1013 
for the equilibrium constant of the gas equilibrium. Hence whereas 
the expressions of § 2, which were exclusively derived from gas 
properties, leave the value for the entropy of solid out of account, 
and the calculations of the gas equilibria have nothing to do with 
the solid state either, so that the determination of the entropy of 
solid according to S=k log W remains a separate problem, the test 
of STeRN’s expressions can give a decision of the validity of Nurnst’s 
theorem of heat. If we assume Srern’s derivations for the gas 
entropy to be correct, then on application to the iodine equilibrium 
it appears that the algebraic sum of the entropies of the solid sub- 
stances at 7’=0O is not zero, which it ought to be according to 
the heat theorem, but about — 7. In this test it is assumed that 
the moment of inertia of the iodine molecules has the value that 
would follow from the mean molecule radius for iodine (from the 
index of refraction). We have here, however, two quantities at our 
disposal: the moment of inertia and ='S,.ia. It is clear that reversely 
the assumption that the sum of the entropies of the solid substances 
at T=0 is zero (through which this algebraic sum disappears from 
the constant of equilibrium and the expression deviates from that 
of Prof. van per Waars Jr. only in this that it is assumed in the 
former that the specific heat of the vibration has already reached 
its amount of equipartition) changes the value of the moment of 
inertia. On this assumption it gets about the value which was 
indicated in my first paper. 
9. The objection advanced by STERN against a small moment of 
inertia, is founded on the value of the chemical constant of /,, which 
was calculated by Sackur on the assumption of the mean molecule 
radius (from the index of refraction) for the moment of inertia, and 
with which the vapour pressure values of solid iodine can very 
well be represented as appears from Sackur’s test. *) In virtue of 
this, however, I do not think myself justified in rejecting the moment 
of inertia calculated by me. 
The said test of the vapour pressure line has been carried out 
by Sackur on simultaneous assumption of the expression 2 of § 2 
and of Scolid ar T=0 = 0. We are then led to the question whether 
these two assumptions are identical or in conflict with each other. 
Discussions with Prof. van per Waats Jr. concerning this question 
have led us to the following opinion. If the entropy of a gas is determined 
by means of log W, the expressions 1 and 2 of § 2 are found for 
1) Sackur, Ann. der Physik (4) 40 87 (1913). 
