194 FUMIGATION METHODS 



was 'about normal, with a trifling excess. On the floor 

 by the side of the generator there was none at all, or 

 only a mere trace. On the floor diagonally opposite 

 to the generator it averages, with rather wide fluctua- 

 tions, 73 per cent, of the normal. After 20 minutes 

 the center at the ceiling showed a trifling loss, the 

 point on the floor next to the generator showed 27 per 

 cent, of the normal, and the point on the floor in the 

 opposite corner showed 94 per cent. After 30 minutes 

 these figures were not greatly changed for the first and 

 the last, while for the second point, that next to the 

 generator, the vapor is 51 per cent, of the normal, 

 nearly double its amount after 20 minutes. After an 

 hour the diffusion is practically complete, the amount 

 of vapor at the three points being 52, 44 and 44 per 

 cent, of the normal, while after four hours and a half 

 it is 25, 24 and 21 per cent., respectively. 



* ' It is apparent that there is a rapid loss in the total 

 amount of acid vapor from the room as a whole. This 

 loss cannot be easily estimated until there is practically 

 complete diffusion, as the average of the three points 

 would not necessarily, nor even probably, give the 

 average for the whole room. It would seem, then, 

 after one hour there is a trifle less than one-half of the 

 normal amount of acid vapor in the room, and after 

 four and one-half hours a trifle less than one-quarter. 

 The rate of loss is probably greater through a plastered 

 wall than through one of boards, and it would doubt- 

 less require a special air-tight construction of a room 

 to reduce this rate very considerably. Hence, the con- 

 stant loss must be borne in mind in considering the 

 completeness of the diffusion. 



