SECT. II. 



BY GASES AND VAPOURS. 



heat having a constant temperature of 270 Cent, were 

 adopted. 



The following table shows the absorption of a num- 

 ber of gases at a common pressure or tension of one 

 atmosphere. 



Dry air . 



Oxygen . 

 Nitrogen . 



Chlorine . 

 Hydrochloric acid 

 Carbonic oxide 



1 

 1 

 1 

 1 



39 

 62 

 90 



Carbonic acid . 

 Nitrous oxide . 

 Sulphuretted hydrogen 

 Marsh gas 

 Sulphurous acid 

 Olefiant gas 

 Ammonia . 



90 



35-5 

 390 

 403 

 710 

 970 

 1195 



The absorptive power of ammonia is so great, that 

 although as transparent in the glass tube as if it had 

 been a vacuum, a length of three feet of it would be 

 perfectly impervious or black to the heat here employed, 

 yet even this does not express the energy which it ex- 

 hibits under one inch of pressure. 



When the relative absorptive actions of gases and 

 vapours is compared, it must be under the same amount 

 of pressure. Hence, for one inch of tension, the absorp- 

 tive action of 



Dry air 



Oxygen 



Nitrogen 



Hydrogen 



Chlorine 



Bromine 



Hydrochloric acid 



= 1 

 1 

 1 

 1 



60 



160 



1005 



Carbonic oxide 

 Nitric oxide 

 Nitrous oxide 

 Sulphide of hydrogen 

 Ammonia 

 Oletiant gas . 

 Sulphurous acid 



750 

 1590 

 1860 

 2100 

 7260 

 7950 

 8800 



Thus, for a tension of an inch of mercury, the 

 absorption of ammonia exceeds that of air more than 

 7000 times ; -the action of olefiant gas is 7950 times, and 

 that of sulphurous acid 8800 times, greater than the 

 absorption of air. 



The effect produced by ^th of an inch of tension 

 of air and the elementary gases is equivalent to that 

 produced by one inch in the others, so the unit repre- 



