CONTROL CONDITIONS, ETC. 



19 



To determine the increase in the quantity of moisture mixed with 

 the air due to the generation of the different quantities of the gas, 

 a psvehrometer was fitted inside the box. This instrument was of 

 the pattern used by the Weather Bureau. The handle was removed 

 and the frame fastened to a hollow spindle which extended through 

 the side of the box. 



The spindle was at- 

 tached to the shaft of 

 a centrifuge in order 

 to whirl the psv- 

 ehrometer inside the 

 box (see fig. 3). By 

 means of the hollow 

 spindle and a small 

 rubber tubing leading 

 to the wet bulb, just 

 the sufficient quantity 

 of moisture could be 

 applied to it. The 

 thermometers could 

 be read through the 

 glass door. 



The gas generator 

 consisted of a beaker 

 8 inches deep and 

 about 4 inches in 

 diameter. This was 

 placed in a large gal- 



Fig. 2. 



Sketch showing the side view of the fumigating box 

 and thp arrangement of the drawers. 



vanized-iron pail in 



order to catch any 



overflow. In the experiments the generator was placed on the floor 



of the box. in the center, with the potassium permanganate crystals 



in it, the formalin poured upon them, and the door closed. There 



was sufficient time to employ this means of mixing the reagents as 



the reaction did not begin immediately. 



CONTROL CONDITIONS AND EXPLANATION OF ARBITRARY UNITS. 



It is thought that owing to the simplicity and efficacy of the 

 formalin-permanganate method of evolving the formaldehyde gas 

 this method will be the one which will be adopted in practical work. 



No determination of the quantities of formaldehyde in the atmos- 

 phere of the box during the experiments was made. The data, given 

 in terms of the cubic centimeters of formalin of known strength 

 used per 1,000 cubic feet of air space, will therefore be as valuable as 

 if given in terms of the quantity of formaldehyde per cubic foot. 



171 



