‎"MARIGNAC, C. (JEAN CHARLES). - FIRST SEPARATION OF COLUMBIUM AND TANTALIUM.‎
‎Recherches sur les Combinaisons du Niobium.‎

‎Paris, Victor Masson et Fils, 1866. 8vo. Contemp. hcalf, raised bands, gilt spine. Light wear along edges. Small stamps on verso of titlepage. In: ""Annales de Chimie et de Physique"", 4e Series - Tome VIII. 512 pp. a. 3 folded engraved plates. (The entire volume offered). Marignac's paper: pp. 5-75.‎

Reference : 45989

‎The paper describes his successfull separation of tantalum and columbium, ""and he also shows that columbium is both tri- and pentavalent, whereas tantalum always has a valency of five. The separation is based on the insolubility of potassium fluo-oxyycolumbate."" (Weeks p. 83).‎