THE PRODUCTION OF SULPHURETTED HYDROGEN 31 



With these data it is possible to ascertain the conditions of 

 equiUbrium in sulphur waters in which, according to Baas- 

 Becking the^H value varies from 7-6 to 8-6. At^H 7-6 the differ- 

 ence in the logarithms of the concentrations of HS~ and HgS 

 is 0-55, as indicated in the graph. Hence the actual ratio of 



HS~ n ^^ . 



concentration ^^rrr = lo"-*"' =? 3-5. 



H,S 



TTC- 



At pH 8-6 this ratio ^v^ = 35- 



Hence in sulphur waters 



the HS concentration is 3-5 — 35 times as high as the H2S 

 concentration. 





7 



■pW 



Fig. I. 



(After Baas-Becking.) 



(Baas-Becking appears to obtain 50 — 100 for the same 

 range of pW values, but this difference does not affect the 

 main argument.) 



Again, at pH ^'6, 

 and at^H 8-6, 



HS- 



S 

 HS 



- = 2-5 X 10' 



S~ 



2-35 X 10^ 



It therefore follows that the concentration of HS" between 

 pH 7-6 and pH 8-6 is somewhat greater than the concentra- 

 tion of HgS, and far greater than the concentration of [S ]. 

 From the above facts he makes the assumption that the 



