Volume change of ion pair formation: Rubidium nitrate and thallium(I) nitrate in water

William L. Masterton, Harry Welles, Jonathan H. Knox, Frank J. Millero

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Density data for dilute aqueous solutions of RbNO3 and TlNO3 at 25°C lead to the following equations for the apparent molal volumes: RbNO3: ΦV = 43.07 + 2.46 c1/2 + 0.15 c (0-0.41 M) TINO3: ΦV = 39.50 + 10.83 c1/2 - 25.46 c + 26.0 c3/2 (0.03-0.25 M) From these expressions and a semiempirical equation for Φv of a completely dissociated 1:1 electrolyte, values of ΔΦv for ion pair formation at c=0.10 are calculated to be+5 ml-mole-1 for RbNO3 and+12 ml-mole-1 for TlNO3. Comparison of ΔΦv with the electrostriction volume effect suggests that virtually all of the electrostriction is removed in the formation of the TlNO3 ion pair but only about half with RbNO3. Values of ΔΦv are in poor agreement with those estimated from electrostatic theories of ion pair formation.

Original languageEnglish (US)
Pages (from-to)91-102
Number of pages12
JournalJournal of Solution Chemistry
Issue number2
StatePublished - Feb 1 1974


  • Ion pair
  • apparent molal volume
  • density
  • electrolyte solution
  • electrostriction
  • magnetic float
  • rubidium nitrate
  • thallium(I) nitrate

ASJC Scopus subject areas

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


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