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Electrowinning of iron by electrodecomposition of iron oxide ore in aqueous alkaline electrolytes is an alternative method to reduce CnormalO2 emissions in steelmaking. Laboratory experiments were carried out in a suspension of hematite (normalFe2normalO3) in concentrated NaOH at 114°C . normalFe2normalO3 particles were reduced to metallic iron upon contact with the rotating cathode, while oxygen gas was evolved on the nickel mesh anode. Iron deposits generally adhered well to the carbon cathode substrate. The current efficiency for iron was consistently above 90%, hydrogen evolution on the cathode being the main reason for the inefficiency. The influence of cathode rotation rate, cathodic current density, content of normalFe2normalO3 particles, and concentration of NaOH on the current efficiency and the morphology of the deposit was studied.

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The purpose of this work has been to establish activity data on sodium in liquid aluminum-sodium alloys at temperatures applied by the industry in liquid metal refining processes. A coulometric titration technique using a galvanic cell employing CaF 2 as a solid electrolyte has enabled measurements to be done under very clean and well-defined conditions over the entire range of compositions from highly diluted up to nearly sodium-saturated solutions. Sodium in liquid aluminum of 99.9999 pct purity is found to exhibit strong negative deviation from Henry's law, corresponding to a large negative self-interaction coefficient Na Na as expressed by the equation Na Na ϭ 16,318 Ϫ (191.1 и 10 5 K) и T Ϫ1 . This behavior is normal for elements, which exhibit strong positive deviation from Raoult's law and is explained by formation of Na clusters. The activity coefficient at infinite dilution, ␥ o Na , is expressed by the equation: RT ln ␥ o Na ϭ 86,729 Ϫ 26.237T. The magnitude of ␥ o Na from this equation agrees with the value predicted from the Miedema's semiempirical model. Sodium in liquid Al-Si5 pct alloy of 99.9999 pct purity exhibits strong positive deviation from Henry's law, which is in agreement with earlier investigations of the activity of sodium in liquid Al-Si alloys. The activity coefficient of sodium in pure liquid aluminum at saturation, ␥ sat Na , is expressed by RT ln ␥ sat Na ϭ Ϫ67,476 ϩ 102.33T, which gives for the sodium concentration at saturation x sat Na ϭ exp (8115.5/T Ϫ 12.307). This implies that the solubility of sodium in liquid aluminum at temperatures around the melting point of aluminum is about 10 times higher than previously reported and decreases rapidly with increasing temperature, possibly due to a decreasing stability of Na clusters. Analysis of the experimental conditions used by previous investigators supports these findings.

In the electrodeposition of cobalt in chloride electrolytes the evolution of hydrogen is a parasitic reaction. On a rotating platinum disc electrode the current efficiency was calculated as the charge used for anodic dissolution of cobalt at a potential where no other reactions were taking place, divided by the total cathodic charge used for cobalt deposition. The results show that the current efficiency could be measured accurately in this way. In part I the current efficiency and deposition potential are studied as a function of current density and pH. The results show an increase in current efficiency with increasing current density, pH and temperature. The results also indicate a change in the reaction mechanism for electrodeposition when the pH is changed.