GLUCOSIDES 



litre of fluid. These colours may be matched closely by 

 aqueous solutions of potassium bichromate. 



In making up the standard solution it is important to 

 allow the mixture to stand in an incubator kept at a tempera- 

 ture of 40 C. for certainly not less than an hour owing to the 

 slowness of development of the full tint. 



AMYGDALIN. 



Amygdalin, C 20 H 27 NO n , is a laevo-rotatory bitter substance 

 which is fairly soluble in water, and gives with concentrated 

 sulphuric acid a pale reddish-violet coloration, this, however, 

 is not a distinctive test, since the same coloration is given by 

 other glucosides, e.g. menyanthin. 



Amygdalin occurs in the seeds of the bitter almond, Pyrus 

 Amygdalus ; it is, however, generally stated not to occur in 

 the seeds of the cultivated almond, the sweet variety, although 

 emulsin, its appropriate enzyme, is present. Dunstan and 

 Henry have shown that traces of hydrocyanic acid occur in 

 the seeds, and more than traces in the seedlings, of the sweet 

 almond ; it is probable, therefore, that a small quantity of 

 amygdalin does occur in the sweet variety. This relative 

 absence of glucoside in the cultivated plant is important, and 

 the same phenomenon has been found to obtain, by these 

 same authors, in Phaseolus lunatus. The seeds of the wild 

 plant yield large quantities of hydrocyanic acid, whereas those 

 of the cultivated plants give very little or none. 



Amygdalin has also been described as occurring in Pyrus 

 Malus y Pyrus Aucuparia, Pyrus cydonia and other plants. 



This glucoside is generally obtained by crushing the seeds 

 of the bitter almond and subjecting the mass to considerable 

 pressure between hot iron plates in order to remove the oil. 

 The solid cake is then digested with hot alcohol which dis- 

 solves out the amygdalin. The alcoholic extract is evaporated 

 down when the amygdalin separates out in scale-like crystals 

 belonging to the monoclinic system. 



It has already been mentioned that the appropriate enzym 

 generally occurs in the same tissues as the glucoside; this 

 being so, the bitter almonds have only to be crushed in water 

 in order to bring the ferment emulsin into contact with the 

 amygdalin to bring about the hydrolysis. 



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