140 RESINS, BITTER PRINCIPLES, ETC. 



salts precipitate it reddish-brown from alcoholic solution. Fused 

 with potash it decomposes, yielding acetic acid, phloroglucin and ' 

 gentisic acid. The latter is isomeric with protocatechuic acid (§ 42), 

 and is coloured deep blue by ferric chloride. An alkaline solution 

 of gentisic acid becomes red ou exposure to the air ; when heated 

 it yields hydroquinone, melting at 169°. * 



For thujin, see Rochleder and Kawaher ;* for rutin (insoluble in 

 ether), and roUnin, Zwenger and Djonke ;' for Ivteolin, Molden- 

 hauer,* Schiitzenberger, Paraf and Rochleder.* 



§ 153. Jalapjn and Allied Substances. — To the group of substances 

 that are soluble in ether, and can be removed by dilute alkali, 

 but not by pure water, from the evaporation-residue 'of the 

 ethereal extract, there belong further some glucosidal resins 

 (§ 58), of which the jala]>in of Ipomtea orizabensig may be taken 

 as a representative. 



Jalapin is readily dissolved by alcohol; and in alcoholic solution 

 is resolved by hydrochloric acid into sugar and jalapinol.; the 

 latter is soluble in ether, but only sparingly soluble in water. 

 The action of aqueous solution of soda converts jalapin . into 

 jalapic acid; the latter, after liberation with a strong- acid, is 

 soluble in water, but only sparingly soluble in ether. 



Jalapinol appears to occur ready-formed in scammony, and 

 possibly in scammony-root also. 



Tampicin of Tampico-jalap resembles jalapin in most of its pro- 

 perties, but diflFers in composition.^ The same maybe said of 



' Compare Hlasiwetz-and Habermann, Annal. der Chem. und Pharm. clxxv. 

 62 ; Ber. d. d. chem. Ges. viii. 684 (Jourh. Chem. Soo; xxviii. 672). The 

 actual gentian-bitter is not identical with genti^in. The former ia eiasily 

 soluble in water, is not thrown down by neutral acetate of lead, but precipi- 

 tated by anunoaiacal acetate and liberated from the precipitate by Bulphtu«ttcd 

 hydrogen. It can be extracted with difficulty by agitation with benzene, but 

 with ease by chloroform ; ferric chloride does not precipitate it. It is sparingly 

 soluble in ether, and is said to dissolve in; cunc. sulphuric acid with red coloura- 

 tion, and to be decomposed by dilute sulphuric acid with production of sugar. 

 (Compare Kromayer, loc. cil.). 



" Chem. Centralblatt, 449, 1858, 



3 Ibid. 766, 1802. Annal. d. Chem. und Pharm. Supplement, i. 257 

 (Amer. Journ. Pharm. xxxv. 32). 



'' Annal. d. Chem. und Pharm. o. 180, 1856. 



^ Comptes Eendus, lii. 92, 1861 ; Jbum! f. prakt. Chemie, xcix/ 433, 

 1867. 



* Compare Spirgatis, N. Repert. f. Phajm. xix. 452, 1870 j Kohler und 

 Zwicke, N". Jahrb. t. Pharm. xxxii. 1, 1869 (Pharm. Joui-n. and Trans. 13], 

 i. 444). 



