PHYSICS: H. B. LEMON 
291 
If a mixture of the two gases is adsorbed then as above the final pressure 
reached is considerably higher. 
1 This article is published with the approval of Major General William L. Siebert, Director 
Chemical Warfare Service, U. S. A. 
2 Gehloff, Leipzig, Physik, Zs., 7, 1913, (838). 
3 Dewar, London, Proc. Roy. Soc, 74, 1904, (122). 
4 Bergter, Leipzig, Ann. Physik, 37, 1912, (606). 
VARIATIONS, DUE TO HEAT TREATMENT, IN THE RATE OF 
ADSORPTION OF AIR BY COCOANUT SHELL CHARCOAL^ 
By Harvey B. Lemon 
Ryerson Physical Laboratory, University of Chicago 
Communicated by A. A. Michelson, May 19, 1919 
This paper is an abstract of results of experiments most of which were 
performed prior to January 1918, but the pubhcation of which has been withheld 
during the war.^ 
If charcoal contained in a bulb of glass or iron is heated to 600°C for about 
four hours and the gases which are freed pumped off into the low vacuum 
furnished by a mercury diffusion pump,^ it is a well known fact that when the 
charcoal is then subsequently cooled to the temperature of liquid air it pos- 
sesses a tremendous capacity for adsorbing gas, and will adsorb it at an ex- 
tremely rapid rate. This adsorption power, however, has been found to be 
very different with different specimens of charcoal made from the same ma- 
terial, in this case cocoanut shell, and also to be very different when a single 
sample is used repeatedly. The magnitude of these differences is of no mean 
order but may be as large as the ratio of 10,000 : 1. It is shown in what fol- 
lows that the heat treatment of the specimen during carbonization and also 
during successive 'outgassings' is a decisive factor in the control of the effi- 
ciency of the material as an adsorbent. 
The experimental method was one of extreme simplicity. The shell was 
carbonized in an enclosed electric furnace having a vent for escape of gases 
and vapors. The temperature was indicated on a Leeds Northrup potential 
point resistance thermometer. The charcoal was then ground up to particles 
of from 1 to 3 mm. diameter and cleansed from all smaller fragments and dust. 
A definite weight (25.7 grams in most of the experiments, determined in dry 
air with which the charcoal was saturated) was sealed up in a tube of iron, 
quartz or Pyrex glass depending on the temperatures to be subsequently 
used. From this tube cocks communicated, (1) to the diffusion pump, and 
(2) to a fixed volume that could be filled with dry air at any desired pressure. 
This fixed volume included a McLeod gauge and a mercury barometer column 
so that the pressure in it could be read to within a few per cent over a range 
