VARIOUS DISACCHARIDES 87 



on treatment with alcoholic potash, yields cellobiose. It re- 

 duces Fehling's solution and yields two molecules of glucose on 

 hydrolysis, and is thus isomeric with maltose. 



GENTIOBIOSE. 



This disaccharide * is obtained by the partial hydrolysis of 

 the trisaccharide gentianose (see p. 91); by the action of 

 emulsin it is converted .into two molecules of glucose from 

 which it follows that gentiobiose is a glucoside. It has 

 been synthesized by the action of emulsin on glucose.f 



Trehalose is a disaccharide found in various agarics, notably 

 Boletus edulis, in moulds such as Aspergillus niger^ and in 

 Selaginella lepidophylla,\ It does not reduce Fehling's solution 

 and is strongly dextro-rotatory, a = + 1 99. When boiled in 

 acids it is slowly converted into two molecules of glucose. 



LACTOSE OR MILK SUGAR. C 12 H 22 O n . 



This disaccharide, though of considerable importance in 

 the animal kingdom, is never found in plants. It reduces 

 Fehling's solution and on hydrolysis, by the enzyme lactase or 

 by dilute mineral acids, it yields molecular proportions of 

 glucose and galactose. 



MELIBIOSE. C 12 H 22 O U . 



This disaccharide || is produced by the partial hydrolysis of 

 the trisaccharide raffinose. It yields on hydrolysis molecular 

 proportions of glucose and galactose. Melibiose is the first 

 natural saccharide that was artificially synthesized. IT 



* Zemplen: " Ber. deut. chem. Gesells," 1915, 48, 233. 

 t Herissey, Bourquelot and Coirre: "J. Pharm. Chim," 1913, 7, 181. 

 J Anselmino and Gilg : "Pharm. Zeit.," 1913,58,563; Lippmann : "Ber. 

 deut. chem. Gesells," 1912, 45, 3431. 



Winterstein : " Z. physiol. Chem.," 1894, *9> 7 



II Scheibler and Mittelmeier : " Ber. deut. chem. Gesells," 1890, 23, 1438. 



IF Fischer and Armstrong: id., 1902, 35, 3144. 



