COLUMBIUM or NIOBIUM, a metallic chemical element, which has, as yet, found little application in the arts. First ob served in 1801 by C. Hatchett in a New England mineral, since named columbite, it was identified by Rose in 1844. The metal was first prepared by Blomstrand (1866) by reducing its chloride with hydrogen. Later its oxide was reduced, by Moissan in the electric furnace in contact with carbon and by Goldschmidt by the use of aluminium powder.
Columbium, whose symbol is Cb or Nb, is a steel-grey metal, atomic number 41, atomic weight 93.1, of specific gravity 7•06 and melting point 1,95o° C. It has nearly the same hardness as wrought iron in massive pieces, is malleable and may be welded. It burns on heating in air, is scarcely attacked by hydro chloric or nitric acid, but is soluble in warm concentrated sul phuric acid. It is related to vanadium and tantalum chemically and occurs associated with the latter most frequently in nature; the chief minerals being tantalite, columbite, fergusonite and yttrotantalite. With other elements it is found in pyrochlor, euxenite and samarskite. Three oxides of columbium are known, namely the dioxide, the tetroxide, and the pentoxide, whilst a fourth oxide, columbium trioxide, has been described by E. F. Smith and P. Maas Columbium tetroxide, is obtained as a black powder when the pentoxide is heated to a high temperature in a current of hydrogen. It is unattacked by acids. Columbium pentoxide, is obtained from columbite after the removal of potassium tantalifluoride. (See TANTALUM.) The mother liquors are concen trated, and the double salt which separates, is de composed by sulphuric acid, or by continued boiling with water. The pentoxide is a white amorphous infusible powder, which when strongly heated in sulphuretted hydrogen, yields an oxysulphide. Several hydrated forms are known, yielding salts known as co lumbates. A percolumbic acid, has been prepared by P. Melikoff and L. Pissarjevski (1899), as a yellow amorphous powder by the action of dilute sulphuric acid on the potassium salt, which is formed when columbic acid is fused in a silver cru cible with eight times its weight of caustic potash.
Columbium trichloride, is obtained in needles or crystal line crusts when the vapour of the pentachloride is slowly passed through a red-hot tube. When heated in a current of car bon dioxide it forms the oxychloride and carbon mon oxide. Columbium pentachloride, is obtained in yellow needles when a mixture of the pentoxide and sugar charcoal is heated in a current of air-free chlorine. It melts at 194° C (H. Deville) and boils at 240.5° C. It is decomposed by water, and dissolves in hydrochloric acid. Columbium oxychloride, formed when carbon tetrachloride and columbic acid are heated together at 44o° C, forms a white silky mass which volatilizes at about 400° C. It deliquesces in moist air, and is decomposed violently by water. Columbium pentafluoride, is obtained when the pentoxide is dissolved in hydrofluoric acid. It is only known in solution; evaporation of the solution yields the pent oxide. The oxyfluoride, results when a mixture of the pentoxide and fluorspar is heated in a current of hydrochloric acid. It forms many double salts with other metallic fluorides. These double salts belong to an isomorphous series in which fluorine is replaced atom by atom by oxygen, e.g., and