( 304. } 
4 
we make suppositions concerning the quantities ‚a and 5, which can 
only be satisfied if the multiple molecules may be considered to be 
mere complexes of simple molecules, which can be formed without 
further radical modifications in the structure of the molecules them- 
selves. But as I will apply the given formula only in the case of 
saturated vapour at a pressure which is not very high, in which 
case the influence of the quantities « and 6 may be neglected, we 
may consider it to be sufficiently accurate for our aim. 
We may deduce from it: 
i dv de {1 n A 
En ) ar is aT \ xz + Copies Te 
For saturated vapour at a pressure which is not too high, we have: 
—l 
prik T (: nef r). 
n 
from which follows: 
n—l de 
dp dv i n dT 
pdr vdT fi Rl 
ee 
n 
: 1 
If we substitute for — - 
oA the value found above, we get the 
equation: 
la 1 T d ; A 
REE EE Ce 
dT nil ; 3 
az (1—e«)(1— 
Whether the number of multiple molecules in the saturated vapour 
increases or decreases with the temperature, depends therefore on the 
fact whether the value of the expression : 
A 
is more or less than = 
T dp. 6 Ter 
For a normal substance pat is approximately equal to 7 7: 
For a substance in which molecular transformation takes place, the 
factor 7 is to be modified and this factor will even vary more or 
less with the temperature. But if a perfectly accurate numeric deter- 
mination is not required, and if we only ask: Can both ways in 
which ‚pr may be thought to vary with the temperature occur? then 
we may state what follows: 
