Allen asserts (Commercial Organic Analysis, 1879), that detection in the body is rarely possible more than twenty-four hours after death; but Taylor (Med. Juris., 1873, p. 368) has found it in the stomach twelve days after, saying, however, that “after the stomach had been exposed a few days longer, all had disappeared.” In a dog’s stomach he found it, after twenty-four hours’ exposure, and washing with water. In a human stomach, success was achieved seven days after death, where no odour was perceptible; in another case, after twenty-two days in the stomach, and after two months in the spleen. It may be found in the stomach, and not in the tissues; but in most cases it is easily detected, soon after death, in the blood, organs, &c. The vapour of HCN will traverse paper, wet or dry bladder, &c., in a few minutes (Taylor), and few stoppers are close enough to retain it. Hence care should be taken to shut up the suspected matters at once in glass bottles accurately stoppered; bad stoppers are worse than corks.
The stomach should be first examined entire, to ascertain odour, &c., noticing whether alkaline or acid, then cut in pieces, under distilled water sufficient to cover it, the whole measured, and one-half (acidulated with tartaric acid, if alkaline), placed in a capacious retort, and distilled in a bath of water saturated with salt to raise the boiling point. The condenser should be well supplied with cold water, the receiver attached airtight, with a mercury valve (a narrow glass U-tube, containing mercury), to prevent undue pressure. A little distilled water, about ½ oz., should be placed in the receiver. The distillation should be continued till one-third to one-half of the original liquid has passed over. The tests may then be applied to the distillate.
Allen recommends us to distil with water alone about one-half. If there is no result on testing the distillate, continue with addition of tartaric acid. Finally, add a considerable excess of moderately dilute sulphuric and hydrochloric acid, and carry the distillation nearly to dryness. In the last stage sulpho-, ferro-and ferricyanides and mercuric cyanide are decomposed, and give HCN. The original should be tested for ferrocyanide, &c. This seems a process calculated to give the clearest idea of the form in which the HCN is present, but is open to the objection that it is protracted, and may hence cause loss.
Sokoloff. (Chem. Centr., 1876, 603) advises a much more heroic treatment. “Strongly acidify with sulphuric acid, and distil over a water bath for two or three days, replenishing the water as evaporated. The longer the distillation, the more accurate the result.” He adds, that the muscles contain the greater part of the HCN. He quotes figures in support of his results, but I have not found such prolongation necessary; and we must remember that HCN is decomposed by heating with moderately strong mineral acids.
The following modification, proposed by the author, may be advantageous, as diminishing the risk of loss, and also effecting concentration:—Prepare exactly equivalent solutions of silver nitrate, and hydrochloric acid: the silver solution may contain 17 grammes of silver nitrate, the hydrochloric solution 3·65 grammes of hydric chloride, per litre. Place in the receiver 100 cubic centimetres of the silver solution (= 1·70 gramme silver nitrate) before distillation. This is allowing large excess, to provide for exceptional quantities of HCN. If any quantity of HCN be present, the liquid in the receiver will become milky; if it does not, there cannot be more than a minute trace. Transfer the distillate and washings to a retort, provided with a thistle-funnel, and boil down to one-third of its bulk; then add, through the funnel, 100 cubic centimetres of the hydric chloride solution, which will precipitate all the silver as chloride, and liberate the HCN. Distill with the same precautions as before: the first 25 cubic centimetres will contain probably all the HCN. If doubted, a further quantity may be collected and tested. The 25 cubic centimetres of distillate may now be subjected to the following tests, taking care that each portion is measured before being examined, in order that the idea of the quantity present may be definite. For instance, in the Prussian blue, and sulphocyanide tests, the resulting colour may be imitated by standard solutions: in the silver test, a standard silver solution should also be used, and thus a triply-confirmed knowledge of the quantity present may be attained; and little bottles, containing the results, should be preserved, to show in the courts of justice.
I. Odour.—All tests involving odour are affected seriously by the remarkable differences between different people as to their sense of smell. We hear much of “colour-blindness;” but the analogous olfactory defect has almost escaped remark. Yet “smell-blindness,” as I have formerly christened it, or “anozism,” if a Greek word be required, is exceedingly common, and chemists and medical men are frequently afflicted with it. I have known an artist, who could not smell strong ammonia, yet delighted in the odour of new paint, which he compared to roses. Many laboratory students can neither smell acetic acid, arseniuretted hydrogen, nor cyanogen. An assistant was so fond of sulphuretted hydrogen, that he was once found insensible beside the apparatus, having narcotized himself with the gas (he recovered); and many more such eccentricities. In the case of prussic acid these diversities are enormous. Some are so sensitive, that the least trace in a room becomes rapidly unbearable, causing headache and nausea; others are like photographers, and can work in a heavily-cyanogened atmosphere. Such idiosyncrasies become of great importance in evidence; for example:—
In Tawell’s trial, Mr. Champneys, surgeon, testified as follows: “Have no experience in detecting odour of prussic acid in a human subject. Should think it may be taken without detection. Should expect it in the mouth and breath, but there may be exceptions. There was no odour in her [the deceased’s] breath; but, on opening the body, I was positive I smelt prussic acid. The other two surgeons could not smell it.” Afterwards, when the contents of the stomach were transferred to a jar, neither the three surgeons, nor Mr. Cooper, the analyst, could perceive the least odour of prussic acid, even when the contents were boiled. Nor was it smelt in the blood. Mr. Cooper subsequently stated: “I have no doubt that prussic acid may exist without being smelt: absence of smell may arise from dilution, or from its being covered by the smell of other substances. When I smell it, it affects spasmodically the back of the throat. Sometimes it has produced a spasmodic constriction about the throat without my smelling it.” Here was a well-marked case of intermittent smell-blindness.
There were also several questions as to whether prussic acid might have existed in the form of an inodorous salt. Mr. Champneys further stated that he put ½ drachm of prussic acid into a tumbler filled with Guinness’s porter, and the smell was scarcely perceptible. Mr. Norblad, surgeon, deposed that he mixed 12 grains of prussic acid with a pint of porter, but could not then smell it. “Some of the porter dropped on the table, and I did then smell it.” In the same trial, Henry Thomas, druggist’s assistant, mixed 30 drops of B.P. prussic acid with 11 oz. of porter, and found the odour of the acid slightly perceptible; yet, when he was pouring Scheele’s acid from a bottle, three women had to leave the room to avoid suffocation!
In a case of suicide by cyanide of potassium (Chem. News, 1861, p. 261), the smell of prussic acid was not perceived by the surgeon, either immediately after death or at the post-mortem examination, nor by the analyst until the contents had been distilled with dilute sulphuric acid.