The partial molal volume and compressibility change for the formation of the calcium sulfate ion pair at 25°C

Frank J Millero, Francis Gombar, Jeffrey Oster

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

The apparent molal volumes (φv) and compressibilities (φK) of CaSO4 solutions have been determined at 25°C from precise density and sound-speed measurements. The large deviations of the values of φv and φK from the limiting law and various additivity estimates for the free ions (Ca2+, SO4 2-) have been used to estimate the partial molal volume ( {Mathematical expression}) and compressibility ( {Mathematical expression}) for the formation of the CaSO4 0 ion pair. Values of {Mathematical expression}= 25 ± 3 cm3-mole-1 and {Mathematical expression}= (54±21)×10-4 cm3-mole-1-bar-1 were found. Since these values are larger than the value for the formation of MgSO4 0, the results indicate that more inner-sphere ion pairs are formed when SO4 2- complexes with Ca2+ than with Mg2+. Using a simple model for ion-water interactions, the percent of inner-sphere or contact ion pairs in CaSO4 solutions is estimated to be 36 to 37%.

Original languageEnglish (US)
Pages (from-to)269-280
Number of pages12
JournalJournal of Solution Chemistry
Volume6
Issue number4
DOIs
StatePublished - Apr 1977

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Calcium Sulfate
Compressibility
compressibility
calcium
sulfates
Ions
ions
estimates
Contacts (fluid mechanics)
Acoustic waves
deviation
acoustics
Water
water
interactions

Keywords

  • Calcium sulfate
  • ion pair
  • molal volume and compressibility

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

The partial molal volume and compressibility change for the formation of the calcium sulfate ion pair at 25°C. / Millero, Frank J; Gombar, Francis; Oster, Jeffrey.

In: Journal of Solution Chemistry, Vol. 6, No. 4, 04.1977, p. 269-280.

Research output: Contribution to journalArticle

Millero, Frank J ; Gombar, Francis ; Oster, Jeffrey. / The partial molal volume and compressibility change for the formation of the calcium sulfate ion pair at 25°C. In: Journal of Solution Chemistry. 1977 ; Vol. 6, No. 4. pp. 269-280.
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