748 
with") @ = 31,583; 6 = 0,847 ; 7 == 7697, from which we draw 
= (2) log. p) =(e=, 8) Blog T ogenen onal 
di 
To be able to determine S’ too, we shall take for 7’ the melting 
point of mercury (234°). If 7 is the heat of fusion and S" the 
entropy of solid mercury we have 
St Ee Si é (19) 
_ i T° . . . . . . . e 
We must remark here that strietly speaking this formula gives 
the value of SS’ for a pressure of 1 atm. (if we consider the equi- 
librium between solid and fluid mercury under that pressure), while 
in the preceding equations S' denotes the entropy of the fluid under 
the pressure of its vapour. It is easily seen that we may neglect 
this difference. 
It remains to determine the entropy A” of solid mercury. This 
can be found by supposing, as is often done in connection with 
Nernst’s heat theorem, that this entropy is O at the absolute zero. 
Then it can be calculated for any other temperature by means of the 
specific heat c, of solid mercury. We have 
! C ) ryy ¢ 
= | Fag oe ey Se et ee 
v0 
if we assume the pressure to be 1 atm. during the heating from 
OF SO 
Nernst?) has given a formula for the specific heat of a gram 
molecule, based on PorLrzer’s measurements and by means of which 
we find *) 
1) According to Hertz we have, using Briggian logarithms and expressing the 
vapour pressure in millimetres of mercury 
3 Goren SS ate 
log p = 10,59271 — 0,847 log T — - Fr 
If we want to know the pressure in dynes per cm?. we must add log 1320, 
as a pressure of 1 mm. of mercury corresponds to 1330 dynes per cm?°. To pass 
finally to’ Neperian logarithms we must divide the first and the third term by logio € 
2) Anu. d. Phys, 36 (1911), p. 431. 
8) According to Nernst we have in G.G.S. units 
3 ee 
cy = 5 Rye) 1 7 Go), 
where the function ¢ is determined by 
