(6) 
in different cases, and we have to consider it as a primary datum 
without any relation to other properties of the solvent or of the 
solved substance. Neither can we account for the value of this ratio, 
if we think that the application of the law of Boyur is sufficient for the 
theory of mixtures; for this law is the same for all substances and 
cannot therefore account for the different values which this ratio has 
in different cases. Therefore it appears convincibly that a closer 
investigation of the quantities pw, wy, >, wr, and uw", is required. 
I pass now to this investigation. 
We start from the following equation, which may be considered 
as the definition of the quantity under consideration: 
*p 
MRT u =| rdp 
So in the first place this quantity depends on p, but as the equa- 
tion of state for a mixture depends on the composition, it also depends 
on x and y. We deduce from this equation: 
du a, © P/ dv 
. MRT — MRT u DE dp 
de )pTy da pTr, 
0 
‘ dv Op Ov 
If we write | — see , we find also: 
da v Op Jax 
MRT a da ee SG | 
1 u PN te G ; G) dp = == 
d 
UR Ts = (GE) 
In Cont. II, p. 9 and p. 19 I have started from this last 
equation, and making use of the form of the equation of state given 
there, I have obtained the result, that for low temperatures «',, may 
be neglected and gw’, may be put approximately proportional to 
ahs es 
dx 
would be the critical temperature of a liquid mixture, if this mixture 
might be considered as a simple substance; or, what comes to the 
same, 7, represents that temperature for which the theoretical iso- 
thermal of that mixture which we think always homogeneous, 
presents only one horizontal tangent, and for which therefore maxi- 
mum- and minimum-pressure have coincided. 
, if by the symbol 7% we represent the temperature which 
It is true that this quantity 7, is no experimental quantity, and 
