( 741 ) 
and dissolved substance begins to play a part only im sensibly con- 
centrated solutions, and that we have to explain the osmotic pres- 
sure by a “moleculares Bombardement”. But the case treated by 
Lorentz shows that the whole osmotic phenomenon might possibly 
exclusively be the consequence, not so much of the presence of 
attractive. forces, but just of the reverse, of the want of attraction 
between the molecules of most solid substances and certain other 
solid substances which form membranes. If the adherents of the 
statie theory mean no more than this with their assertion: that the 
osmotic pressure must be explained from forces of attraction, then 
they seem to me for the present secured against every attack. 
Physics. — “Osmotic pressure or thermodynamic potential’. By 
Dr. Px. Konnstamm. (Communicated by Prof. J. D. van 
DER WAALS). 
§ 1. The theory of thermodynamic functions, through which 
Gipps has enabled us to derive from the equation of state of a system 
in homogeneous condition, what heterogeneous equilibria will oecur, 
has attracted attention only in a very limited circle during a series 
of years. However great the region opened for investigation by Gipps 
was, the methods indicated by him seemed so abstract, that only 
very few dared to grapple with them. At a stroke this was changed, 
when in 1885 Var ’r Horr succeeded in replacing these methods 
in appearance so abstract, by another, that of the osmotic pressure, 
which strongly appeals to the imagination. The theory of solutions, 
which up to that time had only existed for a few, rapidly became 
one of the most frequently treated and discussed subjects of physies 
and chemistry; sinee then it has continued to enjoy undivided 
attention. 
It stands to reason, that the attention, which now for twenty years 
has been so lavishly granted to the questions of heterogeneous equili- 
brium, have also been conducive to making GiBBs’ methods for the 
solution of such questions known in a wider circle. But though Gress’ 
name may be counted among the most famous and widely known 
names in the sciences of physics and chemistry, yet even now his 
methods cannot be said to have been universally accepted. 
The adherent of a mechanical (or, if one prefers, statistical) natural 
philosophy has by no means reason exclusively to regret this course 
of affairs, for he sees in it a clear indieatien, that the views whose 
truth he advocates, are by no means so antiquated, nay even dead, 
