Provided free phosphorus has not been detected, it is necessary to search for phosphorous acid. To this end, the residue remaining in the flask, in either Mistcherlich's or Fresenius and Neubauer's method, is introduced into the apparatus of Dusard and Blondlot. If the phosphorus reaction appears, it is sufficient; otherwise, its production may have been hindered by the presence of organic matter. In case, therefore, the flame is colorless, the evolved gas is conducted into a neutral solution of nitrate of silver. If the materials contain phosphorous acid, a precipitate of phosphide of silver is formed which should be collected and washed. The precipitate, which is now free from organic matter, is then examined for phosphorous acid by means of the apparatus of Dusard and Blondlot. ESTIMATION OF PHOSPHORUS. The best process for determining quantitatively the amount of phosphorus present is the one recommended by Fresenius and Neubauer. The gaseous current is continued until a fresh nitrate of silver solution is no longer precipitated. The solution is filtered, the precipitate washed and then dissolved in nitric acid. The silver is next precipitated by addition of hydrochloric acid, the fluid again filtered, and the precipitate well washed. The washings are added to the filtrate, and the liquid concentrated in a porcelain capsule. A solution of sulphate of magnesia, containing ammonia, is next added to the fluid, and the phosphoric acid determined as pyrophosphate of magnesia: the precipitate formed, is washed, heated to redness, in order to convert it into the pyrophosphate, and then weighed. DETECTION OF ACIDS. The search for acids is to be instituted exclusively in the alimentary canal and its contents. Were acids contained in the other organs, their presence would be due to the blood in which they had previously been absorbed, and, as in this case they would be partially neutralized by the bases contained in the blood, a conclusive decision in regard to their original existence in the suspected materials would be impossible, the salts of the acids usually searched for being normal constituents of the blood. In order to detect the presence of acids, the alimentary canal and contents are first boiled with water which is renewed until the solution ceases to exhibit an acid reaction when tested with litmus paper. The fluid is then filtered, alcohol added to the filtrate, in order to precipitate organic substances, the liquid again filtered, and the solution tested separately for the various acids as directed below. HYDROCHLORIC ACID.