Cluster diffusion in liquids

Cussler, E. L.

doi:10.1002/aic.690260108

Cited by 90 publications

(79 citation statements)

References 34 publications

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“…1). This means that there is a stable/metastable cloud point boundary where the solutions either liquid-liquid [23] or liquid-crystal phase separate. A third line is found in the colloidal range, the monomodal-bimodal line (T S £ 30 C).…”

Section: Vanillin In Aqueous 20 % 2-propanolmentioning

confidence: 98%

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Cluster Formation in Precrystalline Solutions

Sorensen¹,

Sontum²,

Samseth

et al. 2003

Chem Eng & Technol

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Small Angle Neutron Scattering (SANS) gives evidence of colloidal structures or clusters in solutions of vanillin in aqueous alcohol. Interpretation of the data gives the same result as the Photon Correlation Spectroscopy technique: stable or metastable fractal clusters. The size of these clusters increases as a function of the parameters that control supersaturation, but is stable with respect to time. These structures, called metastable clusters, are closely related to the observed liquid-liquid phase separation at high solute concentration. Another type of clusters is found to co-exist with the metastable clusters at a lower solute concentration. The same type of structures is found in a two-component system of vanillin in 2-methyl-2-butanol. They slowly grow as a function of time, and are called labile clusters. These colloidal structures are assumed to be precrystalline clusters giving rise to nuclei in crystallization.

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Section: Vanillin In Aqueous 20 % 2-propanolmentioning

confidence: 98%

“…Cussler [23] derived a relation for the diffusivity in concentrated solutions containing molecular isotropic, homogenous, and non-interacting clusters. This relation can be extended to include fractal structures.…”

Section: Metastable Clustersmentioning

confidence: 99%

Cluster Formation in Precrystalline Solutions

Sorensen¹,

Sontum²,

Samseth

et al. 2003

Chem Eng & Technol

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“…Attempts have been made to explain this phenomenon on thermodynamic grounds (Turner, 1975a,b) and by postulating the failure of Fick's law near the consolute point (Anisimov and Perelman, 1968). Cussler (1980) explained this behavior by assuming that concentration fluctuations, including both single molecules and clusters of molecules, dominate behavior near the consolute point.…”

Section: Introductionmentioning

confidence: 98%

The diffusivity of potassium chloride and sodium chloride in concentrated, saturated, and supersaturated aqueous solutions

Chang

Myerson

1985

AIChE Journal

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The diffusion coefficients of potassium chloride and sodium chloride were measured in concentrated, saturated, and supersaturated solutions at 25°C employing Gouy interferometry. The results indicate a maximum in the diffusivity vs. concentration curve near saturation followed by a rapid decline in diffusivity toward zero with increasing concentration in the supersaturated region. This behavior supports the idea that the diffusion coefficient approaches zero at the spinodal concentration. The data were successfully correlated by modifying an empirical activity coefficient equation (Robinson and Stokes, 1955) to account for molecular cluster effects and employing the calculated activity coefficients along with a predictive equation for diffusivity in electrolytes (Robinson and Stokes, 1955 SCOPEThe study of diffusion coefficients in supersaturated solutions is of fundamental importance in understanding the mechanisms of diffusion and of crystal growth from solution. Virtually no data of this kind exist, however, resulting in the use of values obtained through the extrapolation of undersaturated diffusivity data into the supersaturated range. Sorell and Myerson (1982) demonstrated that diffusion coefficients obtained through extrapolation could be seriously in error. They measured the diffusivity of urea in supersaturated aqueous solutions and compared the results with those obtained through extrapolation of existing data. The experimental results showed a very rapid decline in the diffusion coefficient with increasing concentration in the supersaturated region. Differences of up to several hundred percent between the experimental and extrapolated data were reported. The purpose of this study is to: (1) experimentally measure diffusion coefficients in the electrolyte systems potassium chloride-water and sodium chloride-water at concentrations in the supersaturated region; (2) correlate the diffusion data through modification of existing relations for concentrationdependent diffusion in electrolytes; and (3) determine whether the rapid decline in diffusivity with increasing concentration in the supersaturated region observed in the urea-water system is observed in other systems. CONCLUSIONS AND SIGNIFICANCEThe diffusion coefficients of potassium chloride in water at 25°C were measured at concentrations ranging from 0.7-4.23 M. Experimental results in the undersaturated region were consistent to within f 3 % of those of Costing (1950). Results show a maximum in the diffusivity vs. concentration curve near saturation (4.09 M) followed by a rapid decline in the diffusivity with increasing concentration in the supersaturated region,The diffusion coefficients of sodium chloride in water at 25°C were measured at concentrations ranging from 0.1-5.46 M. Experimental results in the supersaturated region were consistent to within f 3 % of those reported by Rand and Miller (1979). A maximum in diffusivity in the region of saturation followed by a rapid drop of diffusivity with increasing concentration was also observed.It is ...

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“…The concentration gradient developed as a result of the density difference between the clusters and the solution [2]. Cussler observed different rates between cluster diffusion and molecular diffusion in many binary systems, which supported the cluster assumption [3]. Myerson and co-workers observed the decrease in the diffusivities of urea, glycine solutions, which provided evidence for molecular aggregation [4].…”

Section: Introductionmentioning

confidence: 60%

Pyranine Fluorescence Quenching for the Characterization of Solutions

Wang¹,

Berglund²

2016

AJAC

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Fluorescence quenching of pyranine by tryptophan, phenylalanine, and nicotinic acid was investigated by using steady state and time resolved fluorescence spectroscopy. On a comparative basis, nicotinic acid is a very strong quencher of pyranine fluorescence, tryptophan is a moderate quencher and phenylalanine is a weak quencher. The strong quenching is the result of the hydrogen bonding complex between pyranine and amine which existed in both tryptophan and nicotinic acid. Contact complex will form between phenylalanine and pyranine which is the reason of quenching of pyranine by phenylalanine. Associates will form in tryptophan and phenylalanine due to the zwitterion + H 3 NRCOO − or/and hydrogen bond. Higher concentrations favor the formation of aggregates in the supersaturated solution which made the quenching curve different from unsaturated solution dramatically.

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Cluster diffusion in liquids

Cited by 90 publications

References 34 publications

Cluster Formation in Precrystalline Solutions

Cluster Formation in Precrystalline Solutions

The diffusivity of potassium chloride and sodium chloride in concentrated, saturated, and supersaturated aqueous solutions

Pyranine Fluorescence Quenching for the Characterization of Solutions

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