§§127, 128. CAOUTCHOUC, ETC. 109 



C. Schmidt ■} for angelicin, which has Ijeen proved to Ije identical 

 with hydrocarothi, see Brimmer f for carotin, see Husemann.^ The 

 last-named sul)stance forms red crystals, sohible in benzene and 

 bisulphide of carbon. It dissolves in cone, sulphuric acid, with a 

 purplish-blue colour, and is also coloured blue by sulphurous-acid- 

 gas. 



Anemonol, which occurs in many Ranunculaceae, may also be 

 mentioned here. It is an oily acrid liquid, volatile with the vapour 

 of water, and gradually changing in aqueous solution to crystalline 

 anemonin. The latter can be isolated by shaking the aqueous 

 solution with ether or chloroform, and like anemonol, acts as an 

 irritant when applied to the skin.* 



For capsicin and caj^saicin see Thresh f for amyr'm and hryoidin 

 see Buri.'^ 



§ 127. Caoutchouc. — Petroleum spirit extracts only a trace of 

 caoutchouc, which remains vtndissolved on treating the residue 

 after evaporation Avith warm aljsohxte alcohol. If a considerable 

 quantity of caoutchouc is present the majority is left in the sub- 

 stance after exhaustion with petroleum-spirit, and may be extracted 

 by bisulphide of carbon containing 6 to 8 per cent, of alcohol, or 

 by chloroform. From these solutions it may be precipitated by 

 the addition of more alcohol, whilst resinous substances and the 

 like generally remain dissolved. (See also § 46.) 



§ 128. Estimation of Glycerin (§ 13). — For details of the deter- 

 mination of this substance see Keichardt,'' and Neubauer and 

 Borgmann. ^ The latter authors point out the fact that ether- 

 alcohol removes other substances besides glycerin from wine, etc., 

 and that the estimation may accordingly be too high. They 

 therefore recommend dissolving the glycerin residue in alcohol, 

 adding 3 volumes of ether, filteiing and evaporating. Pasteur 

 advises the evaporation of the solution to be conducted as quickly 



■■• Annal. d. Chem. imd Pharm, liii. 156, 1845. 



2 N. Eepert. f. Pharm, xxiv. 665, 1874 (Pharm. Journ. and Trans. [3], vii. 91). 



3 Annal. d. Chem. und Pharm, c.xvii. 200, 1861. 



■• Compare Fehling, Annal. d. Chem. mid Pharm, xxxviii. 278, 1841 ; Midler, 

 Chem. Centrlb. 618, 1850 ; Erdmann, Journ. f. prakt. Chem. Ixxv. 209. See 

 Amer. Journ. Pharm, xxxiv. 300 ; xxxi. 440. 



^ Pharm. Journ. and Trans. [3], vi. 941, vii. 473. 



6 N. Eepert. f. Pharm. 220, 1875 (Pharm. Journ. and Trans. [3], vii. 157). 



' Archiv d. Pharm. [3], x. 408 ; [3], xi, 142, 1877. 



8 Zeitschr. f. anal. Chemie, xviii. 442, 1878, See also Pasteur, Annal. d. 

 Chem. und Pharm. Iviii. 330, 1864. 



