(562) 
The more so, as the solubility of Hg, SO, (or Hg, Cle) is so small, 
a+ 
that the number of Hgg-ions present in the solution was already 
very small from the beginning. 
Because of this considerable change in concentration near the 
small surface, the difference of potential soon varies at that place, 
and it is easy to see, that this „kathodical’’ polarisation causes the 
current to cease quite, or nearly quite *). Be Z namely the elec- 
tromotive force of the inserted cell, then the intensity of the current 
has become zero, as soon as the original difference of potential Ao 
at the small surface has varied so much, that the new value A 
satisfies the equation 
E=A— Mos 
from which follows: 
BENE Nim ae a 
When this value is reached, the concentration ceases to vary and 
a stationary state is established. 
A, being negative, A will, when / increases, first reach a value 
zero and afterwards when Z increases still more, A will become 
positive. For every electromotive force ZE, which we may apply, we 
get a definite value of A, and so — measuring every time the 
surface-tension y of the mercury in the capillary — we geta series 
of values, which form together a curve 
y=f(d) or =F(E), 
which is called the eleetro-capillary-curve. This is the curve whose 
properties we will discuss in this paper. 
On purpose I have given the above explanation rather elaborately, 
because for the theoretical considerations which follow, a clear 
insight is required in what takes place in the capillary-electrometer 
according to the new electrochemical theories of Nernst, PLANCK 
and others. These theories are confirmed brilliantly by the experi- 
1) We shall leave out of account the so called vresidual current”, which will 
be caused by the slow depolarisation by diffusion, the intensity of that current being 
extremely small. 
