ON THE POISONOUS ACTION OF DI-CYANOGEN. 
35 
the usual way by heating cyanide of mercury ; the aqueous 
solution, obtained by passing the washed gas in water, was 
analyzed in the following way:—20 c.c. of that solution were 
mixed with 2—5 c.c. of concentrated soda lye, and when, after 
some time, the cyanogen smell had disappeared, a silver-nitrate 
solution was added and afterwards supersaturated with nitric 
acid. The washed cyanide of silver was weighed on a dried 
filter. The calculated quantity of cyanogen was multiplied by 
2, because half of the di-cyanogen having been converted into 
sodium cyanate was excluded in this determination. Thus 
was found in one case the percentage of cyanogen 0.37%, in 
another preparation 0.64% and in the. third 0.39%. These 
solutions were kept cool, generally below io°C, and were used 
only during the following four or five days for experiments, 1 ) 
because the solutions of di-cyanogen undergo a gradual decom¬ 
position. In comparing the di-cyanogen solutions with those 
of hydrocyanic acid, solutions of equal strength have been used, 
starting with the fact that two molecules of hydrocyanic acid 
(54) act upon two aldehyde-groups, while one molecule of di¬ 
cyanogen (52) reacts upon two amido-groups. 
Action of Di-cyanogen upon Microbes. 
To 50 c.c. of the cyanogen-solution of the dilution of 1 : 5000 
a drop of putrid meat-water was added, and after standing 24 
hours, a sterilized peptone-solution was infected from this aqueous 
liquid. After standing 8 days there was no bacterial development 
and no putrid smell perceptible. In the control experiment, in 
which water was used instead the cyanogen solution, after 3 days 
a strong development of bacteria with a putrid smell was observed. 
In the second experiment in which was compared di-cyanogen 
and hydrocyanic acid both in dilution of 1 : 10000 a bacterial 
developement was observed in both cases, but not till 4 days 
later than in the control case, which seems to indicate that the 
bacilli themselves were killed but not the spores. In the third 
experiment some peas were placed in a cyanogen solution and in 
a hydrocyanic acid solution of equal strength, both of them in 
a dilution of 1: 5000. After three days a very strong develop- 
1) The Nessler’s test showed us, that during the time, we experimented with 
these solutions, no decomposition with formation of NH 3 could be observed. 
