400 Mr Bevan, On the Temperature Effect in the combination 



required for further saturation of the liquids involved and for 

 obtaining a mixture of gases of the maximum sensitiveness. It 

 was found best, in the long run, to keep a constant small current 

 of gas evolved by electrolysis from concentrated hydrochloric acid 

 running steadily through the apparatus, and not to increase the 

 rate of evolution so as to quickly drive out gas of less than the 

 maximum sensitiveness. Altering the rate of evolution of gas 

 was found to diminish the sensitiveness to light, probably owing 

 to changes of concentration round the electrodes giving rise to 

 small changes of composition of the evolved gas. The individual 

 experiments each required about ten days' preparation, so that 

 a long time was necessary for a series of observations. At a 

 particular temperature the • rate of combination was observed 

 daily until a maximum rate was reached, after which no further 

 increase in the rate was observed on further saturation. This 

 rate, therefore, is the rate of combination for the pure mixture 

 at that temperature. 



The following table shews the way in which the maximum 

 action is reached. Each observation represents the rate of com- 

 bination after the period of induction is passed, that is, the steady 

 rate of combination. 



The following table gives the results obtained with the dates 

 on which the final readings were taken for each temperature. 



