The dependence of the anomalous codeposition of iron‐nickel alloys on the pH at the cathode surface is investigated. An equation is derived to evaluate the surface pH as a function of bulk pH, rate of hydrogen evolution, buffer concentration, and diffusion conditions. The results obtained on rotating disk electrodes show that anomalous codeposition is due to a suppression of nickel discharge and that suppression occurs only when the surface pH is high enough to cause hydroxide formation. A type of mechanism is proposed by which the adsorption of ferrous hydroxide suppresses the deposition of nickel but permits a high rate of iron discharge. Experimental results which support this mechanism are discussed. This type of mechanism could be of general importance for other systems exhibiting anomalous codeposition.

No abstract

termining step seems to be excluded. We are left with scheme (b). Thus, as previously pointed out, rate determining hydroxyl discharge should lead to a Tafel slope of 2RT/F, and no ethylene pressure dependence, at the extreme conditions of intermediate species coverage. Furthermore the connection of the transient behavior with coverage of C14-carbon species, mentioned above, can be understood when it is realized that this phenomena (shown in Fig. 12) occurs only at about --150 mv (i.e., about --150 mv from passivation potential). Here OH-discharge becomes comparable in rate to the rate of build of oxidizably organic species, whence the reaction of OH radicals with the organic material on the electrode results in a decrease in organic species surface concentration, and a corresponding increase in area available for OH-discharge. The result of more extensive OH-discharge leads finally to surface oxide formation and passivation, as discussed above.It should be noted that while the above conclusions are consistent with the data, much more elaborate experimental work is required to prove the complete truth of our conclusions. Manuscript

The potential and concentration dependent adsorption of benzene, naphthalene, and phenanthrene at the gold/electrolyte interface has been investigated using a 14C‐radio tracer technique. For a fixed concentration of organic material the adsorption peak was found at about +500 mv (NHE) and the potential‐adsorption curve was bell shaped, adsorption decreasing with potential on either side of the peak. An analysis of the adsorption isotherms for naphthalene leads to the conclusion that naphthalene lies flat on the electrode surface. Comparison of the extent of adsorption of the aromatic hydrocarbons with cyclohexane, n‐octanoic acid, and n‐decanoic acid (no detectable adsorption) indicates that aromatic compounds have a higher binding energy with metals than the corresponding aliphatic compounds. The added binding energy for aromatic molecules is attributed to their π‐electron systems. Finally a comparison of mercury with gold points to the stronger binding energy of water to gold than to mercury.