This curious metal occurs in small quantities in some ores of tin and tungsten, but more abundantly in the uncommon minerals tantalite (containing 49 1/2 to 76} per cent. of the oxide), columbite (22f to 28 1/2), yttrotantalite (10), and ferguson-ite (6 1/2). An impure form of the metal (it seems never to have been isolated in a perfectly pure condition) may be prepared from any of these minerals in the following manner. The mineral is finely powdered, and fused with 3 times its weight of acid potassium sulphate; the fused mass is completely boiled out with water; the residue is digested with ammonium sulphide (to remove the tin and tungsten, while the iron is thereby converted into sulphide), washed, and boiled with concentrated hydrochloric acid; tantalum hydroxide is left, and is washed with boiling water, and ignited; the silica generally present in the resulting oxide is got rid of by dissolving in hydrofluoric acid and evaporating with sulphuric, and any trace of niobic acid is removed by adding 1 part potassium fluoride to every 4 parts of the oxide present in the boiling hydrofluoric acid solution, and boiling down till 1 grm. of the oxide is contained in 7 cc. of the solution; the needle-like crystals of potassium tantalofluoride, which separate out on cooling, are washed till the wash-water gives no orange-red precipitate on standing for 2 hours, but a sulphur-yellow one with tincture of galls, further quantities of this salt being obtained by evaporating the mother-liquor and wash-waters; this salt, mixed with an equal weight of concentrated sulphuric acid, is gradually heated to 752° F. (400° C); when the residue is boiled out with water, there remains a granular compound of tantalum oxide and sulphuric acid, which is decomposed on ignition, the sulphuric acid being completely removed by adding ammonia carbonate.

The metal obtained as a black powder, by igniting potassium fluotantalate with potassium, is soluble only in hydrofluoric acid; it ignites and burns when heated in the air, in chlorine gas, or in sulphur vapour. ____