AbstractBarium sulphate is reduced by carbon to barium sulphide at higher temperatures. BaCO3, SO2, Snand COS are found as by‐products in small amounts. It has been confirmed experimentally that barium sulphite is an intermediate of the reduction process. This compound, however, is not stable at temperatures above 500°C and decomposes mainly to BaSO4and BaS and to a little extent to BaO and SO2. This reactions even take place in the presence of carbon which obviously only attacks the BaSO4whilst the barium sulphide is enriched in the reaction products. A series of consecutive and side reactions is proposed describing the stepwise reduction of barium sulphate to barium sulphi