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(CO)•n HO, where n = 4, 9, and 10.
Decomposes when heated:
The solubility product of yttrium oxalate at 25 °C is 5.1 × 10.
The trihydrate Y(CO)•3HO is formed by heating more hydrated varieties at 110 °C.
Y(CO)•2HO, 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°.