( 789 ) 
Physics. — “Thermodynamic potential and velocities of reaction.” 
By Prof. Pa. Kounstamm and Dr. F. B. C. Scuurrir. (Com- 
municated by Prof. J. D. van per WaAAts). 
(Communicated in the meeting of December 24, 1910). 
$ 1. In the preceeding communication one of us has shown that 
the number of molecules of a substance in a homogeneous phase 
which is able to escape from the attraction of this phase in the 
unity of time is indicated by the expression : 
u' 
/ 
RT 
1 
NEO Te (1) 
in which w represents the thermodynamic potential of this substance 
in that phase deprived of its mere temperature functions, and /è the 
molecular gas constant. This formula was applied there to find the 
condition of the stationary state, in which an equal number of 
particles enter a solution as leave it through a semi-permeable mem- 
brane, but another use of this formula is conceivable. We may, 
namely, put the question: When there is no equilibrium of exchange 
between solution and solvent through the membrane, how many 
more particles per unit of time will then leave the solution than 
enter it, or in other words how great will be the velocity in a 
certain state with which the whole system tends to reach equilibrium ? 
It will be expected that in the case mentioned the velocity may be 
represented by the difference between two expressions of the form 
(1), the former of which represents the number of particles which 
leaves the solution, and the second the number of molecules that 
leaves the solvent, and so enters the solution. We then get for 
this velocity the expression : 
wy Ue 
7 ERE LS 
Nt Gy rr 
Eee 
Such a formula would, of course, have to hold for all analogous 
cases; e.g. for that of the osmotic pressure and for the evaporation 
of liquids. These velocities, however, do not act a very prominent 
rôle in physics, and application of the formula to these cases does 
not seem to open new vistas, the less so as there would hardly be 
any experimental material to test them by. The problem of the velo- 
cities of reaction, on the contrary, plays a most important part in 
