Scandium oxalate, Sc₂(C₂O₄)₃

Solubility of scandium oxalate in acids.

Scandium oxalate, Sc₂(C₂O₄)₃.5H₂O, may be precipitated from an aqueous solution of a scandium salt by oxalic acid, and when air-dried, forms a white, crystalline powder of the above composition. It is slightly, but distinctly soluble in water. In dilute acids it is less soluble than the oxalates of the rare earth elements, as will be seen from figs., and, unlike the rare earth oxalates, it is more soluble in dilute sulphuric than in hydrochloric acid. In these respects it resembles thorium oxalate. The solubility data are as follows (see fig.).

Boiling 10 per cent, hydrochloric acid dissolves 0.8 per cent, of its weight of hydrated scandium oxalate; the 20 per cent, acid, 1.8 per cent, of oxalate (Meyer and Winter).

When dried over sulphuric acid, the trihydrate, Sc₂(C₂O₄)₃.3H₂O, is obtained; at 100° the dihydrate, and at 140° the monohydrate is produced (Crookes).

Scandium oxalate dissolves readily in hot ammonium oxalate solution, less readily in potassium or sodium oxalate, and on cooling, crystalline double oxalates of the type Sc₂(C₂O₄)₃.3R₂^IC₂O₄.10H₂O, or R₃^I[Sc(C₂O₄)₃].5H₂O, separate out. Scandium oxalate has a strong tendency towards double salt formation, and when a solution of sodium or potassium oxalate is added to one of scandium nitrate, the crystalline precipitate first produced is a double oxalate of the type Sc₂(C₂O₄)₃.R₂^IC₂O₄ (Meyer and Wassjuchnow).