SPECIFIC HEATS OF SOME COMPOUND GASES. 571 
Thus, since any error in y is increased tenfold in £, it is useless to do much more 
than find roughly the magnitude of the correction, until our experimental methods 
for determining y are much improved. 
If we take CLAustus’ equation 
RT C 
v—@ Tw + 6? 

p= 
as the characteristic equation of a ae we can, by making certain eppromimalions, 
express the correction for 8 in terms of | ror = ( pv). 
At ordinary temperatures and Ce a ia b are negligible compared with v, so 
. that f may be taken to be — C/Tv. 






Hence 
gp CMC 
p dv Tp?” RIy 
1 df 
v dp ae 
an Bs 
R dt” RT» 
Hepaue C 
790) TRAD) 
therefore 
2 4C 
te ream ace 
and 
git. Gq gC aay © 
p dv (G0) = Tp RI 
Hence 

2 4 
ae le < (pl. ore (5). 
Equation (5) has been used in calculating in all the tables that follow. 
In my former paper I pointed out (p. 34) that the y of ethyl chloride and a few 
other gases appeared to be greater at the higher pressures, and mentioned that the 
effect might be due merely to the divergence of the gas from Boyur’s law, and not to 
any change in the value of 8. This appears to be the case, for if 8 is calculated from 
the results by means of formula (5), the progressive change disappears. The table 
below shows this for ethyl chloride, where the change in y is most marked. 
