Isopiestic determination of the osmotic and activity coefficients of {zH2SO4 + (1 - Z)MgSO4} (aq) at T = 298.15 K. II. Results for z = (0.43040, 0.28758, and 0.14399) and analysis with Pitzer's model

Rard, Joseph A. and Clegg, Simon L. (1999) Isopiestic determination of the osmotic and activity coefficients of {zH2SO4 + (1 - Z)MgSO4} (aq) at T = 298.15 K. II. Results for z = (0.43040, 0.28758, and 0.14399) and analysis with Pitzer's model. Journal of Chemical Thermodynamics, 31 (3). pp. 399-429. ISSN 0021-9614

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Abstract

Isopiestic vapor pressure measurements were made for {zH2SO4 + (1 - z)MgSO4}(aq) solutions with H2SO4 molality fractions of z = (0.43040, 0.28758, and 0.14399) at the temperature 298.15 K. Measurements extend from total molalities of mT = (0.29999, 0.32948, and 0.36485) mol·kg-1 to mT = (4.84740, 4.28433, and 3.96206)mol·kg-1, respectively. These highest molalities correspond to the greatest degrees of supersaturation that could be achieved during isothermal removal of solvent. The corresponding water activity ranges are 0.9924 ≥ aw ≥ 0.7469, 0.9924 ≥ aw ≥ 0.7983, and 0.9924 ≥ aw ≥ 0.8291 for z = (0.43040, 0.28758, and 0.14399), respectively. Isopiestic results for this system with z = (0.85811, 0.71539, and 0.57353) were reported previously (J. Chem. Thermodynamics 1997, 29, 533-555). The combined results to mT ≤ 3.5 mol·kg-1 are represented essentially to experimental accuracy with Pitzer's model, using ionic strength-dependent third virial coefficients for the constituent binary solutions. A second set of parameters is also presented for the more extended molality range of mT ≤ 6.0 mol·kg-1, where this model gives a slightly less accurate representation of the experimental information. The nature and extent of ionic association in MgSO4(aq) is discussed, but it was not possible to select a value of the association constant owing to large discrepancies among the various studies.

Item Type: Article
Additional Information: Funding Information: The work of J.A.R. was supported under the auspices of the Office of Basic Energy Sciences (Geosciences) of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48, and that of S.L.C. by an Advanced Research Fellowship (GT/93/AAPS/2) from the Natural Environmental Research Council of the U.K. J.A.R. thanks Dr Leland W. Younker for additional support to retain the laboratory during 1996, Dr Donald G. Archer for supplying us with copies of his computer program for the thermodynamic properties of NaCl(aq), Dr Donald G. Miller for preparing preliminary versions of two of the plots, Professor Y. Awakura for supplying us with additional experimental information, and Mike Sharp, Bea Armstrong, Randall K. Weese, and Theresa Duewer for the spectroscopic impurity analyses. J.A.R. wishes to express his gratitude to Drs William C. Luth and George A. Kolstad, both former managers of the Geosciences Research Program of the Office of Basic Energy Sciences. Their support allowed him to perform a very extensive series of detailed isopiestic measurements for numerous aqueous binary and ternary electrolyte systems with geochemical and environmental applications.
Uncontrolled Keywords: aqueous solutions,isopiestic measurements,magnesium sulfate,pitzer's model,sulfuric acid,atomic and molecular physics, and optics,materials science(all),physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/3100/3107
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: LivePure Connector
Date Deposited: 24 May 2022 15:02
Last Modified: 26 May 2022 14:36
URI: https://ueaeprints.uea.ac.uk/id/eprint/85112
DOI: 10.1006/jcht.1998.0461

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