potassium trihydrogen dioxalate

Chemical properties

colorless or white crystal(s) [MER06]

Physical properties

The monohydrate is a white crystalline solid; monoclinic structure; density 2.13 g/cm³; loses its water at about 160°C; converts to carbonate when ignited; effloresces in warm dry air; soluble in water, 33 g/100 mL at 20°C; a 0.05m solution of K2C₂O₄?2H₂O has a pH 1.679.

Occurrence

Potassium oxalate, along with calcium oxalate, is found in leaves and roots of certain plants. It is used for cleaning and bleaching straw and for removing stains. It also is used in photography, in clinical tests, as a secondary pH standard, and in wet chemical analysis. The analytical application involves standardization of many oxidizing agents in titrimetric analysis.

Preparation

Potassium oxalate can be preparaed by heating potassium formate at 360°C:
2HCOOK →K2C₂O₄+ H₂
The salt is obtained as its monohydrate by neutralization of oxalic acid with a dilute aqueous solution of potassium hydroxide followed by crystallization:
H2C2O4+ 2KOH →K2C₂O₄+ 2H₂O.

Flammability and Explosibility

Non flammable

Purification Methods

Crystallise it from water below 50o. Dry it below 60o at 760mm. [See potassium oxalate above, Beilstein 2 IV 1823.]