Scheikunde. — De Heer Ernst Cohen biedt eene mededeeling aan 
van den Heer Nil Ratan Dhar : ,,CataIysis — Part VII — 
Tempernture Coëfficiënt of Physiological processes”. 
(Mede aangeboden door den Heer Van Romburgh). ^ 
In this article it is proposed to subject to critical examination the 
results obtained with regard to the effect of temperature on phjsio- 
logical processes. Before proceeding to the consideration of these 
reactioris I shall brieflj state the results obtained in the case of 
ptirely Chemical reactions and then try to show how far these rela- 
tions are applicabie to physiologicai changes. 
In homogeneous medium the following general results have been 
obtai)ied. 
a. The higher the order of the reaction, the smaller is the coëfficiënt 
of temperatnre, in other words, nnimolecular reactions have higher 
temperature coefficients than polymolecular reactions under identical 
conditions. 
b. The greater the velocity of a reaction the smaller is the temp- 
erature coeffhdent. 
c. The teraperature coëfficiënt of a positively catalysed reaction 
is smaller than that of the uncatalysed reaction and the greater the 
concentration of the catalyst the greater is the fall in the temperature 
coëfficiënt. 
In the case of negative catalysis, a reaction which is catalysed 
(negatively), has a higher temperature coëfficiënt than the uncatal- 
ysed reaction. In this case, the greater the concentration of the 
catalyst the greater is the increase in the temperature coëfficiënt. 
In the case of heterogeneous reactions, the following points have 
been established : 
a. Diffusion is the guiding factor in the velocity of heterogeneous 
reactions. 
b. With heterogeneous catalysts which cause reaction between 
the substance in question to take place with practically infinite 
velocity, the actual rate of reaction wili be determined solely with 
which the substance is diffused to the surface of the catalyst. 
c. If the heterogeneous velocity is that of the diffusion process, 
one will always get a unimolecular coëfficiënt for the reaction in 
question, independent of the actual order of the more rapid chem- 
