156 



Drs. Dunstan, Henry, and Auld. 



[Apr. 11, 



of the various consignments of dried bitter cassava root and rind we have 

 received. 



Isolation of the Glucoside. 



Estimations of the amounts of hydrocyanic acid obtainable from the dried 

 sliced root and from the dried rind of bitter cassava were made by the 

 method we have generally used for this purpose, viz., the complete extraction 

 of the ground material with 90 per cent, alcohol and the hydrolysis of the 

 glucoside contained in the residue left after distilling off the alcohol from 

 this extract. This hydrolysis was accomplished by dissolving the residue 

 in water and distilling the liquid almost to dryness after the addition of 

 a few cubic centimetres of hydrochloric acid, the hydrocyanic acid in the 

 distillate being titrated with silver nitrate solution by Liebig's method.* 

 In this way it was ascertained that the dried sliced root yielded about 0"009 

 per cent, and the dried rind of the bitter cassava O035 per cent, of acid. 

 These, results agree fairly well with the quantities of the acid found by 

 Francis, but the last is somewhat higher than those recorded by Carmody,f 

 which ranged from 0"0113 to 0*0238 per cent. Owing to the impossibility 

 of importing fresh roots, we have not been able to make any useful 

 determination of the amount of acid obtainable from fresh roots of " sweet " 

 and " bitter " cassava or from different parts of such roots, but we understand 

 that investigations of this kind are now being carried out in India by 

 Dr. J. W. Leather, Government Agricultural Chemist.j 



For the isolation of the glucoside the finely-ground cassava rind was 

 completely extracted by percolation with 90 per cent, of alcohol. The 

 solvent was distilled from the extract, the syrupy residue slightly diluted 

 with water, filtered from the precipitated resinous and oily matters, and the 

 filtrate decolorised by adding lead acetate, filtering out the precipitated lead 

 compound of the colouring matter, and removing the excess of lead from the 

 filtrate by treatment with sulphuretted hydrogen. This purified extract was 

 then evaporated almost to dryness under reduced pressure at the ordinary 

 temperature. The light brown syrup so obtained showed no tendency to 

 crystallise even after long standing. It was therefore dissolved in alcohol 

 and the solution poured into excess of ether. The matter precipitated by the 

 ether consisted principally of dextrose. The decanted liquid was again 

 evaporated nearly to dryness, the residue dissolved in alcohol, and the 

 precipitation with excess of ether repeated. After each operation the 



* Compare ' Phil. Trans.,' 1901, B, vol. 194, p. 515 ; 1902, A, vol. 199, p. 399 ; ' Roy. 

 Soc. Proc.,' 1904, vol. 72, p. 285. 

 t Loc. cit. 



% Annual Report of the Imperial Department of Agriculture, 1905. 



