The chemical stability of mimetite and distribution coefficients for pyromorphite-mimetite solid-solutions

Inegbenebor, A. I. and THOMAS, JOHN H. and WILLIAMS, PETER A. (1989) The chemical stability of mimetite and distribution coefficients for pyromorphite-mimetite solid-solutions. Mineralogical Magazine, 53. pp. 363-371.

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Abstract

The equilibrium solubility of mimetite has been determined in aqueous solution at 298.2 K. For the reaction Pb5(As04) 3Cl(s,mimetite) + 6H+(aq) ;= 5Pb2+(aq) + 3H2As04(aq) + Cl-(aq) at this temperature log KH+• extrapolated to zero ionic strength, is equal to -27.9(4). This value is equal, within experimental error, to that corresponding to pyromorphite, Pb5(P04) 3Cl, derived from the literature, and redetermined here under analogous conditions. Distribution coefficients in terms of both HXOi- and H2X04(aq) ions (X= P,As) have also been determined for solid phases of the pyromorphite-mimetite solid solution series containing from 5 to 95 mol.% mimetite. Although the two end-members are isostructural without being strictly isomorphous, the solid solution series behaves ideally over the whole compositional range; that is, the composition of the solid phase reflects the ratio of arsenate to phosphate species in aqueous solution at pH values corresponding to naturallyoccurring aqueous solutions generally associated with the oxidized zones of base metal orebodies. Some relationships between mimetite and other secondary lead(II) and copper(II) arsenate minerals have been explored

Item Type:	Article
Uncontrolled Keywords:	chemical stability, mimetite, distribution coefficients, pyromorphite-mimetite, solidsolutions.
Subjects:	Q Science > Q Science (General) Q Science > QD Chemistry
Divisions:	Faculty of Engineering, Science and Mathematics > School of Chemistry
Depositing User:	Mrs Hannah Akinwumi
Date Deposited:	01 Apr 2015 10:29
Last Modified:	01 Apr 2015 10:29
URI:	http://eprints.covenantuniversity.edu.ng/id/eprint/4530

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