1·224 gram of herapathite = 0·674 gram of quinine.
According to the formula of the bitartrate, C20H24N2O21C4H6O6 + Aq. = 442; 1·048 of bitartrate represents 0·69 of quinine, so that 1·255 gram of herapathite should have been obtained.
Notwithstanding the different circumstances in which the reagent was applied, the results are satisfactory.
The two following experiments were made with pure quinine, dried at 100° C., at which temperature it still retains water, under identical circumstances:—
1·0664 gram of hydrated quinine gave 1·7266 gram of herapathite = 164·5 per cent.
1·055 grams of the same hydrated quinine gave 1·7343 gram of herapathite = 164·3 per cent.
The author further states that the iodosulphate of quinine and of quinidine prepared by means of his new reagent have an analogous composition, and are identical with the compound described by Herapath, whilst the iodosulphates of cinchonine and cinchonidine have a different composition from the former, and both require more iodine to be converted into the optical iodosulphates described by Herapath. Of all these iodosulphates that of quinine is by far the most insoluble in alcohol, and is precipitated first and free from the others by a judicious application of the iodosulphate of chinioidine.
Quinine is distinguished from both cinchonine and quinidine by its comparatively free solubility in ether; the last of these being very sparingly soluble, and the other wholly insoluble, in that menstruum. The presence of cinchonine may also be positively determined by reference to the behaviour of that alkaloid. Quinidine is also distinguished from quinine by the different crystallisation, greater specific gravity, and freer solubility of its salts in cold water.[128]
[128] An extremely elegant and highly sensitive method of testing for quinine and quinidine by means of the microscope, &c., is described at considerable length, by Dr Herapath, in the ‘Pharm. Journ.’ for November, 1853.
Estim. See Quinometry.