298 -/. De-war — Thermal Evolution of Gases. 



I. II. III. 



Volume Volume Heat evolved, 



absorbed. absorbed. Grain - 



0° C. -185° C. calories. 



Hydrogen _ 4 c.c. 135 c.c. 9'3 



Nitrogen 15 " 155 " - 25*5 



Oxygen _. 18 " 230 " 34*0 



Argon 12 " 175 " 25"0 



Helium 2 '" 15 " 2-0 



Electrolytic gas ___. 12 " 150 " 17-0 



Carbonic oxide and oxy- 

 gen 30 " 195 " 34-5 



Carbonic oxide 21 " 190 " 27*5 



In all cases, it will be observed, the amount of gas occluded 

 has been greatly increased at the low temperature, and the 

 degree of condensation is generally such as we should antici- 

 pate from the known physical constants of the gases. The 

 amount of heat evolved is so great as to be in excess of that 

 required for liquefaction in the case of gases like hydrogen, 

 nitrogen, and oxygen. The heat produced when successive 

 fractions of the volume of gas required for saturation are 

 absorbed has yet to be determined. In the time required for 

 the absorption no measureable amount of chemical combination 

 was effected between mixtures of hydrogen and oxygen or 

 carbonic oxide and oxygen in the pores of the charcoal. 



Such experiments must be extended to the use of platinized 

 charcoal and other catalytic agents. 



Perhaps the most striking result is the great difference in 

 properties exhibited by helium. While resembling the other 

 gases in showing increased absorption at the temperature of 

 liquid air, the absolute amount occluded per unit volume of 

 charcoal is about one-tenth that of the other gases at the same 

 temperature. There can be little doubt that when the relative 

 absorption of helium in charcoal is measured at the tempera- 

 ture of liquid hydrogen, the increased absorption will be so 

 marked as to make it comparable to that of hydrogen in the 

 present set of experiments. In this case charcoal at the boil- 

 ing point of hydrogen will become an efficient condensing 

 agent for helium, and this property will have important appli- 

 cations in future research. 



Separation of Highly Concentrated Oxygen from Air. 



In order to examine the changes taking place in a mixed 

 gas like air during the absorption, a quantity of about 50 

 grams of charcoal was, after heating and exhaustion, saturated 

 at —185° in a current of pure dry air; got by passing the air 

 current through a U-tube immersed in liquid air. 



For a time the air rushed into the charcoal with great rapidity, 

 and in about 10 minutes between 5 and 6 liters were taken in. 



