572 



LIGHT AND LIFE 



TABLE 1 



Adsorption on Palladium Asbestos of Hydrogen, Photochemically Evolved 

 BY Chromatium Cells from Thiosulfate 



Control 



Palladium asbestos added 



/itnoles Ha evolved 



7.2 

 0.6 



Experimental conditions as in Fig. 1 except that no Tris buffer \\as added and 

 50 /tmoles thiosulfate were used. 100 mg palladium asbestos (11) were placed in 

 the sidearm of the Warburg manometer flask. Reaction time, 2 hours. 



thiosuliate was also inhibited by molecular nitrogen and ammoniinn 

 ions. The results are shown in Fig. 3. 



The photoproduction of hydrogen was dependent on the concen- 

 tration of thiosulfate and was abolished by heating the cells (Fig. 

 4) . Growing Cliromatiitm cells were found, by analysis, to have 

 oxidized in four days 27 millimoles of added thiosulfate into 54 

 millimoles of sulfate. During this period the appearance of the 



PHOTOPRODUCTION OF Hz FROM THIOSULFATE 



30 40 

 minutes 



Fig. 2. Effect of pH on photoproduction of hydrogen from thiosulfate by Chro- 

 alium cells. Phosphate buffer was used to adjust pH to 7.0 and below, and 

 Tris buffer to adjust pH to 7.5 and above. Other experimental conditions as de- 

 scribed for Fig. 1. 



ma 



