Lepidolite Lithia Residue: Troost's Barium Fusion, Lithium Chloride Taken Out (Thorpe, 1912)

Lithium salts from lepidolite by Troost's method: the powdered mineral is fused with barium carbonate, barium sulphate and potassium sulphate, the alkali sulphate layer turned into chlorides with barium chloride, and the lithium chloride dissolved out with alcohol and ether. The saline chlorides left behind are the residue in which Bunsen found rubidium. The fusion separates into two layers: barium silicate and sulphate below, white potassium and lithium sulphate above. Source: T. E. Thorpe, Dictionary of Applied Chemistry vol. III (1912), p. 338. Picture: the book's text.