Neptunium(IV) oxalate

Neptunium (IV) oxalate is an inorganic compound, a salt of neptunium and oxalic acid with the chemical formula Np(C$2$O$4$)$2$. The compound is slightly soluble in water, forms crystalline hydrates—green crystals.

Synthesis
Neptunium(IV) oxalate is formed by the oxalic acid precipitation of neptunium (IV) solutions:
 * $$\mathsf{ NpCl_4 + 2H_2C_2O_4 \ \xrightarrow{}\ Np(C_2O_4)_2\cdot 6H_2O\downarrow + 4HCl }$$

Physical properties
Neptunium(IV) oxalate forms a crystalline hydrate of the composition Np(C2O4)2 • 6H2O with green crystals.

It is insoluble in acetone, and slightly soluble in water.

Chemical properties
Neptunium(IV) oxalate decomposes on heating:


 * $$\mathsf{ Np(C_2O_4)_2 \ \xrightarrow{400^oC}\ NpO_2 + 2CO_2 + 2CO }$$

Applications
Neptunium(IV) oxalate is used as an intermediate product in the purification of neptunium.