THE CHEMISTRY OF LIGHT PRODUCTION 127 



catalytic decomposition of H2O2 by Pt or Ag, it does not 

 affect the catalytic decomposition of H2O2 by thallium. 



OxYLUciFERiN-. — When lucif erin is oxidized it must be 

 converted into some substance or substances and I believe 

 this change involves no fundamental destruction of the 

 luciferin molecule as it is a reversible process. I shall 

 speak of the principal (if not the only) product formed 

 as oxyluciferin. 



If we assume that the oxidation of luciferin changes the 

 molecule but slightly, we at once think of comparing the 

 change luciferin t^ oxyluciferin with the change reduced 

 haemoglobin -^ oxyhasmoglobin. The condition is, how- 

 ever, not so simple as this, for oxyhaBmoglobin will again 

 give up its oxygen providing the partial pressure of 

 oxygen is made sufficiently low, whereas oxyluciferin will 

 not do this, at least in the dark. We can not reduce oxy- 

 luciferin solution by exhausting the oxygen with an 

 air-pump. 



There is rmother oxidation-reduction system which can 

 also be easily reversed, but not by merely removing the 

 oxygen from the solution — that is, the reduction of a dye 

 such as methylene blue to its leuco-base. I believe the 

 change which occurs when luciferin is oxidized is similar 

 to that which occurs when the leuco-base of methylene 

 blue or sodium indigo-sulphonate is oxidized to the blue 

 dye. Oxidation of leuco-dye bases occurs spontaneously 

 in presence of oxygen and appears to consist in the re- 

 moval of hydrogen from the leuco-base with formation 

 of water. Reduction of these dyes may be effected in the 

 same ways that oxyluciferin can be reduced. In the case 

 of methylene blue, reduction consists in the addition of 

 two hydrogen atoms. Whether a similar change occurs 



