Common alloying elements such as aluminum, zinc, and low concentrations (<1%) of manganese do not appear to be dissolved by chromic acid. If any did dissolve, there should be no interference with the atomic absorption method and interference should be minimal in the acid-base titration because these elements would largely be precipitated as hydroxide during the titration, releasing the equivalent quantity of chromic acid which is titrated. Dissolved metals would cause interference with the chelometric method for active magnesium, but procedures for avoiding these interferences are available (6). Any metal capable of yielding hydrogen with sulfuric acid would be counted as magnesium in the eudiometric method.Magnesium nitride would interfere in the titration method by forming both magnesium and ammonium chromates, and to a lesser extent in AA where only the magnesium equivalent is effective. If the nitride content is determined through hydrolysis followed by any method for ammonia determination (7), corrections can be calculated:

No abstract

The extent of surface oxidation of a smooth platinum electrode and the electrode capacitance were measured for various conditions of anodization. The electrolytic formation of the surface platinum oxide is shown to be a highly irreversible reaction. A mechanism which involves a hydroxyl radical intermediate of the oxygen evolution reaction is proposed for the surface oxide formation reaction. This mechanism is supported by the shapes of the anodic and cathodic charging curves on platinum and the interrelationships of the electrode potential, the electrode capacitance, and the extent of surface oxidation. From these same interrelationships it was also concluded that the steady‐state evolution of oxygen occurs on a surface which has at least one atom of oxygen per surface platinum atom and that the rate‐determining step in the oxygen evolution reaction is the electrolytic discharge of oxygen‐containing radicals which are adsorbed on the electrode surface. The surface oxide is reduced at potentials several hundred millivolts cathodic to the potential required to form the oxide. The reduction of the surface oxide is shown to be a first order reaction. The rate of the reduction increases with increasingly cathodic electrode potential.

Hydrolytic decomposition occurs during the fusion of a eutectic mixture of lithium chloride-potassium chloride containing traces of moisture if the fusion conditions are not controlled. The resultant contamination by hydroxyl ion greatly lowers the utility of this mixture as a fused salt solvent. The effectiveness of various procedures used for preparation of the fused salt solvent was followed by observation of the characteristic polarographic residual current using a platinum microelectrode. A preparative method is described which involves drying the mixture under moderate vacuum, fusion under anhydrous hydrogen chloride, and removal of the hydrogen chloride from the melt.

The surface oxidation of a smooth gold electrode in perchloric acid was studied by constant potential anodization and constant current cathodization under various conditions. The anodic reaction is explained as a mixed process of oxygen evolution and the formation of chemisorbed oxygen atoms which are presumed to take the configuration of auric oxide when more than one layer thick. The grain boundary diffusion of oxygen atoms may account for the residual current and the increase in the extent of oxidation at constant potential. Electron micrographs and double layer capacities are consistent with the other findings.