Determination of sulphur species in solidified cryolite melts

Solidified cryolite melts containing a known amount of Na2SO4 (0-713 mg kg(-1) SO (4) (2-) ), Na2S, FeS, and CdS (0-400 mg kg(-1) S2-) together with industrial electrolyte samples were tested for the content of sulphate and sulphide ions by ion chromatography. Added and analytically determined contents of sulphate and sulphide were compared and processed by means of linear regression analysis. It was found that the method of ion chromatography yields satisfying results (uncertainty below 1.1 %) and that it is especially suitable for the determination of low content of soluble sulphate or sulphide in solidified cryolite electrolytes. The method can be used for the estimation of insoluble sulphide content in cryolite melts as well. Results of industrial samples analysis showed that the content of sulphate and sulphide in the samples is influenced by their treatment before the analysis.