DIFFUSION OF HYDROCYANIC ACID VAPOR 193 
soil. Hence, in a box resting on soil, about 62 per 
cent. as much acid vapor is available as in a closed 
box. It would seem necessary, then, in work of this 
sort over soil to use nearly twice as much cyanide and 
other reagents as in a closed box.”’ 
Diffusion in large room.—‘‘ Experiments were made 
in a rectangular room of which the horizontal dimen- 
sions were 20 feet 9 inches by 1g feet 1 inch, and the 
height ro feet 11 inches, and which included 4,332 
cubic feet. The walls and ceiling were plastered and 
the floor was of boards; there were four windows and 
three doors. The crevices were stopped as far as 
possible, but necessarily the room was far from air- 
tight. Samples of air were taken simultaneously from 
three different points within the room. ‘The position 
of two of these points and also of the generator was 
changed several times in order to study the diffusion 
in different places. The generator was a glazed stone- 
ware vessel 8 inches in diameter and 15 inches high. 
The charge of reagents in the case of the room-experi- 
ments was the same per cubic foot as in the case of the 
box-experiments, in the former amounting to 866.5 
grammes cyanide, 1,300 c. c. of concentrated sulfuric 
acid, and 1,950 c. c. of water. The water was poured 
into the generator, the acid was then poured into the 
water, and immediately thereafter the cyanide, wrap- 
ped in paper, was dropped by means.of a string, into 
the acid mixture.’’ 
General results.—‘‘After ten niinutes of diffusion 
time, with the generator in one corner on the floor, the 
amount of vapor in the center of the room at the ceiling 
