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  • 1
    Electronic Resource
    Electronic Resource
    Adsorption on hydrophobic porous glass near the liquid/liquid coexistence curve of a binary liquid mixture (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 732-737 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A differential refractometric method is used to study the temperature and composition dependence of the adsorptive properties of porous glass in 2-butoxyethanol (abbreviated C4E1)/water mixtures. The surface of the adsorbent carries hydrophobic -SiO-C8H17 as well as hydrophilic -SiOH groups. The experiments are carried out close to the liquid/liquid coexistence curve in the vicinity of the lower critical point of the system. Depending on the temperature and composition of the mixtures either C4E1 or water is preferentially adsorbed. There exists a line along which the net adsorption vanishes. For compositions x〉xc (x, mole fraction of C4E1; xc, critical composition) the amount of substance of adsorbed water ñ ws(Tp) per unit gram of adsorbent at temperature Tp increases with increasing values of the temperature difference (Tp−Tc) in the range 0 K〈(Tp−Tc)〈4 K. Tp is the temperature of phase separation of the bulk mixture in the presence of the adsorbent. Beginning at temperatures (Tp−Tc)〉4 K the adsorbed amount of substance ñ ws(Tp) decreases. At (Tp−Tc)〉8 K it reaches a value which is smaller by a factor of about 10 compared with its maximum value. This phenomenon is reminiscent of a wetting transition. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473409
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  • 2
    Electronic Resource
    Electronic Resource
    Diffusivity in a non-ionic surfactant/water mixture of critical composition (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 414-418 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of measurements of the temperature dependence of the mutual diffusion coefficient D of a tetraethyleneglycoloctylether (abbreviated C8E4) /water mixture of critical composition are reported (lower critical point, visually determined critical temperature Tc(vis)=40.587 °C; critical composition, mass fraction yc(C8E4)=0.071). The critical micelle concentration of C8E4 is smaller than the critical concentration, so that micelles are expected to be present in the mixture of critical composition. The reduced diffusion coefficients D*(=6πηξ/(kBT)⋅D) calculated from static and dynamic light scattering and viscosity data scale when plotted as function of the scaling variable x (=qξ) (η, shear viscosity; ξ, correlation length; D, diffusion coefficient; q, absolute value of scattering vector; kB, Boltzmann constant; T, temperature). They can be represented by the approximant of the dynamic scaling function proposed by Burstyn et al. [Phys. Rev. A 28, 1567 (1983)] assuming that the measured diffusion coefficient can be identified with the singular contribution (i.e., D=Dc). The influence of micelles on the critical properties of the system does not show up in the D* versus x plot. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469417
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  • 3
    Electronic Resource
    Electronic Resource
    Diffusivity in 2-butoxyethanol/water mixtures of noncritical composition approaching the liquid/liquid coexistence curve (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 476-479 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of dynamic light scattering experiments are reported which demonstrate that the mutual diffusion coefficient of 2-butoxyethanol/water mixtures of noncritical composition exhibits a characteristic temperature and composition dependence: The diffusion coefficients of the two phases of noncritical composition coexisting along the liquid/liquid coexistence curve decrease by an order of magnitude in the temperature range (Tp−Tc)〈10 K approaching the lower critical point (Tp, temperature of phase separation; Tc, critical temperature). In the homogeneous 1-fluid phase region of the phase diagram, the D vs (T−Tp) curves of mixtures of noncritical composition are shifted to smaller values of D with decreasing values of ||y−yc|| (y, mass fraction of 2-butoxyethanol; yc, critical mass fraction). These findings are discussed on the basis of the model of regular mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468158
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  • 4
    Electronic Resource
    Electronic Resource
    Osmotic properties of polyelectrolyte membranes: positive and negative osmosis (1993)
    s.l. : American Chemical Society
    Langmuir 9 (1993), S. 1370-1377 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00029a034
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  • 5
    Electronic Resource
    Electronic Resource
    Deuterium isotope effects in binary critical mixtures (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2922-2928 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The shape of the liquid–liquid coexistence curve of five binary liquid mixtures containing methanol (methanol, methanol-d1, methanol-d4) and cyclohexane (cyclohexane, cyclohexane-d12) is studied using a differential refractometer. It is found that all systems have approximately the same critical composition (mole fraction) and approximately the same shape of the coexistence curve in the vicinity of the critical point. However, the critical temperature changes in a characteristic manner. Replacement of hydrogen atoms involved in hydrogen bonding by deuterium leads to an increase of the critical temperature of about 1.2 K for each replaced hydrogen atom. Replacement of hydrogen atoms not involved in hydrogen bonding leads to a decrease of the critical temperature of about 0.3 K for each replaced hydrogen atom. These are average values referring to the systems methanol/cyclohexane, phenol-d6/D2O, deutero-isobutyric acid (COOH)/H2O, and deutero-isobutyric acid (COOD)/D2O. Substitution of H2O by D2O in the four component system benzene, ethanol, water, ammonium sulfate of near tricritical composition increases a characteristic temperature by about 1 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451001
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  • 6
    Electronic Resource
    Electronic Resource
    Estimation of liquid/liquid interfacial tensions of metallic mixtures using two-scale-factor universality (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7655-7656 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The two-scale-factor universality hypothesis of critical phenomena is used to estimate the liquid/liquid interfacial tension near the critical point of binary alloys with miscibility gap. Experimental results of measurements of the correlation length of local concentration fluctuations (data for the systems cadmium/gallium and sodium/lithium taken from the literature), and experimental results of measurements of the temperature dependence of the molar heat capacity at constant pressure (data for the system bismuth/gallium taken from the literature) are used for this illustration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464681
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  • 7
    Electronic Resource
    Electronic Resource
    Gravity and shear flow effects on spinodal decomposition in single component fluids (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 758-759 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of experiments, carried out in space and on earth, are reported in which spinodal decomposition in a single-component fluid (SF6) is studied by small angle light scattering. Deformed circular light-scattering patterns are observed. They reflect deformation of density fluctuations by gravity effects and shear flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465753
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  • 8
    Electronic Resource
    Electronic Resource
    Critical slowing down of nuclear growth along the liquid/liquid coexistence curve (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 859-861 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The growth rate of a second liquid phase is studied in demixing process of n-butoxyethanol/water mixtures. Following the liquid/liquid coexistence curve from far-off critical compositions to the critical point, the growth rate of the droplets slows down markedly. The values of the mutual diffusion coefficient D extracted from the growth rate data are found to scale approximately with a power law of the form D ∼|| (T − Tc)/Tc||0.79.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462419
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  • 9
    Electronic Resource
    Electronic Resource
    A search for the wetting transition in 2,6-dimethyl pyridine/water mixtures in contact with glass near the lower critical point (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7757-7760 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The pendant drop method and the capillary rise method are used to measure the interfacial tension σ of 2,6-dimethyl pyridine(2,6-lutidine)/water mixtures near the lower critical point. It is found that at temperatures 0.2 K≤(T−Tc)≤1.5 K the temperature dependence of σ is represented by a power law of the form σ=σ0 tμ (t=(T−Tc)/Tc) with μ=(1.25±0.01) and σ0=(32.4±0.6) mN m−1. The value of μ is consistent with the theoretically expected universal value of μ=1.26. At large temperature differences σ increases slower than expected by the power law. The values of the amplitude ratios Rσ,ξ+[=σ0(ξ0+)2/(kBTc)] and Rσ,A+[=(Av,0/kB)2/3(kBTc/σ0)] calculated from the experimental data [correlation length of local concentration fluctuations, ξ0+=(0.230±0.009) nm] and Av,0 (heat capacity per unit volume at constant pressure; Av,0=1.81 J cm−3 K−1) are consistent with accepted values. This indicates that the interfacial tension measurements are free from large systematic errors. The value of a2 (a, capillary constant) determined with the pendant drop method as well as with the capillary rise method agree with each other within the uncertainty of the measurements in a temperature range (T−Tc)≤7 K. The capillary rise data is analyzed by assuming that the contact angle θ of the lower water rich phase at the capillary wall is zero (θ=0). The data follows the same curve as that obtained with the pendant drop method in a temperature range (T−Tc)≤25 K. From these findings it is concluded that the water rich (lower) phase wets the wall of the glass capillary completely at least up to temperature differences (T−Tc)≤7 K. A wetting transition cannot be detected in that temperature range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463494
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetics of liquid–liquid phase separation in a binary mixture with miscibility gap: Study of noncritical mixtures of 2,6-dimethyl pyridine/water near the lower critical point (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4349-4356 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Temperature jump experiments with a characteristic heating time of 0.5 ms are used to study the kinetics of liquid/liquid phase separation in noncritical mixtures of 2,6-dimethyl pyridine and water (||x-xc||〉0.02; x, mole fraction of 2,6-dimethyl pyridine; xc, critical composition) as functions of composition and supersaturation. The response of the system to a temperature jump is monitored by measuring the intensity of light scattered by the sample at different scattering angles aitch-theta (30°〈aitch-theta〈90°) as a function of time (up to several seconds). Starting from a level of constant intensity reached with a time constant in the range of milliseconds after a temperature jump the scattered intensity increases with time. For small supersaturations consecutive maxima and minima of scattered intensity develop.They reflect diffusion limited growth of droplets of the emerging second liquid phase (linear relationship between the square of the radius of growing droplets and time). The growth rate increases with increasing supersaturation. Practically no nucleation barrier is found for the onset of growth of droplets for small supersaturations and compositions (||x−xc||〉0.03). The number density N of growing droplets is obtained from simultaneous measurements of scattered intensity and turbidity. For small supersaturations N is independent of time but changes with supersaturation in a characteristic way (classical nucleation model). There exists an upper limit of overheating δT* above which the number density N increases drastically. The ratio (δT*/ΔTc,p) is independent of the reduced temperature ε˜ of phase separation (ε˜=ΔTc,p/Tc; ΔTc,p=Tc−Tp; Tc, critical temperature, Tp, temperature of phase separation). This is expected for mixtures of noncritical composition. The theory proposed by Langer and Schwartz to treat nucleation and growth of droplets in metastable near critical fluids does not describe the phenomena observed in this study. The composition of the samples used (||x−xc||〉0.02) appears to be too far away from the critical.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458718
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