DIFFUSION OF HYDROCYANIC ACID VAPOR 189 
taken, or the ‘‘intake,’’ were in one case at the same 
end of the box, in the other case at opposite ends. 
The ‘‘diffusion time’’ was the time elapsed between 
the liberation of the vapor and the taking of the 
sample. 
‘‘It appears,’’ says Professor Penny, ‘‘from the 
results obtained that immediately after the generation 
of the hydrocyanic acid, as would be expected, there 
is an excess of it around the generator, that this excess 
disappears within two minutes, leaving but one-third 
the normal quantity at that point, and that at the oppo- 
site end there is a still greater excess, viz., two and 
one-half times the normal amount; that this latter 
excess in turn rapidly falls and the vapor around the 
generator again increases in amount, so that there is a 
tendency toward equilibrium, though considerably 
over twenty minutes would be required to approximate 
perfect equilibrium. Hence, for the duration of a 
practical trial by far the greater amount of vapor 
would be in the end of the box farthest from the gen- 
erator. 
‘“The fluctuations between repeated trials under 
similar circumstances are relatively slight; that is, 
uniformity is the rule. What is found true in one 
instance is, with due regard to the general character 
of the work which precludes extreme accuracy, sub- 
stantially true in similar instances. This may be 
attributable in part to the double walled and paper- 
lined box, which reduced the influence of air currents 
to a minimum.’’ 
Diffusion in box.—‘‘ The following results in the 
second experiment were obtained with a box of 29 
b 
