Author

# William T. Humphries

Bio: William T. Humphries is an academic researcher from Stephen F. Austin State University. The author has an hindex of 2, co-authored 2 publications receiving 55 citations.

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33 citations

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25 citations

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TL;DR: In this paper, the coefficients of these short forms for the equations of state have been fitted for the fluids acetone, carbon monoxide, carbonyl sulfide, decane, hydrogen sulfide and fluoromethane.

Abstract: In a preceding project, functional forms for “short” Helmholtz energy equations of state for typical nonpolar and weakly polar fluids and for typical polar fluids were developed using simultaneous optimization. In this work, the coefficients of these short forms for the equations of state have been fitted for the fluids acetone, carbon monoxide, carbonyl sulfide, decane, hydrogen sulfide, 2-methylbutane (isopentane), 2,2-dimethylpropane (neopentane), 2-methylpentane (isohexane), krypton, nitrous oxide, nonane, sulfur dioxide, toluene, xenon, hexafluoroethane (R-116), 1,1-dichloro-1-fluoroethane (R-141b), 1-chloro-1,1-difluoroethane (R-142b), octafluoropropane (R-218), 1,1,1,3,3-pentafluoropropane (R-245fa), and fluoromethane (R-41). The 12 coefficients of the equations of state were fitted to substance specific data sets. The results show that simultaneously optimized functional forms can be applied to other fluids out of the same class of fluids for which they were optimized without significant loss of a...

629 citations

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TL;DR: In this article, the available thermodynamic properties for aqueous solutions of each of the alkali metal sulfates have been combined and analyzed within the framework of the ion interaction model at temperatures up to 225°C.

Abstract: The available thermodynamic properties for aqueous solutions of each of the alkali metal sulfates have been combined and analyzed within the framework of the ion interaction model at temperatures up to 225°C. It was necessary to set α1 equal to 1.4kg1/2-mol−1/2 in order to obtain a satisfactory fit. The temperature dependence of the ion interaction parameters was given the functional form used by Rogers and Pitzer(1) in their study of Na2SO4(aq). With few exceptions, it was possible to reproduce the available thermodynamic data for aqueous solutions of the alkali metal to within the estimated experimental error. Thermodynamic results for Na2SO4(aq) appear to be adequate in this temperature range, but enthalpy and heat capacity data for the other alkali metal sulfate solutions are conspicuously lacking. Activity coefficients of these electrolytes decreased to less than 0.1 at moderate molalities at the higher temperatures, and their order changed with increasing temperature; two results which could be due to a combination of hydration and association effects.

131 citations

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TL;DR: In this paper, a thermodynamic model of the system H(+)-NH₄+)-Na(+))-SO₆µµ-NO₃-Clµ µ-H₂O is parametrized and used to represent activity coefficients, equilibrium partial pressures, and saturation with respect to 26 solid phases.

Abstract: A thermodynamic model of the system H(+)-NH₄(+)-Na(+)-SO₄²⁻-NO₃⁻-Cl⁻-H₂O is parametrized and used to represent activity coefficients, equilibrium partial pressures of H₂O, HNO₃, HCl, H₂SO₄, and NH₃, and saturation with respect to 26 solid phases (NaCl(s), NaCl·2H₂O(s), Na₂SO₄(s), Na₂SO₄·10H₂O(s), NaNO₃·Na₂SO₄·H₂O(s), Na₃H(SO₄)₂(s), NaHSO₄(s), NaHSO₄·H₂O(s), NaNH₄SO₄·2H₂O(s), NaNO₃(s), NH₄Cl(s), NH₄NO₃(s), (NH₄)₂SO₄(s), (NH₄)₃H(SO₄)₂(s), NH₄HSO₄(s), (NH₄)₂SO₄·2NH₄NO₃(s), (NH₄)₂SO₄·3NH₄NO₃(s), H₂SO₄·H₂O(s), H₂SO₄·2H₂O(s), H₂SO₄·3H₂O(s), H₂SO₄·4H₂O(s), H₂SO₄·6.5H₂O(s), HNO₃·H₂O(s), HNO₃·2H₂O(s), HNO₃·3H₂O(s), and HCl·3H₂O(s)). The enthalpy of formation of the complex salts NaNH₄SO₄·2H₂O(s) and Na₂SO₄·NaNO₃·H₂O(s) is calculated. The model is valid for temperatures < or approximately 263.15 up to 330 K and concentrations from infinite dilution to saturation with respect to the solid phases. For H₂SO₄-H₂O solutions the degree of dissociation of the HSO₄⁻ ion is represented near the experimental uncertainty over wide temperature and concentration ranges. The parametrization of the model for the subsystems H(+)-NH₄(+)-NO₃⁻-SO₄²⁻-H₂O and H(+)-NO₃⁻-SO₄²⁻-Cl⁻-H₂O relies on previous studies (Clegg, S. L. et al. J. Phys. Chem. A 1998, 102, 2137-2154; Carslaw, K. S. et al. J. Phys. Chem. 1995, 99, 11557-11574), which are only partly adjusted to new data. For these systems the model is applicable to temperatures below 200 K, dependent upon liquid-phase composition, and for the former system also to supersaturated solutions. Values for the model parameters are determined from literature data for the vapor pressure, osmotic coefficient, emf, degree of dissociation of HSO₄⁻, and the dissociation constant of NH₃ as well as measurements of calorimetric properties of aqueous solutions like enthalpy of dilution, enthalpy of solution, enthalpy of mixing, and heat capacity. The high accuracy of the model is demonstrated by comparisons with experimentally determined mean activity coefficients of HCl in HCl-Na₂SO₄-H₂O solutions, solubility measurements for the quaternary systems H(+)-Na(+)-Cl⁻-SO₄²⁻-H₂O, Na(+)-NH₄(+)-Cl⁻-SO₄²⁻-H₂O, and Na(+)-NH₄(+)-NO₃⁻-SO₄²⁻-H₂O as well as vapor pressure measurements of HNO₃, HCl, H₂SO₄, and NH₃.

126 citations

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TL;DR: In this article, aqueous solutions of KCl, CaCl2, and MgCl2 over the temperature range 382 to 474 K were used as the reference solution and provided the basis for the calculation of osmotic coefficients.

Abstract: Isopiestic studies have been made on aqueous solutions of KCl, CaCl2, and MgCl2 over the temperature range 382 to 474 K. Sodium chloride served as the reference solution and provided the basis for the calculation of osmotic coefficients. The molality range covered in this study correspond to about 1 to 6 mol kg−1 for NaCl. An equation recently developed by Pitzer was fitted to each set of osmotic coefficients with a standard deviation of fit (in the osmotic coefficient) ranging from 0.0009 to 0.0029. Parameters obtained from the fit were used to calculate activity coefficients. The activity coefficients showed a monotonic decrease with increasing temperature and became much less dependent on molality at the higher molalities. Osmotic coefficients of KCl and CaCl2 solutions are consistent (by extrapolation) with existing low-temperature (

77 citations