DIFFUSION OF HYDROCYANIC ACID VAPOR  IQI 
sion time the amount of hydrocyanic acid vapor at a 
given point may be as little as 23 per cent. of the 
normal and as high as 272 per cent., or, with the same 
quantity of reagents per cubic foot and in the same 
box, at one point there may be twelve times as much 
acid vapor as at another. Of course this inequality 
would not continue long, but it does exist in certain 
cases for a time. Hence it must be apparent, if we 
rely on spontaneous diffusion, that the amount of 
cyanide used per cubic foot is no guarantee on the one 
hand of sufficient acid vapor to do the work, nor, on 
the other, of too little to injure plants.’’ 
Mechanical mixer.—In these tests a mechanical 
mixer was used in the box of twenty-nine cubic feet 
capacity. This device consisted of a fan on a hori- 
zontal axis which passed through the sides of the box 
and was turned by means of a crank from the outside. 
The results showed a remarkable uniformity for work 
of this general character, varying from 68 per cent. to 
74 per cent. of the normal. ‘The average is 72 per 
cent., and this may be taken as the true measure of 
efficiency under these conditions, z.e., with a similar 
size and proportion of box and equal loss from leakage. 
As about 5 per cent. of the total hydrocyanic acid re- 
mains in solution in the generator, and of the 95 per 
cent. evolved 72 per cent. is uniformly diffused, it would 
follow that about 68 per cent. of the total hydrocyanic 
acid gas originally present in the cyanide, or approxi- 
mately two-thirds, becomes efficient by uniform diffu- 
sion throughout the box. Of the remaining 32 per 
cent., aside from the 5 per cent. left in the generator, 
the balance, 27 per cent., is to be accounted for by 
