CORTEX CINCHONA. 363 



manner to the formation of this or that alkaloid ; and it may even be 

 hoped that the cultivators of cinchona will discover methods of pro- 

 moting the formation of quinine and of reducing, if not of excluding, 

 that of the less valuable alkaloids. 



Most salts of the alkaloids of cinchona afford a beautiful purple tar 

 when they are heated in a test tube, and the same is also produced 

 with the powdered bark, provided alkaloids be present. No other 

 bark, as far as we know, yields a similar product of the dry distillation. 

 It is not observed even in using true Cinchona barks, which are devoid 

 of alkaloids. This method for ascertaining the presence of alkaloids in 

 Cinchona barks has been proposed in 1858 by Grahe of Kasan. Hesse 

 has improved Grahe's test in the following way: he extracts the 

 powdered bark with slightly acidulated water and dries up the liquid 

 with a little of the powder. Grahe s test at once shows whether a 

 given bark contains Cinchona alkaloids or not. 



Acid principles of Cinchona Barks — Count Claude de la Garaye' 

 observed (1746) a crystalline salt deposited in extract of cinchona bark, 

 which salt was known for some time in France as Sel essential de la 

 Garaye. Hermbstadt at Berlin (1785) showed it to be a salt of calcium, 

 the peculiarity of whose acid was pointed out in 1790 by C. A. Hoffmann," 

 an apothecary of Leer in Hanover, who termed it ChiTiasdure. The 

 composition of this substance, which is the Kinic Acid of English 

 chemists, was ascertained by Liebig in 1830 to be C'^'O", or now 

 C®H"(OH)^COOH. The acid forms large monoclinic prisms, fusible at 

 162° C., of a strong and pure acid taste, soluble in two parts of water, also 

 in spirit of wine, but hardly in ether. The solutions are levogyre. 

 Kinic acid appeal's to be present in every species, and also to occur in 

 barks of allied genera ; and in fact to be of somewhat wide distribution 

 in the vegetable kingdom. By heating it or a kinate, interesting 

 derivatives are obtained ; thus, by means of peroxide of manganese and 

 sulphuric acid, we get yellow crystals of Kiiione or Quinone, C^H^O', — 

 a reaction which may be used for ascertaining the presence of kinic 

 acid. Kinic acid is devoid of any noteworthy physiological action. 



Cincho-tannic Acid — is precipitated from a decoction of bark by 

 acetate of lead, after the decoction has been freed from cinchona-red by 

 means of magnesia. Dr. de Vry informed us that the Indian barks are 

 usually richer in cincho-tannic acid ; their cold infusion becomes turbid 

 on addition of hydrochloric acid, which forms an insoluble compound 

 with the former. 



The cincho-tannate of lead decomposed by sulphuretted hydrogen, 

 and the solution cautiously evaporated in vacuo, yields the acid as an 

 amorphous, hygroscopic substance, readily soluble in water, alcohol, or 

 ether. The solutions, especially in presence of an alkali, are quickly 

 decomposed, a red flocculent matter, Cinchona-red, being produced. 

 Solutions of cincho-tannic acid assume a greenish colour on addition of 

 a ferric salt. By destructive distillation, cincho-tannic acid affords 

 pyrocatechin. 



Quinovic (or Chinovic) Acid, C^H^O^ crystallizes in hexagonal 

 scales which are sparingly soluble in cold alcohol, more readily in 

 boihng alcohol, but not dissolved by water, ether, or chloroform. It 



» Clumie hydrmdiqw, Paris, 1746. 114. « Crell's Clum, Annalen, 1790, ii. 314-317. 



