( 335 ) 
The elements considered consist of two cells, coupled in opposition, 
and constructed as follows: 
Saturated solution of a salt 
Electrode, reversible with Electrode, reversible with 
S in contact with the stable 
respect to the anion. respect to the kathion. 
solid phase of the salt. 
and 
Saturated solution of the salt 
Electrode, reversible with Electrode, reversible with 
S in contact with the meta- 
respect to the anion. respect to the kathion. 
stable solid phase of the salt. 
2. The temperature coefficient of the transition element will first 
be calculated at the transition temperature itself, on the supposition 
that the salt in the element is zine sulphate (Zn SO,. 7 HO and 
Zn SO, . 6 H»0). 
We will set out from the equation !) 
PaP 
Where £ is the B. M,F. of the element in calories, q the heat 
evolved by the change which gives rise to the current, P the abso- 
Jute transition temperature of the change which occurs in the ele- 
ment and 7 the temperature of the element. 
Differentiating (1) with respect to 7 we find: 
dE i g r 
(em es . . . ° . . . ° (2) 
At the transition temperature, the change which takes place in 
the element during the passage of 96540 coulombs may be repre- 
sented by the equation: 
Zn SO,.6 HyO + Zn SO,.a H,0 = 
a—O0 
| Se 
l (a— 6) (a—7) 
a—d 
Ee Zn SO, 7 Hy | Bete: ans en 
In this equation a is the number of molecules of water associated 
') van ’r Horr-ConeN, Studien zur chemischen Dynamik (1896), S. 247 u. 260. 
24 
Proceedings Royal Acad, Amsterdam, Vol, II. 
