140 RESINS, SITTER 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 on exposure to the air ; when heated 

 it yields hydroquinone, melting at 169 . 1 



For thujin, see Rochleder and Kawalier ; 2 for rutin (insoluble in 

 ether), and robinin, Zwenger and Dronke ; 3 for luteolin, Molden- 

 hauer, 4 Schiitzenberger, Paraf and Rochleder. 5 



153. Jalapin 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 jalapin of Ipomcea orizabensis 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 differs in composition. 6 The same may be said of 



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

 62 ; Ber. d. d. chem. Ges. viii. 684 (Journ. Chem. Soc. xxviii. 572). 

 actual gentian-bitter is not identical with gentisin. The former is easily 

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

 tated by ammoniacal acetate and liberated from the precipitate by sulphurette 

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

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

 soluble in ether, and is said to dissolve in cone, sulphuric acid with red coloura- 

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

 (Compare Kromayer, loc. cit.). 



2 Chem. Centralblatt, 449, 1858. 



3 Ibid. 766, 1862. Annal. d. Chem. und Pharm. Supplement, i. 257 

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



4 Annal. d. Chem. und Pharm. c. 180, 1856. 



5 Comptes Rendus, lii. 92, 1861 ; Journ. f. prakt. Chemie, xcix. 433, 

 1867. 



6 Compare Spirgatis, N. Eepert. f. Pharm. xix. 452, 1870; Kohler und 

 Zwicke, N. Jahrb. f. Pharm. xxxii. 1, 1869 (Pharm. Journ. and Trans. [3], 

 i. 444). 



