1813.] Specific Heat of the different Gases. 433 



Specijic Heats of 



. A 



Equal volumes. Equal weights. Spec-fic gravity. 



Air 1-0000 1-0000 1-0000 



Hvdrogen 0-9033 12-3401 0*0732 



Carbonic acid ... 1 -2583 0*8280 1-5 196 



Oxygen 0-9765 0-8848 1-1036 



Azote 1-0000 1-0318 0-9691 



Oxide of azote . . 1-3503 0-8878 1-5209 



defiant gas 1-5530 1-5763 0-9S85 



Carbonic oxide . . 1-0340 1-0805 0-9569 



The difference between the specific heats of the gases, when 

 the same weights of both are taken, is more considerable, as ia 

 obvious from the table* 



§ II. — Influence of the Density on the Specific Heat of the same 



Gas. 



The specific heat of atmospherical air in the ratio of its 

 volume, increases with its density, but ut a slower rate : of 

 course, considered in the ratio of the mass, it diminishes as the 

 density increases. 



This is the direct result of our experiments, which give us the 

 specific gravity of air, subjected to the pressure of 41-654 inches 

 of mercury, 1*2396; while that of the same volume of air, 

 subjected to the pressure of 29-634 inches of mercury, was 

 1-0000. Here the increase of specific beat is in the ratio of I 

 to 1-2396, while that of the pressure is in the ratio of 1 to 

 1*3583. 



It results, likewise, from this experiment, that the latio of the 

 pressures being the same as before, the specific heats of the 

 same mass of air, subjected to these different pressures, are in 

 the ratio of 1 to 0*9126. 



Every peison knows that when the air is compressed heat is 

 disengaged. This phenomenon has been long explained by the 

 change supposed to take place in its specific heat : but this 

 explanation was founded upon mere supposition, without any 

 direct proof. The experiments which we have given seem to us 

 sufficient to remove all doubts on the subject. 



J)r. Irvine, and several philosopers since his time, have 

 endeavoured to determine the real zero, or the number of 

 degrees that a body must be cooled in order to be deprived of 

 the whole of its heat. He set out from this principle, (hat the 

 quantity of beat disengaged, or absorbed, during the passage of 

 a body from one state to another, is entirely owing to the ehfl 

 of capacity which takes place in the body : and he conceived 

 that he could, knowing this change of capacity, and the quantity 



Vol. II. >.'- VI. 2E 



