286 Mr. W. R Dunstan and Dr. T. A. Henry. [June 10, 



that when crushed, moistened with water and distilled, it furnished 

 a distillate containing hydrocyanic acid and acetone, and this author 

 drew attention to the fact that he had observed the simultaneous 

 production of acetone and hydrocyanic acid in several other plants, 

 notably in Manihot utilissima, which furnishes the cassava of the West 

 Indies. 



The observations of Boname' and of van Romburgh suggested to us 

 the advisability of examining Pois d'Achery in continuation of the 

 investigation of the chemical origin of the prussic acid of plants, on 

 which we have been engaged for some time. For the material, which 

 is somewhat difficult to procure, we are indebted to M. Boname 1 , who, 

 at the instance of the Colonial Office, collected in Mauritius and 

 forwarded to us two large samples of the beans. 



Preliminary Observations. 



When a few of the beans are powdered and moistened with cold 

 water, the odour of hydrocyanic acid becomes perceptible in a few 

 minutes. If boiling water is used and the vessel is immediately closed 

 and allowed to cool, no odour of prussic acid is perceptible, and no 

 evidence of its production can be obtained by the application cf the 

 usual test to distillates from such preparations. These observations 

 confirm those recorded by Bonam^,* and indicate that the pro- 

 duction of hydrocyanic acid is connected with the action of an 

 enzyme. 



Estimation of the Amount of Hydrocyanic Acid Produced. 



It was found to be impossible to estimate the amount of hydro- 

 cyanic acid, obtainable from a weighed quantity of the powdered 

 beans, by soaking the powder in water and subsequent distillation, 

 owing to the continuous frothing over of the liquid. This difficulty, 

 which was experienced by previous workers, was avoided by extracting 

 in a Soxhlet percolator a weighed quantity of the finely ground seeds 

 with 90 per cent, alcohol, distilling off the solvent, hydrolysing the 

 glucoside contained in the residue by distilling with dilute sulphuric 

 acid until hydrocyanic acid no longer appeared in the distillate, and 

 then estimating, by one of the usual methods, the amount of prussic 

 acid thus produced. 



Owing to the production of some volatile reducing substance, which 

 was carried over with the hydrocyanic acid in this process, it was 

 difficult to titrate the acid volumetrically by Liebig's method, which 

 we have employed in previous cases, since the end reaction was 

 obscured by the formation of a slight precipitate of reduced silver. 



* Loc. dt. 



