194

HYDROCYANIC OR PRUSSIC ACID.

PRUSSIC ACID.-SYMPTOMS

CHAPTER XVII.

FOR

AND APPEARANCES.-TESTS FOR THE ACID.-PROCESS ORGANIC MIXTURES.-CYANIDE OF POTASSIUM.-ESSENTIAL OIL OF BITTER ALMONDS.

NITROBENZENE.-NITROGLYCERINE.

HYDROCYANIC OR PRUSSIC ACID.

Symptoms. The solutions of this acid have a hot, bitter taste and an odor resembling that of bitter almonds. The time at which the symptoms of poisoning commence varies, but it is generally very shortly after the poison has been swallowed. When a large dose has been taken, as from half an ounce to an ounce of the diluted acid (two to four per cent.), the symptoms usually commence in the act of swallowing, or within a few seconds. It is stated that a diluted is more rapidly absorbed than a stronger acid. It is rare that the appearance of symptoms is delayed beyond one or two minutes. When the patient has been seen at this period, he has been quite insensible, the eyes fixed and glistening, the pupils dilated and unaffected by light, the limbs flaccid, the skin cold and covered with a clammy perspiration; there is convulsive breathing at long intervals, and the patient appears dead in the intermediate period; the pulse is imperceptible, and involuntary evacuations are occasionally passed. The respiration is slow, deep, gasping, occasionally heaving or sobbing, and is generally convulsive; but when the coma or insensibility is profound, it may be stertorous. This was observed in a case which occurred to Christison. (Edin. Month. Jour., Feb. 1850, p. 97.) Convulsions of the limbs and body, with a spasmodic closure of the jaw, are sometimes noticed among the symptoms.

The following cases present fair examples of the immediate effects of this poison in a large and fatal dose. A medical man swallowed seven drachms of the common prussic acid. He survived about four or five minutes. About two minutes after he had taken the poison he was found lying on the floor senseless; there were no convulsions of the limbs or trunk, but a faint flickering motion was observed about the muscles of the lips. The breathing appeared to cease entirely for some seconds; it was then performed in convulsive fits, and the act of expiration was remarkably deep, and lasted for an unusual time. When the dose is large the breath commonly exhales a strong odor of the acid, and this is also perceptible in the room.

A medical student took a drachm and a half of Scheele's prussic acid (strength about four per cent.). He was heard to call out once or twice, and a gentleman sleeping in the next room ran to his assistance. He was heard to fall from the sofa to the floor, and when picked up was found to be already insensible. Hilton Fagge saw him a little later-fifteen to thirty minutes after the poison was taken. He was then lying on a sofa, quite insensible. The limbs were paralyzed, and lay in any position in which they were placed; and they were free from all rigidity. The jaws were clenched. The pupils were normal. There were no convulsions, nor had there been any. The face was not livid. The pulse was very rapid, the respirations very infrequent. Cold water dashed on the face produced at each application deep respiratory efforts. An attempt to

APPEARANCES-ANALYSIS.

195

administer an emetic failed, in consequence of inability to swallow. Strong ammonia applied to the nostrils failed to produce the slightest stimulation. After a time the breathing became slower-seven respirations in a minute-and it was distinctly stertorous. The pulse became slower and markedly feebler; and now cold affusion failed to produce any effect. The respirations fell to four in a minute, the face became blue, and the pulse imperceptible at the wrist. Breathing ceased in from an hour to an hour and a half after the poison was swallowed. There was a marked odor of prussic acid in the room; but it was not noticed at first whether the breath smelt of the acid. (Guy's Hosp. Rep., 1869, p. 259.) Appearances.-The body when seen soon after death often exhales the odor of prussic acid; but if it has remained exposed before it is seen, and if it has been exposed to the open air or in a shower of rain, the odor may not be perceptible; again, the odor may be concealed by tobacco smoke, peppermint, copaiba, or other powerful odors. Externally, the skin is commonly livid, or is tinged of a violet color; the nails are blue, the fingers clenched, and the toes contracted; the jaws firmly closed, with foam or froth about the mouth, the face often pale, but sometimes bloated and swollen, and the eyes have been observed to be wide open, fixed, glassy, very prominent and glistening, with the pupils dilated; but a similar condition of the eyes has been observed in other kinds of violent death. Internally, the venous system is gorged with dark-colored liquid blood; the stomach and intestines may be in their natural state; but in several instances they have been found more or less congested. The mucous membrane of the stomach may be intensely reddened throughout. The smallest dose of this acid which is reported to have caused death was in the case of a healthy adult woman, who died in twenty minutes from a dose equivalent to nine-tenths of a grain of anhydrous prussic acid. (Med. Gaz., vol. 35, p. 896.) This corresponds to about fortyfive minims of the B. P. acid. In a case reported by T. Taylor (Med. Gaz., vol. 36, p. 104), a stout healthy man swallowed this dose, i e. ninetenths of a grain, by mistake, and remained insensible for four hours, when he vomited and began to recover. From the facts hitherto observed, we shall not be wrong in assuming that a quantity of B. P. acid (at two per cent.) above fifty minims (i.e. one grain of anhydrous acid), or an equivalent proportion of any other acid, would commonly suffice to destroy the life of an adult. This is the nearest approach that we can make to the smallest fatal dose.

When a dose of half an ounce and upwards of the B. P. acid has been taken, we may probably take the average period for death at from two to ten minutes. In Hick's case, twenty grains of Scheele's acid (containing five per cent.) destroyed life in twenty minutes. It is only when a dose is just in a fatal proportion that we find a person to survive from half an hour to an hour. In this respect, death by prussic acid is like death by lightning-the person in general either dies speedily or he recovers altogether. Before the access of insensibility the person often possesses a wonderful power of exertion and locomotion, perhaps in a state of halfconsciousness. Thus he may be able to cork and conceal the bottle from which he has swallowed the poison; or he may run several yards before falling. Due allowance must be made for the performance of these voluntary acts. (See Brit. Med. Jour., 1887, i. p. 11.)

Chemical Analysis. Two solutions of prussic acid are met with in British commerce-the British pharmacopoeial acid (B. P.' acid), containing two per cent. of the acid, and the so-called Scheele's acid, a stronger preparation containing about four per cent. These solutions are limpid

196

TESTS FOR PRUSSIC ACID.

like water, possess a faint acid reaction, and the vapor has a peculiar odor, which, when the acid is concentrated, although not at first perceptible, is sufficient to produce giddiness, insensibility, and other alarming symptoms. The tests which are best adapted for the detection of this poison, either in liquid or vapor, are equally applicable whether the acid is concentrated or diluted, and, so far as the detection of the vapor is concerned, whether the acid is pure or mixed with other liquids. In the simple state, the tests are three in number-the Silver, the Iron, and the Sulphur tests. 1. The Silver-Test. Nitrate of Silver.-This, added in excess, yields with prussic acid a dense white precipitate, speedily subsiding in heavy clots to the bottom of the vessel, and leaving the liquid almost clear. The precipitate is identified as cyanide of silver by the following properties: a. It is insoluble in cold nitric acid; but when drained of water, and a sufficient quantity of the strong acid is added, it is easily dissolved on boiling. b. It evolves prussic acid when digested in hydrochloric acid. c. The precipitate, when well dried, and heated in a small reduction-tube, yields cyanogen, which may be burnt as it issues, producing a rose-red flame with a blue halo. This is a well-marked character, and at once identifies the acid which yielded the precipitate as prussic acid. Five grains by weight of the dry precipitate correspond to one grain of anhydrous prussic acid, to twenty-five grains of Scheele's acid, and fifty grains of the British pharmacopoeial acid.

For the detection of prussic acid in vapor, hold over the liquid a watchglass moistened in the centre with a drop of a solution of nitrate of silver. Cyanide of silver, indicated by the formation of an opaque white film in the solution, is immediately produced, if the acid is only in a moderate state of concentration. One drop of a diluted acid containing less than 1-50th of a grain of the anhydrous acid produces speedily a visible effect When the prussic acid is more diluted, a few minutes are required; and the opaque film begins to show itself at the edges of the silver solution. In this case the action may be accelerated by the heat of the hand applied

Fig. 21.

Crystals of Cyanide of Silver from the vapor of prussic acid, magnified 24 diameters.

to the vessel. If the vapor is allowed to reach the nitrate of silver gradually and much diluted with air, then instead of an opaque film of cyanide of silver, crystals well defined under the microscope will be slowly produced, and these will constitute an additional proof of the presence of the acid in a state of vapor. As shown in the illustration (Fig. 21), these crystals have the form of slender prisms with oblique terminations. They often hang together in groups, and generally require a high magnifying power to render them visible.

2. The Iron-Test.-The object of the ap plication of this test is the production of Prussian blue. Add to a small quantity of the suspected poisonous liquid a few drops of a solution of ferrous sulphate and a little solution of potash. A dirty-green or brownish precipitate falls; on shaking this with air for a few minutes, and then adding diluted hydrochloric or sulphuric acid, the liquid becomes blue; and Prussian blue, of its well-known color, unaffected by diluted acids, slowly subsides.

3. The Sulphur-Test. A small quantity of yellow sulphide of ammonium is added to a few drops of a solution of prussic acid, and the mixture is gently warmed; it becomes colorless, and, on evaporation,

PRUSSIC ACID IN ORGANIC LIQUIDS.

197 leaves crystals of sulphocyanide of ammonium-the sulphocyanide being indicated by the intense blood-red color produced on adding to the dry residue a solution of nearly neutral persalt of iron; this red color immediately disappears on adding a few drops of a solution of corrosive sublimate.

The great utility of the sulphur-test, however, is in its application to the detection of the minutest portion of prussic acid when in a state of vapor. In this respect it surpasses in delicacy any other process yet discovered. In order to apply it, we place the diluted prussic acid in a watch-glass, and invert over it another watch-glass having in its centre one drop of yellow sulphide of ammonium. No change apparently takes place in the sulphide; but if the upper watch-glass is removed after the lapse of from half a minute to ten minutes, according to the quantity and strength of the prussic acid present, crystallized sulphocyanide of ammonium will be obtained on gently evaporating the drop of liquid to dryness. With an acid of from three to five per cent. the action is completed in ten seconds. The addition of one drop of neutral ferric sulphate or chloride (free from nitric acid) to the dried residue brings out the blood-red color instantly, which is intense in proportion to the quantity of sulphocyanide present. (For some remarks on the application of this process to the detection of prussic acid, see Med. Gaz., 1847, vol. 39, p. 765.)

The

Prussic Acid in organic liquids. Detection by vapor without distillation. The organic liquid may be placed in a short, wide-mouthed bottle, to which a watch-glass has been previously fitted as a cover. The capacity of the bottle may be such as to allow the surface of the liquid to be within one or two inches of the concave surface of the watch-glass. solution of Nitrate of silver is then used as a trial-test for the vapor in the manner above described. If the 1-200th of a grain of prussic acid is present, and not too largely diluted, it will be detected (at a temperature of 60° F.) by the drop of nitrate of silver being converted into an opaque white or crystalline film of cyanide of silver, the chemical change commencing at the margin. We may then substitute yellow sulphide of ammonium for the nitrate of silver, and proceed in the manner above described. In cold weather it may be necessary to place the bottle in a basin of warm water. If the solution of silver is tarnished by sulphuretted hydrogen, as a result of putrefaction, the sulphur-test alone should be used. By this process prussic acid has been detected in the stomach as late as twelve days after death of a person poisoned by it. After the stomach has been exposed for a few days longer, the acid has entirely disappeared.

If traces of the poison are thus found, then the organic liquid should be acidulated and distilled in a water-bath, and about one-fourth of the contents of the flask collected in a receiver kept cool by water. (For the form of apparatus see p. 135, ante.) The tests may now be applied to the distilled liquid, which will have the odor of prussic acid.

[Care should be used in the search by distillation not to employ sulphuric acid, because this acid will decompose the sulphocyanide existing in the saliva likely to be found in the stomach, and thereby evolve traces of prussic acid.

This point was made in the celebrated case of Paul Schoeppe, tried at Carlisle, Pa. The analyst found faint traces of prussic acid by distillation in which sulphuric acid had been used: Reese, 8th Amer. Ed. of Taylor's Med. Jurisprudence, Phila., 1880, p. 212; vide also Wharton & Stillé, Med. Jur., 1873, p. 515.]

198

CYANIDE OF POTASSIUM.

In the tissues.-Soon after death the poison may be easily detected in the blood, secretions, or any of the soft organs, by placing them in a bottle and collecting the vapor in the manner already described. This will be found more convenient and satisfactory than the process by distillation. The poison has been thus discovered, in experiments on animals, in the blood and even in the exhalation from the chest.

If the body is in a putrefied state, the residuary prussic acid may have been converted into fixed sulphocyanide of ammonium. In order to detect this salt in the stomach or its contents, we should digest the parts finely cut up in hot alcohol, filter the alcoholic liquid, evaporate to dryness, and take up any crystalline residue with water. A solution of a persalt of iron added to this solution will indicate the presence of a sulphocyanide by imparting to it an intensely red color. The editor has detected prussic acid as a sulphocyanide in the blood many weeks after the death of a person who died from prussic-acid poisoning.

CYANIDE OF POTASSIUM.

Symptoms. This salt has a bitter taste, producing first a sense of coldness on the tongue, followed by a feeling of constriction and burning heat in the throat. It is one of the most formidable poisons known to chemists. It has destroyed life in a quarter of an hour. A dose of five grains has proved fatal in three instances. In one case the person died in two hours. (Chem. News, Sept. 5, 1863.) The symptoms which the cyanide produces are similar to those occasioned by prussic acid-insensibility. spasmodic respiration, convulsions, with tetanic stiffness of the jaws and body. They appear in a few seconds or minutes, and run through their course with great rapidity.

Appearances. In a case in which an inspection of the body was made two days after death, there was no remarkable odor: the muscles were rigid; the face and forepart of the trunk pale; the back livid, except those portions which had sustained pressure. The fingers and toes were convulsively bent inwards, the nails blue, the eyelids half closed, the lips pale, the vessels of the brain filled with bluish-red blood. On making a section of the brain and spinal marrow, numerous bloody points were observed. The lungs were congested posteriorly, and, on cutting into them, a strong odor of bitter almonds was perceived. A yellowish mucus was found in the stomach, which yielded on analysis cyanide of potassium. The mucous membrane was reddened near the intestinal end. The poison was not detected in any part of the body except the contents of the stomach and intestines. (Casper's Wochenschrift, Oct. 4, 1845, 657.) The stomach is sometimes intensely reddened.

Cyanide of potassium has a local chemical action upon the skin; and if this is abraded or wounded it may be absorbed and produce serious effects. Some accidents of this kind have occurred in the practice of photography. (Ann. d'Hyg., 1863, vol. i. p. 454.)

Analysis. This substance is usually seen in hard white masses. It is deliquescent and very soluble in water; the solution, when pure, is colorless, and has a strong alkaline reaction, a soapy feel, and a powerful odor of prussic acid. It is not very soluble in cold alcohol. 1. It is decomposed by all acids, and prussic acid is set free. 2. The potassium is precipitated by tartaric acid and by platinic chloride. 3. It gives a white precipitate with nitrate of silver, which will be found to possess all the properties of cyanide of silver (ante, p. 196). This precipitate is easily redissolved by a slight excess of a solution of cyanide of potassium. 4.