ad 
( 155 ) 
from this that the B. M.F. of the element is simply a function of 
the electrolytic solution tensions of the two modifications of tin. 
The employment of the element described as a transition element 
depends on the fact that at the transition temperature the two modi- 
fications become identical, the grey modification being transformed 
into the white. In equation (1), P, and Pare then equal and Z = 0. 
In order to discover the transition point of the change 
grey tin 2 white tin 
it is therefore only necessary to find the temperature at which 
E=—0. The application of this method is to be found in the com- 
munication which Dr. van Eyk and I made some time ago on the 
Enantiotropy of tin !). 
We can now go a step further and investigate the electrolytic solu- 
tion tensions. We require the equations 
RT Py RT der 
= —log. — and £,=- log. —— 
Nn Eo Pi "Ey Pi 
By placing an electrode of grey or of white tin in a dilute solution 
of a tin salt and combining it with a normal (Hg—-HgCl—!/,,N . KCl) 
electrode, £, and Ey may be separately determined. If the dissociation 
of the tin solution is known, all the quantities required to calculate 
P, and Py are then known. 
From the equations we obtain 
n Ei nF, 
0.0001983 2’ 0.0001983 7’ 
P,=p, + 10 adv, eed 
4, In the first place an element was prepared with a sample of 
nr En 
grey tin from Prof. HseLr of Helsingfors and the ratio —— deter- 
9 
mined at different temperatures. 
Recently we have succeeded in converting ordinary Banca tin 
into the grey modification in any desired quantity *). The measure- 
ments here described are to be repeated with this material which 
is particularly pure and the results together with the details of 
manipulation will be described in a later communication. 
1) See note 1 on pag. 149. 
2) See pag. 152. 
