OEGANIC POISONS AND DEUGS 



HYDROCYANIC OR PRUSSIC ACID. 



Oceurpence. — Hydrocyanic acid is one of the mosi 

 powerful known poisons, and poisoning by it may arise 

 not only through the use of the acid and its salts in the 

 arts — e.g., in the cyanide gold extraction processes, in 

 electroplating, and in pharmacy — but also because hydro- 

 cyanic acid is, under certain circumstances, generated from 

 many plants. In the vegetable kingdom hydrocyanic acid 

 occurs in combination in the form of cyanogenetic, or 

 cyanide-producing, glucosides. 



A glucoside is an organic compound of vegetable origin 

 which, by hydrolysis with dilute mineral acids, or by the 

 agency of certain vegetable enzymes, is decomposed, yield- 

 ing always sugars and at the same time other compounds. 

 Amygdalin CjoHjyNOu, the glucoside of the bitter almond, 

 is an excellent typical example. The almond seed also 

 contains the enzyme or ferment emulsin. On macerating 

 the seed with water the emulsin is brought into contact 

 with the dissolved glucoside, and causes the decomposition 

 represented by the equation C2oH27NOu + 2H20=2C6Hi206 + 

 CjHsCHO + HCN — i.e., the amygdalin yields glucose, ben- 

 zaldehyde (or oil of bitter almonds), and hydrocyanic acid. 

 In smaller proportions amygdalin is also found in the peach, 

 plum, cherry, and apple seeds, and the formation of the 

 poisonous prussic acid from such sources appears to have 

 been known to the early Egyptian priests. The cherry 

 laurel — Primus laurocerasus — one of the commonest orna- 

 mental shrubs, contains amygdalin in the leaves, and gives 



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