26 

 591.-PRUSSIC ACID IN CASSAVA ROOTS. 



It has been recently ascertained that the poisonous principle in 

 Primus amygdalus, Lotus arabicus, and Sorghum vulgare. is due to 

 the formation of H C N or Prussic acid as the result of the decom- 

 position oi' a glucoside by an enzyme, or inorganised ferment, in the 

 presence of water.* 



Several published analyses of the Cassava root appear to show 

 that prussic acid is obtainable by allowing the sliced material to rest 

 in the presence of water for some hours, and that fresh amounts of 

 poison can be extracted several times in succession. It is therefore 

 possible that the primary poison content is largely added to by rapid 

 decomposition, when the material is allowed to rest in the presence of 

 water. As yet. however, we do not appear to be in possession of the 

 exact amount of poison the roots originally contain, for in the 

 laboratory processes, the method has been to extract with water, 

 causing a " cyanogenetic'" process to be set up. which actually appears 

 to generate the acid. 



As additional evidence that the poison is so generated, we have 

 the well-known fact, that cooked cassava after standing a few hours, 

 becomes poisonous ; and many cases of poisoning have been attributed 

 to this cause. 



The material of the Cassava root grated and dried, which becomes 

 damp by the absorption of moisture from the atmosphere, has also 

 been found on analysis to contain Prussic acid, although when in a 

 perfectly dried state and freshly made, it was quite free from poison. 



It appears therefore to be highly important that the initial, 

 primary or original amount of poison contained in the root should be 

 carefully ascertained, as this point is clearly seen to be of far greater 

 importance, than it is to ascertain the primary contents including the 

 quantities which can be developed as a decomposition product. That 

 there is a primary poison content is shewn by deaths which occur from 

 eating fresh roots of the bitter cassava. 



Following the matter up, it appears desirable to ascertain as 

 follows : — 



How much H C N or Prussic acid does the root of (I ) Bitter 

 Cassava, and (2) Sweet Cassava contain ? 



1. In the entire fresh root? 



2. When skin is removed? 

 .'->. In the skin of the root ? 



4. In the root without the skin ? 



5. In the juice expressed from the whole root? 



6. In the material left after expressing the juice? 



7. In expressed juice kept twenty-l'onr hours ? 



8. In the clean starch of hitter cassava left in the presence 



of water 12 and 24 hours ? 



By ascertaining the above we should be better informed as to the 

 actual poison content of Cassava roots, in the state in which it is 

 actually used as food. 



* Bulletin, No. 3, Imperial Institute. 



