Diffusion In Liquid Systems Research Articles

Diffusive mass transfer by nonequilibrium fluctuations: Fick’s law revisited

Recent experimental and theoretical works have shown that giant fluctuations are present during diffusion in liquid systems. We use linearized fluctuating hydrodynamics to calculate the net mass transfer due to these nonequilibrium fluctuations. Remarkably, the mass flow turns out to coincide with the usual Fick's one. The renormalization of the hydrodynamic equations allows us to quantify the gravitational modifications of the diffusion coefficient induced by the gravitational stabilization of long wavelength fluctuations.

Importance of Thermal Diffusion in High Subcritical and Supercritical Aqueous Solutions

We have reviewed our experimental and theoretical studies of irreversible thermodynamics of non-isothermal aqueous systems, with particular emphasis on the investigation of thermal diffusion phenomena, via electrochemical methods. By employing Agar’s hydrodynamic theory, and by using the experimentally-derived standard entropies of transport, $S_{2}^{⇒t0}$, at temperatures from 25 to 125°C, we have calculated high temperature $S_{2}^{⇒t0}$ values, which exhibit a dramatic rise when the temperature increases above 250°C Recently reported experimental data for thermal diffusion in NaNO3 aqueous solutions at supercritical temperatures and pressures by Butenhoff et al. have allowed us to test the validity of our calculations at temperatures up to 450°C. The significance of thermal diffusion in liquid systems with forced convection is discussed, and it is concluded that, as the Lewis number and the Soret coefficient increase, the impact of thermal diffusion on mass transport becomes increasingly important at higher temperatures. We also concluded that the use of an electrochemical cell with forced convection could be a promising experimental technique for determining Soret coefficients for aqueous solutions at elevated temperatures.

Importance of thermal diffusion in high temperature electrochemical cells

The significance of thermal diffusion in liquid systems with forced convection has been investigated over a wide range of temperature. Numerical calculations have been carried out for the case of dilute liquid solutions that flow into the entrance region of a tube or an annulus, and the theory has been developed for a first order chemical or electrochemical reaction that takes place on the electrode surface. As an example, dilute aqueous electrolyte solutions at sub-critical temperatures (up to 350°C) have been considered. As the Lewis number and the Soret coefficient increase, the impact of thermal diffusion on mass transport is predicted to become increasingly important at higher temperatures. Simple analytical relations for describing thermal diffusion effects in liquid solutions subject to forced convection have been derived, and good agreement between these analytical solutions and numerical results is shown. The use of an electrochemical cell with forced convection could be a promising experimental technique for determining Soret coefficients for electrolyte solutions and liquid mixtures at elevated temperature.

Measurements of diffusivities in liquids by the dispersion method

A combination of convective and diffusive mass transfer is advantageous when molecular diffusion in liquid systems is investigated because the measurements can be made in a relatively short time, with small concentration differences, and in a wide range of temperatures and pressures. The principle of the experimental method, the apparatus and the possibilities of data evaluation are discussed. The results of test measurements are presented.

Binary diffusion in liquid systems

Binary diffusion in liquid systems

Semi‐empirical formulae for the prediction of diffusion in liquid systems

AbstractA critical survey of the published theoretical and experimental approaches to diffusion in liquids is presented. A study of the effects of temperature and viscosity demonstrates that the Stokes — Einstein equation and other relations derived from the hydrodynamic theory can only be applied in special cases. Correlations based on Eyring's absolute rate theory are shown to predict diffusivities more accurately in most cases at the expense of additional complications some of which are shown to be unnecessary.

Diffusion in liquid systems. II. Computer-assisted measurement of diffusion coefficients at various temperatures

Diffusion in liquid systems. II. Computer-assisted measurement of diffusion coefficients at various temperatures

A critique of some approximate theories of multicomponent diffusion in liquid systems

Various approximate theories of diffusion in multicomponent liquid systems are based upon the existence of kinetically independent mechanisms, one for each diffusing species. The principles of irreversible thermodynamics are used to show that such theories cannot generally be valid even as approximations except for the trivial case of thermodynamically ideal systems. Multicomponent diffusion processes are thus generally coupled. Consistent models must involve more than kinetically independent one-body processes.

Mach-Zehnder Interferometer for Diffusion Measurements in Volatile Liquid Systems

The constructional details and method of operation of an optical diffusiometer are described. The apparatus makes use of a Mach-Zehnder-type interferometer, which has not previously been employed for the study of diffusion in liquid systems. The apparatus has been developed for the study of liquid systems whose components are volatile organic solvents. For this purpose a diffusion cell of novel design has been constructed. The diffusiometer has been checked using the system sucrose-water at 25°C and values of the diffusion coefficient found over six determinations are within 0.2% of the reported value. With volatile liquids, the accuracy claimed is only 1%, although duplicates usually agreed to within 0.5%.

Solutions of Electrolytes and Diffusion in Liquids

This review reffects the interests of the authors in that it deals principally with the topics of thermodynamics, conductance, and diffusion in electrolyte solutions. However it seemed desirable to include in the discussion of diffu­ sion data a treatment of diffusion in liquid systems generally, since the fundamentals of the problem are the same for both molecules and ions. Since the last issue of this Review did not include the usual section on electrolyte solutions, the coverage has been extended to include work published during 1955; on the other hand, delays in the arrival of journals from Europe and the United States have made it impossible to cover some of the later publica­ tions during 1956. The period under review has not been one of outstanding original ad­ vances, but substantial progress has nevertheless been made, particularly in the fields of ionic solvation and in the conductance of electrolytes in con­ centrated solutions and in nonaqueous and mixed solvents.

Ninth Spiers Memorial Lecture. Some recent experimental studies of diffusion in liquid systems

Ninth Spiers Memorial Lecture. Some recent experimental studies of diffusion in liquid systems