摘要:

Detailed consideration is given to thermodynamic relationships describing the temperature dependence of the properties of electrified interfaces. Excess entropies are derived for multicomponent systems and in particular it is shown that the effect on the residual excess entropy,S*, of the specifically adsorbed organic species can be directly determined by experiment. Values ofS*in the presence of thiourea (TU) can be understood in terms of the surface excesses of TU and the degree of solvent orientation. The preferred orientation of water is shown to be charge-dependent, under all conditions to be zero at −3 µC cm−2, and largely determined by its molecular polarisability. Temperature-invariant capacities are shown to occur widely and are not easily explained in terms of cluster models or time-dependent solvent orientation.

ISSN:0008-4042    

DOI:10.1139/v81-274

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Discreteness-of-charge effects for simple heterogeneous electron transfer reactions, namely, the self-image effect, the exclusion disc effect, and the effect of local attractive ion–ion interactions, are considered for a variety of reaction sites in the double layer, both in the presence and in the absence of ionic specific adsorption. An expression is derived for the local activity coefficient of the activated complex; this quantity is shown to be a function of both the potential drop across the inner layer and the adsorbed charge density due to specifically adsorbed ions when the standard state is chosen on the basis of the reaction conditions considered in the classical Frumkin theory (reaction site at the outer Helmholtz plane). The consequences of discreteness-of-charge effects for reactions occuring in three different double layer environments of increasing complexity are described. These effects are discussed on the basis of data obtained earlier for the electroreduction of periodate anion in the presence of specifically adsorbed anions.

ISSN:0008-4042    

DOI:10.1139/v81-275

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The electrolyte in the diffuse layer is modelled by a system of charged hard spheres and dipolar hard spheres. Poisson's equation and integral equations for the mean electrostatic potential are derived and the implications worked out for a mean field approximation.

ISSN:0008-4042    

DOI:10.1139/v81-276

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The Poisson–Boltzmann equation for two large charged spheres immersed in an ionic solution with either constant surface charge density or constant surface potential is solved numerically. The repulsion between the spheres is calculated from the electrostatic potential in the double layer surrounding the spheres. Good agreement between this numerically calculated force and the force computed using the Derjaguin formula for spheres with constant surface charge density is found at small separations of the spheres.

ISSN:0008-4042    

DOI:10.1139/v81-277

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The freezing-point depressions of aqueous solutions of the homologous series RNH3Br, where R varies from ethyl ton-octyl, and of sodium decanoate were determined and used to calculate osmotic and mean activity coefficients. In the case of the surfactants octylamine hydrobromide and sodium decanoate, the pre- and post-micellar regions were covered. Activity data at higher temperatures were calculated using previously published thermochemical data. Some difficulties arise in the critical micellar region of sodium decanoate at high temperatures as a result of the large concentration and temperature dependence of the heat capacity data. The activities from freezing point data are compared with those obtained from specific electrodes.

ISSN:0008-4042    

DOI:10.1139/v81-278

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Data are reported on the concentration of Na2SO4required to hold its chemical potential equal to its value in a 0.10045 msolution in pure water for aqueous solutions containing 2-butanol and 1-propanol at six different temperatures. The data were obtained from emf measurements on a galvanic cell without liquid junction containing a sodium reversible glass electrode and a 2-phase lead amalgam – lead sulfate electrode. The results of the measurements are interpreted in terms of the water structure making properties of the organic compound.

ISSN:0008-4042    

DOI:10.1139/v81-279

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Analytical approximation formulae linking ζ potential and electrophoretic mobility have been derived for a variety of limiting conditions. In this paper we present a simplified derivation of an equation first established by Dukhin and his collaborators for a large spherical particle with a thin double layer. Although potentially a very useful expression it has been little used to date, partly because of the complicated nature of Dukhin's derivation and partly because of the lack of a reliable method of testing its validity. The expression compares very favourably with the computer calculations of O'Brien and White, provided κais sufficiently large.

ISSN:0008-4042    

DOI:10.1139/v81-280

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A method previously developed by the authors is used to study the effects of adsorption of ions on the electric double layer interaction between dissimilar colloidal plates immersed in 1:1 electrolyte. For adsorption models which permit the total charge on a plate to change sign, the double layer force remains finite at all plate separations, including zero. For weak adsorption of the ions on the plates the force between two dissimilar plates tends to be repulsive at small separations, looking rather like a weakened constant surface charge density model. Conversely for strong ionic adsorption the force tends to be attractive at small separations, rather as in the constant surface potential model. In this paper we discuss three adsorption models: (1) fixed primary charge density on the plates with secondary adsorption of both counter-ions and co-ions; (2) fixed primary charge density on the plates with secondary adsorption of the counter-ions only, but including the effects of a Stern layer and self-atmosphere potentials; (3) zero primary charge on both plates with equilibrium adsorption of both anions and cations from solution, the net charge density on the plates arising from differential adsorption of the ion types.

ISSN:0008-4042    

DOI:10.1139/v81-281

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The effect of partial charge transfer on the observed capacity of an electrode adsorbing a species from solution is discussed in a general way for the condition of constant fraction of charge transferred. It is confirmed that the width of the peaks is primarily determined by the interaction between adsorbed species. A simple model in which the degree of charge transfer changes rapidly with electrode potential is suggested. This may account for some of the sharp peaks observed experimentally.

ISSN:0008-4042    

DOI:10.1139/v81-282

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Simple arguments, based on perturbation theory, are used to derive expressions for the energy of a bulk ionic fluid and the potential difference in an electric double layer. These expressions are identical to those obtained from the much more elaborate mean spherical approximation.

ISSN:0008-4042    

DOI:10.1139/v81-283

出版商:NRC Research Press    

年代:1981

数据来源: NRC