Browsing by Author "Smith, Alec L."

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Interaction between Silver Iodide Surfaces in the Presence of Specifically Adsorbed Ions
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (08), 1974) Melville, James B.; Smith, Alec L.
Interaction pressures between approaching identical semi-infinite plates are examined for Agl in aqueous solution in the cases of constant Ag+/I~ charge, constant total charge, constant wall potential 0o and constant diffuse layer potential 0d. For this purpose the adsorption isotherm for K+ ions on silver iodide is taken from a combination of potentiometric titration and electrokinetic data. The physically unrealistic result of repulsive pressures tending to infinite values at short separations, which occurs for constant total charge, is shown not to occur for constant surface charge when the adsorbed charge due to indifferent counter ions can equilibrate on approach.
Observation of Weak Primary Minima in the Interaction of Polystyrene Particles with Nylon Fibres
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Boughey, Marie T.; Duckworth, Ralph M.; Lips, Alexander; Smith, Alec L.
The deposition of sub-micron polystyrene particles onto dispersed nylon fibres has been studied as a function of pH and ionic strength in the vicinity of the iso-electric point of the nylon. The presence of weak primary minima is inferred from the reversibility of the deposition under conditions where the interacting surfaces are oppositely charged. The observed deposition rates can be described by a simple kinetic equation containing rate constants for particle capture by the surface and particle escape from it. The observed equilibrium deposition isotherms have an initial linear region and a plateau but deviate from Langmuirian behaviour in the direction of indicating lateral attractive interactions between deposited particles. Initial linear slopes have been related to surface excess integrals of the form [graphic omitted] {exp[–u(x)/kT]– 1}dx, where u(x) is the interaction potential between a particle and the surface (assumed flat) at a separation x. The interaction potentials so inferred are orders of magnitude lower than those predicted by existing theory of the dominant electrostatic interaction. It is suggested that absorption of water by the nylon (∼9 % by weight), rendering the surface diffuse, is a controlling factor.
Rapid Flocculation Rates of Polystyrene Latex Dispersions
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Hatton, William; McFadyen, Peter; Smith, Alec L.
An automatic flow ultramicroscope particle counter with laser illumination has been employed to determine absolute rates of coagulation of monodisperse polystyrene latex dispersions in excess electrolyte. The particles ranged in size from 0.37 µm to 1.9 µm diameter. Experiments were designed to test the effects of initial particle concentration and the temperature. At low particle concentrations, or by extrapolation to such a condition, close agreement was found between experimental values and those predicted by current theory.
Surface and electrokinetic potentials of interfaces containing two types of ionising group
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (05), 1978) Rendall, Henry M.; Smith, Alec L.
A general treatment is presented of the variation of the “wall” potential ψ0 with pH for an interface which derives its surface charge from the ionisation of two separate types (e.g., amino and carboxyl) of ionisable surface group. Simple forms of the derived equation are obtained under limiting conditions. The results are compared and contrasted with a published model which considers a single type of ionisable surface site. The present model gives a satisfactory description of electrokinetic measurements on a polyamide dispersion.