From the above statement respecting the solubility of {145} quinidine in ether, it appears that the ten grains of the salt to be examined, may contain one grain of quinidine, and still a complete solution with ether and ammonia may follow; but in this case the quinidine will shortly begin to crystallize in the layer of ether. The last trace of quinidine may be yet more definitely detected by employing, instead of the ordinary ether, some other, previously saturated with quinidine, by which means all of the quinidine contained in the quinine must remain undissolved. It is particularly requisite in performing this last experiment to observe, after the shaking, whether all has dissolved, for owing to the great tendency of quinidine to cry­stal­li­za­tion, it may become again separated in a crystalline form, and be a source of error.

If more than a tenth of quinidine or cinchonine be present, there will be found an insoluble precipitate at the limits of the two layers of fluids. If this be quinidine, it will be dissolved on the addition of proportionately more ether, while cinchonine will be unaffected.

It is expressly to be remarked, that the necessity for testing sulphate of quinine, in search of other fraudulent adulterations is not superseded by the above described process.

We have particularly to determine upon the absence of inorganic substances, which may be effected by subjecting to red heat on a platinum dish, or simply by solution in alcohol. Gypsum, chalk, magnesia, &c., will be left undissolved. Boracic acid will be dissolved by alcohol, but its green flame will indicate its presence in the alcoholic solution when ignited.

The absence of organic substances, such as salicine, sugar, stearic acid, &c., may be inferred from the formation of a colorless solution with pure concentrated cold sulphuric acid; it is as well to leave the sulphuric acid to act for some hours.

The presence of sal-ammoniac may be detected by the addition of caustic potash to the suspected salt, when, if present, it will be known by the diffusion of the ammoniacal odour.—Phar­ma­ceu­ti­cal Journal, March, 1852.

{146}

REMARKS ON THE ENVELOPEMENT OF PILLS. BY DORVAULT.

The envelopement of pills is a minute question, an accessory in this form of administering medicines, but as it is a frequent cause of trouble to practitioners, and as their successful operation is often due to their peculiar mode of exhibition, we shall perhaps be pardoned for devoting a short space to the subject.