The kinetics of the dissolution of iron in sulfuric acid was investigated by polarizaton measurements in the presence of iodide ions or carbon monoxide as an inhibitor. The measurements included an oscillographic study of transient phenomena as well as steady states. The adsorption of iodide ions on iron was measured as a function of iodide concentration and anodic current density. The effects of iodide ions and carbon monoxide depend on the amount of inhibitor adsorbed on the iron surface. A possible mechanism for the dissolution of iron in the presence of iodide ions and carbon monoxide has been developed in analogy to the mechanism proposed earlier for the behavior in solutions not containing these inhibitors.

tative basis of classification, the new arrangement eliminates the earlier difficulties with respect to the classification of hydrogen, the properties of the rare earths, the higher valence forms of copper, silver and gold, and the relations of the eighth-group elements. Being based upon ions rather than atoms it gives a clearer representation of the chemical relationships.

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It has been found possible to measure reversible electrode potentials for couples containing technetium and one or more of its hydrous oxides. The procedure disclosed the existence, in films, of technetium in 1+, 2+, and 3+ valence states, besides oxides Tc3O4 and Tc4O7 , and provided direct means for evaluating their free energies of formation from the metal. The previous calorimetrically based free energy of formation of normalTcfalse(OH)4 was confirmed to within 1%. It was found that the radioactivity of technetium is involved in certain processes on the electrode.

Theoretical consideration of possible mechanisms to account for the action of inorganic corrosion inhibitors of the XO4n− type led to the discovery that the pertechnetate ion, TcO4−, inhibits the corrosion of iron and carbon steels in aerated water at temperatures from 23 to 250 C, which was the highest temperature investigated. The chemistry and nuclear properties of technetium are such as to make it very useful in studying the inhibitory process. Thus, it has been shown that inhibition may be achieved without precipitating more than radiochemical traces of reaction products on the metal and even this amount is shown to be most probably of secondary origin. Exposures of two years have not been attended by a continuous increase in the amount of precipitated technetium. It was found that even at 250 C 5 ppm of technetium (5 × 10−5 f KTcO4) in distilled aerated water effectively inhibited the attack on an SAE 1010 steel. The inhibition depends upon the maintenance of some minimum concentration of dissolved pertechnetate, the amount being dependent upon the nature of the metal and its surface activity. The evidence points to a weak, reversible adsorption of the inhibitor ion as the source of inhibition. The perrhenate ion, ReO4−, is very similar to the pertechnetate ion in geometry and charge, yet it was found to have no inhibitory properties under any of several conditions studied. The observations make it clear that inhibition arises from some intra-ionic property and it is tentatively suggested that this is a degree of internal polarity sufficient to induce a short-range electrostatic polarization at the interface, whereby the activation energy for the cathodic part of the corrosion process is increased.