Issue 7, 1981

Volumes of aqueous electrolyte solutions and the Tammann–Tait–Gibson model

Abstract

The Tammann–Tait–Gibson (TTG) equation for the partial molal volumes of aqueous electrolytes is compared with the Masson and Redlich equations. The TTG equation is shown to be equivalent to the Masson equation and the relationships between the coefficients are given. The TTG effective pressure function is derived for NaCl, NaBr, MgCl2, Na2SO4 and MgSO4 from reliable density data at 25 °C and shown to be entirely consistent with the corresponding compressibility data. The derivation was made using a number of constraints that ensured correct extrapolation to zero. The Masson and TTG coefficients in I½(I is the ionic strength) were found to be equivalent. Within the experimental and fitting errors, these coefficients are a linear function of the standard ionic entropies. The difference between the Debye–Hückel (DH) and TTG slopes for I½ is given by: S(TTG) – S(DH) = 0.20 + 0.0444{ν+[s with combining macron]+° – 1.4[ν[s with combining macron]° + nΔ[s with combining macron]diss°(H2O)]} where ν+, ν are the number of moles of cation and anion, respectively, in 1 mole of salt, [s with combining macron]+°, [s with combining macron]° are the corresponding standard entropies (relative to [s with combining macron]H+° = 0), Δ[s with combining macron]diss°(H2O) is the entropy of ionization of water and n is the number of moles of water affected by 1 mole of the salt. This equation applies to seventy electrolytes with an average deviation of ± 0.23; the slopes range in value from 0 to 14.6 cm3 kg½ mol[fraction three-over-two]. The TTG volume is shown to be simply related to the standard entropies and when the ions become point charges S(TTG) = S(DH).

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans. 1, 1981,77, 1529-1542

Volumes of aqueous electrolyte solutions and the Tammann–Tait–Gibson model

J. V. Leyendekkers, J. Chem. Soc., Faraday Trans. 1, 1981, 77, 1529 DOI: 10.1039/F19817701529

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