196 FUMIGATION METHODS 



center of the room, one* near the ceiling, one near the 

 floor, and one midway between, after twenty minutes 

 practically the same amount of vapor on an average is 

 found at the ceiling and at the middle point, whereas 

 the space near the floor shows about one-third as much 

 as the other two. 



"Where the generator is covered with a box 

 that extends on all sides to the floor, the effect is 

 to throw the vapor down to the floor. The results 

 show a greater amount there than in the preceding 

 arrangement. This device is quite inadequate to 

 secure an even distribution of vapor. 



' ' In this test the generator was placed two feet 

 from a side wall at the middle point, and provided with 

 a horizontal distributing tube. The intakes were in a 

 vertical line in the center of the room. The effect of 

 this simple arrangement was surprising. After ten 

 minutes there was practically a uniform distribution of 

 acid vapor, at least in so far as the three points of 

 sampling may be taken as typical, and they seem to be 

 fairly representative. After twenty minutes there was 

 found to be but a slight change, well within the limits 

 of fluctuation in work of this sort. This simple device, 

 designed by Professor Sanderson, is shown in Chapter 

 XII. The acid vapor is distributed immediately with 

 surprising uniformity. Thus has been solved perfectly 

 the difficulty of securing an even and speedy diffusion, 

 and that, too, in a very simple and practicable way. 



; ' These results may be taken as showing fairly well 

 how much of the hydrocyanic acid can be accounted 

 for, and that is 93 per cent, of what is actually evolved, 

 or about 88 per cent, of the total amount contained in 



