402 Mr Bevan, On the Temperature Effect in the combination 



heating, if the mixture is kept at a high temperature, there is for 

 some time a slight excess of Chlorine evolved from the water in 

 the bulb. If the whole apparatus be cooled we get a slight excess 

 of Hydrogen, and apparently for the observation of December 2, 

 sufficient fresh gas had not been passed through the apparatus. 



On the ordinary theory of this action, if we attribute the 

 Induction Period to some interfering action at present not under- 

 stood, the relation between the velocity and temperature should 

 be according to van 't Hoff's theory, 



dlogK _A 

 dT T^ ' 



where K is the velocity constant and T the absolute temperature. 

 In this case K can be taken to be the velocity itself as the con- 

 centration of the Hydrogen and Chlorine remains constant during 

 the action*. This expression is derived on the assumption that 

 the action is reversible, which is probably not valid in this case. 

 However, the generally accepted theory of actions of this type 

 is that they are reversible and so we should examine the applica- 

 tion of the relation to the experimental results. 



We obtain on calculation from the smoothed curve the 

 following numbers for B, using the equation in the form 



B = 



(d\ogK\ J d\ogK \ 

 11 { dT A ±2 \ dT h 



Tf-Tf 



and taking for T 2 10° C. 



r x B 



20° -0168 



30 -0143 



40 -0123 



50 -0094 



60 -0078 



Another assumption on which the relation of van 't Hoff 

 depends is that the heat developed in the action is independent 

 of the temperature within the range considered. This is probably 

 true for this action. But the equation of Kooy 



dtegK = A±BT 

 dT T 2 ' 



which takes into account variation of the heat developed in the 

 action, gives results which are very little better. 



* We here neglect the influence of the water vapour in diminishing the concen- 

 tration of the Hydrogen and Chlorine, but this makes only a small difference until 

 high temperatures are reached. 



