Slowing Down in Chemical Reactions. The Isobutyric Acid/Water System in the Critical Region

Kaatze, U.; Mirzaev, S. Z.

doi:10.1021/jp0000984

Cited by 20 publications

(14 citation statements)

References 68 publications

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“…where m ¼ 0:664 and D 0 ¼ 5:9 Â 10 À10 m 2 s À1 [41,[48][49][50][51]. The diffusion coefficient equals 1:3 Â 10 À11 m 2 s À1 at 27 C and 2:8 Â 10 À11 m 2 s À1 at 30 C. We could not find in the literature values of the IBA/water diffusion coefficient for temperatures below the critical point.…”

Section: Binary Mixturesmentioning

confidence: 60%

Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes

Stevar

Vorobev

2012

Journal of Colloid and Interface Science

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We report optical observations of the dissolution behaviour of glycerol/water, soybean oil/hexane, and isobutyric acid (IBA)/water binary mixtures within horizontal capillary tubes. Tubes with diameters as small as 0.2mm were initially filled with one component of the binary mixture (solute) and then immersed into a solvent-filled thermostatic bath. Both ends of the tubes were open, and no pressure difference was applied between the ends. In the case of glycerol/water and soybean oil/hexane mixtures, we managed to isolate the dissolution (the interfacial mass transfer) from the hydrodynamic motion. Two phase boundaries moving from the ends into the middle section of the tube with the speeds v∼D(1/3)t(-2/3)d(2) (D,t and d are the coefficient of diffusion, time and the diameter of the tube, respectively) were observed. The boundaries slowly smeared but their smearing occurred considerably slower than their motion. The motion of the phase boundaries cannot be explained by the dependency of the diffusion coefficient on concentration, and should be explained by the effect of barodiffusion. The shapes of the solute/solvent boundaries are defined by the balance between gravity and surface tension effects. The contact line moved together with the bulk interface: no visible solute remained on the walls after the interface passage. Changes in temperature and in the ratio between gravity and capillary forces altered the apparent contact angles. The IBA/water system had different behaviour. Below the critical (consolute) point, no dissolution was observed: IBA and water behaved like two immiscible liquids, with the IBA phase being displaced from the tube by capillary pressure (the spontaneous imbibition process). Above the critical point, two IBA/water interfaces could be identified, however the interfaces did not penetrate much into the tube.

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Section: Binary Mixturesmentioning

confidence: 60%

Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes

Stevar

Vorobev

2012

Journal of Colloid and Interface Science

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“…34,35 The relaxation times associated with the monomer/linear dimer and the linear dimer/ cyclic dimer equilibria of the critical isobutyric acid-water mixture, for example, reveal significant effects of slowing near the critical temperature. 36 For this reasons, special attention has been paid to the complex critical system 2,6-DMP-H 2 O. No uniform picture on the interactions between the local fluctuations in concentration and the stochiometrically defined chemical reactions has been obtained so far.…”

Section: Introductionmentioning

confidence: 99%

Critical behavior of 2,6-dimethylpyridine-water: Measurements of specific heat, dynamic light scattering, and shear viscosity

Mirzaev

Behrends

Heimburg

et al. 2006

The Journal of Chemical Physics

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The specific heat C(p) at constant pressure, the shear viscosity eta(s), and the mutual diffusion coefficient D of the 2,6-dimethylpyridine-water mixture of critical composition have been measured in the homogeneous phase at various temperatures near the lower critical demixing temperature T(c). The amplitude of the fluctuation correlation length xi(0)=(0.198+/-0.004) nm has been derived from a combined evaluation of the eta(s) and D data. This value is in reasonable agreement with the one obtained from the amplitude A(+)=(0.26+/-0.01) J(g K) of the critical term in the specific heat, using the two-scale-factor universality relation. Within the limits of error the relaxation rate Gamma of order parameter fluctuations follows power law with the theoretical universal exponent and with the amplitude Gamma=(25+/-1)x10(9) s(-1). No indications of interferences of the critical fluctuations with other elementary chemical reactions have been found. A noteworthy result is the agreement of the background viscosity eta(b), resulting from the treatment of eta(s) and D data, with the viscosity eta(s)(nu=0) extrapolated from high-frequency viscosity data. The latter have been measured in the frequency range of 5-130 MHz using a novel shear impedance spectrometer.

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“…(1)). Moreover, the diffusion time that can be calculated on the basis of the measured values of the mutual diffusion coefficient of the IBA/water mixture in the supercritical conditions (Chu, 1968;Kaatze, 2000) are not relevant to the studied process. The measured diffusion coefficient is zero in the critical point; above the critical point, the diffusion coefficient grows according to the formula, The dissolution behaviour was essentially different for the under-and super-critical temperatures.…”

Section: Discussionmentioning

confidence: 99%

Dissolution Behaviour of a Binary Mixture in a Capillary Tube

Stevar¹,

Vorobev²

2011

Proceedings

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SUMMARYWe develop a pore-level physical model for the process of miscible displacement through porous media. Using the network model, the current task is reduced to the study of the dissolution dynamics of a binary mixture within a single capillary tube. Tubes of rather small diameters are considered when the typical diffusion and convective time scales are comparable. The test tube filled with the solute is immersed into the solvent-filled thermostatic bath; no pressure difference between the ends of the tubes is applied. Using a high-resolution video-camera, we study the solvent penetration into the test tube. We examine the evolution of the isobutyric acid/water mixture far from and close to the critical (consolute) point (which is 26C for this mixture). The mixture fills the circular glass tubes of diameters 0.4mm-0.8mm and of various lengths. The shape of the interface and its position are tracked and analysed. Based on our observations the following conclusions can be drawn. In all experiments, we observe a front-type propagation of the solvent phase into the tube with a clearly visible interface. The gravity force significantly affects the shape of the interface and the dissolution dynamics in all undertaken experiments. If the mixture temperature is below the critical point, then the uneven one-sided penetration of the solvent into the tube was consistently observed. The solute/solvent interface experiences oscillations of its shape (being either concave or convex at different time moments). If the mixture temperature is above the critical point, then the solvent penetrates evenly from both ends. In both under-and supercritical conditions, the contact line moves with the same speed as the interface, but the apparent contact angle is time-and coordinate-dependent. The rate of the interface propagation varies at different stages of the dissolution process and does not follow the predictions of the diffusion theory.

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Slowing Down in Chemical Reactions. The Isobutyric Acid/Water System in the Critical Region

Cited by 20 publications

References 68 publications

Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes

Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes

Critical behavior of 2,6-dimethylpyridine-water: Measurements of specific heat, dynamic light scattering, and shear viscosity

Dissolution Behaviour of a Binary Mixture in a Capillary Tube

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