DIFFUSION OF HYDROCYANIC ACID VAPOR 1 91 



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, i.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 



