ANTIDOTE.

BY E. J. SHEARMAŃ, M.D., ROTHERHAM.
Read before the Sheffield Medical Society,
March 7, 1844.

Arsenic is a substance so commonly used for criminal purposes, and so little under the control of any chemical substance as an antidote, that it is very desirable to establish some certain mode of detecting and showing it so clearly that medical practitioners may be able to swear, most positively, as to its existence or not. The late trial of Madame Lafarge, in France, although the chemical and physiological parts of it were conducted by some of the first men of the age, terminated in such a manner as to convince most English chemists that the proof of arsenic having existed in the body of Lafarge, was not established in so distinct a manner as would have carried conviction in this country; and, as I took great interest in it whilst it lasted, I was led to attend to the subject.

In order to show the existence of arsenic in a court

of justice in England, we should be enabled to prove the following facts so satisfactorily, that a jury may not only see, but perfectly understand them.

1st. The metal should be produced either from the contents of the stomach, intestines, or urine, if the patient should survive; or, if dead, from those and some part of the body.

2nd. We should be able to prove that the animal substances experimented upon were the excretions, and parts of the patient's body only; unmixed with any other matter.

3rd. We must also prove that the tests we use to show the existence of arsenic have not a particle of arsenic in themselves; and this requires great caution, because a skilful advocate might make a guilty prisoner appear innocent, owing to this omission.

4th. As antimony, bismuth, tin, zinc, lead, tellurium, cadmium, selenium, and potassium, sublime in a somewhat similar manner to arsenic, and may be mistaken for it; it is quite necessary for an inexperienced eye to guard against such a mistake.

It is therefore my intention, in as simple and clear a manner as I possibly can, to endeavour to show that arsenic can be tested from the most minute particle, so clearly that an unscientific person cannot mistake it; and, also, that this can be done easily, without using any chemical substance known to contain arsenic.

The most common and efficacious manner of proceeding, when the contents of the stomach, or a decoction of the stomach, liver, &c., in distilled water, is to be operated upon, is that recommended by Dr. Christison. The first point is to get rid of the animal matter. After boiling for half an hour in distilled water, the solution No. 1, April 3, 1944.

you have obtained a clear solution, animal matter may often be deposited by adding strong acetic acid, which coagulates the casein. Neutralize this acid with potass or ammonia, and then try the sulphuretted hydrogen test. If this does not act, all you have to do is, slowly to evaporate the solution to dryness in a porcelain dish, redissolve it in distilled water, and when cold, filter. This process, several times repeated, eventually gets rid of the whole of the animal matter.

I had an opportunity of proving this a few years since, in the case of a cow belonging to a nobleman in the neighbourhood, which had been evidently poisoned. Mr. Peach, our eminent veterinary surgeon, was called in, who not being willing to give an opinion as to what was the poison, his lordship begged of me to try to ascertain it. At that time the stomach and its contents had been buried a day or two, and I had to pick out any part that appeared inflamed to operate upon. The animal matter in this case was very large, but by attending to the above rules, I obtained a sufficient quantity of arsenic to have convinced, as I then thought, the most sceptical of its presence. I showed the crust I procured to Mr. West, of Leeds, who said there was no substance but arsenic capable of showing that appearance.

When a clear solution is obtained, with but a small portion of animal matter in it, the ammoniacal nitrate of silver gives a lively lemon-yellow precipitate the arsenite of silver. The ammoniacal sulphate of copper gives an apple or grass-green precipitate the arsenite of copper.

And the transmission of sulphuretted hydrogen gas through this solution, previously neu tralized, and then slightly acidulated with acetic acid, throws down an abundant sulphur-yellow precipitatethe sulphuret of arsenic.

solution a few minutes, which drives off the excess of It is the best plan to boil the last precipitate in the sulphuretted hydrogen gas, and allows the whole of the sulphuret of arsenic to deposit. This is to be collected on a filter; dried on a watch glass; introduced into the bottom of a bulbed tube, and covered with black flux, or what is perhaps better, freshly ignited charcoal. The tube is then to be heated by a spirit lamp, first at the part just above where the flux is, and then gradually below, so as to sublime the metallic arsenic all round the tube; which forms a brilliant polished metallic appearance, that cannot be easily mistaken when once seen: and which I once heard given in evidence as the only proof of arsenic in one of our courts of justice :-the fallacy of which opinion I think I shall be able to prove.

The metallic arsensic should afterwards be oxidized by the heat of the spirit lamp and the oxygen of the air, and driven up the tube, so as to allow it to form octohedral crystals of arsenious acid, with triangular facettes.

In estimating the process which I have now

B

described, an English jury would wish to know, before they condemned a fellow creature to death, if there is no other mode of detecting and proving arsenic; and if no other substance gives the same crystals as arsenious acid?

This gap was, in a degree, filled up, by Marsh's hydrogen test; where hydrogen gas is generated from zinc, sulphuric acid and water, and the suspected substance in solution added to it; if arsenic be present, hydrogen has such an affinity for it, that it will combine with the whole of it very quickly. The arsenietted hydrogen being ignited, the metallic arsenic is deposited on porcelain or glass, which can be seen in rhomboidal crystals with a powerful microscope.

The only objection to this test is, that you are obliged to use zinc, which is known often to contain arsenic and, although it shows the most minute portion of arsenic that can possibly be exhibited, yet, how can you swear that, after the first layer of zinc is oxidized, there may not be some arsenic in the next? for we know that arsenic runs in veins of the zinc ore. The next test I would describe is that beautiful one of Professor Reinsch, modified by Christison, which is well suited for detecting arsenic in animal and vegetable substances. Mix the suspected matter with distilled water: add at least two drachms of pure hydrochloric acid to every eight ounces of fluid. Put a few bits of very thin and bright copper plate into it, boil for half an hour, and the arsenic will be gradually deposited on the copper plates. We have here for analysis, animal matter in solution with arsenious acid by heat, hydrochloric acid, water and copper. As far as I can ascertain at present, the following is the result. The water and arsenious acid are both decomposed: the oxygen of the water unites with the copper, forming oxide of copper: the hydrogen of the water unites with the metallic arsenic, forming arsenietted hydrogen, which is decomposed by the oxide of copper-the metallic arsenic of the arsenietted hydrogen forming a coat on the oxide of copper; while the free hydrogen goes to combine with another portion of the oxygen of the arsenious acid, and forms water: thus accounting for the gradual coating of the copper with arsenic. The hydrochloric acid unites with the ammonia of the animal matter as it is decomposed by the heat, forming hydrochlorate of ammonia; and, if in excess, remains free in the solution. These arsenietted copper plates are to be taken out, cut into small chips, introduced into a bulbed tube, and exposed to a low red heat over a spirit lamp, and the arsenious acid is sublimed in octohedral crystals with triangular facettes. These may be rendered more distinct if you turn out the copper chips, close the tube with the finger, and chase the oxide up and down with the lamp. By dissolving this oxide in distilled water, you may go through the

whole of the former tests.

A very easy mode of ascertaining the exact weight of arsenic in any given quantity of fluid, would be to previously weigh the dry glass tube before introducing the arsenietted copper chips, and to weigh it again after the arsenious acid is sublimed; the copper being removed, the increase in weight would give the quantity of arsenic.

A most ingenious, scientific and elegant mode of detecting arsenic has lately been introduced by Robert Ellis, Esq., of University College, London; to whose polite attention I am indebted for his apparatus, made entirely of glass, in which I have now the pleasure of exhibiting his plan. He has discovered that the oxides of copper have such affinity for arsensic, that by merely passing arsenietted hydrogen over them, a double decomposition takes place; caloric is given out; the oxygen of the copper uniting with part of the hydrogen, forms water, which is seen in the process; the arsenic of the arsenietted hydrogen uniting with the copper, forms arseniuret of copper:

the remaining hydrogen being set free. This arseniuret of copper may be easily sublimed in a glass tube; when the whole of the arsenious acid will be deposited in thick brilliant clusters of octohedral crystals on the tube.

The objection urged against Marsh's apparatus, will, of course, equally apply to this, in being obliged to use zinc for the generation of hydrogen. There is another test which I think deserves more attention than it has yet met with-viz., the decomposition of distilled water by galvanism, to which the suspected solution is added, with pure sulphuric acid, collecting the hydrogen from the negative pole or zincode of Smee's battery, igniting it, and examining the stain left in a glass tube open at both ends. If there is the smallest particle of arsenic, the hydrogen will combine with it, and you then have a stain of metallic arsenic with rhomboidal crystals; which you may oxidize, collect, and dissolve in water; go through the fluid tests, reduce the sulphuret in a tube, and subThis is the most lime it into arsenious acid again. delicate test known, and is perfectly free from the charge of using any substance in which arsenic can exist; on which account I think it the most valuable of them all, and the one to which I would this evening particularly direct the attention of the Society.

I have likewise combined this mode of producing arsenietted hydrogen with Ellis's plan of testing it by the oxides of copper, and have succeeded in obtaining decided crystals of arsenious acid by it; thus doing away with the necessity of using zinc.

The most likely substance to be mistaken for arsenic by any of these tests is antimony, because antimony sublimes into the same kind of crystals as arsenic does. But by attending to the following rules the two substances may, I think, be easily distinguished.

Metallic arsenic sublimes at a heat of 356° without

liquifying into rhomboidal crystals; arsenious acid sublimes at 380°, into octohedral crystals; metallic antimony sublimes not under 810°; and on cooling, acquires a highly lamellated texture, and yields octohedral crystals like arsenic. After you have obtained a deposit of the suspected metal in a glass tube, if you heat the tube gradually by a spirit lamp; should the metal be arsenic, it sublimes on the cool part of the tube into octohedral crystals; which can be dissolved in water, and tested by the three fluid tests. If it is antimony, it first produces dense white fumes, and an amorphous white powder is deposited; and the heat being kept up, the tube is lined with a white crust, which is insoluble in water.

By this method, both arsenic and antimony may be tested at the same time. Arsenic will be sublimed in oxide at the cool part of the tube: antimony remaining at the hot part.

In the reduction test with sulphuretted hydrogen gas, it should be carefully remembered that the sulphurets of antimony, tin, selenium, cadmium, and tellurium, have nearly the same yellow colour, and are deposited in the same manner as the sulphuret of arsenic; and when reduced to their metallic state with black flux, they not only give an appearance so much like arsenic, that it requires a very practised eye to distinguish each-if even that be possible, but tellurium and cadmium also exhale a garlic odour, like arsenic.

L. Thompson, Esq., has shown that antimoniuretted hydrogen when ignited, not only gives a stain very similar to arsenietted hydrogen, but also that the smell of both are very similar, and suggests the following mode of distinguishing them :-Dissolve the crust left on the glass by a drop of nitric acid: evaporate it to dryness, and a white powder will be left in either case: add now, a little weak solution of nitrate of silver, and expose it to the fumes of ammonia from a glass stopper. Antimony will give a white precipitate, and arsenic a yellow floculent one. In answer to the above objection, Marsh proposed the following