Oct. IS. I92I Hydrocyanic Acid in Sudan Grass 133 



obtained was not greater when the grass was wilted for a longer time. 

 Less hydrocyanic acid is obtained from grass that is kept moist while 

 in the sun than from grass that is allowed to dry rapidly. According 

 to Ravenna and Zamorani ^ the nitrogen passes through the following 

 stages in the plant: Nitrate -^ hydrocyanic acid — > amino substance 

 — ^ protein substance. According to this theory the cells which con- 

 tinue to be active use the hydrocyanic acid for the building of protein 

 substance, and as more nitrates from the soil are not supplied for man- 

 ufacture of more hydrocyanic acid, the potential amount present when 

 the plant is cut is soon exhausted. 



When the grass was dried slowly in the shade the hydrocyanic acid 

 disappeared more slowly than when it was dried in the sun, and the 

 amount obtained from the hot-water treatment became approximately 

 equal to that obtained from the longer digestion in cold water. This 

 seems to mean that when the plant wilts the hydrocyanic acid is split 

 off from glucocids and held in such loose combination that it can be 

 set free by hot water and that practically all the hydrocyanic acid is in 

 such combination, since additional amounts can not be obtained by 

 further digestion. Splitting off begins as soon as the plant is cut. 

 Determinations made on grass kept moist in the shade appear to show 

 that after 24 hours all the hydrocyanic acid not otherwise used by the 

 cells is in such a condition that it is soluble in water. 



In the test in which the grass was frosted the hydrocyanic acid dis- 

 appeared very rapidly, though the results were not very consistent. 



EFFECT OF ACIDS 



On June 24 a sample of grass was placed in a flask after maceration, 

 covered with water, and sulphuric acid was added to acid reaction. 

 After it was digested and distilled as usual only a trace of hydrocyanic 

 acid was obtained. From a sample of like material and similarly 

 treated, except that no acid was added, 27 mgm. were obtained. On 

 June 29 this experiment was repeated with the result that 8 mgm. 

 were obtained when acid was used and 26 mgm. when it was not used. 

 On June 30, i and 28 mgm. were obtained by these respective treat- 

 ments. These experiments clearly indicate that the presence of acid 

 has a very importance influence on the amount of hydrocyanic acid that 

 may be obtained. To test the effect of the amount of acid used, four 

 samples were prepared on July 14 and digested overnight in the fol- 

 lowing: (i) water; (2) N/o.i sulphuric acid (HjSOJ; (3) N/0.2 sul- 

 phuric acid; (4) N/i sulphuric acid. No hydrocyanic acid was ob- 

 tained from any of the treatments with sulphuric acid, whereas the 

 water digestion gave 30 mgm. On August 4 this experiment was 

 repeated, using a weaker acid solution. Digestion in water gave 10 



1 Ravenna, C., and Zamorani, M. nuove ricerche sdlla funzione fisiologica dell' acido cian- 

 iDRico NEL SORGHUM VULGARE. In Atti R. Accad. Lincei, Rend. Cl. Sci. Fis., Mat e Nat., v i8, sem. 2, 

 no. 8, p. 283-287. 1909. Abstract in Chem. Abs. v. 5, no. 6, p. 1123. 1911. 



