Electrical resistance of the system isobutyric acid-water near the critical point

Stein, Arnold; Allen, Guy F.

doi:10.1063/1.1679973

Cited by 54 publications

(16 citation statements)

References 21 publications

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“…Water was distilled once from a glass system. The binary solvent mixture was prepared at the critical composition of 0.388 mass fraction isobutyric acid [13] by weighing. Both Fe 2 O 3 and Co 3 O 4 were obtained from Fisher and used as received.…”

Section: Methodsmentioning

confidence: 99%

Chemical Equilibrium and Critical Phenomena: The Solubilities of Iron(III) Oxide and Cobalt(II,III) Oxide in Isobutyric Acid + Water Near the Consolute Point

Baird

2009

Int J Thermophys

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The solubilities of iron(III) oxide, formula Fe 2 O 3 , and cobalt(II,III) oxide, formula Co 3 O 4 , have been determined in the liquid mixture, isobutyric acid + water, along the critical isopleth at temperatures above the upper critical solution temperature near 299 K. When plotted in van't Hoff form with ln s versus 1/T , the measurements of solubility, s, lie on a straight line for values of the temperature, T , in kelvin, which are sufficiently in excess of the critical solution temperature, T c . The sign of the slope, (∂ ln s/∂(1/T )), indicates that in the case of both oxides, the dissolution reaction is endothermic. When the temperature is within 1 K of T c , however, the slope departs from its constant value and appears to diverge toward negative infinity. The principle of critical-point universality predicts that a divergence in (∂ ln s/∂(1/T )) is to be expected for T near T c in those cases where the stoichiometry of the dissolution reaction involves both components of the solvent; moreover, the Gibbs-Helmholtz equation predicts that, if the heat of solution is endothermic, the sign of the divergence should be negative. Both of these predictions are confirmed by the solubilities of Fe 2 O 3 and Co 3 O 4 measured as a function of temperature along the critical isopleth of isobutyric acid + water.

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Section: Methodsmentioning

confidence: 99%

Chemical Equilibrium and Critical Phenomena: The Solubilities of Iron(III) Oxide and Cobalt(II,III) Oxide in Isobutyric Acid + Water Near the Consolute Point

Baird

2009

Int J Thermophys

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“…(15) and (21) (15) and (21) for g = 0.11 and g = 0.793, respectively. (21) 0.77 ± 0.01 28 ± 3 0 . 6 4 g = 0.793, fitting with Eq.…”

Section: Discussionmentioning

confidence: 98%

“…6 4 g = 0.793, fitting with Eq. (21) 0.62 ± 0.04 0.93 ± 0.15 0.84 parameters in Eqs. (15) and (21), and the goodness of fits χ 2 are listed in Table II.…”

Section: Discussionmentioning

confidence: 99%

“…A number of explanations for the critical anomaly in the conductivity of acidwater systems such as isobutyric acid + water and phenol + water were summarized by Greer. 18 The dynamic explanations included the viscosity drag: σ ∼ 1/η ∼ τ vz η = τ 0.041 , 21 the temperature dependence on the nearest-neighbor correlation function: σ ∼ τ 1−α = τ 0.89 , 22 and a percolation model for conductivity: σ ∼ τ 2β = τ 0.65 ; 23 where σ and η are the conductivity and viscosity; α = 0.11, β = 0.326, ν = 0.63, and z η = 0.065 are the critical exponents corresponding to the heat capacity, the coexistence curve, the correlation length and the viscosity, respectively; τ = | T −T c T c | is the reduced temperature with T c being the critical temperature. The thermodynamic explanations attributed the slowing down to the anomaly of the extent of the acid dissociation, which was believed to be dependent on the number of density variables kept constant and resulted in two contradictory singularities: σ ∼ τ 1/δ = τ 0.207 with δ being the critical exponent corresponding to the critical isotherm, when it was thought that only field variables rather than densities were held constant; 16 σ ∼ τ 1−α = τ 0.89 when the total mole fraction of isobutyric acid was considered to be a density and held constant.…”

Section: Introductionmentioning

confidence: 99%

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Critical anomalies of alkaline fading of phenolphthalein in the critical solution of 2-butoxyethanol + water

Yin

Hao

et al. 2013

The Journal of Chemical Physics

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We have used three-wavelength UV-spectrophotometry to study the reaction of the alkaline fading of phenolphthalein in the critical solution of 2-butoxyethanol + water. It was found that when the temperature was far away from the critical point, the values of the natural logarithm of the rate constant k and the natural logarithm of the chemical equilibrium K determined in our experiments had good linear relationships with the reciprocal of temperature, which served as the backgrounds and were used for correcting k and K in the critical region. The critical slowing down of the reaction and the critical anomaly of the chemical equilibrium were detected near the critical point. The value of the critical exponent characterizing the slowing down effect of the reaction rate was obtained to be 0.156, which was close to the value 0.11 associated with the heat capacity divergence and agreed with the theoretical prediction. The experimental result also confirmed the theoretical prediction of 0.11 for the critical exponent characterizing the weak divergence of the singularity of the chemical equilibrium.

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“…The conductivity has been studied in the past in aqueous and poorly conductive nonaqueous critical solutions, as well as in ion-doped solutions [9][10][11][12][13][14][15]. The critical exponent u of the conductivity anomaly is found experimentally between 2b and ͑1 2 a͒ [9-14], where b 0.326 and a 0.109 are the usual 3D Ising-like exponents [16].…”

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Evidence of a Critical Anomaly of the Electrical Conductivity in Highly Concentrated Nonaqueous Ionic Mixtures

Oleinikova

Bonetti

1999

Phys. Rev. Lett.

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We present the first electrical conductivity measurements performed in highly concentrated electrolyte solutions near a critical consolute point. The critical binary mixtures studied are tetra-n-butylammonium picrate in 1-dodecanol and 1,4-butanediol solvents. An accurate determination of the regular conductivity in the one-phase region indicates the presence of a critical anomaly in the electrical conductivity for t , 10 22 , where t is the reduced temperature. The nature of the anomaly does not correlate with the values of the viscosity, the dielectric constant, or the free ion concentration of the mixtures. PACS numbers: 66.10.Ed, 05.70.Jk, 64.70.Ja At present, a theory that describes the critical behavior of highly concentrated electrolyte solutions and molten salts is not yet available [1]. The mechanism of corrosion in supercritical water is a subject of growing scientific interest due to new technological applications such as the oxidation of organic wastes [2]. At high temperature and pressure, supercritical water becomes self-ionized and behaves quite like a highly conducting medium, resembling molten salts [3]. Highly concentrated binary ionic mixtures, made of an organic salt in a low dielectric-constant organic solvent with an upper critical consolute point near room temperature, have been recently investigated [4][5][6][7][8]. These systems belong mostly to the 3D Ising universality class, possibly with some weak crossover from Ising-like to mean-field criticality [Ref. [4(b)]]. The transport properties in such systems have not been studied yet, except for the shear viscosity that shows a weak anomaly similar to that observed in pure fluids or in neutral binary mixtures [8].This Letter presents the first electrical conductivity measurements in highly concentrated nonaqueous electrolytes near a critical consolute point. The conductivity has been studied in the past in aqueous and poorly conductive nonaqueous critical solutions, as well as in ion-doped solutions [9][10][11][12][13][14][15]. The critical exponent u of the conductivity anomaly is found experimentally between 2b and ͑1 2 a͒ [9-14], where b 0.326 and a 0.109 are the usual 3D Ising-like exponents [16]. A u ͑1 2 a͒ exponent should be attributed to short-range fluctuations [17] or should be found in a proton hopping mechanism [13]. A percolation model for the transport of the ions would yield u 2b [10,11]. Scattering of ionic impurities by concentration fluctuations should give a n 0.630 singularity [9].We have measured the electrical conductivity of the salt tetra-n-butylammonium picrate (TBAP) in two different solvents: 1-dodecanol (DD) (static dielectric constant´ 4.6 at T 61 ± C) and 1,4-butanediol (BD) (´ 25.9 at T 59 ± C). Mixtures of TBAP in solvents with composition (92.5% DD 1 7.5% BD) and (85% DD 1 15% BD) have been also studied. The coexistence curve of these binary mixtures is described by the 3D Ising b exponent with almost no crossover to mean field [7].The low-frequency electrical impedance was measured between two parallel ...

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Electrical resistance of the system isobutyric acid-water near the critical point

Cited by 54 publications

References 21 publications

Chemical Equilibrium and Critical Phenomena: The Solubilities of Iron(III) Oxide and Cobalt(II,III) Oxide in Isobutyric Acid + Water Near the Consolute Point

Chemical Equilibrium and Critical Phenomena: The Solubilities of Iron(III) Oxide and Cobalt(II,III) Oxide in Isobutyric Acid + Water Near the Consolute Point

Critical anomalies of alkaline fading of phenolphthalein in the critical solution of 2-butoxyethanol + water

Evidence of a Critical Anomaly of the Electrical Conductivity in Highly Concentrated Nonaqueous Ionic Mixtures

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