Abstract

A detailed investigation has been made of the suitability of the Ag/S specific-ion electrode for the determination of sulphide in aqueous solution. It has been found preferable to use a titrimetric method with the electrode as indicator in order to determine total [S] rather than to measure the potential at the electrode and interpolate from a calibration curve. When the silver solution was titrated into the sulphide solution difficulties were encountered which interfered with precise location of the end-point. No such problems were experienced when the titration was done in the reverse direction and the estimation was performed successfully over a wide range of pH and ionic strength. Sulphite does not interfere with the titration and thiosulphate can be detected and allowed for from the shape of the titration curves. Using these procedures sulphide ion concentrations of the order of 5 p.p.m. have been readily estimated with a precision of better than 1 p.p.m.