§ 168. OTHER BITTER PRINCIPLES. 175 



colouration of the leaves produced thereby would arouse a sus- 

 j)icion of its presence. Cold spirit extracts indican ; the solution is 

 best evaporated in a current of dry air at the ordinary temperature. 

 Foreign bodies may be removed from the aqueous solution by 

 shaking it with freshly precipitated hydrate of copi^er, but the 

 copper that simultaneously passes into solution must be subse- 

 quently removed by sulphuretted hydrogen. The aqueous solution 

 must also be evaporated at the ordinary temjierature, the residue 

 dissolved in cold alcohol, and the indican precii)itated by ether. 

 Dilute acids decompose this unstable body, as above described, 

 with production of indigo-blue. 



The latter is characterized by its insolubility in water, alcohol, 

 and ether and solubility in carbolic and fuming sulphuric acids. 

 It can be sublimed, and yields indigo-white (soluble in water) 

 when boiled with glucose and an alkali. Advantage might be 

 taken of the latter property testing for indican in dried vegetable 

 substances. The residue of the material after exhaustion with 

 water might be boiled with an alkali and glucose ; from the 

 solution thus obtained the indigo-blue would l»e again precipi- 

 tated by passing a current of air through it. 



§ 168. The ioWo^v'm^hitter pinciples have not as yet been shown 

 to be glucosides ; but they are likewise sparingly soluble in ether, 

 more freely in alcohol: Antiarin} aristolochia-bitter,^^ calendiilin'-^ 

 (gelatinizes with water), calif ornin^ (appears to be a mixture of alka- 

 loids, of which loturin, which is strongly fluorescent in acid solution, 

 is especially interesting) ; carajnn,^ cratcegin,^ cusjmrin "^ (coloured 

 green by nitric acid, red by mercvirous nitrate) ; quinorin ^ (quin- 

 ovic acid, obtained by boiling quinovin or quinova-bitter with 

 acids, is said to resemble cholic acid in gradually turning red with 



^ See de Vrij and Ludwig, Zeitschr. d. oesterr. Apoth. Yer. 92, 1S68 (Amer. 

 Journ. Pharm, xxxv. 474). 



^ See Walz, Jahrb. f. Pharm, xxvi. 73. Gmelin's 'Organic Chemistry.' 



3 See Stoltze, Ber. Jahrb. f. Pharm. 1820. 



■* See Mettenheimer, N. Jahrb. f. Pharm, i. 341, 1870. Hesse, Ber. d. d. 

 chem. Ges. xi. 1542, 1878 (Journ. Chem. Soc. xxxvi. 73). 



^ See Caventou, Vierteljahresschr. f . jiract. Pharm, x. 422, 1861 (Amer. 

 Journ. Pharm, xxxi. 231). 



" See Leroy, Journ. de Chira. med. xvii. 3. 



'^ See Saladin, ibid. ix. 388 (Amer. Journ. Pharm, v. 346). 



8 Compare Gmelin, ' Handbook of Organic Chemistry. ' Staeder's method of 

 estimating quinovic acid in certain cinchona barks (N. Tijdschr. voor de 

 Pharm, in Nederl. 152, 1878) was pronounced unsatisfactory by de Vrij (ibid. 

 306). 



