HISTORICAL NOTE. 7 



The following method is a modification by Carmody of that used by 

 Francis: 



The fresh tuber is cut in thin slices and allowed to stand in an equal weight of 

 water in a closed vessel overnight. The liquid is decanted and an aliquot j>ortion 

 distilled, the hydrocyanic acid in the distillate being titrated with a silver salt. The 

 sliced tubers are repeatedly treated with portions of fresh water, as many as five 

 determinations may be made, and the sum of the results is reckoned as the total 

 hydrocyanic acid. 



In the use'ofthis method it was observed that the first extraction 

 generally yielded but a small portion of the total amount of acid and, 

 further, that the tubers continued as long as observed to give off 

 hydrocyanic acid upon continued digestion with fresh water. In 

 Jamaica" the Government analyst (Cousins) continued this work, and 

 writes as follows on this point: 



For seven days a nearly uniform production of hydrocyanic acid took place when 

 the sliced tubers were placed in water. The water was poured off every day, the 

 hydrocyanic acid estimated, and a fresh supply added. Finally hydrochloric acid 

 was used and this eliminated nearly the whole of the hydrocyanic acid. We have 

 now ascertained that the total hydrocyanic acid may be estimated by treating the 

 cassava with hydrochloric acid and distilling with steam. 



In a report published in the Bulletin of tbe Imperial Institute 6 in 

 1903 on the investigation of poisonous fodders and food grains, the 

 following observations are made: 



Lotus arabicus. * * * It was ascertained that the toxicity was due to the pro- 

 duction of prussic acid, when the plant was moistened with water, as the result of 

 the interaction of a glueoside and an enzyme occurring together in its cells. The 

 glucoside (lolusin) was obtained in a pure state and shown to be a derivative of a 

 yellow coloring matter (lotoflamn) , the latter, in addition to dextrose and prussic 

 acid, being produced when lotusin is hydrolyzed, either by the action of the enzyme 

 (lotase) present in the plant, or by boiling it with dilute mineral acids. * * * 



* * * The amount of prussic acid obtainable from Lotus arabicus is considerable 

 and varies from 0.26 per cent in the case of young plants to 0.32 per cent in the case 

 of those almost mature, when the yield of acid reaches the maximum. 



The statement is further made in regard to cassava (Manihot utillis- 

 sima, that "this plant also contains a cyanogenetic glucoside, which, 

 in its decomposition, furnishes the prussic acid hitherto generally 

 believed to exist free in the tuber." 



From a Trinidad report the following note is taken having refer- 

 ence to this work: 



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 



"Department of Agriculture, vol. 2, pts. 6 and 7. 

 6 Vol. 1, pp. 13 and 15. 



c Trinidad, Botanical Department, Bulletin of Miscellaneous Information, No. 41, 

 January, 1904, p. 26. 



