Potassium oxalate monohydrate is a source of oxalate ion. Oxalic acid (and formic acid) is readily oxidized and combine with calcium, iron, sodium, magnesium, or potassium to form less soluble salts called oxalates.
P 2397 (OTTO) Potassium oxalate, GR 99%+ Cas 6487-48-5 - used as a chelating agent, a purifying agent in the pharmaceutical industry and a precipitating agent in rare-earth metal processing.