Abstract: The present invention relates to a method of producing a sodium iron(II)-hexacyanoferrate(II) (Na2-xFe[Fe(CN)6].mH2O), where x is <0.4) material commonly referred to as Prussian White. The method comprises the steps of acid decomposition of Na4Fe(CN)6.10H2O to a powder of Na2-xFe[Fe(CN)6].mH2O, drying and enriching the sodium content in the Na2-xFe[Fe(CN)6].mH2O powder by mixing the powder with a saturated or supersaturated solution of a reducing agent containing sodium in dry solvent under an inert gas. The steps of acid decomposition and enriching the sodium content are performed under non-hydrothermal conditions.