The PVT properties of concentrated aqueous electrolytes. VIII. The volume changes for mixing the major sea salts at an ionic strength of 3.0 from 5 to 95°C

Leslie M. Connaughton, Frank J Millero

Research output: Contribution to journalArticle

16 Scopus citations


The densities of mixtures of the six possible combinations of the four major sea salts (NaCl, Na2SO4, MgCl2, and MgSO4) have been measured at a constant ionic strength of I=3.0 at the temperatures 5, 25, 55, and 95°C. The results have been used to determine ΔVm, the volume change for mixing the major sea salts, which were fitted to equations of the from {Mathematical expression} where y1 is the molal ionic strength fraction of solute i, and vo and v1 are parameters related to the interaction of like-charge ions. The cross-square rule was verified at each of the temperatures of study, but the rule did not hold as well at the higher temperatures. The temperature dependence of the volume change for mixing ΔVm was examined for each of the six mixtures. It was found that the two mixtures NaCl-Na2SO4 and MgSO4-MgCl2 showed little or no variation of ΔVm with temperature, while the other mixtures showed considerable temperature dependence. These results indicate that the anion-anion interactions of Cl- and SO42- do not vary with temperature, while the cation-cation interactions of Na+ and Mg2+ are temperature sensitive. Explanations for these results based on ion-water inter actions are presented.

Original languageEnglish (US)
Pages (from-to)491-502
Number of pages12
JournalJournal of Solution Chemistry
Issue number6
StatePublished - Jun 1987



  • cross-square rule
  • densities
  • MgCl
  • MgSO
  • NaSO
  • NaCl
  • Sea salts
  • volumes of mixing

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this