1016 
the determinations of the vapour tension of solid iodine. The “chemical 
S gas —Cp + Rink — Solid T= 0 
2.3 R 
in which S',„s represents the entropy constant according to the gas 
scale, and in which Sg r—=o is generally also put zero (which in 
my opinion need not therefore be the case in the gas scale), is 
3,27 according to Sacktr'). The entropy constant of the gas is 
calculated by Sackur on the assumption that the moment of inertia 
calculated from the mean molecule radius (index of refraction) is 
the correct one. As the radius of inertia calculated by me in my 
2 
first paper, is at or 5.5 times smaller, and the moment of inertia 
therefore about 30 times smaller, the value of S'j;, in which the 
moment of inertia M occurs as RlnM*), would become Aln 30 or 
6,75 times smaller when the value found by me is used. Hence if 
we want to retain the value 3,27 for the “chemical constant’, 
Ssolid T=o must not be taken zero, but — 6,75, which is in satis- 
factory agreement with the result at the end of § 9. I think therefore 
I am justified in taking this as a confirmation of the validity of my 
former calculation. 
constant” of iodine, which is given by C= 
11. I would therefore summarize the above as follows: 
1. from the vapour pressure line of mercury the entropy of solid 
mercury appears to be about zero at the absolute zero point in the 
gas scale. 
2. it follows from the caloric data of iodine that the entropy of 
solid iodine (/,) at 7 =O is about — 7. 
3. it appears from the calculation of my preceding communication 
that the radius of inertia of /, is about five times smaller than the 
mean molecule radius determined from the index of refraction. 
4. when this radius of inertia is used the test of the vapour 
pressure line of iodine yields for the entropy of solid iodine a 
value of about — 7 in agreement with the second conclusion. 
5. the cited data do not allow of a test of the theorem of heat. 
6. In agreement with the third conclusion Manprrstoot’s calcu- 
lations lead to moments of inertia which are smaller than would 
agree with the mean molecule radii (index of refraction, internal 
friction, and b-values of the equation of state) ®). 
1) Sackur, |. c. 
*) These Proceedings, Vol. XVII p. 697, (equation 2). 
5) ManpersLoor, Thesis for the Doctorate. Utrecht. 1914. See also: These Proc. 
Vol. XVII, p. 702. (1914/15). 
