Current efficiency of alloy plating and the electrochemical equivalent of an alloy

Electrochemical equivalent is defined in the context of the calculation of the current density of electrodeposition of alloys. In order to calculate the current efficiency of the alloy deposition process, it is necessary to know the mass of the alloy expected to be deposited per Faraday of electricity when no other electrode reaction than the alloy deposition occurs at the electrode surface. Since alloys do not have a faxed composition, in other words, since alloys do not obey the law of definite properties, it is not possible to calculate theoretically the mass of the alloy deposited per Faraday. Thus there exists no fixed value for the electrochemical equivalent of an alloy. However, the current efficiency for an alloy deposition process can easily be calculated, without any need to know or define the electrochemical equivalent of an aUoy. An analysis of the alloy deposited can be obtained experimentally and the corresponding Faradays utilised can be calculated. The ratio of this quantity to the number of Faradays passed through the cell would give the current efficiency for the alloy deposition process. The above a..<;pects are dealt with in detail in the paper

Electrodiffusion and charge separation

It has also been realised quite early that there existed some inconsistencies in Planck’s theory of diffusion potentials, regarding the electroneutrality principle. Many workers have tried, to account for the inconsistencies, based on the charge separation over small intervals of time, distance and the variation of dielectric constant across the junction etc. However, in steady state, these theories adapt themselves, to give Planck’s result. It is proposed to discuss in this paper this problem from the definition of the ionic current and the Nernst-Planck flux equations. This leads to the conclusion that, with the assumptions made by Planck, one can only arrive at the equilibrium potential or the Nernst reversible potential, and cannot get with the given initial and boundary conditions any charge separation even in the nonsteady stat

A novel method of current efficiency determination

A simple and rapid method, based on the open-circuit decay of potential, is described for the determination of the current efficiency with which metals are electrodeposited. The advantages and disadvantages of the method are discussed

Mechanism of action of selenious acid in the electrodeposition of manganese

The effect of selenious acid as an addition agent in the electrodeposition of manganese was studied by analysing the current-potential curves for manganese deposition. The mechanism of action of this addition agent was found to be essentially similar to that proposed for sulphur dioxide, namely to affect the manganese deposition indirectly by influencing the hydrogen evolution reaction which is a parallel reaction at the electrode surface

Effect of sulphanilamide on citric acid production by Aspergillus niger

It has been shown that the mechanism of resistance to sulphanilamide toxicity in E. coli involves the enhanced formation of coenzyme A which is required for the acetylation of the drug. A similar increase in the coenzyme A levels of the cells has been observed in S. cerevisiae subjected to sulphanilamide toxicity. An interesting observation made in the experiments with S. cerevisiae was that, concomitant with the increase in the coenzyme A levels of the cells, there was an enhancement in the levels of ergosterol as well. In view of the known role of coenzyme A in sterol biosynthesis, it was considered of interest to investigate the effect of sulphanilamide toxicity on other biosynthetic processes involving the action of coenzyme A. Accordingly the effect of the drug on citric acid production by a citric acid-accumulating strain of Aspergillus niger was investigated. The results presented here show that the production of citric acid by the mould is markedly inhibited by sulphanilamide

Kinetics of hydrogen evolution on a stainless steel electrode

The kinetic parameters for the hydrogen evolution reaction on a stainless steel substrate have been obtained from a study of the steady-state polarization curves as well as the galvanostatic transients. The high Tafel slope obtained in the steady-state polarization measurements was ascribed to the presence of an oxide film present on the surface of the stainless steel electrode

Magnetite biomineralisaton in termites.

Experimental evidence exists for magnetoreception in termites, a major component of the soil macrofauna in many tropical countries. This preliminary study identifies for the first time the presence of biogenic ferrimagnets (magnetite?) in two species of termite (Nasutitermes exitiosus and Amitermes meridionalis), based on magnetic measurements of whole termite specimens and individual body sections, and analysis by electron microscopy of magnetically-extracted grains. The magnetic measurements indicate the presence of very small concentrations of magnetic material, with more magnetic grains in the thorax/abdomen region compared to the head. Magnetic interaction, due to clustering of grains, is also identified by the measurements. Analysis of magnetic extracts by transmission electron microscopy identifies the presence of uniquely ultrafine (10nm) and unidimensional grains of ferrimagnetic material, unequivocally distinct from any possible extraneous magnetite sources, such as ingested soil. Hence, this provides firm evidence for biogenic formation of this magnetic material by these two termite species. Such ultrafine grains would be superparamagnetic, ie. incapable of carrying a permanent magnetic moment, unless they were sited in clusters of interacting grains, when some remanence-carrying ability - and hence magnetotaxis - would be possible