i8o GLUCOSIDES 



above equations ; emulsin, on the other hand, can hydrolyse 

 the mandelonitrile glucoside as indicated in the second 

 equation, and, of course, it can bring about the whole series 

 of changes. Since, moreover, the hydrolysis can be effected in 

 two stages successively by the enzymes maltase and emulsin, 

 which react with a- and /3-glucosides respectively, it follows that 

 amygdalin must be an a/3-glucoside of benzaldehyde cyan- 

 hydrin as represented by the formula : 



_0_ C 6 H S 



CHaOH CHOH CH CHOH CHOH CH . O . CH 2 CHOH CH CHOH CHOH CH . O . CH 



1 o 1 i 



The mandelonitrile glucoside * obtained by the partial 

 hydrolysis of amygdalin is identical with the naturally occurring 

 glucoside prunasin * contained in the twigs of Prunus padus 

 and is isomeric with prulaurasin,* the glucoside occurring in 

 the leaves of Prunus laurocerasus ', and sambunigrin * which 

 occurs in the fruit of the elder Sambucus niger. Sambunigrin 

 has been synthesized by Fischer and Bergmann. f 



The crude oil of bitter almonds contains hydrocyanic acid 

 which may be removed by distillation with lime and ferrous 

 chloride which converts the prussic acid into Prussian blue. 

 Pure benzaldehyde is a colourless or pale yellow liquid, soluble 

 in alcohol, but practically insoluble in water. Its specific 

 gravity is 1*05, and its boiling point 1 80 C. On exposure 

 to air it becomes converted into benzoic acid. 



DHURRIN. 



This is a glucose closely allied to amygdalin, and occurs 

 in the seedlings of Sorghum vulgare, but not in the older 

 plants ; it has the empirical formula C U H 17 NO 7 [and yields, 

 on hydrolysis, glucose, hydrocyanic acid and parahydroxy- 

 benzaldehyde : 



C 14 H 17 NO 7 + H 2 O = C 6 H 12 O 6 + HCN + C 6 H 4 OHCHO 



Similar glucosides occur in the seedlings of Panicum aru 

 Zea. 



PHASEOLUNATIN. 



Phaseolunatin, C 10 H 17 O 6 N, occurs in the seeds of wild 



* For structural formula see p. 169. 



t Fischer and Bergmann : " Ber. deut. chem. Gesells.," 1917, 50, 1047. 



