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 percent. 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. 
‘‘Tt 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. 
