The volume and compressibility change for the formation of transition metal sulfate ion pairs at 25°C

Antonio Lo Surdo, Frank J. Millero

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The apparent molal volume and adiabatic compressibilities of some transition metal (Mn2+, Co2+ Ni2+, Cu2+, Zn2+, and Cd2+) sulfates have been determined at 25°C. Values of {Mathematical expression} to 11.4 cm3-mole-1 and {Mathematical expression} to 31.3 × 10-4cm3-mole-1-bar-1 at 1 atm were found for the formation of the transition metal sulfate ion pairs. These results are in good agreement with the values obtained from the high-pressure conductance measurements of Fisher et al., Shimizu et al., and Taniguchi et al. The volume and compressibility data indicate that 3.1±0.7 water molecules are lost when transition metals form ion pairs with SO42-. The fractions of inner-sphere ion pairs (20%) estimated in this study are in good agreement with the values obtained from ultrasonic measurements.

Original languageEnglish (US)
Pages (from-to)163-181
Number of pages19
JournalJournal of Solution Chemistry
Issue number3
StatePublished - Mar 1 1980



  • Molal volumes
  • ion pair formation
  • molal compressibilities
  • transition metal sulfates

ASJC Scopus subject areas

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

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