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Corrected values of osmotic and activity coefficients of aqueous NaTcO4 and HTcO4 at 25°C

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Abstract

Published isopiestic molalities for aqueous NaTcO4 and HTcO4 solutions at 25°C have been reexamined. Our calculations indicate that published smoothed values of the osmotic coefficients ϕ and mean molal activity coefficients γ± of NaTcO4 are substantially in error, by up to 100% for ϕ and 300% for γ±. Published smoothed values of ϕ and γ± for HTcO4 solutions are in somewhat better agreement with the input data, but the reported ϕ are sometimes higher and sometimes lower than experimental values, by up to 6%. Consequently, we have reanalyzed isopiestic data for these two systems, and find that errors arose in representing the data mathematically. We report parameters for an extended form of the specific ion interaction equations and for Pitzer's equations, and corrected values of ϕ and γ± are tabulated for aqueous NaTcO4 and HTcO4.

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Correspondence to Joseph A. Rard.

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Rard, J.A., Miller, D.G. Corrected values of osmotic and activity coefficients of aqueous NaTcO4 and HTcO4 at 25°C. J Solution Chem 20, 1139–1147 (1991). https://doi.org/10.1007/BF01075131

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Key words

  • Osmotic coefficients
  • activity coefficients
  • aqueous solutions
  • sodium pertechnetate
  • pertechnetic acid