Stages in the preparation of potassium manganate from pyrolusite

Abstract

The progress of the reaction between solid KOH and pyrolusite has been shown by X‐ray analysis to proceed via cryptomelane, K₂Mn₈O₁₆, to potassium permanganite, K₂Mn₄O₈, both of which are brown‐black insoluble compounds. The next step would appear to be the formation of an unstable potassium manganite of approximate composition K₂Mn₂O_4–6 which breaks down to varying mixtures of the soluble manganate K₂MnO₄ and insoluble potassium permanganite.