Collect. Czech. Chem. Commun. 1982, 47, 1184-1188

The metastable zone width of ammonium aluminium sulphate and mechanisms of secondary nucleation

Jaroslav Nývlt

Institute of Inorganic Chemistry, Czechoslovak Academy of Sciences, 160 00 Prague 6


The metastable zone width of aqueous solution of ammonium aluminium sulphate was measured as a function of the cooling rate. The measurements were carried out a) in the absence of seed crystal, b) with one seed crystal at a fixed position in the flowing solution, and c) with one seed crystal moving freely on the bottom of the measuring vessel. The results obtained distinctly differ for the three measurements, providing evidence that primary nucleation took place in the first case, secondary nucleation induced by the surface-layer mechanism combined with fluid shear occurred in the second case, and the contact mechanism of secondary nucleation operated in the third case.