(4204\) 
ereat volumes 6 for the second substance is only very slightly smailer 
than b,, and for great volumes the two isotherms may almost be 
considered as coinciding. But still, the fact remains that there is a 
difference, and that this difference increases with decrease of volume, 
and that this difference is the greater as the variability of 6 is more 
pronounced. 
oh pa ’ à =. 
At a value of v, for which = = 0 in the isotherm which lies above 
v 
the other, i; is positive in the lower isotherm. So the limits for the 
7 
unstable region are further apart in this case than for the upper 
isotherm. But the displacement of these limits is more considerable 
on the side of the small volumes. At the critical temperature of the 
NONE et, home 
first substance, so at RT = RE will still be positive for v = 3hy 
27 bg dv 
for the second substance, and so the temperatures will still have to 
rise, and become greater than ze je before the eritical temperature 
of the seeond substance is reached. 
But though we know that sr is smaller than 8 in all cases in 
which 4 becomes smaller at the same time with v, and the more 
so as b varies more rapidly with wv, still we have no rule as yet to 
determine the value of this quantity. Of course, this would be the 
case, if the law of the variability of 5 was known. 
b bg ; ; 
For instance, if oo 1—a-— could be put, which might be done 
" 5 
for not too small volumes, if the reason of the variability of 6 is 
not a real diminution of the molecule, but must be ascribed to an 
apparent diminution, as I already did in 1873. Then (IV) reduces to: 
and (VI) to: 
r? ie 
and with elimination of a, the approximate equations to: 
1 2s (f—1 s 
ee ea i ae 
r f / 
or 
Tie pede OENE 
r den 
or 
