211 



tioii between the reaction velocities and the thermodynamic relations. 



As regards the former, in the oxidation of alcohols loith coopera- 

 tion of aromatic ketones activated by light I have found a reaction, 

 in which the catalysis proper (the dislocation) could be sharply 

 distinguished from the formation of a coumpound between catalyst 

 and the molecules present. -) 



When an alcoholic solution of benzophenon, which is kept 

 saturate with oxygen, is exposed to violet light, the alcohol is oxi- 

 dized to aldehyde and water, the ketone remaining unchanged. 



A closer study brought to light that above a certain concentration 

 of the ketone the velocity of reaction became independent of (his 

 concentration, and further that it was proportional to (he square of 

 the inlensity of the light and to the first power of the cone, of (he 

 alcohol. 



This may be explained as follows: 



The ketone absorbs part of the light and is aclivated by it. 

 According to the laws of absorption (he quan(i(y of active ke(one 

 will be proportional to: 



/{l—e-^'-'^) in which )^- = absorption coefficient 



c = concentration ketone 

 f/=: thickness of layer 

 jg-kcd is (he ligh( that is transmitted. If k, c, and d are pretty 

 great, this is very li(tle, and all the light is absorbed. The quantity 

 of activated ketone then becomes proportional to / and independent 

 of c, its concentration. 



When we assume that among others the (wo following processes 

 take place : 



2 active ketone -f alcohol — (active ketone), alcohol 

 and 



(active ketone), alcohol + = ketone + aldehyde + H,0, 

 the former of which proceeds much more slowly than the latter, 

 the oxygen absorption (which was measured) will be determined by 

 the first process, the velocity of formation of the ternary compound. 

 This velocity of reaction must (hen be proportional to (he square 

 of / and to the concentration of the alcohol. 



I will not enter here in(o a fuller discussion how (his migh( be 

 proved in diff-eren( other ways ^). The whole process can now be 

 described as follows: 



Under (he influence of (he ligh( there is suddenly formed a 



^) Kecueil 40, 433—445. 

 2) 1. c. p. 439—442. 



