The Chemistry of Light-Production in Luminous Organisms. 187 



neutralized by adding an equal volume of n/1000 NaOH and tested 

 for light by adding photogenin. The photophelein was therefore in 

 contact with n/1000 HCl for 1 hour. In this way the effect of acid 

 on photogenin and photophelein can be separated. The results are 

 given in table 7. 



Table 7. — Effect of acid and alkali on photophelein and photogenin. 



Even very small concentrations of NaOH added to a glowing mixture 

 of photogenin and photophelein will decrease greatly the amount of 

 light (table 6) . Thus if we add 1 c.c. n/500 NaOH to 1 c.c. of a brightly 

 glowing mixture, making the concentration of NaOH n/1000, the light 

 instantly becomes very dim and remains so for a considerable time. If 

 NaOH be added to a concentration of n/250, the light disappears com- 

 pletely; if we now neutralize the NaOH with n/250 HCl, the light 

 returns, faint. 



Still smaller concentrations of HCl prevent light-production. Thus 

 (table 6) n/2000 HCl extinguishes the light from a luminous mixture, 

 but on neutralization with n/2000 NaOH, the light returns and is 

 fairly bright. The effect of NaOH and HCl is therefore to inhibit 

 light-production, and not to immediately destroy the photogenin and 

 photophelein (tables 6 and 7). The reversibility is not apparent if 

 the acid or alkali are only slightly stronger than the values given. 

 (Note also from table 7 that the photogenin is more readily affected 

 by HCl and especially by NaOH than the photophelein.) 



In the case of acid and alkali, as with so many other substances on 

 the light-giving material, the effect is to an extent reversible if the 

 substance is removed. The concentration of HCl which inhibits light- 

 production is the same as that affecting cells, although the concentra- 

 tion of NaOH necessary to inhibit light-production is somewhat greater 

 than that necessary to affect cells (12 and 13). 



