_f._ Sulphate of quinine invariably contains 2 or 3 per cent. of cinchonine, originating, not from a fraudulent admixture, but from an incomplete purification of the salt. One of the best methods for detecting the respective quantities of quinine and cinchonine, present in a sample of the sulphate, is the following: Several grammes of ammonia and ether (which has previously been washed with water) are added to one or two grammes of the salt under examination, the mixture thoroughly agitated, and then allowed to remain at rest. The supernatant etherial solution contains all of the quinine; the cinchonine, which is almost completely insoluble, both in water and ether, remaining suspended between the layers of the two fluids. The ether is next removed by means of a stop-cock funnel, evaporated to dryness, and the weight of the residue obtained determined. The operation is then repeated, the ether being replaced by chloroform in which both quinine and cinchonine are soluble. The residue, formed by the evaporation of the second solution, will be heavier than the first residue: the difference between the two weighings gives the weight of the cinchonine present. _g._ The detection of the presence of sulphate of quinidine is based upon the difference in the solubilities of the oxalates of quinine and quinidine. Oxalate of quinidine is sufficiently soluble in cold water not to be precipitated by double decomposition when solutions of oxalate of ammonia and sulphate of quinidine are mixed. Under the same circumstances, quinine is almost completely thrown down. The test is applied as follows: The suspected salt is dissolved in water, a slight excess of oxalate of ammonia added, and the precipitate formed separated by filtration. If the salt be pure, the filtrate is scarcely rendered turbid by the addition of ammonia; when, however, sulphate of quinidine is present, it will be entirely contained in the filtrate, in which ammonia will produce an abundant precipitate. EXAMINATION OF BLOOD STAINS. This branch of legal chemistry formerly gave but very unreliable results. It is scarcely ten years since the reactions that are now regarded as only secondary and confirmative in their character, and far from conclusive, were the only ones in use: these are the tests based upon the presence of iron and albumen in the blood. Since then, great progress has been made in the methods employed. It must not be understood, however, that the question under consideration always admits of an easy and decisive solution: the stains are sometimes too greatly altered to be identified; but in cases where the distinctive reactions of blood can be produced, the real nature of the stains under examination can, at present, be determined with certainty.