The use of the specific interaction model to estimate the partial molal volumes of electrolytes in seawater

Frank J. Millero

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The specific interaction model has been used to determine the partial molal volume of electrolytes in 0.725 m NaCl and 35‰ salinity seawater solutions at 25°C. The partial molal volumes of electrolytes (MX) were estimated at a given ionic strength (I) from V(MX) = V0(MX) + SvI 1 2 (1 + I 1 2) + vM ∑ XBMX[X] + vX ∑ MBMX[X], where SV is the Debye-Hückel limiting law slope, vi is the number of ions i formed when MX dissociated, [i] is the total molality of ion i and BMX is a specific interaction parameter that varies slowly with ionic strength. The values of V(MX) estimated by using this equation were found to agree very well with experimental values in NaCl and seawater providing there are not strong interactions between M and X. For electrolytes that form ion pairs (i.e. MX°) corrections must be made. Methods are discussed for making these corrections.

Original languageEnglish (US)
Pages (from-to)215-223
Number of pages9
JournalGeochimica et Cosmochimica Acta
Issue number2
StatePublished - Feb 1977


ASJC Scopus subject areas

  • Geochemistry and Petrology

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