1019 
in which J/,, M,, and J/, represent the moments of inertia, r,, r 
and r, the vibrations. of the molecules AB, A,, and B, 
If by the aid of the entropy values of §2 the value of K is 
determined we get, disregarding the term with the r-values, an 
identical expression. Hence the expressions of SACKUR, TETRODE, VAN 
DER Waats Jr., and also those of Stern, when at least with regard 
to the latter it is assumed that Nernst’s heat theorem is valid, yield 
the same result here. 
With regard to the test of this expression we must remark that 
there occur three moments of inertia in equation 15, and that the 
ratio of the moments of inertia can only be determined from the 
equilibrium values. 
The value of Sn/yp=., which naturally cannot be directly deter- 
mined with the equilibrium /, 2 2/, can generally be calculated 
here from the calorie data of BerramLor, THomsen, and others. 
From equation 15 follows for the transformation energy : 
Thay Ths 
anh = SnE T= + ae Ek ie —2 aus ngs yb) 
RT —_\ kT A ekT __] 
2 
If we, therefore, know the r-values from the specifie heats, the 
value of 2n Hypo can be determined from the thermo-chemical 
determination of nf. The r-terms are generally so small that they 
do not cause appreciable deviations between these quantities. 
At low temperatures in equation 15 the term with the frequencies 
has about the value 1. The material that admits of testing, now 
consists for a great part of determinations of electromotive forces of 
gas cells, in winch the term of vibration may therefore be left out. 
Then, however, the agreement with Sacktr’s expressions becomes 
perfect, and | can therefore refer to his paper for the testing of 
these determinations.') Sackur finds good agreement between the 
experimental determinations and his expressions, which are founded 
on the moment of inertia, which follows from the mean molecule 
radii (6 of the equation of state, index of refraction and internal 
friction). At higher temperatures, however, the term with vp asserts 
its influence, and we shall, therefore, have to examine it; for the 
sake of completeness | have inserted the values of the gas cells 
also in the subjoined tables. 
14. The equilibrium UHCI H, + CI. 
The heat of formation of 2HCl from H, and Cl, is given by 
1) Sackur, Ann. der Physik. (4) 40 101 (1913), 
