1905.] 



on New Low Temperature Phenome 



iia. 



181 



and representing a greater surface for condensation, are the greater 

 absorbers. Nevertheless, we must not forget to notice that the 

 aflBnities between charcoal and different gases are not the same, and 

 that these will seriously modify any results derived from mere 



geometrical considerations. 



Thermal Evolution and Absorption of Gases hj Charcoal 

 at Low Temperatures.* 



Saussure first observed and roughly noted that the absorption of 

 gases by charcoal at the ordinary temperature gave rise to a con- 

 siderable evolution of heat. The liquid air and hydrogen calori- 

 meters can be easily arranged to afford an exact measure of the 

 quantities of heat thus given up by the condensation of different 

 gases in charcoal. For this purpose a small glass bulb C, contain- 



FlG. 1. 



ing from half a gramme to a gramme of charcoal, has a long 

 narrow tube C attached, so that it can be immersed in the liquid 

 oxygen, or air in the calorimeter A B, while still allowing a 

 part of the tube to project above the cork A. The calorimeter 

 is then inserted in a large vacuum vessel H, containing two or 

 three litres of liquid oxygen or air, as the case may be, and kept 

 in its place by a loose stuffing of cotton wool. In order to dry 

 and cool the entering gas (which, in my experiments, did not exceed 



* Proc. Hoy. Soc, 1904. \ 



