Successive determination of sulfide and hydrogen sulfide ions by potentiometric titration using sulfide ion-selective electrode.

Abstract

A method for the successive determination of sulfide and hydrogen sulfide ions in a mixed solution in the absence of buffer substance such as sulfite was studied by argentimetric potentiometric titration using a sulfide ion-selective electrode as the indicator electrode and a silver-silver chloride electrode (the reference electrode). Sulfide, hydrogen sulfide, and the total sulfide ions could be rapidly titrated with silver nitrate standard solution or hydrochloric acid standard solution at room temperature. The mixtures(total sulfide concentration of about 2.5×10-3 M) of sulfide ion [(3×10-42×10-3)M] and hydrogen sulfide ion [(2×10-42.5×10-3)M] were determined with a relative standard deviation less than 0.3 %. Halide, thiosulfate, and sulfate ions did not interfere with the titration. The recommended procedure is as follows : Place 10 ml of the sample solution (mixed solution containing sulfide and hydrogen sulfide ions) in a titration cell containing 1-cm-thich liquid-paraffin layer. Add water 80 ml, which should be gently poured along the wall of the titration cell so that air bubbles are not entrained. Titrate the resultant solution with 0.1 M silver nitrate standard solution or 0.1 M hydrochloric acid standard solution potentiometrically. The titration times needed is less than 10 min.