1019] on Liquid Oxygen in Warfare 615 



came out at 1120. The correspondiii*^ value for carbonic acid (taken 

 at a mucli lower temperature) is lo5(), Avhile oxygen and nitrogen 

 are of tbe order of 5(»0. Hence practically all air gases had been 

 removed at this stage, while carbonic acid alone was being evolved. 

 This is a good indication of the clean state of the charcoal at that 

 time, a conclusion which was supported by separate examinations of 

 the gases evolved at successive stages under high exhaust from heated 

 charcoal. 



VERY ABSORPTIVE CHARCOAL, CALLED ACTIVATED CHARCOAL. 



In the early days of the use of cooled charcoal for high vacuum 

 work, it was soon recognised that good efficiency was only obtained 

 when the charcoal was carefully prepared, free from volatile organic 

 and inorganic constituents. lu 1011 chemically prepared cocoanut 

 charcoal (previously treated at a red heat with chlorine and then with 

 hydrogen) was continuously heated in an electric furnace at .S00° to 

 850' C. Periodical tests of the absorptive power proved that this 

 quality rose steadily for two or more days. Values for different 

 gases at atmospheric pressure are given in the following table :— 



Thus time is an important element in the preparation of such 

 charcoal. A sample at the boiling-point of hydrogen (20*4° Abs.) 

 absorbed 397 cc, the pressure on saturation being only 2*2 mm. 

 Similar improvement takes place in ordinary unpurified cocoanut 

 charcoal after prolonged heating. 



EFFICIENCY OF VACUU3I CONTAINERS : CONTRIBUTORY CAUSES. 

 LOSSES DUE TO NECK APERTURE IN VACUU3I VESSELS. 



The proportionate loss due to the convection and temperature 

 gradient in the neck aperture was estimated in several cases. 

 Comparisons were made of vessels of similar dimensions but with 



* Proc. Roy. Inst., xviii. 752. 



