Note G — II. DETECTION OF POISONS, THE PRESENCE OF WHICH IS SUSPECTED.

The omission in the text of Reinsch's test should be supplied. This test is based upon the fact that when solutions of arsenious acid or an arsenide are acidulated with hydrochloric acid and boiled with metallic copper, the latter becomes covered with a film consisting largely of metallic arsenic: it is extensively employed in chemico-legal examinations. The materials to be examined are completely disintegrated by boiling with hydrochloric acid, and the fluid filtered. Some pure copper gauze or foil, having a polished surface, is then immersed in the boiling solution, and notice taken of the formation of a grey deposit. If a coating be formed, fresh pieces of the metal are added, so long as they become affected. The copper is then withdrawn from the solution, thoroughly washed with water, and dried, either by means of the water-bath or by pressing between bibulous paper. It is next introduced into a dry tube, and heated over a spirit lamp. The arsenic present volatilizes and is oxidized to arsenious acid which forms a deposit, consisting of octahedral crystals, on the cold part of the tubes. These are subsequently tested by means of the reactions distinctive of arsenious acid. It need hardly be added that the absolute purity of both the hydrochloric acid and of the copper is to be carefully established. The deposit obtained in the above operation was formerly regarded as pure arsenic, but it has been proved to be an alloy consisting of 32 per cent. arsenic, and 68 per cent. copper. Reinsch's test possesses the advantage of requiring but little time for its execution, of being applicable to complex organic mixtures, and of effecting the detection of a very minute trace of the poison.—Trans.