ENERGY, PHOTOCHEMICALS AND BRIGHTNESS 309 



In the first equation, for example, the reaction proceeds 

 toward the right in the Hght and toward the left in 

 darkness. 



light 



1. 2 AgCl ^=f AgaCl + C1. 



dark 



light 



2. 2 C14H10 ( / C28H20. 



dark 



light 



3. 5 Agl ;=f Agia + 2 Ag2l. 



dark 



4. Tetraphenyldihydrotriazin. 



light 

 White c ' rose red. 

 dark 



5. Dimethyloxalessigesterphenylhydrazon. 



light 

 White < ^ citron yellow, 

 dark 



Cells — C — Cells CeHsCH 



6. Triphenylfulgid, OC-C C-CO 



I O 1 



light . 

 Orange yellow < ^ light brown. 



dark 



blue or violet (440 to 550"") 

 Orange yellow < ^ dark brown. 



red or yellow (550 to 700"") 



H CI2 



C C 



^ \ / \ 



HC C CCl 



7. jS-Tetrachlor-a-ketonaphtalion, I li II 



HC C CCl 



% / \ / 



C C 



HO 



ultra-violet 



White ( ' violet. 



yellow green 



