Physical Methods of Organic Chemistry

Weißberger, A.

doi:10.1097/00010694-195008000-00025

Cited by 91 publications

(33 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The techniques, theory, and data analysis involved in determination of binary diffusion coefficients from this instrument have been described in the literature (Gosting et al, 1949;Weissberger, 1972;Cussler, 1976;Tyrrell and Harris, 1984). Several improvements over traditional instruments were incorporated in the construction of tile Gouy diffusiometer used in this work.…”

Section: Methodsmentioning

confidence: 99%

The mutual diffusion coefficient of methanol–n‐hexane near the consolute point

Clark¹,

Rowley²

1986

AIChE Journal

View full text Add to dashboard Cite

The composition and temperature dependence of the mutual diffusion coefficient near the liquid-liquid critical point of methanol-n-hexane mixtures has been determined by Gouy interferometry. The critical exponent was found to be 0.685. Constant-temperature extrapolation to zero diff usivity located the spinodal curve. Spinodal loci calculated from the NRTL model are inconsistent with the experimentally determined values. W. M. Clark and R. L. Rowley Department of Chemical EngineeringRice University Houston, TX 7725 1 SCOPEMutual diffusion coefficients can be separated into two parts: a mobility or Onsager term and a thermodynamic factor. The mathematical criterion, which defines the spinodal curve and demarcates the unstable region interior to the equilibrium coexistence curve, can be expressed as the loci of points where the thermodynamic factor is identically zero. Classical and light-scattering experiments have shown that the diffusion coefficient goes to zero as the temperature approaches the liquid-liquid critical point at constant critical composition. Although Skripov et al. (1980) concluded that the diffusion coefficient for the methanoln-hexane system vanished at the same rate as the thermodynamic factor, indicating a finite Onsager term, it has been fairly well established by studies on other systems that the Onsager coefficient actually diverges as the critical point is approached. One purpose of this study was to determine the critical exponent in the methanol-n-hexane system by a series of temperaturejump-initiated diffusion experiments in a Gouy interferometer. The diffusion critical exponent has significant implications in terms of universality and scaling theories.The second purpose was to use diffusion coefficient measurements to determine the spinodal curve. Since the diffusion coefficient must be zero at the spinodal, extrapolation of measured diffusivities to zero could be used to determine its location. No methods have heretofore been able to provide spinodal information in liquid-liquid phase-splitting systems. Classical equilibrium studies provide only coexistence information. Nevertheless, the location of the spinodal curve could be extremely valuable in developing and testing liquid mixture models for the Gibbs free energy since it is related to the second derivative with respect to composition, as shown in Eq. 7. Generally, liquid-mixture model parameters are fitted from the solubility or equilibrium concentration information. No other data have been available to test the model at other compositions at the same temperature. The spinodal criterion on the other hand provides additional restrictions that a satisfactory and consistent liquid-mixture model must satisfy. CONCLUSIONS AND SIGNIFICANCEDiffusion coefficients were measured in methanol-nhexane mixtures as a function of temperature along the critical composition in a temperature-jump cell using a Gouy interferometer. The critical exponent was found to be 0.685, in good agreement with previous studies on other systems, indicating that...

show abstract

Section: Methodsmentioning

confidence: 99%

The mutual diffusion coefficient of methanol–n‐hexane near the consolute point

Clark¹,

Rowley²

1986

AIChE Journal

View full text Add to dashboard Cite

show abstract

“…1 as a immersion data in Table I and a knowledge of hL using equation [I]. T h e dipole moments are those of Smyth (7). If it is assumed that the differences in the total adsorption energy arise primarily from E,, then, according to equation [7], the slope of the line in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…T h e dipole moments are those of Smyth (7). If it is assumed that the differences in the total adsorption energy arise primarily from E,, then, according to equation [7], the slope of the line in Fig. 1 is a measure of the average electrostatic field strength of the rutile surface immersed in the liquids.…”

Section: Resultsmentioning

confidence: 99%

“…The values of E, for the Graphon systems were taken to be equal to the net adsorption energy N , (EA4 -E L ) and were not calculated because of both the approximate nature of the equation and the lack of reliable values for the physical constants of the surface atoms. ' The values of E, and E , for alcol~ol on rutile were directly calculable from equations [ 5 ] and [7] respectively from the ltnowledge of the field strength. The polarizabilities of the OH ancl CH2 groups were calculated from molar refraction data.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Interaction Energies of Organic Molecules With Rutile and Graphon Surfaces From Heats of Immersion

Chessick¹,

Zettlemoyer²,

Healey³

et al. 1955

Can. J. Chem.

View full text Add to dashboard Cite

The heats of immersion of rutile in a series of short chain organic liquids are found experimentally to be an approximate linear function of the dipole moment of the wetting liquid. The significance of the relation is discussed in terms of the polar van der Waals force contribution which is primarily dependeut on dipole moment. The average distance of approach of a dipole to the rutile surface and the effective surface force held extending from the rutile surface are calculated.The net adsorption energy, which is calculated directly from heat of immersion data, is related t o the energy contributions resulting from the various polar and nonpolar van der Waals forces active in the adsorption process: These energy contributions which make up the total adsorption energy are calculated for the interaction of an alcohol and a hydrocarbon with both a heteropolar (rutile) and a homopolar (Graphon) surface. On the basis of the results obtained, the effects of chain length and functionality of the liquids on the heat of immersion are discussed.

show abstract

“…The molecular refraction increments for the CH 2 groups, obtained by comparing closest homologues, rise from 4.65 to 4.72. For n-paraffins the increments for the CH 2 group differ from, an average value of 4.64 (for the D line of sodium) by only a few hundredths of a cm 3 except for the first few members of the series (51,52). The increasing atomic and bond refractivities resulting from the increasing alkylation must be due either to an increasing atomic refractivity or to some other factor which increases the molecular refraction.…”

Section: Molecular Atomic and Bond Refractionmentioning

confidence: 87%