Application of a sulphide-selective electrode in the absence of a pH-buffer

Calibration of a sulphide electrode in the pH-range 9–12 has been studied as an e.m.f. vs. (pH — p[HS −]) function by measuring e.m.f. and pH in parallel. Calibration can also be done in this pH range by using a differential amplifier with a three-electrode measuring cell (glass, sulphide-selective and reference electrodes). The effects of an antioxidant (ascorbic acid) and a complexing agent (DCTA) on the calibration of the glass-sulphide electrode cell at pH < 5 were studied. The applicability of this end-point indicator cell has been demonstrated for titrations of Ag +, Pb 2+ and Bi 3+ with Na 2S.