Energy of Light and Chemical Energy. 215 



B. The Effect of Light upon the Induction and Deduction 

 Periods and upon other Properties of Matter* . 



Since now it is the light pissing through the system which 

 is producing the new light-kinetic energy of the atoms and 

 the new additional chemical energy of the molecules of the 

 system, and this is a time process, it follows that it is a thermo- 

 dynamic necessity that all the systems without exception 

 (since all systems absorb light), those with independent as 

 well as those with dependent variables of composition, should 

 arrive at their new state of maximum kinetic energy, passing- 

 first through a period of gradual approximation to the same. 

 This period is called the "induction " period. 



Experimental evidence : — 



1. Such an induction period we find when light is acting 

 upon one of the two plates of the same metal, while the 

 other plate is kept in the dark, in the arrangement before 

 mentioned. Here we have a system with independent 

 variables of composition, where no chemical reaction takes 

 place in the same under the action of light, though a gradual 

 increase in the chemical and a creation and increase of the 

 light-kinetic energy, no doubt, take place, because if the 

 chemical potential remained the same at the two surfaces of 

 the plates, no electromotive force could be generated. We 

 may call it the induction period of energy. 



1. Such a period of induction we find lor the system with 

 dependent variables of composition, i. <?., where a chemical 

 reaction takes place. It was found by the author"* that the 

 velocity-constant of chemical combination of CO and Cl 2 

 gradually increases till it reaches its constant value. Bunsen 

 and lioscoe first observed the phenomenon of " chemical 

 induction " in their investigation of the combination of 

 chlorine and hydrogen under constant conditions. The 

 phenomenon, however, is of a more complicated nature than 

 conceived by Bunsen and Roscoe. Here we have to deal 

 with two periods : one of induction of energy, the other of 

 chemical induction already found by Bunsen and lioscoe. 

 Indeed chemical combination does not usually start at once on 

 exposure to light, but the system first passes through a latent 

 period during which no chemical reaction can be perceived by 

 the most delicate means, but a gradual increase of the stored 

 energy in form of chemical energy and in form of a kinetic 

 energy sul generis undoubtedly takes place in the same manner 

 as in the case of the metallic plates mentioned above. When 



* See the author's paper "On Chemical Statics and Dynamics under 

 the Influence of Light," Philosophical Transactions of the Royal Society, 



October 1902, pp. 378-391. 



