ELECTROCHEMICAL IDENTIFICATION OF THE HYDROGEN-SULFIDE SYSTEM USING APH(2)S(GLASS AG-O,AS(2)S) ELECTRODE/

An electrochemical method to simultaneously assess the two apparent di ssociation constants of the hydrogen sulfide system at pH values rangi ng from 6 to 11 is presented. pH(2)S and pS(2-) values were measured i n aqueous solutions of known total sulfide concentrations using a silv er sulfide/glass and a silver sulfide//silver chloride cell, respectiv ely, 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 estimate d through thermodynamic considerations. The controversy on the second dissociation constant is discussed.