Licence: Attribution 4.0 International (CC BY 4.0)
Credit: The tests for purity of quinine salts / by Frank Tutin. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![THE TESTS FOR PURITY OF QUININE SALTS.* BY FRANK TUTIN, F.C.S. The tests adopted by the various national pharmacopoeias for ascertaining the freedom of quinine salts from an undue proportion of other cinchona alkaloids may be divided into two general classes. One of these is represented by the so-called ammonia test, which is based on a method originally proposed by Kemer.f and is now adopted by most of the pharmacopoeias. The other class is represented by the method of the British Pharmacopoeia, and involves separate tests for einchonidine and cinchonine, quinidine, and cupreine. The respective merits of these two general methods have been critically considered from time to time by various in- vestigators. Nevertheless, it has recently been brought to the author’s notice that there are several conditions affecting the accuracy of the ammonia test, and this fact has sug- gested its further investigation. A number of important observations have thus been made whereby it has been ren- dered evident that the ammonia test has a much more limited application than has generally been supposed. I. Quinine Sulphate. The test originally proposed by Kerner for the detection in quinine sulphate of other cinchona alkaloids, and which is referred to in this communication as the “ ammonia test,” depends upon the fact that, whilst quinine sulphate is less soluble in water than the corresponding salts of the other alkaloids with which it is usually associated, quinine itself, when freshly precipitated, is much more soluble in ammonia than the bases yielded by the latter salts. For the purpose of this test, an aqueous solution of the salt, saturated at 15°, is prepared, and the amount of 10 per cent, aqueous ammonia which will, at 15°, yield a clear liquid when mixed with 5 C.e. of the former solution is then determined. This is con- sidered to afford some indication of the amount of cinchona alkaloids other than quinine in the sample of salt tested. The method of procedure differs somewhat in the various * Communicated from the Wellcome Chemical Research Laboratories, London, E.C., and reprinted from The Pharmaceutical Journal November 13th, 1509. t Arch. d. Pliarm. 1881, [3], 16, 186.](https://iiif.wellcomecollection.org/image/b22425408_0005.jp2/full/800%2C/0/default.jpg)
