I.—Hydrocarbons.
1. PETROLEUM.
§ 137. Petroleum is a general term for a mixture of hydrocarbons of the paraffin series, which are found naturally in certain parts of the world, and are in commerce under liquid and solid forms of various density. Crude petroleum is not imported into England, the original substance having previously undergone more or less rectification. The lighter and more volatile portions are known under the name of cymogene, rhigolene, gasolene, and naphtha.
§ 138. Cymogene has a specific gravity of ·590, and boils at 0°. It has been employed in refrigerating machines. It appears to consist chiefly of butane (C4H10).
§ 139. Rhigolene is now used in medicine in the form of spray to produce local anæsthesia. It boils at 18°, and has a density of ·650.
§ 140. Gasolene has a density of ·680-·688; it has received technical applications in the “naphthalising” of air and gas.
§ 141. Benzoline (mineral naphtha, petroleum naphtha, petroleum spirit, petroleum ether) is a mixture of the lighter series of hydro-carbons; the greater part consists of heptane, and there is also a considerable quantity of pentane (C7H16) present. The specific gravity varies from ·69 to ·74. It is very inflammable, and is used in sponge lamps, and also as a solvent for gutta-percha, naphthalene, paraffin, wax, and many other bodies. By the practical chemist it is much employed.
The similarity of the terms benzoline and benzene has caused benzoline to be often confused with benzol or benzene, the leading constituent of coal-tar naphtha (C6H6). Mr Allen[132] gives in the following table a summary of the chief points of distinction, both between petroleum naphtha, shale naphtha, and coal-tar naphtha. The table is founded upon the examination of particular samples, and commercial samples may present a few minor deviations.
[132] Commercial Organic Analysis, vol. ii. p. 31.
TABLE OF THE VARIETIES OF NAPHTHA.
| Petroleum Naphtha. | Shale Naphtha. | Coal-tar Naphtha. |
|---|---|---|
| Contains at least 75 per cent. of heptane, C7H16, and other hydrocarbons of the marsh gas or paraffin series; the remainder apparently olefins, CnH2n, with distinct traces of benzene and its homologues. | Contains at least 60 to 70 per cent. of heptylene, C7H14, and other hydrocarbons of the olefin series; the remainder paraffins. No trace of benzene or its homologues. | Consists almost wholly of benzene, C6H6, and other homologous hydrocarbons, with a small percentage of light hydrocarbons in some samples. |
| Specific gravity at 15°, ·600. | Specific gravity at 15°, ·718. | Specific gravity ·876. |
| Distils between 65° and 100°. | Distils between 65° and 100°. | Distils between 80° and 120°. |
| Dissolves coal-tar pitch, but slightly; liquid, but little coloured even after prolonged contact. | Behaves similarly to petroleum naphtha with regard to the solution of pitch. | Readily dissolves pitch, forming a deep brown solution. |
| On shaking three measures of the sample with one measure of fused crystals of absolute carbolic acid, no solution. Liquids not miscible. | When treated with fused carbolic acid crystals, the liquids mix perfectly. | The liquids form a homogeneous mixture when treated with fused carbolic acid crystals. |
| Combines with 10 per cent. of its weight of bromine in the cold. | Combines with upwards of 90 per cent. of its weight of bromine. | Combines slowly with 30-40 per cent. of its weight of bromine. |
§ 142. Paraffin Oil (or kerosine, mineral oil, photogen, &c.) is the chief product resulting from the distillation of American petroleum—the usual specific gravity is about ·802—it is a mixture of hydrocarbons of the paraffin series. It should be free from the more volatile constituents, and hence should not take fire when a flame is applied near the surface of the cold liquid.
§ 143. Effects of Petroleum.—Since we have here to deal with a commercial substance of such different degrees of purity, and various samples of which are composed of such various proportions of different hydrocarbons, its action can only be stated in very general terms. Eulenberg[133] has experimented with the lighter products obtained from the distillation of Canadian petroleum. This contained sulphur products, and was extremely poisonous, the vapour killing a rabbit in a short time, with previous insensibility and convulsions. The autopsy showed a thin extravasation of blood on the surface of each of the bulbi, much coagulated blood in the heart, congested lungs, and a bloody mucus covering the tracheal mucous membrane. An experiment made on a cat with the lighter petroleum (which had no excess of sulphur) in the state of vapour, showed that it was an anæsthetic, the anæsthesia being accompanied by convulsions, which towards the end were tetanic and violent. The evaporation of 1·5 grm. in a close chamber killed the animal in three hours. The lungs were found congested, but little else was remarkable. Much petroleum vapour is breathed in certain factories, especially those in which petroleum is refined.[134] From this cause there have been rather frequent toxic symptoms among the workmen. Eulenberg[135] describes the symptoms as follows:—A person, after breathing an overdose of the vapour, becomes very pale, the lips are livid, the respiration slow, the heart’s action weak and scarcely to be felt. If he does not immediately go into the open air away from the poisonous vapour, these symptoms may pass on to insensibility, convulsions, and death. It often occasions a condition of the voluntary muscles similar to that induced by drunkenness, and on recovery the patient is troubled by singing in the ears and noises in the head. The smell and taste of the poison may remain for a long time.
[133] Gewerbe-Hygiene.
[134] The vapour most likely to rise at the ordinary temperature, and mix with the atmosphere, is that of the lighter series, from cymogene to benzoline.
[135] Op. cit.
§ 144. Poisoning by taking light petroleum into the stomach is not common. In a case recorded by Taylor,[136] a woman, for the purpose of suicide, swallowed a pint of petroleum, There followed a slight pain in the stomach, and a little febrile disturbance, and a powerful smell of petroleum remained about the body for six days; but she completely recovered. In August 1870 a sea-captain drank a quantity of paraffin, that is, lighting petroleum, and died in a few hours in an unconscious state. A child, 2 years old, was brought to King’s College Hospital within ten minutes after taking a teaspoonful of paraffin. It was semi-comatose and pale, with contracted pupils; there was no vomiting or purging. Emetics of sulphate of zinc were administered, and the child recovered in twenty-four hours. In another case treated at the same hospital, a child had swallowed an unknown quantity of paraffin. It fell into a comatose state, which simulated tubercular meningitis, and lasted for nearly three weeks.[137] In a case recorded by Mr Robert Smith,[138] a child, 4 years of age, had swallowed an unknown quantity of paraffin. A few minutes afterwards, the symptoms commenced; they were those of suffocation, with a constant cough; there was no expectoration; the tongue, gums, and cheeks were blanched and swollen where the fluid touched them; recovery followed. A woman, aged 32, who had taken a quarter of a pint of paraffin, was found unconscious and very cold; the stomach-pump was used, and she recovered.[139] Hence it is tolerably certain, from the above instances, that should a case of petroleum poisoning occur, the expert will not have to deal with infinitesimal quantities; but while the odour of the oil will probably be distinctly perceptible, there will be also a sufficient amount obtained either from matters vomited, or the contents of the stomach, &c., so that no difficulty will be experienced in identifying it.
[136] Poisons, p. 656
[137] Brit. Med. Journ., Sept. 16, 1876, p. 365.
[138] Brit. Med. Journ., Oct. 14, 1876.
[139] Pharm. Journ., Feb. 12, 1875; also for other cases see Brit. Med. Journ., Nov. 4, 1876; and Köhler’s Physiol. Therap., p. 437.
§ 145. In order to separate petroleum from any liquid, the substances under examination must be carefully distilled in the manner recommended under “[Ether].” The lighter petroleums will distil by the aid of a water-bath; but the heavier require a stronger heat; redistillation of the distillate may be necessary. The odour of the liquid, its inflammable character, and its other properties, will be sufficient for identification.
2. COAL-TAR-NAPHTHA—BENZENE.
§ 146. Coal-tar-naphtha in its crude state, is an extremely complex liquid, of a most disagreeable smell. Much benzene (C6H6) is present with higher homologues of the benzene series. Toluene (C7H8), naphthalene (C10H8), hydrocarbons of the paraffin series, especially hexane (C6H14), and hydrocarbons of the olefin series, especially pentylene, hexylene, and heptylene (C5H10, C6H12 and C7H14). Besides these, there are nitrogenised bases, such as aniline, picoline, and pyridine; phenols, especially carbolic acid; ammonia, ammonium sulphide, carbon disulphide, and probably other sulphur compounds; acetylene and aceto-nitrile. By distillation and fractional distillation are produced what are technically known “once run” naphtha, 90 per cent. benzol, 50 and 90 per cent. benzol,[140] 30 per cent. benzol, solvent naphtha, and residue known as “last runnings.”
[140] Or 50⁄90 benzol, this indicates that 50 per cent. distils over below 100°; and 40, making in all 90, below 120°.
§ 147. Taylor[141] records a case in which a boy, aged 12, swallowed about 3 ozs. of naphtha, the kind usually sold for burning in lamps, and died with symptoms of narcotic poisoning. The child, after taking it, ran about in wild delirium, he then sank into a state of collapse, breathing stertorously, and the skin became cold and clammy. On vomiting being excited, he rejected about two tablespoonfuls of the naphtha, and recovered somewhat, but again fell into collapse with great muscular relaxation. The breathing was difficult; there were no convulsions; the eyes were fixed and glassy, the pupils contracted; there was frothing at the mouth. In spite of every effort to save him, he died in less than three hours after taking the poison. The body, examined three days after death, smelt strongly of naphtha, but the post-mortem appearances were in no way peculiar, save that the stomach contained a pint of semi-fluid matter, from which a fluid, having the characteristics of impure benzene, was separated.
[141] Op. cit., p. 657.
§ 148. The effects of the vapour of benzene have been studied by Eulenberg in experiments on cats and rabbits, and there are also available observations on men[142] who have been accidentally exposed to its influence. From these sources of information, it is evident that the vapour of benzene has a distinctly narcotic effect, while influencing also in a marked degree the spinal cord. There are, as symptoms, noises in the head, convulsive trembling and twitchings of the muscles, with difficulty of breathing.
[142] Dr. Stone, Med. Gaz., 1848, vol. xii. p. 1077.
DETECTION AND SEPARATION OF BENZENE.
§ 149. Benzene is separated from liquids by distillation, and may be recognised by its odour, and by the properties described at [p. 130]. The best process of identification, perhaps, is to purify and convert it into nitro-benzene, and then into aniline, in the following manner:—
1. Purification.—The liquid is agitated with a solution of caustic soda; this dissolves out of the benzene any bodies of an acid character, such as phenol, &c. The purified liquid should again be distilled, collecting that portion of the distillate which passes over between 65° and 100°; directly the thermometer attains nearly the 100°, the distillation should be stopped. The distillate, which contains all the benzene present, is next shaken with concentrated sulphuric acid in the cold; this will dissolve out all the hydrocarbons of the ethylene and acetylene series. On removing the layer of benzene from the acid, it must be again shaken up with dilute soda, so as to remove any trace of acid. The benzene is, by this rather complicated series of operations, obtained in a very fair state of purity, and may be converted into nitro-benzene, as follows:—
2. Conversion into Nitro-Benzene.—The oily liquid is placed in a flask, and treated with four times its volume of fuming nitric acid. The flask must be furnished with an upright condenser; a vigorous action mostly takes place without the application of heat, but if this does not occur, the flask may be warmed for a few minutes.
After the conversion is over, the liquid, while still warm, must be transferred into a burette furnished with a glass tap, or to a separating funnel, and all, except the top layer, run into cold water; if benzene was originally present, either oily drops of nitro-benzene will fall, or if the benzene was only in small quantity, a fine precipitate will gradually settle down to the bottom of the vessel, and a distinct bitter-almond smell be observed; but, if there be no benzene in the original liquid, and, consequently, no nitro-benzene formed, no such appearance will be observed.
3. Conversion into Aniline.—The nitro-benzene may itself be identified by collecting it on a wet filter, dissolving it off the filter by alcohol, acidifying the alcoholic solution by hydrochloric acid, and then boiling it for some time with metallic zinc. In this way aniline is formed by reduction. On neutralising and diluting the liquid, and cautiously adding a little clear solution of bleaching-powder, a blue or purple colour passing to brown is in a little time produced.
3. TERPENES—ESSENTIAL OILS—OIL OF TURPENTINE.
§ 150. The terpenes are hydrocarbons of the general formula CnH2n-4. The natural terpenes are divided into three classes:—
1. The true terpenes, formula (C10;H16)—a large number of essential oils, such as those of turpentine, orange peel, nutmeg, caraway, anise, thyme, &c., are mainly composed of terpenes.
2. The cedrenes, formula (C15H24)—the essential oil of cloves, rosewood, cubebs, calamus, cascarilla, and patchouli belong to this class.
3. The colophene hydrocarbons, formula (C20H32), represented by colophony.
Of all these, oil of turpentine alone has any toxicological significance; it is, however, true that all the essential oils, if taken in considerable doses, are poisonous, and cause, for the most part, vascular excitement and complex nervous phenomena, but their action has not been very completely studied. They may all be separated by distillation, but a more convenient process for recovering an essential oil from a liquid is to shake it up with petroleum ether, separating the petroleum and evaporating spontaneously; by this means the oil is left in a fair state of purity.
4. OIL OF TURPENTINE—SPIRIT OF TURPENTINE—“TURPS.”
§ 151. Various species of pine yield a crude turpentine, holding in solution more or less resin. The turpentine may be obtained from this exudation by distillation, and when the first portion of the distillate is treated with alkali, and then redistilled, the final product is known under the name of “rectified oil of turpentine,” and is sometimes called “camphene.” It mainly consists of terebenthene. Terebenthene obtained from French turpentine differs in some respects from that obtained from English or American turpentine. They are both mobile, colourless liquids, having the well-known odour of turpentine and highly refractive; but the French terebenthene turns a ray of polarised light to the left -40·3° for the sodium ray, and the English to the right +21·5°; the latter terebenthene is known scientifically as austra-terebenthene. This action on polarised light is retained in the various compounds and polymers of the two turpentine oils.
The specific gravity of turpentine oil is ·864; its boiling point, when consisting of pure terebenthene, 156°, but impurities may raise it up to 160°; it is combustible and burns with a smoky flame. Oil of turpentine is very soluble in ether, petroleum ether, carbon disulphide, chloroform, benzene, fixed and essential oils, and by the use of these solvents it is conveniently separated from the contents of the stomach. It is insoluble in water, glycerin, and dilute alkaline and acid solutions; and very soluble in absolute alcohol, from which it may be precipitated by the addition of water.
It is polymerised by the action of strong sulphuric acid, the polymer, of course, boiling at a higher temperature than the original oil. With water it forms a crystalline hydrate (C10H20O2,H2O). On passing nitrosyl chloride gas into the oil, either pure or diluted with chloroform or alcohol, the mixture being cooled by ice, a white crystalline body is deposited, of the formula C10H16(NOCl). By treating this compound with alcoholic potash, the substitution product (C10H16NO) is obtained. By treating turpentine with an equal bulk of warm water, and shaking it in a large bottle with air, camphoric acid and peroxide of hydrogen are formed. When turpentine oil is left in contact with concentrated hydrochloric acid, there is formed terebenthene dihydrochloride (C10H162HCl), which forms rhombic plates, insoluble in water, and decomposable by boiling alcoholic potash, with formation of terpinol, (C10H17)2O. The dihydrochloride gives a colour-reaction with ferric chloride. This is an excellent test—not, it is true, confined to oil of turpentine—but common to the dihydrochlorides of all the terpenes. A few drops of the oil are stirred in a porcelain capsule with a drop of hydrochloric acid, and one of ferric chloride solution; on gently heating, there is produced first a rose colour, then a violet-red, and lastly a blue.
§ 152. Effects of the Administration of Turpentine.—L. W. Liersch[143] exposed animals to the vapour of turpentine, and found that a cat and a rabbit died within half an hour. There was observed uneasiness, reeling, want of power in the limbs (more especially in the hinder extremities), convulsions partial, or general, difficulty of respiration; and the heart’s action was quickened. Death took place, in part, from asphyxia, and in part was attributable to a direct action on the nervous centres. The autopsy showed congestion of the lungs, ecchymoses of the kidney, and much blood in the liver and spleen. Small doses of turpentine-vapour cause (according to Sir B. W. Richardson)[144] giddiness, deficient appetite, and anæmia. From half an ounce to an ounce is frequently prescribed in the country as a remedy for tape-worm; in smaller quantities it is found to be a useful medicine in a great variety of ailments. The larger doses produce a kind of intoxication with giddiness, followed often by purging and strangury, not unfrequently blood and albumen (or both) is found in the urine. When in medical practice I have given the oil, and seen it given by others, in large doses for tape-worm to adults, in perhaps 40 cases, but in no one instance were the symptoms severe; the slight intoxication subsided quickly, and in a few hours the patients recovered completely. Nevertheless it has been known to destroy the lives of children, and cause most serious symptoms in adults. Two fatal cases are mentioned by Taylor; one was that of a child who died fifteen hours after taking half an ounce of the oil; in another an infant, five months old, died rapidly from a teaspoonful. The symptoms in these fatal cases were profound coma and slight convulsions; the pupils were contracted, and there was slow and irregular breathing. Turpentine is eliminated in a changed form by the kidneys, and imparts an odour of violet to the urine; but the nature of the odoriferous principle has not yet been investigated.
[143] Clarus in Schmidt’s Jahrbücher, Bd. cxvii., i. 1863; and Vierteljahrsschr. für ger. Med., xxii., Oct. 1862.
[144] Brit. and For. Med.-Chir. Review, April 1863.