1167 
I am occupied with the application of the above described degra- 
dation method to other sugars such as pentoses. 
The more fully detailed communication will be given elsewhere. 
I have to tender my thanks to Prof. BrANKsMA for kindly giving 
me the opportunity to work in the organic-chemical laboratory of 
the University. 
Leiden, February 1915. Organic-Chemical 
Laboratory of the University. 
Physics. — “Theoretical determination of the entropy constant of 
gases and liquids.” By H. Trrropr. (Communicated by Prof. 
H. A. Lorentz). 
(Communicated in the meeting of Febr, 27, 1915), 
§ 1. Introduction and survey. 
If the entropy of an ideal gas per gramme molecule for the 
temperature 7’ and the pressure p is given by: 
S= Cplog T — Rlogp Jahn «+. « ve (1) 
in which f is the gas constant and GC, denotes the heat capacity 
under constant pressure assumed as invariable for the range of 
temperature considered, then « is a constant remaining undetermined 
in classical thermodynamics. This value has, however, a definite 
value according to NerNst's heat theorem, when namely the entropy 
is defined so that it becomes zero for 7’ = 0 for the condensed gas, 
i.e. for a chemically homogeneous solid or liquid substance, which 
we shall always tacitly supposed to be done in what follows. Ther 
we can determine a from measurements of the vapour tension, when 
we also know the course of the specific heat of the solid (or liquid) 
substance also at the lowest temperatures '), 
On the ground of a general definition of the thermodynamic 
probability in connection with the hypothesis of quanta I have 
derived the value of ~ for different cases in a previous paper*®), in 
which, however, at first undetermined universal values z, z,, and z, 
still occurred, which I supposed to be =1, while others thought 
they had to assign a different value at least to z*). 
u Me 
1) The quantity C= R logy) é is generally called the chemical constant of the gas. 
v 
2) H. Terrope, Ann. d. Phys. 38, 434 and 39, 255 (1912). 
5) O. SACKUR, Ann. d. Phys. 40, 67 (1913). 
77 
Proceedings Royal Acad. Amsterdam. Vol. XVII. 
