Abstract
Aqueous suspensions of zeolite(4A) in the potassium and sodium forms have been
separately exchanged with Ca2+ at 25�C in a precision dilatometer to
measure the associated system volume change, ∆Vobs.
Similar experiments partially exchanged K+ into sodium zeolite(4A) and Na+ into potassium zeolite(4A). Tris(ethane-1,2-diamine)cobalt(III) chloride
was also exchanged with sodium zeolite(13X). For the
overall process ∆Vobs is small,
generally well under 10 cm3 per mole of incoming cation exchanged. The results are discussed
in terms of three contributions to the overall volume change: (i) the volume change of ionic replacement in the solution
external to the zeolite (this is available from the
known apparent molar volumes of the electrolytes); (ii) the small dimension
changes of the zeolite lattices on exchange; (iii)
the transfer of water between zeolite and the
solution phase.