Electrochemical identification of the hydrogen sulfide system using a pH2S(glass/Ago,AS2S) electrode

An electrochemical method to simultaneously assess the two apparent dissociation constants of the hydrogen sulfide system at pH values ranging from 6 to 11 is presented. pH(2)S and pS(2-) values were measured in aqueous solutions of known total sulfide concentrations using a silver sulfide/glass and a silver sulfide//silver chloride cell, respectively, and calculated the apparent dissociation constants directly from the measured electrode readings. The measured constants (pK(al)' 6.91 +/- 0.05 and pK(a2)' 13.86 +/- 0.05) correspond well to those estimated through thermodynamic considerations. The controversy on the second dissociation constant is discussed.