The mechanism of the hydrated nickel hydroxide electrode, used in the nickel cadmium battery, is a matter of considerable controversy. Potential sweep experiments were performed on film nickel hydroxide electrodes in an effort to determine the oxidation‐reduction mechanism. The existence of more than one reduced structure was confirmed and the structure known as α‐nickel hydroxide was studied in detail. A model based on a reversible charge transfer step with a rate‐controlling diffusion process was used to analyze the data. The results were in good agreement with the model. The over‐all reaction for α‐nickel hydroxide was found to be 2][3normalNiOH2·2H2O+6 OH−+3/2KOH⇄2][3normalNiOOH·7/2H2O·3/4KOH+3H2O+6e− The rate‐controlling process, which was assumed to be proton diffusion, was found to have a diffusion coefficient of approximately 2 × 10−9 cm2 sec−. Evidence for the formation of a poorly conducting layer during discharge of the electrode was found and capacity loss was attributed to this.

The diffusion coefficient for protons moving in the hydrated nickel hydroxide lattice has been determined using a potential step technique. It was found to have the value about 3.1×10−10 cm2 sec−1 during charging and 4.6×10−11 cm2 sec−1 during discharging for the nickel hydroxide structure usually found in the nickel electrode of the nickel‐cadmium battery. The temperature dependence of the coefficient has been determined, and it has been concluded that the proton moves in the lattice by thermal diffusion. The enthalpy of diffusion was found to be 2.2 kcal deg−1 mole−1 during charging and 2.3 kcal deg−1 mole−1 during discharging of the electrode.

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A complete structure determination has been made of sodium pyrophosphato decahydra.te, which is monoclinic, with space group I2/c and cell dimensions a ----17-93, b -----6.96, c ----14.85/~, fl ----118 ° 31'.The atomic parameters were found by the analysis of the three-dimensional Patterson function, using the short P-O vectors as the starting point. It was refined by difference maps of electron density, to a residual error factor of 0.20-0.23. The P~O~ ion consists of two PO4 groups sharing an oxygen, with a P-O-P angle at the central oxygen of 134 °. The sodium ions have octahedral groups of water molecules together with some of the oxygens atoms from the P2Ov groups, and the structure is described in terms of the sharing of oxygens and waters by these groups.