Describes a method based on prior conversion of the sulphur compounds in a test portion to sulphate, if required, and reduction of the sulphate ions ti hydrogen sulphide by a mixture of hydriodic and phosphinic acids in the presence of hydrochloric acid. The hydrogen sulphide is entrained in a current of nitrogen and absorbed in a solution of sodium hydroxide in aqueous acetone, followed by titration of the sulphide ions with standard volumetric mercury(II) acetate or nitrate solution in the presence of 1,5-diphenyl-3-thiocarbazone (dithiozone) as indicator.