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 *pose it still more effectually. The animal principles do not act on tartar-emetic, with the exception of milk, which is slightly coagulated by a concentrated solution. Many vegetable and animal substances, though they do not decompose it, alter the operation of the fluid tests. Thus tea, though it does not effect any distinct decomposition of the salt, will prevent the action of gall-infusion; and French wine gives a violet tint to the precipitates with that test and with acids. Hydrosulphuric acid, however, acts under all circumstances, and always characteristically, whatever the colour of the fluid may be. Dr. Turner found that when transmitted through a diluted solution in tea, porter, broth, and milk, with certain precautions to be mentioned presently, he procured a precipitate which either showed its proper colour at once, or did so at the margin of the filter on which it was collected.

The circumstances now referred to render it necessary to resort to other means, besides the simple application of liquid reagents, for the purpose of detecting tartar-emetic in complex organic mixtures. This subject has been ably investigated, first by Dr. Turner, and after-terwards by Professor Orfila. The result of the researches of both seems to me to be that the most convenient method yet proposed is the following.

Process for Tartar-emetic in Organic Mixtures.—If the subject of analysis be not already liquid enough, add distilled water. Then acidulate with a little hydrochloric and tartaric acids; the former of which throws down some animal principles, while the latter dissolves readily all precipitates formed with tartar-emetic by reagents or organic principles except the sulphuret. Filter the product.

1. Subject a small portion of the liquid to a stream of hydrosulphuric acid gas, and if it be perceptibly coloured orange-red, treat the whole liquid in the same way; boil to expel the excess of gas, collect the precipitate, dry it, and reduce it by hydrogen gas in the following manner. Put the sulphuret in a little horizontal tube, transmit hydrogen through the tube by means of the apparatus reprsented in Figure 9, and when all the air of the apparatus is expelled, apply heat to the sulphuret with a spirit-lamp. Hydrosulphuric acid gas is evolved, and metallic antimony is left, if the current of hydrogen be gentle, or it is sublimed if the current be rapid.—When there is much animal or vegetable matter present in the sulphuret, the metal is not always distinctly visible. In that case, dissolve the antimony by the action of nitric acid on the mixed material and broken fragments of the tube, and throw down the orange sulphuret again from the neutralized solution by hydrosulphuric acid.

2. If hydrosulphuric acid do not distinctly affect the liquid, or if no precipitate be separated after boiling, or so small a quantity as