2. The lead is dissolved in wine. For the detection of this dangerous fraud, the reagent invented by Dr. Hahnemann affords a ready and convenient test. It consists of water saturated with sulphuretted hydrogen gas, and acidulated with muriatic acid;[[392]] this latter ingredient is added for the purpose of preventing the precipitation of any iron, which the wine might accidentally contain. This liquor will, if added in the proportion of one part to two of wine, produce with the smallest quantity of lead, a dark coloured, or black precipitate; which, if collected, dried, and fused before the blow-pipe on a piece of charcoal, will yield a globule of metallic lead. Or we may modify the experiment by passing a current of sulphuretted hydrogen gas through the wine, having previously acidulated it with muriatic acid, to prevent the precipitation of the iron.
A farther proof of the presence of lead in wines is the occurrence of a precipitate, on adding a solution of the sulphate of soda.
The most satisfactory proof, however, is derived by distilling off the alcohol, and calcining the residuum with charcoal, in order to obtain the metallic lead.
The quantity of lead which has been detected in sophisticated wine, may be estimated at forty grains of the metal in every fifty gallons,[[393]] but this will of course be liable to vary with the degree of acidity it was intended to correct.
3. The lead is dissolved in oils. In this case the lead may be detected by shaking, in a stopped phial, one part of the suspected oil, with two or three parts of water, impregnated with sulphuretted hydrogen. This test will announce the presence of the deleterious metal, by occasioning a dark brown, or black colour.
4. The lead is mixed with alimentary matter. M. Orfila has furnished us with the following directions for assaying the matter vomited, or that which may be found in the digestive canal, after death. “After having expressed the fluid portion through a piece of fine linen, it must be assayed by the tests, which have been already enumerated as being capable of detecting the salts of lead; and if the precipitates obtained are of a nature to induce a belief, that the fluid contains some preparation of this kind, it must be evaporated to dryness, and calcined with charcoal in a crucible; when, at the expiration of three quarters of an hour, metallic lead will be obtained. If all the experiments made on the fluid portion of the matter vomited, for the discovery of this poison, should be fruitless, the whole of the solid portions, previously dried, should then be calcined with potass and charcoal, by which means metallic lead will be obtained.”
VEGETABLE POISONS.
The poisons of which we are about to offer the physiological and chemical history, although more numerous than those which belong to the mineral kingdom, are, notwithstanding, of far less importance in a forensic point of view. With the exception of opium, and some few others, they must be considered as objects of accidental, rather than of criminal poisoning; and even with respect to the former narcotic, it may be said to afford more frequently the means of destruction to the suicide, than to the assassin.
The sensible qualities of smell, taste, and sometimes colour, which so eminently characterise deleterious plants, must necessarily render them ill calculated to favour that secresy, which constitutes the indispensable companion of crime; while their bulk, and the pharmaceutical preparation which they require, are alike inconsistent with the hope of concealment.
Thus we receive, as it were, from Nature, that protection which art can no longer supply; and the commission of crime is either prevented or discovered, in cases where the powers of chemistry would fail in its detection.