Sulphates, chlorides, carbonates and phosphates are most frequently met with in the preceding examination, and it should be carefully noticed which of these salts exist in the greatest abundance. If acids of comparatively rare occurrence (such as the oxalic and tartaric) are found, their approximate amount is also to be noted. These facts, together with the original acidity of the materials and the absence of other toxical bodies, would lead to the conclusion that the poisoning was caused by the reception of an acid, as well as to the identification of the special acid used. In subsequently effecting the detection of the poison by the determinative tests, the danger of destroying other poisons possibly contained in the substance will be obviated, as the question of the absence or presence of these latter will have been previously decided. (5). The examination for acids concluded, the various fluids which have accumulated, and from which the acids present have been separated, are united and the whole evaporated to dryness. The organic substances, present in the residue obtained, are destroyed by means of nitric acid, and the residual mass examined for _soda_. If this substance has not been introduced into the portion of fluid examined, and is discovered in a quantity largely in excess of the amount normally contained in the organism, it is probable that poisoning has been caused by its administration, and that an acid has also been given, either in order to mask the poison, or to act as an antidote. In this case, it is necessary to carefully search for acetic acid, as this is the substance usually employed as an antidote for alkalies. (6.) Whatever results have been obtained by the preceding examinations, the portion of the fluid which has been treated with soda (_vide_ p. 87) is evaporated to dryness. The organic matters possibly present are destroyed by means of nitric acid, or _aqua regia_, and the residue taken up with water. The solution so obtained is then examined for metals (including potassa, which salt has not been introduced into this portion of the fluid in any of the preceding operations) by the usual methods. (7). The soluble portion of the suspected materials having been thoroughly tested, the undissolved substances remaining on the filter are next examined. _b._ SOLID PORTION.