363 



SCIENCE PROGRESS 



Following Hartley's work, Stewart, Baly, Desch and others 

 have shown that light absorption may be due to tautomeric 

 changes taking place within the molecule, as between the 

 forms : 



$ — CH=C(OH) — 



CH 2 — CO — 



or 



0" 



O- 



C 



/ \ 



c c 



I! I! 



c c 



_v 



o 



II 



/ c \ 



c c 



$ II II 



c c 



V 



II 

 o 



Which explains why absorption is not produced by the presence 

 of a single unsaturated group. And from Drude's researches 

 it is evident that Hartley's vibrating particles are subatomic 

 and correspond to the valenc}^ electrons. The relations be- 

 tween absorption and chemical composition must therefore be 

 sought in the dynamic condition of the valencies of the absorbing 

 groups. 



