CASSAVA: 



ITS CONTENT OF HYDROCYANIC ACID AND STARCH, 

 AND OTHER PROPERTIES. 



HISTORICAL NOTE ON PREVIOUS INVESTIGATIONS. 



The presence of hydrocyanic acid (commonly called prussic acid) in 

 cassava, and the resultant danger in eating this root unless it has been 

 especiall} 7 prepared, have restricted its use in the countries where it 

 is indigenous to that of a human food. For centuries it has been an 

 important food among the South American Indians, who peel and 

 cook all varieties. This preparation eliminates the hydrocyanic acid, 

 making a nutritious human food, while the unpeeled raw product may 

 produce fatal results. For this reason it is not utilized in feeding 

 stock, though it is a most valuable forage product except for the possi- 

 bilit\ T of its being poisonous. In this country it is considered pri- 

 marily as a forage product; secondly, as a source of commercial starch, 

 glucose, and alcohol, and, thirdly, possibly as a human food. 



BITTER AND SWEET VARIETIES. 



Owing to the variation in content of hydrocyanic acid, the cassava 

 has been divided into sweet and bitter varieties that is, varieties 

 which do not contain enough prussic acid to be dangerous are called 

 sweet and the others bitter. The chemical work that has been done 

 previously is so limited that it is merely suggestive of the lines of 

 research that should be pursued. A review of the literature of the 

 subject shows that it is not definitely known that the same variety is 

 at all times either sweet or bitter. 



In 1877 the Government analyst for Trinidad (Francis) examined 

 some varieties of cassava and reported that the average percentage of 

 hydrocyanic acid in the sweet varieties was 0.016, and in the bitter 

 0.027. The subject was not again considered for some years, and only 

 within the past five years has the work been carried further by in\ < - 

 tigations at the Government stations in Trinidad and Jamaica. A 

 series of results was obtained on the Trinidad varieties by the Govern- 

 ment analyst at that station (Carmody). He reports the mean per- 

 centage of hydrocyanic acid in the sweet varieties examined as 0.010 

 and in the bitter 0.022. These analyses were made by a modification 

 of the method used by Francis, and the results obtained by the two 



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