Barium Sulphide: Heavy Spar Roasted with Coal

Barium sulphide is the barium half of lithopone, the white pigment. Thorpe (1912): roast 100 parts of heavy spar with 20 parts of coal slack or charcoal. Caking bituminous coal soaks through the mass and reduces it completely; with charcoal, mix very thoroughly. The roasted mass still holds carbon and some unchanged spar: hot water takes out the barium sulphide. Left in air it turns to carbonate and smells of rotten eggs, so keep it closed. The picture: our own drawing.