also as cerasin, cerite, or min- er a 1 wax, usually occurs in the neighbourhood of petroleum springs, and in association with bituminous sandstone, clay-schist, gypsum, and common salt. Though not a very abundant substance, ozokerite occurs in many parts of the globe, the most remarkable and best-known deposit being that in the Miocene rocks of Galicin, on the slopes of the Carpathian Mountains, and also on the "Wallachian side of the range. It is also worked on the island of Tscheleken in the Caspian and at Swatoi-Astrow, near Apsheron, where a variety called neft-gil is found. It exists also in Turkestan, and a valuable deposit has been found in Utah. Ozokerite consists chiefly of a mixture of solid paraffins, though oxygenated compounds are also present. 1 Its commercial interest is chiefly as a source of paraffin wax, though liquid hydrocarbons are also obtained by the distillation of the inferior kinds. Crude Galician ozokerite is a scaly or waxy substance, with a resinous fracture. It is usually brittle, but as hard as beeswax. It becomes negatively electric by friction and exhales an aromatic odour. Crude ozokerite varies much in appearance. The finest varieties are transparent, of a pure yellow or greenish colour, and can easily be kneaded between the fingers. Poorer kinds of Galician ozokerite are black and soft, or hard, with a fibrous structure and conchoidal fracture, varying in colour from yellow (" butter-stone ") to black. Some pieces are as hard as gypsum, and are dichroic, the transmitted light being a pure 1 R. Heger states that the composition of ozokerite is best represented by the formula C n H2n, and that it appears to have been formed by the oxidation and decomposition of the hydrocarbons of naphtha, since the action of oxygen on these compounds simply eliminates hydrogen. Thus, naphthalene gives water and dinaphthyl : 2C 10 H 8 + = C 20 H 14 + H 2 0. By further oxida- tion, hydrocarbons of the formula C n H2n are obtained, which react with paraffins to form very complex carbon compounds of various melting points, as for example : 2C 8 H 18 + 2 =C 16 H 32 + 2H 2 0; and C 16 H 32 + C 8 H 18 + = C, 4 H 48 + H 2 0. 372 ASSAY OF OZOKERITE. yellow, and the reflected dark green. The melting point is very variable, ranging from 58 to 100 C. 1 Ozokerite is separated from the gangue by being melted, and, after being pressed, is treated with alkali and filtered through fine animal charcoal. 2 Peritz obtained from 75 to 82 per cent, of crystallised paraffin from Boryslau ozokerite, and 9 to 13 per cent, of light oils. Ozokerite refined in England yields nearly 70 per cent, of white paraffin. The purified substance constitutes cerasin, which name should be confined to the solid paraffin obtained with- out distillation. Inferior ozokerite is usually distilled with superheated steam, when it yields paraffin wax, lubri- cating oil, naphtha, &c. 3 ASSAY OF CRUDE OZOKERITE. According to B. Lach (Chem. Zeit., ix. 905 ; Jour. Soc. Chem. Ind., iv. 488), for the valuation of crude ozokerite 100 grammes of the sample should be treated with 20 grammes of fuming sul- phuric acid in a tarred basin. The mixture is heated to 170 to 180 C., and continuously stirred till all sulphur dioxide has escaped. On reweighing the basin, the loss is said to represent 1 The raw ozokerite occurring on the island of Tscheleken, in the Caspian Sea, is a brownish-black sticky mass, almost entirely soluble in boiling benzene. On extracting it with ether, the oily portion and colouring matter are dissolved, leaving a hard residue. On boiling this with acetic ether the paraffin is dissolved, and by repeated treatment with animal charcoal, &c., may be obtained in lustrous crystals, melting constantly at 79 C., and con- taining 85 '10 of carbon and 14*57 of hydrogen (Beilstein and W i e g a n d, Ber., xvi. 1547; Jour. Chem. SOC.,X\LV. 1073). 2 Frequently both acid and alkali are used in the purification of ozokerite, and fuller's earth and magnesium silicate have been substituted for the char- coal. The charcoal used is preferably the fine carbonaceous residue produced in the manufacture of potassium ferrocyanide. The purification of ozokerite with sulphuric acid is attended with considerable loss, owing to the action of the acid on the oxygenated bodies present. 3 Galician ozokerite yields on distillation about 25 per cent, of petroleum, 21 of lubricating oil, and 36 of solid paraffin. A higher yield might doubtless be obtained by improved manipulation. B. Redwood (Jour. Soc. Arts, xxxiv. 886) gives the products as 5 per cent, of gaseous hydrocarbons, 3 per cent, of naphtha, 6 of semi-solid "ozokerine," 12 of soft paraffin (melt- ing at 44 to 46 C.), distilled ozokerite (melting at 61 C.), and a black waxy residue. The following are the products obtained by the distillation of Caspian ozokerite (neft-gil), according to Grabowski : 2 to 8 per cent, of benzine, 15 to 20 per cent, of naphtha, 15 to 20 per cent, of heavy oils, 36 to 50 per cent, of solid paraffin, and 10 to 20 per cent, of coke. Sometimes the products are less carefully differentiated, the chief being : 30 to 40 per cent, of benzine of 73 specific gravity, and 50to70 ,, solid paraffin melting at from 60 to 70 C. EEFINED OZOKERITE. 373 the volatile constituents, namely, petroleum and ivater. No allow- ance appears to be made for the loss due to the formation of sulphur dioxide and possible volatilisation of sulphuric anhydride. Probably a better plan would be to dilute the mixture, and separate and weigh the paraffin wax. Lach further directs that another quantity of 100 grammes of the sample should be treated with 10 grammes of the carbonaceous residue from the manufacture of potassium ferrocyanide, which has been previously dried at 140. A tenth part of the mixture (11 grammes) is then weighed into a tarred tubular filter, and extracted with benzene. The wax is esti- mated from the loss, or recovered by evaporating the benzene. REFINED OZOKERITE or CERASIN usually melts between 61 and 78 C., is quite odourless and colourless, and has a waxy section. A variety manufactured in Frankfort-on-the-Oder is said to melt at 83, and to be so hard as scarcely to yield to the finger nail. Cerasin possesses the general characters of paraffin wax, of which indeed it is merely a variety. Cerasin or refined ozokerite closely resembles bleached beeswax, but may be distinguished from the latter by its lower specific gravity (page 185), and by its absolute resistance of alcoholic potash (page 186), no trace of saponifiable matter being present. In admixture with beeswax, cerasin may be detected and approxi- mately determined by treating the substance with warm concentrated sulphuric acid (page 188), which completely destroys beeswax but leaves the hydrocarbon wax comparatively unattacked. Asphaltum. Compact Bitumin. Mineral Pitch. Asphaltum is a smooth, hard, brittle, black or brownish-black, resinous mineral, having a conchoidal fracture and a streak lighter than the main surface. The specific gravity varies from 1 to 1*68. Asphaltum melts when heated, and easily inflames, burning with a bright but very smoky flame. Asphaltum is a complex substance, consisting largely of the less volatile portions of petroleum. It consists chiefly of hydrocarbons, but oxygenated bodies are also present, apparently formed by the oxidation of unsaturated hydrocarbons, and many varieties, such as the bitumen of Judea, contain a notable proportion of sulphur in the form of some organic compound. In some American speci- mens of asphalt the sulphur exceeds 10 per cent. Asphaltum is insoluble in water, but dissolves partially in alcohol and more readily and completely in carbon disulphide, coal-tar naphtha, petroleum spirit, and oil of turpentine. Some varieties are more or less soluble in alkalies and alkaline carbonates. When carefully heated, or even when distilled with water, 374 ASPHALT ROCK. asphaltum yields a volatile oil, called by Boussingault "petrolene," but which doubtless consists chiefly of a mixture of paraffins. The residue of "asphalten e," which remains when the petrolene is wholly driven off, is a solid black substance of strong lustre and conchoidal fracture, which softens at about 300 C. and decom- poses below its fusing point. Asphaltum is found in many parts of the world, the island of Trinidad, the shores of the Dead Sea, and the Caucasus being among the best known localities. ASPHALT ROCK. Rock Asphalt. Asphaltum very often occurs in intimate association with sand or limestone, the latter being often very pure and of dolomitic character. The mineral, which may be conveniently described as " asphalt rock," is found especially in the Upper Jurassic formation, interstratified with beds of ordinary limestone. It is now exten- sively employed for paving purposes. The following figures byM. Durand-Claye show the proxi- mate composition of some leading varieties of native rock asphalt employed for paving. Valde Travers (Switzerland). Lnbsann (Alsace). Sevssel (Am, Fiance). Maestu (Spain). Ragusa (Sicily). Water and other ) matters volatil- I 0-35 3-40 0-40 0-40 0-80 ised at 100 C., . ( Bituminous matter, 870 11-90 9-10 8-80 8-85 Sulphur in organic ) combination or [ 0-08 , 4-99 trace. ... free state, . j Iron pyrites, 0-21 4-44 Alumina and oxid of iron, | 0-30 1-25 0-05 4-35 0-90 Magnesia, o-io 0-15 0-05 3-85 0-45 Lime, . 49-50 38-90 50-50 570 49-00 Carbonic acid, 40-16 31-92 39-80 8-15 39-40 Combined silicate, 11-35 Sand, . : 60 s'-05 b-'io 57-40 0-60 100-00 100 -OG 100-00 100-00 100-00 The Yal de Travers and other native calcareous asphalts have a deep brown or black colour, and break without any sign of cleavage, the fracture being earthy and very similar to chocolate both in colour and appearance. When asphalt rock has been long exposed to the air the surface acquires the appearance of ordinary lime- stone, but on fracturing the specimen the interior will be found ASPHALT EOCK. 375 unchanged. The proportion of bitumen cannot be judged of with certainty from the appearance. The average specific gravity of asphalt rock is about 2*23. It is very hard and sonorous when cold, and may be broken with a hammer. In summer it is softened by blows to a kind of paste, and at 50 to 60 falls to powder. Some rock asphalts, such as that of Lobsann, contain a volatile oil which renders them greasy in character. This oil may be removed by distillation, after which the asphalt is fit for use. Good asphalt rock has a fine and homogeneous grain and no particle of white limestone is visible. The rock is often streaked, while other samples contain crystals of calcite of considerable size, but impregnated with bitumen like the matrix. This is an important characteristic, while bad qualities are imperfectly im- pregnated, or contain so small a proportion of bitumen as to render it difficult to work them. The presence of clay spoils the homo- geneous nature of the asphalt, and causes fissures. When intended to be used for paving, the Val de Travers, Seyssel, and other asphalt-rocks are melted with a certain propor- tion of rich native asphaltum, such as Trinidad pitch, the product being called "mastic." On arrival in England, the mastic is mixed with a further proportion of bitumen, shale oil, and grit. 1 For the determination of the total bituminous matters in asphalt- rock and mixtures containing it, C. K i n g z e 1 1 extracts the air- dried sample with freshly-distilled Kussian oil of turpentine, 1 The following analyses are byM. Durand-Claye : Beflned Bitumen from Bastennes. Seyssel Asphalt Mastic made with Bastennes Bitumen. Imitation Asphalt made with Coal Tar. Moisture, 0-30 015 0-60 Bituminous matter soluble in CS 2 , 69-35 14-05 20-65 Organic matter in- soluble in CS 2 , 4'50 18-45 Alumina and oxide of 2-85 0-85 2-65 iron, Magnesium and cal- cium carbonates, 2-65 80-40 39-60 Silica, 20-35 4-55 18-05 100-00 100-00 100-00 Analyses of various specimens of asphalt paving, and of the materials em- ployed, have been published by C. T. Kingzett (Analyst, viii. 4). 376 ASSAY OF ASPHALT. evaporates the resultant solution, and weighs the residue. The matter insoluble in turpentine is washed with ether, the calcium and magnesium carbonates dissolved by dilute hydrochloric acid, and the washed insoluble siliceous matter weighed. H. P. Cooper prefers carbon disulphide for dissolving out the bituminous matters from asphaltic mixtures. Even when the solvent is used cold, the removal of bitumen from Val de Travers asphalt is so complete that the residual limestone is obtained per- fectly white. 1 The process can also be conveniently conducted by exhausting 20 grammes of the powdered material with carbon disulphide in a Soxhlet's tube. If a correction be made for the moisture driven off from the sample at 100 C., the loss of weight expresses accurately the proportion of bituminous matter. The determination may be advantageously checked by distilling off the carbon disulphide, and weighing the residue after heating it to 100 C. till constant. The bitumen so obtained should be further heated to 220 C., when there will be little further loss if the sample be good, but if much volatile oil ("petroleum") be present the loss will be considerable. The volatile oil is preferably deter- mined by repeatedly digesting the powdered sample with cold alcohol, and weighing the residue. The exhaustion is known to be complete when a portion of the alcoholic washings does not become turbid on dilution with water. ADULTERATIONS OF ASPHALTUM AND ASPHALTIC MIXTURES. Pure asphaltum is much employed in the manufacture of black varnishes and japans, and for other similar purposes. It is not unfrequently mixed with or substituted by coal-tar pitch and other artificial products, which render it quite unfit for some of its most important uses. Asphaltum for varnish-making should be entirely (or with the exception of 4 or 5 per cent, of earthy matters) soluble in carbon disulphide, chloroform, high-boiling coal-tar naphtha, and oil of turpentine. It is also said to be insoluble in alcohol or a mixture 1 The carbon disulphide employed for dissolving the bituminous matter must not contain free sulphur. It may be replaced by chloroform or benzene (coal- tar naphtha). If the residue left after extraction be dark-coloured, foreign organic matters of valueless nature are present. Their proportion may be determined by igniting the weighed residue left after dissolving out the asphal- tum, recarbonating it with ammonium carbonate, again gently igniting and re- weighing. The loss of weight is the amount of non-bituminous organic matter present. In the case of samples leaving a white residue after exhaustion with carbon disulphide, the bituminous matter may be simply and accurately ascer- tained from the loss on ignition, taking care to recarbonate the lime before weighing. ASSAY OF ASPHALT. 377 of equal parts of alcohol and chloroform. It should break with a conchoidal fracture and brilliant resinous lustre, the streak and powder being of a bright brown. Asphaltum should not flow or lose shape like wood-tar pitch when left on a plane surface, and an angular fragment or chip should retain its shape and the sharpness of its angles in boiling water, and only begin to melt at about 150 C. Asphaltum adulterated with coal-tar pitch has a much less brilliant fracture-surface, and an adamantine or metallic rather than a resinous lustre. When fused at as low a temperature as possible, the adulterated asphaltum has a granular pasty appearance and feel, instead of being smooth and homogeneous, and will not draw out into even and transparent brown threads like pure asphaltum. 1 The following figures, due to E. Da vies (Pharm. Jour., [3], xiv. 394), show the behaviour of certain natural asphaltums, asphalt rocks, and their substitutes, with petroleum spirit. 2 The proportions of sulphur and mineral matter are also recorded : Kind of Pitch. Ash. Organic Matter. Proportion Soluble for 100 of Organic Matter. Sulphur. Soluble in P.S. Insoluble in P.S. Per 100 of Asphalt. Per 100 of Organic Matter. Val de Travers asphalt, Fine Syrian asphalt, . Low Syrian asphalt, . Trinidad pitch, . American asphalt, American asphalt, Stearin pitch, Stockholm pitch Rosin pitch, Coal-tar pitch, Coal-tar pitch, Coal-tar pitch, 90-24 68 2-64 37-76 '60 26 5-50 84 58 20 1-06 48 976 48-16 49-68 36-24 none 51-16 47-68 26-00 100-00 48-49 51-02 58-22 41 6-13 5-65 3-47 4-20 6-19 5-80 5-58 65-64 63-62 71-05 91-46 86-94 24-44 1870 15 '"86 3370 36-12 23-45 770 12-48 75-36 8074 83-66 66-03 6378 75-18 92-23 87-45 24-29 18-90 15-94 62 85 04 01 26 69 41 59 1 The characters of asphaltum fitted for varnish-making given in the text are taken from Spon's Encyclopedia. They evidently apply to a product from which the petroleum, or volatile oil, commonly present in raw natural asphaltum has been driven off by heat. 2 Five grammes of the finely-divided sample were digested for one hour with 50 c.c. of petroleum spirit of 070 specific gravity, and the mixture frequently agitated. The liquid is then boiled for a short time, decanted, and the residue boiled with another quantity of 25 c.c. of petroleum spirit. This treatment is repeated eight or ten times, till the exhaustion is complete. 378 ASSAY OF PITCHES. Of these samples, those of American asphalt were evidently' manufactured and not natural products. They were considered to be probably petroleum pitch, and were black brittle substances, having a conchoidal fracture and black streak. They differed from stearin pitch in their brittleness and the proportion of sulphur. The Stockholm pitch was black, too soft to powder, and very easily soluble in petroleum spirit. The rosin pitch had a con- choidal fracture, and gave a brown powder. The different propor- tions of matter soluble in petroleum spirit present in the samples of coal-tar pitch were no doubt due to the extent to which the respective distillations had been carried. The following results have been obtained by A. E. Jordan in the author's laboratory, by the analysis of typical specimens of pitch : Kind of Pitch. Ash. Organic Matter. Organic Matter. Volatile. Non- volatile. Soluble in P.Sp. Insoluble in P.Sp. Percent- age of Organic Mattel- Soluble. Asphalt (origin unknown), Trinidad pitch, . Petroleum pitch, Shale-oil pitch, . Coal-tar pitch, . Bone pitch (inferior), . 60 5-48 8079 76-75 18-61 1777 47-63 74-23 5177 20-29 47-91 78-53 none 25 15 33 50-43 66-40 49-33 56-15 49-57 33-35 50-52 43-52 36-16 63-62 18-56 29-96 63-84 ^36-13 81-29 69-71 36-16 68-77 18-58 30-05 From a general consideration of the figures, it is apparent that while Val de Travers asphalt yields the whole of its organic matter to petroleum spirit, and the other mineral pitches not sensibly less than one-half, the soluble portion of coal-tar pitch does not exceed 25 per cent. 1 The other varieties of manufactured pitch are not produced in sufficiently large amount to make their substitution for mineral pitch for paving a very important consider- ation. The distinction of natural asphalt from coal-tar pitch by means of petroleum spirit may be effected in the following man- ner : 1 gramme of the sample is treated with 5 c.c. of petroleum spirit, and the mixture shaken repeatedly. The liquid is filtered, and 5 or 6 drops of the filtrate diluted to 5 c.c. with petroleum spirit. A greenish fluorescence is always observed in the case of coal-tar pitch, which is absent from solutions of most specimens of 1 Coal-tar pitch is only partially soluble in carbon disulphide, but a larger proportion dissolves than in petroleum spirit. ASSAY OF ASPHALT. 379 mineral asphalt. (A similar fluorescence is observed in solutions of coal-tar pitch in chloroform, turpentine, or glacial acetic acid.) Five c.c. of rectified spirit should then be added, the mixture shaken, and allowed to stand. The upper layer will consist of strongly-coloured petroleum spirit, and the lower of alcohol, which will have a golden-yellow colour if the sample consisted of coal-tar pitch. In the case of mineral asphalt, the alcoholic stratum is often colourless or faintly straw-yellow, but has a somewhat darker yellow tint if much volatile oil be present. An alternative and preferable test, which, like the last, is due to M. D u r a n d-C 1 a y e, is as follows : The sample is digested in carbon disulphide, the solution filtered, the filtrate evaporated to dryness, and the residue heated till it remains hard and brittle after cooling. O'l gramme of the residue is treated with 5 c.c. of fuming sulphuric acid in a stoppered tube, the mixture agitated, and allowed to stand for twenty-four hours; 10 c.c. of water should then be added drop by drop, the liquid being continuously stirred, after which the solution is filtered through paper. If natural bitumen has been operated on, the filtrate will be colour- less, or only faintly coloured, but will have a dark brown colour if coal-tar pitch has been used, mixtures of the two giving inter- mediate tints. If the same conditions are observed in all experi- ments, the depth of colour indicates approximately the proportion of coal-tar pitch present. The comparison should be made by holding the test-tubes up to the light and observing the tints transversely. The samples of pitch, already referred to as having been analysed in the author's laboratory, behaved as follows when examined by the sulphuric acid test just described : Kind of Pitch. Coloration. Asphalt. Faintly coloured. Trinidad pitch. Slight brownish colour. Petroleum pitch. Colourless. Shale-oil pitch. Hair-brown. Coal-tar pitch. Intensely dark brown. Bone pitch. Very dark brown. PETROLEUM AND SHALE PRODUCTS. The parallel products obtained by the distillation of crude petro- leum and the oil or tar from bituminous shale (page 343) present a marked similarity in general character, though differing notably in certain respects. As a rule, the treatment of petroleum, is a much simpler operation than the manufacture of marketable pro- 380 PETROLEUM AND SHALE PEODUCTS. ducts from crude shale oil, but, broadly speaking, the same method of treatment is applied to both of the raw materials. The process employed consists essentially in fractional distilla- tion, and treatment of the separate fractions successively with sulphuric acid and caustic soda, to remove bodies of acid and basic character and to destroy the less stable hydrocarbons. The less volatile portions deposit paraffin wax on cooling. The following table shows in parallel columns the character and quantities of the products obtained in first-class works from crude American petroleum of '800 specific gravity and Scotch shale oil produced at the works of the Broxburn Oil Company. From Petroleum. From Shale Oil. Products. Specific Gravity. Percentage. Spe-ific Gravity. Percentage. Cymogene and flhigolene, 590 to -625 very small very small Gasolene '636 to '657 1/0 to 1/5 "C" Naphtha ("benzine- ) naphtha "), . "B "Naphtha,. 700 714 to -718 10 2-5 V -730 5 " A " Naphtha (" benzine '), 725 to -737 2-0 to 2-5 Kerosene or burning oil, 802 50 to 56 800 to -810 37 Lubricating oil, Paraffin wax, . 875 17-5 2 885 17 13 Coke, gas, and loss, . ... 8 to 10 28 By judicious " cracking," the yield of burning oil from petro- leum may be increased by nearly 20 per cent., at the expense of the heavier products. (See footnote on page 327.) The products from Russian petroleum are very different in both density and percentage from those yielded by the American oil (see pages 368, 402). Rangoon tar of '885 specific gravity gives, on an average, the following proportions of refined pro- ducts : Burning oil (sp. gr. "83 2), 30 per cent. ; lubricating oil (sp. gr. *901), 51 per cent.; and paraffin scale (melting at 51*4 C.), 10-7 per cent. The Abruzzo bitumen is alleged to yield on distillation : Per Cent. Specific Gravity. Flashing Point. C. Burning oil, . Intermediate, Lubricant, 15 33 16| 850 945 (?) 990 (?) 54-5 121-1 157-2 CHARACTERS OF CRUDE PETROLEUMS. 381 The products obtained by the distillation of ozokerite have already been described (page 372). 1 The number of products into which the more volatile portions of shale oil and petroleum are fractionated varies considerably according to the practice of the works, but gasolene and the more volatile products are obtainable from shale oil equally with petro- leum. The only commercial product producible from petroleum having no analogue amongst the products from shale oil is the gelatinous substance known as vaselene (page 385). The more volatile products from petroleum are shortly described on page 385. The similar fractions from shale oil closely resemble the petroleum products in their physical characters, but they con- tain a much larger proportion of o 1 e f i n s, or hydrocarbons of the 1 B. Redwood (Jour. Soc. Arts, xxxiv. 823, 878) gives the following particulars respecting the characters and yields of commercial products of typical samples of petroleum from various localities : Yield of Commercial Products. Locality. Specific Gravity. Naphtha. Burning Oil. Lubricating Oil. per cent. per cent. sp. grav. per cent. 1. Persia, . 777 1-4 87-5 2. Kast India, 821 3-6 62-5 soo 32-0 3. Burmah, mud volcano, Kyouk Phyou, . 818 none 55-7 800 31-3 4. Burmah, native pits, MinVbyin 866 none 15-1 810 65-9 5. Burmah, Western Barangah, . 888 none 7'2 815 89-3 6. Burmah, Eastern Barangah, 835 2-5 66-1 810 27-3 7. Assam, 933 none none 94-2 8. Jndia, 935 n A. naphtha, ) ^Benzine, } 59 to 58 740 to ) 745 j Used as a turpentine-substi- tute, for cleaning printers' types, &c. The term ligroin is sometimes used to indicate a petroleum- product boiling between 70 and 120 C., and having a density between '685 and '690. Shale oil yields a parallel series of products, closely resembling those from petroleum in their leading physical properties, but differing materially in chemical composition, being composed chiefly of olefins instead of paraffins. For general purposes the term gasolene, 1 or mineral The following statement of the densities and applications of the more volatile fractions of American petroleum is taken from an advertisement in a New York trade journal : 63 ( = sp. gr. 725), deodorised naphtha for painters and varnishes ; 68 to 70, deodorised naphtha for manufacturing burning fluid; 74 to 76, deodorised gasoline for printers, druggists' erasive fluid, vapour stoves, and vapour burner lamps ; 74 to 76, redistilled gasoline for street lamps and vapour burners ; 85 to 95 ( = sp. gr. '651 to '622), gasoline for gas machines. 1 Of the products from Russian petroleum, the inappropriate name "gasolene" has hitherto been frequently applied to a liquid of 787 sp. grav., which it is now agreed to call "heavy benzine," "light benzine" being the more volatile fraction of the density 754. All the products from Russian petroleum are denser than the parallel products from the American oil. VOL. II. 2 B 386 PETROLEUM SPIRIT. ether, may be conveniently employed to denote indifferently the fractions of shale and petroleum spirit boiling below 60 C., and having a density below "670, 1 while the heavier portions may be appropriately termed naphtha 2 or mineral spirit. These products may be further differentiated according to their origin in shale oil or petroleum. The employment of the terms " benzoline," t benzine," and " benzin " z - to denote the more volatile fractions obtained on dis- tilling petroleum or shale oil has caused great confusion between the products so called and benzene or benzol, C 6 H 6 , the leading constituent of coal-tar naphtha. This confusion has been increased by the intentional substitution, partial or complete, of one product for the other. Methods for distinguishing petroleum spirit from coal-tar naphtha, and for analysing mixtures of the two are described in the sequel. PETROLEUM SPIRIT consists of a mixture of homologous hydro- carbons of the paraffin series, with smaller quantities of isoparaffins, olefins, &c., and traces of aromatic hydrocarbons. The relative proportions of the several constituents vary according to the boil- ing point and density of the sample, pentane and hexane being the chief constituents of the lighter and more volatile fractions, such as gasolene, while heptane is the leading constituent of the denser kinds, such as commercial benzolene, in which octane and even higher homologues are also present. Petroleum spirit is a thin colourless liquid, having, when re- fined, a peculiar but not unpleasant odour. It gives off inflam- mable vapour at ordinary temperatures, and rapidly evaporates. It is said to absorb oxygen from the air. It is quite insoluble in water, but dissolves in about 6 parts of rectified spirit. Petroleum spirit has considerable solvent properties. The higher kinds especially dissolve caoutchouc, asphalt, and, with less facility, colophony, mastic, and dammar resin. The heavier kind (sp. gr. '745) is said not to dissolve resin. Petroleum spirit dis- solves, in all proportions, the fixed oils of almond, olive, rape, linseed, croton, codliver, palm, cocoanut, theobroma, and lard. It 1 The "benzin" of the United States Pharmacopoeia is the portion of the purified distillate from American petroleum having a density between 670 and '675, and boiling between 50 and 60 C. The "petroleum -benzin" of the German Pharmacopoeia consists of the colourless, non-fluorescent portions of petroleum having a specific gravity of "640 to '670, and distilling almost entirely between 55 and 75. 2 A rule of the New York Produce Exchange defines petroleum naphtha as " water- white and sweet, and of gravity from 68 to 73 Baume" (= 707 to 690 sp. gr. ). ASSAY OF PETROLEUM SPIRIT. 387 does not dissolve castor oil, but the latter liquid dissolves its o\vn volume of petroleum spirit (page 128). Petroleum spirit also dis- solves naphthalene, paraffin, wax, and many similar bodies, and is miscible in all proportions with amyl alcohol, ether, chloroform, benzene, oil of turpentine, creosote, and cresylic acid, but not with carbolic acid. Petroleum spirit is liable to contain certain impurities, which sometimes unfit it for its intended use. If of good quality, when evaporated on the hand it should leave no odour, and when eva- porated in a porcelain basin heated over boiling water no oily residue of heavy hydrocarbons should remain. When boiled for a few minutes with alcohol and a few drops of ammonia, no brown coloration should be produced on subsequently adding nitrate of silver solution. The presence of sulphur-compounds indicated by this test renders the naphtha unfit for use as a turpentine-substitute, as it will be liable to discolour light paints. "When petroleum spirit is agitated with warm water, the water after separation should be perfectly neutral in reaction, and should give no cloud with barium chloride (absence of sulphuric acid and sulphonates). Water cannot exist in notable quantity in petroleum spirit with- out rendering the liquid milky, but if present to an extent sufficient to be thus visible the liquid is rendered unfit for burning in sponge-lamps, &C. 1 The water may be removed by prolonged sub- 1 The remarkable influence produced by insignificant quantities of water and heavy oils on the burning quality of petroleum is indicated by the following results obtained in the author's laboratory. The spirits were sold under the inappropriate name of "gasolene," and were intended for use in the safety lamps employed by colliers. Sample A. burnt well, and was of admittedly satis- factory quality. B. gave a very small flame, which went out entirely in about half an hour. A. B. Appearance, . . Clear. Very milky. Specific gravity at 15 '5 C. , 7038 7015 Distillate below 60 C., 3'0 per cent. 4'1 per cent. 70 17-5 137 80 37-9 43-2 ,, 90 607 56-0 ,, 100 75-3 74-8 ,, Tailings, . . 247 ,, 25 '2 specific gravity, 7150 7272 On further distilling the tailings to 150, A. left a residue equal to 2 '4 per cent, of the sample, of 784 specific gravity ; B. left 3 '2 per cent, of 798 specific gravity. On heating these residues to 100 for some time that from A. entirely volatilised, while B. left a viscid liquid resembling lubricating oil. 388 PETROLEUM AND SHALE NAPHTHAS. sidence, or more rapidly and perfectly by agitating the spirit with. a little dry plaster of Paris. Petroleum Naphtha. Shale Naphtha. Coal-Tar Naphtha. Chemical Compo- Contains at least Contains at least Consists almost sition, . . . 75 per cent, of heptane, C 7 H ]6 , and other 40 to 50 per cent, of h e p - tylene, C 7 H 14 , wholly of b e n- z e n e, C 6 H 6 , and other homo- hydrocarbons of and other hy- logous hydro- the marsh gas drocarbons of carbons. A or paraffin series, the re- the o 1 e f i n series. The re- small percent- age of light hy- mainder appar- mainder paraf- drocarbons in rently olefins, fins, CnH2n+2. some samples. CnH2n ; with No trace of distinct traces benzene or of benzene, its homologues. C 6 H 6 , and its homologues. Specific gravity at 15 C., . . 700 718 876 Chiefly distils be- tween, . . . 65 and 100 C. 65 and 100 C. 80 and 120 C. Sol vent action on Very slight ac- Behaves similarly Readily dissolves coal-tar pitch, tion ; liquid but slightly coloured to petroleum spirit. pitch, forming a deep brown even after pro- solution. longed contact. Behaviour on shaking three measures of the No apparent solu- tion ; the liquids are not miscible, The liquids form a homogeneous mixture, often The liquids form a homogeneous mixture. sample at 20 C. but set to a mass setting to a mass with one mea- of crystals when of crystals at 18 sure of fused cooled slightly to 20 C. crystals of ab- below C. solute carbolic acid, . . . Reaction with Combines with Combines with up- Reacts slowly bromine in the 10 to 20 per wards of 60 per with a consider- cold, . . . cent. of its cent. of its able proportion weight of bro- weight of bro- of bromine. mine. mine. When employed in a vapour-lamp sample A. burnt well, but B. gave a small flame, which in half an hour went out entirely, On treating the plugs of cotton-wool which formed the extremity of the wicks with water, the solution from B. gave a very distinct precipitate with barium chloride, and a little water agitated with the original oil acquired a distinct acid reaction. KEROSENE OIL. 389 SHALE NAPHTHA, which is the lighter and more volatile portion of the oil obtained by the distillation of bituminous shale, is a product very similar to petroleum spirit in most of its properties and uses. The author has found, however, that the shale naphtha presents certain differences, which are due to a much larger pro- portion of olefins, CnH 2n , than exist in petroleum naphtha. The table on the preceding page exhibits these differences in a condensed form, and compares in juxtaposition the characters of a sample of coal-tar naphtha with specimens of similar products from shale and American petroleum. Of course, variation in minor details will be met with in different samples from similar sources. Mineral Burning Oil. Kerosene. 1 Photogene. Under these names, and others more fanciful and less appropriate, are classed the fractions of petroleum and shale oil which are suited for burning with a wick. The petroleum product is often broadly described as "refined petroleum," and that from shale oil as " paraffin oil," but the latter name is often popularly applied to the similar oil from petroleum. Kerosene is a colourless or yellowish oily liquid, often possessing a well-marked blue fluorescence. It has a characteristic taste and smell which it imparts to water, though practically insoluble in that liquid. It is only moderately soluble in alcohol, but is miscible in all proportions with ether, chloroform, benzene, petroleum spirit, volatile oil, and fixed oils with the exception of castor oil. It dissolves phosphorus, sulphur, iodine, camphor, many resins, waxes, fats, and softens india-rubber to a glairy varnish. The commercial varieties of mineral burning oil are very numerous, and hence the physical characters are not very constant. The specific gravity of ordinary American kerosene as at present imported is about *803, the parallel product from shale oil being "800, and from Russian (Baku) petroleum '822. Burning oils of higher densities are also largely manufactured, and are well adapted for special purposes. 2 The American kerosene oil recently imported to England has a distinctly higher specific gravity than was formerly the case. The 1 The name "kerosene" is a contraction of keroselain, or "wax oil," and was originally a trade-mark adopted for a certain patented fraction of coal oil. The term has now been adopted as the most convenient to apply to mineral burning oils generally. 2 The following are the characters and special applications of certain other varieties of mineral burning oils : Colzarine oil: specific gravity about '833 ; fire-test 250 U F. Quite odour- 390 VARIETIES OF KEROSENE OIL. density is an important character, for the heavier oils are generally the more viscous, and hence require a more loosely-woven wick for their satisfactory consumption. The photogene oil from shale resembles refined petroleum in all essential physical respects but, when examined by the bromine process (page 331), the shale product is found to contain a smaller percentage of paraffins and more olefins than is the case with petro- leum. Some samples of shale photogene contain only 5 or 6 per cent, of paraffins. The author has frequently found that when three measures of petroleum kerosene were shaken with one of fused crystals of absolute carbolic acid, the phenol gradually assumed a dark violet, and ultimately a black colour, but the reaction is not invariably produced ; and no such reaction was observed to occur with burning oil from shale. The mixture of petroleum kerosene and phenol becomes turbid at 42-49 C., but the shale oil mixture remains clear till the temperature has fallen to about 25 C. ASSAY OF MINERAL BURNING OIL OR KEROSENE. Good kerosene should be water-white or light yellow, with or without blue fluorescence. A decided yellow often indicates im- perfect purification, or the presence of heavy oils. 1 The odour less, pale amber; specially intended for burning in "moderator" and "carcel lamps." Cazeline oil: specific gravity '805 ; fire- test 144 F. Limpid, with scarcely a trace of colour, and very slight odour. Mineral sperm oil: specific gravity '829 to '847. Abel-flash-point 240 F. ; fire-test about 300 F. Specially adapted for lighthouse and locomotive lights. Its use is compulsory on some of the American railroads, and it is also exten- sively employed on board ship. "Mineral colza oil " and " mineral seal oil " are similar products. Belmontine oil: obtained by distillation of Rangoon tar or Burmese petroleum with superheated steam. Specific gravity '847 ; fire-test 134 F. Though heavy, the oil has but little viscosity, and will rise through a long wick. The flame is very white, and of high illuminating power. Pyronaphtha is a product from Russian petroleum somewhat similar to mineral sperm oil. It has a density of '858 to '869, a fire-test of 265 F., and a flash-point by the Abel-test of 205 to 250 F. (see also page 398). Solar oil is a name commonly applied in Russia to an intermediate oil of about '860 specific gravity, and flashing at about 220 F. by the Abel-test. "Liquid gas," "safety gas," "aurora oil," "astral oil," "beacon oil," ' ' petroline, " "puroline," "septoline," and other fanciful names have also been given to various petroleum and shale products employed for illuminating purposes. In many cases purification is pretended to have been practised with the result of removing the dangerously inflammable constituents. All such products come under the legal definition of "petroleum" (see page 392), and the " flashing point " is a perfectly satisfactory test of their nature. FLASHING POINT OF KEROSENE. 391 should be faint and not disagreeable. When agitated with an equal volume of sulphuric acid of 1*53 specific gravity, the colour ought to become lighter rather than darker. The specific gravity is rarely less than *795, except in certain water-white oils, or ordi- narily above '810 in the case of American, or '823 in the case of Russian oil, but kerosene from different sources, and intended for different special purposes (see footnote on preceding page), varies considerably in this respect, and hence the indication afforded by the density must not be interpreted too strictly. The absence of an objectionable proportion of very volatile constituents or "naphtha," as indicated by the flashing point, and the absence of a large pro- portion of " tailings " or heavy oil, as indicated by fractional dis- tillation, are the most important characters in judging of the quality of a sample of kerosene. 2 Flashing Point of Kerosene Oil. Cold kerosene oil of good quality will not take fire when a light is applied, nor will the supernatant vapour inflame. The temperature at which a sample of petroleum oil commences to give off sensible quantities of in- flammable vapour is technically called its "flashing poin t." Clearly the lower the temperature at which an oil " flashes" the more dangerous its transportation, storage, and use must become. The " flash-point," or temperature of ignition of the vapour, is greatly reduced by a small admixture of naphtha. 3 The " burning point," or temperature at which the oil permanently inflames, is still much used in America as a test of quality. But this is not a reliable test of the safety of an oil, since oils, when spilled, will ignite instantly on approach of a flame, when heated only a degree or two above their flashing point, even although the burning point is considerably higher. 4 Experiment shows that an oil flashing at 86 by the open test, and burning at 107 F., can be made to flash 1 Kerosene often acquires a yellow colour by exposure to light. "When kept in clear glass bottles it becomes ozonised, and the cork becomes bleached. Kerosene so changed will not burn well. 2 The rules of the New York Produce Exchange provide that refined petro- leum or kerosene for contract purposes shall be standard white or better, with a burning test of 110 F. (equivalent to 70 Abel-test) or upwards, and specific gravity not below 44 Baume. 3 Dr B. "W. White found that when a kerosene oil having a flashing point of 113 F. ( = 45 C.) by the open test was mixed with 1 per cent, of naphtha, it flashed at 103 F., with 2 per cent, at 92, with 5 at 83, with 10 at 59, and with 20 at 40 F. On addition of 20 per cent, of naphtha, the oil itself burned at a temperature of 50 F. 4 An oil flashing at 73 F. by the Abel close test, or at 100 F. by the old open test, will generally show about 120 F. by the American " fire-test," or determination of the temperature of permanent ignition. 392 LEGAL DEFINITION OF PETROLEUM. at 100 F. by removing 6 or 7 per cent, by distillation, though such treatment does not improve an oil in other respects. The determination of the flash-point has been very properly adopted by the English Government as the official test for mineral oils, and in a somewhat modified form is also in force in other countries. According to the Petroleum Act of 1871 (34 and 35 Viet. cap. 105), "the term 'petroleum' includes any rock oil, Rangoon oil, Burmah oil, oil made from petroleum, coal, schist, shale, peat, or other bituminous substance, and any products of petroleum or any of the above-mentioned oils ; and the term ' petroleum to which this Act applies' means such of the petroleum so defined, as, when tested in manner set forth in Schedule I. to this Act, gives off an inflammable vapour at a temperature of less than one hundred degrees of Fahrenheit's thermometer." l This definition is expressly intended to exclude the better class of kerosene oil, which does not give off sensible quantities of inflammable vapour (under the conditions prescribed in the schedule) till heated above 100 F. The apparatus to be em- ployed and the mode of conducting the test were set forth in the schedule of the Act ; but as they are happily now merely of historical interest, it is not necessary to detail them. It is suffi- cient to say that, owing to an insufficient description of the mode of performing the operation, and inherent sources of error in the process itself, the results obtained were extremely unsatisfactory. One of the great faults of the apparatus was that the vapour rising from the warm liquid was in no way prevented from diffusing into the surrounding air, and hence the operation of ascertaining the flashing point by this apparatus was known as the " open test." A close test, or process in which the vapour was confined, was adopted in 1879 on the recommendation of Sir F. Abel, and since the end of that year has become the legal form of the test. The apparatus devised for the test is shown in fig. 14, and the following description, abridged from Schedule I. of the Petroleum Amendment Act, 1879, sufficiently indicates the method of using it. The test apparatus is to be placed for use in a position where it is not exposed to currents of air or draughts. The heating apparatus is filled by pouring water into the funnel until it begins to flow out at the spout of the vessel. The temperature of the water at the commencement of the test is to be 130 F. (neither more nor less). 1 Petroleum, within the meaning of the Act, is only allowed to be kept and sold under certain restrictions, which vary to a certain extent according to a discretionary power exercised by the local authorities, any breach of the pro- visions of the Act being punishable by heavy fines. DETERMINATION OF FLASHING POINTS. 393 The test-lamp is prepared for use by fitting it with a piece of flat-plaited candle-wick, and filling it with colza or rape oil up to the lower edge of the opening of the spout or wick tube. The lamp is trimmed so that when lighted it gives a flame of about 0'15 of an inch diameter; and this size of flame, which is represented by the pro- jecting white bead (F) on the cover of the oil-cup, is readily maintained by simple manipulation from time to time with a small /^ wire trimmer. When gas v is available it may be advantageously used in- stead of the little oil lamp, and for this purpose a test- flame arrangement for use with gas may be substi- tuted for the lamp. The water-bath (B) having been raised to the proper temperature (130 F.), the oil to be tested is introduced into the petroleum cup (A) (2 inches high by 2^- in internal diameter, and made of gun metal or brass tinned inside). The oil must be poured in slowly until the level of the liquid just reaches the point of the gauge (c), which is fixed at exactly 1J inches from the bottom of the cup. (In pouring in the oil to be tested great care should be taken not to splash it against the sides of the cup. In warm weather the temperature of the room in which the samples to be tested have been kept should be observed in the first instance, and if it exceeds 65 the samples to be tested should be cooled down to about 60 F.). The lid (D) of the cup, with the slide closed, is then put on, and the cup is placed in the bath or heating vessel. The thermometer (E) in the lid of the cup has been adjusted so as to have its bulb just immersed in the liquid, and its position, which is adjusted to 1 J inches below the centre of the lid, is not under any circumstances to be altered. When the cup has been placed in the proper position, the scale of the thermometer faces the operator. \\ Fig. 14. 394 DETERMINATION OF FLASH-POINTS. The test-lamp is then placed in position upon the lid of the cup, the lead-line or pendulum, which has been fixed in a convenient position in front of the operator, is set in motion, and the rise of the thermometer in the petroleum cup is watched. When the tempera- ture has reached about 66 the operation of testing is to be com- menced, the test-flame being applied once for every rise of one degree in the following manner : The slide is slowly drawn open while a pendulum performs three oscillations, 1 and is closed during the fourth oscillation. In moving the slide so as to uncover the holes, the oscillating lamp (G) is caught by a pin fixed in the slide, and tilted in such a way as to bring the end of the spout just below the surface of the lid. Upon the slide being pushed back so as to cover the holes, the lamp returns to its original position. The temperature at which the vapour of the oil gives a blue flash on applying the test-flame is noted as the flashing point of the sample. To determine the flashing points of burning oils of very low volatility, the air-chamber which surrounds the lamp is filled with cold water to a depth of 1 \ inches, and the heating vessel or water- bath is filled as usual, but with cold water instead of water at 130 F. The heating lamp is then placed under the apparatus, and kept there during the entire operation. If a very heavy oil is being dealt with, the operation may be commenced with water previously heated to 120, instead of with cold water. The results obtained by the above described mode of operating, or " Abel-test," are, on the whole, very satisfactory, as the opera- tion has been freed as much as possible from sources of error due to "personal equation." One peculiarity of the test is that the flashing of the vapour occurs at a temperature much lower than was the case with the old apparatus for the open test. 2 As the result of the numerous comparative experiments made with the two forms of apparatus, the minimum flashing point by the close 1 The pendulum should be 24 inches in length. A properly adjusted metro- nome is a convenient substitute, but the use of some arrangement of the kind is highly desirable, as serious errors have occurred in cases where it has been dispensed with. A clock-work arrangement connecting the slide and pendulum has been legalised in Germany and India. 2 Sir Frederick Abel found, on comparing the results given by 29 samples of oil when tried by the close and open tests, that the flashing point was 23 lower in one case, and from 25 to 29 lower in the remaining 28 cases, by the close test than by the open. At the suggestion of Sir F. Abel Mr Boverton Redwood, the chemist to the Petroleum Association, examined as many as 1000 samples of commercial kerosene (representing 97,766 barrels of oil), and obtained the following comparative results by the old and new methods : INFLUENCE OF ATMOSPHERIC TEMPERATURE. 395 test of the Act of 1879 has been fixed by law at 73 F., which is equal to 22'7 C. The flashing point of a sample of kerosene, as determined by Abel's apparatus, has been found to be sensibly lower in India and the tropics than when the same oil is tested in temperate climates (Jour. Soc. Chem. Ind., i. 471 ; Chem. Neivs, xlix. 196). Thus a sample which under ordinary circumstances flashed at 73 F. had a flash point of 66 when examined in a tropical atmosphere. The difference is due to the fact that at a high atmospheric tem- perature the more volatile hydrocarbons are less readily held in solution in the oil, and the least agitation, such as is involved in pouring the oil into the cup, determines their vaporisation. To obtain concordant results in hot countries Abel and Redwood recommend that the operator should commence to apply the test- flame at a much lower temperature (56 F.) than that prescribed in the Act, which is when the oil in the cup has acquired a temperature of 66 F. This modification causes the removal of the superin- cumbent vapours in quantities too small to flash, by currents of air set up by each application of the gas flame. Even with this modification of the test, a sample which flashes at 73 in England will flash at about 70 F. in India. It is evident that the causes which lead to errors in India will have a tendency to affect the test in temperate countries, and to render the flash-point of the same oil lower in summer than in winter, but this tendency can be Of 968 samples, all of which consisted of the ordinary petroleum oil of commerce, 92 samples showed a difference between the two tests of 25 F. 208 26 225 27 281 28 162 29 Hence, so far, Redwood's results fully corroborated those obtained by Abel. The remaining 32 samples were all specimens of the special product known in the trade as " water-white oil." This brand shows a flashing point by the open test as high as 116 F., and even up to 140 and over, and this slight volatility is accompanied by comparatively low specific gravity. These characters, somewhat unusual in the same oil, are due to the mode of manu- facture adopted, by which a considerable portion of the first and last portions which distil are rejected. Hence the water- white oil is doubtless a mixture of a smaller number of hydrocarbons than is the case with other varieties of kero- sene. "When tried by the close and open tests, the 32 samples of water- white oil showed a difference between the two tests of from 20 to 25 F. As the lowest flashing point by the open test was 118 F., a deduction of the mean difference of 27 would still leave water-white oil with a flashing point far above the ordinary kinds. Hence the smaller difference in the results of the tests, when applied to water-white oil, is of no practical importance. 396 FLASH-POINT APPARATUS. counteracted by bringing the sample to be tested to 56 F. before commencing the operation (Cliem. News, xlix. 196). Changes in barometric pressure also affect the flash-point of kerosene, a fall of 1 inch of the mercury in the barometer lowering the flash-point of an oil by about 2 F. (Redwood). Various other forms of apparatus have been devised for deter- mining the flash-point of mineral oils, and some have met with official adoption. 1 In Germany, a modification of Abel's ap- 1 A valuable comparison of the results yielded by the same oils when examined by different instruments has been made by A. H. Elliott (Second Report of New York State Board of Health] , whose results are condensed in the following table. The oils Nos. 1 and 3 were the best sold in New York city. No. 2 was bought at a small store and had a pale amber colour ; and No. 4 was a mixture of No. 2 oil with petroleum naphtha of '696 specific gravity, to reduce the flashing point. The figures in the table are the flashing points of the oils, expressed in degrees of the Fahrenheit scale : Apparatus. No. 1. No. 2. No. 3. No. 4. OPEN TESTERS Tagliabue's, . Arnaboldi's, ...... 110 118 120 Ill 121 124 119 122 122 97 96 97 CLOSED TESTERS 111 115 112 90 Tagliabue's large, ..... Wisconsin State, ..... English Government (Abel's), . Bernstein's, ...... 117 107 103 130 111 118 109 102 128 107 118 108 102 130 108 93 86 76 90 81 Mann's, ....... Foster's automatic 95 119 96 95 118 75 96 From the figures in the table it appears that it is very important to know what form of instrument has been employed in determining the flash-point of an oil, the closed testers, as a class, not only giving lower results than the open forms, but differing considerably among each other. From the results of his experiments, Elliott concludes that the open testers, whether used for ascertaining the flash-point or the "burning point" of a sample, are entirely untrustworthy for determining the safety of kerosene oil. Of the closed testers, not one of which he considers perfectly satisfactory, he gives the preference to Mann's apparatus, after which he places the Wisconsin State tester. In criticising the Abel apparatus, Dr Elliott points out that when the little oil lamp attached to the cover of the oil-cup of the Abel apparatus is used as a means of ignition, the cover of the oil-cup gets so hot that the hand can only with difficulty endure the heat of it ; and this heat can readily be communicated to the oil down the sides of the oil-cup, and cause a FRACTIONAL DISTILLATION OF KEROSENE. 397 paratus is in use, the minimum flash-point being fixed at 21 C., equal to 69'8 F., and an allowance of 1/62 F. is made for a varia- tion of 1 inch in the barometric pressure. In Russia, the legal flash-point for sale or exportation is 28 C. ( = 82*4 F.). In France and Switzerland the limit is fixed at 35 C. ( = 95 F.), and in Austria and some of the States of the American Union at 37'5 C. ( = 99-5F.). On fractional distillation, mineral burning oils should not give a high percentage below 150 C., and on the other hand should not have a large proportion of " tailings " or heavy oil, distilling above 300 C. By judicious doctoring with a mixture of naphtha and heavy oil, kerosene may be sophisticated without altering the density and without reducing the flash-point so far as to excite suspicion. But such an oil will not prove satisfactory in actual use, as the more volatile portions will be consumed first, the heavy viscous portions remaining to clog the wick. J. Biel (Dingl. Polyt. Jour., cclii. 119) recommends that the fractional distillation of mineral burning oils should be conducted on 250 grammes of the sample, in a glass flask of 500 c.c. capacity. This is wrapped round tightly with thin brass gauze or glass wool, to protect it from too rapid changes of temperature, and is connected by a Glinsky's dephlegmator (vol. i. page 14) with a Liebig's condenser. The thermometer is fixed in the dephlegmator so that the bulb may be on a level with the exit-tube. At the commencement, the flame under the flask should not be larger than is requisite to drive over the light oils, which are collected as long local overheating of the fluid. When a gas jet is used the same trouble is ob- served, but can be overcome by not lighting the jet until the temperature of the oil reaches a point a few degrees below the flash-point ; though even then the heat is communicated with undesirable rapidity through the gun metal attachments on the cover. Elliott suggests that a glass flash jet would eliminate this difficulty. He considers the use of a pendulum unnecessary. Elliott suggests some modifications of the Wisconsin State tester, and the modified apparatus is now the official instrument of New York State. The peculiarity of the instrument consists, in the first place, in the comparatively large size of the oil-cup, which holds about 10 ounces of oil, a condition on which Elliott lays much stress, as more nearly representing the conditions under which the oil is likely to be used. The other peculiarity is that the cover of the oil-cup is of glass, convex upwards. It is furnished with a central hole, fitted with a cork, through which passes the stem of a thermometer, and an opening in the rim through which the flashing jet can be passed. The sub- stitution of a glass for a metal cover enables the operator to note more exactly the point at which the flash occurs. The rate of heating should not exceed 10 F. per minute. 398 FRACTIONAL DISTILLATION OF KEROSENE. as any notable quantity (more than 10 drops per minute) of oil distils at 150. The flame is then enlarged and the "normal petroleum" distilling between 150 and 270 C. is next driven over, the receiver being changed when no appreciable quantity distils when the thermometer is maintained at the latter temperature, Biel weighs the distillates, and ascertains the amount of the residue or " tailings " by noting the difference between the weight of the flask and dephlegmator on the completion of the distillation and again after cleaning. It is evident that the method of measure- ment commonly employed in practical examinations of volatile oils is equally available. 1 The following results obtained by Biel by the above process are interesting as showing the behaviour of typical samples of Russian oils : * Kerosene. Pyronaphtha. A. B. C. D. E. Specific gravity, Flash-point; C., . 820 52-5 820 35-0 835 44-5 857 7'5 867 94-0 Light oils (below 150), . Normal oils (150 to 270), Heavy oils (tailings), 0-8% 92-0% 7'2% 10-0% 76-5% 13-5% 6-0% 63-5% 30'5% 0-0% 44'5% 55'5% 0-0% 30-5% 69-5% Biel has also placed on record the following figures obtained by the distillation of certain burning oils 2 in a glass retort with a thermometer immersed in the oil, which is probably quite as good a plan for the particular purpose : American. Baku. No. 1. No. 2. No.l. No. 2. Original oil ; spec, gravity, ,, flash-point ;/C., 795 26 783 48 803 26 822 30 Light oils (below 150), . Normal oil (150 to 270), Heavy oils (tailings), 14-4% 45'9/ 397% 2-2% 87'8% 10-0% 33'5/ 66-5% 12-8% 78'3% 8-4% 1 For the abstract of a valuable paper on the assay of kerosene by fractional distillation, see W. Thb'rner, Jour. Soc. Chem. Ind., v. 371. 2 No. 1 American oil was a sample of ''Standard oil" manufactured by the Imperial Refining Company of Oil City. An equal volume of concentrated FRACTIONAL DISTILLATION OF KEROSENE. 399 "No. 1 American oil was of decidedly inferior quality, and had probably been produced by "cracking" the heavy residue from which the normal burning had been partially removed. It must not, however, be assumed that all oils produced by cracking are of the same unequal character. As already stated, Russian kerosene is usually of distinctly higher density than the parallel product from American petroleum. Russian petroleum gives much the smaller yield of burning oil, but the product is very homogeneous, the various hydrocarbons com- posing it not differing very widely in specific gravity, boiling point, and other characteristics. This peculiarity is well shown by the following figures obtained by B. Redwood (Jour. Soc. Chem. Ind., iv. 76) by fractionally distilling samples of kerosene made from Baku and American petroleum. A measured quantity of the liquid was distilled, and the density of each fraction of 10 per cent, was observed : Russian Kerosene. American Kerosene. Spec. Grav. Spec. Grav. Kerosene oil. '822 '803 1st fraction 783 748 2nd 796 759 3rd 4th 5th 6th 7th 8th 9th 10th 803 778 814 792 827 '802 831 -812 837 '822 838 -831 846 -838 (residue) '864 '849 It is evident that in the case of the Russian kerosene there is less difference between the specific gravity of the lightest and heaviest fractions than in the case of the American kerosene. A practical test of the burning qualities of kerosene oils by actually consuming them in similar lamps and noting the rates of consumption and the comparative intensities of the light yielded, is often capable of giving valuable information. Much depends on the character of the wick used, all oils burning far more satis- factorily and safely with an American wick, of long staple cotton sulphuric acid was coloured blackish-brown when shaken with the oil. The distillation was attended with a copious evolution of sulphurous acid, and the distillate between 190 and 230 was strongly impregnated with it. No. 2 was an "Astral oil" of the Pratt Manufacturing Company. It gave a golden- yellow coloration when shaken with an equal measure of strong sulphuric acid. The distillation was normal throughout, and the process was not attended with the formation of sulphurous acid. 400 COLOUR OF KEROSENE OIL. loosely woven, than with the comparatively hard, tightly-woven wick commonly employed in this country (B. Kedwoocl). 1 Kero- senes containing a large proportion of light oils give a better light, but burn faster than others, while the presence of heavy oils retards the consumption and seriously diminishes the light yielded. Care must be taken not to form too hasty an opinion on the oils tested, as a kerosene containing excess of both light and heavy oils, or in technical parlance consisting largely of " mixed tops and bottoms," will often give a good light at first, but after burning some time the flame will greatly diminish in size and luminosity, and in extreme cases the wick may become so clogged and charred as to cause actual extinction of the flame. Russian kerosene does not give so much light as the American oil, but on the other hand there is considerably less diminution in the light as the level of the oil in the reservoir of the lamp falls. The colour of kerosene is a character to which attention should be paid. Frequently, it is sufficient to compare the colour of the sample with that of a standard specimen, the two oils being con- tained in bottles of the same size. A preferable plan is one proposed by B. Redwood. He places the oils to be compared in two glass cylinders, such as are used for measuring water, and holds these above a mirror in such a position that the images of the bottoms of the cylinders are presented side by side. In this way it is easy to make an accurate comparison of the reflected discs, which are, of course, tinted in proportion to the colour of the liquids. With a fluorescent liquid like kerosene, Redwood finds this plan preferable to looking down on the oils while the cylinders are placed on a white surface. A chromometer devised by R. P. Wilson, 2 in which the kerosene is compared with discs of coloured glass of standard tints, has been adopted by the Petroleum 1 B. Redwood, to whom the author is indebted for a perusal and revision of the entire article on petroleum products, has proposed to test the quality of kerosene by burning it under constant conditions in a lamp placed in front of a camera. The glass or paper screen into which the image of the flame is focussed is divided into a number of squares, so that the size of the image is readily measured, and the outline may be traced on paper for permanent reference. The capillarity of wicks he compares by noting the weight of oil drawn over in a certain time when the wicks are employed as syphons. 2 The glass discs for Wilson's chromometer are issued by the Petroleum Association of London (85, Gracechurch Street), and the instruments are all precisely alike in construction, so that the testing of the colour of petroleum, wherever these chromometers are used, is placed on a uniform basis. In a German form of the instrument devised by Stammer, the column of oil can be adjusted in length until its colour is identical with that of the standard, by which means results of considerable precision are obtainable. SULPHUR IN KEROSENE. 401 Association and is now in use both in Europe and America (Jour. Soc, Chem. Ind., iv. 76). 1 In some cases a diminution of light may be due to the presence of excess of sulphur-compounds, owing to imperfect refining of the oil. Specimens containing a large proportion of olefins, as those resulting from cracking, are especially liable to contain sulphonates. Sulphur compounds may be recognised by the test described on page 205, and in the footnote on page 363. The quantity can be best ascertained by collecting the products of the combustion of the oil in a Referees' gas-testing apparatus, and converting the sulphur acids into barium sulphate. Occasionally oil is met with containing sulphonates in such quantity as to cause a condensation of sulphuric acid on the chimney when the oil is burnt. Kedwood has found 119 grains of sulphur per gallon in Canadian kerosene. The products of combustion injured the plants in a greenhouse. Mineral Lubricating Oil. The products classed under the above title are obtained chiefly from two sources, namely, the less volatile fluid portions of petro- leum, and the less volatile fluid portions of the oil produced by the distillation of bituminous shale. In the case of petroleum the lubricating oil has not always undergone distillation, but is ob- tained from the residues by treatment with charcoal and other puri- fj r ing agents. Such oils, often called "natural oils," or "reduced oils," are preferable as lubricants to those which have undergone distillation. The lubricating oil obtained from either American petroleum or shale has essentially the same chemical composition. It consists largely of the higher members of the o 1 e f i n series of hydrocar- bons, C n H2n, with, in the case of the shale product, small amounts of polymerised acetylenes, and possibly also terpenes. Small proportions of solid paraffins are often present in solution, but liquid paraffins exist in much smaller proportions than in the lighter fractions of petroleum and shale oil. A considerably larger proportion of paraffins is usually found in lubricating oil from petroleum than in that derived from shale. 2 The hydrocarbons of the lubricating oil from Eussian petroleum are not wholly under- 1 The following grades of colour are recognised in the trade : water white, superfine white, prime white, standard white, and good merchantable. The rules of the New York Produce Exchange provide that kerosene or refined petro- leum for contract purposes shall be standard white (straw-coloured) or better, with a burning test of 110 F. or upwards, and a density not below 45 B. 2 According to E. J. Mills, "the normal paraffins are unsuitable for use as lubricants ; the lubricating properties belong to one or more series of iso- paraffins." VOL. II. 2 C 402 MINERAL LUBRICATING OILS. stood, but higher members of the series peculiar to Caucasian petroleum (page 365) are probably present in large amount. Mineral lubricating oils are called by various fancy names, such as " oleonaphtha,'' " valvoline," " vulcan oil," " globe oil," &C. 1 In colour they range from pale yellow through all shades of red, brown, green, and blue, to black. The better qualities have very little taste and no marked smell either at the ordinary temperature or when heated. Some samples develop a peculiar and characteristic smell on gently heating, and have a disagreeable burning taste. Mineral lubricating oils have a density ranging from '850 to '925, the most usual gravities falling between '880 and *910. They boil at a very high temperature. Mineral lubricating oils are not optically active, but they usually exhibit a strongly marked blue or green fluorescence, a character which plays an important part in their detection when mixed with fat oils. The method of applying the test is described on page 8 1 . The fluorescence or "bloom" of mineral lubricating oil may sometimes be destroyed by exposure to light, but more rapidly and certainly by subjecting it to a process of limited oxidation by treatment with nitric acid. Turmeric, nitro-naphthalene, and picric acid also obscure the fluorescence. Oil thus treated regains its fluorescence by treatment with an equal measure of strong sul- phuric acid. There are, however, varieties of mineral lubricating oil wholly non-fluorescent, and in which the character cannot be developed by any known treatment. These oils, if derived from shale, usually deposit solid paraffin on cooling to about 8 C. They distil without decomposition, are unaffected by alkalies, and behave in the ordinary manner with sulphuric acid. 1 "Ragosine oil" is not a fanciful trade-name, but the name of an oil manu- factured by V. I. Ragosine & Company. The following are stated by this firm to be the quantities and specific gravities of the chief products obtained from 100 gallons of Russian petroleum of '826 specific gravity : Products. Specific Gravity. Gallons. "Benzine," 725 1 "Gasolene" or heavy benzine, . . 775 3 Kerosene, '822 27 Pyronaphtha (flash-point 270 F., open test), '858 12 Lubricating oil, '890--905 27 Cylinder oil, '915 5 Vaselene (not a direct product), . . '925 1 Residuum and loss, . 100 The heavier lubricating oils or " oleonaphthas " of the Ragosine Company range in density from '905 to '920, and have remarkably low freezing points. ASSAY OF MINERAL LUBRICATING OILS. 403 Mineral lubricating oil is not acted on by alkali, a fact on which is founded the process of detecting and estimating it when mixed with fat oils (see page 83). When treated with bromine, mineral lubricating oils form brom- ides in which the proportion of bromine is of some value in form- ing an opinion as to the origin and constitution of an oil (see page 334). EXAMINATION OF MINERAL LUBRICATING OILS. In determining the general character of hydrocarbon lubricating oils, as also their suitability for special purposes, the properties to be taken into account are the same as those which are important in the case of lubricating oils of animal or vegetable origin. 1 These have already been described (page 192 et seq.), .but the following additional characters are of service : a. Colour is of little importance except for the fine kinds of oil. A well-marked fluorescenceis an ordinary characteristic of mineral lubricating oils, but is in no respect a test of quality. Turbidity may be due to aqueous fluid in suspension, in which case the oil usually froths on heating, or it may be caused by the presence of solid hydrocarbons which dissolve on warming the oil. Other solid matters may be separated by diluting the oil with ether or petroleum spirit, filtering, washing the residue with ether, drying it gently, and weighing. b. The smell should by preference be very slight, even on warming. A marked odour indicates an imperfectly refined oil, or the presence of objectionable volatile compounds which will reduce the flash-point of the oil and increase its waste in use. c. The specific gravity of mineral lubricating oil may vary within wide limits. As a rule, the greater the density of an oil the higher will be its flash-point and viscosity ; but there are many exceptions to this rule. Lubricating oils .from Eussian petroleum have a higher viscosity than the products of similar density from American petroleum and shale oil (see page 196). In the case of oils completely fluid at the ordinary temperature, the specific gravity may be determined by any of the usual methods. The density of the thicker and semi-solid oils is best ascertained by filling a specific gravity bottle to the brim with the warm oil. When it has cooled to a temperature of 60 F. 1 It has already been pointed out (page 203) that the tendency of an oil to act on metals is closely related to the proportion of acid which is present or may be formed in it, and hence observations of the action of oils on different metals have little interest or meaning apart from the particular samples examined. This fact appears to have been lost sight of 'in an otherwise inter- esting paper by I. J. Redwood (Jour. Soc. Chem. 2nd., v. 362). 404 FLASH-POINT OF LUBRICATING OIL. (=15 '5 C.) the stopper is inserted, and worked to and fro until it is forced home, the excess of oil gradually escaping through the perforation in the stopper, when the bottle may be wiped and weighed. d. On exposure to cold a mineral lubricating oil should not become solid, but should assume the consistency of a jelly or oint- ment, and the temperature at which it undergoes this change should not be inconsistent with the conditions under which it is to be used. The test is commonly applied by slowly cooling a sample of the oil in a tube about If inch in diameter, and noting the temperature at which the oil no longer flows on inclining the tube, or that at which separation of solid paraffin commences. The absence of notable proportions of solid hydrocarbons enables the lubricating oil from Baku petroleum to bear exposure to a very low temperature ( 20 F. in some cases) without becoming solidified or even depositing any paraffin. This peculiarity may be employed to distinguish Russian from American products. e. The flash-point (page 391) of a lubricating oil should be fairly high. A low flash-point indicates the presence of volatile constituents which will produce an odour, cause waste, and may possibly be dangerous. A high flash-point is often rigidly insisted on in the case of oils to be used in cotton mills or engine-cylinders. The flashing points of the pale Scotch oils from shale range from 130 to 180 C. ( = 266 to 356 F.), and of the darker oils and greases from 180 to 230 ( = 356 to 414 F.). These oils usually become viscous about C. The pale oils from American petroleum manufactured by the Thompson and Bedford Company flash from 166 to 230 C. ( = 330 to 414 F.), the density ranging from '885 to '920. The black oils flash at temperatures ranging from 180 to 204 C. ( = 340 to 400 F.), according as the melting point varies from 10 to 1 C. (=15 to 30 F.). The flash-point of lubricating oils is best observed by the Abel-apparatus, but the water-bath must be removed and the intermediate air-bath filled with olive oil or melted paraffin wax. The apparatus is then heated on a sand-bath, and the flash-point of the oil observed in the usual way. Some operators remove the air-bath also and immerse the oil-chamber itself in a sand-bath, but such a mode of operating is liable to cause unequal heating. It is not unusual to test the flashing point of lubricating oils by the old or open test, instead of by the closed or Abel-test. The results by the open test are always higher than those by the closed test, but there is not the simple relationship between the figures obtained which is observed when kerosene oil is tested. /. On heatinga mineral lubricating oil in a platinum capsule TESTING OF LUBRICATING OILS. 405 it should volatilise without the production of any very pungent odour ; and if the vapours be allowed to ignite and the flame be then blown out, no smell of resin or acrolein (from fixed oils) should be observable. Spindle oil should not lose more than 5 per cent, of its weight when absorbed by filter-paper and exposed to 140 F. (=60 C.) for twelve hours. (See also page 202.) g. On ignition, a mineral lubricating oil should leave no inorganic residue, or merely an insignificant trace (less than 0*05 per cent.). Certain oils, which have been treated with soda, leave a very sensible quantity of ash of marked alkaline reaction to litmus. The same result would be obtained if the oil contained a soap of an alkali-metal, but soap is neutral to an alcoholic solution of phenol-phthalein (page 266). The more usual addition, however, is that of palmitate or oleate of aluminium (page 242), which is added to lubricating oils to increase the viscosity. It often separates from the mineral oil after a time, especially in contact with water. If such oil be heated it foams violently. Aluminium oleate can be definitely detected as indicated on page 206. h. The oil should be agitated in a test-tube with an equal measure of boiling water, and the tube then kept in the water-oven till separation occurs. The formation of a granular white layer at the junction of the two liquids indicates the presence of resin. If the liquid assume a milky-white appearance the oil has been insufficiently washed after the final treatment with soda. Alkali is often purposely left in an oil l with the view of increasing its "body" or viscosity. Such oil is very prone to oxidise, and becomes turbid on exposure to air from absorption of moisture. It is also liable to change in colour. If a mineral oil be boiled in a large excess of water for three or four hours the oil will be practically unaltered in colour if of first-rate quality. i. If the oil be agitated with an equal measure of caustic soda solution of 1*36 specific gravity, and the tube kept at about 55 C. till the liquids have separated, a precipitation of tarry matter indicates that the oil has previously been insufficiently treated with soda, and hence is liable to deteriorate in colour. A first-rate oil gives no trace of tarry matter when submitted to this test. The forma- tion of a white emulsion with the alkali is due to an admixture of some fatty oil, fatty acid, or resin. A diminution in the bulk of the oil indicates the presence of plienolo'id bodies, which may be determined by a quantitative application of the test. k. Fatty oils may be detected and determined with considerable i This is effected by blowing air through the imperfectly- washed oil. As the moisture is got rid of the oil takes up the soda, while remaining perfectly transparent. 406 BEHAVIOUR OF MINERAL OILS WITH ACIDS. accuracy by saponifying the oil and extracting the aqueous solution of the soap with ether, as described on page 82. I. When mineral lubricating oil is agitated with an equal measure of sulphuric acid of 1'53 specific gravity, it will remain unchanged or acquire simply a yellow tint if of good quality, but if the sample be imperfectly refined, or if coal-tar oil be present, more or less browning will ensue. On treatment with concen- trated sulphuric acid, in the manner described on page 53, lubri- cating oils from shale and petroleum at first develop a trifling degree of heat (3 to 4 C.), though on continued stirring a very decided increase of temperature is sometimes observed. Rosin oil usually causes a rapid rise of 18 to 22 C., and with coal-tar oil the action is still more marked. Fatty oils rarely give a less rise than 40 C. m. If 10 c.c. of the oil be mixed with an equal measure of fuming nitric acid of 1*45 specific gravity, but little rise of temperature will occur with good mineral or shale lubricating oil, but great heat is produced by coal-tar oil. Kosin oil mixes quietly with the acid, and then suddenly evolves much heat. The unacknowledged addition of rosin oil to shale or petroleum lubricating oil is often suspected, but the practice is probably less common than is supposed. Methods for detecting the adulteration are described under " Rosin Oil." Vaselene. 1 Petroleum Jelly. Soft Paraffin. Vaselene consists of those portions of petroleum which are soft or pasty at ordinary temperatures. It is taken from petroleum or ozokerite stills after the greater part of the oil has volatilised. 2 The crystallisable paraffin is more or less removed, and the residue purified without distillation, treatment with sulphuric acid and superheated steam and filtration through animal charcoal being the usual methods employed. (See Jour. Soc. Chem. Ind., i. 97 ; and Pharm. Jour., [3], xiii. 123.) Yaselene is now extensively used as a lubricant, and to protect iron and steel goods from rust. In pharmacy, it has proved a valu- able basis for ointments. Vaselene varies somewhat in its physical characters according to its origin and quality. It is ordinarily a colourless or pale yellow, translucent, fluorescent semi-solid. The commoner kinds used for 1 " Vaseline" was originally the proprietary name of an article patented by the Chesebrough Manufacturing Company, but, like kerosene, the name has been extensively applied to other products of the class, and, with the altera- tion of the spelling the writer has ventured to make, may be advantageously adopted for soft paraffin or gelatinous petroleum generally. 2 Shale oil does not yield any sensible quantity of a product having the characters of vaselene. CHARACTERS OF VASELENE. 407 lubricating have a dark greenish or brownish colour. Vaselene is quite free from taste and smell. Under the microscope, crystals are sometimes visible, and become more numerous on application of cold. The commercial varieties of vaselene may be classed under two heads : (1) those which, like the product from American petroleum, are obtained as a ready-formed mixture of hydrocarbons of gela- tinous consistence ; and (2) those made by directly mixing solid paraffin of low melting point with heavy lubricating oil. The latter kind are less homogeneous and are liable to deposit crystals of paraffin on keeping, and hence are not so suited for the preparation of ointments as the true American vaselene. Vaselene usually melts between 40 and 50 C. 1 At the boiling point of water, compared with water at 15 '5 C., the density of vaselene ranges between "803 and '85 5, 2 figures which present a striking contrast to those representing the density of paraffin wax and ozokerite under the same circumstances ('748 to '757). Vaselene consists chiefly of a mixture of hydrocarbons of the paraffin series, the iso-paraffins from C 16 H 34 to C 20 H 42 being apparently the most prominent constituents. Vaselene, however, contains in addition a notable proportion of olefins, the bromine-absorption ranging from 1 to 12 per cent. 2 Vaselene is insoluble in water. Cold alcohol of 98 per cent, dissolves 2 '2 per cent, of German vaselene, and in hot alcohol vaselene dissolves completely to form a clear solution, from which the hydrocarbon separates in flakes on cooling. 1 According to the British Pharmacopoeia, "paraffinum molle" has a melting point of 95 F. ( = 35 C.), but, as pointed out by C. Umney (Pharm. Jour., [3], xvi. 413), only one such article is met with in commerce, the usual range in this country being from 104 to 119 F. This practically agrees with the description of the article in the United States Pharmacopoeia, which gives the melting point as between 104 and 125 F. 2 The following figures show the density and bromine-absorption of samples of vaselene and allied products examined in the author's laboratory. The density determinations at 99 C. were made with a plummet and Westphal's balance, as described on page 16, and the bromine-absorptions as on page 331 : Specific Gravity. Bromine-absorption. Description. Solid ; at 15-6 C. Melted; at 99 C. Total. Br. as HBr. White pomade vaseline (Chesebrough Co.), Yellow vaselene (maker unknown), . . 856 870 8036 8140 11-3 1-1 1-8 o-o Yellow vaselene (maker unknown), . . . 873 8172 7-2 1-1 White pomade ozokerine (J. C. or olefins, C n H 2n . There are not wanting firm upholders of the latter view, but the researches of Gill and Meusel seem to have definitely proved the former to be correct. These chemists found that when excess of paraffin wax was heated with bromine in sunlight, for some time, half the bromine was converted into hydrobromic acid. This reaction is characteristic of paraffins, the olefins combining at once with bromine without forming hydrobromic acid. Thus : Paraffins, . C n H 2n+2 + Br 2 = C n H 2R+1 Br + HBr; an( j Olefins, . C n H 2n +Br 2 = C n H 2n Br 2 . Paraffin wax, or, more shortly, paraffin, is, when pure, a white or bluish-white waxy solid, without taste or smell. Its density and melting point vary with its composition, and the same is true of its boiling point, which is very high. Exposure to continued heat, aided by pressure, resolves paraffin wax into liquid hydrocar- 410 DENSITY OF PARAFFIN WAX. bons (page 327), and the same result is partially obtained by dis- tillation. By merely raising the temperature to 370 C. the paraffin undergoes decomposition, with separation of carbon and formation of permanent gas, liquid products, and a paraffin of lower melting- point. The specific gravity of paraffin wax increases with its melting point, as is shown by the following results attained by Galletly from Boghead coal products : Sp. Gravities. Melting Points. 8236 8480 8520 9090 9110 9243 9248 9400 G. Beilby (Jour. Chem. Soc., xliii. 388) has given the follow- ing data respecting the specific gravity of a sample of shale oil paraffin melting at 38 C. (= 104'4 F.) : Sp. Gravity. 8740 7950 7956 32-0 C 89'6 F 39-0 , 102-2 40-5 , 104-9 53-3 , 128-0 53'3 , 128-0 58-0 , 136-4 59-0 , 138-2 80'0 , 176-0 In the solid state, at 21 C., Dissolved in '885 paraffin oil, at 21 C., In the melted state (calculated to 21 C.), From this it appears that paraffin in solution has practically the same density as when in the molten state. 2 The data in the table on the following page, obtained in the author's laboratory, show the relations between the solidifying point of paraffin w r ax and its density in the solid and liquid state. 3 From these figures it appears that, except in the case of the refined ozokerite, there is a regular increase in the density with a rise in the melting point, as was observed by Galletly. There is a striking contrast between the densities of the waxes in the molten state at 99 and the densities of the same samples when solid, the 1 These temperatures are correctly quoted. 2 This result is comparable with that of the writer, who found that spirit of camphor has a volume equal to the sum of the volumes of the camphor and alcohol used in preparing it. 3 The determinations of the density of the solid samples were in most cases made as described on page 184, but, on repetition, the figures obtained were not very concordant. The density at 99 was determined by the plummet (page 16), and the solidify ing point was ascertained by method d, page 23. CHARACTERS OF PARAFFIN. 411 Specific Gravity. Origin of Sample. Solidifying Point ; C. Solid, at 15-5 C. Liquid, at 99 C. 1 Shale oil, . 8666 7481 44-0 2. Shale oil, . 8961 7494 47-0 3. Shale oil, . 9000 7517 52-0 4. Shale oil, . 9111 7572 58-5 5. American petroleum, 9083 7535 53-8 6. Ozokerite, . 7531 61-5 7. Rangoon tar, 8831 7571 49-0 range in the latter case being, for the shale-products, five times as great as in the former. In other words, the density of paraffin wax is far more constant when melted than in the solid state. It also appears that paraffin wax is much less dense in the melted state than the oil from which it crystallises on cooling, a sample of which had a specific gravity of '843 at 99. Yaselene also is considerably denser than paraffin wax (see page 407). Paraffin melting from 32 to 43 C. exhibits a well-defined crystalline fracture, from 43 to 50 C. the crystals become much smaller and less marked, and from 50 C. upwards the fracture is very close and fine in the grain. On the other hand, paraffin melting at 65 C. presents, on fracture, brilliant, white, acicular crystals having a silky lustre. Paraffin melting at 77 C. closely resembles bleached beeswax, but the fracture is not conchoidal. When paraffin is kept for some time under gentle pressure, the temperature being somewhat below its melting point, a molecular change occurs and the substance becomes transparent. A sudden change of temperature or a sharp blow or knock causes this vitreous paraffin to return to its original state, but it may be annealed by slow cooling. Paraffin becomes plastic at a temperature considerably below its melting point, a fact which is disadvantageous when it is employed for making candles, but which is to a great extent obviated by a small admixture of stearic acid, wax, or other foreign body. Mixtures of paraffins of different fusing points melt at a tem- perature which is the mean of the melting points of the constituent hydrocarbons ; but the products obtained by melting together paraffin wax and stearic or palmitic acid, beeswax, &c., always have a melting point lower than the mean of those of their con- stituents. 1 1 This is well shown by the following table from Vincent's Manufacturing Chemistry, the results recorded being obtained from mixtures of the Mussel- 412 CHARACTERS OF PARAFFIN WAX. When two pieces of paraffin are sharply struck together a metallic ring is heard, the sound being sharper the higher the melting point of the paraffin. Paraffin wax is completely insoluble both in hot and cold water. It is insoluble in rectified spirit, and but sparingly soluble in boil- ing absolute alcohol, the dissolved portion separating again on cool- ing. It dissolves readily in ether, and is very soluble in petroleum spirit, shale naphtha, kerosene, and benzene. Paraffin dissolves readily in essential oils in the cold and in warm fixed oils, and does not again separate from the latter on cooling. Hence it is miscible with all kinds of vegetable and animal oils and fats. It differs from these in its indifference to alkalies, and hence cannot be saponified. If, however, the soap be made from a mixture containing carnaiiba wax as well as paraffin the latter is completely dissolved by the alkali, a fact which is said to be attributable to its solubility in the myricyl alcohol, C 30 H 61 .OH, which is a constituent of the carnaiiba wax. Paraffin wax burns when kindled with a very bright but not smoky flame, and hence is much employed for making candles and tapers. 1 When paraffin wax is boiled with concentrated nitric acid it is burgh Company's stearic acid, melting at 130 F. , with various proportions of three varieties of Young's paraffin : Percentage of Stearic Acid. Percentage of Paraffin Melting Point of Mixture. Paraffin melting at 120 F. 126F. 127 F. 55 45 114 1134 1154 60 40 119 116 118 65 35 121 118 120 70 30 122J 1224 122 75 25 1244 124 124 80 20 125J 125| 125| 85 15 126 127 127 90 10 1274 128 1294 95 5 128A 129 130 1 Paraffin candles usually contain from 5 to 15 per cent of stearic acid. The presence of the admixture may be detected by adding a little powdered fuchsine to the sample and keeping it at 100 C. for some time. If pure, the melted paraffin will remain uncoloured, but with 2 per cent, of stearic acid a pink colour is produced, and if as mush as 5 per cent, be present the whole mass becomes crimson. Coloured candles are made by dissolving the fuchsine or other colouring matter in stearic acid or beeswax, and adding the product to the paraffin till the desired tint is obtained. PAKAFFIN SCALE. 413 oxidised, with formation of various products, of which the most characteristic are succinic acid, C 4 H 6 5 , and c e r o t i c acid, C 27 H 54 0. 2 , the production of the latter of which points to the presence of the hydrocarbon C 27 H 56 in the original paraffin. 1 P o u c h e t has described a yellowish combustible light solid which he obtained by similar means. He found it to melt between 45 and 47 C., and to be crystalline and slightly soluble in alcohol. It has been named paraffinic acid, and from the analysis of its lead, silver, and barium salts the formula C 24 H 48 2 has been assigned to it. The action of nitric acid on paraffin occurs the more readily the higher the melting point of the sample, the variety obtainable from ozokerite melting at 80 C. being very easily acted on. Paraffin is also violently oxidised by permanganate of potassium mixed with sulphuric acid and heated. Concentrated sulphuric acid will attack paraffin at high temperatures, and the more readily the higher the melting point of the hydrocarbon. When heated with sulphur, paraffin is decomposed, with evolu- tion of nearly pure sulphuretted hydrogen and separation of carbon. Other chemical characteristics of paraffin, and methods for separating it from hydrocarbons of other series are given on page 328 et seq. In all their chemical relationships ozokerite and c e r a s i n resemble paraffin wax, of which indeed they are simply varieties. For the quantitative analysis of mixtures of paraffin wax with fatty acids or gtycerides, the process described on page 82 is suit- able. The detection and determination of paraffin in beeswax can be effected as described on pages 186 and 188. PARAFFIN SCALE. Crude Paraffin. " Scale '' is the technical name for the crude paraffin wax de- posited by cooling the oils holding it in solution. The lower the temperature employed for refrigeration, the lower the melting point of the paraffin deposited. The assay of crude paraffin scale is limited to determinations of the water, insoluble matter, and oil, and to observations of the melting point of the scale before and after expression of the oil. To determine the proportion of water, 1 grammes of the sample should be melted rapidly and treated with 50 c.c. of light petro- leum spirit. The solution obtained is kept warm until the water has thoroughly settled. If the water be present in quantity, it may be tapped off into a graduated tube and estimated by measure. The insoluble matter may be separated by filtration or simple de- 1 Cerotic acid was also the chief product obtained by Gill and Meusel by the oxidation of a paraffin, melting at 56 C., by means of chromic acid mixture. 414 ASSAY OF PARAFFIN SCALE, cantation. If the water be present in proportion too small to admit of its being readily measured, it may be determined by agitating the solution of the scale in petroleum spirit with a known weight of gently ignited plaster of Paris. This may be filtered off, washed with petroleum spirit, dried at a gentle heat, and again weighed. The increase of weight gives the water taken up. Of course, in employing this method the petroleum spirit used for the solution and washing must be previously dehydrated by agitation with plaster. The water in crude American scale ranges from a trace up to about 2 per cent., being usually below 1 per cent. The water may also be determined \)y heating the sample to 105 110 C., and stirring with a thermometer (see footnote, page 142). For the determination of the oil in paraffin scale, K. T e r v e t recommends that 30 grammes of the finely-powdered sample should be folded up in a piece of closely-woven cloth about 12 inches square, so that the scale may form a cake 3 inches square. The parcel is placed between 40 folds of blotting paper, 20 on each side, and the whole put between iron plates and subjected to a moderate pressure in a vice for one or two hours, when the pres- sure should be increased to 10 or 12 cwt. per square inch, and maintained at this for twelve hours. The parcel is then removed, the pressed scale detached from the cloth and weighed. The loss from the original weight taken is the oil, soft paraffin, and a portion of the ivater. The residual water and insoluble matter are determined in an aliquot part of the pressed cake in the same way as in the original sample, and the sum of their weights deducted from that of the pressed cake gives the corrected weight of the latter. 1 The proportion of oil is usually between 0*5 and 2'0 per cent. What is technically known in England as the melting point of paraffin scale is in reality the solidifying point, and can be ascer- tained in a very satisfactory manner by method d, page 23. In 1 Boverton Redwood (Jour. Soc. Chem. Ind. , iii. 430) has devised a special machine for testing paraffin scale, and the greater part of that imported from America is sold on the results of the assay by Redwood's test. The apparatus consists of a press furnished with a gauge for indicating the pres- sure applied, and a convenient form is made by J. H. Ladd & Co., of 116 Queen Victoria Street. The test is, of course, a purely arbitrary one, depend- ing upon (a) temperature, (&) amount of pressure applied, (c) length of time during which the pressure is continued, and (d) quantity of scale operated upon in relation to the diameterof the press-cake. The operation is conducted at 60 F. , which temperature must be closely adhered to. The quantity of scale operated upon is 500 grains, and the pressure is applied for five minutes. The gauge of the press indicates from 1 to 10 tons, and the working pressure is 9 tons on the whole surface of the press cake of 5| inches diameter, equal to about 7 cwt. per square inch. The sample is placed between two circular pieces of PETROLEUM RESIDUES. 415 the Scotch paraffin works the melting point of scale is sometimes observed by method a, page 21. With readily fusible scale the bulb of a thermometer is thoroughly cooled and placed in the half- solid scale. By this means a film of solid scale is formed on the bulb. On removing the thermometer and exposing it to the warm air of a room, the film of paraffin melts, when the point at which the thermometer stands is at once observed. 1 Petroleum Residues. In some works the distillation of petroleum is carried to actual coking, and in others so far as to produce a kind of pitch. In other cases the process is stopped at an earlier stage, and the " petroleum residue" obtained is separately treated. Besides paraffins and olefins, the residues from American petroleum contain notable quantities of close-chain hydrocarbons, among which anthracene, phenanthrene, chrysene, chrysogene, and pyrene have been recognised, as also a hydrocarbon called thallene. From the residue from Calif ornian petroleum the hydrocarbon p i c e n e, C 22 H 14 , has been isolated. When treated with strong sulphuric acid it yields a sulphonic acid, which dis- solves in water with fine blue-green fluorescence. For the assay of petroleum residues a method may be used similar to that employed for the examination of crude shale oil filter cloth in a turned iron cup into which the ram of the press fits, and a sufficient number of circular pieces of filtering paper are placed above and beneath the cloth to absorb the expressed oil. The press cake is carefully removed from the cloth at the expiration of five minutes, and the loss in weight noted. The proportion of oil in American scale usually ranges between 1 and 12 per cent Much depends upon the proper drawing and averaging of the samples of scale. A good plan is to sample one cask in twenty by taking out a core with a sampling iron driven into the centre of the cask, 'and then mix the sample by passing it through a small hand sausage-machine. 1 In America the paraffin scale is melted over a water-bath in a hemispherical tinned iron or glass dish, 3 or 4 inches in diameter. The dish is then placed on a stand where slow cooling can take place, in a room at a temperature of about 60 F., and a thermometer, with a spherical bulb half an inch in diameter, is suspended over the centre of the dish so that seven-eighths of the bulb is immersed in the paraffin. The surface of the melted scale is then carefully watched, and the temperature noted at which a " spider " extends from the edge of the liquid to the bulb of the thermometer. The " spider " or network makes its appearance before there is any uniform film over the surface, and is not readily observable unless the observer be suitably placed in relation to the source of light. Mr B. Redwood, to whose published papers and private communications the author is indebted for much valuable informa- tion on the subject of petroleum-products, states that the results of the American test are from 2g to 3 F. higher than those obtained by the English test. 416 CLASSIFICATION OF TERPENES, ETC. (page 345). That is, 500 c.c. should be distilled, the distillate washed with acid and soda, and the purified product again distilled, when it will yield burning oil, heavy oil containing paraffin, and "grease" which should be separately cooled and pressed. The oil separated from the scale is again treated with acid and soda, when it forms finished lubricating oil. A sample of residue examined by R. Tervet yielded : burning oil, 5 '5 ; lubricating oil, 50'6 ; and paraffin scale, 5'8 per cent. Petroleum residues often contain a considerable proportion of water, which cannot be separated by simply heating the substance. The residue should be treated with a large excess of petroleum spirit and the water allowed to settle out, any gritty matter being separated by filtration. TERPENES AND THEIR ALLIES. There exist ready-formed in the vegetable kingdom a number of closely-allied hydrocarbons, which constitute many of the so-called " essential oils." These hydrocarbons are often described gener- ically as "terpenes"; but it is recognised that the true- terpenes form only a sub-class related to the allied hydrocarbons in a very peculiar manner. Thus, the different hydrocarbons in question do not seem to be homologues of the ordinary kind, but rather to have the constitution of polymers of isoprene or other hydrocarbons isomeric therewith. The following arrangement indicates the relationship existing between the terpenes and allied hydrocarbons :* I. PENTINES or HEMITERPENES, C 5 H 8 ; as isoprene, valeryl- ene. II. DIPENTINES or TRUE TERPENES, (C 5 H 8 ) 2 = (C 10 H 16 ), sub- divided into five classes, thus : a. Pinenes, as t e r e- benthene, from oil of turpentine ; b. Citrenes, as h e s- peridene from oil of orange-peel ; c. Sylvestrene, from Russian turpentine oil ; d. Terpilene or Di-isoprene, from terpene hydrochlorides, &c. ; and e. Camphenes, which are solid at the ordinary temperature. 1 J. H. Gladstone (Jour. Chem. Soc., xlix. 622), in a very recent paper, has pointed out that the refraction and dispersion equivalents of the terpenes and their allies exhibit considerable differences. Thus : Refraction -equivalent. Dispersion-equivalent. Isoprene, .... 40 '3 3 '2 Terpenes, .... 73 '0 4'0 Citrenes, .... 75 '0 4 '5 Caoutchene, . . . . 75 '3 5'0 Campheires, .... 71 "9 37 Cedreues, . . . .109-8 61 ISOPRENE. 417 III. TRIPENTINES or CEDRENES, (C 5 H 8 ) 3 = C 16 H 94 ; as cedrene, from oil of cloves. IV. POLYPENTINES (C 5 H 8 ) n ; as colophene, C 20 H 3 2) and caout- chouc, (C 5 H 8 ) n . A great number of natural hydrocarbons of Groups II. and III. are known, and even those which are apparently chemically identical often present marked differences in certain of their physical char- acters. There is little doubt, however, that many of the terpenes and allied hydrocarbons which have been assumed to be distinct have been far from pure, and it is probable that further research will prove that many which have been hitherto regarded as iso- meric are really identical. Pentines or Hemiterpenes, C 5 H 8 . Eight bodies of the composition C 5 H 8 can theoretically exist, assuming that the formulae are all open chains. Three of these, namely, p r o p y 1- acetylene, isopropy 1-a c e t y 1 e n e, and methyl-ethyl- acetylene, are true homologues of acetylene (page 335), form- ing metallic derivatives with cuprous and argentic solutions. Valerylene, boiling at 41-42, prepared by the action of alcoholic potash on amylene dibromide, is probably a dimethyl-allene, from the facility with which it is converted into the k e t o n e, C 5 H 10 0, by digestion with mercuric bromide and water. Piperyl- ene, also boiling at 42, differs from valerylene in forming a crystalline tetrabromide. Another pentine is contained in the liquid deposited from oil-gas on compression. ISOPRENE, which is the most interesting of the hemiterpenes, has probably the constitution of a /3-methyl-crotonylene, CH 2 : (C.CH 3 ).CH : CH 2 , and hence belongs to Group III. of the acetylene series (page 335). It is obtained, together with other products, by the dry distillation of caoutchouc and gutta-percha. It is a volatile liquid, boiling, according to Tilden, at about 35 C. It is not affected by treatment with mercuric bromide and water. By careful management, Tilden obtained from isoprene a t e t r a- b r o m i d e, C 5 H 8 Br 4 , as a yellowish oily liquid remaining fluid at 18 C., but which was decomposed on distillation. When isoprene is heated to about 280 C. for some hours it polymerises into a terpene, C 10 H 16 , together with colophene, CgoH^. 1 Isoprene behaves similarly with sulphuric acid, yielding a terpene and a fluorescent colophene. By dilute chromic acid mixture 1 The terpene boils at 174 to 176 C., and appears to be identical with terpilene, the optically inactive hydrocarbon obtained from turpentine. It yields the same dihydrochloride, and by the action of dilute acid may be converted into a terpin, C 10 H 22 0., crystallising in the same form as the terpin from ordinary turpentine. VOL. II. 2 D 418 TERPENES. isoprene is oxidised to carbonic, formic, and acetic acids. "With nitric acid it yields a considerable quantity of oxalic acid. On exposure to the air, isoprene absorbs oxygen and becomes converted into a white syrupy substance, which on distillation is suddenly converted, often with explosive violence, into a white amorphous mass of the composition C 10 H 16 0. Another character- istic reaction of isoprene is that of being converted into true caoutchouc or india-rubber when brought into contact with certain chemical agents, such as strong hydrochloric acid or nitrosyl chloride. 1 Dipentines. C 10 H 16 = (C 5 H 8 ) 2 . The hydrocarbons of this class exist for the most part ready formed in the essential oils of plants, but terpenes have been pro- duced synthetically. Thus they are obtainable by the dehydrolysis of the oxygenated bodies of the composition C 10 H 18 contained in various natural essential oils. Isoprene, C 5 H 8 , readily polymerises, with formation of a terpene. An optically inactive hydrocarbon of the formula C 10 H 16 , having most of the characteristic properties of the natural terpenes, has been obtained by the action of alcoholic potash on d i b r o m- rutylene, C 10 H 18 Br. Another terpene has been synthetically obtained from amylene (Her., xviii. 838). With the exception of the different varieties of oil of turpentine, the terpenes have been but imperfectly studied. As a class they are colourless or yellowish liquids, usually having a marked power of rotating the plane of vibration of a ray of polarised light, the rotation being in some cases to the right and in others to the left. The terpenes are usually volatile without decomposition, and may all be distilled unchanged in a vacuum or with the vapour of water. The terpenes are practically insoluble in water, but readily soluble in alcohol, ether, chloroform, benzene, petroleum spirit, and the fixed and volatile oils. The general characters of the terpenes are well indicated by those of terebenthene, the best-known member of the class (see page 421). The table on the following page is an epitome of the principal distinctive characters of such of the isomeric terpenes as are liquid at ordinary temperatures. 2 1 As pointed out by W. A. Tilde n (Chem. News, xlvi. 120)"this reaction of isoprene would have considerable practical interest if isoprene were obtain- able from some other and more accessible source. 2 The table in the text is constructed chiefly from the classification of the terpenes in the second edition of Watts' Manual of Chemistry, edited by W. A. Tilden. CHARACTERS OF TERPENES. 419 a. PlNENES. b. CITKKNES. c, SYLVESTRENE. d. TERPILENB or Di-isoprene. Sp. gravity; at 0, About '876. About -860. ,, at 15 to 20 C., 865 to -880. 846 to -853. 860. 852. Optical activity, . + or - . Usually +. SD=+19'5. Inactive. Boiling point ; C., 156-160. 174-176. 173-176. 176-178. Action of acidulated Form crystalline Do not usually yield tn Slowly converted alcohol, . . . terpin hydrate a terpin. into terpin. Hydro- j Mon -> chlorides, jp. Crystalline: m. p. 124. Crystalline; m. p. No crystalline com- pound. Identical with pin- No crystalline com- pound. Crystalline ; m. p. No crystalline com- pound. Identical with pin- Tetrabromide, . . 50. Liquid. ene compound. Crystalline; m. p. 72-73. Liquid. ene compound. Crystalline; m. p. 104-105. 125. Nitrosyl-derivative, Crystalline ; m. p. Crystalline ; m. p. No definite com- No definite com- 129. 71. pound. pound. Chief source or American and Oils of orange-peel, Russian and Swedish Action of heat or mode of forma- French turpen- lemon, lime, and turpentine oils sulphuric acid on tion, tine oils, and oil bergamot (Au- (Conifer IK). turpentine oil, of juniper (C, ,, old,. . . 955 8-0 -10-0 cloves 1-060 lO'O - x Clear greenish. ,, copaiba, .... 920 0-3 - 0-35 Blue. Deep violet-red. coriander, . . . 880 5-0 -lO'O Colourless. Gradually reddish brown. cubebs, .... 945 ... Colourless to blue. Deep violet-red to cherry-red. 920 0-05- O'l ,, dill, . . 880 3-5 - 5-0 Colourless. After Brownish to cherry 24 hours, brown. red. ,, eucalyptus, . . . 900 ,, fennel, 990 o-8- 1-1 Colourless. After- Brownish to violet- 24 hours, currant brown. red. ,, juniper berries, 850 Colourless to green- Deep cherry-red. blue. ,, lavender, .... 890 2-0 - 2-5 Yellowish to Brownish red ; greenish. darkens. old,. . . 888 10-0 - x ... ,. lemon, 870 0-2 - 0-4 ,, mace, 895 0-6 - 0-9 Colourless. After- Brownish to red- wards brown- brown. violet. marjoram, . . . 901 1-5 - 2-5 Colourless to Brown-red to deep green-brown. cherry red. ,, neroli, 870 2-5 - 3-3 ,, orange, sweet, . . 850 0-3 - 0-5 Yellow. '.'.'. ,, ,, bitter, . . 876 0-35- 0-5 Yellow. ,, parsley 950 1-0 - 1-3 ... ,, peppermint, . . . 915 1-2 - 1-9 ,, verv old, 925 5-0 - 6-5 ... ,, rose, 860 0-4 - 1-2 ,, rosemary, French, 894 2'5 - 2'8 Colourless to clear Red-brown to deep greenish. cherry red. ,, Italian,. 904 4-0 - 5-0 ,, rue, 890 4-0 - 5-0 , savin, . 898 0'5 - 0'7 sage 920 1'5 - 1'8 ,, santal, .... 980 4-0 - 5-0 Violet-brown to dark blue. ,, thyme, 895 1-0 - 1-4 Clear yellowish, Brownish red, then turning violet. cherry-red. ,, turpentine, . . . 890 ... Colourless. Yellow-brown. ,, verbena, .... 895-9-863 ,, winter- green, . , 1-158 7-0 '-10-0 Orange. Greenish - yellow, turning brown- red. wormseed, Levant, 920 10-0 - x Orange to gam- Deep red-brown to boge-yellow. deepcherry-ied. ,, wormwood (absinth), 965 3-5 - 5-0 ,, (chenopod), 960 8-0 -10-0 ... ... 436 REACTIONS OF ESSENTIAL OILS. Concentrated sulphuric acid (2 or 3 drops to 1 of oil) assumes with most essential oils a yellow colour, turning brown, and frequently passing finally to a fine red. Oils of cardamoms, cloves, fennel, anise, cajeput, and laurel produce a violet coloration, and oil of cinnamon a green coloration changing to blue at the edges. Addition of ferric chloride gives further characteristic colorations. Fuming nitric acid (5 drops to 1 of oil) gives specially characteristic colorations with oils of mace and nutmeg (blood-red), cubebs (green), copaiba (bluish-violet), gaultheria (cherry-red), cinnamon (carmine), myrrh (reddish-violet), pimento (blood-red), and pennyroyal (violet). Solid iodine added to essential oils produces somewhat vary- ing effects, oils consisting chiefly of terpenes giving a very energetic reaction, accompanied by evolution of light and heat, while with other oils nothing of the kind is observable. With a few exceptions, the individual essential oils are not of sufficient general importance to require separate description. Among the exceptions, however, is the oil of turpentine, described in the following article, while the oils of winter-green, bitter almonds, mustard, &c., are considered in other parts of the work. Oil Of Turpentine, Spirit of Turpentine. French Essence de Terebenthine. German Terpentinbl. Oil of turpentine is contained in the wood, bark, leaves, and other parts of pines, firs, and other coniferous trees, and is usually prepared by distilling, either with water or alone, the crude tur- pentine or oleo-resinous juice which exudes from incisions in the bark of the trees. The non-volatile portion constitutes rosin or colophony (page 458), and the distillate, varying in yield from 10 to 25 per cent., is the volatile oil or spirit of turpentine, vulgarly known as " turps." Rectified oil of turpentine is obtained by treating the first product with alkali, to saturate any rosin acids, and redistilling. The principal varieties of oil of turpentine met with in commerce are the French, English or American, and Russian. Though pre- senting close resemblances these varieties are not strictly identical, as will be evident from the following description : French turpentine oil is now comparatively rarely met with in England. It is manufactured chiefly from the crude turpentine or " gum " yielded by the Pinus maritima, but smaller quantities are obtained from the pin franc or frankincense pine. Of late years, the distillation has been conducted by blowing superheated steam into the still containing the gum, no external heat being em- ployed. To this improved mode of manufacture the very constant COMMERCIAL OIL OF TURPENTINE. 437 character of the product is probably due. French oil of turpentine consists chiefly of a pinene, C 10 H 16 , called terebenthene, which has already been fully described (page 421). Smaller pro- portions of other terpenes, of cymene, and of resinous matters are also present in the commercial oil. English or American turpentine oil is obtained from the turpen- tine collected in Carolina and other Southern States of the American Union, from the swamp pine (Pinus australis) and the loblolly pine (P. tseda). Its main constituent is a pinene called australene or au s tra-t e rebenthene, having the same boiling point, specific gravity, and chemical characters as the tere- benthene of the French oil, but differing from that body in being dezfro-rotatory instead of exerting a Isevo-rotatory action on a ray of polarised light. With this exception, and the fact that French oil absorbs oxygen somewhat less rapidly than the American pro- duct, the two oils are practically identical, and hence the following description applies equally to both. American oil of turpentine has a density varying from *864 to *870. It begins to boil at a temperature between 156 and 160 C., and fully passes over below 170. Old samples leave a small proportion of non- volatile resinous matter. Oil of turpentine is readily combustible, and burns with a very smoky flame. Oil of turpentine is almost wholly insoluble in water, glycerin, and dilute alkaline and acid solutions. It is very soluble in absolute alcohol, but its solubility is greatly lessened by the pre- sence of water, spirit of 0'85 specific gravity dissolving only 10 per cent, of its weight of oil of turpentine. Oil of turpentine is very soluble in (probably miscible in all proportions with) ether, carbon disulphide, chloroform, benzene, petroleum spirit, and fixed and essential oils. Oil of turpentine is itself a solvent for sulphur, phosphorus, resins, fats, waxes, caoutchouc, &c. Turpentine oil absorbs oxygen on exposure to air, gradually becoming thick and ultimately resinous. C. T. Kingzett has shown that the oxidation is accompanied with the formation of a body of the formula C 10 H 14 4 , which he regards as camphoric peroxide. This substance, by the action of water, is converted into hydrogen peroxide and camphoric acid. The disinfectant known as "Sanitas" is produced by passing air through Kussian oil of turpentine in contact with warm water. Russian oil of turpentine was till recently of but little commercial importance, though its use is now increasing. It is not well suited for making paint or varnish, owing both to its persistent odour and the great readiness with which it absorbs oxygen and becomes viscid, 438 COMMERCIAL OIL OF TURPENTINE. whence its application for the manufacture of sanitas. Its vapour is said to excite violent headache. The Russian turpentine of commerce is chiefly the product of Pinus sylvestris, but P. ledebourii and other species also contribute to it. A sample of Russian turpentine oil, of '8682 specific gravity, examined by Til den, was found to contain : (1) from 10 to 15 per cent, of a p i n e n e boiling at about the same temperature as australene, but having the specific rotation of +23*5; (2) from 65 to 70 per cent, of a peculiar terpene called sylvestrene, having a characteristic odour and the characters described on page 419; (3) a considerable quantity of c y m e n e ; and (4) small proportions of viscid hydro- carbons boiling at high temperatures. But Russian oil of turpen- tine is very variable in character, the normal constituents being accompanied with more or less of the products of the destructive distillation both of the rosin and the wood, including benzenoid hydrocarbons, phenoloid bodies, furfurane and sylvane, &c. The specific gravity of the Russian oil of commerce varies from 8620 to *8722, and it contains matters not volatile at 100 C., in proportions ranging from 0'5 to 2*4 grammes per 100 c.c. The variations met with in the chief commercial varieties of oil of turpentine are indicated in the table below, showing the Source. Specific Rotation. Number of Samples. Authority. FRENCH Pure terebenthene, Commercial oil, . ?j -40-4 -30-0 to -30-5 -25-3 W. A. Tilden. H. E. Armstrong. C. Symes. AMERICAN Pure australene, . Oil shipped at Wilming- ton, Oil shipped at Savannah, ,, Charleston, 1 + 21-5 + 12-3 to +16-3 + 8'8 to +12-0 + 9-5 to +167 35 12 9 W. A. Tilden. H. E. Armstrong. * j RUSSIAN Pure sylvestrene, . Commercial oil, . + 19-6 + 15-0 to +23-4 + 15-0 to +22-2 23 67 W. A. Tilden. H. E. Armstrong. C. T. Kingzett. 1 The oil shipped from Charleston comprises turpentine of somewhat high dextro-rotatory power, as well as oil of the Wilmington and Savannah types. Other American ports furnish a somewhat irregular product ; but the values always lie between the extremes given in the table, and in the majority of cases the oils belong to the Wilmington type, Brunswick alone exhibiting a ADULTERANTS OF TURPENTINE OIL. 439 range observed in the specific rotatory power for the sodium ray of the oils from different sources. 1 ADULTERATIONS OF TURPENTINE OIL. Although the optical activity of commercial oil of turpen- tine is so variable, it still furnishes a valuable means of distin- guishing real turpentine oil from its substitutes and adulterants, all of which are optically inactive (see page 442). The most usual adulterants of oil of turpentine are certain frac- tions of petroleum known as "turpentine substitute," and "rosin, spirit," the more volatile portion of the product obtained by dis- tilling ordinary rosin. Certain fractions of shale oil and coal tar are not improbable adulterants, but their employment is not com- mon. The following table gives a number of distinctions between real turpentine oil and its substitutes : - Turpentine Oil. Rosin Spirit. Petroleum Naphtha. Shale Naphtha. Coal tar Solvent Naphtha. 1. Optical activity, . active usually none none none none 2. Specific gravity, . 860 to '872 856 to '880 700 to -740 700 to -75:> 860 to -875 3. Temperature of dis- tillation ; C., . 156 to 180 Gradual rise. Gradual rise. Gradual rise. Gradual rise. 4. Action in the cold Readily dis- Readily dis- Veiy slight Very slight Readily dis- on coal-tar pitch, solves pitch solves pitch action (see action (see solves pitch to a deep- to a deep- page 388). page 388). to a deep- brown solu- brown solu- brown solu- tion. tion. tion. 5. Behaviour with ab- Homogeneous Homogeneous No apparent Homogeneous Homogeneous solute phenol at mixture. mixture. solution. mixture crys- mixture. 20 C. (see page tallising on 388), . cooling. 6. Behaviour on agi- Homogeneous Homogeneous Liquid separ- Behaves like ... tating 3 measures mixture. mixture. ates into two petroleum of the cold sample layers of naphtha. with 1 measure of nearly equal castor oil, volume. 7. Bromine absorption, dry (page 331), . 203 to 236 184 to 203 10 to 20 60 to 80 ... 8. Behaviour with sul- Almost com- Polymerised. Very little Considerable Moderate phuric acid, . pletely poly- action. action. action. merised. marked tendency to furnish a product of the Savannah type. (H. E. Arm- strong, Jour. Soc. Chem. Ind., i. 478.) By submitting American oil of turpentine to fractional distillation, Arm- strong obtained a portion having a specific rotation of +24 '8, and by submit- ting the original oil to air-oxidation and subsequently distilling off the un- altered hydrocarbon in a current of steam he several times obtained products of considerably higher rotatory power than the original oils. Similarly, the hydro- carbons carried over by the air-current during the oxidation of Russian turpen- tine oil are almost free from sylvestrene, and usually exhibit a higher rotatory power than the original crude turpentine from which they are derived. 1 Instruments intended for observing the angular rotation for the transition- tint are not suitable for examining the optical activity of oil of turpentine. It will be noted that the rotations of the commercial oils of turpentine differ considerably from those of the terpenes said to form their chief constituents. 440 ASSAY OF TURPENTINE OIL. The specific gravity is alone sufficient to indicate the presence of any considerable proportion of some of the above adulterants of turpentine oil, but it is not of much value for quantitative purposes, owing to the variable character of the shale and petroleum pro- ducts. In fact, heavier fractions of shale oil and petroleum are apt to be added to turpentine oil, although their presence is still more objectionable than the naphthas. According to H. E. Armstrong, a good indication of the presence and amount of such adulterants is obtainable by distillation with steam. For this purpose a current of open steam, generated by boiling water in a large flask or tin can, is caused to bubble through a definite quantity of the oil contained in a flask or retort fitted to a condenser. Unless it has been freely exposed to the air for some time genuine turpentine oil leaves a mere trace of non-volatile matter, but old samples may leave a small proportion (0*5 to 2'0 per cent.) of resinous matter, which solidifies on cooling. As a rule, if more than 0'4 per cent, of non-volatile residue is left after steam-distillation it consists of unvolatilised petroleum oil. This is recognisable by its low density ("800 to '850, colophene being '940), and more or less marked blue fluorescence when dis- solved in ether. The residue from genuine old turpentine oil is readily oxidised and dissolved by dilute nitric acid, while the petroleum product is more or less nitrofied without altering much in volume. Rosin oil would be recognisable by the formation of a bulky grease on trituration with a little slaked lime. The oil which distils over in a current of steam will consist of the genuine oil of turpentine, together with the more volatile portions of any adulterants, and the presence of any shale or petroleum naphtha will be indicated by the low specific gravity of the oily portion of the distillate after separation from the water which condensed with it. B. Redwood has pointed out that the presence of petroleum naphtha in turpentine oil is readily and certainly indicated by the reduced flash-point of the sample. Thus, while genuine American turpentine oil flashes at 92 F., the addition of only 1 per cent, of ordinary petroleum spirit lowers the flash-point by about 10 F. The presence of the more volatile fractions of shale oil and petro- leum will also be indicated with certainty by the distinctive tests given in the table. The reactions with coal-tar pitch and carbolic acid are not reliable in the case of mixtures of turpentine oil with adulterants. Petroleum and shale naphthas and rosin spirit com- mence to distil at very varying temperatures according to their quality, but during the distillation the thermometer rises regularly through a considerable range. On the other hand, genuine American EXAMINATION OF TUKPENTINE OIL. 441 oil of turpentine commences to boil at 156 C., or only a few degrees above that temperature, and passes over almost completely below 180 . 1 This is a most useful mode of examining turpentine. For the approximate determination of petroleum naphtha in turpentine oil, and its isolation therefrom, H. E. Armstrong (Jour. Soc. Chem. Ind., i. 480) recommends the following process, which depends on the ready and nearly complete polymerisation of oil of turpentine by sulphuric acid, and the comparative indiffer- ence to such treatment of the paraffins which form the greater part of petroleum spirit : 500 c.c. of the sample of turpentine is placed in a separator and treated with 120 to 170 c.c. of a mix- ture of two measures of strong sulphuric acid with one measure of water (2 : 1). The mixture is cautiously agitated, and if much rise of temperature is observed the separator must be placed in cold water for a short time. The turpentine is gradually converted into a viscid oil, and when this has taken place, and no more heat is developed on repeated agitation, the acid is tapped off. The oily layer is then transferred to a flask and subjected to steam- distillation in the manner already mentioned. When all that is volatile in a current of steam has passed over, the oily portion of the distillate is separated from the aqueous layer, and treated with half its volume of sulphuric acid previously diluted with one- fourth of its measure of water (4 : 1). The mixture is well agitated as before, the acid liquid separated, and the oily layer again distilled with steam. When genuine turpentine oil has been operated upon, the volatile product of this second treatment consists merely of c y m e n e and a small quantity of a p a r a f- fino'iid hydrocarbon, (C 10 H 20 ). It never exceeds 4 or 5 per cent, of the measure of the original sample, and with care is as low as 3 per cent. If the volume notably exceeds 5 per cent, it is advisable, as a precaution, to repeat the treatment with 4 : 1 acid. When treated in the foregoing manner, petroleum naphtha is not materially affected, and hence the proportion present may be de- duced approximately by making an allowance of 4 or 5 per cent, from the volume of volatile oil which has survived the repeated treatment with sulphuric acid. A further purification may be effected by violently agitating the surviving oil with several times its volume of concentrated sulphuric acid (or, preferably, slightly fuming sulphuric acid) heated to 50 or 60. This treatment can be repeated, if thought desirable, after which the residual hydro- carbon is separated, steam-distilled, and again measured, when the 1 A good sample of rectified American oil will give 90 to 93 per cent, of dis- tillate below 165, the greater part of which will pass over between 158 and 160 C. Russian oil distils chiefly between 170 and 180 C. 442 ROSIN SPIRIT IN TURPENTINE. surviving oil from pure turpentine oil will not exceed 0*5 to 1*0 per cent, by measure of the original sample. Any excess over this proportion represents the minimum admixture of petroleum naphtha present. Shale naphtha suffers considerably by the foregoing treatment with acid, and cannot be satisfactorily determined by the process. Its proportion is best deduced from the results of a bromine-titra- tion ; but the estimation obtainable in this way is only approximate. Evidence of the presence of rosin spirit is also afforded by the increased yield of hydrocarbons on treatment with 4 : 1 and con- centrated sulphuric acid, as rosin spirit also yields a cymene and paraffinoid hydrocarbon on treatment with 4 : 1 acid. The cymene from rosin spirit being isomeric with that from turpentine, proof of the presence of rosin spirit might possibly be obtained by examin- ing the cymene produced. The use of rosin spirit as an adulterant of turpentine oil is ex- tending, and small proportions of the admixture are difficult to detect. The odour suffices to indicate the presence of an inferior spirit, but is useless if the refined article has been employed. The behaviour on distillation varies, but the temperature rises regularly throughout the process, and no considerable fraction is obtained at a constant temperature of 158-160, as in the case of American turpentine oil. Very often there is a notable residue of viscid oil left on steam-distillation. The bromine-absorption of rosin spirit is somewhat lower than that of turpentine oil, but the difference is not sufficiently marked or constant to serve as a distinction. According to Armstrong, rosin spirit is never optically active unless actual resin be present, but the author has some reason to doubt the uniform accuracy of this proposition ; and in any case the rotation of commercial oil of turpentine is too variable to allow of the optical activity being employed for the estimation of the proportion of rosin spirit present. Camphors. Stearoptenes. Many natural essential oils contain oxidised principles which are solid at ordinary temperatures, and are deposited from the oils on cooling or standing. They are usually colourless crystallisable bodies, often optically active, volatile without decomposition, in- soluble or nearly so in water, but readily soluble in alcohol and most other organic solvents. They often have a pungent aromatic taste, characteristic of their origin. Some of these stearoptenes or camphors are phenols (e.g., thymol), while others are apparently oxidised ter penes. The following are the principal bodies of the class : CAMPHORS OR STEAROPTENES. 443 Remarks. See page 444. S fo'lss "* <* 13 ^ &o.a to, 02 " G ft' 5 g> C'go.S I 1 ls* See page 447. Yields acetic and anisic acids with chromic acid mixture. Blue colora- tion with ferric chloride. Forms piper onic acid by limited oxidation. See page 450. 1 ^ oo w S e 2*> ! II II : : 1 O ^ a a CO J/2 d iL" CO . 1 S S Q O 1.. ~:4 111 S3 w j c8 s .- o _o :~oS .^ O ^ t3 f? 1* s-a 1-aS ^ "3 'o'ftS 13 . 'S gg 1 til > M 6 s 5 sS >> n A 02 1 w e^ S A do \? ww V 77' y o ^ M w W* w" a 1 S ^ - 1 V 1 s Si 4 1 1 ^0 A " tti o* W II II 6" II c? o v v II II II f ' f- _-^ \ 2 S o^ c^ uT o 00 f| | o ^ o* o o 444 MENTHOL. MENTHOL. Menthyl Alcohol. C 10 H 20 = C 10 H 19 .OH. (See also page 443.) This camphor occurs, together with a terpene, in oil of pepper- mint, and separates in crystals on cooling the oil. 1 It forms com- pound ethers by reaction with acids, is converted by treatment with phosphoric pentachloride or hydrochloric acid into m e n t h y 1 chloride, C 10 H 19 C1, and by distillation with zinc chloride or phosphoric anhydride into liquid menthene, C 10 H ]8 , boiling at 163. The menthol from American oil of peppermint (derived from Mentha piperita), for which the name pipmenthol has been suggested, usually forms snow-white acicular crystals, or stellate groups of white, satiny needles, having the characteristic odour of peppermint. The product from the Japanese and Chinese oils forms prismatic crystals, closely resembling those of magnesium sulphate, and having a peculiar fragrant odour, suggesting a mix- ture of peppermint with some other members of the mint family. Menthol is but slightly soluble in water, but imparts to it its characteristic taste and smell. It dissolves readily in alcohol and ether, and in volatile and fixed oils. It is not soluble in aqueous alkalies, a character which distinguishes it and enables it to-be separated from thymol and phenol. Menthol is now extensively employed as a remedy for neuralgic headache and other affections. It forms the active constituent of the "neuralgic crystals," which, however, are liable to considerable adulteration. Thus, in addition to a legitimate economisation of the menthol by forming the base of the pencil of paraffin wax, the menthol itself is sometimes mixed with paraffin; and fatty matters, thymol, and other substances are also added (Pharm. Jour., [3], xv. 365, 686). To ascertain the quality of a pencil, a portion of the substance should be scraped from the surface and its melting point determined. Pure menthol is said to melt at 36 C., but the com- mercial article more commonly fuses at 41* to 43 C. An admixture of paraffin wax notably raises the melting point, unless some other adulterant is also present. On heating a weighed portion of the exterior of the pencil to 100 C. till constant or nearly constant in weight, the menthol will volatilise, and its quantity may be ascer- tained from the loss in weight, none of the usual adulterants, such as fatty matters, spermaceti, paraffin wax, salicin, salicylic acid, 1 Besides menthol and menthene, C 10 H ]8 , Japanese peppermint oil is said to contain an isomer of borneol, C 10 H 18 0, which, however, is appar- ently absent from the oil prepared at Mitcham, which contains several hydro- carbons of the formula C 10 H 16 and 15 H 24 , having a terebinthinate, somewhat lemon-like odour. BORNEOL, 445 thymol, &c., being sensibly volatile at 100. Mineral matters, such as magnesium sulphate, which is said to have been used as an adulterant of menthol, will remain on heating the sample to dull redness in the air. The ready solubility of menthol in cold rectified spirit is a test of some value, as many of the adulterants (e.g., paraffin, sperma- ceti, and fats) are insoluble in that menstruum. The alcohol should be heated to boiling to ensure the complete solution of the menthol, and then allowed to cool. By operating in this manner the test may be made quantitative. Salicin may be readily recognised by its bitter taste, solubility in water, and the red colour it assumes when touched with strong sulphuric acid. Salicylic and benzoic acids will communicate an acid reaction to the alcoholic solution of the sample. They may be isolated by treating the sample with aqueous soda, agitating the liquid with ether, separating the ethereal layer, and acidulating the concentrated aqueous liquid with hydrochloric acid, when they will be thrown down as a bulky white precipitate readily soluble in ether. Thymol may be separated from menthol by treating the sample with a hot solution of soda, which dissolves the thymol only. Thymol may be detected by Eykrnan's test (page 449). Menthol pencils adulterated with many of the above-named substances produce an intense prickling sensation on the skin, quite distinct from the cooling sensation produced by pure menthol. BORNEOL. C 10 H 18 = C 10 H l7 .OH. (See also page 443.) This body is imported under the name of " Borneo camphor," which contains 2 to 3J per cent, of resin and other impurities, from which the borneol can be obtained pure by sublimation. It crystallises in prisms. Artificial borneol, obtained by the action of sodium or alcoholic potash on common camphor, resembles the natural product in every respect, except in its optical activity, the portions obtained at the beginning and end of the process being dextro-gyrate, while the intermediate fractions are laevo-rotatory. By nitric acid, borneol is converted into common camphor, C 10 H 16 0, and by continued treatment into camphoric and camphoronic acids. A terpene called borneene, C 10 H 16 , is found in association with borneol. It occurs in commerce under the name of cam- phor oil, but differs from the similar product obtained with laurel-camphor by not yielding crystals on exposure to air. The liquid camphors contained in the essential oils of hops, Indian geranium, cajeput, coriander, &c., are isomeric with borneol. The camphor of oil of patchouli is a crystal- line mass melting at 54 to 55 and boiling at 296 C. It has the composition C 15 H 26 0, and hence is homologous with borneol. 446 LAUREL CAMPHOR. LAUREL CAMPHOR. COMMON CAMPHOR. C 10 H 16 0. (See page 443.) Camphor is usually obtained from the wood of the camphor- laurel (Campliora officinarum) by a rough process of distillation with water, and is purified by resublimation. 1 It is also produced by the oxidation of camphene, C 10 H 16 , by platinum-black or chromic acid mixture, and by the oxidation of borneol. Commercial camphor forms a colourless, translucent, tough, fibrous mass, but may be obtained crystallised in white prisms. It has a peculiar fragrant odour and burning taste. The density of com- mon camphor varies from *9 8 6 to '996. It melts at 175 C., and boils at 204, but vaporises rapidly even at the ordinary tempera- ture. Camphor is optically active, the apparent specific rotation varying with the nature of the solvent and the concentration of the solution. For a 10 per cent, solution in alcohol it is about +42 '8 for the sodium ray. Oil of feverfew yields a camphor which is Isevo-rotatory to the same extent, but in all other respects is un- distinguishable from ordinary camphor. Camphor is nearly insoluble in water, only one part per 1000 being taken up ; but it is readily soluble in alcohol, ether, acetone, acetic acid, carbon disulphide, chloroform, and oils. The "spirit of camphor" of the Pharmacopoeia is a solution of one part by weight of camphor in nine measures of rectified spirit. The author found that such a solution occupied fully the bulk of the spirit used plus that of the camphor before solution, there being expan- sion rather than contraction in the act of solution. Rubini's "essence of camphor" is a solution of camphor in an equal weight of rectified spirit. 2 On diluting an alcoholic solution of camphor with water, the solid is precipitated in white flocks. If the proportion of alcohol exceed a certain limit, no amount of dilution will cause precipitation. When camphor is triturated with chloral hydrate, menthol, thymol, or phenol, the mixture speedily liquefies. The chemical relationships of camphor are somewhat uncertain. It has some analogy to the aldehydes, but is not oxidised by chromic acid mixture, and forms no compound with acid sulphite of sodium. It absorbs hydrochloric acid, sulphur dioxide, and nitric peroxide gases, forming colourless liquids decomposed on addition of water. Camphor is not affected by the ordinary re- ducing agents, but if dissolved in an inert liquid, such as toluene, and heated to 90 with sodium, it forms sodium camphor, 1 During the process an oil distils over called liquid camphor or oil of camphor, (C 10 H 16 ) 2 0, which deposits camphor on exposure to the air. 2 " Compound Tincture of Camphor, B.P.," may be analysed as described in vol. i. p. 114. REACTIONS OF CAMPHOR. 447 C l0 H 15 NaO, and borneol, C 10 H 18 0. By distillation with zinc, chloride or phosphoric anhydride camphor yields c y m e n e, C 10 H U , water, and other products, while carvacrol, C 10 H 14 0, is produced by heating camphor with half its weight of iodine. These reactions render it probable that camphor is a benzene-derivative, containing methyl and propyl in the para position, as in cymene and carvacrol. With alcoholic potash, camphor yields borneol and c a m p h i c acid, C 10 H 16 2 , a behaviour which appears to establish its analogy to benzoic aldehyde. 1 Heated to 400 with soda-lime it yields campholic acid, C 10 H 18 2 . By prolonged treatment with nitric acid of 1'37 sp. gravity, camphor is chiefly converted into camphoric acid, C 10 H 16 4 , which on further boiling is oxidised to camphoronic acid, C 9 H 12 O 5 . Camphor unites with bromine to form a crystalline, very unstable dibromide, which on distillation splits up into hydrobromic acid and monobrom-camphor, C ]0 H 15 BrO. This last substance is of some therapeutic interest. It crystallises in prisms fusible at 76 C. and boiling at 274, is readily soluble in alcohol, and is not decomposed by alcoholic potash. Commercial camphor is said to be liable to be adulterated with terebenthene hydrochloride. Such an improbable sophistication would be readily detected by the formation of hydro- chloric acid on burning the substance. Camphor can be readily separated from most substances with which it is liable to occur. From alcohol it may be partially sepa- rated by addition of water, the solution being afterwards fractionally distilled. The camphor may also be determined by treating the tincture with excess of chromic acid mixture, when the alcohol will be oxidised to acetic acid. After neutralising the liquid the camphor may be filtered off, pressed, and weighed ; or the acetic acid may be determined, calculated to its equivalent of alcohol, and the camphor estimated by difference. If this plan be adopted, any water should be previously separated by agitating the tincture with dry potassium carbonate. THYMOL. Thy my 1 alcohol. (See also page 443.) Thymol is the camphor or stearoptene of thyme oil, and is also contained in the volatile oils of horse-mint and ajowan. 2 1 Benzoic aldehyde, on treatment with alcoholic potash, yields benzyl alcohol, C 7 H 7 .OH, and b e n z o i c acid, C 7 H 8 2 . 2 Oil of thyme consists chiefly of a mixture of thymol with the hydrocarbons t h y m e n e, C 10 H 16 , and cymene, C ]0 H 14 . It is colourless when freshly 448 THYMOL. It is extracted by agitating the oil with an equal measure of a 20 per cent, solution of caustic soda. The aqueous layer is separated and treated with excess of dilute acid, when the thymol separates as an oily layer. A better plan is to expose the crude oil to a temperature of C., when the thymol crystallises out. It may be purified by crystallisation from alcohol. Thymol is a phenol, and homologous with carbolic and cresylic acids, which it closely resembles in its general properties. It is a powerful antiseptic, its preservative power being ten times as great as carbolic acid according to Bucholz, and four times as great according to Willmott. It acts as a caustic on the lips and mucous membrane, but does not irritate the skin like carbolic acid. Thymol forms large colourless crystals having a feeble aromatic smell and burning taste. It melts at 44 C., and does not readily resolidify unless touched by a solid body or a crystal of thymol. It boils at about 230 C. Solid thymol is slightly heavier than water (sp. gr. 1'028), but in the fused state it is rather lighter; the density appears to be somewhat variable. In water, thymol is scarcely soluble, requiring about 1200 parts of cold or 900 of boiling water. Even this weak solution is powerfully antiseptic. Rectified spirit dissolves its own weight of thymol, the greater part separating again on dilution. A solution of 4 grains of thymol to the fluid ounce of spirit is miscible with water in all proportions. Thymol is very sparingly soluble in glycerin, requiring 120 parts for solution. The liquid is precipitated by an equal measure of water, but is perfectly miscible with four measures. The solution so obtained is a useful lotion. Thymol is readily soluble in glacial acetic acid. It is also freely dissolved by ether, chloroform, benzene, petroleum spirit, and oils. When thymol and camphor are triturated together, a syrupy liquid is obtained, which is readily miscible with vaselene and similar preparations. Thymol is insoluble in small quantities of alkaline distilled, but becomes deep red on keeping. It has a density of '87 to '90. When the oil is distilled, thymene passes over between 160 and 165, and the cymene between 170 and 180 C.', the thymol is much less volatile, and passes over towards the end of the distillation. Much of the oil of thyme of commerce consists merely of thymene and cymene, the thymol having been already extracted. Oil of thyme may be assayed for thymol by the process with alkali used for the extraction of thymol. If the thymol be present in too small a proportion to separate as a measurable layer on acidulating the solution of thymolate of sodium, the liquid may be agitated with ether and the thymol recovered by evaporating the ethereal layer. The presence of turpentine oil in oil of thyme may be detected by adding a few grains of iodine to five or six drops of the oil. In presence of turpentine a lively reaction at once ensues, with considerable rise of temperature and disengagement of vapours. Thyme oil itself gives a slight reaction after a time. REACTIONS OF THYMOL. 449 liquids, but dissolves in presence of an equivalent amount of soda (40 of soda to 150 thymol), forming a soluble compound, which is decomposed by acids with separation of the thymol. If thymol be dissolved in four parts of concentrated sulphuric acid it forms a yellowish liquid, which acquires a rose colour when gently warmed. If this solution be diluted with ten times its measure of water, and the liquid digested with excess of white lead and filtered, the filtrate contains lead thymo-snl- p h o n a t e, and acquires a beautiful violet-blue colour on adding a drop of ferric chloride. Phenol gives a similar reaction. With excess of bromine water, solutions of thymol yield a yellowish- white precipitate of a bromo-derivative, which gradually collects to globules of a yellowish liquid. The author has not succeeded in applying the reaction to the determination of thymol. A delicate test for thymol consists in heating the solution with half its measure of glacial acetic acid, and at least its own measure of concentrated sulphuric acid, when a fine violet-red coloration will be produced, not destroyed by boiling, and having a characteristic absorption-spectrum. J. F. E y k m a n modifies this test by dis- solving a little of the sample in 1 c.c. of glacial acetic acid, and adding five or six drops of strong sulphuric acid and one drop of nitric acid, when, if thymol be present, at first a greenish and then a fine blue coloration will make its appearance in the lower part of the test-tube, and will spread throughout the liquid on shaking. Phenol gives a violet-red colour, but menthol, camphor, borneol, and salicylic acid give no colour- reaction M r hen similarly treated. Tested with the reagents for phenol (see " Carbolic Acid "), thymol in aqueous solution gives the following reactions : b. Thymol gives no coloration with ferric chloride. c. With ammonia and hypochlorites, strong solutions of thymol give a greenish colour, changing very slowly to blue-green and red, but with more dilute solutions a mere turbidity is produced on heating, without any colour resulting. d. With sodium hypochlorite and aniline, thymol behaves like phenol. e. Thymol in tolerably strong solutions (1 in 5000) gives a red or violet coloration or precipitate with Millon's reagent, but the reaction is far less delicate than with phenol, and the colour is destroyed by boiling. Thymol reduces gold and platinum from their solutions (the latter only on boiling) far more readily than does phenol. It appears from the above that phenol in presence of thymol may be best detected by its reactions with ferric chloride, and in very dilute solutions by ammonia and hypochlorite. In the con- VOL. II. 2 F 450 CANTHARIDIN. centrated state, thymol is distinguished from phenol by its slighter solubility in water, glycerin, and alkaline liquids, and by forming a liquid bromo-derivative. It may be separated from phenol by fractional distillation, and from menthol by excess of strong solu- tion of caustic soda. CANTHARIDIN. Cantharidic Anhydride. C 10 H 19 4 . (See page 443.) Cantharidin, the active principle of Cantharides or Spanish fly, and of other vesicating insects, has many of the properties of a stearoptene or camphor. When pure it forms four-sided prisms, but is often deposited from its solutions in needles or brilliant micaceous plates. It melts at 200 C., and volatilises in white fumes, which strongly irritate the eyes, nose, and throat, and con- dense in lustrous rectangular prisms. Cantharidin has feebly-marked acid properties. It is insoluble in pure water, but dissolves in caustic alkalies to form canthari- dates. On adding excess of acetic or dilute hydrochloric acid to the cold dilute alkaline liquid, no precipitate is formed; but on warming the clear liquid to about 70 C., Cantharidin is reprecipi- tated, probably owing to the loss of the elements of water by the unstable soluble cantharidic acid, C 10 H 12 5 = C 8 H 13 2 .CO.COOH. Cantharidin may be crystallised from hot nitric or hydrochloric acid, and is soluble in strong sulphuric acid, being reprecipitated on dilution. Cantharidin dissolves readily in rectified spirit, and is also soluble in ether, acetic ether, and chloroform ; but is nearly in- soluble in petroleum spirit or carbon disulphide. It is extracted from acidulated aqueous liquids by agitation with chloroform. Cantharidin has well-marked poisonous properties, and the beetles containing it have not uncommonly been administered with criminal intent, on account of their powerful aphrodisiac character. In toxicological inquiries, the coats of the stomach and intestines should be carefully examined with a lens, with a view of detecting particles of the characteristic, iridescent, green wing-cases of the beetles. In the event of a tincture having been administered, the only available test is the isolation of the cantharidin in the form of an extract or tincture, and the application of a small portion of the product to a sensitive part of the skin (e.g., the lobe of the ear, or the inside of the fore-arm). If cantharidin be present, even in small quantity, a well-marked blistering will occur. A mixture of 1 part of cantharidin in 500 of lard produces very strong vesiculation. In examining for cantharides the viscera should be cut small, and digested with rectified spirit slightly acidulated with acetic acid. The filtered liquid is then concentrated by evaporation till ASSAY OF CANTHAEIDES. 451 the alcohol is driven off, and then agitated with chloroform. The chloroform is separated from the aqueous liquid, evaporated, and the residue applied to "the skin. If desired, the cantharidin may be further purified by treatment with carbon disulphide to remove fat, and then recrystallised from chloroform. O'OOl gramme of canthari- din dissolved in a drop of alcohol will produce marked vesiculation. Cantharides may be assayed for cantharidin by the following process described by H. G. Greenish (Pkarm. Jour.), [3], x. 729) : 25 grammes of the powdered flies are exhausted by treat- ment with gasolene in a percolator or Soxhlet's tube. The solvent should be limited to 100 c.c. measure, and a correction of 0'0108 gramme of cantharidin made for the slight solubility of the prin- ciple in the liquid. The flies thus freed from fat are now thoroughly moistened with solution of soda, and the mixture dried at 100 C. Much ammonia is evolved, and a soluble canthari- date of sodium formed. The dried mass is finely powdered and transferred to a separator, where it is treated with excess of dilute hydrochloric acid, and the liberated cantharidin extracted from the aqueous liquid by agitation with a mixture of equal measures of ether and chloroform ; the ether-chloroform is separated, and the agitation repeated with a fresh quantity till the extraction is com- plete. The ether-chloroform is evaporated to dryness at a gentle heat, and the residue weighed. The crude cantharidin thus obtained may be transferred to a small tared filter and washed with a little absolute alcohol, and then with 2 or 3 c.c. of water. Any remaining traces of oil may be removed by a little gasolene. If the washing with alcohol and water be employed, the volumes used must be noted and a correction made of '00077 gramme for each 1 c.c. of alcohol, and '00050 for each 1 c.c. of water. Resins. French Resines. German Harze. Resins occur as natural or induced exudations from plants, in admixture with the essential oil peculiar to the plant. All natural resins appear to be products of the oxidation of terpenes and allied hydrocarbons, and are produced in the plant and during collection by the oxidation of the essential oil. Resins containing gum or mucilage are termed gum-resins, and those containing volatile oils are called oleo -resins, tur- pentines, or balsams. 1 1 The name turpentine ought, strictly speaking, to be limited in its applica- cation to the oleo-resins obtained as exudations from various species of Pinus, Abies, Juniperus, and other allied genera. It is, however, often applied to the spirit or e s s e n t i a 1 o i 1 (e.g. , oil of turpentine) obtained by distilling 452 CHARACTERS OF RESINS. In some cases resins are prepared by simple exudation (e.g., copal); in other cases by distilling off the essential oil mixed with the resin (as common rosin or colophony); and in some in- stances by destructive distillation (e.g., pitch and g u a i a c u m). As a class, the resins are solid, transparent bodies, sometimes crystallisable. They have no well-marked odour or taste, and range in density from 0'9 to 1'2 or somewhat higher. They are easily fusible, but not volatile, and are decomposed when heated in close vessels, with formation of pyro-products consisting essentially of hydrocarbons. They are readily combustible. Resins are very bad conductors of electricity, and when excited by friction become negatively electrified. The resins are insoluble in water, but they dissolve in alcohol and many other organic liquids. The solutions of many of them have an acid reaction, and yield a lather on treatment with a solu- tion of caustic alkali. Their solutions in alkaline liquids differ from ordinary soaps in being incapable of precipitation by addition of common salt unless used in very large quantity. The resins are rarely even approximately pure definite bodies, but are usually mixtures of several analogous oxygenated bodies in various proportions. Their chemical relations are at present but very imperfectly understood. the crude turpentines above mentioned, when the non-volatile resin is obtained as a secondary product. The crude turpentines are viscous honey-like liquids, or soft or brittle solids. Their odour is usually terebinthinate, but sometimes agreeably aromatic, and their taste varies from bitter, nauseous, and acid, to a pleasant aromatic flavour. They are not sensibly soluble in water, though some yield traces of formic and probably succinic acid to that solvent. Balsams are, correctly speaking, such of the oleo-resinous exudations of plants as contain benzoic or cinnamic acid, and yield cinnamate or benzoate of methyl or ethyl by dry distillation. They are liquid, more or less viscous, and yield essential oils on distillation with water. The term balsam is mis- applied to "canada balsam" and "copaiba balsam," which are true turpen- tines not containing or yielding benzoic or cinnamic acid ; while "dragon's- blood " would be more properly classed among the resins. The description of the minute and often inappreciable differences between the various oleo-resins known in commerce as turpentines and balsams belongs rather to a work on pharmacy and materia medica than to one on chemical analysis, and as their recognition and examination are rarely required by others than pharmacists, it is unnecessary to describe them individually or in detail. Much information on the botanical origin, methods of obtaining, characters and composition of the turpentines and balsams will be found in Watt's Dic- tionary of Chemistry, vol. i. p. 491 et seq. ; and a most exhaustive series of articles by Dr Julius Morel, published in the Pharmaceutical Journal, [3], vol. viii. pp. 21, 81, 281, 342, 542, 725, 886, 981, 1024 ; and vol. ix. pp. 673 and 714. See also the footnote on page 454. SEPARATION OF RESINS. 453 The resins are employed in medicine, in the manufacture of varnishes and soap, for making sealing-wax, and for stiffening purposes. Water and general impurities may be separated from the resins by dissolving the substance in oil of turpentine or other suitable solvent. If the operation be conducted in a graduated tube the separated water may be measured; while the insoluble matters may be filtered off, washed with turpentine oil, dried, weighed, and further examined. From the neutral fixed oils resins may be separated by treating the mixture with alcohol of about 0'85 sp. gr. 1 The alcohol is subsequently separated, and the dissolved resin recovered by eva- porating it to dryness. The results are only approximately correct. Acid resins, such as common colophony, may be separated from the neutral fats by boiling the substance with a strong solution of bi- carbonate of sodium or borax. After cooling, the aqueous liquid is separated from the oil, and the resin precipitated from its solu- tion in the sodium salt by adding hydrochloric acid. For other and detailed methods of separating resins from fixed oils and fatty acids, see pages 77, 78, and 224. Eesins may be separated from the essential oils and camphors, in admixture with which they so frequently occur, by distilling the substance in a current of steam, and then, if necessary, immersing the flask or retort in a chloride of calcium bath, while still con- tinuing the current of steam (see also page 431). Essential oils and camphors may also be separated by rubbing down the resinous substance to a fine powder in admixture with a known quantity of sand, and then macerating in petroleum spirit. Part of the true resin will also be dissolved, and hence the filtered solution must be evaporated to dryness, the residue heated to 110 or 120 C. till constant, and the weight found added to that of the undissolved portion, when the loss will be the essential oil and 1 The following figures are said to fairly represent the specific gravities of various resins and balsams at a temperature of 15 to 16 C. ( = 60 F.): Pine-rosin, yellow trans- Copal, very old, 1-054-1 '055 parent, . . 1-083-1-084 Benzoin, Siam, . . 1-235 ,, whitish opaque, 1 '044-1 '047 Penang, . 1-145-1 -155 ,, dark colophony, I'lOO Shellac, light coloured, 1 '113-1 '114 darker, . . . 1'123 ,, Borneo, . Guaiacum, pure, . 1-165-1-170 1-236-1-237 , 1-074-1-094 ,, bleached, . . '965-0 "968 Dammar old . 1 '075 Sandarac, . . . Mastic . 1-038-1-044 1-056-1-060 3opal, E'. Indian, . . 1 '063-1 '070 ,, W. Indian, . . 1 '070-1 '800 Tolu, old brittle, . . 1-231-1-232 454 EXAMINATIONS OF RESINS. other volatile constituents. The amount of resin dissolved by the petroleum spirit is often of interest. Thus, in the case of copal, the quality of the sample is better the smaller the quantity of non-volatile matter dissolved by the petroleum spirit. The mix- ture of ethereal oil and resin left on evaporating the petroleum spirit at the ordinary temperature often yields more or less charac- teristic colour-reactions with the reagents for essential oils men- tioned on page 434 et seq. The residue insoluble in petroleum spirit should be weighed and then treated with ether, after which it should be ascertained if alcohol will extract anything insoluble in ether or petroleum spirit. In the case of gum-resins, sugar is one of the principal substances extracted by alcohol, while gum, salts, &c., may subse- quently be dissolved out by water, which in some cases (e.g., gum tragacanth) may produce swelling without actual solution of the gummy matter. The ethereal solution should be tested as to its miscibility with alcohol, and a portion may be evaporated to dry- ness and the residue examined by colour-tests. It is also desirable to ascertain if a turbidity is produced by adding ether, ammonia, or an alcoholic solution of lead acetate to the spirituous solution of the original resin. Useful information may also be obtained by treating the original resin with chloroform, ether, or a saturated aqueous solution of sodium carbonate, which last may produce colorations or dissolve out cinnamic acid and acid resins. The foregoing methods, chiefly due to Hirschsohn, afford useful indications of the nature of resinous substances, but the positive identification of the various individual resins is a matter of considerable difficulty even when only one is present, and in admixture the task is often insuperable. The only systematic scheme for the identification of resins, gum-resins, and balsams is that devised by Hirschsohn, and the practical importance of the subject is not great enough to justify a reproduction of his observations. 1 The bromine-absorptions of a number of resins have been deter- mined by M il Is and Muter (Jour. Soc. Chem. Ind., iv. 97). The process is substantially the same as that described on page 331, but the bromine is allowed to act all night on the finely-powdered resin in presence of carbon disulphide, and the excess then ascer- tained by titration in the usual way. Much hydrobromic acid was formed in many cases. E. J. Mills has also determined the 1 Hirschsohn's results are fully described in the Pharmaceutical Journal, [3], vii. 369, &c. ; viii. 389; and in Watt's Dictionary of Chemistry, viii. 1743. CHARACTERS OF VARIOUS RESINS. 455 proportions of potash neutralised by various resins (Jour. Soc. Chem. Ind,, v. 221). The finely-powdered resin was treated with a decided excess of normal alcoholic potash, and the mixture allowed to stand in a closely-stoppered bottle for eighteen hours, when phenol-phthalein solution was added, and the excess of potash was titrated with normal hydrochloric acid. Performed in this way, the determination is a cross between Koettstorfer's pro- cess described on page 44 and that for determining free fatty and resin acids described on page 76, but all three methods would probably give essentially the same figures in most cases. With benzoin and other balsams containing ethereal salts, the dif- ference according to method employed would be very important, and the writer has found colophony to require a sensibly higher proportion of acid by Koettstorfer's process than is requisite to simply neutralise the free acids. The following table shows the bromine-absorptions and neutral- ising powers of various resins, according to Mills and Muter :-^- Kind of Resin. KHO neutralised per cent. = Saponification Equivalent. Bromine- Absorption. Hydrobromic Acid formed. Rosin, refined, . . Shellac, .... ,, bleached, . Benzoin, .... Amber, .... Anime, .... Gamboge, .... Copal 18-1 23-0 18-2 22-3 16-1 9-5 15-5 12-4 308-6 2427 306-9 256-0 347-6 585-5 381-1 450'8 1127 5-2 4-6 38-9 53-5 60-2 71-6 [89 -9] 1 some some much much much ,, reduced to f by boiling, . . . . " Sandarac, .... Kauri, .... 12-9 16-4 12-9 433-4 340-6 4337 [84 -5] 1 96-4 108'2 much very much Thus, 21-0 265-6 108-5 Dammar, .... Elemi, .... Mastic, .... 5-2 3-3 11-7 1068-1 1697-9 478 6 117-9 122-2 124-3 much very much much The chief feature of interest in the bromine-absorptions is the comparatively low figures obtained with shellac. Although not included in the table, Mills has determined the bromine-absorptions of various specimens of the tinctorial resins known as dragon's- blood and xanthorrhoea resin, and found for the first figures varying from 7 to 33 per cent, and for the latter from 8 to 85 per cent. 1 These determinations were not made on the same samples as those used for ascertaining the neutralising power. 456 BALSAM OF COPAIBA. With respect to the proportions of potash neutralised, Mills points out that sylvic acid, C 20 H 30 0, would theoretically react with 18 '49 per cent, of KHO, and that the proportions of potash neu- tralised by the various resins exhibit (approximately) very simple ratios to this amount. This, he suggests, is due to the resins being "in effect a series of polymers of a body C 20 H 30 2 ." Mills does not appear to have examined more than a single sample of each resin ; but it is evident that, if further experience should show that the neutralisation-equivalents and bromine- absorptions are fairly constant, the conjoint determinations would go far to allow of the recognition and determination of two resins present in a mixture. The method could probably be used with advantage for the analysis of varnishes, after evaporating off the volatile solvent. It might be advantageously combined with the process described on page 125. The following resume of the methods devised for assaying balsam of copaiba affords a good example of the examination of such bodies. 1 The proportion of resin, and, by difference, of volatile oil, in copaiba balsam may be determined by heating a known weight (1 to 1*5 gramme) of the sample at 100 C. until it has a rich brown colour and ceases to lose weight. If the balsam be free from caster or other fixed oil, the residual resin will be perfectly brittle and pulverisable, but if 1 per cent, of the adul- terant be present it is impossible to reduce the residue to a fine powder, and with 3 to 5 per cent, of fatty oil the resin feels quite sticky. A convenient plan is to place a drop of the hot residue on a small piece of well-glazed writing paper; after cooling, if the paper be bent the resin left by a pure balsam will be so brittle as to break into numerous fragments (Siebold, Year-Book Pharm., 1877, p. 601). For the determination of fatty oils in copaiba balsam J. Muter (Analyst,!. 160) employs a process based on the insolubility of oleate and ricinoleate of sodium in ether-alcohol, 1 Copaiba balsam is an oleo-resin obtained from several species of Copaifera. It varies greatly in viscidity, owing to the inconstant proportion of essential oil, which is usually between 35 and 70 per cent., but occasionally as high as 82 per cent., the remainder being resin. Similarly, the specific gravity of the substance varies from '915 to '995. The resin of copaiba balsam iscapaibic acid, but some varieties also contain a neutral resin (see also W. A. Rush, Pharm. Jour., [3], x. 5). Copaiba balsam is very liable to adulteration, the sophistications consisting in the addition of fixed oils (lard, linseed, and castor oils), other turpentines or oleo-resins, and gurjun balsam, or East Indian wood oil, which presents a close resemblance to copaiba in taste and smellj and has been used as a substitute for it. Oil of turpentine and oil of sassafras have also been occasionally added to balsam of copaiba. ASSAY OF COPAIBA BALSAM. 457 and the solubility of capaivate of sodium in the same medium. The process is practically identical with the modified Barfoed's method described on page 224, with the difference that the fatty acids are subsequently determined in the insoluble soap, after washing with ether-alcohol, instead of the resin being determined in the solution. Gurjun balsam, or wood oil (see Hirschsohn, Pharm. Jour., [3], x. 561), is often used as an adulterant of or substitute for copaiba balsam. To detect it, H a g e r mixes the sample with 4 volumes of petroleum spirit, which should form a solution which should either remain clear or merely give a very slight deposit forming a thin film on the tube. In the presence of gurjun oil a voluminous deposit is formed after standing half an hour. Benzene cannot be substituted for petroleum spirit, 'but ether gives very similar results. 1 A balsam adulterated with gurjun oil is not quite clear, and frequently exhibits prisms of gurjunic acid under the microscope. To effect the detection of oil of turpentine in copaiba the essen- tial oil should be separated from a portion of the sample by distilla- tion. Oil of turpentine passes over before the oil of copaiba, and can be recognised by its odour when the first few drops of distillate are heated on a watch glass. 2 or 3 per cent, of the adulterant may thus be detected. An idea of the amount present may be obtained by noting the density and boiling point of the distilled oil. Oil of copaiba boils at 240 to 250 C., and oil of turpentine at about 160 C. For the detection of Venice turpentine in copaiba, H a g e r ( Year- Book Pharm., 1871, p. 64) recommends the following test: 5 to 7 c.c. of the sample are mixed in an evaporating basin with 5 or 6 drops of water and sufficient levigated litharge to form a thick semi-fluid mass. At a temperature of 20 to 25 C. a well- marked terebinthinate odour is evolved if 10 per cent, of Venice turpentine be present, and is still recognisable with as little as 5 per cent, of the adulterant. By the following modification of this test, Hager effects the approximate estimation of the turpen- tine. 5 grammes of balsam, 8 to 10 drops of water, and 15 grammes of litharge are heated together for 15 minutes 011 a sand- 1 Another good test for gurjun oil is to dissolve the sample of balsam in about 20 measures of carbon disulphide, and add a drop of a cold mixture of concentrated sulphuric and nitric acids, which in presence of gurjun oil occasions a splendid violet coloration. Fish liver oil and oil of valerian give a similar reaction, but the colour is evanescent, while that produced by gurjun oil persists for some hours. To exclude fish oil a small quantity of the sample may be distilled and the test applied to the distillate. This is a preferable plan for several reasons. 458 COMPOSITION OF COLOPHONY. bath and then for several hours at 100 C. After cooling, the hard mass is powdered and boiled with petroleum spirit, the filtered liquid evaporated, and the residue macerated with rectified spirit for several hours. If the sample were pure, the filtered alcoholic solution leaves on evaporation about '2 or *3 of resin, which, when boiled with caustic potash, yields a filtrate which is scarcely tinged by ammonium sulphide. In the presence of Venice turpentine the residue from the alcoholic solution contains about three-fourths of the resin of the adulterant, and yields with potash a liquid in which sulphide of ammonium produces an abundant brownish-black precipitate of lead sulphide, which may be collected and weighed if desired. The method is based on the solubility of the lead com- pound of the turpentine-resin in both petroleum spirit and alcohol, and the insolubility of capaivate of lead in the same menstrua. 1 COLOPHONY, or common resin, often called "rosin," is the residue left on distilling off the volatile oil from crude turpentine. It consists chemically of a mixture of several resin acids and the corresponding anhydrides. Of these, abietic anhydride, C 44 H 62 4 , is the chief. On boiling the resin with 80 per cent, alcohol, filtering, and adding a little water, abietic acid, C 44 H 64 5 , separates in the crystalline state. Abietic acid melts at 165 C. (or, according to Dragendorff at 144), crystallises from alcohol in laminae, and is readily soluble in ether, chloroform, benzene, glacial acetic acid, and carbon disulphide. Prolonged heating converts it into its anhydride, which was formerly known as pinic acid. This body is gradually reconverted into abietic acid by the action of 70 per cent, spirit, and is soluble in absolute alcohol, but the solution yields no crystals on evaporation. Abietic acid is dibasic, and forms a series of salts which are generally uncrystallisable. The abietates of the alkali-metals are readily soluble in water, alcohol, and ether, and are possessed of marked detergent properties. Hence the employ- ment of rosin in soap-making. An acid called sylvic acid, C 90 H 30 2 , exists in small quantity in colophony, and the isomeric pimaric acid, melting at 1 48-1 49, is contained in the resin from " galipot " and the crude turpentine 1 H a g e r has met with oil of sassafras as an adulterant of copaiba. He detects it by mixing 1 c. c. of the sample with 2 c. c. of concentrated sulphuric acid; after the mixture has cooled, 20 c.c. of alcohol are added, the mixture heated to boiling, and set aside. With pure copaiba a milky greyish or reddish- yellow liquid is obtained on addition of the alcohol, and on boiling the liquid becomes clear and yellow, and a resinous compound settles to the bottom. If oil of sassafras be present, addition of alcohol produces a dark brown colour, becoming on boiling still darker with a violet tint. CHARACTERS OF COLOPHONY. 459 of the Pinus maritima of Bordeaux. Pimaric acid is difficultly soluble in cold, but easily in boiling alcohol, and is also soluble in ether. It resembles abietic acid in most of its properties, but differs in possessing a bitter taste. 1 According to Vesterberg (Ber., xviii. 3331; Jour. Chem. Soc., iv. 365), the substance hitherto described as pimaric acid is probably a mixture. Colophony or rosin is a transparent or translucent resin, usually having a density of about 1'07 to 1*08, the extreme figures being r04 to riO. It is very brittle, breaking with a shallow con- choidal fracture. It has a faint terebinthinate odour, and is nearly tasteless, but some varieties possess a nauseous and highly charac- teristic after-taste. Colophony varies in colour from a pale amber to dark reddish- brown. The darkest kind is known commercially as " black rosin." ' ' White rosin " is a light-coloured variety which is rendered opaque by containing water, on the gradual evaporation of which it becomes translucent. Colophony is quite insoluble in water, but dissolves readily in ether, chloroform, alkalies, and in the volatile and fixed oils. At 60 C. it is slowly soluble in an equal weight of alcohol or of glacial acetic acid. Colophony softens in boiling water, melts completely at a somewhat higher temperature (some varieties at about 135 C.), and at a higher heat burns with a dense yellow and sooty flame. On blowing out the flame, a highly characteristic smell may be observed. Colophony is readily dissolved by solutions of caustic alkalies and even by alkaline carbonates. The resultant soaps are brown, very deliquescent and soluble in water, and are not readily and completely precipitated from their solutions by addition of brine. Colophony may be detected by its physical characters and odour on heating. It may also be recognised by the nitric acid test described on page 188. It maybe titrated in alcoholic solution with caustic alkali and phenol-phthalein (see page 76), but its combining weight is somewhat variable. It usually neutralises about 1 8 per cent, of KHO, 2 though the proportion is sometimes as 1 According to Perrenoud, pimaric acid from galipot and ' ' abietiuic acid " from American colophony are isomeric, being both represented by the formula C 40 H 54 4 ; but while the ammonium salt of abietinic acid is gelatinous, the acid ammonium salt of pimaric acid crystallises in handsome needles. Abietinic acid is stated to melt at 165 C., but whether under this name abietic acid or sylvic acid is meant is not evident. 2 The free acids of a very pure, pale resin, examined in the author's labora- tory, neutralised 15 '5 per cent, of KHO, but by Koettstorfer's process 167 per cent, was neutralised. Similar results have been obtained with othei samples. Hence it is probable that colophony contains either ethers or anhydrides which do not react with caustic potash unless heated with it. 460 RESIN SPIRIT. low as 16. The separation of the acids of colophony from neutral fatty oils, hydrocarbon oils, and soap is described on page 87, and from free fatty acids on pages 78 and 224. The bromine-absorption of colophony is usually be- tween 100 and 113. The figures given by other resins will be found on page 455. Colophony may be distilled almost unaltered in a vacuum, and with but little change in a current of superheated steam at about 250 C., but when subjected to dry distillation it suffers decom- position and yields a variety of products, of which the so-called " rosin oil " is the chief. The yield of rosin oil is usually about 85 percent., the remaining 15 percent, including : about 3 per cent, of rosin spirit; water containing some acetic acid ; a heavy and powerfully anaesthetic gas containing carbonic oxide, ethylene, butylene, and pentine ; coke; and loss. 1 ROSIN SPIRIT, or Resin Spirit, is the lighter or more volatile oily portion of the product of the dry distillation of rosin. It is sepa- rated from the acetous aqueous liquid, agitated with water containing caustic soda and sometimes common salt, and is then redistilled. When thus refined, rosin spirit presents a close general resem- blance to oil of turpentine, but is of peculiar and highly complex composition. 2 The nature of rosin spirit is not wholly understood, but one of its constituents is a heptine, C 7 H 12 (probably methyl-propyl- allylene), boiling at 103-104 C., and having a density of '8031 at 20. This body is colourless, mobile, of characteristic odour, and is soluble in alcohol and ether. It absorbs oxygen very readily, and is without action on an ammoniacal solution of cuprous chloride or argentic nitrate. By treatment with concentrated sul- phuric acid it is polymerised, with formation of a di-heptine, C 14 H 24 , boiling at 235-250, and rapidly oxidising and resinify- ing in the air. By the action of water and air it is converted into a crystalline heptine glycol, C 7 H 12 (OH) 2 ,H 2 0, soluble in 1 The stills are vertical, with hemispherical ends, and hold from 50 to 70 barrels of rosin. They are heated directly, and distillation without steam is usually preferred, as in that case the production of spirit is less. Water passes over throughout the process. The residue, or pitch, is run off while still fluid. E. J. Mills has recorded the densities and bromine-absorptions of the products distilling at frequent intervals during an entire operation. The density increased from '909 to 1 '030 at the end of 20 hours, and then fell to '970. The bromine-absorption of the first product was 142 per cent, and gradually fell to 32 per cent. (Jour. Soc. Chem. Ind., iv. 328). 2 Renard (Jour. Chem. Soc., xlvi. 843) has given a list of the bodies recognised as constituents of rosin spirit, and Morris (Jour. Chem. Soc., xli. 167) a valuable list of references. ROSIN OIL. 461 water, alcohol, and ether. The crystals, as also the original hydrocarbon, when warmed with an acid (e.g., hydrochloric, sul- phuric, tartaric), give a series of colorations, the mixture passing through shades of yellow, red, green, and deep blue ; and on add- ing this liquid to alcohol a magnificent green colour is communi- cated to it (G. H. Morris, Jour. Chem. Soc., xli. 172). Rosin spirit itself does not give the reaction distinctly, and the author has not succeeded in applying it to the detection of rosin spirit in turpentine. ROSIN OIL, or Resin Oil, is the heavier and less volatile portion of the dry distillation of rosin, part of it distilling at a dull red heat. The crude oil first obtained can be purified by washing with a small percentage of sulphuric acid, followed by treatment with lime water and redistillation, with or without steam. A very superior product is obtainable by redistilling the oil over solid caustic soda, with the aid of a current of superheated steam. Zinc-dust and other reducing agents have also been employed, and a very fine oil is said to be obtainable by mixing the crude oil with cottonseed oil prior to distillation. The chemical composition of rosin oil is very imperfectly under- stood. It often contains a notable proportion of abietic acid, or, more probably, abietic anhydride, but the greater part consists of hydro- carbons of an indefinite nature. In part, at least, they probably consist of polymerised terpenes and h e p t i n e. 1 Commercial rosin oil ranges in specific gravity from about '980 to 1*100, and hence is denser than any of the animal or vegetable oils, and much denser than mineral lubricating oils. The colour of rosin oil varies from nearly water-white to dark brown. It generally presents a strong bluish or violet fluores- cence, which is apparent even in its dilute ethereal solutions. The bloom can be destroyed more or less completely by exposure to sunlight, by treatment with hydrogen peroxide, by addition of nitrobenzene, nitro- or dinitro-toluene, dinitronaphthalene, &c., or by heating with sulphur. Rosin oil is often strongly dextro-rotatory ; but the rotation is variable, being sometimes slight and occasionally left-handed. The optical activity is not due simply to the presence of rosin acids, as has been suggested, for the hydrocarbons isolated in the author's laboratory from refined rosin oil have exhibited a dextro-rotatory power as high as -f-46 for the sodium ray. To render highly- 1 However often rosin oil be distilled, the product always contains a small quantity of terpenes or terpenoid bodies, which are probably produced by de- polymerisation of the heavier hydrocarbons, or possibly by a process of " crack- ing," similar to that undergone by the hydrocarbons of petroleum ,(p. 327). 462 REACTIONS OF ROSIN OIL. coloured rosin oil fit for optical examination, Yalenta treats it with potassium ferrocyanide and then filters. Refined rosin oil has but little smell at ordinary temperatures, but when strongly heated it gives fumes having a marked odour of resin, neutral or nearly so in reaction, and which burn when inflamed with a large and very smoky flame. When rosin oil is distillate little or nothing usually passes over below 300 C. The taste of rosin oil is peculiar, and the after-taste strong and highly characteristic. Kosin oil is insoluble in water, and but slightly soluble in alco- hol, but it is miscible in all proportions with fatty oils, mineral oils, ether, chloroform, carbon disulphide, turpentine oil, and petro- leum spirit. Rosin oil is not capable of true saponification, or at least only so far as it consists of resin acids and phenoloid bodies. But even if these be removed, the hydrocarbons are capable of forming unstable compounds with slaked lime and other bases, which compounds are resolved again on distillation, and are of importance in the preparation of commercial "rosin greas e." 1 Superior rosin oil is sometimes made by distilling the crude oil with lime, or, preferably, caustic soda. The formation of a grease on trituration with slaked lime is one of the few characteristic reactions of rosin oil. Chlorine and bromine act somewhat violently on rosin oil. The proportion of bromine absorbed is very variable (see page 464). Nitric acid is sometimes without immediate action on cold rosin oil, but if the mixture be warmed a violent reaction often suddenly ensues, and, after cooling, the oil is found to have been converted into a more or less brittle red resin. Rosin oil usually shows a rise of 18 to 20 C. in temperature when treated with sulphuric acid as described on page 53, and forms a reddish-brown liquid which separates into two strata on standing. When agitated with one-third of their bulk of fuming hydro- chloric acid, most samples of rosin oil gradually acquire a dark and ultimately a black colour. 1 Rosin grease is made by stirring rosin oil with slaked lime made into a cream with water. Combination takes place, probably according to the for- mula C 10 H 16 ,2CaH 2 2 , and the superfluous water separates and is run off. The solid product is diluted with more rosin oil, and the solution obtained stirred into a further quantity, till the proportions of the constituents are about 13C 10 H 16 ,CaH 2 2 . The resultant rosin grease is used as a lubricant for iron bearings, and especially for the axles of pit-waggons, which are much exposed to moisture. It rapidly acetifies by heat and friction, and hence is not adapted for brass bearings. Rosin grease is often mixed with neutral coal-tar oils (naphthalene oils), and sulphate of barium, gypsum, whiting, and other make-weights are also added. EE ACTIONS OF ROSIN OIL. 463 R, e n a r d has observed that anhydrous stannic chloride develops a violet coloration with rosin oil. The author has found it more convenient to employ stannic bromide than stannic chloride, and finds that the reaction is much more delicate and under control if free bromine be also present and the oil and reagent be previously dissolved in carbon disulphide. The stannic bromide is prepared by allowing bromine to fall drop by drop on granulated tin con- tained in a dry flask immersed in cold water. The addition is continued until the permanent coloration of the product shows that the bromine is in excess. A further moderate addition of bromine is then made, and the liquid is then diluted with three or four times its measure of carbon disulphide, in which the stannic bromide is readily soluble. To employ the reagent, which when thus prepared appears to be perfectly stable, a few drops of the sample should be placed in a dry test-tube and dissolved in about 1 c.c. of carbon disulphide. The bromide reagent is then gradually added, when if rosin oil be present the liquid will rapidly acquire a fine violet coloration, which in the case of the employment of pure rosin oil is so intense as to necessitate dilution with carbon disulphide before the colour is perceptible. On standing for some time, a deposit of violet colour is formed at the bottom of the tube, and if the remaining liquid be poured off" and the residue be warmed with a little carbon disulphide, a violet or purple solution of great purity of tint may be obtained. This mode of operating is espe- cially useful in the presence of foreign oils or impurities which disguise the colour due to the rosin oil. In the presence of much mineral oil the author has found it a good plan to first mix the sample with a solution of stannic bromide in carbon disulphide, and then add, drop by drop, a solution of bromine in carbon di- sulphide, by which means the violet coloration may often be obtained unobscured by any colour produced by the mineral oil. 1 The violet substance to which the coloration is due appears to be permanent in the air, but the colour is destroyed by addition of alcohol, ether, ammonia, or water. Instead of dissolving the oil in carbon disulphide it may be dis- solved in glacial acetic acid, and the greater solubility of rosin oil than mineral oils in this menstruum affords a means of applying the test to mixtures of the two in a very advantageous manner. Thus, if the sample to be tested be shaken in the cold with twice its measure of glacial acetic acid, and the acid layer separated and tested with a solution of stannic bromide and bromine in carbon i A sample of lubricating oil from Russian petroleum (oleb-naphtha) gave a fiery red colour with the bromide reagent, a heavy oil from American petro- leum gave a bright yellow, and a shale lubricating oil gave an olive-green tint. 464 CHARACTERS OF ROSIN OIL. disulphide, a fine violet coloration will be produced if rosin oil be present. The coloration produced in acetic acid solution appears to be of a decidedly bluer shade than that obtained when carbon disulphide is used as the solvent for the oil, but the tint in the latter case varies considerably with the proportion of the reagent used, a large excess having a tendency to produce reddish tints. Although colophony is capable of producing various colour- reactions with the bromide reagent, the colour produced by rosin oil is not due simply to the presence of resin acids, the hydrocarbons isolated from the oil being also capable of giving the reaction. The following results of analyses of samples of rosin oil examined in the author's laboratory show the variation in the character of the commercial article. The specific gravity was determined by the bottle, the oils being too viscous to allow a plummet being satisfactorily used. The hydrocarbons were isolated as described on page 83, and the resin acids subsequently recovered by acidulat ing the alkaline liquid. Bromine-a bsorption; Bromine-a bsorption; Dr y. W et. Description of Sample. Specific Resin Hydro- Gravity. Acids. carbons. Total. As HBr. Total. As HBr. Very pale refined oil, Pale oil ; special, 990' 982 6-4 96-9 93-9 110-0 105-1 11-8 4-8 ... ... Pale sweet oil, . 979 1-1 63-0 4-7 56 : 5 13-6 Ordinary oil, 935: 17-8 81-2 138-5 97 Common dark oil (no ; the commonest), 1-099 11-1 88-6 66-6 7-6 ... Crude oil, . . 990 ... ... 60-8 3-9 47-0 ii'-2 Pine oil, . . . 986 73-9 5-1 51-9 8-9 Ink oil, . . . 1-006 ... ... ... ... ... It will be observed that the bromine-absorptions, as determined by the dry process (page 331) are extremely variable, and in some cases exceed the limits observed by Mills (footnote, page 460). There is also a wide divergence between the results by the dry and those by the wet process, and the absorptions of different oils are not even comparative. The figures obtained by the wet process are less than those yielded by the dry, while the reverse is the case with shale and petroleum products. The results were confirmed by repetition, and hence the anomalous figures are not errors of experiment. Rosin oil has a large legitimate employment as a lubricant, espe- cially for machinery and waggon wheels. It is used in the con- dition of rosin grease, and in admixture with olive, rape, and other DETECTION OF ROSIN OIL. 465 oils. 1 Mixed with rape oil it has been employed for adulterating olive oil, and it is frequently added to the inferior kinds of boiled linseed oil. It is also suspected to be added to the denser kinds of mineral lubricating oil. The detection of rosin oil in fatty oils is based on its isolation by the method described on page 83, and its subsequent identifica- tion by its taste, odour on heating, specific gravity, optical activity, reaction with stannic bromide, and formation of a grease with slaked lime. Some of these reactions are applicable to the original mixture of fatty and rosin oils. If the accurate determination of the rosin oil be desired, it will often be necessary to add to the weight of the hydrocarbons or ether-residue that of the resin acids, after separation from the fatty acids as described on pages 78 and 224. The detection of rosin oil in admixture with the mineral lubri- cating oils may be effected with tolerable ease and certainty, but the positive recognition of a moderate proportion of mineral oil in such a mixture is more difficult. Any optical activity of the sample or purple reaction with stannic bromide affords definite proof of the presence of rosin oil, and in many cases its existence is evident from the taste of the sample and its odour on heating. A high density and bromine-absorption, and a violent reaction with nitric acid, also afford strong evidence of the presence of rosin oil. Yalenta and Feigerle (Dingl. Polyt. Jour., ccliii. 418; Jour. Chem. Soc., xlviii. 93) employ glacial acetic acid for detect- ing rosin oil in mineral lubricating oils. They recommend that 2 c.c. of the oil should be treated with 10 c.c. of glacial acetic acid (sp. gr. 1-0562 at 15 C.), and heated for five minutes to 50 C. in a loosely corked test-tube immersed in a water-bath. The mix- ture is then passed through a small filter and the middle portion of the filtrate collected. A weighed quantity of the filtrate is then titrated with standard alkali and phenol-phthalein, whereby the weight of acetic acid present can be calculated, and the difference between the amount thus found and the weight of the portion of filtrate operated on gives the weight of oil dissolved by the acetic acid in that quantity of the filtrate. 2 When examined in this manner, the solubility of mineral lubricating oil (apparently from petroleum) varied from 2 '6 7 to 6 '50 grammes for 100 grammes of 1 Information respecting the mode of manufacture of rosin oil, and the com position of various lubricants containing it, will be found in the Journal of the Chemical Society, vol. xxvi. pp. 304, 305, and 1175. 2 The presence of resin acids in the rosin oil would alter its solubility, and also make the determination of the acetic acid inaccurate. It would be better to neutralise the greater part of the acetic acid, dilute with water, and extract the rosin oil by agitation with ether. VOL. II. 2 G 466 DETECTION OF KOSIN OIL. glacial acetic acid, while a sample of crude rosin oil of T0023 specific gravity showed a solubility of 16*87 per cent. 1 The solu- bility of a mixed sample does not, however, increase regularly with the proportion of rosin oil present. D e m s k i and M o r a w s k i (Dingl. Polyt. Jour., cclviii. 82) recommend the use of acetone for the detection and rough deter- mination of rosin oil in mineral oils. According to these chemists, rosin oils are miscible with acetone in all proportions, while mineral oils require several times their volume of acetone to effect solution. The test is applied by agitating 50 c.c. of the sample with 25 c.c. of acetone. If, on allowing the mixture to stand, it separates into two layers, 10 c.c. of the upper or acetonic layer should be removed with a pipette and evaporated, and the residual oil weighed. In the case of pure American or Galician lubricating oil the residue will weigh about 2 grammes, but only half this quantity will be obtained from Wallachian or Caucasian oil. The relative proportions of mineral and rosin oils in the residue may be deduced from its specific gravity as determined by Hager's method (page 85). The proportion of rosin oil which requires to be added to the sample to render the mixture permanently miscible with lialf its measure of acetone is next ascertained. The beginning of complete solution is always indicated by the formation of a rela- tively persistent froth on shaking. It is stated that mixtures of rosin oil with the lubricating oils from American and Galician petroleum are permanently soluble in half their volume of acetone if the proportion of rosin oil exceeds 35 per cent, of the mixed oil, but that complete solution is not effected in the case of Wallachian and Caucasian oils unless the rosin oil constitutes at least 50 per cent, of the mixture. Ragosine cylinder oil requires an addition of rosin oil equal to 53 per cent, of the mixture to become soluble in half its volume of acetone. The results of the test will doubtless be affected in a sensible manner by the character of the rosin oil employed. AND ITS HOMOLOGUES. Benzene is the lowest and most important member of a series of homologous hydrocarbons occurring in coal-tar and some analogous products. Coal and Russian petroleum-residues are now distilled with special reference to the production of benzene and allied hydro- carbons. The composition of the hydrocarbons of the benzene series is expressed by the generic formula C n H 2n -6 or C n H 2n -7.H. The hydrocarbons of the benzene series diminish in volatility Imt increase in density with the number of carbon-atoms present. As a rule they behave as saturated molecules, or the hydrides of PARAFFENES. 467 alcohol radicals, but they are not incapable of forming additive-com- pounds. 1 The members of the benzene series present very close resem- blances both in their physical and chemical characters, and hence, with the exceptions specified below, the description given of ben- zene on page 470 et seq., may be regarded as of general applica- bility to the other hydrocarbons of the series. The homologues of benzene may be regarded as being produced by the substitution of the group methyl, CH 3 , or one of its homo- logues, for one or more of the six hydrogen-atoms of benzene. At present, however, no more than four atoms of hydrogen have been thus displaced, and h e x y 1, C 6 H 13 , is the highest alcohol-radical which has been thus introduced. 2 1 These additive-compounds are formed not only with chlorine and bromine but also with hydrogen. Thus by the prolonged treatment of benzene with a saturated solution of hydriodic acid, under high pressure, W r e d e n (Annalen, clxxxvii. 166) obtained hex ah ydr oben zene, C 6 H 6 .H 6 , a body isomeric with hexylene. Toluene and xylene behave in a similar manner, the assimilation of hydrogen taking place with greater facility with an increase in the number of carbon-atoms in the hydrocarbon. Thus isoxylene, C 8 H 10 , may be com- pletely converted into thehexahydride, C 8 H 16 , by the action of hydriodic acid and amorphous phosphorus under conditions which cause no change in benzene and toluene. The following table shows the specific gravity and boiling points of the hexahydrides of the hydrocarbons of the benzene series : Formula. Boiling Point ; 0. Specific^Gravity. C fi H 10 69 0760 atOC. C 7 H U 97 0772 0758 at 20 C 8 H 16 118 0781 ,, 0765 at 20 C 9 H 18 135-138 0790 (?) C' 1n H 9n 153-158 0-802 0788 at 23 Compared with water at C. For these interesting bodies the generic name paraffene has been suggested, in allusion to their analogy to the true paraffins. The paraffenes behave in many respects like saturated hydrocarbons, being incapable of forming addi- tive-compounds, offering great resistance to the action of oxidising agents, and, when yielding, splitting up completely, with formation of carbon dioxide and water as the chief products. They are not acted on in the cold by bromine, fuming sulphuric acid, nor strong nitric acid ; but by fuming nitric acid, or a mixture of nitric and sulphuric acids, they are converted into the uitro-com- pounds of the benzene hydrocarbons. The paraffenes are either isomeric or identical with thenaphthenes which have been found largely in Caucasian petroleum, and are present also in American petroleum (see page 365). 2 Kekule's theory of the constitution of benzene has now received so much corroboration as to be raised from the position of a most valuable work- ing hypothesis to an approximation to the actual truth. Although the actual kind of bond is still somewhat an open question, chemists are practically agreed that in the molecule of benzene three of the four affinities or bonds of 468 THEORY OF THE BENZENE RING. The table on pages 354, 355, shows the hydrocarbons of the benzene series, the presence of which has been observed in coal tar and other products of destructive distillation. Further details respecting the individual members of the series will be found in the following sections. It is remarkable that all the homologues of benzene, the pre- sence of which in coal tar has been certainly recognised, are bodies in which one or more of the atoms of hydrogen of benzene are replaced by methyl, CH 3 . Hydrocarbons in which the homo- logues of methyl occur are producible by synthetical means, but each carbon-atom are satisfied by other carbon-atoms of the same molecule, the fourth being satisfied by atoms of hydrogen. This statement receives graphic illustration in the following diagram, due to Glaus, which is modified from that previously proposed by Kekule. 1 C H H-C 6 H-C 5 2 C H 'C H Each of the hydrogen-atoms of the benzene molecule is replaceable by simple and compound radicals, and upon the relative positions of these replacements depends the formation of the isomeric ortho-, para-, and meta- compounds of the aromatic series. When only one of the hydrogen-atoms is replaceable, its position is a matter of indifference, and hence phenol, C 6 H 5 .OH ; aniline, C 6 H 5 .NH 2 ; n it robe n z en e, C 6 H 5 .N0 2 ; monoch 1 orobe n- zene, C 6 H 5 .C1; and toluene, C 6 H 5 .CH 3 , are bodies of which no isomers exist. But when two hydrogen -atoms are replaced they may be either two adjacent atoms, two opposite atoms, or two alternate atoms. It is usual to number the positions from the top of the diagram, proceeding in the direction taken by the hands of a watch. This procedure is of course arbitrary, and hence a body of which the replaced hydrogen-atoms were the first and second would be identical with onfe in which they were first and sixth, or, in short, any two adjacent. Such products are called the ortho- modifications ; the term would be preferably applied to those bodies in which the opposite (first and fourth) hydrogen -atoms were replaced, and which therefore have a a more symmetrical structure, but which are those known as para- modifica- tions. When the first and third or first and fifth atoms are replaced, meta- compounds are produced. For the sake of simplicity it is usual to represent ORTHO-, PARA-, AND META- COMPOUNDS. 469 do not appear to occur in coal tar. 1 It is also doubtful whether coal-tar oils contain any higher homologues of the benzene series than tetramethyl-benzene. The light oil from coal tar, known as commercial " benzol," consists chiefly of a mixture of benzene and its homologues in very variable proportions. The method of assaying it is described on page 491. The characters of benzene and its immediate homo- logues are described in separate sections. Benzene, Phenyl Hydride. C 6 H 6 = C 6 H 5 .H. The term benzol is one frequently applied to the hydrocarbon benzene, but when used at all it should be strictly limited in its application to the mixture of homologous hydrocarbons obtained benzene by a simple hexagon, and its derivatives by attaching the formulae of the replacing radicals to the angles, while the empty corners are understood to be occupied by hydrogen-atoms. Thus the three isomeric xylenes (dimethyl- benzenes) are named and represented as follows : CH 3 Ortho-dimetliyl- Para-dimethyl- Jfete-dimethyl- benzene (1:2). benzene (1:4). benzene (1:3). It is evident that an isomer of the true xylenes, C 6 H 4 (CH 3 ) 2 , exists in ethyl- benzene, C 6 H 5 (C 2 H 5 ), in which only one of the hydrogen-atoms of the benzene nucleus is replaced. When more than two atoms of hydrogen are replaced, the number of possible isomers becomes enormously increased, especially when two or more different radicals are substituted. The following is an example of the nomenclature and method of representing the constitution of a body of this class. The hydroxyl atom is always supposed to occupy No. 1 angle : OH S0 2 H Orthobromo-orthonitro-phenol-parasulphonic acid, C 6 H 2 Br(N0 2 ).OH.S0 3 H. 1 Cymene, C 10 H 14 , however, which appears to be a methyl-parapropyl ( OTT ( ^ benzene, C 6 H 4 j p jf /'\> is not improbably present in coal tar, as is also the higher homologue c e d r e n e, C 15 H 24 . 470 PREPARATION OF BENZENE. from light coal-tar oil, of which benzene, C 6 H 6 , is the most important constituent. Benzene is produced by a great number of reactions, among which are the following : 1. Molecular change of acetylene at a red heat : 3C 2 H. 2 = C 6 H (5 . 2. Distillation of benzoic acid with slaked lime : C^IL 6 2 -}- CaH 2 2 = CaC0 3 + H 2 + C 6 H 6 . * 3. Distillation of phthalic acid with excess of lime : C 8 H 6 4 + 2CaO = 2CaC0 3 + C 6 H 6 . 4. Action of highly-heated zinc-dust on phenol: C 6 H 6 + Zn = ZnO + C 6 H 6 . Benzene also results from the heating of various hydrocarbons and other organic bodies, and is produced by the destructive distil- lation at a high temperature of turf, wood, resin, coal, &c. It occurs naturally in certain petroleums. In practice, benzene is obtained from the portion of coal tar which distils below 100 C., which is technically known as "light oils." To prepare pure benzene the oil is agitated successively with dilute sulphuric acid, water, and milk of lime or caustic soda solu- tion. It is next digested, at 100 C., with 5 per cent, by measure of concentrated sulphuric acid for several hours, in order to separate thiophene and hydrocarbons of the olefin and acetylene series, and this treatment is continued as long as fresh quantities of acid con- tinue to blacken it. The purified product is then separated and fractionally distilled, the portion which passes over below 90 C. being collected separately. This is cooled by a freezing mixture, when the benzene crystallises out, and is separated from, the more fusible hydrocarbons by draining on a vacuum-filter. If a pure product be required the benzene is melted and recrystallised several times, the mother-liquor being separated as before. Pure benzene is a colourless, very limpid, highly refractive liquid, of a peculiar and somewhat agreeable odour. When sub- jected to a freezing mixture it solidifies to a brilliant white mass of fern-like tufts, which melt at 5 '5 C. Benzene boils without de- composition at 80*5 C., emitting a highly inflammable vapour, which burns with a luminous and very smoky flame. Benzene is practically insoluble in, though it communicates its odour to, water, but it is miscible (apparently in all proportions) with alcohol, amyl alcohol, ether, chloroform, petroleum spirit, turpentine, absolute carbolic acid (see page 388), and fixed and volatile oils. Hot benzene dissolves sulphur, phosphorus, and iodine. It is 1 Benzene is obtained by heating any of the benzene-carboxylic acids with excess of a strong base. PROPERTIES OF BENZENE. 471 an excellent solvent for gutta-percha and india-rubber, and leaves them unaltered on evaporation. It dissolves waxes, fats, and fatty acids with facility. The following are determinations of the specific gravity of benzene : Source of Benzene. Density. Temperature ; C. Observer. '8991 Kopp. 8957 Warren. 8820 15 Benzoic acid '9002 Adrieenz. - 8846 15 8689 30 8133 80 Coal tar, '9012 ,, 8850 15 Nickels. Benzene may be heated to 400 C. in a sealed tube without change ; but when passed through a tube heated to a bright red- ness it yields hydrogen, together with diphenyl, C 12 H 10 , and other hydrocarbons. Benzene is not acted on by distilling it with metallic sodium, and caustic alkalies have no effect on it. Benzene dissolves entirely when heated to 100 C. for some hours with four or five times its volume of concentrated sulphuric acid. The resulting liquid contains benzene-sulphonic acid, C H 5 HS0 3 , and is colourless if pure benzene be employed. At very high temperatures, or when fuming sulphuric acid is em- ployed, the product contains more or less benzene-disul- phonic acid. Under the influence of oxidising agents benzene yields a number of interesting products, according to the treatment to which it is subjected ; thus : a. By the action of chromic oxychloride on a solution of ben- zene in glacial acetic acid, trichloroquinone, C 6 HC1 3 2 , is formed. b. By the action of manganese dioxide and concentrated sulphuric acid, benzene yields carbon dioxide, formic acid, and water, together with small quantities of benzoic, phthalic, and terephthalic acids. c. By the action of concentrated nitric acid, benzene is readily converted into nitro-benzene, C 6 H 5 N0 2 ; and by the continued action of the acid, especially if hot or mixed with sulphuric acid, dinitro-benzene, C 6 H 4 (N0 2 ) 2 , is produced. 1 1 The influence of the strength of the nitric acid employed, and the time allowed for the reaction, on the extent of the nitrofication of benzene has been studied by P. Spindler (Ber., xvi. 1252; Jour. Chem. Soc., xliv. 975; Jour.'iSoc. Chem. Ind., ii. 373).,. 472 ISOLATION OF BENZENE. By the action of chlorine or bromine in the dark or diffused light, benzene is converted into chlorinated orbrominated derivatives, in some cases five out of the six atoms of hydro- gen being replaced. In direct sunlight, chlorine and bromine form additive-compounds with benzene, of which benzene hexachloride, C 6 H 6 C1 6 , is a type. Iodine alone has no action on benzene, but when a mixture of benzene with iodine and iodic acid is heated, iodobenzenes are formed. By prolonged treatment with hydriodic acid, under high pressure, benzene is converted into hexahydrobenzeiie, C 6 H 6 . H 6 , a body isomeric with hexylene (see footnote on page 467). SEPARATION AND RECOGNITION OP BENZENE. When in a pure state and in tolerable quantity, benzene is readily recognisable by its smell, specific gravity, and boiling point. The chemical tests for benzene capable of ready application are very few, the most satisfactory being that based upon the formation of nitrobenzene by treatment with nitric acid, followed by recognition of the aniline resulting from the action of reducing agents on the nitro-compound. This test is only applicable when the benzene is in a state of approximate purity, or at least free from certain kinds of admixture. Hence in the case of complex mixtures one or all of the following means must be adopted to separate the benzene from interfering bodies : 1. The liquid should be agitated with solution of caustic soda, and separated from the aqueous layer. This treatment removes phenols and other bodies of an acid character. 2. The purified oily liquid should be separated from non- volatile matters by distillation in a small retort or flask furnished with a thermometer and good condensing arrangement. The portion passing over between 65 and 100 C. will contain any benzene which may be present, and should be collected separately and treated as follows : 3. The fraction passing over between 65 and 100 C. is shaken with a small quantity of cold concentrated sulphuric acid, and the treatment repeated, if necessary, with successive small portions of acid till no further blackening ensues. Thiophene and hydro- carbons of the ethylene and acetylene series are thus removed. 1 4. The purified oil is separated from the acid and washed by agitation with dilute caustic soda solution. 1 If at this stage the liquid be warmed with excess of concentrated sulphuric acid, and the acid liquid separated, heated to 180 to 200, and a current of steam passed through it, the benzene and its homologues which had dissolved as sulphonic acids will be completely recovered in a nearly pure condition. RECOGNITION OF BENZfcSE./ ' 473/ ^^1^=^ 5. The product of the last operation should nexTBe'fe'distilled in an apparatus provided with a dephlegmator, and the fraction passing over between 78 and 84 C. collected separately, and, if thought desirable, again fractionated, the portion distilling between 80 and 82 being collected separately. The product will consist of benzene, probably mixed with more or less of other bodies having approximately the same boiling point, those most likely to be present being thiophene, carbon disulphide, toluene, and benzene hexahydride. 6. The first of these may be removed by prolonged treatment with concentrated sulphuric acid, 1 and the second by alcoholic potash (see page 491), while the remaining bodies may be further separ- ated by again fractionally distilling, and remain liquid on exposure to a temperature of C., while benzene solidifies at that tempera- ture. When present in but small proportion in a mixture of volatile bodies the foregoing process wholly fails to isolate the benzene present, and in many other cases it is unnecessary to obtain the hydrocarbon in a state of absolute purity in order to demonstrate its presence. As a rule, it is sufficient to treat the partially purified substance resulting from process 4 for nitrobenzene as described below. The benzene, having been concentrated and obtained more or less pure in the manner above described, is next treated with about twice its measure of fuming nitric acid of 1'50 specific gravity. The operation is conducted in a small flask or retort furnished with an inverted condenser. If a vigorous action occur no extraneous heat need be applied, but if the reaction be sluggish the liquid should be well agitated and moderately heated for a few minutes. The flask is then cooled and the contents transferred to a tapped separator. If separation into distinct strata occur, all except the top one 2 are run off" while still warm through the tap into a quantity of cold water. If this liquid remain clear no nitrobenzene can have been formed, and consequently no benzene can have been present. 1 To purify large quantities of benzene from thiophene, C. Willgerodt passes a current of chlorine for four hours, the liquid being cooled with ice and the operation conducted in the dark. After distillation, the product is found to be free from thiophene. Small quantities may be treated with bromine- water till yellow, distilled, and the distillate agitated with soda. 2 In the case of mixtures of petroleum spirit and benzene, three layers are formed, the uppermost consisting of unaltered paraffins, the middle one of nitrobenzene, and the lowest of a solution of nitrobenzene in nitric acid. If the proportion of benzene in the mixture be moderate, the mtro-compound produced remains wholly in solution in the nitric acid until the latter is diluted. 474 DETERMINATION OF BENZENE. In presence of a considerable quantity, a distinct separation of yellow oily nitrobenzene will occur at the bottom of the water, and a marked odour of bitter almonds will be perceived. "With smaller quantities, the nitrobenzene will form a finely-divided pre- cipitate, which will collect after some hours at the bottom of the vessel. The liquid is passed through a wet filter, washed with cold water, and the nitrobenzene collected is dissolved by dropping alcohol on the filter. The alcoholic solution thus obtained is then treated with zinc and hydrochloric acid in the manner described on page 477, and the resultant aniline detected by bleaching powder. For the determination of benzene in complex mixtures, the only available method is to separate fixed matters, purify by treat- ing with acid and alkali, as already described, then to remove any carbon disulphide by alcoholic potash (see page 491), and subse- quently to carefully fractionate the purified hydrocarbons in a bulb- apparatus, as directed on page 501. The product may then be converted into nitrobenzene as described on page 494, the latter body being dissolved in strong sulphuric acid and any residual hydrocarbons deducted from the apparent benzene previously found. For the determination of benzene and its homologues in the liquid obtained by compressing the gaseous hydrocarbons obtained by subjecting petroleum to a red heat, as in the Pintsch system of light- ing railway carriages, C. G. Williams rejects the portion dis- tilling below 6 5 '5, and treats the remainder with its own measure of commercial nitric acid previously diluted with an equal bulk of water. On distilling the mixture at 100, the benzene and its homologues readily come over, while the olefins are converted into compounds which remain in the still. COMMERCIAL BENZENE. The benzene of commerce varies in purity from an article containing only insignificant proportions of other bodies, to the " 90," " 50," and " 30 " per cent, benzols of the tar distiller. 1 The composition and methods of assaying these products is described in a subsequent section (page 488 et seq.). Benzene is now manufactured of such purity in Germany, and by more than one firm in England, that 95 to 98 per cent, will distil within 1 C. of the theoretical boiling point. The assay of such products is conducted by more rigid methods than these em- ployed for ordinary benzols. Thus the distillation is conducted on 1 Commercial benzol when sold retail is sometimes entirely replaced by petroleum spirit or "benzoline." Shale naphtha may also be substituted. These products are readily distinguished from the coal-tar product by the tests, described on page 388. THIOPHENE. 475 100 c.c., which is fractionated in a flask with side-tube, the bulb of the thermometer being adjusted so as to be just below the tubulure. In some cases, and in conformity with Continental contracts, commercial benzene is subjected to the following special tests : (a) 1 c.c. of the sample is agitated with 20 c.c. of pure concen- trated sulphuric acid in a small stoppered bottle, and allowed to stand some hours. The colorisation at the end of this time should be very slight, never exceeding a pale straw-yellow, (b) 10 c.c. of the sample is agitated in a stoppered bottle with successive small quantities of saturated bromine water, until a yellow tint is obtained which persists for some minutes. iSTot more than 0'5 c.c. of bromine water should be required to produce this result. THIOPHENE, C 4 H 4 S. The purest commercial benzene from coal tar has been proved by Victor Meyer to contain about J per cent, of a sulphuretted body of the above formula, resembling benzene very closely both physically and in its chemical relationships. 1 In a pure state, thiophene is a colourless, very mobile liquid, boiling at 84 C., and having a density of 1'07 at 15 C. It is not miscible with water, and is not attacked by alkalies or alkali- metals. With concentrated sulphuric acid it forms a sulphonic acid and by nitric acid is oxidised very rapidly. Mono- and dinitro- thiophene have, however, been obtained, and are present in the purest commercial nitrobenzols (see page 479). By bromine it is converted into monobrom-thiophene, boiling at 150 and having a density of 1'652 at 23 ; or by a larger quantity into dibrom-thiophene, C 4 H 2 Br 2 S, which is a colourless liquid boiling at 211 and of 2'147 specific gravity at 23. In its re- actions this body closely resembles thiophene. 1 Thiophene is isolated from the purest commercial coal-tar benzene by agitating a large quantity of the latter with 10 per cent, by measure of con- centrated sulphuric acid, separating the acid liquid, diluting it with water and saturating it with carbonate of lead. The solution of the soluble lead thio- phene-sulphonate is evaporated to dryness, the residue mixed with one fourth of its weight of ammonium chloride, and distilled. The distillate is agitated with water and then with a strong solution of caustic potash, to sepa- rate rnercaptans, and is then dehydrated with calcium chloride and distilled The distillate still contains an admixture of benzene which may be separated by dissolving it in 100 times its measure of purified petroleum spirit and shak- ing the liquid with 10 per cent, by measure of sulphuric acid, preparing the lead sulphonate, distilling with ammonium chloride, &c., as before. An alter- native method of purification is to treat the impure substance with an insuffi- cient quantity of bromine, which forms dibrom thiophene, C 4 H 2 Br 2 S > and this may be obtained pure by fractional distillation. 476 REACTIONS OF THIOPHENE. Many of the colour-reactions of commercial benzene and toluene are really due to the presence of thiophene. This is true of the brown colour produced on agitation with strong sulphuric acid, and especially the reaction observed by Laubenheimer (Ber., viii. 224). To apply this test, a dilute solution of phenanthraquinone in glacial acetic acid is treated with a few drops of the liquid to be examined, the mixture well cooled, and concentrated sulphuric then added drop by drop, the resulting solution after a few minutes being treated with water. A colouring matter separates out, which, on agitation with chloroform, dissolves with a fine green coloration. 1 Another highly characteristic reaction is the deep blue coloration, due to the formation of indophenin, which is produced on agitating thiophene with isatin and strong sulphuric acid. If the mixture be warmed, the same reaction is produced by many of the derivatives of thiophene, including dibrom thiophene, thiophene- sulphonic acid, C 4 H 3 S.S0 3 H, and thiophenic acid, C 4 H 3 S.COOH. 2 The purple reaction of dinitrobenzene with alcohol and potash is due to the presence of nitro- or dinitro- thiophene (see page 479). Methyl-thiophene or thiotolene, C 5 H 6 S, is contained in im- pure toluene, from which it is isolated with difficulty as a colour- less liquid boiling at 113 C. 1 Dimethyl-thiopliene, or thioxene, C 6 H 8 S, is also present in coal-tar naphtha. NITROBENZENE, C 6 H 5 X0 2 . Nitrobenzene, sometimes called " nitrobenzol," is a product of the action of nitric acid on benzene, C 6 H 6 + HN0 3 =C 6 H 5 N0 2 + H 2 0. The nitric acid should not be of lower gravity than 1'45, and on the large scale is employed in admixture with sulphuric acid. Great heat is evolved, and more or less red fumes are produced. When the action is over the product may be poured into water, when the nitrobenzene sinks to the bottom as a yellow oil. 3 Pure nitrobenzene is a pale yellow liquid, having an odour closely resembling that of the essential oil of bitter almonds 4 or benzoic aldehyde, C 7 H 6 0, but differs from that body in 1 M e t h y 1-t li i o p h e n e behaves similarly to thiophene with phenanthra- quinone, but the colouring matter dissolves in ether with violet-red colour. 2 Pyrroline, C 4 H 5 N = C 4 H 4 .NH, gives the indophenin reaction, probably in consequence of its analogous constitution to thiophene. 3 Nitrobenzene and dinitrobenzene are now manufactured by passing coal gas through strong sulphuric acid, and then through a mixture of strong nitric acid with excess of sulphuric acid. This absorbs the benzene, with formation of the nitro-compounds (Jour. Soc. Chem. 2nd., iv. 475). * Nitrobenzene is employed extensively as a scenting and flavouring agent under the name of "Essence d e M i r b a n e." REACTIONS OF NITROBENZENE. 477 many respects besides chemical composition. Pure nitrobenzene has a density of 1'200, and boils at a temperature of 212 to 213 C. When cooled below 3 it crystallises in prisms. Nitrobenzene is nearly insoluble in water, but dissolves in nitric acid, being reprecipitated on dilution. It is readily soluble in alcohol, and is miscible in all proportions with ether, benzene, and oils. Nitrobenzene is a body of great stability, being unattacked by chlorine or bromine even at its boiling point, unless iodine or anti- monic chloride be simultaneously present. By treatment with sulphuric and the strongest nitric acid, nitro- benzene is converted into a mixture of three isomeric dinitro- benzenes, C 6 H 4 (N0 2 ) 2 . These form pale yellow crystals. Nitrobenzene is scarcely affected by aqueous alkalies, even when boiling, but is converted by alcoholic potash into a mixture of azobenzene, (C 6 H 5 ) 2 N 2 , and azoxybenzene, (C 6 H 5 N) 2 0. Under the influence of reducing agents, e.g., sulphuretted hydrogen, zinc and hydrochloric acid, or acetic acid and iron filings, nitrobenzene is converted into aniline, C 6 H 5 .H 2 N, the production of which affords one of the most delicate and charac- teristic tests for nitrobenzene. The alcoholic solution of the nitro- benzene should be mixed with hydrochloric acid and boiled for some time with metallic zinc. The liquid is next diluted, neutral- ised with caustic soda, and a clear solution of bleaching powder cautiously added. A blue or purple coloration, often appearing somewhat slowly and gradually changing to brown, will be pro- duced if aniline, resulting from the reduction of nitrobenzene, be present. According to Balls, magnesium ribbon, with the addition of a few drops of solution of platinic chloride, rapidly and completely reduces nitrobenzene in alcoholic solution to aniline, giving a solution which can be at once decanted and tested with bleaching powder (Jour. Soc. Chem. Ind., ii. 232). The following methods of detecting small quantities of nitro- benzene are due to Jacquemin (Jour. Pharm. Cliim., [4], xxii. 375 and 455 ; Jour. Chem. Soc., xxix. 776). A single drop of nitrobenzene dissolved in 20 c.c. of alcohol is stated to suffice for all three tests: a. The liquid is treated with zinc and sulphuric acid to reduce the nitrobenzene to aniline. The liquid is treated with excess of sodium carbonate and filtered; to the filtrate one drop of carbolic acid is added, and then some sodium hypochlorite, when a brown coloration, rapidly changing to blue, due to formation of sodium erythrophenate, indicates the presence of nitrobenzene. b. The liquid is treated with some dioxide of lead. If excess of the oxide be used, a rose tint, changing to brown, is developed, 478 POISONING BY NITHOBENZENE. but otherwise the rose colour changes to blue. The reaction is said to be very delicate. c. A crystal of potassium chlorate is added to the liquid, and a drop of concentrated sulphuric acid allowed to run down the side of the tube, when a violet coloration is produced. Toxicological Detection of Nitrobenzene. The symptoms pro- duced by nitrobenzene, when taken either in the liquid or the gaseous state, show that it is an active poison of a peculiarly insidious nature. For the most part its action is that of a power- ful narcotic, and as a rule it produces but little local irritation of the stomach or bowels. 1 Its vapour may prove injurious even when largely diluted with air. The post-mortem appearance of the stomach is normal, but the smell of the poison will usually be perceptible, unless death has ensued by inhalation of the vapour. The brain is always congested, and the blood everywhere black and thick, but fluid, the heart being full of dark treacly blood. There is usually well-marked and long-continued rigidity. In cases of delayed death, nitrobenzene may be smelt or found on analysis, owing to its reduction to aniline, which will be met with in the brain and urine. In many cases a distinct colour will be observed on the skin, at least in some parts. The poisonous effects of nitrobenzene are identical with those of aniline, and are most probably due to the reduction of the nitro- benzene to that substance in the body. For the detection of nitrobenzene, the portions of the body to be examined should be reduced to fragments and acidulated with dilute sulphuric acid. The liquid is distilled, and the distillate examined from time to time, with the view of detecting the presence of any unchanged nitrobenzene. Then treat the contents of the retort with rectified spirit of wine, and filter. Precipitate the filtrate with excess of basic lead acetate, and again filter. Kemove any lead from the liquid by adding a slight excess of sodium sulphate. Evaporate the filtered liquid nearly to dryness, and render the 1 The first symptoms are usually headache and drowsiness, followed by flushing of the face, difficult breathing, irregular pulse, dilation of the pupils, more or less loss of voluntary power, and sometimes convulsions. On at- tempting to walk, the poisoned person will sometimes reel as if drunk, and the breath will smell of nitrobenzene. These symptoms are followed by coma, which may come on slowly, but is more frequently sudden, increasing in intensity till death ensues in five or six hours from the commencement of the symptoms. "When the stage of coma is reached there is but little ohance of preventing a fatal termination of the case. On the whole, the symptoms of poisoning by nitrobenzene simulate those of apoplexy ; but the strong and persistent odour and the intense salivation it is apt to produce sufficiently dis- tinguish it from the latter affection. COMMERCIAL NITROBENZOL. 479 solution alkaline with sodium carbonate. Then agitate with ether to dissolve the aniline, run off the aqueous liquid, and agitate the ethereal solution with a little very dilute sulphuric acid. Separate this, which will contain any aniline as sulphate, concentrate by evaporation at a low temperature, and test for aniline by bleaching powder solution as described on page 477. Commercial Nitrobenzol. The products obtained on a large scale by the action of nitric acid on commercial benzols (page 493) vary in composition with the character of the benzols employed in their manufacture, but are often exceedingly complex, containing simultaneously several isomeric varieties of the different mono- and di-nitro-derivatives of the benzene series of hydrocarbons, which diminish in volatility and fusibility with the number of atoms of carbon or nitryl, N0 2 , contained in them. By the action of reducing agents the various nitro-compounds yield aniline and other bases, the constitution of which depends on that of the nitro-com- pounds from which they are derived. Some of these yield colour- ing matters materially differing in shade or brilliancy from those given by purer products. The presence of hydrocarbons in nitrobenzol may be detected by dissolving 30 c.c. of the sample in 70 c.c. of concentrated sul- phuric acid, in which it ought to be entirely soluble. Commercial nitrobenzene and dinitrobenzene commonly contain the nitro-derivatives of thiophene. These impurities may be detected by dissolving the sample in alcohol, and adding a single drop of aqueous potash, when a deep red solution is obtained, a thin layer appearing violet. An excess of alkali destroys the colour, but it may be restored by cautiously neutralising (Jour. Soc. Chem. Ind., iv. 270). The specific gravity of nitrobenzol made from 90 per cent, benzene should be 1'186, and from 30 to 40 per cent, benzol 1*175 to 1'190. Crude nitrotoluol is described on next page. Toluene. Methyl-benzene, C 7 H 8 = C 6 H 5 CH 3 . Toluene, formerly called "toluol," a name which should be applied only to the impure commercial substance, is obtainable by various synthetical methods, and is a product of the dry distillation of tolu-balsam and many other resins, and is present to a considerable extent in coal-tar naphtha. Toluene is the next homologue of benzene, which body it closely resembles. The chief points of difference are : 1. The odour, which is distinct from that of benzene. 2. The specific gravity, which is '881 at or '871 at 15 C. 3. The boiling point, which is 111 C., and hence considerably higher than that of benzene. 480 TOLUENE. 4. The solidifying point, toluene remaining liquid even at 20 C., while benzene is solid at 0. By the action of concentrated nitric acid, toluene is converted into one or more nitrotoluenes, C 7 H 7 N0 2 , or d i n i t r o- toluenes, C7H 6 (]S"0 2 ) 2 ; but when boiled with dilute nitric acid it is oxidised with formation of benzoic acid, C 7 H 6 2 , and other products. Commercial nitrotoluol has a density of 1'167. Pure orthonitrotoluene has a gravity of 1'162, that of metanitro- toluene being 1*168. Paranitrotoluene is solid at the ordinary temperature. When treated with excess of hot concentrated sulphuric acid, toluene forms two isomeric t ol uene-sulph on ic acids, C 7 H 7 .HS0 3 , and on heating the liquid to 150 to 170, and passing a current of steam, these compounds are decomposed and the toluene distils over almost without loss. COMMERCIAL TOLUENE. Toluene constitutes the greater part of "50 per cent, benzol" (page 490), and also occurs to a considerable extent in "90 per cent, benzol." Toluene occurs in an approximately pure state in commercial " toluol," which is now manufactured on a large scale. When fractionated in the manner described on page 496, commercial toluols should give the first drop at 110 to 111, and 90 per cent. of distillate below 120 C. An almost pure toluene is now made commercially, which distils wholly within a degree or two of 110 C. XyleneS. Dimethylbenzenes. C 8 H 10 = C 6 H 5 .(CH 3 ) 2 . All three modifications of xylene (ortho-, para-, and meta-) occur in coal tar, though the isomeric body, ethyl-benzene, C 6 H 5 (C 2 H 5 ), has not been found therein. The isomeric xylenes present a close general resemblance to benzene and toluene, but are distinguished by their higher boiling points, inferior density, and the greater facility with which they are oxidised and are converted into sulphonic acids. They differ in these respects even among themselves, as will be evident on reference to the table on the following page. A method of separating the three xylenes from each other, and from their isomer ethyl-benzene, has been described by Friedel and Crafts (Compt. Rend., ci. 1218; Jour. Chem. Soc., 1. 229). The different behaviour of the isomeric xylenes with reagents has some practical interest as affording a means of examining the nature of COMMERCIAL XYLENE or XYLOL, which is now manufactured on ISOMERIC XYLENES. 481 fl d Ni Aci J8* o ^ o S 2 O O H f_ rfl ^OW Jill lilti P.O a PEI o ^! IS So PS i ^ tf g'i J J ? a|||l : b^a <~^~* ^ fco .1p!?l!i VOL. II. J5 H 482 COMMERCIAL XYLOL. a considerable scale for the preparation of cumidine (by heating the monomethyl-metaxylidine chloride with methyl-alcohol) and of azo-colouring matters (scarlets, oranges, &c.). Com- mercial xylene is obtained by the fractional distillation of coal-tar naphtha. It varies greatly in purity, giving 90 to 95 per cent, within a range of 2 to 6 from the first drop over. The distilling points may range from 136 to 138; 136 to 140; 136 to 142 ; 138 to 140; or 138 to 142 , 1 according to the stipulations of the contract-note. Besides varying proportions of the three isomeric xylene s, the properties of which have already been described, commercial xylol contains more or less of their lower and higher homologues (e.g., toluene, mesitylene, and pseudo-cumene), together with a notable proportion of paraffins, and probably styrolen e 2 and hydrocarbons of other series. The hydrocarbons of the ethylene and acetylene series are not improbably present in the fraction of crude naphtha from which commercial xylene is prepared, but they either suffer absorption by the sulphuric acid used for the purification, or are thereby polymerised so as to remain in the retort when the purified substance is redistilled. Ortho-xylene also undergoes absorption by the sulphuric acid employed, and hence the refined product contains a comparatively small proportion of this hydro- carbon, the same reaction having prevented its recognition in coal tar until recently. Thioxene, or dimethyl-thiophene, C 6 H 8 S, if present, will also be absorbed by treatment with sulphuric acid. On the other hand, any hexahydrometa- xylene (see footnote on page 467) and homologues of that body will behave in all essential respects like paraffins. Of all these constituents of commercial xylene, the metaxylene is the only one of value, even its two isomers being useless. 3 As the boiling point of a sample affords no indication of the propor- 1 In some cases the contract-note stipulates that 90 per cent, of the sample of xylene shall distil within a range of 1 C., and this behaviour is very strictly enforced. 2 STYROLENE, CINNAMENE, or Phenyl-ethylene, C 8 H 8 = C 6 H 5 .CH:CH 2 , occurs in small quantities in coal tar. It is a colourless, mobile oil, of '876 sp. gr., boiling at 145, but volatilising at ordinary temperatures. It is not acted on by caustic alkalies, but is converted by strong sulphuric acid into a solid polymer, which again yields styrolene on distillation. By fuming sul- phuric acid it is converted into a sulphonic acid. Fuming nitric acid converts styrolene into a nitro-compound, and bromine and chlorine form additive- compounds. 3 If the metaxylene contain even a few units per cent of orthoxylene, on converting it into the nitro-derivative, and this into x y 1 i d i n e, tarry matters are formed, which are a serious inconvenience in practice. DETERMINATION OF METAXYLENE. 483 tion of the different isomers present, attempts have been made to devise other methods of assay. The difficulties attending the solution of this problem have not yet been completely surmounted, but a great advance has been made in this direction by T. Levin stein (Jour. Soc. Chem. Ind., iii. 77), who claims that the following method of assay affords results of sufficient accuracy for practical purposes, and is at any rate of great assistance in valuing commercial xylols. For the determination of the metaxylene^ 100 c.c. of the sample should be treated with an equal measure of dilute nitric acid, made by mixing 40 c.c. of acid of 1'40 specific gravity with 60 c.c. of water. The mixture is heated to 100 C. for about an hour, and well agitated at intervals. The liquid is then poured into a separator, the lower acid layer drawn off, and the hydrocarbons transferred to a flask, treated with excess of caustic soda solu- tion, and distilled with wet steam. 1 The distillate consists of metaxylene, paraffins, and water, the ortho- and para-xylene pre- sent in the original sample having been converted into toluic acids or nitro-compounds soluble in soda. The aqueous portion of the distillate is separated, and the hydrocarbons are measured and treated in a graduated tube with 1J times their volume of concentrated sulphuric acid of 1*845 specific gravity. The mix- ture is well agitated at intervals during half an hour, when the metaxylene will have dissolved in the acid, the paraffins remain- ing unaltered. By subtracting the measure thus obtained from that of the hydrocarbons, previously to treatment with sulphuric acid, the volume of metaxylene in 100 c.c. of the sample will be obtained. Exception has been taken to this process by Keuter and others, but Levinstein contends that, if the prescribed condi- tions are adhered to, the method is sufficiently accurate for practical purposes ; and it has been shown to yield fairly concordant results in the hands of different operators. For the determination of the paraxylene, 100 c.c. of the crude sample should be treated with 120 c.c. of cold concentrated sul- phuric acid in a graduated tube, and the mixture shaken at inter- vals during half an hour, or until no further solution of the hydro- carbons is observed to take place. It is advisable to cool the mixture. The ortho- and meta-xylene are converted into sulphonic acids, but on allowing the mixture to stand, the paraxylene and paraffins form an upper layer, which is separated and treated with an equal measure of fuming sulphuric acid containing 20 per cent, of anhydride. The mixture is heated on the water- 1 Repeated agitation of the undissolved oil with solution of caustic soda may be resorted to in place of the distillation. 484 XYLENE-SULPHONIC ACIDS. bath for a short time and allowed to settle. The paraffins now form the upper layer, and on deducting their volume from that of the mixed paraffin and paraxylene previously observed, the measure of the latter hydrocarbon may be ascertained. The pro- cess depends on the ease with which ortho- and meta-xylene are converted into sulphonic acids by the action of ordinary sulphuric acid, while the paraxylene is comparatively unaltered by this reagent under the conditions of the experiment, 1 but forms a sulphonic acid when heated witli the fuming acid, the paraffins remaining unchanged by either treatment. By maintaining the solution of the paraxylene-sulphonic acid at 180 to 200 C., w r hile a current of steam is passed through it, the paraxylene is regenerated, and may be separated from the aqueous portion of the distillate and measured. On exposing the fraction to a freezing mixture, the paraxylene crystallises, and may be further purified by pressure between folds of filter-paper. The same process of distillation with steam serves for the recovery of the ortho- and meta-xylene from their solution in the ordinary sulphuric acid. If it be desired to separate the paraxylene from the paraffins without converting the former into a sulphonic acid, the mixture of the two should be placed in a flask furnished with a condenser, and a current of wet steam driven through it. The portion which distils first should be separated from the water, and distilled by means of external heat up to 138. From the distillate thus ob- tained pure paraxylene can be crystallised out by subjecting it to a freezing mixture. The proportion of orthoxylene present in crude xylol may usually l>e ascertained with sufficient accuracy by deducting from 100 the sum of the paraxylene, metaxylene, and paraffins found by the foregoing processes. As, however, the whole of the error in these estimations falls on the orthoxylene, the results must not be re- garded as really accurate, besides which it must be remembered that other bodies than paraffins and the isomeric xylenes are present in greater or less amount. Levinstein finds the indications fairly satisfactory in the case of " unsophisticated crude xylene properly 1 J. Levinstein lias shown (Jour. Soc. CJiern. Iiid., iii. 354) that 100 c.c. of pure paraxylene could be dissolved by 150 c.c. of ordinary sulphuric acid, but that when mixed with paraffins and metaxylene, as in commercial xylol, it was practically unacted on. Thus, on agitating a mixture of 80 c.c. of metaxylene, 10 of paraxylene, 10 of paraffins from crude xylol, and 100 c.c. of strong sulphuric acid for several hours, 20 c.c. of the hydrocarbons remained undissolved, and on further examination was found to consist of 10 c.c. of -paraffins and 10 of paraxylene. DETERMINATION OF ORTHOXYLENE. 485 prepared from English gas-tar naphtha," as in such an* article there is usually no toluene present, and only small quantities of foreign compounds acted on by nitric acid. "When, however, it is desired to- prove definitively the presence of orthoxylene, he recommends that the following process should be employed : Treat 100 c.c. of the sample with ordinary concentrated sulphuric acid, in the manner described for the determination of paraxylene, separate the acid liquid containing ortho- and meta-xylene-sulphonic acids, and convert these into their calcium and then into their sodium salts. On con- centrating the solution of the latter, sodium orthoxylenesulphonate will crystallise in large flat prisms, while the meta-salt remains in. solution. The mother-liquor should be further concentrated, when a second crop of crystals will be obtained. Both crops are purified by resolution and recrystallisation to remove any of the meta-salt which may have separated owing to over-concentration. The indistinct crystals of this body are readily distinguished from the large well-defined crystals of the ortho-salt from English crude xylols. That from Scotch products crystallises far less readily, probably owing to an admixture of some foreign sulphonate. Crystallised sodium orthoxylene-sulphonate contains C 6 H 3 (CH 3 ) 2 . S0 3 Na -f 5H 2 . It is dried by pressure between folds of filter-paper, and then over sulphuric acid, when it can, if desired, be weighed. 1 The orthoxylene can be regenerated by adding excess of sulphuric acid and distilling in a current of steam at 120 to 150 C. The following figures are among those quoted by I. Levinstein as illustrating the results obtained on applying his methods to the analysis of samples of crude xylol : Percentage of No. Origin of Sample. Sp. gr. at 19 C. DisMllinjr Degrees; C. Meta- xylene. Para- xylene. Ortho- xylene. Paraffins. 1 From Manchester tar, 8629 134 to 140 87 6 4 3 2 From English tar, . 8660 138 to 141 79 3 15 3 3 From Scotch tar, 8574 134 to 140 72 8 12 8 4 From mixed English and Scotch tars, . 8605 134 to 141 81 10 3 6 5 From mixed English and Scotch tars, . ... 140 to 141 86 3 5 6 6 Unknown, ... 139 to 141 70 5 15 10 7 Pure metaxylene iso- lated by dilute nitric acid, &c., 8668 142 to 143 100 Probably it would be preferable to saturate the acid liquid with baryta- 486 COAL-TAR NAPHTHA. Samples 2 and 5 were analysed independently by the same method by A. Kademacher, with the following results : Number. Metaxylene. Paraxylene. Orthoxylene. Paraffins. 2 81 3 144 14 These results are very satisfactory, especially those indicating the proportion of metaxylene. In practice, the assay may usually be limited to this determination, though that of the paraxylene is readily made and affords a useful check. 1 Coal-Tar Naphtha. In the first distillation of coal tar, two fractions are obtained, known respectively as "first light oils" and " second light oils. 2 Sometimes they are not collected separately, in which case the fraction is known as "crude naphtha "or "light oi 1." CRUDE COAL-TAR NAPHTHA is a more or less fluorescent liquid, of a dark coffee colour, and disagreeable odour. It has a density of '840 to "940 or even higher, 3 and evolves ammonia abundantly on distillation. Crude naphtha is an extremely complex product, as will be seen on reference to the table on pages 354, 355. Many or all of the bodies boiling below about 220 C. are some- times present simultaneously in crude naphtha. Crude naphtha is usually submitted to redistillation without water, filter from the sulphate, and crystallise the sulphonates from the filtrate. Barium orthoxylenesulphonate crystallises in large nacreous laminae, requiring 3 parts of boiling or 18 parts of cold water for solution. 1 Renter (Ber. t 1884, page 2028) expresses doubt of the reliability of Levinstein's method, as it is difficult to act ou the ortho- and para-xylene by dilute nitric acid without more or less affecting the meta-xylene. Similarly, paraxylene is not unaffected by ordinary sulphuric acid, while fuming sulphuric acid must be employed in large excess to remove the last traces of xylenes from the paraffins. Reuter suggests no improvement on Levinstein's method. Watson Smith writes very favourably of Levinstein's method of determining metaxylene, but does not consider the direct isolation of orthoxylene, or of a sulphonate of that body, to be valuable as a quantitative indication. 3 Good "first light oils" or "first runnings" ought, on redistillation, to yield 10 per cent, below 100 C., and an average of 78 per cent, below 170 C. On again distilling the fraction collected under 130, fully 25 per cent, should come over under 100. " Second light oils" should have a density of about 975. It yields but little distillate below 120, and about 30 per cent, below 170 C. 3 The density of crude naphthas of London make usually ranges between *883 and '888, and that of Scotch naphthas from '868 .to '876, but the density is sometimes considerably outside these limits. ONCE-RUN NAPHTHA. 487 previous chemical treatment, the resultant products being "once- run naphtha" and "last runnings." 1 By some dis- tillers an intermediate product is obtained, termed "medium naphtha." It is the fraction of the crude naphtha which on redistillation passes over between 160 and 180 C. Benzene can be isolated in small quantity even from this fraction by the use of a dephlegmating arrangement. ONCE-RUN NAPHTHA is a fluid of a more or less amber-yellow colour and a specific gravity ranging from '886 to '892. The method of assaying once-run naphtha by distillation is described on page 504. Before redistilling once-run naphtha on a large scale it is purified by treatment with sulphuric acid of T845 specific gravity. This removes the bases, hydrocarbons of the ethylene and crotonylene series, and some of the higher homologues of benzene. A subse- quent treatment with milk of lime or caustic soda eliminates the phenols and any other bodies of acid character. The oil is then washed with water and again distilled. Once-run naphtha is the starting point from which the manu- facturer derives, by fractional distillation, the following products : 90 per cent, benzol; 50 and 90 per cent, benzol (called "50/90 benzol"); 30 per cent, benzol; solvent naphtha; burning naphtha; and a further quantity of last runnings. Each of these products has distinctive characters by which it is known and recognised both in England and on the Continent. In addition, benzene, toluene, and x y 1 e n e are now manufactured on a commercial scale in a condi- tion of almost absolute purity (see pages 474 and 480). BURNING NAPHTHA is a product similar to " last runnings," but results from a second distillation. It should have a density of 880 to '887, and gives 20 to 30 per cent, over at 150, and 90 at 170 C. SOLVENT NAPHTHA is so called from its wide application as a solvent for india-rubber in the manufacture of waterproof articles. It is also used for washing crude anthracene. It gives from 8 to 30 per cent, of distillate below 130 and about 90 below 160. The specific gravity should not exceed '875. Solvent naphtha has a 1 " Last runnings " are highly charged with naphthalene, and find an appli- cation as a common burning oil in street vapour-lamps. A sample examined by B. N i c k e 1 sjgave, on fractional distillation, 10 per cent, at 142 ; 20 at 146 ; 30 at 151; 40 at 157; 50 at 164; 60 at 170; 70 at 179; 80 at 191; and 90 at 209 C. When 70 per cent, had passed over, naphthalene appeared in quantity. By repeated fractioning, evidence of the presence of toluene, xylene, &c. , was obtained. 488 LIGHT STUFF IN BENZOLS. complex and variable composition, but consists chiefly of isomeric x y 1 e n e s and c u m e n e s, with a notable proportion of p a r a f - fins, and sometimes several units per cent, of naphthal- ene, the last constituent being considered very objectionable. Formerly, solvent naphtha comprised the whole of the fraction from the redistillation of once-run naphtha passing over above the benzols and below 160 C., but when a demand arose for xylene as a separate product, much of it was removed, with the result of rendering the residual solvent naphtha less suitable for its intended purpose. CARBURETTING NAPHTHA is a product consisting chiefly of xylenes. It is usually specified as giving at least 70 per cent, of distillate at 130 and 90 at 150, the specific gravity ranging from "850 to 870. COMMERCIAL BENZOLS. In commerce, the term "benzol" is applied generically to the more volatile portions of redistilled coal- tar naphtha. It is a convenient name to indicate this more or less complex liquid, consisting chiefly of benzene and its homologues ; while the use of the term benzene should be restricted to the definite hydrocarbon of the formula C 6 H 6 . Commercial benzols consist essentially of mixtures of very vari- able proportions of benzene and its homologues, together with: smaller percentages of carbon disulphide ; certain light hydrocarbons technically known as " petroleum," and which are incapable of nitrofication ; l thiophene and its homologues; traces of water ; very frequently acetylene, and probably homologous hydrocarbons; 2 and traces of other impurities of an indefinite nature. The light hydrocarbons diminish the yield of colouring matter 1 The nature of these light hydrocarbons is not fully made out, but Vin- cent has shown that they are almost wholly absorbable by bromine, and consist largely of amylene, C 5 H 10 . They are sometimes present to the extent of 8 or 10 per cent., being most abundant in the products from gas-works in which cannel coal is extensively used. (See also Watson Smith, Chem. News, xliv. 138, and Jour. Soc. Chem. Ind., iii. 80). B. Nickels has examined a sample of the so-called "light stuff" obtained in rectifying benzol on the large scale. The original density was "899, but this was reduced to '884 by repeated treatment with alcoholic potash (page 491), indicating the removal of 8 to 9 per cent, of carbon disulphide. On fractionating the purified liquid with a 6-bulb tube (page 501) a first fraction of a density of '857 was obtained, and 80 c.c. of this on again fractionating gave five fractions of 10 c.c. each, having the successive densities 760, '825, '858, "875, and '880, the 30 c.c. remaining undistilled having a density of '883. 2 By boiling such benzol rapidly, and passing the vapours into ammonio- nitrate of silver or ammoniacal cuprous chloride, an abundant precipitate of the corresponding metallic acetylide is obtained. COMMERCIAL BENZOLS. 489 from the aniline made from the benzols containing them, and, if present in considerable proportion, render the process of nitrofica- tion irregular and even dangerous. Carbon disulphide is a some- what troublesome impurity, and is difficult to get rid of by ordinary means. The details of the method of effecting the assay of benzols are given on page 496 et seq. According to the behaviour of the sample when distilled, it is classed as 90 per cent, benzol, 50 per cent, benzol, or 30 per cent, benzol. 90 per cent. Benzol is a product of which 90 per cent, by volume distils before the thermometer rises above 100 C. A good sample should not begin to distil under 80 C. and should not yield more than 20 to 30 per cent, at 85, or much more than 90 per cent, at 100 C. It should wholly distil below 120. An excessive dis- tillate, e.g., 35 to 40 per cent, at 85, indicates a larger proportion of carbon disulphide or light hydrocarbons than is desirable (see also page 500). The actual percentage composition of a 90 per cent, benzol of good quality is about 70 of benzene, 24 of toluene including a little xylene, and 4 to 6 of carbon disulphide and light hydrocarbons. The proportion of real benzene may fall as low as 60 or rise as high as 75 per cent. 90 per cent, benzol should be colourless ("water- white"), and free from opalescence. The specific gravity of English 90 per cent, benzols ranges from '880 to '888 l at 15'5 C. ( = 60 F.), but the density is a fallacious indication of the quality of a sample, owing to the presence of carbon disulphide and light hydrocarbons, which impurities, from their high volatility, become concentrated in this class of benzol. Carbon disulphide has the high density of 1'27, while the light hydrocarbons ("petroleum") average 0*860. Hence, when present together in certain proportions, these impurities do not sensibly affect the density of the benzol. Scotch 90 per cent, benzols contain but little carbon disul- phide, but a considerable proportion (7 to 8 per cent.) of light hydrocarbons ; hence the specific gravity is often as low as '870 or even less. 2 The first 20 per cent, distilled from such a sample may have a density of '866 ; while the residual 80 per cent, will be as dense as '872. The low density of the first fraction here distinctly indicates " petroleum," and not carbon disulphide, as the predomi- nant impurity. By eliminating the carbon disulphide from 90 per cent, benzol in the manner described on page 491, the anomaly in 1 "Watson Smith has described a 90 per cent, benzol from London tar which had a density of '900, and contained as much as 6 per cent, of carbon disulphide, after removing which the density of the benzol fell to '880. 2 Truby states that he has worked Scotch benzols having a density of '870. 490 COMMERCIAL BENZOLS. the density almost disappears, and the interpretation of the results of the fractional distillation becomes much simpler (see page 498). Until the last few years, 90 per cent, benzol was the highest quality in the market ; but, by improved methods of fractionating, products are now obtained at one operation which distil completely within a few degrees of the true boiling points of benzene, toluene, and xylene respectively. These products have already been de- scribed (pages 474, 480). 50 per cent, benzol, often called 50/90 benzol, is a product of which 50 per cent, by volume distils over at a temperature not exceeding 100 C., and 40 per cent, more (making 90 in all) below 1 20 C. It should wholly distil below 130. The density of English 50 per cent, benzol is about '878 to '880 and of Scotch '867 to 872. This class of benzol is nearly free from carbon disulphide, and contains comparatively little of the light hydrocarbons, while the proportion of toluene and xylene is of course larger than in 90 per cent, benzol. 50/90 benzol is employed for producing the heavy aniline used for preparing rosaniline or magenta. In the case of a benzol of intermediate character, the proportions of 90 and 50 per cent, benzol to which it corresponds may be found by the following rule : Deduct 50 from the percentage- volume of the sample distilling below 100, and multiply the difference by 2 '5. The product gives the percentage of 90 per cent, benzol in the sample, the difference between this and 100 being the proportion of 50 per cent, benzol. 1 For English benzols the rule is accurate to 1 per cent. SO per cent, benzol is a product of which 30 per cent, distils below 100, about 60 per cent, more passing over between 100 and 120. It consists chiefly of toluene and xylene, with smaller proportions of benzene, cumene, &c. The specific gravity should be about '875. For the manufacture of aniline-red, magenta, or fuchsine, a benzol is required which will yield (by nitrofication and subsequent reduction) an aniline oil of which three-fourths distils between 180 and 190, and the remainder between 190 and 215. Such an aniline oil is producible from a benzol of which three-fourths passes over between 80 and 100, and the rest between 100 and 130. For the manufacture of methyl-violet, on the contrary, an aniline as free as possible from higher homologues is required, and this must be made from a benzol which almost wholly distils below 83 or 84 C. For xylidine-red an aniline oil derived from 1 Thus a benzol giving 64 per cent, over below 100 corresponds to a mixture of 35 parts of 90 per cent, benzol with 65 parts of 50/90 benzol; for: 64-50 = 14; 14x2-5 = 35; and 100-35 = 65. ASSAY OF BENZOLS AND NAPHTHAS. 491 benzols boiling above 115 or 120 is required, but it is of ten found preferable to prepare this by fractionating an ordinary aniline oil rather than to employ a benzol of specially high boiling point for the purpose. The commercially pure xylene and toluene now largely manufactured (page 480) have largely replaced the high- boiling " benzols " formerly employed. Assay of Commercial Benzols and Naphthas. 1 The observations of importance in judging of the quality of a commercial benzol or naphtha are, in addition to the appearance and smell of the sample : its specific gravity ; its behaviour with concentrated sulphuric acid ; the proportion of carbon disulphide ; the proportion of the light hydrocarbons technically known as " petroleum " ; the proportion of nitrofiable hydrocarbons and its behaviour on fractional distillation. In the case of commercial xylols, the proportion of metaxylene should be ascertained in the manner directed on page 483. Commercial 90 per cent, benzol should not be diminished in volume by more than J per cent, when agitated with 5 per cent, by measure of cold concentrated sulphuric acid. For a more stringent test, applicable to commercially pure benzene, see page 475. Water, if present in such quantity as to render the sample turbid, must be got rid of prior to any further process of assay. This may be done sufficiently perfectly by passing the liquid through a dry filter. A complete elimination of the water may be easily effected by agitating the sample with a little recently gently ignited plaster of paris, and filtering. The dehydration is almost instantaneous. If a known weight of plaster be employed, and it be afterwards washed with a little gasolene, dried at a gentle heat, and reweighed, a quantitative estimation of the water may be readily effected. Carbon disulphide often exists in very sensible quantity in crude and once-run naphtha, and in 90 per cent, benzol. From the less volatile classes of benzol it is usually absent. Its presence is im- portant only in 90 per cent, benzol. Carbon disulphide may be eliminated from benzol, and its amount determined with a near approach to accuracy, by the following method devised by B. Nickels (Chem. Neivs, xliii. 148 and 250; Hi. 170) : 100 c.c. measure of the sample of benzol (preferably dehydrated with plaster of paris, as above described) is treated with a solution of 1 gramme of caustic potash in the smallest possible quantity (about 20 c.c.) of 1 For much valuable information in this section, and on coal-tar products generally, the author is indebted to Mr B. Nickels. 492 .DETERMINATION OF CARBON BISULPHIDE. hot absolute alcohol, 1 and the mixture agitated thoroughly. Tf carbon disulphide be present a yellow colour is usually developed, and the mixture becomes pasty from the formation and separation of potassium xanthate (vol. i. p. 137) in crystals of a characteristic silky appearance. The mixture is shaken at intervals during half an hour, and is then passed through a dry filter. 2 The adhering benzol is separated as far as possible from the precipitated xanthate by carefully folding the filter and pressing it against the sides of the funnel by means of a spatula. The filtrate is agitated in a cylindrical separator with its own volume of warm water, which removes the excess of alcohol and a little dissolved xanthate. The aqueous liquid is run off, and the benzol again agitated with its own measure of cold water, after the removal of which it may be dehydrated with plaster, and then further examined by fractional distillation (see page 498). 3 The potassium xanthate collected on the filter is washed with a little ether, dissolved in alcohol, and the solution obtained rendered slightly acid with acetic acid. On adding a solution of cupric sulphate, a brownish precipitate of cupric xanthate is formed, which rapidly changes to bright yellow cuprous xanthate, CuC 2 H 5 (CO)S 2 , insoluble in water and dilute acids (vol. i. p. 137). The cuprous xanthate may be collected on a filter, washed, ignited in the air, and weighed as CuO ; or the cupric oxide may be ignited with sulphur in hydrogen, and thus converted into cuprous sul- phide. The weight of CuO or Cu 2 S obtained, divided by "523, gives that of the carbon disulphide in the sample operated upon. 4 1 The alcohol used may be methylated. It may be rendered sufficiently an- hydrous by agitating it with a large excess of dry potassium carbonate, and decanting. 2 "When the quantity of solid xanthate formed is small, as is often the case with Scotch benzols, the filtration may be omitted and the xanthate removed by agitation with water. 3 If this is to be done, it is better to operate on a larger quantity of the original benzol, and it is safest to treat the purified benzol a second time with alcoholic potash. 4 Instead of weighing the cuprous xanthate, H. M a c a g n o (Chem. News, xliii. 138) titrates the acidulated solution of potassium xanthate with a solution of cupric sulphate containing 12 '47 grammes of the crystallised salt per litre, the end of the reaction being indicated by the brown colour produced when a drop of the liquid taken out with a glass rod is added to a drop of potassium ferrocyanide solution on a porcelain plate. 1 c.c. of the above cupric sulphate solution corresponds to '0076 gramme of carbon disulphide. The foregoing process is convenient and fairly accurate. If conducted on 300 c.c. of the sample, sufficient of the purified benzol is obtained to allow of a very perfect CARBON BISULPHIDE IN BENZOLS. 493 Holland and Phillips (Jour. Soc. Cliem. Ind., Hi. 295) "have described a process of determining carbon disulphide in com- mercial benzols which is based on the reaction :-CS 2 -j-4NH 3 = NH 4 CNS + (NH 4 ) 2 S. The manipulation is carried out in the following manner : A piece of combustion-tube about 1 3 inches in length is sealed at one end and drawn out into a funnel at the other. An accurately measured volume of 2 c.c. of the sample of benzol is introduced, followed by 5 c.c. of ferric chloride solution (containing 24 per cent, of .FeCl 3 ) and 10 c.c. of strong ammonia. The tube is carefully sealed, well shaken, wrapped in a cloth, and heated in boiling water for about an hour. It is then cooled, opened, and the contents evaporated just to dryness in a flask. To the residue 20 c.c. of fuming nitric acid should be suddenly added, and the solution boiled nearly to dryness. A repetition of the treatment with nitric acid will be necessary if any sulphur remain unoxidised. Hydrochloric acid and water are next added, and the solution filtered. The filtrate is precipitated by barium chloride, when the weight of barium sulphate multiplied by 0'326 gives the carbon disulphide in the quantity of benzol taken. 1 It is probable that other sulphur-compounds (e.g., thiophene) are partially esti- mated as carbon disulphide by this process. The change in density which results from the elimination of the carbon disulphide from a benzol is very noticeable. Thus, in the case of a sample which would be conveniently classified as a " light 90 per cent. " there will be an entire removal of the previous alliaceous odour; a diminution of density from "885 to '882 or *880, according to the amount of carbon disulphide which has been removed ; and a disappearance of the abnormally large proportion of liquid distilling below 85 C., the reduction in this respect being from 30 per cent, or more down to 12 per cent. The proportion of carbon disulphide eliminated by treatment with alcoholic potash has been proved by B. Nickels to be indicated fractional distillation ; but in such cases the potassium xanthate should be dried by pressure between blotting paper, weighed, and an aliquot part of the dry substance dissolved in alcohol and titrated with copper solution. 1 The test-analyses made by this process were very fairly satisfactory. The authors of the method found the following proportions of carbon disulphide (c.c. per 100 c.c.) in commercial benzols, &c. : CS 2 per cent, by volume. 90 per cent, benzols from Lancashire tar, . . 1'62; 1 '97; 1'93 50 per cent, benzols, 1'16; 0'82; 0'89 Toluols, 016; 0'17 Specially purified benzols, 0'19; 0'20 " Pure benzols " from retail shops, . . . 072; 0*55; 0'68 Crude naphthas. 0'14; 0'21 494 SPECIFIC GRAVITY OF BENZOLS. with a considerable approach to accuracy by the reduction in the density of the sample, thus : 1 per cent, by volume of carbon disulphide raises the density by '0033 2 -0065 3 ,, ,, -0093 Till comparatively recently, the assay of benzols for carbon di- sulphide was usually neglected, but of late there has been some demand for products containing only a limited amount of this impurity. The specific gravity of benzols and naphthas is often a valuable indication of their character, but is apt to be fallacious, especially in the case of 90 per cent, benzols (see page 489). If carbon disulphide be previously eliminated in the manner already described, a determination of the specific gravity affords a much more reliable indication. The specific gravity of benzol is not readily determined by the bottle, owing to its high coefficient of expansion. An easy and fairly satisfactory plan is to employ a delicate hydrometer, 1 care being taken to bring the liquid exactly to the standard temperature of 15 '5 C. (=60 F.), but the most accurate results are obtained by the use of the Westphal-balance (page 13), which is specially suitable for such determinations. As the hydrocarbons of the benzene series decrease in density with each increase in the number of carbon-atoms and rise in the boiling point, low volatility of a benzol corresponds with a low density, though such samples are technically called " heavy benzols." Instead of determining the light hydrocarbons, it is sometimes of interest to ascertain the proportion of true benzene and its homo- logues by converting them into nitro-compounds. 2 To effect this, J. von Hohenhausen {Jour. Soc. Chem. Ind., iii. 7 4) proceeds in the following manner: A mixture is made of 150 grammes of nitric acid of 1'40 specific gravity with 200 grammes of sulphuric acid of 1'845 specific gravity. When quite cold, this is gradually added through a tapped funnel to 100 grammes of the sample of 1 A set of three instruments specially adapted for benzol-testing, but very useful for other purposes, is made by L. Casella, of Holborn Bars, at a very moderate price. They are adapted for reading from the bottom of the meniscus of the liquid. 2 In connection with this method, it must be borne in mind that it is not proved that all the hydrocarbons in benzols capable of nitrofication form nitro-compounds which can be converted into colouring matters. Too little is known of the nature of the light hydrocarbons of commercial benzols to allow of any certain prediction as to their behaviour. Nitrothiophene is known to be present in the purest commercial nitrobenzols, and a test for its presence has been pointed out by Meyer and Stadeler (see page 479). NITROFICATION OF BENZOLS. 495 benzol contained in a 500 c.c. flask. The liquids are well mixed by agitating the flask between each addition, and cooled if they become warm. When the whole of the acid has been added and the con- tents of the flask have become cold, the nitrobenzene is separated from the acid, washed several times by agitation with a dilute solution of caustic soda, and subsequently with water, the latter allowed to separate completely, and the nitrobenzol produced weighed. A good quality of benzene should not get hot imme- diately a small portion of the acid is added to it. 100 parts by weight of an English 90 per cent, benzol of fair average quality yield not less than 150 parts of well-washed nitrobenzene, while some Scotch benzenes do not give more than 135 parts. The nitrobenzol produced should be further examined by fractionally distilling it, when the last 2 per cent, in the retort should remain liquid after cooling. If 100 c.c. of the nitrobenzol be distilled (see page 496), and the first 30 c.c. of distillate be treated with 70 c.c. of concentrated sulphuric acid, the nitrobenzene and its homologues will dissolve in the acid, while all the non-nitrofied hydrocarbons will separate. This layer should be again treated with the mixture of sulphuric and nitric acids, when the presence of previously unchanged benzene will be indicated by a rise of temperature. The acid is tapped off, the residual hydrocarbons again treated with strong sulphuric acid, and their volume observed. FRACTIONAL DISTILLATION OF BENZOLS AND NAPHTHAS. A fractional distillation in some specified manner is a method of very general application for the commercial assay of benzols and allied products, and, if carefully conducted, and the results inter- preted in connection with the specific gravity and chemical tests, the process affords very satisfactory indications. These indications, however, are of a purely arbitrary character, and, unless the pre- scribed conditions of manipulation be rigidly adhered to, great dis- crepancies result. Thus, the barometric pressure, the rapidity of the distillation, the size and shape of the retort, the position of the thermometer-bulb, and even its shape and length, are all more or less important factors in the result obtained. On this account it is usual in contract-notes to specify minutely the mode in which the test is to be made, and the slightest departure from the prescribed directions may invalidate the contract. Ordinary Retort Test. The following "mode of test" is taken verbatim from a form of contract-note largely employed in com- mercial benzol transactions : "A quantity of 100 cubic centimetres to be distilled in a glass retort of a capacity of 200 cubic centi- metres ; bulb of thermometer to be placed ^ of an inch from bottom of retort; distillation to be made over a naked flame, 496 FRACTIONAL DISTILLATION OF BENZOLS. and at such a speed that the distillate shall not pass over in a stream, but as quickly as it can drop in separate particles. Any deficiency in quantity arising from evaporation or other natural causes during the operation to be added to the product at each point, and proper allowance to be made (if necessary) for the observed reading of the barometer." In older forms of contract- note it was usual to prescribe the distillation of 2000 fluid grains or 4 fluid ounces in a retort of 8 fluid ounces capacity, and no allowance was made for barometric variations. The proportion by volume of the sample which passes over below and at a given temperature is called the "strength" of the sample at that temperature. For crude naphtha it is usually sufficient to note the volume distilling below 120 C. ( = 248 F.); in the examination of once-run naphtha, an observation of the volume distilling below 160 C. is also made; in the case of 90 per cent, benzols the volumes distilled are noted at 84 or 85 C., and again at 100 C.; whilst with 50 and 30 per cent, benzols the temperatures noted are 100 and 120 C. The very great majority of parcels of benzol and naphtha sold in this country are bought, or are supposed to be bought, on the above test ; and contrary to the statements which have sometimes been published, 1 the results obtained by different operators under- standing the test agree exceedingly closely, the variations rarely exceeding 1 or 1J per cent. The following is the best mode of conducting the ordinary retort- test so as to ensure results which are constant, and which can be trusted to be as accurate as the process will admit of. The instruc- tions given apply to the assay of a 90 per cent, benzol. The temperature to be observed must, of course, be modified accord- ing to the contract-note, or to the nature of the product under treatment : 100 c.c. of the benzol to be tested is measured in an accurately graduated cylinder, and poured thence into a tubulated retort, of such a size as to be capable of retaining 200 c.c. or 8 fluid ounces, when placed in the ordinary position for distillation. 2 A delicate thermo- meter is fitted in the tubulure of the retort by a cork, so that it may be vertical and the lower end of the bulb be |- inch distance from the bottom of the retort. 3 The neck of the retort is then inserted into 1 See the correspondence in the Chemical News, vol. xliii. pp. 46, 69, 93, 115, 128, 164, and 185. 2 The retort should be previously rinsed with some of the sample to be tested, or a little may be distilled in it, and the residue carefully drained out. 3 The thermometer used for benzol-testing should be 14 inches long ; the bulb sufficiently small to ensure its remaining well immersed in the boiling liquid ; FRACTIONAL DISTILLATION OF BENZOLS. 497 the inner tube of a Liebig's condenser, and pushed down as far as it will go. The condenser should be from 15 to 18 inches in length, and well supplied with cold water. The neck of the retort should not project too far into the condenser ; if necessary it should be cut short. No cork or other connection is necessary between the retort-neck and condenser-tube. Before use, the tube of the condenser should be rinsed with a little of the sample, and allowed to drain, or some of the benzol may be sprayed through it. The graduated cylinder employed for measuring out the sample is next placed under the further end of the condenser-tube in such a manner as to catch all the distillate, while allowing it to drop freely. The retort is then heated by the naked flame of a bunsen burner. 1 The flame should be small, about the size and shape of a filbert, and when the distillation of the benzol commences must be so regulated that the condensed liquid shall fall rapidly in dis- tinct drops, not in a trickle or a continuous stream. When the distillation commences the flame is regulated, if neces- sary, and the rise of the thermometer carefully watched. The moment it registers a temperature of 85 C. 2 the flame is extin- guished. Four or five minutes are allowed for the liquid in the condenser to drain into the measuring cylinder, and then the volume of the distillate is carefully read off and recorded. The lamp is then relighted and the distillation continued till the thermometer rises to 100 C., 2 when the gas is turned off as before, the first marking or division at 70 C., which point should be well out of the tubulure of the retort ; and the graduation should be continued up to 130 C., with divisions at each 4 or (better) of a degree Centigrade. It is a curious but undeniable fact that thermometers, otherwise similar, bitt differing some 6 inches in the height of the 100 C. mark, give distinctly different percentages in benzol-testing. Instruments guaranteed to -^ degree, and constructed in the manner above detailed, are obtainable of L. Casella, 147 Holborn Bars, E.G. 1 The bunsen should be furnished with an air-regulator working automati- cally with each movement of the tap, and should be surrounded with a cylinder to exclude currents of air. The lamp should be placed in a deep tin basin containing sand or sawdust, in order to absorb the benzol in the event of the retort cracking. 2 It is found in practice that, if the light be turned out exactly when the thermometer registers the required temperature, the mercury subsequently rises to an extent varying from to fully 1 degree. With a little experience of a thermometer the range of this "after-rise" will become known, and in subsequent operations the lamp should be turned out when the mercury is as much below the critical temperature as it is expected afterwards to rise about it. Thus if the after-rise of a thermometer has been found to be 1 C., the gas should be turned out when the instrument registers 84 '5 instead of 85, as it wilj subsequently rise to 85*5, and hence 85 '0 may be considered to be the mean reading. VOL. II. 2 I 498 DISTILLATION OF BENZOLS. and the volume of the distillate read off, after allowing time for drainage. The residual liquid in the retort is allowed to cool, and is then poured, to the last drop, into the measuring cylinder. A deficiency from the 100 c.c. originally taken will generally be observed. This is the loss arising "from evaporation or other natural causes," referred to in the contract-note (page 495). The difference between the collective volume after distillation and that of the original sample is to be added to the measure of the distillate collected at each temperature, and the corrected volumes reported as the "strength" of the benzol examined. 1 In benzol-testing it is very desirable to observe the barometric pressure before making an experiment, and to modify the manipu- lation accordingly. A difference of 1 inch in the height of the barometer makes a difference of about 1 C. in the boiling point of a benzol. Hence if the barometer register 29'5 inches instead of 30 inches, the gas should be extinguished so that the thermometer may show a mean temperature of 99'5 instead of 100. The foregoing method of testing benzols is admittedly crude and unscientific, but its indications are well understood (see page 489); and, till within the last few years, it sufficed for the technical examinations required. Now, however, that a demand has arisen for practically pure benzene, toluene, and xylene, the value of the crude products depends on their content of these hydrocarbons, and hence there is a tendency to replace the test by others giving absolute analytical results. Modified Retort Test. A preferable plan to observing the volume of distillate obtained at one or two temperatures only is to note the height of the thermometer at every 5 or 10 c.c. of liquid which passes over. The simultaneous presence of variable and unknown proportions of carbon disulphide and light hydrocarbons in benzol often com- pletely masks the results of the fractional distillation, and hence B. Nickels strongly recommends that the fractionation should be conducted on a portion of the sample from which the carbon di- sulphide has been previously removed by treatment with alcoholic potash in the manner described on page 491. The proportion of carbon disulphide present can be estimated by the xanthate formed, 1 Thus, if by distilling 100 c.c. of a benzol there was obtained 20 c.c. at 85 and 90 c.c. at 100, and the total liquid mixed after distillation measured 99 c.c., the difference between that and 100 c.c., i.e., 1 c.c., must be added to the yields at 85 and 100 respectively, making the corrected figures 21 per cent, at 85 and 91 at 100 C. As a matter of fact the loss of volume by distillation is due far more to expulsion of acetylene and other gases than, to actual loss of benzol. BEHAVIOUE OF BENZOLS WHEN DISTILLED. 499 or may be deduced from the alteration in the density of the sample. Nickels has published (Chem. News, lii. 170) the following results obtained by the distillation in a simple retort in the usual way of synthetically-prepared samples representative of commercial 90 per cent, benzols. Column A. shows the behaviour on distillation of a sample prepared by mixing, Pure benzene, sp. gr. '885, Pure toluene, sp. gr. '871, Light hydrocarbons, sp. gr. 760, Carbon disulphide, sp. gr. 1 "27, 63 per cent, by measure. 27 100 Column B. shows the behaviour of this mixture on distillation, after treating it with alcoholic potash for the removal of carbon disul- phide ; and column C. the behaviour of a mixture of 70 measures of pure benzene with 30 of pure toluene, or, in other words, the mixture without either carbon disulphide or light hydrocarbons : A. B. C. Original Mixture. With CS 2 removed. Benzene and Toluene. Specific gravity, 879 871 8805 1st drop collected at 79-0 82-5 85-4 5 per cent. 84-0 86-2 10 85-0 86-6 20 8*4-0 86-2 87'2 30 85-5 87-2 87'8 40 87-2 88-2 88-8 50 88-5 89-6 89-8 60 90-4 91-2 91-4 70 92-6 93-3 93-2 80 95-6 967 96-2 88 100-0 90 160-0 ... 102-0 These results are very instructive when compared with the figures on the following page obtained by B. Nickels from the fractionation of representative commercial samples of different classes of benzols and naphthas. It is interesting to observe the characters of the Scotch 90 per cent, benzol, which exhibits an abnormally low density owing to the presence of a notable proportion of light hydrocarbons. From the results yielded by the distillation of the synthetical sample after removal of carbon disulphide (B.) there is no indication of the presence of 8 per cent, of light hydrocarbons, though the 500 BEHAVIOUR OF BENZOLS OX DISTILLATION. Good 90 per cent. Benzol. Good 90 per cent. Benzol. Scotch 90 per cent. Benzol. 50 per cent. Benzol. 30 per cent. Benzol. Solvent Naphtha. Very good Once- run Naphtha. Specific gravity, . 8855 882 873 880 875 877 1st drop collected at 824 82 10 per cent. 84 844 94 97 1284 96 20 84* 844 85 95 98 130 994 30 85 85f 964 994 1324 102 40 ggl 85| 86i 98 101 135 107 50 87i 86| 100 104 137 111 60 88i 88 89 1024 106 140 119 70 90^ 89f 91i 106 1094 ]43i 128 80 93 924 94| 1104 1134 1484 145 90 120 120 156 170 92 100 100 100 low density of the sample would point to their presence. This character is disguised in the ungurified sample (A.) by the presence of the carbon disulphide. As stated on page 489, a good 90 per cent, benzol should not begin to distil below 80, and should not yield more than 20 to 30 per cent, of distillate below 85. The distilling point is now seldom below 82, and many 90 per cent, benzols are now rectified so as to give the first drop over at 83 to 84, and the disposition is to go still further, i.e., to 85. This has not been done voluntarily by the manufacturer, but to meet the demands of continental buyers. J. von Hohenhausen gives the following data as typical of the behaviour of good average commercial benzols on distillation in an 8-oz. retort : 90 per cent. Benzol. 50 per cent. Benzol. 30 per cent. Benzol. Specific gravity, . 882 878 875 Distillate at 85 C. 22 per cent. 90 74 , ... ... 95 87 , 18 per cent. 98 40 21 per cent. 100 90 ' ', 50 30 105 94 68 55 110 98 79 73 115 ... 85 84 120 ... 90 90 G. Lunge (Treatise on Coal Tar, #c.,page 290) gives the follow- FRACTIONATION BY THE BULB-TUBE. 501 ing figures as his own experience of the behaviour of commercial benzols and coal-tar naphthas when distilled from a fractionating flask with side-tube, the thermometer-bulb being just immersed in the liquid at the commencement of the distillation i 1 Temperature ; C. 90 per cent. Benzol. 50 per cent. Benzol. Toluol. Carburetting Naphtha. Solvent Naphtha. Burning Naphtha. Boiling point 82 88 100 108 110 138 88 30 . . . ... 93 65 13 ... 100 90 54 ... ... ... 110 74 56 1 120 90 90 35 17 130 ... 71 57 138 84 71 149 _ 97 90 30 160 M ... ni 171 ... ... ... 85 Bulb-Tube Test. When there is "no contract-note to describe the mode of conducting the distillation, it is very much better to substi- tute for the simple retort a flask fitted with some form of dephlegmator. A very useful arrangement of this kind is that of L e Bel and Henninger (fig. 15), which consists of a number of bulbs, varying from two to six, blown upon a tube, which is fitted by means of a cork to an 8-oz. flask containing the liquid to be distilled. The upper end of the tube is furnished with a tubulure, which can be fitted by a cork to a Liebig's con- denser, and with an orifice into which a thermo- meter can be fitted so as to observe the tempera- ture of the vapour which passes over. Each of the bulbs is connected with the one below by a small side-tube. In the constriction of each bulb is placed a little cup of platinum- or copper-gauze, of the size and shape of a small thimble. These cups are made by folding the gauze over the end of a stout glass rod. The ascending vapour condenses in the cups, 1 In the opinion of the writer, in all such distillations it is desirable that the bulb of the thermometer should be wholly immersed in the liquid, and should remain so, if possible, till the close of the operation. When a benzol is distilled the temperature rises very rapidly towards the end of the distillation, and the bulb has not time to take up the heat from the vapour with sufficient rapidity to render the thermometer-indication accurate. The heating of the mercury by direct contact of the thermometer-bulb with the liquid is much more rapid. 502 FR ACTION ATION BY THE BULB-TUBE. and thus serves to wash, the vapour subsequently formed as it bubbles through. When the liquid rises to a certain height in each bulb it runs off by the side-tube, and ultimately finds its way back 'to the distilling flask, the flame under which is so regulated as to keep all the cups full and cause the distillate to fall in separate drops. In an improved form of dephlegmator, devised by Glynsky (fig. 16), the wire-gauze is replaced by hollow balls of glass, introduced into the bulbs during manufacture. 1 He in pel (Jour. Chem. Soc., xlii. 551) substi- tutes for the more complex apparatus of Hennin- ger and Glynsky a long glass tube arranged ver- tically and filled with solid glass beads. This simple arrangement is remarkably efficient. By employing a dephlegmating apparatus, ff\ greatly improved results are obtainable, and a Jj complex liquid may be fractionated at one opera- tion into approximately pure constituents. Hence it is probable that the present empirical method of testing will ultimately be entirely superseded by the more rational process. 2 Almost absolutely pure benzene, toluene, and xylene are now articles Fig. 16. of commerce, being produced on a large scale by a single apparatus based on the principle of the bulbed tube ; and it will be necessary to ascertain the percentage composition of the benzols used in their production. This is approximately possible by operating with the bulb-apparatus, especially if the carbon disulphide be previously removed, but it is wholly beyond the powers of the ordinary retort. 3 1 This apparatus is obtainable from Messrs Townson & Mercer, 89 Bishops- gate Street, E.G. The description of dephlegmators in the text was given in vol. i. (page 14), but it appeared desirable to repeat it in the present section. 2 The use of a dephlegmator in fractionating benzols is universal in German laboratories, tubes having as many as twelve bulbs on the same stem being sometimes employed. 1000 c.c. is the quantity usually employed for this test, and the distillation is conducted in a copper vessel. 3 The annexed figures are communicated by Mr B. Nickels. Column A. represents the temperatures recorded by the thermometer when the original benzol was distilled in an 8-07. retort in the ordinary way ; B. shows the alter- ation produced by removing the carbon disulphide in the manner described on page 491 ; and C. shows the results obtained when the purified benzol was dis- tilled in a three-bulbed apparatus, instead of in a retort. When the original sample A. was fractionated in the three-bulb apparatus at 45 it gave oily drops indicative of carbon disulphide ; and these became FRACTIONATION BY THE BULB-TUBE. 503 If 400 or 500 c.c. of the sample of benzol be carefully purified from carbon disulphide by treatment with alcoholic potash and then fractionated with the aid of a 6 -bulb tube, the light hydro- more abundant at 60. At 70, 5 per cent, had distilled, and the thermometer rose at once to 80. The process being stopped at this point, the contents of the flask were found to have decreased in density from '884 to '882, showing A. B. C. Commercial A., in 8-oz. B., distilled in 90 per cent. retort, after flask with three- Benzol in8-oz. being purified bulb apparatus. retort. from CS 2 . Specific gravity at 15 '5, 884 881 881 First drop distilled at 79-5 C. 83-4 C. 5 per cent, over at ... 84-2 81-25 C. 10 84-3 82-0 20 85-0 82-8 '25 84 : b ... 30 85-0 85 : 8 83-6 40 85-4 86'4 83-5 50 86-4 871 847 60 88-0 88-3 85-3 70 90-0 90-0. 86-5 80 93-0 93-0 89-3 90 100-0 100-0 100-0 95 ... 112-4 111-8 the removal of a substance heavier than benzene. That this was largely carbon disulphide is proved by the figures in column B., the complete removal of the impurity reducing the gravity and raising the boiling point. When the puri- fied sample B. was fractioned by the three-bulb apparatus into 20, 70, and 10 per cent, portions, they showed a density of '883, "885, and '8715 respectively. Had carbon disulphide been present, the first fraction would have been denser instead of lighter than benzene (sp. gr. '885). Hence the first portion of the distillate must have contained light hydrocarbons (" petroleum "). By operat- ing originally on 300 c.c. of the same sample, removing the carbon disulphide by alcoholic potash, and several times repeating the process of fractioning with the three-bulb apparatus, Nickels obtained the following results as in- dicative of the proximate analysis of the benzol tested : Carbon disulphide, removed by alcoholic potash, . Light hydrocarbons, sp.gr. '860 (more or less non- nitrofiable ; probably chiefly amylene and acetonitril), Benzene, specific gravity '885, and distilling wholly ) within a range of 2 degrees, .....) Toluene, specific gravity '8715, and distilling within) 2 degrees, f 1 '5 per cent. 3-5 100-0 504 ASSAY OF CRUDE NAPHTHA. carbons can be concentrated in a comparatively small volume dis- tilling between 60 and 79 C. The lightest of these impurities has a density of *760, and such a product is readily obtainable by again fractionating that first obtained (see footnote, page 488). 1 The assay of crude naphtha by distillation is not unfrequenfcly limited to a determination of the volume-percentage obtained at a temperature not exceeding 120 C., the operation being conducted in an ordinary retort (page 496). The proportion of distillate usually ranges from 15 to 35 per cent., according to the quality of the naphtha under examination. J. vonHohenhauseii (Jour. Soc. Chem. Ind., iii. 73) gives the following data as representing the distilling points of certain typical crude coal-tar naphthas : Percentage of Distillate. Temperature ; C. Wigan. Yorkshire. Scotland. 105 4 110 4 16 17 120 19 34 38 130 33 47 49 140 45 58 150 55 69 Once-run naphtha may be similarly assayed. It usually yields from 40 to 60 per cent, of distillate below 120 when examined by the retort-method, 2 and an additional 32 to 36 per cent, be- 1 B. Nickels has pointed out that if 760 be taken as the density of the light hydrocarbons the proportion of these present in commercial 90 per cent, benzol may be deduced with a considerable approach to accuracy from the den- sity of the sample previously purified from carbon disulphide. Thus a mixture of 70 measures of pure benzene with 30 of pure toluene (which is the proportion in which they usually exist in 90 per cent, benzol) has a density of '8805, which would therefore be that of the sample purified from carbon disulphide if no light hydrocarbons were present. But each 1 per cent, of impurity of 760 sp. gr. reduces the density of the mixture by about "0012. Thus the syntheti- cal sample described on page 499, containing 8 per cent, of light hydrocarbons, had, after removal of the carbon disulphide, a density of '8710. (0'0012 x 8 = 0-0096; and '8805- '0096= '8709 ; or '8710 nearly.) Thiophene is not com- monly present in benzol in sufficient proportion to affect the figures obtained as above ; but if existing in quantity, as in some carbonisation benzols, it can be separated by agitating the purified sample with one-tenth of its measure of strong sulphuric acid before proceeding to fractionate. 2 A sample of genuine once-run naphtha yielding 50 per cent, over at 12o 3 when distilled in a retort at a rate of 120 drops per minute, should also yield DISTILLATION OF ONCE-RUN NAPHTHA. 505 tween 120 and 160. These products, when mixed and redistilled, should yield from 19 to 26 per cent, over at 100 C. For technical purposes the results thus obtained are often sufficient, and their inter- pretation is well understood. London makes generally give a good yield of 90 per cent, benzol, while Midland products are preferable for 50/90 benzols. The results obtained by fractionally distilling a sample of very good once-run naphtha are given on page 500. The following figures, communicated by B. Nickels, show the comparative behaviour of typical samples of crude and once-run naphthas when distilled in an ordinary retort and in a flask fur- nished with a bulb-tube. The test may be made on 100 c.c. : By Retort Method. By Bulb-Tube Method. Character of Naphtha. Below From 100 Froml i Below From 100 From 120 100 C. to 120. to 170 100 C. to 120. to 160. CRUDE London, ... 12 ! 28 . London, 36 ... i 41 London, ... 8 20 , Plymouth, 46 45 Lancashire, . ... 20 ... 25 Cleckheaton, . 3 44 30 23 24 Derbyshire, . 4 43 35 36 20 26 Scotch, . ... 28 32 17 37 ONCE-RUN London, 45 ... 1 43 London, ... 66 ... 52 Country, 60 ... 45 . . Country, 59 ... 41 Country, 58 ... 42 . . Country, 64 ... 46 A careful inspection of these results shows that crude London naphthas give a low yield by the retort method at 120, as com- pared with the yield by the bulb-tube at 100; while country naphthas give a yield at 120, by the retort, not much less than, and often considerably exceeding, the yield by the bulb-tube at 100. Crude naphthas of London make (e.g., giving by retort method 17 per cent, at 100 and 35 at 120) generally give a good yield of 90 per cent, benzol ; on the other hand, Midland makes (e.g., giving by retort 10 per cent, at 100 and 48 at 120) are better for 50/90 benzols. 50 per cent, over below 100 when distilled with a bulb-tube at a rate of 100 drops per minute. 506 ASSAY OF CRUDE NAPHTHA. A more accurate knowledge of the composition of crude naphtha may be obtained by distilling 500 c.c. in a retort and collecting the distillate in two portions. The fraction passing over below 160 represents the yield of once-run naphtha, and that distilling between 160 and 180 C. the yield of medium naphtha. These distillates may then be further fractionated by means of a bulb- tube. The fraction of once-run naphtha which on redistillation with a bulb-tube passes over below 100 represents 90 per cent, benzol; from 100 to 120, toluol, commencing to distil at 108 to 110 and giving 88 to 90 per cent, over at 120; and from 120 to 160, solvent naphtha. The use of the bulb-tube for fractionating naphthas has now become very general. The indications obtained when once-run naphthas are assayed in the laboratory by this method agree fairly well with the actual yields given on a practical scale, at any rate for 90 per cent, benzol and toluol, the determina- tion of solvent naphtha being but rough. The following are results actually obtained : Laboratory. Distillate below 100 C. = 30 per cent. ,, between 100 and 120 =15 120 and 160 = 20 Works. 90 per cent, benzol =31 to 32 per cent. ,, toluol =14 to 16 ,, Solvent naphtha =12 to 15 ,, The foregoing test may be satisfactorily made on 100 c.c. of the once-run naphtha, but it is preferable to operate on such a quantity as will yield at least 100 c.c. of distillate below 100, so that this fraction can be proved by a subsequent test to have the actual characters of a 90 per cent, benzol. 1 If a fractionating bulb- tube be not at hand, an assay of crude naphtha for the yield of 90 per cent, benzol can still be made tolerably satisfactorily by the following process : Distil 500 c.c. of the sample in a glass retort, and collect separately the portion passing over below 180 C. This fraction, representing once-run naphtha, is then redistilled up to 120, and the distillate again distilled up to 105 C., when the fraction which passes over below this temperature should have the characters of "90 per cent. benzol." 1 This, however, should be proved to be the case, when the measure obtained indicates the yield from 500 c.c. of the crude naphtha. If once-run naphtha is to be examined the first distilla- tion up to 180 C. should be omitted. 1 A rule is given on page 490 by which the proportion of 90 per cent, benzol in a higher boiling product can be deduced. NAPHTHALENE. 507 NAPHTHALENE AND ITS DERIVATIVES. Among the products of the dry distillation of organic substances certain closely-associated bodies occur, of which naphthalene itself is the best known and most characteristic, but homologues and hydrogen-additive compounds of naphthalene are also present. Naphthalene. Naphthalin. C 10 H 8 = CjoH^H. 1 Naphthalene is produced largely when the vapours of various organic substances are passed through a red-hot tube, and is present most abundantly in products resulting from the employment of an excessive temperature. Thus naphthalene occurs largely in the tar produced in the distillation of coal for the manufacture of illumin- ating gas, the usual proportion being 5 to 10 per cent. It is said to be wholly absent from the products of the distillation of bitu- minous shale when conducted in the ordinary manner, being in this product replaced by paraffin. 2 Naphthalene is obtained by sublimation, or by the cooling of its boiling saturated solutions, in large white crystalline rhombic plates of silvery lustre. It possesses a characteristic odour, 3 which may be covered, when desired, by the addition of a small proportion of oil of bergamot. Its taste is biting and somewhat aromatic. Naphthalene melts at 79 C. to a liquid as clear as water, and on cooling forms a brilliant white radiated mass, often filled with cavities. Naphthalene boils at 216 to 218 C., but evaporates copiously with the vapour of boiling water, and volatilises very 1 Naphthalene appears to have the constitution of two conjoined benzene nuclei, thus The derivatives of naphthalene belong to the a- or ^-series according to the position of the radicals replacing the hydrogen-atoms of the molecule. 2 Berthelot has shown that naphthalene is a constant product of the mutual reaction of benzene, ethylene, and acetylene at a high temperature, the two first reacting to form styrolene, and this product with another molecule of ethylene to generate naphthalene: C 6 H 6 + C 2 H 4 =C 8 H 8 + H 2 ; and C 8 H 8 + C 2 H 4 = C 10 H 8 + 2H 2 . Again, naphthalene is produced by the reaction of benzene and acetylene, C f) H 6 + 2C 2 H 2 = C 10 H 8 + H 2 ; or of styrolene and acetylene, C 8 H 8 + C 2 H 2 = C 10 H 8 + H 2 . As benzene and its homologues are wholly absent from shale products, the simultaneous absence of naphthalene becomes intelligible. 3 It is said that absolutely pure naphthalene is free from smell, but this statement requires confirmation. 508 CHARACTERS OF NAPHTHALENE. sensibly even at ordinary temperatures. When inflamed, it burns with a luminous and very smoky flame. Naphthalene has a density of 1*158 in a solid state. In a molten state, at 79'2 C., its density is 0'978. Melted naphthal- ene dissolves sulphur, phosphorus, iodine, indigo, &c. Naphthalene is insoluble in cold, and but faintly soluble in hot water, and is insoluble in alkaline or dilute acid liquids. It dis- solves readily in alcohol, wood spirit, ether, chloroform, carbon disulphide, benzene, petroleum spirit, and fixed and volatile oils. It is also slightly soluble in concentrated acetic acid, and readily in carbolic and cresylic acids. Nitric acid converts naphthalene into nitro-naphthalene, C 10 H 7 (N0 2 ), or dinitro -naphthalene, C 10 H 6 (N0 2 ) 2 , accord- ing to the strength of the acid employed. Chromic acid and certain other oxidising agents convert naphthal- ene into naphthal-quinone, C 10 H 8 2 , which by further treatment is converted into phthalic acid, C 8 H 6 4 . Concentrated sulphuric acid converts naphthalene into isomeric naphthalene-sulphonic acids, the exact natures of which vary the temperature and proportions of materials employed. They serve for the preparation of the corresponding naphthols, C 10 H r .OH (page 510). Chlorine and bromine act on naphthalene with formation of various c h 1 o r o- and bromo-substitutio n-p r o d u c t s. For the detection of naphthalene, the substance should be dis- tilled, and the fraction passing over between 210 and 225 treated with fuming nitric acid, the product poured into water, and the precipitate washed and heated with a boiling solution of equal parts of caustic potash and potassium rnonosulphide, when a purple coloration will be produced if naphthalene were present. COMMERCIAL NAPHTHALENE. Naphthalene is contained largely in the less volatile portions of coal-tar naphtha, in the crude carbolic acid and "creosote oils" which subsequently distil, and in the semi-fluid " anthracene oils " obtained at a still higher temperature. It is said to be wholly absent from the products of the distillation of bituminous shale. By cooling the portion of the coal-tar distillate which passes over about 200 C., naphthalene is frequently deposited in such quan- tities as to render the product semi-solid. It may be separated by pressure from the liquid oils, and purified by heating strongly with 5 to 1 per cent, of concentrated sulphuric acid, washing thoroughly with water, and subliming the product. 1 1 It is better to press the naphthalene to be purified, and to precede the treatment with sulphuric acid by a washing with caustic soda solution to COMMEECIAL NAPHTHALENE. 509 Naphthalene is now prepared commercially in beautiful colourless crystals which wholly distil within a very few degrees of the boiling point of pure naphthalene. Besides this nearly pure product, which, when remelted and cast into moulds, is employed largely in " albo- carbon" lamps, naphthalene occurs in commerce as an impure coarsely crystalline substance of peculiarly rank odour, technically known as crude naphthalene or " naphthalene salts." The methods of testing naphthalene " salts " are of a very simple character, the following being those most commonly employed : 25 grammes weight of the sample is wrapped up in several layers of coarse filter-paper, so as to form a flat thin cake. This is placed between two iron plates and strongly pressed in a vice, as long as any oil is expressed. The usual proportion of oil eliminated varies from 6 to 16 and occasionally 20 per cent, of the sample; but 13 per cent, is the maximum proportion which should be present. The "salts" freed from oil in the above-described manner may then be further examined by distilling 10 grammes in a small retort as described on page 496. A good sample of pressed salts should give nothing over below 210, and should yield 90 per cent, of distillate before the temperature of the contents of the retort rises above 225 C. The sublimed naphthalene of commerce contains from 70 to 99 per cent, of the pure substance. The finer qualities form colourless crystals, but the inferior grades have a fawn or brown colour. A useful and reliable test for the purity of sublimed naphthalene consists in warming the substance in a test-tube with a little pure concentrated sulphuric acid. With pure naphthalene the solution remains colourless, but a decided pinkish tint is observed if the sample contains 1 per cent, of impurity, and the coloration becomes deeper pink, or even brown, the greater the proportion of foreign matters in the naphthalene. Naphthalene Oils. This name, as also that of " creosote oil," is applied to the frac- tion of coal tar distilling between 200 and 280 or 300 C. Its com- position is very imperfectly understood, but besides phenols and phenoloid bodies, and a variety of b a s e s, it is apparently remove phenoloi'd bodies. G-. Lunge recommends the addition of native manganese dioxide, or dried weldon mud, after the acid has been thoroughly mixed with the naphthalene, the mixture being heated to 100 C. for a short time. The naphthalene is allowed to cool, washed successively with pure water, weak alkali, and pure water, and is then distilled. Prepared in this manner, the product remains perfectly white for eight or nine months (Chern.* News, xliv. 65). 510 NAPHTHALENE OILS. largely composed of naphthalene and certain hydrides and homologues of that body, the following of which have been described as being present. NAPHTHALENE DIHYDRIDE, C 10 H 8 .H 2 , is a viscid liquid of strong disagreeable smell, boiling at 200 to 210 C. It is powerfully acted on by bromine, and is soluble in cold fuming nitric acid. NAPHTHALENE TETEAHYDRIDE, C 10 H 8 .H 4 , resembles the dihydride, but boils at 190 C. a- AND (3- METHYL-NAPHTHALENE, C 10 H 7 .CH 3 , occur in the frac- tion of coal tar distilling between 220 and 270. At the ordinary temperature, the a-variety forms a colourless liquid having a blue fluorescence and pleasant aromatic smell. It has a density of 1*0042 at 22 C., distils in a current of open steam, and crystal- lises at 18 to a hard mass, a-methyl-naphthalene is miscible in all proportions with alcohol, ether, glacial acetic acid, carbon disul- phide, and benzene. It is readily attacked by oxidising agents. /3-rnethyl-naphthalene crystallises like naphthalene in large white plates, melts at 32'5, and boils at 141-142 C. DIMETHYL-NAPHTHALENE, C 10 H 6 :(CH 3 ) 2 . According to E m m e r t and Eeingruber (Annalen, ccxi. 365), the fraction of coal tar boiling between 252 and 270, after removing all basic, oxy- genated, and crystallisable bodies, apparently consists of a mixture of several isomeric dimethyl-naphthalenes, the separation of which has hitherto proved unmanageable. These bodies are said to con- stitute the major portion of coal-tar creosote oils. The assay of naphthalene oils is fully described in the section on " Creosote Oils." Naph.th.olS. Naphthyl Alcohols. Hydroxy naphthalenes. C 10 H 7 .OH. By the action of concentrated sulphuric acid, naphthalene yields two isomeric sulphonic acids of the formula C 10 H 7 .S0 3 H. At moderate temperatures (e.g., 80 to 100 C.) the a-modification is the chief product, but at 160-170 C. /8-naphthalene-monosulphonic acid predominates. On diluting the solution with water, saturating it with lead carbonate, and filtering from the insoluble lead sulphate and excess of lead carbonate, the lead salts of the two sulphonic acids are obtained in solution. They may be separated by concen- tration and crystallisation, lead a-naphthalene-sulphonate forming shining laminae soluble in 27 parts of cold water or 11 of alcohol, while the /3-compound crystallises in scales or crusts which require 115 parts of cold water or 305 of alcohol for solution. When these lead salts are respectively fused with excess of caustic potash, a substitution of OH for S0 3 H occurs, with formation of the variety ISOMERIC NAPHTHOLS. 511 of naphthol corresponding to the sulphonate employed. 1 On dissolving the fused mass in water, and treating the filtered solu- tion with hydrochloric acid, the naphthol is precipitated, and may be purified by crystallisation from hot water, followed by sublimation. The isomeric naphthols have been isolated by Schultze from the "green oils" left after the filtration of the anthracene from a high- boiling fraction of coal tar (Her., xviii. 150). The isomeric naphthols bear to naphthalene the same relation that phenol bears to benzene, and they closely resemble phenol in their general chemical properties. Both naphthols are colourless crystalline bodies, melting when heated and distilling unchanged at a higher temperature. They are sparingly soluble in hot and nearly insoluble in cold water. In alcohol, ether, chloroform, and benzene they dissolve readily. They dissolve readily in solutions of caustic alkalies, forming unstable compounds which are decom- posed when the solutions are evaporated. By the action of carbon dioxide on their sodium-derivatives, the sodium salts of hydroxy-acids are formed, in a manner parallel to the production of salicylic acid from phenol. On warming with concentrated sulphuric acid, the naphthols are dis- solved and converted into sulphonic acids, C 10 H 6 (OH).S0 3 H. The following are the most important distinctions between the isomeric naphthols : x-Naphthol. /3-Naphthol. Crystallises in small monoclinic needles. Melts at about 95 2 and boils at 278 to 280 C. Faint odour, resembling phenol. Volatilises readily with vapours of water. Aqueous solution becomes dark violet, changing to reddish-brown on adding solution of bleaching powder. Aqueous solution becomes red, and then violet, on adding ferric chloride. Crystallises in laminae belonging to the rhombic system. Melts at 123 , 2 and boils at 285 to 21)0. Almost odourless. Scarcely volatile with vapour of water. Aqueous solution is coloured pale yellow by solution of bleaching powder. Aqueous solution becomes pale green on adding ferric chloride. 1 On the large scale caustic soda is used, the mixture being heated very gradually till, at a certain temperature, the melt separates into two layers, the upper of which, consisting of crude sodium naphtholate, is decanted, while the lower is a mixture of caustic soda and sodium sulphate (Levinstein, Jour. Soc. Chem. 2nd., iv. 478). 2 A mixture of the two naphthols is said to melt at a lower temperature than either substance alone. 512 DINITRONAPHTHOL. Both, the naphthols yield interesting nitro-derivatives, but they are most conveniently prepared by indirect methods. DiNiTRO-a-NAPHTHOL, C 10 H 5 (N0 2 ) 2 .OH, is obtained by dissolving a-naphthol in concentrated sulphuric acid, diluting the resultant sulphonic acid with water, adding nitric acid, and heating gently, when the dinitro-derivative is deposited in minute yellow needles. The same body is obtainable by other methods, and may be purified by converting it into the ammonium salt, which is recrystallised and decomposed by an acid. Dinitro-a-naphthol resembles picric acid, and forms a series of beautiful and well-crystallised salts. The sodium and calcium salts have been extensively employed under the names of "Manchester yellow," "Martius' yellow," and "naphthalene yellow." 1 They are liable to be adulterated with dextrin and sodium sulphate. They dye silk and wool a brilliant yellow colour, free from the greenish reflection peculiar to fabric dyed with picric acid. The latter dye may be distinguished by boiling wool in the acidified solution, washing it, heating it with ammonio- sulphate of copper, and again washing. When a fibre or fabric dyed with picric acid is thus treated it turns . bluish green, but if naphthalene yellow has been used an olive-green tint results. Either of the dyes may be extracted from a fabric with hot dilute ammonia, which dissolves them with yellow colour. "Waller and Martin (Analyst, ix. 166) have recorded a case in which mustard was found to be coloured with naphthalene yellow, a use for which its marked poisonous characters render it very unfit. ANTHRACENE AND ITS ASSOCIATES. In the distillation of coal tar, the fraction passing over above the temperature of 270 C. is a heavy, greenish or reddish, oily liquid known as anthracene oil, which usually amounts to about one-sixth of the entire distillate. On cooling completely, a granu- lar, crystalline deposit is formed, which consists chiefly of a mix- ture of various solid hydrocarbons, of which anthracene is the most important and characteristic. The deposit is freed as much as possible from the adherent oil by filtration, pressure, or other mechanical means. Formerly it was sold in a pasty state, but the 1 The "Naphthalene yellow, S." of the Badisclie Anilin und Soda FabriJc ' is the potassium salt of dinitronaphtholsulphonic acid, C 10 H 4 (N0 2 ) 2 (S0 3 K)OK. By boiling it with strong hydrochloric acid the free sulphonic acid is obtained in long yellow needles, soluble in water but insoluble in ether. The sodium and ammonium salts are freely soluble, the barium and lead salts sparingly so. Various dinitronaphtholsulphonates, including the free acid, are manufactured by Lev. instein & Co. under the name of "Naphthol-yellow." ANTHRACENE. 513 purification is now carried further. To obtain a superior product, it is desirable to use powerful hydraulic pressure, and to press the crude anthracene, first cold and then hot, by which means a 30 to 40 per cent, cake may be obtained without washing. The anthra- cene may be further purified by treatment, after crushing, with coal- tar naphtha boiling between 120 and 190, which, in some cases, is subsequently washed out by petroleum spirit boiling between 70 and 90 C. 1 Anthracene and the other chief constituents of the product thus obtained are described in the following sections. The assay of the crude anthracene is described on page 528 et seq. (-CH-) Anthracene. C U H 10 =C 8 H 4 V | Vc 6 H 4 ". (CH-) U H 10 = C 6 H 4 "4 | ICHJ Anthracene is formed in a variety of reactions taking place at high temperatures. It is a characteristic constituent of coal tar from the manufacture of illuminating gas, and is also found in the tar produced by condensing the gas from Simon-Carve coke-ovens, and in the tar obtained in the manufacture of gas by exposing petroleum to a high temperature. Anthracene is now manufactured on a large scale from the high-boiling fractions of these tars (see above). It is contained in notable quantity in coal-tar pitch, and hence the distillation of this product has been carried as far as actual coking in order to obtain the greatest possible yield of anthracene, but the product was so impure, and is refined with such difficulty, that the manufacture from this source has been abandoned. When quite pure, anthracene crystallises in colourless rhom- boidal plates or shining scales, which exhibit a fine violet fluores- cence. 2 It melts at 213 C., sublimes at about the same temper- ature in micaceous scales, and distils almost unchanged at about 360 C. 3 It may be distilled nearly unchanged in admixture with caustic potash, and Perkin recommends this as the only method by which crude anthracene can be purified on the large scale. Anthracene is insoluble in water and in dilute acid and alkaline solutions. In cold alcohol chemically pure anthracene dissolves 1 The solvent is recovered by distillation. The residue consists largely of phenanthrene and liquid oils of unknown nature. Hitherto its only application has been for making lamp-black. 2 According to Liebermann, anthracene and all its derivatives which contain the two peculiar atoms of hydrogen intact exhibit fluorescence. If, however, the CH groups be changed for CO, as in anthraquinone, C 6 H 4 : (C0) 2 : C 6 H 4 , the fluorescence is wanting. 3 Nearly pure anthracene may be obtained by melting a partially purified sample in a retort and passing a strong current of air through it, when the anthracene is carried off and deposited in brilliant flakes. VOL. II. 2 K 514 CHARACTERS OF ANTHRACENE. to the extent of 0'6 per cent., while benzene dissolves Q'9 1 and carbon disulphide 1*7 per cent, of anthracene. 2 If picric acid be added to a solution of anthracene in boiling benzene, a picrate of anthracene is formed, having the composition C 14 H 10 , C 6 H 2 (N0 2 ) 3 OH. On cooling, this body separates in ruby-red needles, which melt at 170 C., and are soluble in a small proportion of alcohol with red colour, but on adding more alcohol the compound undergoes decomposition and the liquid is decolorised. The crystals are also decomposed by water. Hot dilute nitric acid converts anthracene into a mixture of anthraquinone with dinitro-anthraquinone, C 14 H 6 (N"0 2 ) 2 2 . The latter body crystallises in microscopic quadratic plates, and, according to Fritzsche, forms compounds with all the solid hydro- carbons associated with anthracene in coal tar. With anthracene itself, Fritzsche's reagent gives shining, rhomboidal, purple plates, which appear blue if the hydrocarbon be not quite pure, and if too impure the reaction fails altogether. On gently heating, concentrated sulphuric acid dissolves anthra- cene with greenish colour, and at a higher temperature forms anthracene-sulphonic acids. Fuming sulphuric acid acts violently on anthracene. By the action of bromine or chlorine, anthracene is converted into various b r o ni o - and chloro-derivatives. On treating dibromanthracene, C 14 H 8 Br 2 , with oxidising agents it is converted into dibromanthraquinone, C 14 H 6 Br 2 2 , and this when heated with caustic potash yields dioxyanthraquinone or alizarin, C 14 H 6 (OH) 2 2 . Similarly, by treatment with chlorine, 1 When a cold saturated solution of anthracene in benzene is exposed to sunlight, an allotropic modification of anthracene crystallises out in micro- scopic plates. Par -anthracene is but very sparingly soluble. It melts at 244 C., and is reconverted into anthracene. It is not attacked by bromine or by concentrated (ordinary) nitric acid, and does not combine with picric acid, but yields anthraquinone by the action of chromic acid or warm fuming nitric acid. 2 These results are by Gessert (Dingl. Polyt. J., cxcvi. 543). Yers- mann (Her., 1879, p. 1978) has published the following data, which unfortunately were not obtained with pure anthracene. The figures represent grammes of the solid contained in 100 c.c. of the solutions at 15 C. Solvent. Anthracene. Solvent. Anthracene. Alcohol, sp. gr. '800 825 830 835 840 850 472 424 408 397 387 360 Ether, Chloroform, Carbon disulphide, Glacial acetic acid, Benzene, . Petroleum spirit, 858 2-587 1-180 472 1-470 291 ANTHEAQUINONE. 515 anthracene is converted into the theoretical weight of d i c h 1 o r- anthracene, C 14 H 8 C1 2 , a lemon-yellow crystalline substance re- sembling picric acid. The reaction forms an important step in the manufacture of artificial alizarin. ANTHRAQUINONE. 1482 Anthraquinone has the constitution of a diphenylene-dike- tone. It is produced by the action of oxidising agents on anthracene. Chromic acid is the best oxidiser for the purpose, as with nitric acid nitro-anthraquinone is apt to be produced. The details of the process are given on page 530. As usually prepared, anthraquinone appears as a felted mass of delicate crystalline needles of a yellowish or pale buff colour, but when purified by sublimation it is obtained in long, delicate, lemon-yellow needles, or golden-yellow prisms. When pure, it melts at 277 C. and boils at a temperature between the points of ebullition of mercury and sulphur. Anthraquinone is neutral in reaction, and insoluble in water and in dilute acid and alkaline liquids. It is sparingly soluble in alcohol and ether; more soluble in hot benzene. It is an exceedingly stable substance, resisting the action of reagents in a remarkable degree. Anthraquinone is not affected by hot hydrochloric acid or by boiling with solution of caustic potash or milk of lime. It dissolves in hot nitric acid of 1'4 specific gravity, and is deposited in crystals on cooling, a more complete separation occurring when the acid is diluted, In concentrated sulphuric acid at 100 C. anthraquinone dis- solves unchanged, and on exposing the solution to a moist atmosphere is gradually redeposited in crystals, or may be obtained in a more finely-divided state by pouring the acid into water. Solution in sulphuric acid is employed for purifying commercial anthraquinone. When strongly heated with concentrated sulphuric acid, or more easily if fuming acid be used, anthraquinone is converted into a mixture of anthraquinone-mono- and anthraquinone-di- sulphonic acid. These bodies are also obtained by the action of sulphuric acid on dichloranthracene, C 14 H 8 C1 2 , and play an important part in the manufacture of artificial alizarin. The proportion of the two sulphonic acids formed depends on that of the sulphuric acid employed. On nearly neutralising the product with caustic soda, sparingly soluble sodium anthraquinone- monosulphonate separates, and may be obtained in brilliant pearly scales by pressure and recrystallisation. Heated with caustic soda and potassium chlorate it yields pure alizarin. When fused with caustic potash, anthraquinone yields p o t a s- 516 ANTIIRAQUINONE. sium benzoate, (C 14 H 8 2 + 2KHO = 2KC 7 H 5 2 ), and, when ignited with or distilled over soda-lime, benzene, C 6 H 6 , is formed. By the action of certain reducing agents, such as sodium amal- gam, or caustic soda solution and zinc-dust, anthraquinone is con- verted into hydro-anthraquinone, C 14 H 10 2 . This reaction has been applied by A. Glaus (JSer., x. 925) as an extremely delicate means of detecting anthraquinone, and hence anthracene. A few particles should be placed in a test-tube with some sodium amalgam, covered with ether free from water and alcohol, and the whole well shaken together. On adding a drop of water a splendid red colour appears, but is destroyed by shaking in contact with air, reappearing on standing. If absolute alcohol be substituted for the ether, the colour produced is dark green, turned to red by a trace of water, and destroyed by shaking with air. The marked characters and great stability of anthraquinone render it the most convenient body into which to convert anthra- cene for the purpose of determining it. The best method of effect ing this is described on page 530. ANTHRACENE DIHYDRIDE, C 14 H 12 = C 14 H 10 ,H 2 , occurs in coal tar. It crystallises in colourless plates resembling naphthalene, fuses at 106, and distils unchanged at 305. It has a peculiar odour, sublimes at the temperature of boiling water, and distils readily with the vapour of water or alcohol. Anthracene dihydride is in- soluble in water, but is readily soluble in alcohol, ether, or benzene, the solutions exhibiting a blue fluorescence, which is not shown by the solid substance. It is said not to yield a compound with picric acid. ANTHRACENE HEXAHYDRIDE, C 14 H 16 = C 14 H 10 ,H 6 , occurs in coal tar with the dihydride, which it closely resembles. It melts at 63 and boils at 290. METHYL-ANTHRACENE, C 15 H 12 = C 14 H 9 (CH 3 ), occurs in small quantities in coal tar, and is produced by the reduction of chryso- phanic acid and other bodies. It resembles anthracene, crystallises from hot alcohol in thin, pale yellow, bright scales, and sublimes in greenish scales. It melts at a temperature variously stated at 200 to 210; is sparingly soluble in alcohol, ether, and glacial acetic acid, but readily in benzene, chloroform, and carbon di- sulphide. It forms a picric acid compound similar to that of anthracene, and is dissolved by concentrated nitric or sulphuric acid, especially if hot. DIMETHYL- ANTHRACENE, C 16 H 14 = C 14 H 8 (CH 3 ) 2 , resembles the last compound, melts at 224 to 225, and is supposed, though not proved, to exist in coal tar. CONSTITUENTS OF CEUDE ANTHEACENE. 517 Constituents of Crude Anthracene. The crude commercial anthracene, obtained from coal tar in the manner described in outline on page 512, is an extremely complex mixture of hydrocarbons and other organic compounds, some of which have been but very imperfectly studied. The following is a list of the better-known hydrocarbons occurring in crude anthracene: Empirical Formula. Name of Hydrocarbon. Dissected Formula Melting Point; Boiling Point ; Clo H 8 Naphthalene, .... ... 79 218 to 220 f Diphenyl, or Phenyl-benzene, . |c 6 H 5 } 70-5 254 C 12 H 10 | Acetnaphthene, " H E I 95 285 C 13 H 10 ^Fluorene, or Diphenylene- ) ( methane, j" signifies that the substance dissolves in all proportions : 100 parts of Toluene dissolve 100 parts of Absolute Alcohol dissolve At 15 C. At 100 C. At 15 C. At 78 C. Naphthalene, 31-94 00 5-29 00 Phenanthrene, 33-02 00 2-62 10-08 Anthracene, 92 12-94 076 83 Pyrene, 16-54 Very soluble 1-37 3-08 Chrysene, 24 5-39 097 17 Anthraquinone, 19 2-56 05 2-25 Carbazol, 55 5-46 92 3-88 Imido - phenyl - ) aphthyl, . \ Scarcely soluble 39-'57 Scarcely soluble 25 The following data are due to W. H. Perkin (Jour. Soc. Arts, xxvii. 598): 100 parts of Petroleum Spirit boiling between 70 and 100 C. dissolve 100 parts of Coal-tar Naphtha boiling between 80 and 100 C. dissolve Phenanthrene, Anthracene, Dichloranthracene, Anthraquinone, . Carbazol, 3-207 115 137 013 016 21-94 976 52 166 51 524 REACTIONS OF SOLID HYDROCARBONS. Figures showing the behaviour of anthracene itself with various solvents are given on page 514. The comparatively slight solu- bility of anthracene in alcohol, carbon disulphide, and petroleum spirit was formerly applied to the assay of the commercial sub- stance (page 529). A process has been given by Zeidler (Ann. Ckem. Pharm., cxci. 285; Jour. Soc. Chem. Ind., i. 98) for the further separa- tion by solvents of such of the constituents of crude anthracene as are dissolved by acetic ether. COMPOUNDS OF SOLID HYDROCARBONS WITH PICRIC ACID. The constituents of crude anthracene mostly form characteristic crystalline compounds with picric acid, which have the general formula #,C 6 H 3 (N0 2 ) 3 0, in which x represents an atom of the hydrocarbon. In some instances, the reaction with picric acid affords a valuable means of recognising the hydrocarbon. The " picrates " of the hydrocarbons are usually decomposed by water or alkaline solutions and in some cases even by alcohol. To produce them, a saturated solution of the hydrocarbon in hot benzene should be mixed with an approximately equivalent quantity of picric acid, also dissolved to saturation in hot benzene, and the mixed solution then allowed to cool. In other cases alcohol may be substituted for the benzene, and for the detection of naphthalene cold alcoholic solu- tions should be employed. The following is a description of the compounds of picric acid with the more important solid hydro- carbons, &c. : Naphthalene. The only solid hydrocarbon, except pyrene and pseudophenanthrene, giving a precipitate when its cold alcoholic solution is mixed with a cold alcoholic solu- tion of picric acid. Picrate forms stellate groups of yellow needles, melting at 149 C. Diphenyl forms no definite crystalline picrate (see page 322). Acetnaphthene. Picrate forms orange-yellow needles on cooling the boiling alcoholic solution. F 1 u o r e n e. Compound crystallises from benzene in slender red needles, melting at 81. Phenanthrene. Compound crystallises from benzene in yellow needles, melting at 145 and soluble in hot alcohol without decomposition. Pseudophenanthrene. The picrate forms readily on mixing saturated cold alcoholic solutions of the hydrocarbon and picric acid. It crystallises in light red needles, melt- ing at 147. Anthracene, Picrate is deposited from solution in hot benzene in ruby-red crystals, very soluble with red colour KEACTIONS OF SOLID HYDROCARBONS. 525 in a little alcohol, the solution being decolorised and com- pound decomposed on adding more alcohol. Fluoranthrene. Compound forms reddish-yellow needles, melting at 182, difficultly soluble in cold alcohol, and decomposed by boiling with water. P y r e n e. Compound is deposited from hot alcohol as a red crystalline precipitate or long dark red needles melting at 222, nearly insoluble in cold alcohol, but very soluble in benzene and decomposed slowly by boiling with water. K e t e n e. Orange-yellow needles, readily soluble in alcohol. Chrysene. Compound crystallises from benzene in orange needles, decomposed by cold alcohol. Benzerythrene. Compound is deposited from very con- centrated hot alcoholic solutions in brownish-yellow flocks. Carbazol. Compound forms large red prisms, fusing at 182. A c r i d i n e. Forms a true picrate (see footnote, page 522). KEACTIONS OF SOLID HYDROCARBONS WITH SULPHURIC ACID. Many of the bodies occurring in crude anthracene give charac- teristic colours with concentrated sulphuric acid. These reactions have already been described. KB ACTIONS OF SOLID HYDROCARBONS WITH METALLIC CHLORIDES. With Antimony tri- chloride. With Bismuth tri- chloride. Naphthalene, pure, No coloration. During cooling, characteristic No coloration. During cooling, yellow, trans- rhombic tables form in parent needles sepa- the fused chloride. rate. Naphthalene, impure. More or less carmine More or less orange coloration. coloration. Diphenyl, No coloration. No reaction. Phenanthrene, Difficultly soluble. Faint Brown or greenish greenish coloration. brown. Anthracene, . Traces even give a Purple-black colora- yellowish green colour. tion ; very character- Colourless needles istic. formed during cooling. Dinaphthyls, . No coloration. No reaction. Pyrene, . Same as phenanthrene. Chrysene, Traces even produce ... golden yellow colour. Stilbene, C 14 H 12 , . At 40 C. smallest trace ... gives orange colour, destroyed at higher temperature. /8-Phenyl-naphthalene No reaction. Triphenyl-methane, No reaction. Greenish colour with excess. 526 REACTIONS OF SOLID HYDROCARBONS. Watson Smith has proposed to employ the fused chlorides of antimony and bismuth as reagents for the discrimination of solid hydrocarbons (Chein. News, xl. 26). For this purpose, a small quantity of the crystallised chloride is placed in a small porcelain crucible arid melted, and then further heated over a small flame. A small particle of the hydrocarbon to be tested is next placed on the side of the crucible, which is then so inclined that the melted chloride comes in contact with it. Fusion follows, accompanied in many cases by a coloration. On restoring the crucible to a vertical position, the coloured spot elongates and forms a coloured streak. Tested in this way the hydrocarbons give the reactions shown in the table on the preceding page. BEHAVIOUR OF SOLID HYDROCARBONS WITH CHROMIC ACID. When treated with oxidising agents, anthracene and many of the acid bodies occurring in association with it yield characteristic oxidation-products. The best method of obtaining these bodies is to act on the hydrocarbons by a solution of chromic acid in glacial acetic acid. When the object is to obtain the immediate products of the oxidation, the treatment should be of limited duration, and the oxidising agent should be employed in theoretical quantity or very moderate excess, but otherwise the process should be conducted as described on page 530. The following is an epitomised account of the products obtained by the action of chromic acid in acetic solution on the principal constituents of crude anthracene : Naphthalene is converted into naphthalquinone, C 10 H 6 2 , and ultimately into phthalic acid, C 8 H 6 2 , which is readily soluble in alkali. Acetnaphthene is oxidised to naphthalic acid, C 12 H 8 4 , while diphenyl yields benzoic acid, C^HgO^ Fluorene is oxidised to dip hen ylene-ke tone, C 13 H 8 0, which is volatile in a current of steam, and deposited in crystals from its solution in alcohol. Phenanthrene is transformed by the chromic acid mixture into phenanthraquinone, C 14 H 8 2 , and this is ultimately con- verted into diphenic acid, which is susceptible of still further ' oxidation and is also soluble in alkaline liquids. Phenanthra- quinone crystallises in dark orange-yellow prisms, melting at 198 C. It is sparingly soluble in hot water, but dissolves freely in benzene and acetic acid. Ignited with soda-lime it yields diphenyl, (C 6 H 5 ) 2 , in almost the theoretical proportion, whereas anthraquinone gives benzene when similarly treated. The two bodies also differ in their behaviour with the acid sulphites of the alkali-metals, with which anthraquinone does not combine. Phenanthraquinone, when BEHAVIOUR OF HYDROCARBONS WITH CHROMIC ACID. 527 warmed with solution of sodium-hydrogen sulphite, is dis- solved, and may be reprecipitated by mixing the filtered liquid with hydrochloric acid. This reaction may be used for the detec- tion of phenanthrene. The hydrocarbon is oxidised by warm chromic acid mixture, the oxidation-product treated with alkali, and then warmed with the sulphite solution. Pyrene-quinone gives a similar reaction. If a few drops of commercial toluene be added to a dilute solution of phenanthraquinone in glacial acetic acid, and, after thoroughly cooling, concentrated sulphuric acid be then added, drop by drop, and the resultant solution treated with water after a few minutes, a colouring matter separates out which is dissolved with splendid violet-blue coloration on agitation with ether. This reaction depends on the presence of methyl-thiophene, C 4 H 3 S.CH 3 , in the toluene used (see page 476). Pseudophenanthrene yields a yellow quinone, fusing at 170 and soluble with facility in alcohol and cold benzene. Anthracene is converted by the chromic acid treatment into anthraquinone, C 14 H 8 2 , which is an exceedingly stable body, resisting further action to a remarkable degree. Its pro- perties have already been fully described (see page 515). Methyl-anthracene is converted into soluble anthraquinone- carboxylic acid, C 14 H 7 2 .COOH. Fluoranthrene is converted by the chromic acid mixture into f luoranthrene-quinone, C 15 H 8 2 , and an acid soluble in alkaline liquids. Pyrene yields pyrene- quinone, C 16 H 8 2 , in slender yellow or reddish crystals. It yields finally, and with some difficulty, products soluble in alkali. Retene forms retene-quinone, C 18 H 16 2 , 1 and other pro- ducts. Retene-quinone is a brick-red powder, crystallising from alcohol in orange-yellow needles. It can be further oxidised only with great difficulty, and is insoluble in cold and dilute soda, but is dissolved by hot concentrated alkalies. Ghrysene yields chrysoquinone, C 18 H 10 2 , and is after- wards converted, with some difficulty, into phthalic acid, C 8 H 6 2 , which is readily soluble in alkali. Chrysene-quinone has a deep red colour and dissolves in strong sulphuric acid with deep indigo-blue coloration. Benzerythrene yields soluble products under the chromic acid treatment. Chrysogene, said to exist in considerable quantity in certain kinds of anthracene (see page 520), is alleged to be completely and 1 Not dioxyretistene, C 16 H 14 Oo, as was formerly supposed. 528 ASSAY OF CRUDE ANTHRACENE. readily converted into soluble products by the chromic acid mixture. This is doubtful, for, Imido-plienylnaphthyl (described on page 521) yields a quinone of the formula C l6 H 9 N 2 2 , which forms reddish-yellow needles and obstinately resists further oxidation. It appears always to be pro- duced by the oxidation of anthracenes which give banded absorp- tion-spectra of the nature described on page 521, and leads to excessive estimates of the yield of real anthracene. The quinone is destroyed by prolonged treatment with fuming sulphuric acid at 100 C. The paraffin, the presence of which in crude anthracene is referred to on page 520, is practically unaltered by treatment with the chromic acid mixture. A dark-green hydrocarbon, fusing at 271 C., is occasionally present in anthracene. It is soluble with difficulty in glacial acetic acid, and should, if present, be separated as far as possible by this solvent before employing the chromic acid mixture, as its oxidation is very difficult to effect. Assay of Crude Anthracene. 1 Commercial crude anthracene is a green or brownish-green friable mass or crystalline powder. It contains a very variable percentage of real anthracene, the usual proportion being from 30 to 40 per cent., though formerly 15 per cent, was common, and special makes now assay over 80 per cent. 2 It cannot be too strongly insisted on that the true value of a sample of crude anthracene is dependent not merely on the proportion of real anthracene contained in it, but also on its comparative freedom from objectionable impurities. The paraffin referred to on page 520 as existing in Scotch and north-country anthracenes greatly reduces the value of the product and even renders some batches wholly unmarketable. It has a high melting point, and very limited solubility in either petroleum or coal-tar naphtha. It dissolves in the hot liquids, but is almost entirely deposited on cooling. A small percentage of this paraffin greatly impedes the subsequent treatment of the anthracene, and, being a very stable substance, it passes through most of the pro- cesses unchanged. Experience has proved that in the operation of oxidising anthracene on a large scale by treatment with potassium bichromate and dilute sulphuric acid, all other admixtures may be 1 For a perusal of the entire article on " Anthracene and its Associates," and for the communication of a number of valuable facts and suggestions, the author is indebted to Messrs D. B e n d i x and B. Nickels. 2 Sublimed anthracene has been made on a large scale containing upwards of 90 per cent, of real anthracene, but the manufacture is no longer carried on. ASSAY OF CRUDE ANTHRACENE. 529 dealt with and to a great extent removed, but paraffin resists the oxidising action, melts, and retards the operations to a hopeless extent.- Hence a search for this objectionable impurity should never be omitted, unless it be known to a certainty that bituminous shale or cannel coal has had no share in the production of the sample. It may be detected and determined in crude anthracene in the following manner: 10 grammes weight of the sample is treated with 200 grammes (=108 c.c.) of strong sulphuric acid. The mixture is heated on a water-bath for about ten minutes, or until the anthracene is completely dissolved. Any considerable quantity of paraffin will rise to the surface in the form of oily globules. The solution obtained is cautiously poured into 500 c.c. of water contained in a tall beaker. After being thoroughly stirred the liquid is allowed to cool, when any paraffin will rise to the surface, and having solidified, can be removed, washed with a little cold water, dried between blotting paper, and weighed. From 2 to 5 per cent, is the quantity commonly present in Scotch anthracenes. According to B. Nickels (Chem. Neivs, xl. 270; xli. 52, 95, 117), samples of crude anthracene containing imido-pJienylnaphthyl (page 521) give a highly characteristic absorption-spectrum, show- ing two broad and well-defined black bands between the F and G lines and another slightly more refrangible than G. Samples exhibiting these bands are purified with some difficulty, and yield by oxidation an impure anthraquinone containing many amorphous particles. For observing the spectrum of the sample, a few grains should be dissolved in 6 c.c. of warm benzene, the liquid passed through a dry filter, and observed with a spectroscope. A micro- spectroscope may be employed, or, in its ^absence, a direct- vision pocket spectroscope will suffice. The intensity of the absorp- tion-bands is a measure of the objectionable impurities of the sample. For the quantitative assay of commercial anthracene, three pro- cesses based upon the behaviour of real anthracene and the asso- ciated impurities with solvents have been employed. In one of these alcohol was used ; in the second, carbon disulphide ; and in the third the sample was subjected to successive treatment with petroleum spirit and carbon disulphide. The method of perform- ing these tests need not be given in detail, as they are now prac- tically obsolete. 1 1 The principle of the solution-tests was so far the same that advantage was taken of the greater solubility of the impurities than of anthracene itself. Alcohol always yielded a higher percentage of residue with a low melting point, while carbon disulphide gave a lower percentage of residue of high melting point. VOL. II. 2 L 530 ANTHRAQUINONE TEST. ANTHRAQTJINONE TEST. The most satisfactory method of assaying crude anthracene is based on the conversion of the anthracene, by the action of chromic acid, into anthraquinone (page 515). This is a characteristic, insoluble body, not liable to further change, while nearly all the associates of anthracene are, by the same treatment, either completely oxidised or else converted into pro- ducts readily removed by water or dilute alkali (see page 526). The method of assaying anthracene by conversion into anthra- quinone was first proposed by E. L ii c k, and, with the various modifications of the process which have been intro- duced from time to time as experience of the sources of error has become greater, the method affords a very satis- factory solution of a difficult problem. The following mode Jof operating is essentially that of Meister, Lucius, and B r ii n i n g, with some precautions and modifications recommended by G. E. and T. H. Davis, who verified the accuracy of the method by operating on pure anthra- cene and impure samples of known composition: 1 1 gramme of the carefully sampled specimen is placed in a flask holding 500 c.c. 45 c.c. of the very strongest glacial acetic acid is then added, and an inverted condenser or long glass tube adapted to the flask. The liquid is then brought to the boiling point, and, while boiling, the chromic acid is A added to it gradually, drop by drop, by means of a tapped /\ funnel passing through the india-rubber stopper of the flask, ( j or inserted in the top of the vertical condenser (fig. 17). \ The chromic acid solution is prepared by dissolving 15 lg ' ' grammes of crystallised chromic anhydride (perfectly free from lead salts and insoluble matter generally) in 10 c.c. of water and 10 of glacial acetic acid. The addition of the oxidising agent should occupy two hours, and the contents of the flask should be kept in continued ebullition for two hours longer, four hours in all being necessary to ensure complete oxidation of the impurities. There was ho fixed relation between the two results, while the residues themselves varied greatly in composition ; hence the tests are now seldom if ever used. The fluid portion of anthracene oil is itself the best solvent for all the solid hydro- carbons, including anthracene ; and hence, when a sample of crude anthracene containing much liquid oil is treated with a solvent, the combined action of the oil and the solvent removes considerably more anthracene than the solvent alone. This was one of the causes of the discrepancies in anthracene assays made by alcohol or carbon disulphide, a soft sample containing much oil always showing a lower percentage of anthracene than the same sample previously pressed and separated from the oil. 1 This test is commercially known as "Meister, Lucius, and Briining's anthraquinone test, with appendix. " ASSAY OF ANTHRACENE. 531 The flask is then left at rest for twelve hours, when the contents should be diluted with 400 c.c. of cold water, 1 and allowed to rest another three hours. The precipitated anthraquinone is then filtered off and well washed with cold water. It is next washed on the filter with a boiling hot 1 per cent, solution -of caustic soda, and again thoroughly washed with boiling water, about 300 c.c. being employed. The anthraquinone, which should exhibit no alkaline reaction, is then rinsed from the filter into a small dish by means of a jet of water, the water is evaporated off, and the residue dried at 100 C. and weighed. The anthraquinone obtained in the foregoing manner is rarely sufficiently pure to allow of the percentage of real anthracene in the sample being at once calculated from its weight. Several methods have been proposed for the further purification of the crude product, but the following improved " appendix " by Meister, Lucius, and B r ii n i n g 2 (Ghem. News, xxxiv. 1 67) is now universally employed. The crude anthraquinone is mixed, in the dish in which it was weighed, with ten times its weight of fuming sulphuric acid having a specific gravity of 1*880 at 60 F., 3 and the whole heated to 100 C. on a water-bath for ten minutes. The solution obtained is next left in a damp place for twelve hours to absorb water. 200 c.c. of cold water are then added, the pre- cipitated anthraquinone collected on a filter, and washed free from acid with cold water, then with about 100 c.c. of boiling dilute soda solution (1 per cent.), and finally with about 400 c.c. of boiling water. 4 The greater part of the moist anthraquinone is then transferred to a flat platinum or porcelain dteh by means of a spatula, the remaining portion being rinsed off the filter into the dish by means 1 The use of this large proportion of water ensures the complete precipitation of the anthraquinone, and renders it unnecessary to make a correction of 10 milligrammes for its solubility in the acetic solution, as was formerly done. (See Versmann, Chem. News, xxxiv. 188, and R. Lucas, xxxiv. 267). 2 Commercially known as the "sulphuric acid test of October 1876." 3 The authors adopted the treatment with sulphuric acid described in the text, and now generally employed in preference to one with potassium per- manganate formerly recommended by them. The strength and quantity of the acid prescribed must be strictly adhered to. Pure acid of the exact strength is obtainable from Chapman, Messel & Co., Silvertown, E. 4 The character of the quinone is an indication of its purity, a deep yellow or orange tint indicating the presence of phenanthrene- or chrysene-quinone. The latter body is also recognised by the production of an indigo-blue colora- tion on adding the sulphuric acid. "With impure anthraquinones both the acid filtrate and the alkaline washings are deeply coloured } brown, purplish, and bluish tints being the most common. 532 ANTHRAQUINONE TEST. of a fine jet of water. The water is then evaporated off at 100, and the residue weighed. 1 The weight of anthraquinone thus obtained ought not to be regarded as representing that of the pure product, as it usually con- tains extraneous matters, such as sand, and very frequently oxide of chromium. Some anthracenes yield anthraquinones which carry down much Cr 2 3 in combination. Hence the dish should be gradually heated so as completely to sublime the anthraquinone, and the residue obtained deducted from the weight previously found. This corrected weight of the anthraquinone, multiplied by the factor 0'856, gives the real anthracene in the weight of the sample employed. The anthraquinone obtained by the above process should be crystallised, and of a uniform pale-yellow colour. The purer it is the paler the colour. Certain strange quinones are apt to be present in some cases, and are recognisable by the modified form of the crystals and the colour of the product. Phenanthraquinone is orange, and chrysene-quinone deep red. Continued treatment with the chromic acid mixture removes all these bodies, but does not affect the quinone, C 16 H 9 N0 2 , produced by the oxidation of imido-phenylnaphthyl referred to on pages 521 and 529 as giving a characteristic absorption-spectrum. This quinone, unlike those from phenanthrene, chrysene, &c., tends to prevent the crystallisa- tion of the anthraquinone, and is one of the sources of the so-called " amorphous particles " which are frequently present in sufficient quantity to obliterate all trace of crystallisation in the oxidised product. This troublesome impurity may, however, be destroyed 1 An alternative method is to dry the anthraquinone on the filter, and then carefully remove it with a knife. This plan is apt to cause a loss, varying from 4 to 8 milligrammes, through, incomplete removal of the substance. To avoid this, the stained portion of the filter should be cut small and heated in a test-tr>e with about 1 c.c. of benzene. The resultant solution is poured off into a small dish, and the residue obtained by its evaporation added to the main quantity of anthraquinone. The difference in the result caused by the benzene treatment often amounts to 0'2 per cent, of the crude anthracene, owing to the loss in the other methods by imperfect removal from the filter. Hence, when accurate results are required, or the analyst is not tied down by the conditions of the contract-note, treatment of the filter with benzene should never be neglected. Either of the foregoing methods of treatment is preferable to weighing the anthraquinone on the filter, which is apt to be altered in weight by the reagents employed, though this source of error may be to a great extent avoided by using a double filter, the apex of the outer one being cut off. The weights of the two filters are accurately adjusted before use by trim- ming with a pair of scissors, and on weighing the anthraquinone the outer filter is used as a counterpoise to the inner. ANTHRACENE IN TAR. 533 by a somewhat longer-continued heating with sulphuric acid in the manner already described, and hence this supplementary treat- ment should never be omitted in the case of samples which originally yielded absorption-bands, or which have produced crude anthraquinones of unhealthy appearance. 1 DETERMINATION OF ANTHRACENE IN TAR AND PITCH. For the determination of anthracene in coal tar, Carl Nicol (Zeits. Anal. Chem., xiv. 318; Jour. Chem. Soc., xxx. 553) dis- tils 20 grammes in a small luted retort, and the vapours are received in a U-tube, kept at 200 C. by being immersed in a bath of hot paraffin. The more volatile products are not condensed, but the anthracene and other hydrocarbons of high, boiling point collect in the U-tube. Care must be taken to prevent bumping, and the condensation of the distillate on the neck and sides of the retort. When the contents of the retort become coked, the process is stopped and the neck is cut off, pounded, and the powder added to the distillate. The whole is then dissolved in glacial acetic acid, and subjected to oxidation with the chromic acid mixture, in the manner already described. Watson Smith writes adversely of this process, considering 20 grammes far too small a quantity of tar. He himself employs a similar method, but operates on at least a litre, and rejects the portion distilling just before coking, as it contains much resinous matter of an objectionable kind, and would not in practice be treated for anthracene. The anthracene oil is well mixed and an aliquot part oxidised. In some cases it is preferable to reject the fraction distilling be- tween 200 and 250 C., as it contains little or no anthracene, and in tars rich in naphthalene is so large in quantity as materially to impede the subsequent treatment. The anthracene may be further concentrated by cooling the heavy oils to a low temperature, filter- ing, and pressing the deposit of solid hydrocarbons between folds of filter- paper. The crude anthracene thus obtained is then oxidised to anthraquinone in the usual way. Ordinary gas-works coal tar contains from 0'3 to 0*5 per cent, of real anthracene, but from the tar obtained from Simon-Carve coke-ovens, Watson Smith obtained 0*73 per cent, of anthracene, and A. H. Elliott found as much as 2 '63 per cent, in the tar produced in the manu- facture of water-gas from petroleum naphtha. i R. Lucas (Chem. News, xxxiv. 267) has proposed to supplement the sulphuric acid treatment by re-treating the product with the chromic acid mixture, exactly like the original sample of anthracene. It must not be forgotten, however, that anthraquinone itself does not wholly resist the oxidising treatment, and hence the cases in which the proposal of Lucas can be advantageously adopted .are very rare. PHENOLS. THE bodies known to chemists as phenols belong to the aromatic series, and are intermediate in character between acids and the true aromatic alcohols of which benzylic alcohol is the type. THE MONOHYDRIC PHENOLS have the general formula C n H 2n _ 7 .OH. Of these, carbolic acid and cresylic acid are described in the following sections. Thymol, C 10 H 13 .OH, which is a higher homologue of these bodies, has already been considered (page 447). The naphthols, C 10 H r .OH, which are closely related to the monatomic phenols, are described on page 510. THE DIHYDEIC or HYDROXY-PHENOLS, C n H2 n _ 8 .(OH) 2 , are de- scribed on page 560. Catechol (or pyrocatechin), resor- c i n o 1, and q u i n o 1 (or hydroquinone) are isomeric bodies of the formula C 6 H 4 :(OH)2. r c i n o 1 or o'rcin, C 7 H 6 :(OH) 2 , obtained from various lichens, is a phenol homologous with resorcinol. THE TRIHYDRIC or DIHYDROXY-PHENOLS, pyrogallol and phloroglucol, C 6 H 3 (OH) 3 , will be described in the chapter on "Tannins" (vol. iii.). Certain ethers of catechol and pyrogallol are described in the section on "Wood-tar Creosote" (page 564), in which liquid they are present in large proportion. MONOHYDRIC PHENOLS. C n H 2n _ 7 .OH. The monohydric phenols form a homologous series, of which phenol proper or carbolic acid is the first member, and the cresols form the next homologue. Of the higher members of the series, some exist in the tars pro- duced by the distillation of coal (page 354), wood, &c. (e.g. xylenols), others in certain natural essential oils (e.g, thymol), while others have hitherto been obtained by synthetical reactions only. The higher monohydric phenols present a close resemblance to carbolic acid in their general characteristics. They may be distilled without decomposition, and are but slightly soluble in water, but readily in aqueous alkalies, alcohol, ether, &c. The monohydric phenols may be regarded as being formed from PHENOLS AND AKOMATIC ALCOHOLS. 535 benzene and its homologues by the substitution of an atom of hydroxyl, OH, for an atom of hydrogen on the principal chain (see page 535). All but the lowest term are susceptible of isomeric modifications, according to the relative positions of the hydroxyl and other substituted radicals in the benzene nucleus. The probable difference in structure between the monohydric phenols and the true aromatic alcohols, typified by benzylic alcohol, is shown by the following example, all four bodies having an ulti- mate composition corresponding to the formula C7H 8 0: Varieties of Cresylic Acid or Benzyl Alcohol or Methyl-phenol. Fhenyl-carbinol. Ortho-eresol (1 : 2). Meta-cresol (1 : 3). Para-cresol (1 : 4). OH OH OH CH 2 .OH 'CH 3 The monohydric phenols are distinguished from the alcohols of the benzylic series by the following reactions: a. The haloid acids are without action on the phenols, but hydrochloric acid converts benzylic alcohol (e.g.) into benzyl chloride, C 6 H 5 .CH 2 C1. b. Carbolic acid readily dissolves in concentrated sulphuric acid to form phenol-sulphonic acid, C 6 H 4 (OH).S0 3 H, while benzylic alcohol is resinified by similar treatment. c. On treatment with oxidising agents, the phenols yield quinones (e.g., benzo-quinone, C 6 H 4 2 ), but benzylic. alcohol yields benzoic acid, C-jH 6 2 . d. Nitric acid converts the phenols into well-characterised nitro-derivati ves of acid character (e.g., trinitrophenol or picric acid, C 6 H 2 (N0 2 ) 3 .OH ); but benzylic alcohol is oxidised by the same reagent to benzoic aldehyde and benzoic acid. e. The phenols dissolve in solutions of caustic alkalies to form com- pounds in which they play the part of an a c i d. The acid character of the phenols is less marked in the higher members of the series, but the chloro- and nitro-derivatives have strongly acid properties, not only dissolving in solutions of alkaline hydroxides, but decomposing carbonates with effervescence and forming definite and stable salts. /. Ferric chloride produces a characteristic blue or violet colour with many of the phenols and their derivatives. g. On adding hydrochloric acid to the aqueous solution of a phenol, immersing a slip of deal in the liquid and allowing the wood to dry, a blue colour is developed. 536 PHENOL OE CAEBOLIC ACID. Ti. The phenols react immediately with excess of bromine water to form bromo-derivatives (usually containing Br 3 ), which are usually white or yellowish insoluble or nearly insoluble bodies. The reactions of the phenols of service for their recognition are described more in detail on page 539. Phenol. 1 Carbolic Acid. PhenicAcid. Phenylic Hydrate. Phenylic Alcohol. Hydroxybenzene. C 6 H 6 = C 6 H 5 .OH = 6 ^ | o . Phenol is stated to exist ready-formed in nature, 2 and is pro- duced in various analytical and synthetical reactions, 3 but the only source of commercial interest is the fraction of coal tar distilling between 150 and 200 C. On treating this with caustic soda, phenol and its homologues are dissolved, together with a certain amount of naphthalene and other indifferent bodies. These are partially precipitated on diluting the alkaline liquid, and others become oxidised on exposing the solution to the air. On treating the liquid with an excess of sulphuric acid, the liberated phenols form an oily layer which is separated from the aqueous liquid. From the crude carbolic acid so obtained pure phenol is obtained by fractional neutralisation, the homologues having less defined acid properties. On again liberating the phenol from its sodium com- pound a product is obtained which is fractionally distilled. The portion passing over within a few degrees of 182 C. is subjected to a freezing mixture, when crystals of phenol form which are separated from the liquid by a centrifugal machine. The product may be further purified by a repetition of the process. Pure phenol is a colourless solid, crystallising in long needles, and melting at 42 '2 C. (=108 F.) 4 to a colourless, limpid fluid, 1 The name "phenol" is applied genetically to bodies of the aromatic series having properties allied to true alcohols and also to acids (see page 534). "When used without qualification and as a proper name, the term "phenol" is to be understood as applying to the body of the above formula, the most impor- tant and best known member of the genus, just as the name "alcohol," em- ployed under similar conditions, is always understood to mean ethylic alcohol, 2 Free phenol is alleged to exist in various proportions in the leaves, stem, and cones of Pinus sylvestris. Phenol is said to be a product of putrefaction under certain conditions. 3 Pure phenol may be conveniently prepared on the small scale by heating crystallised salicylic acid strongly and rapidly in a glass retort, either alone or mixed with pounded glass or quicklime. Phenol passes over into the receiver, and crystallises almost to the last drop. 4 Specimens of carbolic acid having a lower melting point than 42 C. con- tain cresylic acid or water. PROPERTIES OF PHENOL. 537 slightly heavier than water. When pure and free from cresol, phenol boils at 182 C., and distils without decomposition. The taste of carbolic acid is biting, but at the same time sweet. The odour is usually strong and characteristic, but both smell and taste are much less marked in very pure specimens than in the crude article. The crystals of phenol readily absorb water from the air, whereby the fusing point is lowered, owing to the formation of a hydrate, of the formula 2C 6 H 6 0-j-H 2 0, This hydrate con- tains 874 per cent, of water, and melts at 17*2 C, ( = 63 F.). It forms large six-sided prisms, which in very moist air absorb still more water, forming a product which is fluid at ordinary tem- peratures. When cold water is gradually added to absolute phenol as long as it continues to be dissolved, a liquid is obtained which contains about 73 per cent, of phenol and 27 of water. This approximately agrees with the composition of a hydrate of the formula, C 6 H 6 + 2H 2 ; but the fact is probably merely a coincidence,, as the pro- portion of water depends greatly on the temperature, and the liquid gives up its phenol to benzene, and deposits crystals of the hydrate melting at 17 '2 C. when subjected to a freezing mixture. Liquid hydrous carbolic acid dissolves in about 11 '1 times its measure of cold water. This corresponds to a solubility of 1 part by weight in 10'7 for the absolute acid, the saturated solution con- taining 8 '5 6 per cent, of real phenol. 1 In hot water, phenol is greatly more soluble, and is miscible in all proportions at about 70 C. In water saturated with sodium chloride or sulphate, carbolic acid is but very slightly soluble. Carbolic acid is miscible in all proportions with alcohol, glacial acetic acid, and glycerin. Anhydrous phenol is miscible in all proportions with ether, ben- zene, carbon disulphide, and chloroform. When aqueous carbolic acid is shaken with excess of either of these solvents, the phenol dissolves and the contained water is separated. In cold petroleum spirit, carbolic acid is but slightly soluble. 2 1 These statements are the result of the writer's own experience (Pliarm. Jour., [3], ix. 234). The solubility is often grossly misstated, partly owing to the use of an acid containing cresol, and partly from a confusion between the absolute and the hydrated acid. This mistake occurs in the most recent con- tribution to the subject (Pharm. Jour., [3], xiv. 207). 2 For details of its behaviour, see page 388. The statements here made re- specting the solubility of carbolic acid in water and other solvents are all the results of the writer's personal experience. The details of the investigation are published in the Analyst, iii. 319, and in the Year Book of Pharmacy, 1878, page 575. 538 REACTIONS OF PHENOL. Phenol coagulates albumin, is a powerful antiseptic, acts as a caustic on the skin, and is powerfully poisonous. It appears to act on the system by paralysing the nerve-centres. The effect of even momentary contact of the strong acid with any considerable surface of the lower part of the body is apt to be fatal, but it has often been applied to the arms with comparative impunity. Strong carbolic acid dissolves gelatin completely, but it coagu- lates it when added to its aqueous solution. Indigo-blue (indigotin) is soluble in hot phenol, and may be obtained in crystals on cooling the liquid. By the action of fused caustic soda on phenol, phloglucol, catechol, and resorcinol are formed, together with other products ; but the action of caustic potash is entirely different. Carbolic acid is converted by the action of chlorine and bromine into chloro- and bromo-deri va ti ves (page 540). Nitric acid acts on it with formation of mono-, di-, or tri- nitrophenol; the last of these being identical with picric acid, C 6 H 2 (N0 2 ) 3 .OH. Concentrated sulphuric acid converts car- bolic acid into phenol-sulphonicacids. In the presence of bodies which can furnish methane-carbon, together with free mineral acids and oxygen, para-rosolic acid, C 19 H 14 3 , is formed. An aqueous solution of hydrogen peroxide gradually added to pure phenol oxidises it with formation of catechol, quinol (hydroauinone), and q u i n o n e. PHENATES. Although aqueous solutions of phenol do not redden litmus, carbolic acid is much more soluble in weak alkaline solutions than in pure water. With equivalent amounts of the strong bases it forms compounds which are difficult to obtain in a definite form. The potassium and sodium salts are readily soluble in water, and the solutions are not decomposed on dilution. Potassium phenate, C 6 H 5 .OK, obtained by heating phenol with potassium or with solid caustic potash, crystallises in slender white needles soluble in ether. On heating potassium phenate with the iodides of methyl, ethyl, and amyl, the corresponding ethers are produced. Methyl phenate or a n i s o i 1, C 6 H 5 .OCH 3 , is a mobile liquid of pleasant aromatic odour, having a density of 0'991 and distilling unchanged at 152. It dissolves in strong sulphuric acid to form methyl-phenol-sulphonic orsulphanisoilic acid, and with bromine yields substitu- tion-products. Ethyl phenate and amyl phenate re- semble the methylic ether. ETHERS OF PHENOL. Besides the foregoing bodies, in which phenyl, C 6 H 5 , plays DETECTION OF PHENOL. 539 the part of an acid-radical, a series of phenylic salts are known, but have little practical importance. The production of phenylic ortho-oxalate has been observed to occur in the manufacture of aurin (Jour. Soc. Ghem. Ind., ii. 345), and phenylic sali- c y 1 a t e has been recently introduced as an antiseptic under the name of "salol" (Pharm. Jour., [3], xvii. 273). DETECTION AND DETERMINATION OF PHENOL. The following reactions are in most cases common to carbolic and cresylic acids. They do not require that the substance should be in a concentrated state, but are applicable to the aqueous solution. They have mostly been verified by the author. Various other reactions of carbolic acid are described in the sections on " Cresylic Acid "and "Creosote." a. When a drop of a dilute aqueous solution of carbolic acid is added to a few drops of a solution of 1 gramme of molybdic acid in 10 c.c. of concentrated sulphuric acid, contained in a porcelain crucible, a yellowish-brown coloration is produced, which rapidly changes to purple, the latter tint being tolerably permanent. Warming the mixture to about 50 C. greatly assists the reaction, but a higher temperature must be avoided. As this delicate reac- tion depends on the deoxidation of the molybdic acid, a great many substances interfere with this test. b. Ferric chloride (avoiding excess) gives a fine violet colour, by which 1 part of phenol in 3000 of water can be detected. Many allied bodies give a similar reaction (see pages 562, 569). The presence of common salt, nitre, or boric acid is unobjectionable, but the reaction is hindered by most mineral and organic acids, acetates, borax, sodium phosphate, glycerin, alcohol, amylic alcohol, and ether. c. If an aqueous solution of phenol be gently warmed with ammonia and a solution of sodium hypochlorite (avoiding excess) a deep blue colour is obtained, which is permanent, but turns to red on addition of acids. Solutions containing 1 of phenol in 5000 of water react well when 20 c.c. are employed. Much smaller quan- tities give the reaction after a time. A modified, and in some respects preferable, method of performing the test is to add to 50 c.c. of the aqueous liquid to be tested 5 c.c. of dilute ammonia (1 measure of ammonia of '880 specific gravity with 9 parts of water), and then drop in fresh and dilute bromine water very slowly, avoiding excess. The presence of phenol will be indicated by the production of a fine blue tint, which is very permanent. A still better plan is to expose the ammoniacal liquid to the vapour of bromine, avoiding excess of the latter. d. According to E. J a c q u e m i n, if to a neutral solution of 540 RE ACTION OF PHENOL WITH BROMINE. phenol a minute quantity of aniline be first added, and then a solution of sodium hypochlorite be dropped in, the reagent pro- duces yellow striae which change to a greenish blue. The reaction is said to be very delicate. e. If 20 c.c. of a dilute phenol solution be boiled with 5 or 10 drops of Millon's reagent, 1 and nitric acid added drop by drop to the hot solution, until the precipitate is redissolved, the mixture assumes a fine blood-red colour which is permanent for several days. The reaction is exceedingly delicate, but is not peculiar to phenol E. Hoffmann modifies this test by pouring 2 or 3 c.c. of the liquid supposed to contain phenol on to the surface of an equal measure of strong sulphuric acid, so as not to cause the liquids to become mixed. A few granules of potassium nitrite are then dropped in, when each particle will produce violet streaks if even a very minute quantity of carbolic acid be present. Liebermann has observed that strong sulphuric acid, to which a 6 per cent, solution of potassium, nitrite has been added, gives a brown coloration,' changing to green and blue when gently warmed with phenol or its allies. /. Reaction of Phenol with Bromine. "When bromine water is added in moderate excess to an aqueous solution of phenol, a snow- white crystalline precipitate is formed, which readily collects into flocks on agitation, and appears under the microscope in the form of fine stellated needles. In presence of much cresylic acid or certain other phenols, the precipitate loses its crystalline character, and may even assume the form of yellow or reddish oily globules. In extremely dilute solutions the precipitate is only produced slowly ; but in twenty-four hours a solution containing g^^K^j ^ phenol gives the reaction. The reaction with bromine was employed by Landolt to demon- strate the effect of a gas-works on the water of the neighbouring- wells; but the production of a white or yellowish precipitate with bromine water is by no means conclusive evidence of the presence of carbolic acid, a similar reaction being produced by homologues of carbolic acid (e.g., cresylic acid, thymol), besides other phenoloid bodies (e.g., guaiacol, orcinol, pyrogallol, phloroglucol), salicylic acid, aniline, and various alkaloids. On gradually adding bromine to a moderately concentrated solu- tion of pure phenol, in a proportion not exceeding that necessary for the reaction C 6 H 5 .OH + Br 2 = C 6 H 4 Br.OH + HBr, a white turbidity is produced owing to the formation of the sparingly soluble monobrom -phenol. If the solution be dilute, no 1 Prepared by dissolving mercury in fuming nitric acid, boiling, and diluting the solution with two measures of water. TRIBROMOPHENOL. 541 actual precipitation occurs at this stage. On adding more bromine water, a formation of dibromophenol, C 6 H 3 Br 2 .OH, takes place, but often no further precipitation occurs until the bromine added exceeds the proportion : C 6 H 5 .OH : Br 4 . On further addi- tion of bromine a very bulky precipitate is produced, and when the proportion of phenol employed is to that of the bromine added as C 6 H 5 .OH : Br 6 , the whole is separated as the insoluble and characteristic tribromophenol, C (5 H 2 Br 3 .OH. 1 It was sup- posed till recently that this body was the final product of the reaction of bromine on phenol in aqueous solution, though t e t r a- and penta-brom-phenols could be obtained under other con- ditions, but it has been shown by the researches of Werner and of W e i n r e b and B o n d i (Compt. Rend., c. 799 ; Monatsh. Chem., vi. 506; Jour. Chem. Soc., xlviii. 658, 1266) that by the action 1 TRIBROMOPHENOL. Tribromophenic acid. C 6 H 2 Br 3 .OH. This body has a very peculiar and persistent odour, melts at 92 C., and readily volatilises. It is almost insoluble in water and dilute acid liquids, but is readily soluble in ether, chloroform, carbon disulphide, &c. It dissolves in absolute alcohol, but is precipitated from the solution by a very small quantity of water. Tribromophenol has marked acid properties. It dissolves in the fixed alkalies and in ammonia, and the latter solution yields on evaporation sparingly soluble crystalline needles of ammonium tribromophen- at e, NH 4 .O.C 6 H 2 Br 3 . The solution of this salt gives other tribromophenates by double decomposition. The metallic solutions must be perfectly neutral or a flocculent precipitate of tribromophenic acid will be obtained. The silver salt forms an orange-yellow flocculent precipitate, the c u p r i c salt is reddish- brown and floceulent, and the lead salt white. The nickel salt is in- soluble and dark red, but no precipitate is obtained with solutions of c o b a 1 1. The author has investigated the reactions of the tribromophenates with a view of finding a means of estimating phenol and cresol in mixtures of the two, but has met with but very partial success, partly owing to the difficulty of preparing a soluble salt of tribromocresol. The following differences were observed in the reactions with neutral solutions of metallic salts of ammonium tribromophenate and sodium tribromocresolate from coal-tar cresol : With Solution of Phenol-derivative. Cresol-derivative. Silver nitrate, . Nickel sulphate, Cobalt nitrate, Calcium chloride, . Barium chloride, Magnesium sulphate, Orange-yellow, floccu- lent. Dark red, dissolved on boiling. No precipitate. No precipitate. White, crystalline, readily soluble in hot alcohol. No precipitate. Cream coloured, floccu- lent. Dark red, not dissolved on boiling. Light brown, flocculent. White, flocculent. White, flocculent, not readily dissolved by hot alcohol. White, flocculent. 542 BROMOPHENOLS. of excess of bromine the hydrogen of the hydroxyl is replaced, in addition to three atoms of the phenylic hydrogen, the reaction being : C 6 H 5 .OH + Br 8 = C 6 H 2 Br 3 .OBr + 4HBr. 1 The new body, bromoxy-tribromophenol, crystallises in scales, is gradually 1 The following table shows the leading properties of the bromophenols hitherto obtained : Formula. Name. Constitu- tion. Appearance. Melting Point ; C. Boiling Point ; C. OH:Br: 1. Ortho-monobromo- 1:2 Colourless oil, 194 to 195 phenol, 2. Meta-monobromo- phenol, 1:3 Laminar, colour- less mass, 32 to 33 236 to 237 3. Para-monobromo- 1:4 Large monoclinic 64 236 C 6 H 3 Br 2 .OH phenol. 4. Para-orthodibromo- 1:2:4 prisms, Colourless satiny 40 C 6 H 3 Br 3 .OH phenol, 5. Para-diortho-tribro- 1:2:4:6 prisms. White silky 92 C 6 H 2 Br 3 .OBr mophenol, 6. Bromoxytribromo- ... needles, Crystalline scales, ... phenol, C 6 HBr 4 .OH 7. Tetrabrom-phenol, ... Colourless needles, 120 ... C 6 Br 5 .OH 8. Pentabrom-phenol, ... Colourless needles, 225 By the gradual addition of bromine water to phenol, a mixture of bodies 1 and 3 appears first to be formed, and this, by further addition of bromine water, is converted in succession into the bodies 4, 5,. and 6. Para-monobromophenol may be conveniently obtained by the action of bro- mine vapour on an equivalent amount of crystallised phenol (i.e., 160 parts of bromine to 94 of phenol). Although its melting point is 64, it remains liquid at 13 C. Para-ortho-dibromophenol may be obtained by the same method, using twice as much bromine. It remains fused at 12 C. The solu- bility in water of the two foregoing compounds, and of the tribromophenol into which they are converted by excess of bromine, has been determined by E. Werner (Compt. Rend., xcviii. 1333), who gives the following figures: Monobromophenol, C 6 H 4 Br. OH Dibromophenol, C 6 H 3 Br 2 .OH Tribromophenol, C 6 H 2 Br 3 .OH Solubility at 15 C. 14-22 grammes per litre. 1-94 0-07 The bromo-derivatives of phenol are tolerably stable, more or less volatile, and easily soluble in alcohol, ether, chloroform, carbon disulphide, and glacial acetic acid. They possess acid properties, and the di- and tri-bromo-derivatives form well-defined series of metallic salts, some of which crystallise well. On treatment with nitric acid the bromophenols form a series of nitrobromo- phenols, which are yellow crystalline bodies of pronounced acid properties, furnishing most beautiful crystallised salts, varying in colour from yellow to brilliant crimson, and more or less soluble in water. The mono- and di-bromo- phenols yield sulphonic acids, but tribromophenol is not acted on by strong sulphuric acid. DETERMINATION OF PHENOL BY BROMINE. 543 decomposed by water, and reacts with potassium iodide in acid solution according to the equation : C 6 H 2 Br 3 .OBr + 2KI + 2HC1 = C 6 H 2 Br 3 . OH + 2KC1 + 2HBr + 21 . Neither the free iodine nor an excess of potassium iodide has any effect on the tribromophenol. Hence, if it be desired to determine the amount of phenol in an aqueous liquid, it may be effected by adding bromine water in excess, followed by potassium iodide, and then titrating back with a standard solution of sodium thiosulphate in the usual manner. Operating in this manner, it is a matter of indifference whether C 6 H 2 Br 3 .OH or C 6 H 2 Br 3 .OBr be first formed, as by the subsequent treatment with potassium iodide the latter body is converted into the former. The formation of tribromophenol as a means of determining phenol was first suggested by Landolt, who operated gravi- metrically. The method was greatly improved byKoppeschaar, who devised a volumetric process. This method has been modified by various chemists with more or less advantage. A very simple means of determining carbolic acid in soap by direct titration with bromine water is given on page 256, but the process there described is not adapted to yield results of more than approximate accuracy. Very good results are obtainable by the wet bromine process of determining olefins described on page 333. 2 In some cases it is preferable to substitute for the bromine water a standard solution of sodium bromate of known strength. A known quantity of the sample to be examined (containing from 0*2 to 0'5 of phenol) is introduced into a stoppered flask, together with a solution of potassium bromide and some dilute hydrochloric acid, and the liquid then diluted to about 100 c.c. with water. A known volume of the standard solution of sodium bromate is then run in, sufficient being used to ensure a permanent reddish coloration due to excess of bromine. The bromate solution should contain 15*1 grammes of NaBr0 3 per litre. The flask is then closely stopped, well shaken, and allowed to stand at rest for half an hour to ensure the completion of the reaction. By the reaction 5KBr + NaBr0 3 H-6HCl = 5KCl + NaCl + Br 6 + 3H 2 0, bromine is set free, and acts on the phenol. A solution of potassium iodide is then added in excess, and the liquid titrated back with a decinormal solution of sodium thiosulphate (hyposulphite, 24*8 grammes of crystallised Na 2 S 2 3 per litre), each 1 c.c. of which represents '008 gramme of bromine in excess of that which has reacted with the phenol, '094 gramme of which causes the disappearance of '480 gramme of free bromine, or as much as will be liberated by 10 c.c. of the sodium bromate solution. Instead of preparing a standard solution of 544 POISONING BY CAEBOLIC ACID. sodium bromate, it is preferable to compare the sample of carbolic acid to be tested with one of pure phenol. Calvert's No. 1 Carbolic Acid, previously boiled to get rid of traces of moisture, affords a very satisfactory standard. 1 The bromine-process, in one or other of its modifications, has superseded all the other methods of determining carbolic acid, except those based on direct measurement or weighing. A toxicological examination for carbolic acid is not un- frequently necessary, owing to the numerous instances in which poisoning has ensued from the accidental administration of the substance internally. In such cases, the mouth and oesophagus are commonly white, soft, and corroded, but are sometimes found hardened and shrivelled. The stomach is usually white, contracted, thickened, and shrivelled, but sometimes intensely congested, with destruction of the mucous membrane; occasionally no abnormal appearance is observable. The intestines are usually thickened and congested. The bladder is generally quite or very nearly empty, any urine having a dark colour. In testing animal matters for carbolic acid, the smell is a most valuable indication. For the recognition of the poison, the sus- pected matters are cut up and well shaken with Water acidulated with sulphuric acid. The liquid is then distilled, 2 and the tests for carbolic acid applied to the distillate. The tests of most service are the smell ; the reactions with ferric chloride, sodium hypochlorite, and bromine ; and the property of coagulating albumin. Carbolic acid may often be conveniently concentrated by shaking the fluid to be tested (e.g., urine) with dilute sulphuric acid and ether, separating the ethereal layer, and examining the residue of its evaporation by the tests for carbolic acid. Or, preferably, the urine, &c., may be distilled with dilute sulphuric acid, and the distillate shaken with ether. In cases of suspected poisoning by carbolic acid it must be remembered that phenols exist normally in minute quantity in urine, 1 Titration in carbon disulphide solution is not applicable to the assay of phenol, the proportion of bromine required being much less than corresponds to the formation of tribromophenol, an additive-compound being apparently formed. Titration by bromine in aqueous solution may be applied to a num- ber of phenoloid bodies with more or less success, but an extensive series of experiments made in the author's laboratory by J. C. Belcher gave very disap- pointing results in many cases, apparently from the occurrence of secondary reactions, such as the formation of q u i n o n e s, &c. 2 The operation should be continued as long as bromine water renders the distillate milky. COMMERCIAL CARBOLIC ACID. 545 and, along with its next homologues, is formed in small quantity in putrefaction. COMMERCIAL CARBOLIC ACID. Commercial carbolic acid often turns red in the light. The cause of the coloration is uncertain, the change having been attri- buted by different observers to the presence of copper, to contact with ammoniacal air, to the formation of rosolic acid, &c. The colouring matter can be separated by dissolving the carbolic acid in water and adding 5 per cent, of common salt to the solu- tion. The better varieties of commercial carbolic acid are well repre- sented by the articles manufactured by F. C. Calvert & Company. Their " No. 1 Carbolic Acid," in the form of colourless crystals, may be regarded as chemically pure and absolute, and free from homo- logous phenols, the proportion of which gradually increases in the lower grades till the dark liquid known as "JSTo. 5 Carbolic Acid" consists chiefly of cresylic acid, with smaller proportions of higher homologues. For disinfecting purposes, such an article appears to be fully as serviceable as pure carbolic acid. 1 In addition to containing water and homologous phenols, the lower grades of commercial carbolic acid are often largely adul- terated with neutral tar oils ("naphthalene oils") of little direct value as antiseptics. For the determination of the tar oils in crude carbolic acid the following simple method may be used: Introduce 10 c.c. of the sample into a graduated tube, and add gradually, noting the effect produced, twice its volume of a solution of caustic soda free from alumina, containing 9 per cent, of NaHO. Then close the tube and agitate well. The coal-tar acids will be completely dissolved by the alkaline liquid ; whilst, on standing, the neutral oils will form a separate stratum above or below the other, according as the admixture consisted of the light or heavy " oil of tar." By the volume occupied by the oily stratum the extent of the adulteration is at once indicated. "'After noticing whether the tar oils are light or heavy, a volume of petroleum spirit equal to that of the sample taken may be advantageously added. Its employment facilitates the separation of the oily stratum, and renders the reading of its volume more easy and accurate. Of course, the volume of petro- leum spirit used must be deducted from that of the total oily layer. When a more accurate determination of the neutral oils is required, and there is sufficient of the sample at disposal, the 1 According to C. M. Tidy, this statement does not extend to the lime com- pound of cresylic acid, which is said to be practically valueless as a disinfectant, whatever may be the value of the carbolic compound with lime. VOL. II. 2 M 546 ASSAY OF CARBOLIC ACID. modified process described in the section on " Creosote Oils " (page 559) may be used with advantage. The specific gravity of crude carbolic acid at the ordinary temperature should be between 1*050 and 1'065. If lighter, it is suspicious. In presence of light tar oil, the density is often as low as 1-040 or 1'045. For the estimation of the water in crude carbolic acid, Bach agitates the sample with half its volume of a saturated solution of common salt. The loss of volume undergone by the carbolic acid shows the measure of water present. If the experiment be made in a burette furnished with a glass tap, the saline solution may be run off and the phenolic layer agitated with soda as already de- scribed. The inferior grades of crude carbolic acid contain the smallest proportion of water. The following method of assaying crude carbolic acid with a view of ascertaining its quality, and the approximate proportion of crystallisable phenol contained in it, is due to Charles Lowe, and is largely employed by manufacturers: 1000 grains or 100 c.c. measure of the sample is placed in a retort (without any special condensing arrangement), and distilled, the liquid which passes over being collected in graduated tubes. Water first distils, and is followed by an oily fluid. When 10 per cent, by measure of the latter has been collected, the receiver is changed. The volume of water is then read off. If the oily liquid floats on the water, it contains light oil of tar. It should be heavier than water, in which case it may be regarded as hydrated acid containing about 50 per cent, of real carbolic acid. The next portion of the distillate con- sists of anhydrous acid, and when it measures 6 2 '5 per cent, the receiver is again changed. The residue in the retort consists wholly of cresylic acid and still higher homologues of carbolic acid. The 6 2 '5 per cent, of anhydrous acid contains variable proportions of carbolic and cresylic acid. These may be approximately deter- mined by ascertaining the solidifying point, which should be be- tween 60 and 75 F. (15'5 and 24 C.). Having ascertained this temperature, a mixture of pure carbolic and cresylic acids is made in such proportions as to have the same solidifying point. This must be adjusted by trial, or a series of standard specimens may be prepared. The exact point of solidification can be more sharply read if a minute fragment of crystallised carbolic acid be added to induce the commencement of the change of state ; or the sample may be solidified, and the liquefying point noted. Many qualities of crude carbolic acid now contain a compara- tively small proportion of light oils (5 to 6 per cent.), and hence a notable quantity of carbolic acid is lost in the 10 per cent, first CARBOLIC ACID POWDERS. 547 distilled. This raises the proportion of cresylic acid in the 6 2 '5 per cent, next collected, and hence a product is obtained having too low a solidifying point. A preferable plan of assaying the second and third qualities of carbolic acid would probably be to reject all that passes over below 185, then distil to 190 or 195, and take the measure and solidifying point of this fraction. For No. 1 quality, with 62 J per cent, of distillate crystallising above 70 F., only the portion passing over below 180 to 182 should be rejected. About 12 per cent, of water usually passes over from this kind of acid, though the proportion ranges from 10 to 17 per cent., and at times 1 per cent, of neutral oils are present. By stipulating that a sample should contain a certain proportion of anhydrous phenols (exclusive of neutral oils as estimated by soda) distilling below a given temperature and having a definite solidifying point, a more accurate knowledge of the product would be obtained. Or the quality of the sample might be simply expressed in units of anhydrous phenols solidifying at a certain fixed temperature. The mixtures of phenols from shale-tar and blast-furnace creosote are liable to be sold for crude carbolic acid. They may be dis- tinguished from the coal-tar product as described on page 571. CARBOLIC ACID DISINFECTING POWDERS. A variety of disinfecting powders are now made, which owe their efficacy chiefly to the fact of their containing more or less crude carbolic acid. In some cases the base of the powder is slaked lime, but the resultant u carbolate of lime " is of little value for antiseptic purposes. " MacdougalTs Disinfecting Powder," the oldest preparation of the kind, is made by adding a certain proportion of crude carbolic acid to a crude sulphite of calcium, prepared by passing sulphurous acid gas over ignited limestone. 1 Sulphurous acid is introduced into other powders by the direct addition of a solution of calcium bisulphite. " Calvert's Carbolic Acid Powder " is made by adding carbolic acid to the siliceous residue resulting from the manufacture of sulphate of aluminium from shale or kaolin. 1 Calcium sulphate is likewise a suitable absorbent, and kieselguhr has been used for the stronger powders. Macdougall Brothers have patented the use of soluble salts as ab- sorbents of carbolic acid, the resultant powder being more readily removed and less liable to choke up drain-pipes than the prepara- tions commonly employed. Good carbolic acid powders contain from 12 to 18 per cent. 2 of 1 For the analysis of the bases of Macdougall's and Calvert's carbolic powders, see a: paper by the writer in the Analyst, in. 286. 2 F. C. Calvert & Co. now manufacture disinfecting powders containing re- spectively 5, 10, 15, 20, and 50 per cent, of crude carbolic acid. 548 ASSAV OF CAKBOLIC POWDERS. crude carbolic acid, but they are liable to lose 1 or 2 per cent, by- volatilisation. Some powders in the market contain but 5 or 6 per cent, of total oils, of which less than half is really carbolic and cresylic acids, the remainder being neutral tar oils. The relative antiseptic values of different carbolic powders are sometimes tested by mixing 1 gramme of each sample with 20 grammes of flour. Add gradually to each mixture 200 c.c. of water, and stir well in the cold ; then bring the liquid to the boil, pour the resultant pastes into open vessels, and leave them freely exposed to the air. Note the number of days which elapses in each case before the formation of mildew occurs, and on which paste the growth takes place most easily and rapidly. L. Archbutt finds the flour-paste test very unsatisfactory, and suggests that it would be better to treat fresh urine or other putrescible liquid with the antiseptic, and examine daily for bacteria. For the determination of the percentage of crude acid contained in siliceous carbolic powders, a method frequently used is to introduce 1000 grains or 100 grammes of the powder into a tubulated glass or copper retort, and heat the vessel over a flame. Crude carbolic acid distils over, and may be collected in a gradu- ated tube. The process is continued as long as anything passes over. The heat should be pushed to dull redness, and the contents of the retort occasionally shaken towards the end of the process. On standing, the aqueous portion of the distillate separates from the oily liquid, and the volume of the latter may be read off. A combustion-tube of glass or iron, through which a slow current of coal gas is caused to pass, may be advantageously substituted for the retort. To diminish the loss due to solubility of the carbolic acid, the aqueous layer may be saturated with powdered sodium sulphate, when the dissolved carbolic acid will rise to the surface. When carefully conducted, the foregoing process has given in the writer's hand fairly satisfactory results, though test-experiments have indicated that the proportion of carbolic acid obtained is always somewhat below the truth. A better and more accurate process is the following, omitting the treatment with sulphuric acid as unnecessary in the case of siliceous powders. The quantity of the powder may also be increased to 100 grammes. In the case of powders made with lime, or others in which the carbolic acid exists in combination, the methods of distillation and direct treatment with a solvent do .not give accurate results. For the determination of the crude carbolic acid in such powders, the disinfectant value of which is very doubtful, the following method may be employed : 50 grammes of the sample should be mixed in a large mortar with 5 c.c. of water. Strong sulphuric acid, pre- ASSAY OF CARBOLIC POWDERS. 549 viously diluted with an equal bulk of water, is then added very gradually, a few drops only at a time. After each addition the whole is well mixed together with a pestle. The addition of the acid, which should extend over some hours, to avoid sensible rise of temperature, is continued until a minute fragment of the well- mixed contents of the mortar shows an acid reaction when placed on a piece of litmus paper and moistened with water. If the mixture be pasty, sufficient sand is mixed with it to cause it to granulate, and the mortar is then covered up and left for some hours. By proceeding in this manner the whole of the lime com- bines with the sulphuric acid and water to form gypsum, while the carbolic acid is liberated. The product is then exhausted with ether or gasolene in a Soxhlet-tube or similar contrivance, and the ethereal solution distilled till the contents of the retort acquire a temperature of about 110 C. 1 The residue consists of the crude carbolic acid extracted from the sample, and its weight may be ascertained, or it may be measured in a narrow graduated tube. Whether isolated by the extraction or the distillation process, the crude carbolic acid obtained should be further examined for neutral tar oils, which not unfrequently constitute the greater part of the so-called " carbolic acid " of disinfecting powders. For their detection and approximate determination, the test with dilute soda described on page 545 will usually be found sufficient. In other cases, the crude carbolic acid should be treated with twice its measure of strong soda solution (1*2 sp. gravity) any undissolved oils separated, and the alkaline solution shaken with ether to remove any neutral oils still remaining dissolved. The ethereal layer is separated, added to the neutral oils previously obtained, the ether driven off by a gentle heat, and the residual neutral oils or naphthalene measured or weighed. The alkaline solution of the phenols is boiled in a small flask to drive off the ether, and acidu- lated in a narrow graduated tube with diluted sulphuric acid (1:3). When the liquid has stood some time and is thoroughly cold, the layer of separated phenols is measured. Each cubic centimetre weighs about 1'050 gramme, hence an addition of ^ to the measure gives the correct weight. The results are somewhat below the truth, chiefly owing to the solubility of the phenols in aqueous liquids. The sulphurous acid contained in certain disinfecting powders 1 B. Nickels and C. M. Tidy use 90 per cent, benzol instead of ether for the extraction of the carbolic acid, which they effect by using a more dilute sul- phuric acid than is employed by the writer, and violently agitating the acidu- lated product with the solvent. 550 ISOMERIC CRESOLS. may be determined by stirring 1 gramme of the sample in a mortar with a small quantity of distilled water free from air, and decanting the liquid into a flask containing 50 c.c. of the ordinary decinormal solution of iodine and about 250 c.c. of water. The residue in the mortar is repeatedly treated with fresh quantities of water, the resultant liquids being transferred to the flask, and finally the undissolved powder is rinsed in. Very dilute hydrochloric acid is next cautiously added to the contents of the flask, until the reaction is distinctly acid, when the excess of iodine is determined by titration with decinormal thiosulphate in the usual way. Each c.c. of decinormal iodine reduced by the sulphite present represents 0-0032 gramme of S0 2 . CreSOlS. Cresylic AcidS. Cresylic Hydrates. Methyl- hydroxybenzenes. C 7 H 8 = C 7 H 7 .OH = C 6 H 4 (CH 3 ) H Three modifications of cresol are known (page 535), having the following characters : Variety. Melting Point ; C. Boiling Point ; C. Product when Fused with Caustic Potash. Ortho-cresol (1:2), Meta-cresol (1:3), 31 liquid 186 to 188 200 to 201 $ Salicylic acid (ortho- 1 hydroxybenzoic acid). SMeta-hydroxybenzoic acid. Para-cresol (1:4), . 36 198 to 199 JPara-hydroxybenzoic acid. Meta- and para-cresol yield a blue coloration with ferric chloride. Either modification of cresol can be obtained pure by dissolving the corresponding kind of toluidine and an equal weight of sulphuric acid in about 30 parts of hot water. An aqueous solution of potassium nitrite is then added in quantity sufficient for the reaction : C 7 H 7 .im 2 + KN0 2 + H 2 S0 4 = C 7 H 7 .OH + KHS0 4 + H 2 The liquid is then saturated with common salt or sodium sulphate, allowed to cool, and the layer of cresol separated and purified by distillation. All three modifications of cresol have been found in the cresylic acid from coal tar. The relative proportions in which they are usually present is uncertain, but para-cresol, with more or less of its isomers, constitutes the greater part of the crude liquid "carbolic acid " of commerce. COAL-TAR CRESOL. 551 CRESYLIC ACID FROM COAL TAR has a density of 1*039 to 1'044. It closely resembles carbolic acid, but is liquid, far less soluble in water, and boils at a higher temperature than the latter. The boiling point of commercial cresylic acid is very variable, as it con- tains more or less of carbolic acid and higher homologues. Samples of commercial carbolic acid containing much cresylic acid remain fluid at ordinary temperatures (even when anhydrous) and are less soluble in water and dilute alkaline liquids than is pure carbolic acid. 1 Cresylic acid resembles phenol in its reaction with ferric chloride, 2 and when acted on by strong nitric or sulphuric acid gives similar, but not identical, products with those yielded by carbolic acid. With excess of bromine it produces a similar body, but brominated cresol from coal-tar cresylic acid is liquid at ordinary temperatures, whereas the phenol derivative is solid. Carbolic Acid. Cresylic Acid. 1. Melting point, Solid at ordinary temperatures ; Liquid at ordinary temperatures ; liquefied by addition of water ; neither absolute nor hydrous both absolute and hydrated acid is solidified by freezing acid are solidified by freezing mixture. mixture. 2. Boiling point, 182 C. 198 to 203 C. 3. Solubility of hy- 1 volume in 11. 1 volume in 29. drous acid in cold water, 4. Solubility in strong Completely and readily soluble Soluble in equal volume of strong solution of am- in equal volume ; solution not ammonia ; the solution is pre- monia (sp. grav. 880) at 15 C., 5. Reaction with pe- precipitated by addition of less than 2 volumes of water. Absolute acid is miscible with hot cipitated by slight cooling or dilution. Absolute acid miscible in all pro- troleum spirit, petroleum spirit in all propor- tions. Miscible with only portions. No separation of crystals or liquid produced by volume of cold petroleum spirit; precipitated by greater propor- suddenly cooling solution in 3 measures of petroleum spirit. tion. With 3 volumes petro- leum spirit, bulk unchanged ; upper layer contains carbolic acid, which crystallises out on sudden cooling by freezing mixture. 6. Behaviour with gly- Miscible in all proportions. One Miscible in all proportions. One cerin of 1-258 sp. measure of carbolic acid with measure of cresylic acid, gravity at 15 C., an equal volume of glycerin is mixed with 1 measure of gly- not precipitated on addition of cerin, is completely precipi- 3 measures of water. In pre- tated by 1 measure of water. sence of cresylic acid less dilution is possible, 2 volumes of water being the maximum for a sample containing 25 per cent, cresylic acid. 1 Cresylic acid dissolves in dilute soda solution containing far less alkali than corresponds to the proportion C 7 H 8 : NaHO, but on adding water two layers are formed, the lower one of which closely resembles cresylic acid, but some- times occupies a considerably greater volume than that of the sample used. 2 With some samples of cresylic acid the blue coloration at first produced by ferric chloride rapidly changes to brown (compare page 569). 552 . CREOSOTE OILS. Cresylic acid is said to possess antiseptic properties in even a greater degree than carbolic acid. It may be determined by the methods employed for carbolic acid (page 548). The table on the preceding page shows the chief differences of analytical value existing between carbolic and cresylic acids. The statements have been personally verified by the author upon a sample of Cal vert's " No. 1 Carbolic Acid " and a cresylic acid prepared purposely by careful fractional distillation of a sample of Calvert's "No. 5 Carbolic Acid." l From these reactions it will be seen that cresylic acid is less soluble in water, ammonia, and glycerin, than is the case with carbolic acid, but it is more soluble in petroleum spirit. Although the above tests suffice for the detection of considerable proportions of cresylic acid in admixture with carbolic acid, they afford no basis for its quantitative determination, except of the roughest kind. The only available means of even approximately determining the proportion of cresylic acid present in samples of crude carbolic acid is that described on page 546. Creosote Oils. The term " creosote-oil " was formerly used to denote that por- tion of the distillate from coal tar intermediate between " crude naphtha" and pitch. It is practically synonymous with the " heavy oil " or " dead oil," so called from its being heavier than water. The name "creosote oil" is now sometimes applied to certain oils obtained by the distillation of bituminous shale, and by the cool- ing of the waste gases from blast-furnaces, and also to the bone-oil produced in the manufacture of animal charcoal. All these products are decidedly different in their chemical and physical characters from the coal-tar products to which the name of creosote oil was first applied (see page 571). Creosote oils receive their main application in the creosoting or preserving of timber, 2 and their technical assay is practically 1 The cresylic acid was further purified by dissolving it in caustic soda and agitating the solution with ether to remove naphthalene and other hydrocar- bons, the cresol being subsequently recovered by addition of acid. If this treatment be omitted, scales of naphthalene, &c., are liable to separate on treating the sample with ammonia. 2 The process of creosoting is effected by placing well-seasoned timber in a vessel so constructed that a more or less perfect vacuum can be obtained by means of an air-pump. The creosote oil, previously heated to a temperature of 35 to 50 C. , is allowed to enter the exhausted receiver, and pressure is then applied by pumps in order to effect the better penetration of the antiseptic fluid. According to an improved method invented by S. B. Boulton, the CREOSOTING limited to an examination of their suitability for -ffi^purpose. 1 The impregnation of wood with creosote oil chokes up the pores and materially hinders the subsequent absorption of water. The smell of creosote oil is one much disliked by the lower animals, while certain of the constituents have a powerful antiseptic action. The " tar-acids," or phenoloid constituents, were, till recently, commonly considered to be those to which the preservative properties of creosote oil were mainly due, as they are powerful anti- septics, coagulating albumin and rendering animal life impossible. It is probable, however, that the value of tar-acids, as constituents of creosote intended for preserving timber, has been greatly over- rated, as the solubility and volatility of the lower members of the series prevent their antiseptic influence from being permanent. 2 exhaustion is continued after the entrance of the creosote, which is heated to a temperature somewhat above 100 C. By this means the moisture contained in the pores of the wood is volatilised and removed by the pump, and the creosote oil subsequently penetrates the wood very thoroughly. A great advantage of this process is that wet timber can be at once treated without being previously seasoned. The amount of creosote oil taken up by the timber varies considerably, but is usually about one gallon per cubic foot of wood. 1 Creosote oils have also been employed as fuel, for production of illuminat- ing gas, carbonising coal gas, softening hard pitch, manufacturing lubricating compounds, burning for lamp-black, production of antiseptic preparations, &c. It has been recently proposed to project a spray of creosote oil, by means of compressed air, by which a circular brush of flame of great illuminating power is said to be obtainable, well adapted for out-door use. 2 S. B. B o u 1 1 o n has published the following data : Two typical speci- mens of coal-tar creosote oils were repeatedly washed by agitation with three times their measure of cold water, and the tar-acids determined after the seventeenth and thirty-second treatments : Tar-Acids ; per cent. MiX Countr d Oii and Country Oil. Original oil, 10 17 '5 After 17 washings, . 3'5 6'0 After 32 washings, . 1*5 3 '5 The small proportion of tar-acids remaining in both cases gave no reaction with the ammonia-bromine test for carbolic acid, and did not boil below 215 C. The distillate below 315 C. yielded by the washed oil was somewhat less than that given by the original. Experiments made by Coisne, on behalf of the Belgian Government, on sleepers which had been many years in use, showed that the tar-acids had disappeared. Experiments made on the preservation of wood-shavings by creosote oils respectively supplemented by the addition of tar-acids and high- boiling oils gave results notably favourable to the latter. In 1882, S. B. Boulton made a series of experiments on sleepers, obtained from various rail- ways, which had resisted decay for periods varying from 16 to 32 years. He 554 COAL-TAR CREOSOTE OIL. Hence the phenoloid bodies of high boiling point and slight solubility are probably of more value for creosoting timber than carbolic and cresylic acids themselves. But the lower phenols are doubtless valuable as coagulators of albumin, and should be present in creosote oils in sufficient quantity to effect this. If dissolved or volatilised from the timber they will prob- ably create an antiseptic atmosphere, and thus prevent the approach of living organisms. The basic constituents are also probably of high antiseptic value, and certain of them are not readily washed out or volatilised. The naphthalene of coal-tar creosote also volatilises only from the superficial strata of the timber, and, by solidifying and filling up the pores of the wood, doubtless acts mechanically as a valuable preservative agent. 1 COAL-TAR CREOSOTE OIL commonly consists of that portion of coal tar which distils between 200 and 300 C., together with the residual oils from the manufacture of crude carbolic acid, naphthal- ene, and anthracene (see page 509). 2 When fresh, coal-tar creosote oil is greenish-yellow and highly fluorescent, the latter character being still more evident after exposure of the oil to air and light. After a time the oil becomes bottle-green by reflected and dark red by transmitted light. The smell is unpleasant and highly characteristic. When rubbed be- tween the fingers, the feel is at first oily, but the tar-acids soon act on the skin, producing a sensation of friction. Creosote oil from coal tar is always somewhat heavier than water, the specific gravity of the portions last distilling being as high as I'lO. Coal-tar creosote oil usually contains more or less naphthalene, phenanthrene, anthracene, diphenyl, and other solid hydro- carbons; carbolic and cresylic acids, and higher phenoloid found that the tar-acids had disappeared, that the semi-solid constituents, such as naphthalene, were present, and that from 60 to 75 per cent, of the oils remaining in the wood distilled above 315 C. ( = 600 F.). In 1869 R. Angus Smith pointed out the volatility and solubility of carbolic and cresylic acids as an obstacle to their use as permanent germicides. The same facts have been dwelt on by A. Sansom, and have recently been demonstrated with great clearness by Koch, Boillat, and others. 1 Much valuable information on the nature and mode of action of creosote oils will be found in an exhaustive paper by S. B. Boulton in the Proceedings of the Institute of Civil Engineers for May, 1884, a copious abstract from which has been published in the Jour. Soc. Chemical Industry, iii. 622. 2 This description applies more especially to the creosote oil produced in the best managed works. In others, every residue which cannot be used for any other purpose finds its way into the creosote- oil well. GOAL-TAR CEEOSOTE OIL. 555 bodies; 1 about 2 per cent, of pyridine, cryptidine. quinoline, acridine, and other bodies of basic character; and the so-called indifferent oils, fluid at ordinary temperatures, and about which comparatively little is known, notwithstanding the enormous quantities of creosote oil which are produced (see " Naphthalene Oils," page 509). The following table shows the general character of coal-tar creosote oils of different kinds. The samples under A were the wliole runnings of heavy oils distilled from samples of tar obtained from twenty different metropolitan gas-works. The samples under B were produced at the works of the Gaslight and Coke Company at Beckton, and represent creosote oils from which portions of the green oils and naphthalene were excluded. Hence these samples are comparatively rich in tar-acids, and give a larger distillate below 600 F. than the whole runnings described under A. 2 The liquefying point of the B samples ranged from 98 to 91 F., and the point of turbidity on cooling from 88 to 83. The samples in series C were analysed by L. Archbutt. All were completely fluid at 90 F., and many at 60. The sample yielding 72 per per cent, of distillate and 13*5 of tar-acids was the product of a special treatment. The samples in series C are probably somewhat richer in tar-acids than the generality of country oils : Sp. Gravity Percentage of Distillate Percentage of Tar- Acids at 90F. (=32 C.). below 600 F. (=315C.). from Distillate. A. Whole runnings of heavy London oils Highest, . . . 1075 79 8-0 Lowest, ..... 1048 60 3-0 Average of 20 samples, 1058-8 71-5 5-6 B. Partial runnings of London oils Highest, 91 10-2 Lowest, 78 8-2 Average of 20 samples, ... 82-8 9-15 C. English country oils Highest, ..... 1056 90 24-0 Lowest, 1024 72 13-5 Average of 18 samples, 1033-5 81-8 18-6 The dead oils made in London and from the tar from Newcastle 1 Besides higher homologues of phenol, and a- and 0-naphthol, Noetling believes the less volatile phenoloid bodies of creosote oil to consist in part of phenols of anthracene and phenanthrene (Ber., xvii. 385). 2 Writing in February 1885, C. M. Tidy, who analysed the B samples, states that the best London creosote oils contain a proportion of tar-acids closely approximating to 8 per cent., and he stipulates for this amount, believ- ing it to secure the genuine character of the oil. 556 ASSAY OF CEEOSOTE OILS. coal generally are the richest in naphthalene and constituents of high boiling point, but contain but a moderate percentage of tar-acids. The " country oils," or oils from the Midland districts, are lighter, thinner, and more volatile than "London oils," and usually contain less naphthalene and a larger proportion of tar- acids than the latter. The Scotch oils, again, are largely derived from cannel coal, and are still thinner and more volatile, and some- times lighter than water. ASSAY OF CREOSOTE OILS. As previously stated (page 553), the value of creosote oils for preserving timber depends on several constituents, all of which should therefore be taken into account in the examination. Un- fortunately the assay of creosote oils is often conducted according to the arbitrary conditions of a contract-note drawn up without much reference to the chemical nature of the article to be assayed, or to the possibility of obtaining a fairly accurate determination of the leading constituents by the mode of operation prescribed. Until recently, specifications for coal-tar creosote oil often stipu- lated for a certain density ; the absence of a deposit when cold ; the presence of a certain proportion of tar-acids ; the volatility of a certain percentage below 315 C. ( = 600 F.); and occasionally stipulations of a still more arbitrary character were made. Some recent specifications include no reference to the density, allow the presence of a considerable proportion of naphthalene, and stipulate that a certain percentage of the oil shall not distil below a given temperature, instead of the opposite, this modification being a recognition of the value of the fractions of high boiling point. 1 1 In a Eeport to the Directors of the Gas Light and Coke Company (February 1885), C. M. Tidy remarks that "the heavier oils are un- doubtedly the most preservative, and a wood well-saturated with such oils is practically indestructible. It is better to have 5 per cent, only of mixed tar acids, provided the oil has a high boiling point, than 15 per cent, of tar- acids in an oil which distils at a low temperature. For the oil with the high boiling point, amongst other advantages, contains the less volatile alkaloids, such as cryptidine and acridine. The higher the distilling the more permanent in all probability will be the effects of the oils, owing to their lesser volatility." He then recommends the following specification for coal-tar creosote oil: 1. That the creosote shall be completely liquid at a temperature of 100 F. , no deposit afterwards taking place until the oil registers a temperature of 95 F. 2. That the creosote shall contain at least 25 per cent, of constituents that do not distil over at a temperature of 600 F. 3. That, tested by the process here- after to be described, the creosote shall yield a total of 8 per cent, of tar-acids. 4. That it shall contain no admixture of bone oil, shale oil, or any substance not obtained from the distillation of coal tar, and that the first 25 per cent, of the distillate shall have a specific gravity greater than that of water. This CREOSOTE OIL SPECIFICATIONS. 557 No practical recognition has yet been made of the antiseptic value of the basic constituents of creosote oil, nor of the fact that the portion of the oil distilling below 315 C. does not contain the whole of the tar-acids. The density of creosote oil is in no way a criterion of its suita- bility for creosoting timber, but it is of value as an indication of the genuine character of the sample. The density of creosote oil containing much naphthalene may be ascertained as described in the footnote on page 133. The presence of solid naphthalene in the cold creosote oil is no detriment, but the deposit should wholly dissolve on warming. A sample should become quite clear below 38 C. (= 100 F.), and should not become turbid again till cooled to 32 C. ( = 90 F.). The liquefying point is ascertained simply by trans- ferring an average sample of the creosote oil to a test-tube, immers- specification has been to some extent adopted by several of the large railway companies. In the specification of the Crown Agents for the Colonies (July 1882), it is stipulated that "the creosote shall not contain more than 30 per cent, of naphthalene, para-naphthalene, or any other (solid) substance when subjected to a temperature of 40 F." The same specification stipulates for a density of 1 '035 to 1 '055 at a temperature of 60 F. ; for a distillate of at least 75 per cent, below 610 F., containing at least 10 per cent, of tar-acids (extracted by soda of 1 '125 specific gravity), of which one half should distil below 450 F. The specifications of the Belgian Government do not stipulate for any tar-acids, but require that at least two-thirds of the creosote shall distil at a temperature exceeding 250 C., and that nothing shall distil below 200. It allows 30 per cent, of naphthalene determined at the ordinary temperature. The recent specification of the Midland Railway Company con- tains the following stipulations : The creosoting liquor is to be of the de- scription known as Heavy Oil of Tar, obtained by the distillation of coal-tar, and consisting of that portion of the distillate which comes over between the temperature of about 350 F. and that of about 760 F. It must be free from any oil or other substance not obtainable from such distillate, and must con- tain at least 25 per cent, of constituents distilling above 600 F. It must become perfectly fluid at 100 F., and remain so on recooling to 90 F. The specific gravity at 90 F. must lie between 1 '040 and 1 '065, as compared with water at 60 F. The liquor must yield not less than 6 per cent, of tar-acids when the distillate below 600 F. is treated with soda solution of 1 '21 specific gravity. Sir Frederick Abel now recommends a specification in which the distillate below 600 F. is not to exceed 80 or fall short of 70 per cent, and the tar-acids in the distillate must not be less than 9 per cent, of the original creosote oil. The specific gravity must range between 1 P 035 and 1 '065. In other respects the provisions are identical with those in the Midland Railway specification. 558 ASSAY OF CREOSOTE OILS. ing a thermometer, and warming it gently till it becomes liquid. The point of turbidity is similarly observed by allowing the tube to cool spontaneously. These simple tests are much more satisfactory than the assay for solid naphthalene, as required by the Crown Agents for the Colonies. If necessary, the approximate determination of the constituent may be effected in the manner carried out in the works-laboratory of Messrs Burt, Boulton, & Haywood, as follows : " 100 grammes of the sample are placed in a small beaker and cooled in a freezing mixture to 40 F. ( = 4'5 C.). The oil is kept at that tempera- ture for about fifteen minutes, after which it is thrown on a cloth filter, placed in a small funnel inserted in a larger one containing a freezing mixture, so that a temperature of 40 F. may be main- tained during the filtration. The filter-cloth and contents are then removed from the small funnel as quickly as possible, and pressed strongly between coarse filter-paper in a copying press or vice. The pressed product is then detached from the cloth and weighed." The following method is that usually adopted for ascertaining the behaviour of creosote oil on distillation : a 100 c.c. measure of the oil is gradually heated in a 4 oz. tubulated retort, by a small naked flame surrounded by a tin-plate cylinder. A thermometer should be arranged in the retort in such a position that on the termination of the distillation the bulb shall only just touch the residual liquid. The flame is arranged so that the distillation shall occupy about 30 minutes. The distillate should be collected in a graduated glass cylinder, and the proportion of water observed at an early stage of the operation, as later on it is again more or less completely taken up by the phenoloid constituents of the oil. The proportion of water in creosote oils is very variable, ranging from 1 or 2 to nearly 10 per cent. The distillation is arrested at 315 C. ( = 600 0> F.), 321 C. ( = 610 F.), or other temperature, as specified in the contract-note, the measure of the distillate being then observed. For the determination of the tar-acids, it is usual to employ the distillate obtained in the last operation. This is transferred to a stoppered flask, holding about 250 G.C., and treated with 30 c.c. of solution of caustic soda of 1*21 specific gravity. 2 The liquid is 1 The method described in the text is that employed in the works-laboratory of Messrs Burt, Boulton, & Haywood. For the details of this and the following test, as also for much other information on creosote oils and other tar-products, the writer is indebted to Mr D. Bendix. 2 Prepared by dissolving 23 grammes of pure caustic soda in water, and diluting to 100 c.c. DETERMINATION OF TAR-ACIDS. 559 thoroughly agitated, heated for a few minutes in a water-bath, and again thoroughly agitated for about a minute. The whole is then poured into a separating funnel, the alkaline liquid drawn off, and the oil agitated with a further quantity of 15 c.c. of soda solution, which is then separated as before, 1 after which the alkaline liquids are mixed, well cooled, separated from any further stratum of oil, and treated with a slight excess of dilute sulphuric acid (1 measure of the concentrated acid to 3 of water), of which about 30 c.c. will be required. The mixture is then transferred to a graduated cylinder and allowed to cool completely, after which the volume of tar-acids is observed, the number of c.c. obtained being the per- centage by measure of tar-acids in the sample under examina- tion. 2 The foregoing mode of operation ignores such tar-acids as occur in the fraction of the oil distilling above 315 to 320 C., 3 and does not ensure the complete extraction of the acids existing in the less volatile portion of the oil. A more accurate and practical assay of creosote oil for the content of tar-acids would be effected by adopting the following modifications of the process : The oil should be distilled to the point of pitching, and the whole of the distillate subjected to the treatment with solution of soda. The alkali should at first be of moderate strength (e.g., 1*125), but the 1 In order to ascertain if the extraction of the phenols is complete, it is necessary to agitate the undissolved with alkali a third time, and acidify the liquid separately. Complete extraction is generally indicated by the soda ceasing to acquire a reddish colour. 2 The method described in the text is substantially that prescribed by Abel and Tidy. In the specification of the Crown Agents for the Colonies the specific gravity of the caustic soda employed is 1 *125, but otherwise the process is the same. Tidy employs 20 c.c. of caustic soda for the second and third extractions, instead of 15 c.c. as prescribed in the text. Having separated the tar-acids, he redissolves them in 20 c.c. of the caustic soda solution (sp. gr. 1*20) and 10 c.c. of water. The solution is then boiled and filtered through a funnel containing a plug of asbestos. The plug is washed with not more than 5 c.c. of boiling water, and the filtrate allowed to cool perfectly in a 100 c.c. measure. It is then rendered slightly acid with dilute sulphuric acid, of which about 10 c.c. will be required, allowed to stand for two hours till perfectly cold, when the percentage of tar-acids is read off. The results are lower than those given by processes in which the re-solution of the tar-acids is omitted, owing to their imperfect recovery from the aqueous liquid. Abel formerly recommended a fractional distillation of the tar-acids obtained, at least one half of which he considered should pass over below 233 C., but of late he has abandoned this stipulation. 8 The proportion of these higher phenoloi'd bodies extractable by strong caustic soda from London coal-tar creosote varies from 2 to fully 4 per cent. 560 DETERMINATION OF TAR BASES. operation should be repeated with fresh quantities of soda solution of 1'34 specific gravity, until the extraction is complete, as shown by the separation of mere traces of tar-acids on acidifying the alkaline liquid. To cause the alkaline liquid to separate com- pletely and promptly from the stratum of indifferent oils, an addition of petroleum spirit should be made and the whole again agitated. The petroleum spirit acts as a solvent for the oils, and also prevents the naphthalene from solidifying or being partly dis- solved by the alkaline liquid. Instead of liberating and mea- suring the tar-acids in a graduated cylinder, a more accurate plan is to employ a flask with, a narrow graduated neck. The layer of tar-acids is brought to the zero-mark by running in mercury from a burette. It must be borne in mind that the tar-acids separated are not anhydrous. If desired, they can be further examined as described in the section treating of the assay of crude carbolic acid. Abel till recently stipulated that fully 50 per cent, of the separated tar- acids should distil below 232 C. ( = 450 F.), but there is no apparent ground for assuming that the phenoloid bodies of lower boiling point are superior as antiseptic agents to those distilling at a higher temperature. The foregoing modified method of estimating the tar-acids in creosote oils by isolation and measurement is far more satisfactory than any process based on their conversion into the bromo-deriva- tives, as the latter plan involves the knowledge or assumption of their mean molecular weight and of their exact reaction with bromine. Although not usually practised, a valuable addition to the ordi- nary method of examining creosote oils consists in a determination of the basic constituents. This may be effected by distilling the sample to the point of coking and agitating the distillate with a mixture of 1 volume of sulphuric acid with 3 of water. The acid liquid is separated, rendered distinctly alkaline with soda, any oily layer separated, and the aqueous liquid distilled nearly to dryness. This second distillate is mixed with the oily layer, the whole acidulated with hydrochloric acid, and evaporated to dryness on the water-bath. The residue consists of the hydrochlorides of the tar-bases, from which the bases themselves may be liberated by solution in a small quantity of water and addition of solid caustic soda to the liquid. If desired, the bases may be further examined by converting them into chloroplatinates. DIHYDBIC PHENOLS. C n H 2n _ 8 : (OH) 2 . The dihydric phenols bear the same relation to carbolic acid and its homologues that g 1 y c o 1, C 2 H 4 : (OH) 2 , bears to ordinary ISOMERIC DIHYDKOXYBENZENES. 561 alcohol, C 2 H 5 .OH. The following members of the series are known : f(l:2) Ortho-dihydroxybenzene, catechol, or pyro- catechin. (1:3) Meta-dihydroxybenzene, resorcinol, or res- orcin. (1:4) Para-dihydroxy benzene, quinol, or hydro- quinone. TT /PTT \ /rm\ 1 :2 Homocatechol. 6 H 3 (CH 3 ):< EL) 2 . C 6 H 4 :(OH) S C 6 H 2 (CH 3 ) 2 :(OH) 2 j Hydiophloione ( Betorcmol, or p-orcm. The three dihydroxy benzenes, catechol, resorcinol, and quinol, may be obtained by fusing the corresponding iodo- or chloro-phenols, phenol-sul phonic acids, or benzeiie-disulphonic acids with caustic potash. The following equations represent the reactions : C 6 H 4 I(OH) + K(OH) = C 6 H 4 (OH) 2 + KI C 6 H 4 (OH)S0 3 K + K(OH) = C 6 H 4 (OH) 2 + K 2 S0 3 , C 6 H 4 (S0 3 K) 2 + 2K(OH) = C 6 H 4 (OH) 2 + 2K 2 S0 3 . If the temperature be high, resorcinol is always obtained, as it is more stable than its isomers. The three dihydroxybenzenes are volatile crystallisable bodies, readily soluble in water, alcohol, and ether, and extracted from their aqueous solutions by agitation with ether. They form ethers when their hydrogen is displaced by alcohol-radicals, and resemble glycols in many respects. The table on the following page shows the chief distinctions between them ; but, besides the reactions in the table, resorcinol is char- acterised by its behaviour with nitric acid, bromine, bleaching powder, and phthalic anhydride (see page 563). Resorcinol. ReSOrcin. Meta-dihydroxybenzene. C 6 H e2 C 6 H 4 : (OH) 2 = C 6 H 4 Resorcin was originally obtained by the action of fused alkalies on certain resins, and subsequently by their action on meta-iodo-phenol, but it is now manufactured on a large scale by heating caustic soda to about 250 C. with sodium meta-benzene-disulphonate (see above). The fused mass is allowed to cool, dissolved in water, and the solu- tion acidified. From the solution, the resorcinol can be extracted by agitation with ether, and can be purified by sublimation or crystallisation from ether or hot benzene. Kesorcinol crystallises in trimetric tables from water, alcohol, VOL. II. 2 N 562 CHAEACTERS OF DIHYDROXYBENZENES. SJ-Scfs^ 3 ta ^e i^^ _8 . CO _ 2 "3 to " "* jj 1 I? od, ; s^f- 3 ^ III Msi S >> - tD !i . |I IMS IJi jfK S 93 s|s oi| isilll ,2 C T3 a "S | n ii 111 Trimetric So-l Pill AH ^ jifil and col Turns bro Dark viol No precip IS o >' ^ Swectisli. .. ^ ^- : - V no o s .-.^ a S .2 "2 rt ^ ^ ^ o> c o -* o 3 c3 >> ^ a 2 rrr "* ** ^ ^ ^* C- o ^j 03 ^ ^'^ y 0; C ~ a .S .> g"S "oX ''i s^ Is 1 5 , I? 1 | gi w go ^ J| ll s lii. 1 +3 jl Q n of phenol or tho- D, benzoin, or guaii stic alkalies. Dry protocatec h.u i I 3 (OH>,.COOH. Acti ' on g u'ai a c o 1,C 6 H 4 square prisms or ;es resembling benzoi at 104; boils at 245 limed, forming pun, ch excite coughing. soluble in water, a 2r ; extracted by < ecus solutions. ties green, brown, am green, changed to v nonia or acid sodium much altered by t ored to green by acid s precipitate. 1 "c c .2 o ~ 3 >S '|3 0*0 cJS I* ill! < B ||| S |1 1 fa i. & > B ^ ^ a 5 5 o i . ^ * 8 "1 * P c c 2 -Cf 4* o o