( 304 ) 
Of greater importance is the test of the relation (3), which not 
only for hydrogen but for every substance mixed with carbon 
dioxide will hold with « exceedingly small: 
Ppl — Prk 
==. le 
Tpl — Tar 
For we find for this proportion with 
2= 0.0494 : 1.88, 
2= 0.0995 : 2.12, 
so that the value 1.61 for «=O will come near to the truth and 
therefore in this respect theory and observations confirm each other 
sufficiently. 
dT yj 
: d 
§ 7. In the same way as we have considered ve and ae 
xv x 
we 
. d . . . . 
can also consider a for «0, a quantity important with a view 
x 
to the determination of the critical volume of a simple substance. 
In the equation: 
See a) = eee Se 
: dv dv dv are 
the co-efficients Gal Gal, and ere all infinitely large for 
«= 0 and such that in the development their terms cancel one another. 
dv 
ze etc. the finite terms, in that 
dp 2T 
aT pI 
d, ; 
of Landt the terms with the first power of 2 must be kept. 
a ve 
Therefore in the development of ( 
As a starting point I have chosen the relations 
(3) 9 ut (3 oT : 
of § 2, which hold for the plait-point. 
; - 5 d, aT. i 
If in equation (4) we substitute the values and — which we 
& a 
obtain by the differentiation of the above relations: 
