Are Ionic Stokes Radii of Any Use?

Marcus, Yizhak

doi:10.1007/s10953-012-9922-4

Cited by 31 publications

(21 citation statements)

References 30 publications

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“…Estimates of the sizes of hydrated individual ions at finite concentrations, as Stokes radii, could eventually be made from conductivity plus transference and from diffusion data, but there are pitfalls also along this way. 55…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, also, there is no point in deriving effective ionic diameters or volumes for the individual ions at such concentrations from experimental thermodynamic data. Estimates of the sizes of hydrated individual ions at finite concentrations, as Stokes radii, could eventually be made from conductivity plus transference and from diffusion data, but there are pitfalls also along this way …”

Section: Discussionmentioning

confidence: 99%

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Concentration Dependence of Ionic Hydration Numbers

Marcus

2014

J. Phys. Chem. B

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Isothermal compressibility data of 23 aqueous electrolyte solutions at 25 °C from the literature are used to calculate their hydration numbers, which diminish as the concentration increases. Their limit at very high concentration is near the "number of adsorption sites" of water molecules on the ions, obtained by the BET method. On the contrary, hydration numbers obtained from ultrasound speed measurements yielding isentropic compressibilities cannot be valid, being much too large at infinite dilution.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Concentration Dependence of Ionic Hydration Numbers

Marcus

2014

J. Phys. Chem. B

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“…In our view, this interpretation is problematic, since the Stern layer thickness should be rather given by the ionic radius, and Stokes ion diameter does not represent the actual size of the ions, which can be measured more reliably by X-ray diffraction, neutron scattering, or X-ray absorption fine structure (XAFS) [64][65][66]. The deviations mainly occur due to neglect of dielectric friction and failure of the Stokes law at the molecular level [67,68]. Brown et al [19] have further argued that the increase of the Stern capacitance with increasing salt concentration is caused by a decrease of the Stern layer thickness due to an increasing osmotic pressure of the electrolyte solution.…”

Section: Colloids Interfaces 2018 2 X For Peer Reviewmentioning

confidence: 99%

Measuring Inner Layer Capacitance with the Colloidal Probe Technique

Smith

Maroni

Borkovec

et al. 2018

Colloids and Interfaces

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The colloidal probe technique was used to measure the inner layer capacitance of an electrical double layer. In particular, the forces were measured between silica surfaces and sulfate latex surfaces in solutions of monovalent salts of different alkali metals. The force profiles were interpreted with Poisson-Boltzmann theory with charge regulation, whereby the diffuse layer potential and the regulation properties of the interface were obtained. While the diffuse layer potential was measured in this fashion in the past, we are able to extract the regulation properties of the inner layer, in particular, its capacitance. We find systematic trends with the type of alkali metal ion and the salt concentration. The observed trends could be caused by difference in ion hydration, variation of the binding capacitance, and changes of the effective dielectric constant within the Stern layer. Our results are in agreement with recent experiments involving the water-silica interface based on a completely independent method using X-ray photoelectron spectroscopy in a liquid microjet. This agreement confirms the validity of our approach, which further provides a means to probe other types of interfaces than silica.

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“…However, ions with medium dimensions and low charge densities (classified as negatively solvated ones) did not fit the concept of "Stokes" radii. Those ions caused a lot of inconveniences and stimulated the disappointment of researchers [2,16,19]. Quite often, such cases re-mained without attention.…”

Section: Discussion Of the Resultsmentioning

confidence: 99%