Nucleation phenomena arising during the dehydration of solid hydrates

Abstract

The lattice vacancies formed on the evaporation of water molecules from the surfaces of potassium chrome alum have little mobility within the crystal. Treatment of crystals of potassium and ammonium chrome alums and copper sulphate pentahydrate in hard vacuum produces a change in the surface which under the catalytic action of water vapour gives rise to nuclei of the solid products. Common alum does not show these phenomena. The anomalous activation energies of the interface reactions of hydrates are discussed.