§ 168. OTHER BITTER PRINCIPLES. 176 



colouration of the leaves produced thereby would arouse a sus- 

 picion 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 witli freshly precipitated hydrate of copper, 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 temperature, the residue 

 dissolved in cold alcohol, and the indican precipitated by ether. 

 Dilute acids decompose this unstable body, as above de.'icribed, 

 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 be again precipi- 

 tated by passing a current of air through it. 



§ 168. The following bitter principles have not as yet been shown 

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

 more fredy in alcohol: AnHarin,^ aridolochia-hUter,^ ealendulin^ 

 (gelatinizes with water), ccUifornin* (appears to be a, mixture of aBka- 

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

 is especially interesting) ; carapin,^ craUegin,^ cusparin '' (coloured 

 green by nitric acid, red by mercurous nitrate); quinovin^ (quin- 

 ovic acid, obtained by boiling quinovin or quinovarbitter with 

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



^ See de Vrij and Ludwig, Zeitschr. d. oesterr. Apoth. Ver. 92, 1868 (Amer. 

 D'ourn. Fharm. xxxv. 47i). 



* See Walz, Jahrb. I. Pharm. xxvi. 73. Gmelin's ' Organic Chemistry.' 

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



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

 chem. Ges. xi. 1542, 1878 (Joum. Chem. See. xxxyi. 73). 



* See Caventou, Vierteljahresschr. f . pract. Pharm. x, 422, 1861 (Amer. 

 Jonm. Pharm, xxxi. 231). 



" See Leroy, Joum. de Chim. m<!d. xvii. 3. 



'' See Saladin, ibid, ix, 888 (Amer. Joum. Pharm. v. 846). 



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

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

 Pharm. in Ne4erl. 152, 1878) was pronounced unsatisfactory by de Vrij (ibid. 

 306). 



