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The precipitation of barium chromate from aqueous solution (with rapid mixing): Kinetics of the crystal growth
Author(s) -
Packter A.
Publication year - 1977
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.19770120203
Subject(s) - aqueous solution , precipitation , nucleation , crystallization , chromate conversion coating , induction period , crystal growth , crystal (programming language) , barium , crystallite , inorganic chemistry , salt (chemistry) , conductivity , reaction rate constant , chemistry , materials science , kinetics , chromium , crystallography , metallurgy , physics , organic chemistry , meteorology , computer science , programming language , biochemistry , quantum mechanics , catalysis
The kinetics of precipitation of barium chromate from well‐stirred aqueous solutions of initial solute concentrations C 0 = 0.0001 to 0.0010 M (supersaturations 8 to 80) was studied at 25 °C by conductivity measurements and chemical analysis. Nucleation occurred during induction periods and regular crystal growth then took place onto the crystallites formed during the induction periods. The crystal growth was rate‐controlled, in this range, by the rate of deposition of metal salt ions onto the growing crystal surfaces. This rate, at any time, then depended on both the overall surface area ( A t ) and on the residual excess solute concentration (Δ C t ) in solution according to the relation,\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{dc}}{{dt}} = - k_c A_t \,\Delta C\frac{2}{t}\,mole\,{\rm}l^{- 1}\, {\rm sec}^{{\rm - 1}}; $$\end{document} the growth rate expressed in terms of degree of crystallisation was then\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{d\alpha}}{{dt}} = - k_\alpha \alpha _t ^{2/3} [\Delta C_0 (1 - \alpha _t)]^2 \,{\rm sec}^{{\rm - 1}} $$\end{document}The rate constant ( K α ) for the crystallisation of barium chromate at 25 °C was 1.5 10 6 sec −1 M −2 .