Assay of high-purity sodium oxalate traceable to the international system of units by coulometric titration and gravimetric titration

► The purity of sodium oxalate was first determined with the linkage to the SI units. ► The determination methods were examined through three different paths. ► The determination methods with the highest accuracy were presented. ► High accuracy of each titration reaction was newly ascertained. ► The measurement methods presented enable analysts to obtain reliable results.