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The Precipitation of Alkaline‐Earth Metal Carbonate Powders from Aqueous Solution. Crystal Numbers and Final Sizes
Author(s) -
Packter A.,
Uppaladini S. C.
Publication year - 1974
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.19740090903
Subject(s) - carbonate , precipitation , supersaturation , alkaline earth metal , magnesium , chemistry , metal , strontium carbonate , inorganic chemistry , strontium , solubility , aqueous solution , crystallite , barium , mineralogy , crystallography , organic chemistry , physics , meteorology
Abstract The precipitations of magnesium carbonate trihydrate, basic magnesium carbonate and calcium, strontium and barium carbonates was studied from equivalent solutions of concentrations from 0.0005 M to 1M, at pHs from 10 to 7, by optical microscopy and other methods. Crystal growth started after induction periods: the precipitations of the more sparingly‐soluble metal carbonates — mainly studied at medium to high supersaturation — were homogeneously nucleated while the magnesium carbonate trihydrate precipitations — studied at low supersaturations at pH ≦ 7.6 — were heterogeneously nucleated. The crystal forms and numbers of the final precipitates depended on the type and numbers of nuclei (and crystallites) formed during the induction periods. Crystal numbers generally increased with increasing initial mean metal carbonate concentration according to the relation N = N 1 C MCO3 β ; β was 3 for the metal carbonate precipitations and β was 4 for the basic magnesium carbonate precipitations. N 1 values increased in the order basic MgCO 3 (at pH ≧ 9), or MgCO 3 · 3H 2 O (at pH ≦ 7.6) < CaCO 3 < SrCO 3 < BaCO 3 . The final crystal lengths then generally decreased, from maximum values, with increasing initial concentration according to the relation l fin = l 1 / C MCO 3γ , where γ was 0.7 and 1.0. For precipitation at any concentration and pH, smaller crystal sizes were generally obtained in precipitates from solutions of the metal carbonate of lower solubility.