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. 



