Synthesis and Stabilities of the Basic Copper(II) Chlorides Atacamite, Paratacamite and Botallackite

A. M. Pollard, R. G. Thomas and P. A. Williams
School of Chemistry and Applied Chemistry, University of Wales College of Cardiff, P.O. Box 912, Cardiff CF1 3TB

Abstract: Strictly reproducible syntheses of the trimorphs of composition Cu2Cl(OH)3, atacamite, paratacamite, and botallackite, have been developed. In syntheses involving direct precipitation, or reaction of aqueous solutions with solid phases, reliable results are obtained only if the temperature and time of reaction are carefully controlled. Botallackite, the rarest of the naturally occurring trimorphs, is a key intermediate and crystallizes first under most conditions; subsequent recrystallization of this phase to atacamite or paratacamite, or of the latter from the former, depends upon the precise nature of the reaction medium. The crystallization sequence indicates that paratacamite, as has long been suspected, is the thermodynamically stable phase at ambient temperatures. Spertiniite, Cu(OH)2, can be reproducibly synthesized via one route in the non-commutative titration of aqueous copper chloride with aqueous sodium hydroxide solutions.

Keywords: synthesis • stability • copper(II) chlorides • atacamite • paratacamite • botallackite

Mineralogical Magazine; December 1989 v. 53; no. 373; p. 557-563; DOI: 10.1180/minmag.1989.053.373.06
© 1989, The Mineralogical Society
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