The volume and compressibility change for the formation of the LaSO4+ ion pair at 25°C

Chen Tung Chen, Frank J. Millero

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


The apparent molal volumes (φv) and adiabatic compressibilities [φK(S)] of La2(SO4)3 solutions have been determined from density and sound speed data at 25°C. The large positive deviations of φv and φK(S) of La2(SO4)3 from the limiting law have been attributed to the formation of the ion pair LaSO4+. The observed values of φv and φK(S) have been used to estimate the change in the apparent molal volume and adiabatic compressibility for the formation of LaSO4+ from {Mathematical expression} where φ{symbol}(2La3+, 3SO42-) is the apparent molal volume or adiabatic compressibility of the free ions, and α is the degree of association. The value of {Mathematical expression} and {Mathematical expression} at infinite dilution are in reasonable agreement with the values determined from the high-pressure conductance data of Fisher and Davis. The number of hydrated water molecules (ca. 11) associated with the formation of LaSO4+ determined from the volume and compressibility data are in good agreement.

Original languageEnglish (US)
Pages (from-to)589-607
Number of pages19
JournalJournal of Solution Chemistry
Issue number9
StatePublished - Sep 1 1977


  • Lanthanum sulfate
  • adiabatic apparent molal compressibility
  • apparent molal volume
  • density
  • electrostriction
  • hydration number
  • ion pair
  • magnetic float densimeter
  • sound velocimeter

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Physical and Theoretical Chemistry


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