Scheikunde. — De Heer Ebnst Cohen biedt eene mededeeling aan 
van den Heer Nil Ratan Dhar: „Catalysis. X. Expïanation 
of some abnormally large and small temperature coefjicients" . 
(Mede aangeboden door den Heer van Rombürgh). 
Skrabal (Monatsh. 1914, 35, 1157) has shown that the velocity 
of formation of iodate frona iodine and iodide in a mixture of 
sodium carbonate and sodium bicarbonate Solutions has 
“IT 
= 45. 
When a sirailar reaction was effected in sodium acetate solution 
the temperature coëfficiënt is 2. 
The velocity of decomposition of iodate in a mixture of acetic 
acid and sodium acetate solution has — j[ 34 The same reaction 
kt 
in a mixture of disodium and monosodium phosphates gives a 
temperature coëfficiënt ’ 1.26 ; in a mixture of KF and HF, the 
temperature coëfficiënt has the value 0.9 to 1.04 and a mixture of 
sodium sulphate and sodium hydrogen sulphate leads to the value 
of 0.85. 
Skrabal remarks that the temperature coëfficiënt must necessarily 
undergo a change when the substances, which affect the time 
equation, are transformed into complexes. The relationship between 
the temperature coëfficiënt T of the original reaction and T', that 
of the reaction between the complex substances is governed by tlie 
forraula, 
T^/T = q10/RT (ï -|- 10) (mQi -f- nQ2,-|- -f- xqi -j- yq^T ) 
in which Q and q respresent the heat changes of the complex 
reaction and the sum (m -f- + • • • • -f- ^ + J + • • • •) indicates the 
order of the reaction. This formula indicates that a great variability 
of T is to be expected from reactions of the higher orders. 
In a foregoing paper (Annales de Chimie et de physique 1919, 
t. XI, 130) 1 have definitely proved that this conclusion of Skrabal 
which States that the teraperature coefficients of polymolecular 
reactions are, in general, greater than those of unimolecular ones, 
is not supported by experimental evidence. 
Skrabal investigated these two poiymolecular reactions: 
3 I, + 6 OH' = 5 F + I O', + 3 H,0 and 
I O', + 5 I' + 6 H- = 3 I, + 3 H,0. 
32 * 
