( 1222 )) 
fe EN EN 
af 
Comparing this value with (V) we see that if c, should be inde- 
pendent of 7, and so c, = sr always strictly equal to 8, the value of 
db dby, 
— | would be perfectly the same as —. But these two quantities 
dv) kr dv}; 
do not mean the same thing. The meaning of what I have repre- 
db\ . 
sented by & is clear. We have a substance with definite a and b,. 
U/ kr , 
The quantity 4, which is only equal to 5, for infinitely large volume, 
decreases on decrease of the volume, whatever may be its cause 
and the law according to which it decreases. Starting from very 
large volume, the decrease is so small at first that it can practically 
db 
be neglected, and zo may be put almost equal to 0. I have repre- 
av 
sented the value which = has in the critical point, by (=) ; 
dv "oN dh 
The way in which, even for substances with the same value of 
b,, the quantity 4 depends on v appears to be different, and this 
circumstance calls up the question again, what is, after all, the 
EET De NE NN 
cause of this variability of 6. At the critical point tae and as we 
g av 
: d*b ; 
shall more fully discuss later on ao SP POY different. And the 
x 
different way in which 4 depends on », is the cause, that the quan- 
tities s, f and r differ in the critical point. 
b 
at = 
b 
: os q = ; 
But the significance of hea? which quantity I have represented 
td 
db f RE 
in (V) by ee another. The equation (JV), from which it has 
Uk 
: é br. Cc s 
been derived, viz. — —=r——=r (1 —*) enables us to calculate 
by f 
oz DE : 
— in the critical point, when 7, s and f should be known for a 
g 
substance, and may therefore be considered as a locus holding for 
all substances, whatever may be the law of dependence of 6 with v. 
So it does not belong to a single substance. If the dependence of 
6 with » is given, only a single point of this locus refers to this 
b 
substance, viz. that point in which ae fw) tor that definite sub- 
9 
