148 
Consequently the metal will exhibit a potential that is more 
positive than the equilibrium potential. | 
OBSERVATION. 
Analogous considerations as those on page 135, given there of a 
metal in a solution of its ions and electrons, hold for every equili- 
brium between coexisting phases which contain charged particles of 
different solubility. In this case a potential difference will always 
occur, given by the equation A= — oe, where u, and u, indicate 
p 
the molecular thermodynamic potentials of the charged particles in 
the two phases. As these in general wiil not be the same, there 
must exist a potential difference. 
This applies then also e.g. for a salt in equilibrium with its 
saturate solution, for a solid salt in equilibrium with its melt ete. 
Amsterdam, May 25, 1916. Anorg. Chem. Lab. of the Univ. 
Physics. — “On Diffusion in Solutions.” 1. By Dr. J. D. R. SCHEFFER 
and Dr. F. EB. C. Scurrrer. (Communicated by Prof. A. F. 
HOLLEMAN). 
(Communicated in the meeting of May 27, 1916). 
1. Introduction. ErNsrrin has derived expressions which indicate 
how the mean square of the deviation of a Brownian particle and the 
diffusion constant depend on the nature of the substances and the tem- 
perature’). The relation between the Brownian movement, indicated by : 
eae 
De = Si t (1) 
N 3206 
and the diffusion constant is expressed by : 
ix 
ee ERE 
2t 
so that for the latter 
poe 1 8 
Eee Sen (3) 
is found, an expression, which can also be found by a direct way 
by making use of the osmotic pressure, which as apparent force 
causes the diffusion, and the law of Srokes, which gives the resist- 
1) EINSTEIN. Ann. d. Phys (4) 19. 289. 371 (1906). Zeitschr. f. Elektrochem. 
14. 235 (1908) 
