KINETICS OF PRECIPITATION OF NICKEL AMMONIUM-SULFATE HEXAHYDRATE FROM AQUEOUS-SOLUTIONS

The precipitation of nickel ammonium sulphate [Ni(NH4)2(SO4)2·6H2O] prepared by mixing of equimolar aqueous solutions of (NH4)2SO4 and NiSO4 has been studied at 25 °C. Precipitation induction periods and the number of crystals formed per unit volume have been determined experimentally as functions of supersaturation for values of Sa, H < 2.6. The mechanisms of nucleation and crystal growth are assessed by comparing the experimental results with theoretical predictions. In this system, heterogeneous nucleation and crystal growth are assessed by comparing the experimental results with theoretical predictions. In this system, heterogeneous nucleation appears to operate at Sa, H < 1.3, whereas at Sa, H > 1.6 crystals are generated predominantly by homogeneous nucleation and grow by a polynuclear mechanism. The interfacial tension of nickel ammonium sulphate crystals in contact with their supersaturated solution is estimated to be about 20 mJ/ m2. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim