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QUINIDINE. BY MR. ROBERT HOWARD.
This alkaloid, which gained a prize in the Great Exhibition, has scarcely yet attracted much attention. Some of the cheaper barks now largely imported from New Grenada contains so much of it that it is, perhaps, as well that it should be more studied. The Cinchona cordifolia, from this part of the continent, is particularly rich in it. It is, however, contained in larger or smaller quantities in the Bolivian and Peruvian barks—the Cinchona Calisaya, Boliviana, rufinervis, and especially ovata.
Referring your readers to a very able paper in your Journal,[10] I beg to add a few facts from my own observations.
[10] Pharmaceutical Journal, vol. ix., p. 322, January, 1850.
The sulphate of quinidine, or β quinine as it is called by some, (Van Heijninger and others,) is so like the sulphate of quinine, that the eye or the taste can with difficulty distinguish them. It forms the same light fibrous crystallization, and occupies as large a bulk. It corresponds in appearance with the description given by Winckler, of “chinidine.” (See Pharm. Journ. for April, 1845, vol. iv., p. 468.) He notices that it has “a remarkably white color and a peculiarly faint lustre.” Its most striking characteristic is its extreme solubility. Pure sulphate of quinine requires nearly thirty times its weight of boiling water for solution, whilst the sulphate of quinidine dissolves in four parts. On the other hand the pure alkaloid crystallizes readily out of proof spirit and out of ether, whilst quinine does not crystallize out of either. A very good test for the presence of cinchonine in sulphate of quinine is also capable of being applied to detect the presence of β quinine. On this point I would refer for very interesting details to a paper by M. Guibourt, in the Journal de Pharmacie for January in this year.
In your Journal of April, 1843, I gave a test for sulphate of quinine, to which I would again advert, because subsequent {142} experience has proved it to be a tolerable easy, and at the same time exact means of ascertaining its purity. Put 100 grains in a Florence flask with five ounces of distilled water, heat this to brisk ebullition; the sulphate of quinine ought not to be entirely dissolved; add two ounces more water, and again heat it to ebullition; ought to make a perfectly clear solution. If this be allowed to cool for six hours, and the crystals carefully dried in the open air on blotting paper, they will be found to weigh about ninety grains, the mother-liquor may be evaporated and tested with ether, when any cinchonine or β quinine will be easily detected. On examining sulphate of quinine of commerce from several leading manufacturers, I have found all of them give, within a grain or two, the same result, and, in each, indications of a β quinine, though to an unimportant extent.
The above quantity of water (seven ounces) readily dissolves 800 grains of sulphate of β quinine; and if 100 grains of this salt are dissolved in seven ounces of water, the crystals as above weigh only fifty-four grains, thus leaving forty-six grains in solution instead of about ten grains.
The medical effects of β quinine deserve investigation, the chemical constitution and the taste appear to indicate a great similarity if not identity.