Chapter XXIV: Part V: More or Less Volatile Poisonous Substances Capable of Being (4)

In commerce there are three kinds of nitro-benzene--the purest, with the characters given above; a heavier nitro-benzene, boiling at 210° to 220°; and a very heavy variety, boiling at 222° to 235° The last is specially used for the preparation of aniline, or aniline blue. Nitro-benzene has been used as an adulterant of bitter almond oil, but the detection is easy (see “Foods,” p. 551). Nitro-benzene was first discovered by Mitscherlich in 1834, and its poisonous properties were first pointed out by Casper[219] in 1859. Its technical use in perfumes, &c., dates from about 1848, and in the twenty-eight years intervening between that date and 1876, Jübell[220] has collected 42 cases of poisoning by this agent, 13 of which were fatal. One of these cases was suicidal, the rest accidental.

[219] _Vierteljahrsschrift für ger. Med._, 1859, Bd. xvi. p. 1.

[220] _Die Vergiftungen mit Blausäure u. Nitro-benzol in forensischer Beziehung_, Erlangen, 1876.

§ 240. =Effects of Poisoning by Nitro-benzene.=--Nitro-benzene is a very powerful poison, whether taken in the form of vapour or as a liquid. The action of the vapour on animals has been studied by Eulenberg[221] and others. One experiment will serve as an illustration. Fifteen grms. of nitro-benzene were evaporated on warm sand under a glass shade, into which a cat was introduced. There was immediately observed in the animal much salivation, and quickened and laboured breathing. After thirty minutes’ exposure, on removing the shade to repeat the dose of 15 grms., the cat for the moment escaped. On being put back there was again noticed the salivation and running at the eyes, with giddiness, and repeated rising and falling. The animal at last, about one hour and forty minutes after the first dose, succumbed with dyspnœa, and died with progressive paralysis of the respiration. The membranes of the brain were found gorged with blood, the lungs liver-coloured, the mucous membrane of the trachea--to the finest sub-divisions of the bronchia--reddened, inflamed, and clothed with a fine frothy mucus. The left side of the heart was filled with thick black blood. The bladder contained 8 grms. of clear urine, in which aniline was discovered. There was a notable smell of bitter almonds.

[221] _Gewerbe Hygiene_, S. 607, Berlin, 1876.

§ 241. The effects of the vapour on man are somewhat different in their details to those just described. In a remarkable case related by Dr. Letheby, a man, aged 42, had spilt some nitro-benzene over his clothes. He went about several hours breathing an atmosphere of nitro-benzene, he then became drowsy, his expression was stupid, and his gait unsteady, presenting all the appearances of intoxication. The stupor suddenly deepened into coma, and the man died; the fatal course being altogether about nine hours--viz., four hours before coma, and five hours of total insensibility.

An interesting case of poisoning by the vapour is recorded by Taylor.[222] A woman, aged 30, tasted a liquid used for flavouring pastry, which was afterwards chemically identified as pure nitro-benzene. She immediately spat it out, finding that it had an acrid taste, and probably did not swallow more than a drop. In replacing the bottle, however, she spilt about a tablespoonful, and allowed it to remain for some minutes; it was a small room, and the vapour rapidly pervaded it, and caused illness in herself as well as in a fellow-servant. She had a strange feeling of numbness in the tongue, and in three hours and a quarter after the accident was seen by a medical man; she then presented all the appearances of prussic acid poisoning. The eyes were bright and glassy, the features pale and ghastly, the lips and nails purple, as if stained with blackberries, the skin clammy, and the pulse feeble, but the mind was then clear. An emetic was administered, but she suddenly became unconscious; the emetic acted, and brought up a fluid with an odour of nitro-benzene. The stomach-pump was also used, but the liquid obtained had scarcely any odour of nitro-benzene. In about eleven hours consciousness returned, and in about seventeen hours she partially recovered, but complained of flashes of light and strange colours before her eyes. Recovery was not complete for weeks. In this case the small quantity swallowed would probably of itself have produced no symptoms, and the effects are to be mainly ascribed to the breathing of the vapour.

[222] _Poisons_, Third Edition, p. 665.

§ 242. The liquid, when swallowed, acts almost precisely in the same way as the vapour, and the symptoms resemble very much those produced by prussic acid. The great distinction between prussic acid and nitro-benzene poisoning is that, in the latter, there is an interval between the taking of the poison and its effects. This is, indeed, one of the strangest phenomena of nitro-benzene poisoning, for the person, after taking it, may appear perfectly well for periods varying from a quarter of an hour to two or three hours, or even longer, and then there may be most alarming symptoms, followed by rapid death. Poisoning by nitro-benzene satisfies the ideal of the dramatist, who requires, for the purposes of his plot, poisons not acting at once, but with an interval sufficiently prolonged to admit of lengthy rhapsodies and a complicated _dénouement_. On drinking the poison there is a burning taste in the mouth, shortly followed by a very striking blueness or purple appearance of the lips, tongue, skin, nails, and even the conjunctivæ. This curious colour of the skin has, in one or two instances, been witnessed an hour before any feeling of illness manifested itself; vomiting then comes on, the vomited matter smelling of nitro-benzene. The skin is cold, there is great depression, and the pulse is small and weak. The respiration is affected, the breathing being slow and irregular, the breath smelling strongly of the liquid, and the odour often persisting for days. A further stage is that of loss of consciousness, and this comes on with all the suddenness of a fit of apoplexy. The coma is also similar in appearance to apoplectic coma, but there have frequently been seen trismus and convulsions of the extremities. The pupils are dilated and do not react to light, and reflex sensibility is sometimes completely extinguished. Cases vary a little in their main features; in a few the blue skin and the deep sleep are the only symptoms noted. Death, for the most part, occurs after a period of from eight to twenty-four hours (occasionally as soon as four or five hours) after taking the poison.

From the following remarkable train of symptoms in a dog, it is probable, indeed, that nitro-benzene, taken by a human being, might produce death, after a rather prolonged period of time, by its secondary effects:--To a half-bred greyhound[223] were administered 15 grms. of nitro-benzene, when shortly after there were noticed much salivation, shivering, and muscular twitchings. The same dose was repeated at the end of five, of seven, and of eight hours respectively, so that the dog altogether took 60 grms., but with no other apparent symptom than the profuse salivation. On the following day, the dog voided a tapeworm; vomiting supervened; the heart’s action was quickened, and the breathing difficult; convulsions followed, and the pupils were seen to be dilated. For eight days the dog suffered from dyspnœa, quickened pulse, shivering of the legs or of the whole body, tetanic spasms, bloody motions, great thirst and debility. The temperature gradually sank under 25°, and the animal finally died. The autopsy showed, as the most striking change, the whole mucous membrane of the intestinal tract covered with a yellow layer, which chemical analysis proved to be caused by picric acid, and in the urine, liver, and lungs, aniline was discovered.

[223] Eulenberg, _Gewerbe Hygiene_, S. 607.

§ 243. =Fatal Dose.=--It is probable, from recorded cases, that 1 grm. (15·4 grains) would be quite sufficient to kill an adult, and, under favourable circumstances, less than that quantity. It would seem that spirituous liquids especially hasten and intensify the action of nitro-benzene, so that a drunken person, _cæteris paribus_, taking the poison with spirits, would be more affected than taking it under other conditions.

In a case related by Stevenson,[224] in which so small a quantity as 1·74 grm. was taken in seven doses, spread over more than forty-eight hours; there were yet extremely alarming symptoms, and the patient seems to have had a narrow escape. On the other hand, a woman admitted into the General Hospital, Vienna, took 100 grms. (about 3½ ozs.) and recovered; on admission she was in a highly cyanotic condition, with small pulse, superficial respiration, and dribbling of urine, which contained nitro-benzol. Artificial respiration was practised, and camphor injections were administered. Under this treatment consciousness was restored, and the patient recovered. On the fourth day the urine resembled that of a case of cystitis (_Lancet_, Jan. 16, 1894). The quantity of nitro-benzene which would be fatal, if breathed, is not known with any accuracy.

[224] This case is not uninteresting. Through a mistake in reading an extremely illegible prescription, M. S. S., æt. 21, was supplied by a druggist with the following mixture;--

℞. Benzole-Nit., ʒiij.
Ol. Menth, pep., ʒss.
Ol. Olivæ, ʒx.
gutt. xxx., t. ds.

He took on sugar seven doses, each of 20 minims, equalling in all 23 min. (or by weight 27·1 grains, 1·74 grm.) of nitro-benzene--viz., three doses on the first day, three on the second, and one on the morning of the third day. The first two days he was observed to be looking pale and ill, but went on with his work until the seventh dose, which he took on the third day at 9 A.M. About 2 P.M. (or six hours after taking the seventh dose), he fell down insensible, the body pale blue, and with all the symptoms already described in the text, and usually seen in nitro-benzene poisoning. With suitable treatment he recovered. The next morning, from 8 ounces of urine some nitro-benzene was extracted by shaking with chloroform.--Thos. Stevenson, M.D., in _Guy’s Hospital Reports_, MS., vol. xxi., 1876.

§ 244. =Pathological Appearances.=--The more characteristic appearances seem to be, a dark brown or even black colour of the blood, which coagulates with difficulty (an appearance of the blood that has even been noticed during life), venous hyperæmia of the brain and its membranes, and general venous engorgement. In the stomach, when the fluid has been swallowed, the mucous membrane is sometimes reddened diffusely, and occasionally shows ecchymoses of a punctiform character.

§ 245. =The essential action of nitro-benzene= is of considerable physiological interest. The blood is certainly in some way changed, and gives the spectrum of acid hæmatin.[225] Filehne has found that the blood loses, in a great degree, the power of carrying and imparting oxygen to the tissues, and its content of carbon dioxide is also increased. Thus, the normal amount of oxygen gas which the arterial blood of a hound will give up is 17 per cent.; but in the case of a dog which had been poisoned with nitro-benzene, it sank to 1 per cent. During the dyspnœa from which the dog suffered, the carbon dioxide exhaled was greater than the normal amount, and the arterial blood (the natural content of which should have been 30 per cent. of this gas), only gave up 9 per cent. Filehne seeks to explain the peculiar colour of the skin by the condition of the blood, but the explanation is not altogether satisfactory. Some part of the nitro-benzene, without doubt, is reduced to aniline in the body--an assertion often made, and as often contradicted--but it has been found in too many cases to admit of question. It would also seem from the experiment on the dog (p. 186), that a conversion into picric acid is not impossible. A yellow colour of the skin and conjunctivæ, as if picric-acid-stained, has been noticed in men suffering under slow poisoning by nitro-benzene.

[225] Filehne, W., “_Ueber die Gift-Wirkungen des Nitrobenzols_,” _Arch. für exper. Pathol. u. Pharm._, ix. 329.

§ 246. =Detection and Separation of Nitro-Benzene from the Animal Tissues.=--It is evident from the changes which nitro-benzene may undergo that the expert, in any case of suspected nitro-benzene poisoning, must specially look (1) for nitro-benzene, (2) for aniline, and (3) for picric acid. The best general method for the separation of nitro-benzene is to shake up the liquid (or finely-divided solid) with light benzoline (petroleum ether), which readily dissolves nitro-benzene. On evaporation of the petroleum ether, the nitro-benzene is left, perhaps mixed with fatty matters. On treating with cold water, the fats rise to the surface, and the nitro-benzene sinks to the bottom; so that, by means of a separating funnel, the nitro-benzene may be easily removed from animal fats. The oily drops, or fine precipitate believed to be nitro-benzene, may be dissolved in spirit and reduced to aniline by the use of nascent hydrogen, developed from iron filings by hydrochloric acid, and the fluid tested with bleaching powder, or, the aniline itself may be recovered by alkalising the fluid, and shaking up with ether in the separation-tube (p. 156), the ether dissolves the aniline, and leaves it, on spontaneous evaporation, as an oily yellowish mass, which, on the addition of a few drops of sodic hypochlorite, strikes a blue or violet-blue--with acids, a rose-red--and with bromine, a flesh-red. It gives alkaloidal reactions with such general reagents as platinum chloride, picric acid, &c. Aniline itself may be extracted from the tissues and fluids of the body by petroleum ether, but in any special search it will be better to treat the organs as in Stas’ process--that is, with strong alcohol, acidified with sulphuric acid. After a suitable digestion in this menstruum, filter, and then, after evaporating the alcohol, dissolve the alcoholic extract in water; alkalise the aqueous solution, and extract the aniline by shaking it up with light benzoline. On separating the benzoline, the aniline will be left, and may be dissolved in feebly-acid water, and the tests before enumerated tried.

Malpurgo[226] recommends the following test for nitro-benzene:--2 drops of melted phenol, 3 drops of water, and a fragment of caustic potash are boiled in a small porcelain dish, and to the boiling liquid the aqueous solution to be tested is added. On prolonged boiling, if nitro-benzene is present, a crimson ring is produced at the edges of the liquid; this crimson colour, on the addition of a little bleaching powder, turns emerald-green.

[226] _Zeit. anal. Chem._, xxxii. 235.

Oil of bitter almonds may be distinguished from nitro-benzene by the action of manganese dioxide and sulphuric acid; bitter almond oil treated in this way loses its odour, nitro-benzene is unaltered. To apply the test, the liquid must be heated on the water-bath for a little time.

XI.--Dinitro-benzol.

§ 247. =Dinitro-benzol=, C₆H₄(NO₂)₂ (ortho-, meta-, para-).--The ortho-compound is produced by the action of nitric acid on benzol, aided by heat in the absence of strong sulphuric acid to fix water. Some of the para-dinitro-benzol is at the same time produced. The meta-compound is obtained by the action of fuming nitric acid on nitro-benzol at a boiling temperature.

The physical properties of the three dinitro-benzols are briefly as follows:--

Ortho-d. is in the form of needles; m.p. 118°.

Meta-d. crystallises in plates; m.p. 90°.

Para-d. crystallises, like the ortho-compound, in needles, but the melting-point is much higher, 171° to 172°.

Just as nitro-benzol by reduction yields aniline, so do the nitro-benzols on reduction yield ortho-, meta-, or para-phenylene diamines.

Meta-phenylene diamine is an excellent test for nitrites; and, since the commercial varieties of dinitro-benzol either consist mainly or in part of meta-dinitro-benzol, the toxicological detection is fairly simple, and is based upon the conversion of the dinitro-benzol into meta-phenylene-diamine.

Dinitro-benzol is at present largely employed in the manufacture of explosives, such as roburite, sicherheit, and others. It has produced much illness among the workpeople in the manufactures, and amongst miners whose duty it has been to handle such explosives.

§ 248. =Effects of Dinitro-benzol.=--Huber[227] finds that if dinitro-benzol is given to frogs by the mouth in doses of from 100 to 200 mgrms., death takes place in a few hours. Doses of from 2·5 to 5 mgrms. cause general dulness and ultimately complete paralysis, and death in from one to six days.

[227] “_Beiträge zur Giftwirkung des Dinitrobenzols_,” A. Huber, Virchow’s _Archiv_, 1891, Bd. 126, S. 240.

Rabbits are killed by doses of 400 mgrms., in time varying from twenty-two hours to four days.

In a single experiment on a small dog, the weight of which was 5525 grms., the dog died in six hours after a dose of 600 mgrms.

It is therefore probable that a dose of 100 mgrms. per kilo would kill most warm-blooded animals.

A transient exposure to dinitro-benzol vapours in man causes serious symptoms; for instance, in one of Huber’s cases, a student of chemistry had been engaged for one hour and a half only in preparing dinitro-benzol, and soon afterwards his comrades remarked that his face was of a deep blue colour. On admission to hospital, on the evening of the same day, he complained of slight headache and sleeplessness; both cheeks, the lips, the muscles of the ear, the mucous membrane of the lips and cheeks, and even the tongue, were all of a more or less intense blue-grey colour. The pulse was dicrotic, 124; T. 37·2°. The next morning the pulse was slower, and by the third day the patient had recovered.

Excellent accounts of the effects of dinitro-benzol in roburite factories have been published by Dr. Ross[228] and Professor White,[229] of Wigan. Mr. Simeon Snell[230] has also published some most interesting cases of illness, cases which have been as completely investigated as possible. As an example of the symptoms produced, one of Mr. Snell’s cases may be here quoted.

[228] _Medical Chronicle_, 1889, 89.

[229] _Practitioner_, 1889, ii. 15.

[230] _Brit. Med. Journ._, March 3, 1894.

C. F. W., aged 38, consulted Mr. Snell for his defective sight on April 9, 1892. He had been a mixer at a factory for the manufacture of explosives. He was jaundiced, the conjunctiva yellow, and the lips blue. He was short of breath, and after the day’s work experienced aching of the forearms and legs and tingling of the fingers. The urine was black in colour, of sp. gr. 1024; it was examined spectroscopically by Mr. MacMunn, who reported the black colour as due neither to indican, nor to blood, nor bile, but to be caused by some pigment belonging to the aromatic series. The patient’s sight had been failing since the previous Christmas. Vision in the right eye was 6/24, left 6/36, both optic papillæ were somewhat pale. In each eye there was a central scotoma for red, and contraction of the field (see diagram). The man gradually gave up the work, and ultimately seems to have recovered. It is, however, interesting to note that, after having left the work for some weeks, he went back for a single day to the “mixing,” and was taken very ill, being insensible and delirious for five hours.

§ 249. =The Blood in Nitro-benzol Poisoning.=--The effect on the blood has been specially studied by Huber.[231] The blood of rabbits poisoned by dinitro-benzol is of a dark chocolate colour, and the microscope shows destruction of the red corpuscles; the amount of destruction may be gathered from the following:--the blood corpuscles of a rabbit before the experiment numbered 5,588,000 per cubic centimetre; a day after the experiment 4,856,000; a day later 1,004,000; on the third day the rabbit died.

[231] _Op. cit._

In one rabbit, although the corpuscles sank to 1,416,000, yet recovery took place.

Dr. MacMunn[232] has examined specimens of blood from two of Mr. Snell’s patients; he found a distinct departure from the normal; the red corpuscles were smaller than usual, about 5 or 6 µ in diameter, and the appearances were like those seen in pernicious anæmia. Huber, in some of his experiments on animals, found a spectroscopic change in the blood, viz., certain absorption bands, one in the red between C and D, and two in the green between D and E; the action of reducing agents on this dinitro-benzol blood, as viewed in a spectroscope provided with a scale in which C = 48, D = 62, and E = 80·5, was as follows:--

[232] _Op. cit._

Dinitro-Bands.
In Red. In Green.
-----/\-----
50-52 62-66 70-77
After NH₄SO₄, 53-55 62-66 70-77
„ NH₃, 54-58 60-65 70-77
„ NH₄SO₄ + NH₃, 52-55 60-65 70-77

Taking the symptoms as a whole, there has been noted:--a blue colour of the lips, not unfrequently extending over the whole face, and even the conjunctivæ have been of a marked blue colour, giving the sufferer a strange livid appearance. In other cases there have been jaundice, the conjunctivæ and the skin generally being yellow, the lips blue. Occasionally gastric symptoms are present. Sleeplessness is common, and not unfrequently there is some want of muscular co-ordination, and the man staggers as if drunk. In more than one case there has been noticed sudden delirium. There is in chronic cases always more or less anæmia, and the urine is remarkable in its colour, which ranges from a slightly dark hue up to positive blackness. In a large proportion of cases there is ophthalmic trouble, the characteristics of which (according to Mr. Snell) are “failure of sight, often to a considerable degree, in a more or less equal extent on the two sides; concentric attraction of visual field with, in many cases, a central colour scotoma; enlargement of retinal vessels, especially the veins; some blurring, never extensive, of edges of disc, and a varying degree of pallor of its surface--the condition of retinal vessels spoken of being observed in workers with the dinitro-benzol, independently of complaints of defective sight. Cessation of work leads to recovery.”

§ 250. =Detection of Dinitro-benzol.=--Dinitro-benzol may be detected in urine, in blood, and in fluids generally, by the following process:--Place tinfoil in the fluid, and add hydrochloric acid to strong acidity, after allowing the hydrogen to be developed for at least an hour, make the fluid alkaline by caustic soda, and extract with ether in a separating tube; any metaphenylene-diamine will be contained in the ether; remove the ether into a flask, and distil it off; dissolve the residue in a little water.

Acidify a solution of sodium nitrite with dilute sulphuric acid; on adding the solution, if it contains metaphenylene-diamine, a yellow to red colour will be produced, from the formation of Bismarck brown (triamido-phenol).

XII.--Hydrocyanic Acid.

§ 251. =Hydrocyanic Acid= (=hydric cyanide=)--specific gravity of liquid 0·7058 at 18° C., boiling-point 26·5° (80° F.), HCy = 27.--The anhydrous acid is not an article of commerce, and is only met with in the laboratory. It is a colourless, transparent liquid, and so extremely volatile that, if a drop fall on a glass plate, a portion of it freezes. It has a very peculiar peach-blossom odour, and is intensely poisonous. It reddens litmus freely and transiently, dissolves red oxide of mercury freely, forms a white precipitate of argentic cyanide when treated with silver nitrate, and responds to the other tests described hereafter.

§ 252. =Medicinal Preparations of Prussic Acid.=--The B.P. acid is a watery solution of prussic acid; its specific gravity should be 0·997, and it should contain 2 per cent. of the anhydrous acid, 2 per cent. is also the amount specified in the pharmacopœias of Switzerland and Norway, and in that of Borussica (VI. ed.); the latter ordains, however, a spirituous solution, and the Norwegian an addition of 1 per cent. of concentrated sulphuric acid. The French prussic acid is ordered to be prepared of a strength equalling 10 per cent.

The adulterations or impurities of prussic acid are hydrochloric, sulphuric,[233] and formic acids. Traces of silver may be found in the French acid, which is prepared from cyanide of silver. Tartaric acid is also occasionally present. Hydrochloric acid is most readily detected by neutralising with ammonia, and evaporating to dryness in a water-bath; the ammonium cyanide decomposes and volatilises, leaving as a saline residue chloride of ammonium. This may easily be identified by the precipitate of chloride of silver, which its solution gives on testing with silver nitrate, and the deep brown precipitate with Nessler solution. Sulphuric acid is, of course, detected by chloride of barium; formic acid by boiling a small quantity with a little mercuric oxide; if present, the oxide will be reduced, and metallic mercury fall as a grey precipitate. Silver, tartaric acid, and any other fixed impurities are detected by evaporating the acid to dryness, and examining any residue which may be left. It may be well to give the various strengths of the acids of commerce in a tabular form:--

[233] A trace of sulphuric or hydrochloric acid should not be called an _adulteration_, for it greatly assists the preservation, and therefore makes the acid of greater therapeutic efficiency.

Per cent.

British Pharmacopœia, Switzerland, and Bor. (vj), 2
France, 10
Vauquelin’s Acid, 3·3
Scheele’s „ 4 to 5[234]
Riner’s „ 10
Robiquet’s „ 50
Schraeder’s „ 1·5
Duflos’ „ 9
Pfaff’s „ 10
Koller’s „ 25

[234] Strength very uncertain.

In English commerce, the analyst will scarcely meet with any acid stronger than Scheele’s 5 per cent.

Impure oil of bitter almonds contains hydric cyanide in variable quantity, from 5 per cent. up to 14 per cent. There is an officinal preparation obtained by digesting cherry-laurel leaves in water, and then distilling a certain portion over. This _Aqua Lauro-cerasi_ belongs to the old school of pharmacy, and is of uncertain strength, but varies from ·7 to 1 per cent. of HCN.

§ 253. =Poisoning by Prussic Acid.=--Irrespective of suicidal or criminal poisoning, accidents from prussic acid may occur--

1. From the use of the cyanides in the arts.

2. From the somewhat extensive distribution of the acid, or rather of prussic-acid producing substances in the vegetable kingdom.

1. =In the Arts.=--The galvanic silvering[235] and gilding of metals, photography, the colouring of black silks, the manufacture of Berlin blue, the dyeing of woollen cloth, and in a few other manufacturing processes, the alkaline cyanides are used, and not unfrequently fumes of prussic acid developed.

[235] The preparation used for the silvering of copper vessels is a solution of cyanide of silver in potassic cyanide, to which is added finely powdered chalk. Manipulations with this fluid easily develop hydrocyanic acid fumes, which, in one case related by Martin (_Aerztl. Intelligenzbl._, p. 135, 1872), were powerful enough to produce symptoms of poisoning.

2. =In the Animal Kingdom.=--One of the myriapods (_Chilognathen_) contains glands at the roots of the hairs, which secrete prussic acid; when the insect is seized, the poisonous secretion is poured out from the so-called _foramina repugnatoria_.

3. =In the Vegetable Kingdom.=--A few plants contain cyanides, and many contain amygdalin, or bodies formed on the type of amygdalin. In the presence of emulsin (or similar principles) and water, this breaks up into prussic acid and other compounds--an interesting reaction usually represented thus--

C₂₀H₂₇NO₁₁ + 2H₂O = CNH + C₇H₆O + 2C₆H₁₂O₆.

1 equivalent of amygdalin--_i.e._, 457 parts--yielding 1 equivalent of CNH or 27 parts; in other words, 100 parts of amygdalin yield theoretically 5·909 parts of prussic acid,[236] so that, the amount of either being known, the other can be calculated from it.

[236] According to Liebig and Wöhler, 17 grms. of amygdalin yield 1 of prussic acid (_i.e._, 5·7 per cent.) and 8 of oil of bitter almonds. Thirty-four parts of amygdalin, mixed with 66 of emulsin of almonds, give a fluid equalling the strength of acid of most pharmacopœias, viz., 2 per cent.

Greshoff[237] has discovered an amygdalin-like glucoside in the two tropical trees _Pygeum parriflorum_ and _P. latifolium_. The same author states that the leaves of _Gymnema latifolium_, one of the Asclepiads, yields to distillation benzaldehyde hydrocyanide. Both _Lasia_ and _Cyrtosperma_, plants belonging to the natural family of the Orontads, contain in their flowers potassic cyanide. _Pangium edule_, according to Greshoff, contains so much potassic cyanide that he was able to prepare a considerable quantity of that salt from one sample of the plant. An Indian plant (_Hydnocarpus inebrians_) also contains a cyanide, and has been used for the purpose of destroying fish. Among the Tiliads, Greshoff found that _Echinocarpus Sigun_ yielded hydrocyanic acid on distillation. Even the common linseed contains a glucoside which breaks up into sugar, prussic acid, and a ketone.

[237] M. Greshoff--_Erster Bericht über die Untersuchung von Pflanzenstoffen Niederländisch-Indiens. Mittheilungen aus dem chemisch-pharmakologischen Laboratorium des botan. Gartens des Staates_, vii., Batavia, 1890, Niederländisch. Dr. Greshoff’s research indicates that there are several other cyanide-yielding plants than those mentioned in the text.

The following plants, with many others, all yield, by appropriate treatment, more or less prussic acid:--Bitter almonds (_Amygdalus communis_); the _Amygdalus persica_; the cherry laurel (_Prunus laurocerasus_); the kernels of the plum (_Prunus domestica_); the bark, leaves, flowers, and fruit of the wild service-tree (_Prunus padus_); the kernels of the common cherry and the apple; the leaves of the _Prunus capricida_; the bark of the _Pr. virginiana_; the flowers and kernels of the _Pr. spinosa_; the leaves of the _Cerasus acida_; the bark and almost all parts of the _Sorbus aucuparia_, _S. hybrida_, and _S. torminalis_; the young twigs of the _Cratægus oxyacantha_; the leaves and partly also the flowers of the shrubby _Spiræaceæ_, such as _Spiræa aruncus_, _S. sorbifolia_, and _S. japonica_;[238] together with the roots of the bitter and sweet _Cassava_.

[238] The bark and green parts of the _Prunus avium_, L., _Prunus mahaleb_, L., and herbaceous _Spirææ_ yield no prussic acid.

In only a few of these, however, has the exact amount of either prussic acid or amygdalin been determined; 1 grm. of bitter almond pulp is about equal to 2½ mgrms. of anhydrous prussic acid. The kernels from the stones of the cherry, according to Geiseler, yield 3 per cent. of amygdalin; therefore, 1 grm. equals 1·7 mgrm. of HCN.

§ 254. The wild service-tree (_Prunus padus_) and the cherry-laurel (_Prunus Laurocerasus_) contain, not amygdalin but a compound of amygdalin with amygdalic acid; to this has been given the name of laurocerasin. It was formerly known as amorphous amygdalin; its formula is C₄₀H₅₅NO₂₄; 933 parts are equivalent to 27 of hydric cyanide--that is, 100 parts equal to 2·89.

In the bark of the service-tree, Lehmann found ·7 per cent. of laurocerasin (= ·02 HCN), and in the leaves of the cherry-laurel 1·38 per cent. (= 0·39 HCN).

Francis,[239] in a research on the prussic acid in cassava root, gives as the mean in the sweet cassava ·0168 per cent., in the bitter ·0275 per cent., the maximum in each being respectively ·0238 per cent., and ·0442 per cent. The bitter-fresh cassava root has long been known as a very dangerous poison; but the sweet has hitherto been considered harmless, although it is evident that it also contains a considerable quantity of prussic acid.

[239] “On Prussic Acid from Cassava,” _Analyst_, April 1877, p. 5.

The kernels of the peach contain about 2·85 per cent. amygdalin (= ·17 HCN); those of the plum ·96 per cent. (= ·056 HCN); and apple pips ·6 per cent. (= ·035 per cent. HCN).

It is of great practical value to know, even approximately, the quantity of prussic acid contained in various fruits, since it has been adopted as a defence in criminal cases that the deceased was poisoned by prussic acid developed in substances eaten.

§ 255. =Statistics.=--Poisoning by the cyanides (prussic acid or cyanide of potassium) occupies the third place among poisons in order of frequency in this country, and accounts for about 40 deaths annually.

In the ten years ending 1892 there were recorded no less than 395 cases of accidental, suicidal, or homicidal poisoning by prussic acid and potassic cyanide. The further statistical details may be gathered from the following tables:--

DEATHS IN ENGLAND AND WALES DURING THE TEN YEARS 1883-1892 FROM PRUSSIC ACID AND POTASSIC CYANIDE.

PRUSSIC ACID (ACCIDENT OR NEGLIGENCE).

Ages, 0-1 1-5 5-15 15-25 25-65 65 and Total
above
Males, ... 1 1 1 12 1 16
Females, 1 1 ... 2 7 ... 11
--------------------------------------------
Totals, 1 2 1 3 19 1 27
--------------------------------------------

CYANIDE OF POTASSIUM (ACCIDENT OR NEGLIGENCE).

Ages, 1-5 5-15 15-25 25-65 65 and Total
above
Males, 1 1 4 1 ... 7
Females, 1 ... ... 3 ... 4
---------------------------------------
Totals, 2 1 4 4 ... 11
---------------------------------------

PRUSSIC ACID (SUICIDE).

Ages, 15-25 25-65 65 and Total
above
Males, 23 156 23 202
Females, 5 13 1 19
----------------------------
Totals, 28 169 24 221
----------------------------

POTASSIUM CYANIDE (SUICIDE).

Ages, 5-15 15-25 25-65 65 and Total
above
Males, 1 6 88 5 100
Females, ... 6 15 1 22
----------------------------------
Totals, 1 12 103 6 122
----------------------------------

To these figures must be added 10 cases of murder (2 males and 8 females) by prussic acid, and 4 cases of murder (3 males and 1 female) by potassic cyanide.

In order to ascertain the proportion in which the various forms of commercial cyanides cause death, and also the proportion of accidental, suicidal, and criminal deaths from the same cause, Falck collated twelve years of statistics from medical literature with the following result:--

In 51 cases of cyanide poisoning, 29 were caused by potassic cyanide, 9 by hydric cyanide, 5 by oil of bitter almonds, 3 by peach stones (these 3 were children, and are classed as “domestic,” that is, taking the kernels as a food), 3 by bitter almonds (1 of the 3 suicidal and followed by death, the other 2 “domestic”), 1 by tartaric acid and potassic cyanide (a suicidal case, an apothecary), and 1 by ferro-cyanide of potassium and tartaric acid. Of the 43 cases first mentioned, 21 were suicidal, 7 criminal, 8 domestic, and 7 medicinal; the 43 patients were 24 men, 14 children, and 5 women.

The cyanides are very rarely used for the purpose of murder: a poison which has a strong smell and a perceptible taste, and which also kills with a rapidity only equalled by deadly bullet or knife-wounds, betrays its presence with too many circumstances of a tragic character to find favour in the dark and secret schemes of those who desire to take life by poison. In 793 poisoning cases of a criminal character in France, 4 only were by the cyanides.

Hydric and potassic cyanides were once the favourite means of self-destruction employed by suicidal photographers, chemists, scientific medical men, and others in positions where such means are always at hand; but, of late years, the popular knowledge of poisons has increased, and self-poisoning by the cyanides scarcely belongs to a particular class. A fair proportion of the deaths are also due to accident or unfortunate mistakes, and a still smaller number to the immoderate or improper use of cyanide-containing vegetable products.

§ 256. =Accidental and Criminal Poisoning by Prussic Acid.=--The poison is almost always taken by the mouth into the stomach, but occasionally in other ways--such, for example, as in the case of the illustrious chemist, Scheele, who died from inhalation of the vapour of the acid which he himself discovered, owing to the breaking of a flask. There is also the case related by Tardieu, in which cyanide of potassium was introduced under the nails; and that mentioned by Carrière,[240] in which a woman gave herself, with suicidal intent, an enema containing cyanide of potassium. It has been shown by experiments, in which every care was taken to render it impossible for the fumes to be inhaled, that hydrocyanic acid applied to the eye of warm-blooded animals may destroy life in a few minutes.[241]

[240] “_Empoisonnement par le cyanure de potassium,--guérison_,” _Bullet. général de Thérap._, 1869, No. 30.

[241] N. Gréhant, _Compt. rend. Soc. Biol._ [9], xi. 64, 65.

With regard to errors in dispensing, the most tragic case on record is that related by Arnold:[242]--A pharmaceutist had put in a mixture for a child potassic cyanide instead of potassic chlorate, and the child died after the first dose: the chemist, however, convinced that he had made no mistake, to show the harmlessness of the preparation, drank some of it, and there and then died; while Dr. Arnold himself, incautiously tasting the draught, fell insensible, and was unconscious for six hours.

[242] Arnold, A. B., “Case of Poisoning by the Cyanide of Potassium,” _Amer. Journ. of Med. Scien._, 1869.

§ 257. =Fatal Dose.=--Notwithstanding the great number of persons who in every civilised country fall victims to the cyanides, it is yet somewhat doubtful what is the minimum dose likely to kill an adult healthy man. The explanation of this uncertainty is to be sought mainly in the varying strength of commercial prussic acid, which varies from 1·5 (Schraeder’s) to 50 per cent. (Robiquet’s), and also in the varying condition of the person taking the poison, more especially whether the stomach be full or empty. In by far the greater number, the dose taken has been much beyond that necessary to produce death, but this observation is true of most poisonings.

The dictum of Taylor, that a quantity of commercial prussic acid, equivalent to 1 English grain (65 mgrm.) of the anhydrous acid, would, under ordinary circumstances, be sufficient to destroy adult life, has been generally accepted by all toxicologists. The minimum lethal dose of potassic cyanide is similarly put at 2·41 grains (·157 grm.). As to bitter almonds, if it be considered that as a mean they contain 2·5 per cent. of amygdalin, then it would take 45 grms., or about 80 almonds, to produce a lethal dose for an adult; with children less--in fact, 4 to 6 bitter almonds are said to have produced poisoning in a child.

§ 258. =Action of Hydric and Potassic Cyanides on Living Organisms.=--Both hydric cyanide and potassic cyanide are poisonous to all living forms, vegetable or animal, with the exception of certain fungi. The cold-blooded animals take a larger relative dose than the warm-blooded, and the mammalia are somewhat more sensitive to the poisonous action of the cyanides than birds; but all are destroyed in a very similar manner, and without any essential difference of action. The symptoms produced by hydric and potassic cyanide are identical, and, as regards general symptoms, what is true as to the one is also true as to the other. There is, however, one important difference in the action of these two substances, if the mere local action is considered, for potassic cyanide is very alkaline, possessing even caustic properties. I have seen, _e.g._, the gastric mucous membrane of a woman, who had taken an excessive dose of potassic cyanide on an empty stomach, so inflamed and swollen, that its state was similar to that induced by a moderate quantity of solution of potash. On the other hand, the acid properties of hydric cyanide are very feeble, and its effect on mucous membranes or the skin in no way resembles that of the mineral acids.

It attacks the animal system in two ways: the one, a profound interference with the ordinary metabolic changes; the other, a paralysis of the nervous centres. Schönbein discovered that it affected the blood corpuscles in a peculiar way; normal blood decomposes with great ease hydrogen peroxide into oxygen and water. If to normal venous blood a little peroxide of hydrogen be added, the blood at once becomes bright red; but if a trace of prussic acid be present, it is of a dark brown colour. The blood corpuscles, therefore, lose their power of conveying oxygen to all parts of the system, and the phenomena of asphyxia are produced. Geppert[243] has proved that this is really the case by showing, in a series of researches, that, under the action of hydric cyanide, less oxygen is taken up, and less carbon dioxide formed than normal, even if the percentage of oxygen in the atmosphere breathed is artificially increased. The deficiency of oxygen is in part due to the fact that substances like lactic acid, the products of incomplete combustion, are formed instead of CO₂.

[243] Geppert, _Ueber das Wesen der CNH-Vergift; mit einer Tafel_, Berlin, 1889; _Sep.-Abdr. aus Ztschr. f. klin. Med._, Bd. xv.

At the same time the protoplasm of the tissues is paralysed, and unable to take up the loosely bound oxygen presented. This explains a striking symptom which has been noticed by many observers, that is, if hydrocyanic acid be injected into an animal, the venous blood becomes of a bright red colour; in warm-blooded animals this bright colour is transitory, but in cold-blooded animals, in which the oxidation process is slower, the blood remains bright red.

§ 259. =Symptoms observed in Animals.=--The main differences between the symptoms induced in cold-blooded and warm-blooded animals, by a fatal dose of hydric cyanide, are as follows:--

The respiration in frogs is at first somewhat dyspnœic, then much slowed, and at length it ceases. The heart, at first slowed, later contracts irregularly, and at length gradually stops; but it may continue to beat for several minutes after the respiration has ceased. But all these progressive symptoms are without convulsion. Among warm-blooded animals, on the contrary, convulsions are constant, and the sequence of the symptoms appears to be--dyspnœa, slowing of the pulse, giddiness, falling down, then convulsions with expulsion of the urine and fæces; dilatation of the pupils, exophthalmus, and finally cessation of the pulse and breathing. The convulsions also frequently pass into general paralysis, with loss of reflex movements, weak, infrequent breathing, irregular, quick, and very frequent pulse, and considerable diminution of temperature.

The commencement of the symptoms in animals is extremely rapid, the rapidity varying according to the dose and the concentration of the acid. It was formerly thought that the death from a large dose of the concentrated acid followed far more quickly than could be accounted for by the blood carrying the poison to the nervous centres; but Blake was among the first to point out that this doubt was not supported by facts carefully observed, since there is always a sufficient interval between the entry of the poison into the body and the first symptoms, to support the theory that the poison is absorbed in the usual manner. Even when Preyer injected a cubic centimetre of 60 per cent. acid into the jugular vein of a rabbit, twenty-nine seconds elapsed before the symptoms commenced. Besides, we have direct experiments showing that the acid--when applied to wounds in limbs, the vessels of which are tied, while the free nervous communication is left open--only acts when the ligature is removed. Magendie describes, in his usual graphic manner, how he killed a dog by injecting into the jugular vein prussic acid, and “_the dog died instantly, as if struck by a cannon ball_,” but it is probable that the interval of time was not accurately noted. A few seconds pass very rapidly, and might be occupied even by slowly pressing the piston of the syringe down, and in the absence of accurate measurements, it is surprising how comparatively long intervals of time are unconsciously shortened by the mind. In any case, this observation by Magendie has not been confirmed by the accurate tests of the more recent experimenters; and it is universally acknowledged that, although with strong doses of hydric cyanide injected into the circulation--or, in other words, introduced into the system--in the most favourable conditions for its speediest action, death occurs with appalling suddenness, yet that it takes a time sufficiently long to admit of explanation in the manner suggested. This has forensic importance, which will be again alluded to. Experiments on animals show that a large dose of a dilute acid kills quite as quickly as an equivalent dose of a stronger acid, and in some cases it even seems to act more rapidly. If the death does not take place within a few minutes, life may be prolonged for hours, and even, in rare cases, days, and yet the result be death. Coullon poisoned a dog with prussic acid; it lived for nineteen days, and then died; but this is quite an exceptional case, and when the fatal issue is prolonged beyond an hour, the chance of recovery is considerable.

§ 260. The length of time dogs poisoned by fatal doses survive, generally varies from two to fifteen minutes. The symptoms are convulsions, insensibility of the cornea, cessation of respiration, and, finally, the heart stops--the heart continuing to beat several minutes after the cessation of the respirations.[244] When the dose is short of a fatal one, the symptoms are as follows:--Evident giddiness and distress; the tongue is protruded, the breath is taken in short, hurried gasps, there is salivation, and convulsions rapidly set in, preceded, it may be, by a cry. The convulsions pass into paralysis and insensibility. After remaining in this state some time, the animal again wakes up, as it were, very often howls, and is again convulsed; finally, it sinks into a deep sleep, and wakes up well.

[244] N. Gréhant, _Compt. rend._, t. 109, pp. 502, 503.

Preyer noticed a striking difference in the symptoms after section of the vagus in animals, which varied according to whether the poison was administered by the lungs, or subcutaneously. In the first case, if the dose is small, the respirations are diminished in frequency; then this is followed by normal breathing; if the dose is larger, there is an increase in the frequency of the respirations. Lastly, if a very large quantity is introduced into the lungs, death quickly follows, with respirations diminished in frequency. On the other hand, when the poison is injected subcutaneously, small doses have no influence on the breathing; but with large doses, there is an increase in the frequency of the respirations, which sink again below the normal standard.

§ 261. =Symptoms in Man.=--When a fatal but not excessive dose of either potassic or hydric cyanide is taken, the sequence of symptoms is as follows:--Salivation, with a feeling of constriction in the throat, nausea, and occasionally vomiting. After a few minutes a peculiar constricting pain in the chest is felt, and the breathing is distinctly affected. Giddiness and confusion of sight rapidly set in, and the person falls to the ground in convulsions similar to those of epilepsy. The convulsions are either general, or attacking only certain groups of muscles; there is often true trismus, and the jaws are so firmly closed that nothing will part them. The respiration is peculiar, the inspiration is short, the expiration prolonged,[245] and between the two there is a long interval ever becoming more protracted as death is imminent. The skin is pale, or blue, or greyish-blue; the eyes are glassy and staring, with dilated pupils; the mouth is covered with foam, and the breath smells of the poison; the pulse, at first quick and small, sinks in a little while in frequency, and at length cannot be felt. Involuntary evacuation of fæces, urine, and semen is often observed, and occasionally there has been vomiting, and a portion of the vomit has been aspirated into the air-passages. Finally, the convulsions pass into paralysis, abolition of reflex sensibility, and gradual ceasing of the respiration. With large doses these different stages may occur, but the course is so rapid that they are merged the one into the other, and are undistinguishable. The shortest time between the taking of the acid and the commencement of the symptoms may be put at about ten seconds. If, however, a large amount of the vapour is inhaled at once, this period may be rather lessened. The interval of time is so short that any witnesses generally unintentionally exaggerate, and aver that the effects were witnessed _before_ the swallowing of the liquid--“As the cup was at his lips”--“He had hardly drunk it,” &c. There is probably a short interval of consciousness, then come giddiness, and, it may be, a cry for assistance; and lastly, there is a falling down in convulsions, and a speedy death. Convulsions are not always present, the victim occasionally appears to sink lifeless at once. Thus, in a case related by Hufeland, a man was seen to swallow a quantity of acid, equivalent to 40 grains of the pure acid--that is, about forty times more than sufficient to kill him. He staggered a few paces, and then fell dead, without sound or convulsion.

[245] In a case quoted by Seidel (Maschka’s _Handbuch_, p. 321), a man, 36 years of age, four or five minutes after swallowing 150 mgrms. anhydrous HCN in spirits, lay apparently lifeless, without pulse or breathing. After a few minutes was noticed an extraordinary deep expiration, by which the ribs were drawn in almost to the spine, and the chest made quite hollow.

§ 262. The very short interval that may thus intervene between the taking of a dose of prussic acid and loss of consciousness, may be utilised by the sufferer in doing various acts, and thus this interval becomes of immense medico-legal importance. The question is simply this:--What can be done by a person in full possession of his faculties in ten seconds? I have found from experiment that, after drinking a liquid from a bottle, the bottle may be corked, the individual can get into bed, and arrange the bedclothes in a suitable manner; he may also throw the bottle away, or out of the window; and, indeed, with practice, in that short time a number of rapid and complicated acts may be performed. This is borne out both by experiments on animals and by recorded cases.

In Mr. Nunneley’s numerous experiments on dogs, one of the animals, after taking poison, “went down three or four steps of the stairs, saw that the door at the bottom was closed, and came back again.” A second went down, came up, and went again down the steps of a long winding staircase, and a third retained sufficient vigour to jump over another dog, and then leap across the top of a staircase.

In a remarkable case related by Dr. Guy,[246] in which a young man, after drinking more wine than usual, was seized by a sudden impulse to take prussic acid, and drank about 2 drachms, producing symptoms which, had it not been for prompt treatment, would, in all probability, have ended fatally--the interval is again noteworthy. After taking the poison in bed, he rose, walked round the foot of a chest of drawers, standing within a few yards of the bedside, placed the stopper firmly in the bottle, and then walked back to bed with the intention of getting into it; but here a giddiness seized him, and he sat down on the edge, and became insensible.

[246] _Forensic Medicine_, 4th ed., p. 615.

A case related by Taylor is still stronger. A woman, after swallowing a fatal dose of essence of almonds, went to a well in the yard, drew water, and drank a considerable quantity. She then ascended two flights of stairs and called her child, again descended a flight of stairs, fell on her bed, and died within half an hour from the taking of the poison.

Nevertheless, these cases and similar ones are exceptional, and only show what is possible, not what is usual, the rule being that after fatal doses no voluntary act of significance--save, it may be, a cry for assistance--is performed.[247]

[247] Dr. J. Autal, a Hungarian chemist, states that cobalt nitrate is an efficacious antidote to poisoning by either HCN or KCN. The brief interval between the taking of a fatal dose and death can, however, be rarely utilised.--_Lancet_, Jan. 16, 1894.

§ 263. =Chronic poisoning by hydric cyanide= is said to occur among photographers, gilders, and those who are engaged daily in the preparation or handling of either hydric or potassic cyanides. The symptoms are those of feeble poisoning, headache, giddiness, noises in the ears, difficult respiration, pain over the heart, a feeling of constriction in the throat, loss of appetite, nausea, obstinate constipation, full pulse, with pallor and offensive breath. Koritschoner[248] has made some observations on patients who were made to breathe at intervals, during many weeks, prussic acid vapour, with the idea that such a treatment would destroy the tubercle bacilli. Twenty-five per cent. of those treated in this way suffered from redness of the pharynx, salivation, headache, nausea, vomiting, slow pulse, and even albuminuria.

[248] _Wiener klin. Woch._, 1891.

§ 264. =Post-mortem Appearances.=[249]--If we for the moment leave out of consideration any changes which may be seen in the stomach after doses of potassic cyanide, then it may be affirmed that the pathological changes produced by hydric and potassic cyanides mainly coincide with those produced by suffocation. The most striking appearance is the presence of bright red spots; these bright red spots or patches are confined to the surface of the body, the blood in the deeper parts being of the ordinary venous hue, unless, indeed, an enormous dose has been taken; in that case the whole mass of blood may be bright red; this bright colour is due, according to Kobert, to the formation of cyanmethæmoglobin. The lungs and right heart are full of blood, and there is a backward engorgement produced by the pulmonic block. The veins of the neck and the vessels of the head generally are full of blood, and, in like manner, the liver and kidneys are congested. In the mucous membrane of the bronchial tubes there is a bloody foam, the lungs are gorged, and often œdematous in portions; ecchymoses are seen in the pleura and other serous membranes; and everywhere, unless concealed by putrefaction, or some strong-smelling ethereal oil, there is an odour of hydric cyanide.

[249] Hydric cyanide has, according to C. Brame, a remarkable antiseptic action, and if administered in sufficient quantity to animals, preserves them after death for a month. He considers that there is some more or less definite combination with the tissues.