18S 
SPECIFIC HEAT OF GASES. ‘ 
Specific )ieat 
of the air 
under different 
pressures. 
the temperature of the calorimeter elevated g®53 above that oa 
the ambient air. The difference between these two resuliJ 
was, therefore, y°53 — 8°43 = 1°1 = effect produced by tha 
vapours. 
The barometer, during the course of this experiment 
was at 0 7594 metres. With this result, if we consult the 
table of Dalton, we shall find, that the volume of air comparet 
with the vapour was as 15 0 to 1. We have seen that the 
effect of this vapour was expressed by 1°1 j and as, in general, 
this effect is proportional to the quantity of elastic ffuid which 
traverses the calorimeter, it follows, that a current of vapour 
equal to the current of air would, under the same circum- 
stances, raise the calorimeter to l6°5 above the ambient air. 
We may, therefore, from these experiments, conclude, that 
the specific heat of air being I'OO - - - - rooo 
That of the vapour of water 
is, with the same volume, rpG or under the same 
weights - - 3/ 13(3*. 
We are, however, obliged to confess, that the quantity of 
vapour and its effect being very little, and having been multi- 
plied by 15 to establish the comparison with the air, a small 
error in the experiment may cause a considerable one in the I 
result. I 
Section V. B 
Specific Heat of the Air under different Pressures. ' | 
The form of our gazometers was such, that we could cause I 
air, subject to different pressures, to circulate from one to the 
other. It was easy, therefore, for us to heat also beforehand 
currents of air under different pressures, and to determine at 
what term each of them would maintain the temperature of 
the calorimeter stationary. 
• This specific heat has been calculated on (he supposition, that the 
weight of vapour is to that of air as 10; 16. — Gay-Lussac, Anmlesde 
Chimie, tom. 80, jr. 218, 
The 
