38 
ON THE POISONOUS ACTION OF DI-CYANOGEN. 
the fermentative action of yeast without killing it. But we have 
found further that if the hydrocyanic acid of the same strength 
remains in contact with yeast for more than one day, or if, in¬ 
stead of hydrocyanic acid solution of i : 1000 a stronger solution 
is applied, as i : 400, it will damage the fermentative activity so 
much that afterwards the yeast produces only a very faint fer¬ 
mentation. It seems to us that only a few yeast cells escaped 
death under these circumstances. We have found furthermore 
that 2 day’s contact with hydrocyanic acid in a dilution of 1: 
5000 with frequent shaking, will kill almost all the cells, so 
that after pouring off the hydrocyanic acid, the yeast being 
shaken up in sterilized Pasteur’s solution showed only very 
slight indications of fermentative action. 
If we compare this result with our further observation that 
the fermentative action is not suppressed when we add to the mix¬ 
ture of yeast and Pasteur’s solution prussic acid in the proportion 
of i : 5000, we are led to the conclusion that in all probability 
the hydrocyanic acid upon entering the yeast cell undergoes 
decomposition before it can act poisonously. If, however, the 
yeast is not in fermenting activity, the entering hydrocyanic acid 
is not so quickly decomposed, and therefore acts as a slow poison. 
It may perhaps be assumed that the change consists in the addi¬ 
tion of H 2 0 , forming thereby formamid : 
HCN + H.O = HCl^tv 
Action of Di-cyanogen and Prussic Acid 
upon Algae. 
If threads of Spirogyra communis are treated with a solution 
of di-cyanogen of 0.39%, instantaneous death with contraction and 
turbidity of the cytoplasm is observed. In solutions of di-cyano¬ 
gen, respectively hydrocyanic acid of 1 : 1000, no noxious effect 
was seen after 30 minutes, but after 4 hours most of the cells in 
the cyanogen solution were killed; in the prussic acid solution, 
however, a much smaller proportion of cells. After 15 hours, all 
the cells were dead in both cases. Also solutions of 1 : 10000 
exerted a poisonous influence after several days 1 ), but it could 
1) In another case the noxious effects of the two substances in the same dilution 
were observed after 20 hours ; on treating with very dilute methyl violet the cells 
of the algae in the cyanogen were all coloured, but of those in the prussic acid some 
cells not, showing these were still alive. 
