Abstract
Salt solutions saturated at 44° C and containing varying amounts of lead ions were allowed to cool to about 29°C in 5.5 h. The total heat, ΔHt, evolved decreased to 2/3 of its highest value with the increase of Pb2+‐concentration, while the amount of salt crystallized, Wc, decreased to nil. The distribution coefficient of Pb2+ between crystals and solution was 10.5 and 9.8 for KBr and KCl respectively. The high lead content improved the perfection of the crystals. The results are consistent with a two‐stage mechanism of crystallization: heterogeneous nucleation by complex ions and growth of crystals by the addition of bloc nuclei.