PHYSICS: LEMON AND BLODGETT 
289 
THE RELATIVE ADSORPTLON OF MLXTURES OF OXYGEN AND 
NLTROGEN IN COCOANUT SHELL CHARCOAL^ 
By Harvey B. Lemon and Kathryn Blodgett 
Ryerson Physical Laboratory, University of Chicago 
Communicated by A. A. Michelson, May 19, 1919 
It is a well known fact that gases are adsorbed in charcoal with rates and 
in total amounts that vary in a manner closely related to the boiling tempera- 
tures of the gases. A mixture of gases may accordingly have its proportions 
entirely altered by adsorption. This is the principle of the method of Gehloff 
for the isolation of atmospheric neon.^ Dewar has mentioned it as a conven- 
ient means of extracting a high percentage of oxygen from the air.^ A quan- 
titative knowledge of the manner in which the presence of one gas to satura- 
tion affects the adsorption of another is of great importance since these are 
the conditions of use under which charcoal has sprung into prominence in 
modern warfare. 
The experiments herein described deal with the relative adsorption of mix- 
tures of oxygen and nitrogen in varying proportions by a highly activated 
charcoal prepared in the manner described in a previous report by one of 
the writers. Relatively large amounts of charcoal are employed with respect to 
the quantity of gas used so that saturation is in all cases reached in the course 
of thirty minutes or so. The charcoal which weighed 6.5 grams when satu- 
rated with dry air at 20° and 750 mm. pressure was contained in Pyrex glass 
bulbs which could be outgassed by a diffusion pump. Outgassing was for 
four and a quarter hours at 582°C. After outgassing the tubes were immersed 
in liquid air of definite age and temperature. While immersed they were 
exposed to the given gas mixture contained in a constant volume of 975 cc. 
The initial pressure of the mixture was 73.95 cm. and observations were taken 
of it at intervals while the adsorption was going on and until it had ceased to 
fall. A barometer and McLeod gauge formed a part of the above mentioned 
volume for this purpose. 
In figure 1 is given the data in graphical form where log p in cm. is plotted 
against log t in minutes after the adsorption began. The same sample always 
is included in this record, two others were used as controls. It is noted that 
the logarithm of the pressure reached by saturation is almost in a linear rela- 
tion with the percentage of oxygen in the mixture. 
This is shown in figure 2 as the line NO. Here log final pressure is plotted 
against percentage of oxygen. 
The other lines of this diagram NN^ and 00' show the final pressures of 
amounts of pure nitrogen and pure oxygen equal to those existing in the mix- 
ture at corresponding values of abscissa but adsorbed separately. 
