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VIII.—Bisulphide of Carbon.

§ 208. Bisulphide of carbon—carbon disulphide, carbon sulphide (CS₂)—is a colourless, volatile fluid, strongly refracting light. Commercial samples have a most repulsive and penetrating odour, but chemically pure carbon sulphide has a smell which is not disagreeable. The boiling-point is 47°; the specific gravity at 0° is 1·293. It is very inflammable, burning with a blue flame, and evolving sulphur dioxide; is little soluble in water, but mixes easily with alcohol or ether. Bisulphide of carbon, on account of its solvent powers for sulphur, phosphorus, oils, resins, caoutchouc, gutta-percha, &c., is in great request in certain industries. It is also utilised for disinfecting purposes, the liquid being burnt in a lamp.

§ 209. Poisoning by Carbon Bisulphide.—In spite of the cheapness and numerous applications of this liquid, poisoning is very rare. There appears to be a case on record of attempted self-destruction by this agent, in which a man took 2 ozs. (56·7 c.c.) of the liquid, but without a fatal result. The symptoms in this case were pallor of the face, wide pupils, frequent and weak pulse, lessened bodily temperature, and spasmodic convulsions. Carbon disulphide was detected in the breath by leading the expired air through an alcoholic solution of triethyl-phosphin, with which it struck a red colour. It could also be found in the urine in the same way. An intense burning in the throat, giddiness, and headache lasted for several days.

§ 210. Experiments on animals have been frequent, and it is found to be fatal to all forms of animal life. There is, indeed, no more convenient agent for the destruction of various noxious insects, such as moths, the weevils in biscuits, the common bug, &c., than bisulphide of carbon. It has also been recommended for use in exterminating mice and rats.[193] Different animals show various degrees of sensitiveness to the vapour; frogs and cats being less affected by it than birds, rabbits, and guinea-pigs. It is a blood poison; methæmoglobin is formed, and there is disintegration of the red blood corpuscles. There is complete anæsthesia of the whole body, and death occurs through paralysis of the respiratory centre, but artificial respiration fails to restore life.

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§ 211. Chronic Poisoning.—Of some importance is the chronic poisoning by carbon disulphide, occasionally met with in manufactures necessitating the daily use of large quantities for dissolving caoutchouc, &c. When taken thus in the form of vapour daily for some time, it gives rise to a complex series of symptoms which may be divided into two principal stages—viz., a stage of excitement and one of depression. In the first phase, there is more or less permanent headache, with considerable indigestion, and its attendant loss of appetite, nausea, &c. The sensitiveness of the skin is also heightened, and there are curious sensations of creeping, &c. The mind at the same time in some degree suffers, the temper becomes irritable, and singing in the ears and noises in the head have been noticed. In one factory a workman suffered from an acute mania, which subsided in two days upon removing him from the noxious vapour (Eulenberg). The sleep is disturbed by dreams, and, according to Delpech,[194] there is considerable sexual excitement, but this statement has in no way been confirmed. Pains in the limbs are a constant phenomenon, and the French observers have noticed spasmodic contractions of certain groups of muscles.

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The stage of depression begins with a more or less pronounced anæsthesia of the skin. This is not confined to the outer skin, but also affects the mucous membranes; patients complain that they feel as if the tongue were covered with a cloth. The anæsthesia is very general. In a case recorded by Bernhardt,[195] a girl, twenty-two years old, who had worked six weeks in a caoutchouc factory, suffered from mental weakness and digestive troubles; there was anæsthesia and algesis of the whole skin. In these advanced cases the mental debility is very pronounced, and there is also weakness of the muscular system. Paralysis of the lower limbs has been noted, and in one instance a man had his right hand paralysed for two months. It seems uncertain how long a person is likely to suffer from the effects of the vapour after he is removed from its influence. If the first stage of poisoning only is experienced, then recovery is generally rapid; but if mental and muscular weakness and anæsthesia of the skin have been developed, a year has been known to elapse without any considerable improvement, and permanent injury to the health may be feared.

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§ 212. Post-mortem Appearances.—The pathological appearances found after sudden death from disulphide of carbon are but little different to those found after fatal chloroform breathing.

§ 213. Detection and Separation of Carbon Disulphide.—The extreme volatility of the liquid renders it easy to separate it from organic liquids by distillation with reduced pressure in a stream of CO₂. Carbon disulphide is best identified by (1) Hofman’s test, viz., passing the vapour into an ethereal solution of triethyl-phosphin, (C₂H₅)₃P. Carbon disulphide forms with triethyl-phosphin a compound which crystallises in red scales. The crystals melt at 95° C., and have the following formula—P(C₂H₅)₃CS₂. This will detect 0·54 mgrm. Should the quantity of bisulphide be small, no crystals may be obtained, but the liquid will become of a red colour. (2) CS₂ gives, with an alcoholic solution of potash, a precipitate of potassic xanthate, CS₂C₂H₅OK.

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IX.—The Tar Acids—Phenol—Cresol.

§ 216. Carbolic Acid. Syn. Phenol, Phenyl Alcohol, Phenylic Hydrate; Phenic Acid; Coal-Tar Creasote.—The formula for carbolic acid is C₆H₅HO. The pure substance appears at the ordinary temperature as a colourless solid, crystallising in long prisms; the fusibility of the crystals is given variously by different authors: from my own observation, the pure crystals melt at 40°-41°, any lower melting-point being due to the presence of cresylic acid or other impurity; the crystals again become solid about 15°. Melted carbolic acid forms a colourless limpid fluid, sinking in water. It boils under the ordinary pressure at 182°, and distils without decomposition; it is very readily and completely distilled in a vacuum at about the temperature of 100°. After the crystals have been exposed to the air, they absorb water, and a hydrate is formed containing 16·07 per cent. of water. The hydrate melts at 17°, any greater hydration prevents the crystallisation of the acid; a carbolic acid, containing about 27 per cent. of water, and probably corresponding to the formula C₆H₆O,2H₂O, is obtained by gradually adding water to carbolic acid so long as it continues to be dissolved. Such a hydrate dissolves in 11·1 times its measure of water, and contains 8·56 per cent. of real carbolic acid. Carbolic acid does not redden litmus, but produces a greasy stain on paper, disappearing on exposure to the air; it has a peculiar smell, a burning numbing taste, and in the fluid state it strongly refracts light. Heated to a high temperature it takes fire, and burns with a sooty flame.

When an aqueous solution of carbolic acid is shaken up with ether, benzene, carbon disulphide, or chloroform, it is fully dissolved by the solvent, and is thus easily separated from most solutions in which it exists in the free state. Petroleum ether, on the other hand, only slightly dissolves it in the cold, more on warming. Carbolic acid mixes in all proportions with glycerin, glacial or acetic acid, and alcohol. It coagulates albumen, the precipitate being soluble in an excess of albumen; it also dissolves iodine, without changing its properties. It dissolves many resins, and also sulphur, but, on boiling, sulphuretted hydrogen is disengaged. Indigo blue is soluble in hot carbolic acid, and may be obtained in crystals on cooling. Carbolic acid is contained in castoreum, a secretion derived from the beaver, but it has not yet been detected in the vegetable kingdom. The source of carbolic acid is at present coal-tar, from which it is obtained by a process of distillation. There are, however, a variety of chemical actions in the course of which carbolic acid is formed.

§ 217. The common disinfecting carbolic acid is a dark reddish liquid, with a very strong odour; at present there is very little phenol in it; it is mainly composed of meta- and para-cresol. It is officinal in Germany, and there must contain at least 50 per cent. of the pure carbolic acid. The pure crystallised carbolic acid is officinal in our own and all the continental pharmacopœias. In the British Pharmacopœia, a solution of carbolic acid in glycerin is officinal; the proportions are 1 part of carbolic acid and 4 parts of glycerin, that is, strength by measure = 20 per cent. The Pharmacopœia Germanica has a liquor natri carbolici, made with 5 parts carbolic acid, 1 caustic soda, and 4 of water; strength in carbolic acid = 50 per cent. There is also a strongly alkaline crude sodic carbolate in use as a preservative of wood.

There are various disinfecting fluids containing amounts of carbolic acid, from 10 per cent. upwards. Many of these are somewhat complex mixtures, but, as a rule, any poisonous properties they possess are mainly due to their content of phenol or cresol. A great variety of disinfecting powders, under various names, are also in commerce, deriving their activity from carbolic acid. Macdougall’s disinfecting powder is made by adding a certain proportion of impure carbolic acid to a calcic sulphite, which is prepared by passing sulphur dioxide over ignited limestone.

Calvert’s carbolic acid powder is made by adding carbolic acid to the siliceous residue obtained from the manufacture of aluminic sulphate from shale. There are also various carbolates which, by heating or decomposing with sulphuric acid, give off carbolic acid.

Carbolic acid soaps are also made on a large scale—the acid is free, and some of the soaps contain as much as 10 per cent. In the inferior carbolic acid soaps there is little or no carbolic acid, but cresylic takes its place. Neither the soaps nor the powders have hitherto attained any toxicological importance, but the alkaline carbolates are very poisonous.

§ 218. The chief uses of carbolic acid are indicated by the foregoing enumeration of the principal preparations used in medicine and commerce. The bulk of the carbolic acid manufactured is for the purposes of disinfection. It is also utilised in the preparation of certain colouring matters or dyes, and during the last few years has had another application in the manufacture of salicylic acid. In medicine it is administered occasionally internally, while the antiseptic movement in surgery, initiated by Lister, has given it great prominence in surgical operations.

§ 219. Statistics.—The tar acids, i.e., pure carbolic acid and the impure acids sold under the name of carbolic acid, but consisting (as stated before) mainly of cresol, are, of all powerful poisons, the most accessible, and the most recklessly distributed. We find them at the bedside of the sick, in back-kitchens, in stables, in public and private closets and urinals, and, indeed, in almost all places where there are likely to be foul odours or decomposing matters. It is, therefore, no wonder that poisoning by carbolic acid has, of late years, assumed large proportions. The acid has become vulgarised, and quite as popularly known, as the most common household drugs or chemicals.[196] This familiarity is the growth of a very few years, since it was not discovered until 1834, and does not seem to have been used by Lister until about 1863. It was not known to the people generally until much later. At present it occupies the third place in fatality of all poisons in England. The following table shows that, in the past ten years, carbolic acid has killed 741 people, either accidentally or suicidally; there is also one case of murder by carbolic acid within the same period, bringing the total up to 742:—

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DEATHS FROM CARBOLIC ACID IN ENGLAND AND WALES DURING THE TEN YEARS ENDING 1892.

Accident or Negligence.
Ages,	0-1	1-5	5-15	15-25	25-65	65 and above	Total
Males,	2	39	13	5	83	8	150
Females,	2	21	7	13	51	7	101
Totals,	4	60	20	18	134	15	251
Suicide.
Ages,				15-25	25-65	65 and above	Total
Males,				26	186	7	219
Females,				72	194	5	271
Totals,				98	380	12	490

Falck has collected, since the year 1868, no less than 87 cases of poisoning from carbolic acid recorded in medical literature. In one of the cases the individual died in nine hours from a large dose of carbolate of soda; in a second, violent symptoms were induced by breathing for three hours carbolic acid vapour; in the remaining 85, the poisoning was caused by the liquid acid. Of these 85 persons, 7 had taken the poison with suicidal intent, and of the 7, 5 died; 39 were poisoned through the medicinal use of carbolic acid, 27 of the 39 by the antiseptic treatment of wounds by carbolic acid dressings, and of these 8 terminated fatally; in 8 cases, symptoms of poisoning followed the rubbing or painting of the acid on the skin for the cure of scabies, favus, or psoriasis, and 6 of these patients died. In 4 cases, carbolic acid enemata, administered for the purpose of dislodging ascarides, gave rise to symptoms of poisoning, and in one instance death followed.

The substitution of carbolic acid for medicine happened as follows:—

	Cases.
Taken instead of Tincture of Opium,	1
Ta„en inst„ad of  Infusion of Senna,	3
Ta„en inst„ad of  Mineral Water,	2
Ta„en inst„ad of  other Mixtures,	3
Ta„en inwardly instead of applied outwardly,	3
	12

Of these 12, 8 died.

Again, 10 persons took carbolic acid in mistake for various alcoholic drinks, such as schnapps, brandy, rum, or beer, and 9 of the 10 succumbed; 17 persons drank carbolic acid simply “by mistake,” and of these 13 died. Thus, of the whole 85 cases, no less than 51 ended fatally—nearly 60 per cent.

It must be always borne in mind that, with regard to statistics generally, the term “carbolic acid” is not used by coroners, juries, or medical men, in a strictly chemical sense, the term being made to include disinfecting fluids which are almost wholly composed of the cresols, and contain scarcely any phenol. In this article, with regard to symptoms and pathological appearances, it is only occasionally possible to state whether the pure medicinal crystalline phenol or a mixture of tar-acids was the cause of poisoning.

§ 220. Fatal Dose.—The minimum fatal dose for cats, dogs, and rabbits, appears to be from ·4 to ·5 grm. per kilogram. Falck has put the minimum lethal dose for man at 15 grms. (231·5 grains), which would be about ·2 per kilo., basing his estimate on the following reasoning. In 33 cases he had a fairly exact record of the amount of acid taken, and out of the 33, he selects only those cases which are of use for the decision of the question. Among adults, in 5 cases the dose was 30 grms., and all the 5 cases terminated by death, in times varying from five minutes to an hour and a half. By other 5 adults a dose of 15 grms. was taken; of the 5, 3 men and a woman died, in times varying from forty-five minutes to thirty hours, while 1 woman recovered. Doses of 11·5, 10·8, and 9 grms. were taken by different men, and recovered from; on the other hand, a suicide who took one and a half teaspoonful (about 6 grms.) of the concentrated acid, died in fifty minutes. Doses of ·3 to 3 grms. have caused symptoms of poisoning, but the patients recovered, while higher doses than 15 grms. in 12 cases, with only one exception, caused death. Hence, it may be considered tolerably well established, that 15 grms. (231·5 grains) may be taken as representing the minimum lethal dose.

The largest dose from which a person appears to have recovered is, I believe, that given in a case recorded by Davidson, in which 150 grms. of crude carbolic acid had been taken. It must, however, be remembered that, as this was the impure acid, probably only half of it was really carbolic acid. The German Pharmacopœia prescribes as a maximum dose ·05 grm (·7 grain) of the crystallised acid, and a daily maximum quantity given in divided doses of ·15 grm. (2·3 grains).

§ 221. Effects on Animals.—Carbolic acid is poisonous to both animal and vegetable life.

Infusoria.—One part of the acid in 10,000 parts of water rapidly kills ciliated animalcules,—the movements become sluggish, the sarcode substance darker, and the cilia in a little time cease moving.

Fish.—One part of the acid in 7000 of water kills dace, minnows, roach, and gold fish. In this amount of dilution the effect is not apparent immediately; but, at the end of a few hours, the movements of the fish become sluggish, they frequently rise to the surface to breathe, and at the end of twenty-four hours are found dead. Quantities of carbolic acid, such as 1 part in 100,000 of water, appear to affect the health of fish, and render them more liable to be attacked by the fungus growth which is so destructive to fish-life in certain years.

Frogs.—If ·01 to ·02 grm. of carbolic acid be dissolved in a litre of water in which a frog is placed, there is almost immediately signs of uneasiness in the animal, showing that pain from local contact is experienced; a sleepy condition follows, with exaltation of reflex sensibility; convulsions succeed, generally, though not always; then reflex sensibility is diminished, ultimately vanishes, and death occurs; the muscles and nerves still respond to the electric current, and the heart beats, but slowly and weakly, for a little after the respiration has ceased.

§ 222. Warm-blooded Animals.—For a rabbit of the average weight of 2 kilos., ·15 grm. is an active dose, and ·3 a lethal dose (that is ·15 per kilo.). The sleepy condition of the frog is not noticed, and the chief symptoms are clonic convulsions with dilatation of the pupils, the convulsions passing into death, without a noticeable paralytic stage. The symptoms observed in poisoned dogs are almost precisely similar, the dose, according to body-weight, being the same. It has, however, been noticed that with doses large enough to produce convulsions, a weak condition has supervened, causing death in several days. There appears to be no cumulative action, since equal toxic doses can be given to animals for some time, and the last dose has no greater effect than the first or intermediate ones. The pathological appearances met with in animals poisoned by the minimum lethal doses referred to are not characteristic; but there is a remarkable retardation of putrefaction.

§ 223. Symptoms in Man, external application.—A 5 per cent. solution of carbolic acid, applied to the skin, causes a peculiar numbness, followed, it may be, by irritation. Young subjects, and those with sensitive skins, sometimes exhibit a pustular eruption, and concentrated solutions cause more or less destruction of the skin. Lemaire[197] describes the action of carbolic acid on the skin as causing a slight inflammation, with desquamation of the epithelium, followed by a very permanent brown stain, but this he alone has observed. Applied to the mucous membrane, carbolic acid turns the epithelial covering white; the epithelium, however, is soon thrown off, and the place rapidly heals; there is the same numbing, aconite-like feeling before noticed. The vapour of carbolic acid causes redness of the conjunctivæ, and irritation of the air-passages. If the application is continued, the mucous membrane swells, whitens, and pours out an abundant secretion.

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Dr. Whitelock, of Greenock, has related two instances in which children were treated with carbolic acid lotion (strength 2¹⁄₂ per cent.) as an application to the scalp for ringworm; in both, symptoms of poisoning occurred—in the one, the symptoms at once appeared; in the other they were delayed some days. In order to satisfy his mind, the experiment was repeated twice, and each time gastric and urinary troubles followed.

Nussbaum, of Munich, records a case[198] in which symptoms were induced by the forcible injection of a solution of carbolic acid into the cavity of an abscess.

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Macphail[199] gives two cases of poisoning by carbolic acid from external use. In the one, a large tumour had been removed from a woman aged 30, and the wound covered with gauze steeped in a solution of carbolic acid, in glycerin, strength 10 per cent.; subsequently, there was high fever, with diminished sulphates in the urine, which smelt strongly of carbolic acid, and was very dark. On substituting boracic acid, none of these troubles were observed. The second case was that of a servant suffering from axillary abscess; the wound was syringed out with carbolic acid solution, of strength 2¹⁄₂ per cent., when effects were produced similar to those in the first case. It was noted that in both these cases the pulse was slowed. Scattered throughout surgical and medical literature, there are many other cases recorded, though not all so clear as those cited. Several cases are also on record in which poisonous symptoms (and even death) have resulted from the application of carbolic acid lotion as a remedy for scabies or itch.

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A surgeon prescribed for two joiners who suffered from scabies a lotion, which was intended to contain 30 grms. of carbolic acid in 240 c.c. of water; but the actual contents of the flasks were afterwards from analysis estimated by Hoppe-Seyler to be 33·26 grms., and the quantity used by each to be equal to 13·37 grms. (206 grains) of carbolic acid. One of the men died; the survivor described his own symptoms as follows:—He and his companion stood in front of the fire, and rubbed the lotion in; he rubbed it into his legs, breast, and the front part of his body; the other parts were mutually rubbed. Whilst rubbing his right arm, and drying it before the fire, he felt a burning sensation, a tightness and giddiness, and mentioned his sensations to his companion, who laughed. This condition lasted from five to seven minutes, but he did not remember whether his companion complained of anything, nor did he know what became of him, nor how he himself came to be in bed. He was found holding on to the joiner’s bench, looking with wide staring eyes, like a drunken man, and was delirious for half an hour. The following night he slept uneasily and complained of headache and burning of the skin. The pulse was 68, the appearance of the urine, appetite, and sense of taste were normal; the bowels confined. He soon recovered.

The other joiner seems to have died as suddenly as if he had taken prussic acid. He called to his mother, “Ich habe einen Rausch,” and died with pale livid face, after taking two deep, short inspirations.

The post-mortem examination showed the sinuses filled with much fluid blood, and the vessels of the pia mater congested. Frothy, dark, fluid blood was found in the lungs, which were hyperæmic; the mucous tissues of the epiglottis and air-tubes were reddened, and covered with a frothy slime. Both ventricles—the venæ cavæ and the vessels of the spleen and kidneys—were filled with dark fluid blood. The muscles were very red; there was no special odour. Hoppe-Seyler recognised carbolic acid in the blood and different organs of the body.[200]

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In another case, a child died from the outward use of a 2 per cent. solution of carbolic acid. It is described as follows:—An infant of seven weeks old suffered from varicella, and one of the pustules became the centre of an erysipelatous inflammation. To this place a 2 per cent. solution of carbolic acid was applied by means of a compress steeped in the acid; the following morning the temperature rose from 36·5° (97·7° F.) to 37° (98·6° F.), and poisonous symptoms appeared. The urine was coloured dark. There were sweats, vomitings, and contracted pupils, spasmodic twitchings of the eyelids and eyes, with strabismus, slow respiration, and, lastly, inability to swallow. Under the influence of stimulating remedies the condition temporarily improved, but the child died twenty-three and a half hours after the first application. An examination showed that the vessels of the brain and the tissue of the lungs were abnormally full of blood. The liver was softer than natural, and exhibited a notable yellowishness in the centre of the acini. Somewhat similar appearances were noticed in the kidneys, the microscopic examination of which showed the tubuli contorti enlarged and filled with fatty globules. In several places the epithelium was denuded, in other places swollen, and with the nuclei very visible.

In an American case,[201] death followed the application of carbolic acid to a wound. A boy had been bitten by a dog, and to the wound, at one o’clock in the afternoon, a lotion, consisting of nine parts of carbolic acid and one of glycerin, was applied. At seven o’clock in the evening the child was unconscious, and died at one o’clock the following day.

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§ 224. Internal Administration.—Carbolic acid may be taken into the system, not alone by the mouth, but by the lungs, as in breathing carbolic acid spray or carbolic acid vapour. It is also absorbed by the skin when outwardly applied, or in the dressing or the spraying of wounds with carbolic acid. Lastly, the ordinary poisonous effects have been produced by absorption from the bowel, when administered as an enema. When swallowed undiluted, and in a concentrated form, the symptoms may be those of early collapse, and speedy death. Hence, the course is very similar to that witnessed in poisoning by the mineral acids.

If lethal, but not excessive doses of the diluted acid are taken, the symptoms are—a burning in the mouth and throat, a peculiarly unpleasant persistent taste, and vomiting. There is faintness with pallor of the face, which is covered by a clammy sweat, and the patient soon becomes unconscious, the pulse small and thready, and the pupils sluggish to light. The respiration is profoundly affected; there is dyspnœa, and the breathing becomes shallow. Death occurs from paralysis of the respiratory apparatus, and the heart is observed to beat for a little after the respiration has ceased. All these symptoms may occur from the application of the acid to the skin or to mucous membranes, and have been noticed when solutions of but moderate strength have been used—e.g., there are cases in gynæcological practice in which the mucous membrane (perhaps eroded) of the uterus has been irrigated with carbolic acid injections. Thus, Küster[202] relates a case in which, four days after confinement, the uterus was washed out with a 2 per cent. solution of carbolic acid without evil result. Afterwards a 5 per cent. solution was used, but it at once caused violent symptoms of poisoning, the face became livid, clonic convulsions came on, and at first loss of consciousness, which after an hour returned. The patient died on the ninth day. There was intense diphtheria of the uterus and vagina. Several other similar cases (although not attended with such marked or fatal effects) are on record.[203]

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§ 225. The symptoms of carbolic acid poisoning admit of considerable variation from those already described. The condition is occasionally that of deep coma. The convulsions may be general, or may affect only certain groups of muscles. Convulsive twitchings of the face alone, and also muscular twitchings only of the legs, have been noticed. In all cases, however, a marked change occurs in the urine. Subissi[204] has noted the occurrence of abortion, both in the pig and the mare, as a result of carbolic acid, but this effect has not hitherto been recorded in the human subject.

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It has been experimentally shown by Küster, that previous loss of blood, or the presence of septic fever, renders animals more sensitive to carbolic acid. It is also said that children are more sensitive than adults.

The course of carbolic acid poisoning is very rapid. In 35 cases collected by Falck, in which the period from the taking of the poison to the moment of death was accurately noted, the course was as follows:—12 patients died within the first hour, and in the second hour 3; so that within two hours 15 died. Between the third and the twelfth hour, 10 died; between the thirteenth and the twenty-fourth hour, 7 died; and between the twenty-fifth and the sixtieth hour, only 3 died. Therefore, slightly over 71 per cent. died within twelve hours, and 91·4 per cent. within the twenty-four hours.

§ 226. Changes in the Urine.—The urine of patients who have absorbed in any way carbolic acid is dark in colour, and may smell strongly of the acid. It is now established—chiefly by the experiments and observations of Baumann[205]—that carbolic acid, when introduced into the body, is mainly eliminated in the form of phenyl-sulphuric acid, C₆H₅HSO₄, or more strictly speaking as potassic phenyl-sulphate, C₆H₅KSO₄, a substance which is not precipitated by chloride of barium until it has been decomposed by boiling with a mineral acid. Cresol is similarly excreted as cresol-sulphuric acid, C₆H₄CH₃HSO₄, ortho-, meta-, or para-, according to the kind of cresol injected; a portion may also appear as hydro-tolu-chinone-sulphuric acid. Hence it is that, with doses of phenol or cresol continually increasing, the amount of sulphates naturally in the urine (as estimated by simply acidifying with hydrochloric acid, and precipitating in the cold with chloride of barium) continually decreases, and may at last vanish, for all the sulphuric acid present is united with the phenol. On the other hand, the precipitate obtained by prolonged boiling of the strongly acidified urine, after filtering off any BaSO₄ thrown down in the cold, is ever increasing.

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Thus, a dog voided urine which contained in 100 c.c., ·262 grm. of precipitable sulphuric acid, and ·006 of organically-combined sulphuric acid; his back was now painted with carbolic acid, and the normal proportions were reversed, the precipitable sulphuric acid became ·004 grm., while the organically-combined was ·190 in 100 c.c. In addition to phenyl-sulphuric acid, it is now sufficiently established[206] that hydroquinone () (paradihydroxyl phenol) and pyrocatechin () (orthodihydroxyl phenol) are constant products of a portion of the phenol. The hydroquinone appears in the urine, in the first place, as the corresponding ether-sulphuric acid, which is colourless; but a portion of it is set free, and this free hydroquinone (especially in alkaline urine) is quickly oxidised to a brownish product, and hence the peculiar colour of urine. Out of dark coloured carbolic acid urine the hydroquinone and its products of decomposition can be obtained by shaking with ether; on separation of the ether, an extract is obtained, reducing alkaline silver solution, and developing quinone on warming with ferric chloride.

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To separate pyro-catechin, 200 c.c. of urine may be evaporated to an extract, the extract treated with strong alcohol, the alcoholic liquid evaporated, and the extract then treated with ether. On separation and evaporation of the ether, a yellowish mass is left, from which the pyro-catechin may be extracted by washing with a small quantity of water. This solution will reduce silver solution in the cold, or, if treated with a few drops of ferric chloride solution, show a marked green colour, changing on being alkalised by a solution of sodic hydro-carbonate to violet, and then on being acidified by acetic acid, changing back again to green. According to Thudichum,[207] the urine of men and dogs, after the ingestion of carbolic acid, contains a blue pigment.

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§ 227. The Action of Carbolic Acid considered physiologically.—Researches on animals have elucidated, in a great measure, the mode in which carbolic acid acts, and the general sequence of effects, but there is still much to be learnt.

E. Küster[208] has shown that the temperature of dogs, when doses of carbolic acid in solution are injected subcutaneously, or into the veins, is immediately, or very soon after the operation, raised. With small and moderate doses, this effect is but slight—from half to a whole degree—on the day after the injection the temperature sinks below the normal point, and only slowly becomes again natural. With doses that are just lethal, first a rise and then a rapid sinking of temperature are observed; but with those excessive doses which speedily kill, the temperature at once sinks without a preliminary rise. The action on the heart is not very marked, but there is always a slowing of the cardiac pulsations; according to Hoppe-Seyler the arteries are relaxed. The respiration is much quickened; this acceleration is due to an excitement of the vagus centre, since Salkowsky has shown that section of the vagus produces a retardation of the respiratory wave. Direct application of the acid to muscles or nerves quickly destroys their excitability without a previous stage of excitement. The main cause of the lethal action of carbolic acid—putting on one side those cases in which it may kill by its local corrosive action—appears to be paralysis of the respiratory nervous centres. The convulsions arise from the spinal cord. On the cessation of the convulsions, the superficial nature of the breathing assists other changes by preventing the due oxidation of the blood.

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