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CHAPTER XVIII 

 DIFFUSION OF HYDROCYANIC ACID VAPOR 



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N a recent report (twelfth) of the Delaware Agri- 

 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 o. 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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