<Original Papers>Fundamental Researches on Metallurgical Treatment of Manganese Ores.(VII) : Studies on the Stability of the Electrolyte

The electrolytic deposition of manganese was carried out in a catholyte pH 7 to make the hydrogen evolution at the cathode as suppressive as possible. Though the neutral or weak alkaline solution of the electolyte is favourable to obtaining good current efficiency, divalent manganese ion in its solution is very unstable and leads to the formation of manganese ions of higher valency owing to oxidation of exposure to air ; that is the solution becomes cloudy, then gradually brown, finally precipitates colloidal manganese hydroxide or its oxidation products which is detrimental to manganese deposition because of lowered current efficiency and formation of nodular or treed deposits. So, the writers investigated the stability of the electrolyte of which components were principally manganese and ammonium sulphate, manganese sulphamate and ammonium sulphate, and manganese and ammonium sulphamate mixed solutions. The relationship between the rate of the precipitated manganese to the total manganese in the solution, and various conditions of the solution are compared in Table 1 and Figs.1～4. In another series of experiments the buffering effect of ammonium sulphate and ammonium sulphamate at various manganese concentrations were determined by titration with NaOH solution and are shown in Figs.5～7. Finally, a study was made to determine the possibility of electrowinning manganese using sulphamate bath and the experimental results are shown in Tables 4,5 and Figs.8～11. A comparision between the sulphamate process and the sulphate process is made, pointing out the chief advantages and disadvantages