ISO 5143:1977

Sodium carbonate for industrial use — Determination of sulphur compounds content — Method by reduction and titrimetry

Applicable to products having a S compounds content, expressed as sulphate, of equal to or more than 5 mg/kg. Bases of progressive neutralization, with evolution of carbon dioxide, by adding slowly a mixture of hydriodic acid and hypophosphoruos acid. Reduction of the compounds to hydrogen sulphide by heating. Distilation of the hydrogen sulfide, entrainment in a flow of oxygen-free nitrogen and absorption in a mixture of acetone and sodium hydroxide solution. Titration of the sulphide with standard volumetric mercury(II) nitrate solution in the presence of dithizone as indicator. Has also been approved by the IUPAC.