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An a‐c square wave technique was used to study resistance and double‐ layer capacity during film formation on silver electrodes in KOH solutions. The peak in the voltage‐time curve at constant current anodization is shown to coincide with complete surface coverage by Ag2O and is not an ohmic resistance, but rather an overvoltage effect. Evidence for the existence of an unstable higher oxide than normalAgO (or additional oxygen) during oxygen evolution is presented. Microvolumetric gas measurements with large area electrodes on open‐circuit decay also support this conclusion. The duration of the upper voltage plateau of the voltage‐time curve during discharge of normalAgO electrodes is determined by contact phenomena among individual normalAgO particles, in particular by separation and passivation of the remaining normalAgO by insulating surface layers of Ag2O .

The solubility of Ag20 and AgO in alkaline electrolytes has been studied with a polarographic technique, using a rotating platinum electrode. Only a, monovalent (and no divalent) silver species could be detected in solutions which had been in intimate contact with AgO powder over prolonged periods of time.Quantitative measurements of the solubility of Ag~O in KOH solutions ranging from 1-14 moles per liter, were carried out utilizing a potentiometric titration method. The solubility has a maximum at about 6N KOH where it reaches a value of 4.8-10-4N.The rate of the decomposition reaction 2AgO~ Ag~O + 1/2 O2 in alkaline electrolytes was investigated with a very sensitive microvolumetric method. The reaction rate increases with increasing hydroxyl ion concentration and is sensitive to day-light. The decomposition appears to proceed at the solid-liquid interface. Any divalent silver dissolving in minute amounts into the electrolyte is decomposed rapidly due to its instability. The decomposition proceeds at a rate of about 16% in 1 year at 30~ and 49% in 1 year at 45~ This reaction can contribute significantly to the self-discharge of AgO-Zn batteries.Anodic oxidation of silver in alkaline solutions is a two-step process. First, a layer of monovalent Ag20 is produced on the metal. Subsequently, when this layer has reached a critical thickness and mass transport through the layer becomes slow, Ag20 is oxidized to AgO. Further anodization leads to evolution of oxygen. Simultaneously, the oxidation of metallic silver continues at a very low rate. There is also evidence of the formation of highly unstable "higher oxides" than AgO during prolonged anodization.The standard potential of the Ag/Ag~O couple in alkaline solutions is 0.342 v (1) and the potential of the Ag~O/AgO couple, 0.604 v (2). If an electrode contains both metallic silver and AgO, a local action mechanism must proceed (3, 4) with a driving force of 0.262 v or --6.05 kcal, according to 2Ag + 2(OH)-~-~--~ Ag~O + H20 + 2eEo~ 0.342with the first reaction proceeding in the forward direction, and the second reaction in the backward direction, resulting in Ag + AgO ~ Ag20 AG = --6.05 kcal This local action mechanism should be a fast process, because the individual component electrode reactions are known to have high exchange currents. Measurements of the double layer capacity and the interface resistance during anodic formation of Ag20 films (3, 5, 6) give an insight into the mechanism of oxidation. The double layer capacity decreases during build-up of the Ag~O layer, apparently due to increased separation of the charge layers in the solution and on the metal. At the same time, the interface resistance increases sharply, indicating restriction of mass transfer. The resistance decreases again when the formation of AgO begins. This decrease in resistance must be correlated with the breakdown of the Ag~O layer, and with the high electric conductivity of the divalent oxide. The conductivity is in the order of 7.10 -~ ohm -1 cm -1 and increases with increasing tempe...

Nickel-molybdenum, cobalt-molybdenum, and iron-molybdenum alloys have been electrodeposited, from aqueous solutions containing sodium molybdate, the sulfate of the codeposited metal, sodium citrate, and ammonium hydroxide. Typical baths were made up with 0.3 M/1 of the codepositing metal sulfate, 0.3 M/1 of sodium citrate, varying amounts of sodium molybdate, and ammonium hydroxide to pH about 10.5. The maximum amount of molybdenum in the electrodeposited alloys depends on the alloying metal. When a typical bath was used, nickel alloys were found to contain up to 20% molybdenum, cobalt alloys contained up to 40% molybdenum, and iron alloys contained about 50% molybdenum. The cathode current efficiency in the above cases ranged from 75-85% for the nickel-molybdenum bath, 50-60% for cobalt-molybdenum, and 10-20% for iron-molybdenum. The effects of pH, concentration, temperature, and cathode current density on cathode current efficiency and alloy composition were studied.These electrodeposited molybdenum alloys were metallic and either bright or light gray in appearance, with a large number of cracks in the bright deposits. Adherence of the deposit to well-cleaned flat cathodes seemed to be good, but adherence to tubing or rods was poor; usually these deposits could be brushed off in flake or powder form.

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