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The precipitation of sparingly‐soluble metal salts from aqueous solution: Heterogeneous nucleus numbers at low to intermediate supersaturation
Author(s) -
Packter A.,
Alleem A.,
Chauhan P.,
Uppaladini S. C.
Publication year - 1981
Publication title -
kristall und technik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0023-4753
DOI - 10.1002/crat.19810161219
Subject(s) - supersaturation , nucleation , chemistry , aqueous solution , precipitation , inorganic chemistry , crystallography , tetragonal crystal system , surface energy , crystallite , crystal structure , organic chemistry , physics , meteorology
The precipitation of series of alkaline‐earth metal and transition hydroxides, sulphates, chromates and molybdates, hydrogen phosphate carbonates, oxalates and ‘oxinates’ were studied in aqueous solution of low to intermediate supersaturation. Heterogeneous nucleation probably occurred onto micro‐crystalline particles of some siliceous mineral (of the trigonal, hexagonal or cubic system), dispersed in the solution. The heterogeneous nucleus numbers for these precipitations then depended on the rates of the heterogeneous nucleation onto these substrates and the rates of the mononuclear growth of nuclei to crystallites (during the induction periods). Generally, N het values in polypropylene and glass beakers, at low supersaturation, varied from 10 4 to 10 13 dm −3 : the N het values then increased slightly with concentration and supersaturation according to the relation N het = K N β , where K N is a function of the metal salt surface energy and an ‘epitaxy’ factor; β = 0.4–0.5. In turn, at any supersaturation, log N het = log N het 0+ F σ, where N het 0and F were constants for any precipitation: N het values then increased from 10 4 to 10 8 times for increase in σ from 50 to 150 mJ m −2 . At any supersaturation and surface energy, N het values increased in the order monoclinic < orthohombic < tetragonal < trigonal crystals.