certain sulphur compounds such as thiosulphuric acid , polythionic acids , thiocyanic acid , thioureas , thioamides and 2-mercapto-acids are readily electrolytically hydrogenated in 1n sulphuric acid to form hydrogen sulphide which is absorbed in potassium hydroxide solution and titrated with o-hydroxymercuribenzoic acid in the presence of dithizone as indicator .
C0038776
sulphur compounds
C0039958
thioureas