Yttrium oxalate

Yttrium oxalate is an inorganic compound, a salt of yttrium and oxalic acid with the chemical formula Y$2$(C$2$O$4$)$3$. The compound does not dissolve in water and forms crystalline hydrates—colorless crystals.

Synthesis
Precipitation of soluble yttrium salts with oxalic acid:
 * $$\mathsf{ 2YCl_3 + 3H_2C_2O_4 \ \xrightarrow{}\ Y_2(C_2O_4)_3\downarrow + 6HCl }$$

Properties
Yttrium oxalate is highly insoluble in water and converts to the oxide when heated. Yttrium oxalate forms crystalline hydrates (colorless crystals) with the formula Y$2$(C$2$O$4$)$3$•n H$2$O, where n = 4, 9, and 10.

Decomposes when heated:
 * $$\mathsf{ Y_2(C_2O_4)_3 \ \xrightarrow{700^oC}\ Y_2O_3 + 3CO_2 + 3CO }$$

The solubility product of yttrium oxalate at 25 °C is 5.1 × 10−30.

The trihydrate Y$2$(C$4$O$3$)$2$•3H$2$O is formed by heating more hydrated varieties at 110 °C.

Y$2$(C$4$O$3$)$2$•2H$2$O, which is formed by heating the decahydrate at 210 °C) forms monoclinic crystals with unit cell dimensions a=9.3811 Å, b=11.638 Å, c=5.9726 Å, β=96.079°.

Related
Several yttrium oxalate double salts are known containing additional cations. Also a mixed-anion compound with carbonate is known.