470 THE POPULAR SCIENCE MONTHLY. 



seeds, and imparting a slight astringency to the juice, retained after 

 fermentation. In the red wines from 0.08 to 0.2 per cent, of tannin is 

 found. The decomposition of tannin, by a fermentation producing 

 sugar, has been mentioned under the head of sugars. Tannin is also 

 liable to oxidation with various products not including sugar. 



The vegetable kingdom furnishes numerous compounds, known as 

 gltjcosides, which are capable of definite and distinctive fermenta- 

 tions, one of the fermentation-products in each instance being sugar. 

 A number of these glucosides are found in fruits. One of the most 

 important of these is amygdalin, a glucoside found in the fruits, 

 leaves, etc., of plants of the almond family, especially in the kernels 

 of the bitter-almond, peach, and cherry, the leaves of the cherry-lau- 

 rel, and the bark of the wild-cherry. 



Amygdalin, when obtained pure, is a white, odorless solid, with a 

 taste both sweet and bitter. Taken alone it is not poisonous, even in 

 considerable quantities. But if mixed with a substance named emul- 

 sin, and wetted, amygdalin begins at once to break up, with forma- 

 tion of three other compounds, as follows : 



Amygdalin, 457 parts (by contact with ( L Bitter-almond oil, 106 parts. 



emulsin and cooperation with wa- \ 2 " Hydrocyanic acid (or "pnissic 

 ter), produces : | acid "), 27 parts. 



13. Glucose, 360 parts. 



In the plant, amygdalin is accompanied with the emulsin needful 

 for its fermentation. During the ripening of the fruit, and in the 

 maturity of the leaves and other parts, the amygdalin is constantly, 

 though slowly, being transformed into the three products above 

 named. The bitter-almond oil and hydrocyanic acid are volatile and 

 odorous, and give the pleasant odor of peach-kernels, almonds, etc., 

 familiar to every one. The rapidity of the chemical change is chiefly 

 governed by the proportion of moisture, being greatly accelerated by 

 wetting the bruised kernels or leaves, and stopped altogether by 

 drying, while the moisture of the living plant permits only a gradual 

 rate of the transformation. One of the products of this change is 

 poisonous, the well-known hydrocyanic acid, or prussic acid, one- 

 tenth of a grain of which is a full medicinal dose. The bitter-almond 

 oil (known to chemists as benzoic aldehyde, and easily oxidized to 

 benzoic acid) is not in the least poisonous (when separated from the 

 hydrocyanic acid). It will be seen from the numbers of parts result- 

 ing from the change (as given above) that one part of hydrocyanic 

 acid and four of bitter-almond oil are produced by sixteen parts of 

 pure amygdalin. The amygdalin of the shops, in Europe, where it is 

 somewhat used to generate hydrocyanic acid in medicine, yields from 

 aV t0 "2~V f ^ ts weight of hydrocyanic acid. In exposure to the air, 

 the hydrocyanic acid, being very volatile, is quickly dissipated, while 

 the bitter-almond oil vaporizes more slowly. In most fruits of the 



