S. Darwish

Adsorption of bromide ion on polarized iron

Abstract Electrochemical polarization measurements have been carried out in order to investigate the effect of bromide ion on the dissolution of iron in air-free aqueous sulphuric acid. The surface coverage has been calculated from the observed cathodic shift. Bromide ion affects both the cathodic hydrogen evolution and the anodic dissolution of iron. Deviations from the Langmuir isotherm have been observed. Comparison is made with the effect previously reported for other halides.

A review on the electrochemistry of tin

Abstract The recent literature on the electrochemistry of tin has been reviewed since 1970. In order to avoid unnecessary length, only papers which contain significant contributions are included. The review has been written in a bibliographical manner, and papers are arranged chronologically in each section. In this manner, the reader can follow the developments in each section as new techniques and new ideas are introduced, and can easily draw conclusions regarding the agreement and contradictions between the results of various authors. Furthermore, he has the liberty of formulating plans for future research, without being biased by the reviewers personal opinions. The contents of this review have been classified into twelve sections: 1. (1) Anodic dissolution of Sn and tinplate. 2. (2) Corrosion of Sn and tinplate. 3. (3) Passivity and anodic passivation of Sn, tin alloys, and tinplate. 4. (4) Cathodic passivation in dichromate. 5. (5) Electrodeposition (electroplating) of Sn and Sn alloys. 6. (6) Electrochemical properties of electroplated Sn alloys. 7. (7) Semi-conducting properties of SnO 2 . 8. (8) Some industrial aspects of tinplate. 9. (9) Cathodic processes. 10. (10) Electron transfer studies between soluble Sn species. 11. (11) Photo-effects. 12. (12) Miscellaneous studies. Each section written as concisely as possible, and 190 references are included.

Kinetics of the ferro—ferricyanide electron transfer reaction on anodically formed tin oxide

Abstract The kinetics of electron transfer reaction across a layer of tin oxide formed on tin electrodes were measured in borate buffer pH = 8. The effect of concentration of the redox system, Fe(CN)3−6/Fe(CN)4−6, on the rate of the process and also the effect of oxide thickness were measured by cathodic and anodic polarization curves. A reaction order of 0.7 with respect to the redox system was found. An exponential dependence of the exchange c.d, i0, on film thickness was interpreted on the basis of direct tunnelling through the oxide. Thick films formed at potentials within the O2-evolution range showed increase of i0 as function of film thickness.

A treatment of adsorption equilibria of Br− and I− ions on Fe in the active state☆

The equilibrium treatment of the adsorption of Br− and I− ions on active Fe is extended to isotherms other than Langmuirs. Mobility of adsorbed particles leads to an isotherm analogous to Langmuirs at low surface coverage. A new approach to repulsion interaction is discussed, which describes the results at both extremes of surface coverage. In the intermediate range, however, the results are best explained on the basis of the Temkin isotherm.

Potentiometric study of aqueous cyanide complexes of mercury(II)

Abstract The stoichiometry of the aqueous cyanide complexes of Hg(II) has been investigated by the potentiometric method at constant ionic strength. Measurements have been carried out in the range 1:1 to 1:20 (Hg 2+ :CN − ), and for H 2+ concentrations between 0·00005 and 0·15 M. The formation of both Hg(CN) 2 and [(Hg(CN) 4 )] 2− is accompanied by an inflexion. The occurrence of [(Hg(CN) 3 )] − is not detected. The existence of mononuclear complexes with q > 4, eg 5, 6, and probably 7 is indicated. Stability constants are calculated from the relation between the formal potential of the complex and the logarithm of CN − concentration.