Mutual diffusion coefficients, electrical conductances, osmotic coefficients, and ionic transport coefficientsl ij for aqueous CuSO4 at 25°C

Anomalous diffusion is the rule in concentration-dependent diffusion processes

“…In this communication, we provide confirmation of our hypothesis by analysing one-dimensional diffusion experiments of aqueous CuSO 4 in pure water carried out by Carey et al [1]. The concentration-dependent diffusivity of CuSO 4 solutions was established in [28] using Rayleigh interferometry. Besides the technical aspects of the optical method (which will not be recalled here), the experiments essentially consisted of establishing a small concentration step (generally smaller than 0.04 mol l −1 ) between two solutions of aqueous CuSO 4 and calculating the diffusivity, D(C), from measurement of the displacement of the concentration front.…”

“…Two complementary remarks must be made at this point: (1) even a small departure from the t 1/2 relation has important quantitative consequences since the diffusion process is cumulative and (2) the fact that the diffusion equation cannot represent the phenomenon at some time in the experiment implies that it cannot represent the phenomenon at any future time, for the same reason. It must also be pointed out that, although the diffusivity coefficients of figure 1 were calculated assuming normal Fickian diffusion (instead of subdiffusion) in [28], we do not expect large changes in the diffusivity curve in this case. The successive concentration steps applied to measure the different values of the CuSO 4 diffusion coefficient as a function of concentration were small and systematically lower than 0.04 mol l −1 below 0.8 mol l −1 (see table 1 in [28]): this represents only a few per cent of the full range of concentration investigated in [28].…”

“…It must also be pointed out that, although the diffusivity coefficients of figure 1 were calculated assuming normal Fickian diffusion (instead of subdiffusion) in [28], we do not expect large changes in the diffusivity curve in this case. The successive concentration steps applied to measure the different values of the CuSO 4 diffusion coefficient as a function of concentration were small and systematically lower than 0.04 mol l −1 below 0.8 mol l −1 (see table 1 in [28]): this represents only a few per cent of the full range of concentration investigated in [28]. It is thus reasonable to assume that each diffusion experiment was conducted at an almost constant diffusivity, D(C): the application of the Fickian hypothesis was thus justified as a first approximation.…”

A Relationship Among the Transport Properties of Some Concentrated Aqueous Solutions of Binary Electrolytes

“…Calculation of ~.--In order to evaluate ~ over a wide range of concentration, physical property data were obtained from Ref. (3) and (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). In Ref.…”

“…In Ref. (3) and (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), critically analyzed thermodynamic and transport property data for 17 electrolytes were used to calculate the Onsager transport coefficients lij. These same data were sufficient to calculate ~ in the present work.…”