1. A reproducible electrode, which gives a constant and reversible potential of active nickel was obtained by using powdered nickel reduced with hydrogen directly in the cell and also using an apparatus which allows the cell to be filled with the electrolyte entirely in the absence of air. 2. The potentials of the reduced nickel powder in 0.05 M and 0.005 M nickel sulphate solutions both at 25°C. and 18°C. were measured in an atmosphere of hydrogen. 3. The normal electrode potentials of nickel were calculated from these observed potentials on the ground of two different concepts of the strong electrolytes, one being that the ion concentrations calculated from the conductance viscosity ratios are involved in the expression of the electromotive force of a concentration cell and the other being that the ion activities are involved. The average values of these normal electrode potentials are −0.2496 volt (25°C.) and −0.2508 volt (18°C.) at one molal ion concentration, and −0.2480 volt (25°C.) and −0.2492 volt (18°C.) at one molal ion activity. 4. The change in free energy of nickel electrode reaction per equivalent, that is, (Remark: Graphics omitted.) was calculated from the above electrode potentials.
(1) The oxidation velocity of sodium sulphite in sodium carbonate solution of various concentrations was observed. The oxidation velocity was independent of the concentration of sodium sulphite under the condition of the present experiment, and the velocity constant was expressed as a linear function of the concentration of sodium carbonate approximately, when CNa2CO3 is greater than about 0.02 normal. (2) The effect of temperature was small. (3) The dissolution velocity of oxygen into sodium carbonate solution of various concentrations was obtained indirectly.