_Reinsch’s Process._—The suspected liquid is boiled with from one-sixth to one-eighth of its bulk of pure hydrochloric acid, and a bright slip of copper introduced. If arsenic be present the copper will be coated with it in the form of an iron-grey deposit. Next after removing the copper, washing it with distilled water, and drying it between folds of blotting paper, cut it into slips, and introduce it into a reduction-tube and apply heat; arsenious acid will be sublimed and deposited on the sides of the tube, in the form of minute octahedral crystals. These may be dissolved in water and tested in the usual way. Before resorting to this test, the acid must be examined to make sure of its purity. This is easily effected by boiling the copper with a mixture of the hydrochloric acid and distilled water before adding the suspected liquid. In conducting the analysis in the case of Smethurst (Cent. Crim. Court, Aug. 1859) Taylor and Odling found that all the varieties of copper in common use for Reinsch’s process contained arsenic. A copper of ascertained purity must therefore be used. _Arsenic in Organic Matters._—The following process, which has been introduced by Dr. Taylor, is a very convenient one. The suspected matters are to be thoroughly dried in a water-bath or otherwise, taking care not to use too great a heat. They are then to be introduced into a flask fitted with a long bent tube; to the dried material is to be added a quantity of strong hydrochloric acid, proved free from arsenic, sufficient to drench it, and the whole allowed to digest for some hours. At the end of that time heat is to be applied to the flask by means of a sand-bath, and a receiver fitted to the bent tube. The receiver should contain a little water, and both it and the bent tube should be kept cool. As distillation goes on the arsenic passes over in the form of chloride of arsenic, and is collected in the receiver beyond. A second portion of hydrochloric acid may be used to remove any last traces of arsenic in the organic material. The arsenic may be recovered from the chloride by boiling with pure polished copper, as in Reinsch’s process. The process of Fresenius and Von Babo given at page 31 is especially adapted for the recovery of arsenic from organic admixture. Several cases of poisoning by arsenuretted hydrogen are on record, some proving fatal. CHAPTER XVI. ANTIMONIAL COMPOUNDS. In its metallic state antimony is not regarded as poisonous. Two of its preparations, however, claim attention; namely, tartar emetic, and chloride of antimony.