M. LOSADA, iM. NOZAKI, AND DANIEL I. ARNON bl'6 



EFFECT OF N2 AND NH4CI ON 

 PHOTOPRODUCTION OF H2 FROM THIOSULFATE 



120- 



10 



60 



20 30 40 50 



minutes 



Fig. 3. Effect of N, and NH4CI on photoproduction of hydrogen from thiosulfate 

 by Chromatium cells. In the Nj treatment, nitrogen gas was used instead of 

 argon as the gas phase. 10 micromoles of NH4CI was supplied in the NH4CI 

 treatment. Other experimental conditions as described for Fig. 1. 



culture indicated a transitional formation of elemental sulfur. The 

 results are explained by the following sequence of reactions: 



light 



SaOr + 2 H+ + 2 OH- 



^ s + sor + H2O + H2 



(^) 



light 



S + 8 H+ + 8 OH- ^-^ SOr + 2 H+ + 4 H2O + 3 H, (2) 



dark 



10 H2O 



Sum: S2OT + 5 H2O 



^ 10 H+ + 10 OH- 



(3) 



light 



^ 2 SOr + 2 H+ + 4 Hj 



