134 



Journal of Agrictdtural Research 



Vol. XXI. No. 3 



mgm. of hydrocyanic acid; N/o.oi sulphuric acid, 1 1 mgm. ; and in N/ 0.02 

 sulphuric acid, 4 mgm. On August 2 three samples were prepared and 

 digested in N/i vSulphuric acid; in N/0.2 sulphuric acid; and in N/0.05 

 sulphuric acid. Just before distillation, sodium hydroxid was added to 

 almost neutral reaction. From the N/0.05 sulphuric acid 18 mgm. of 

 hydrocyanic acid were obtained; a trace was obtained from the N/0.2, 

 and none from normal. The weakest of the acid solutions gave no 

 more than water alone. The smaller amounts obtained from the water 

 treatments at the later date is in accord with the general observation 

 that as the season advanced less hydrocyanic acid was present. It 

 was planned to determine the exact hydrogen-ion concentration at 

 which the hydrocyanic acid is most easily split off, but time did not 

 permit. It is hoped that this may be determined in the future. 



It was shown in connection with the hot-water treatment that when 

 grass dries the hydrocyanic acid is changed into a free condition, so that 

 simply adding hot water and distilling will drive off the hydrocyanic acid. 

 To see if more would be driven off if acid was also present the following 

 experiment was performed. Six samples of leaves were placed in the 

 open in clear weather from 9 a. m. till 9 a. m. the next day. Then they 

 were macerated and digested in water and in different concentrations of 

 sulphuric acid. The results are given in Table XII. 



Table XII. — Effect of acid solutions in formation of hydrocyanic acid 



HiS04 added. 



Nil... 

 NI0.2. 

 NI0.05 



HCN ob- 

 tained. 



Mgm. 



H2S04 added. 



NI0.O2 

 NJO.OI 



Water. 



HCN ob 

 tained. 



Mgm. 



Trace. 

 10 

 18 



Thus, it appears that sulphuric acid is unfavorable to the liberation of 

 the hydrocyanic acid even in the wilted material. 



To determine whether hot sulphuric acid would liberate the hydro- 

 cyanic acid, hot water and sulphuric acid of varying normalities were 

 added to green material immediately after maceration on July 16. The 

 results are shown in Table XIII. 



Table XIII. — Effect of hot sulphuric acid on formation of hydrocyanic acid 



H2SO4 added. 



Nil.. 

 NI0.5 

 NI0.2 

 NIo.i 



HON ob- 

 tained. 



Mgm. 



Trace. 



Trace . 



H2SO4 added. 



NI0.05 



NI0.02 



NIo.oi. .. . 

 Hot water 



HCN ob- 

 tained. 



Mgm. 



O 



Trace. 

 Trace. 



