Thorium niobate

Thorium Niobate, 5Th02.16Nb205, is prepared by adding thorium sulphate to a solution of potassium niobate, fusing the precipitate with borax and boiling the melt with water containing hydrochloric acid. It forms doubly refracting, prismatic needles density 5-21.7... 

Pyrochlore.—This is a crude calcium niobate which may also contain appreciable quantities of titanium, thorium and cerium, together with smaller quantities of iron, magnesium, the alkali metals, and fluorine. It does not contain chlorine, and it is of interest in that some specimens are remarkably free from tantalum. It occurs in Norway and near Miask in the Ural Mountains. The ore is brown, forms regular octa-... 

Zirconium Niobate.—The salt ZrQ2.5Nb2Os has been obtained in cloudy, rod-like needles, similarly to the thorium salt density 5 14.u This salt is remarkable for its large content of acid oxide. 

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