CHAPTER: XVII 
DIFFUSION OF HYDROCYANIC ACID VAPOR 
N arecent report (twelfth) of the Delaware Agn- 
cultural Experiment Station, Prof. Charles L. 
Penny gives the results of a careful series of 
experiments to determine the diffusion of 
hydrocyanic acid vapor in an enclosed space, from 
which the following facts are abstracted or quoted: In 
all the diffusion experiments, in both small boxes and 
large rooms, a uniform charge of chemicals was used. 
For each cubic foot of space to be filled with 0.2 gramme 
potassium cyanide, 0.45 c. c. water, and 0.3 c. c. of 91 
per cent. sulphuric acid. 
In the box experiments the acid was allowed to 
run into the cyanide previously dissolved in water. 
In the room experiments the water and acid were 
poured together in a two-gallon earthen vessel, into 
which the cyanide was dropped. As the potassium 
cyanide was on the average of 96.7 per cent. purity, 
containing 40.14 per cent. hydrocyanic acid, it would 
have furnished 0.08028 gramme of that acid per cubic 
foot if all had been liberated. Professor Penny found, 
as he expected, that a certain amount of hydrocyanic 
acid always remained in solution in the generating 
liquid, depending on the temperature and the time of 
exposure of the latter. In the case of the box experi- 
ments this residual hydrocyanic acid varied from 2 to 
8 per cent. of the whole amount originally present, and 
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