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 



