Titre du document / Document title

Synthesis and stability of wroewolfeite, Cu₄SO₄(OH)₆.2H₂O

Auteur(s) / Author(s)

DABINETT Timothy R. ; HUMBERSTONE David ; LEVERETT Peter ; WILLIAMS Peter A. ;

Résumé / Abstract

Titration of aqueous copper(II) sulfate solutions with aqueous NaOH at temperatures ranging from 0 to 25 °C results in a complex Ostwald step rule cascade of basic copper sulfate phases. At 25 °C, the thermodynamically stable phase is brochantite [Cu₄SO₄(OH)₆], but posnjakite [Cu₄SO₄(OH)₆.H₂O] is formed first. At lower temperatures, but above 0 °C, wroewolfeite [Cu₄SO₄(OH)₆.2H₂O] forms first. If left in contact with the reaction solution, wroewolfeite is converted to posnjakite and brochantite in turn. However, at 0 °C, synthetic wroewolfeite is stable for periods longer than a week, even in contact with the reaction solution, and a stability constant could be determined for its formation. For the reaction below, 1g K = -16.3(1) at 0 °C and / = 0, as determined by solution methods. Stability relations between minerals of stoichiometry Cu ₄SO ₄(OH)₆.nH₂O (n=0, 1, 2) are discussed. High concentrations of Mg²⁺ ions (1 M) prevent the isolation of wroewolfeite at any temperature down to 0 °C.

Revue / Journal Title

Pure and applied chemistry   ISSN 0033-4545   CODEN PACHAS 

Source / Source

2008, vol. 80, n^o6, pp. 1317-1323 [7 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Pure and applied chemistry, Research Triangle Park, NC, ETATS-UNIS  (1960) (Revue)

Mots-clés d'auteur / Author Keywords

wroewolfeite ; basic copper sulfates ; synthesis ; stability ; supergene mineralogy ;

Localisation / Location

INIST-CNRS, Cote INIST : 1296, 35400019785501.0100