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and freshly prepared sulphureted hydrogen water, sulphhydrate of ammonia, a newly-prepared alkaline solution of hypochlorite of soda (by passing chlorine gas into a solution of carbonate of soda).

A few practical remarks may conclude this important chapter.

The analyst should not allow any other operations to be carried on at the same time in his workingroom; he should not lose sight of the various objects of examination during the time of his work, and lock them up on leaving the laboratory. The presence of other persons, while the investigation is carried on, is far from agreeable, and should be as much as possible avoided. It detracts the attention and does no mortal good. The apparatus to be used should be new, or, at least, cleaned with the greatest care. The last point, in particular, should be most conscientiously attended to, and mentioned in the written report.



COPPER, LEAD, AND ZINC. $ 55. The compounds of other metals are much more rarely made use of for willful murder, or selfdestruction, than arsenious acid. In most cases of poisoning with such substances, the poison was taken by mistake or carelessness; and even this does not frequently occur, since they generally betray their presence by a peculiar metallic taste.

The number of metals treated of in this chapter may appear to some too small, to others too large; but other metals than those named will scarcely ever become the objects of a chemico-legal analysis. Nobody will raise any objections against copper, lead, and mercury. Food, cooked in copper vessels, sometimes takes up some of the metal; vinegar is often boiled purposely in vessels of copper for the manufacture of mixed pickles, to which it then imparts a fine, green color. Lead, or tin containing lead, when used for keeping or preparing articles of food, may produce poisonous effects; white lead and sugar of lead are articles of commerce, very accessible to the public, and may serve for willful poisoning. Corrosive sublimate, red oxide of mercury, and white precipitate, all of which are violent poisons, find also application in the trades, and are of easy access. Antimony has been included in the number because cases of poisoning with tartar emetic have occurred; and zinc, on account of the extensive use which is at the present time made of vessels of zinc, and the frequent substitution of zinc-white for white lead as a paint; besides, there are cases on record of poisoning with white vitriol, which is easily mistaken for Epsom salt, or other salts. Tin is, perhaps, of all these metals, the one least likely to occur in chemico-legal investigations; it has been noticed on account of the general use which is made of its compounds in the operations of dyeing. It must be borne in mind that the attempt at poisoning, alone, may lead to chemicolegal analysis, and that these metals may become the objects of analysis with regard to medical police. To commit murder by poisoning with white vitriol must be considered next to impossible, but it may involve on the chemist to show that white vitriol has been administered by mistake, instead of Epsom salt, for example.

$ 56. It would be very erroneous to think that the presence of small quantities of the above-named metals is more easily ascertained than that of a small quantity of arsenic. There is, perhaps, no metal of which equally minute quantities can be detected with the same degree of certainty, as of arsenic. Even antimony, though greatly resembling arsenic in its properties, is no exception; it lacks that characteristic odor which arsenic emits on burning, and gives no equally characteristic reaction with nitrate of silver. It is well known to every chemist that minute portions of mercury, tin, lead, and especially zinc, are very difficult of detection. Next to arsenic stands, perhaps, copper, since it is easily separated in the metallic state, even in small quantities.

If very small quantities of some of the metals under consideration have been detected, we are by no means justified to infer an attempt at poisoning. Traces of copper occur everywhere; I have attempted in vain to show its absolute absence anywhere; we eat it daily with our bread. Lead is also said to be very widely distributed in very minute quantities; its detection is attended with greater difficulties, hence its presence is not always so conclusively proved. The same may be the case with tin, which has been so frequently found by Berzelius in minerals, by treating them before the blowpipe in the reduction flame. Certain it is, that articles of food of acid reaction, when boiled in tinned vessels, take up some of the metal, without becoming thereby poisonous. Antimony and mercury do not, perhaps, so generally occur, but it should always be remembered that their compounds are extensively used as medicines, and it is said to be an authenticated fact that metallic mercury is sometimes found in the body of persons who have used for some time mercurials as a medicine.

$ 57. It might appear from the preceding remarks that it would be very difficult to decide the question whether poisoning has taken place or not. But, I think, the difficulty is not so great as it appears at first sight. There can, in my opinion, hardly ever arise any doubt as to whether, for instance, the copper found in articles of food, or the contents of the stomach, is the minute quantity which everywhere occurs, or whether it originated from copper vessels, or is intentionally mixed with the food. A practised and well-qualified expert will certainly be able to decide the point, while an inexperienced and not sufficiently qualified person does not find the minute, and as it were normal, quantity of copper at all. The same remark is still more applicable in regard to lead, tin, &c. In cases of willful murder, and still more so of suicide, the quantity of the poison administered is almost invariably much larger than necessary—a circumstance which not unfrequently saves the life of the person. It is usually only in cases of accidental poisoning that the quantity of the poisonous metal to be detected is very small; so ex. gr. in poisoning with food, which has been boiled in vessels of copper, zinc, etc.

In most cases, and even in those of willful murder, a remnant of the substance which served for poisoning will be at the disposal of the analyst. This occurs still more frequently in cases of suicide, and almost invariably if the toxic principle was taken by mistake, or carelessness, there being no reason for removing or hiding the rest of the poison. But, for reasons already stated, the majority of cases of poisoning with the metals in question will be of the latter description.

$ 58. What substances may become the objects of analysis it is utterly impossible to predict; contents, vomited matters, articles of food, commercial and chemical preparations, etc., may become objects of

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