Oct., 1957
THEp’-p TRANSITION IN LrPb
1413
for studying Cs-Ba exchange equilibria is therefore short times (up t o a few days). Ion-exchange of surface ions, however, occurs rapidly (within a few available. I n the exchange experiments with ground micas minutes, usually). Strong preferential uptake of described above, it seems probable that decay prod- certain ions in low concentration may occur, but it uct Ba (and other extraneous ions, if any) mas is unlikely that any completely irreversible excompletely adsorbed by the mica. On the basis change occurs with t8he ions we have used (the of Cs decay alone, there would not have been radiometric measurements exhibit an anomaly on enough Ba present to account for the observed this point, but the other work does not confirm anomalies. However, the possibility of their that result). origin in such impurity effects cannot be ruled out. Potassium and hydrogen ions apparently can fill all of the available ion exchange sites. Whether Conclusions Cs+ (about 25% larger than I
