( 1249 ) 
db 
dp Ha (: 7 =) 2a 
& Sus (v - 6)? v? (1) 
and from the differentiation of 1 and after elimination of R7’: 
v db | 
v (on 2 dv? ieee an 
v—b do) db 2 ane | 
dv 
If 5 was known as function of v, II might serve for the determination 
of vj, and by means of this I might yield the value of 27. If 
; be 
for all substances a same function = =i / existed, the same value 
4 v 
by ‘ 
would always be found for — from II. In other words the quantity 
Vk 
r in verb, would have the same value for all substances. But 
a 
then RT), would be an equally great fraction of — for all substances, 
) 
9 
; Nd pv 1 
and pj an equally great fraction of — . In the same way (Fr =- 
s 
would have the same value for all substances — and particularly 
the investigations of SypNey Youre show us that great differences exist 
in the value of s for the different substances. So we are compelled to 
Vy 
pe may b 
abandon the assumption that in — =, (=) the course of — would 
g 5 9 
be the same for all substances. It is clear that this brings the 
o 
question what may be the cause of the circumstance that 6 becomes 
smaller with decreasing volume, to the front again, but for the 
moment I shall pass over this question in silence. That the value of 
yin i ; 5 ; 
r==-— is smaller than 3, and can be different for the different 
9 
substances, I shall, however, assume as certain. And in the same 
way that 7 descends the more below 3 as b descends more rapidly 
with v. If we assume a real diminution of the molecule as cause of 
this variability of 6 with v, we might put this as follows: the quantity 
r is the smaller in the critical state as the molecule is the more 
compressible. 
But whatever may be the cause of the variability of 6, the law 
db v ab 
of this change is unknown, and the quantities = and aa which 
occur in the equations I and II, are unknown. This excludes the 
