506 Lord Blythswood and Mr. H. S. Allen 



Table IV. 



t (mins.) ... 



1 



U 



n 



If 



2 



2J 



2* 



£— .r(c.c.) .. 



23-5 



19-2 



15-5 



12-4 



9-9 



7-9 



6-2 



t 



2* 



3 



Si 



33 



3) 



3| 



4 



4* 





g — x 



50 



4-0 



2-6 



2-1 



17 



1-5 





The results are plotted in fig. 2. 



§ 14. This value for X is very nearly the same as the values 

 found in the previous experiments in which the pressure 

 altered as the absorption proceeded. The constancy in the 

 value of X leads to the important conclusion that, within the 

 range of the observations, the rate of absorption is practically 

 independent of the pressure. 



The rate of absorption will be different for different samples 

 of charcoal, and there is a wide field awaiting investigation 

 in the determination of this constant for various kinds of 

 charcoal, and what is more important the determination of 

 the rate of absorption of pure gases by a particular sample 

 of charcoal. 



(ii.) Absorption of a Limited Volume of Air by a 

 large quantity of Charcoal. 



§ 15, In order to trace the course of the absorption at low 

 pressures, a charcoal bulb w T as sealed to a McLeod gauge and 

 barometer-tube. The capacity of the McLeod gauge was 

 2324 c.c., the capillary portion being 10 cm. long and having 

 a capacity 0*125 c.c The internal volume of the barometer- 

 tube and the connecting tubes was estimated at 142 c.c. 



The charcoal bulb first used contained about 65 grams of 

 charcoal, its volume being 200 c.c. 



The vessel containing liquid air was brought up underneath 

 the charcoal bulb and gradually raised until the whole w T as 

 immersed. This process generally occupied about two 

 minutes. At the end of this time, readings of the height of 

 the mercury column were commenced and noted at everv 

 half minute, until the motion became too slow to give trust- 

 worthy results. In ten minutes the difference between the 

 height of this column and that of the barometer was less 

 than one millimetre. 



No readings of the McLeod gauge could be obtained until 

 about half an hour after the commencement of the experiment. 



