Journal of Applied Electrochemistry

, Volume 20, Issue 4, pp 651–655 | Cite as

Characterization and use of aqueous caesium chloride as an ultra-concentrated salt bridge

  • P. R. Mussini
  • F. D'Andrea
  • A. Galli
  • P. Longhi
  • S. Rondinini
Papers

Abstract

Five strong aqueous binary electrolytes — one symmetrical (CsCl) and four unsymmetrical (Li2SO4, K2SO4, Rb2SO4, Cs2SO4) — have been examined, for possible use as salt bridges for the minimization of liquid junction potentials (EL), up to the highest concentrations practicable, by the method of homoionic transference cells: Pt−Ir | Cl2 | CsCl (m2) ‖ CsCl (m1) | Cl2 | Pt−Ir and Hg | Hg2Cl2 | CsCl (m2) ‖ CsCl (m1) | Hg2Cl2 | Hg for CsCl, and Hg | Hg2SO4 | Me2SO4 (m2) ‖ Me2SO4 (m1) | Hg2SO4 | Hg for the Me2SO4 sulphates where Me=Li, K, Rb and Cs. CsCl, K2SO4, Rb2SO4, and Cs2SO4, prove to belong to the class obeying close equality of transference numbers for their ions, that is,t+= |t|=0.5, over the whole concentration range (namely, from infinite dilution up to saturation). This result qualifies aqueous CsCl as an unrivalled salt bridge, whose equitransference is obeyed more stringently than any other salt. This is now demonstrated experimentally over the whole molality range, the saturation molality being as high as 11.30 mol kg−1 at 25°C. The observed propertyt+=|t|=0.5 excludes K2SO4, Rb2SO4, and Cs2SO4, as possible salt bridges because the equitransference conditions for minimization ofEL's are τ+ = |τ| = l/(z+ + |z|) = 0.333, i.e.,t+=0.333 andt=2t+=0.667. Finally, Li2SO4, though behaving quite differently from the other three sulphates studied, does not sufficiently approach the required conditions, contrary to what one might have hoped from its known infinite-dilution transference numbers.

Keywords

Sulphate Chloride Rb2SO4 Me2SO4 CsCl 

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Copyright information

© Chapman and Hall Ltd 1990

Authors and Affiliations

  • P. R. Mussini
    • 1
  • F. D'Andrea
    • 1
  • A. Galli
    • 1
  • P. Longhi
    • 1
  • S. Rondinini
    • 1
  1. 1.Department of Physical Chemistry and ElectrochemistryUniversity of MilanMilanoItaly

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