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The relative stabilities of the copper hydroxyl sulphates

  • C. H. Yoder (a1), T. M. Agee (a1), K. E. Ginion (a1), A. E. Hofmann (a1), J. E. Ewanichak (a1), C. D. Schaeffer (a2), M. J. Carroll (a2), R. W. Schaeffer (a3) and P. F. McCaffrey (a3)...


The literature contains considerable disagreements on the relative stabilities of the members of the copper hydroxyl sulphate family. Titration of copper sulphate with sodium hydroxide is claimed by some to produce only brochantite, while other reports indicate that antlerite and a dihydrate of antlerite are produced in the titration. Most stability field diagrams show that antlerite is the more stable stoichiomer at pH 4 and sulphate activity of 0.05–1. We have reexamined this stoichiometric family by titration of aqueous copper sulphate with sodiumhydroxide and sodium carbonate, reverse titration of sodiumhydroxide with copper sulphate and simultaneous addition of copper sulphate and sodium hydroxide at a variety of mole ratios, concentrations, temperatures and reaction times. We have also explored the reaction of copper hydroxide with copper sulphate and the reaction of weak bases, such as sodiumacetate, sodiumcarbonate and urea, with copper sulphate. Our work indicates that: (1) antlerite is not formed in reactions of 0.05 to 1.2 M CuSO4 with 0.05–1.0 M NaOH or Na2CO3 at room temperature; (2) antlerite is formed in the addition of small concentrations of base (≤0.01 M) to 1 M CuSO4 at 80°C, but not at roomtem perature or with 0.01 M CuSO4 at 80°C; (3) the formation of Cu5(SO4)2(OH)6·4H2O occurs at large Cu2+ to base mole ratios; (4) the compound described in the literature as antlerite dihydrate is actually Cu5(SO4)2(OH)6.4H2O; (5) at mole ratios of Cu2+ to OH ranging from 2:1 to 1:2 the predominant product is brochantite; and (6) brochantite and Cu5(SO4)2(OH)6.4H2O are converted to antlerite in the presence of 1 M CuSO4 (the latter requires temperatures of 80°C or greater).

The Ksp (ion activity product) values of antlerite and brochantite were determined to be 2.53 (0.01)⨯10−48 and 1.01 (0.01)⨯10−69, respectively, using atomic absorption spectroscopy and Visual MINTEQ after equilibration in solutions of varying ionic strength and pH for six days. These values are in good agreement with those from the literature. However, after 6 months, antlerite in contact with solution is partially converted to brochantite and hence is metastable with a relatively low conversion rate. The Ksp value for antlerite must therefore be considered approximate. The relative stabilities of the copper hydroxyl sulphates are rationalized using appropriate equations and Gibbs energy calculations. A Gibbs free energy of formation for Cu5(SO4)2(OH)6.4H2O of –3442 kJ/mol was obtained from the simple salt approximation.


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Balarew, C. and Markov, L. (1986) Synthesis and stability of Cu(OH)x(A)y type minerals (A = Cl, NO3 , SO4 2−). Pp. 295–303 in Morphology and Phase Equilibria of Minerals. Proceedings 13th General Meeting, International Mineralogical Association, Bulgarian Academy of Sciences, Sofia.
Bandy, M.C. (1938) Mineralogy of three sulphate deposits of northern Chile. American Mineralogist, 23, 669–695.
Barton, P.B. Jr., and Bethke, P.M. (1960) Thermodynamic properties of some synthetic zinc and copper minerals. American Journal of Science, A258, 21–34.
Binder, O. (1934) The definition of the basic sulfates of copper. Annales de Chimie, 5, 337–409.
Chavez, W.X. Jr., (2000) Supergene oxidation of copper deposits: zoning and distribution of copper oxide minerals. SEG Newsletter, 41, 9–21.
Dasent, W.E. (1982) Inorganic Energetics. 2 nd edition, Cambridge University Press, Cambridge, UK.
Lachenal, G. and Gauthier, J. (1969) Basic copper sulfate, 2CuSO4.3Cu(OH)2.5H 2 O. Comptes Rendus des Seances de l’Academie des Sciences, 268, 2095–2097.
Lachenal, G. and Vingalou, J. (1983) Thermal behavior of copper hydroxysulfate 2CuSO4.Cu(OH)2.4H2O and copper hydroxyselenate 2CuSeO4.Cu(OH)2. 4H2O. Thermochimica Acta, 64, 207–227.
Latimer, W.M. (1952) The Oxidation States of the Elements and their Potentials in Aqueous Solutions. 2nd edition, Prentice–Hall, Inc., New York.
Lin’ko, I.V., Kulikov, A.B., Venskovskii, N.U., Lobanov, N.N., Zaitsev, B.E. and Ezhov, A.I. (2001) Deposition of copper (II) hydroxosulfates by urea. Russian Journal of Inorganic Chemistry, 46, 298–301.
Livingston, R.A. (1991) Influence of the environment on the patina of the statue of liberty. Environmental Science and Technology, 25, 1400–1408.
Pollard, A.M., Thomas, R.G. and Williams, P.A. (1992) The stabilities of antlerite and Cu3SO4(OH)4.H2O: their formation and relationships to other copper (II) sulfate minerals. Mineralogical Magazine, 56, 359–365.
Posnjak, E. and Tunell, G. (1929) The system, cupric oxide–sulfur trioxide–water. American Journal of Science, 18, 1–33.
Tanaka, H. and Koga, N. (1988) Preparation and thermal decomposition of basic copper (II) sulfates. Thermochimica Acta, 133, 221–226.
Tanaka, H. and Koga, N. (1990) The thermal decomposition of basic copper(II) sulfate: an undergraduate thermal analysis experiment. Journal of Chemical Education, 67, 612–614.
Tanaka, H., Kawano, M. and Koga, N. (1991) Thermogravimetry of basic copper(II) sulfates obtained by titrating NaOH solution with CuSO4 solution. Thermochimica Acta, 182, 281–292.
Wagman, D.D., Evans, W.H., Parker, V.B., Schumm, R.H., Halow, I., Bailey, S.M., Churney, K.L. and Nuttall, R.L. (1982) The NBS tables of chemical thermodynamic properties. Journal of Physical and Chemical Reference Data, 11, supplement 2.
Weiser, H.B., Milligan, W.O. and Cook, E.L. (1942) Hydrous cupric hydroxide and basic cupric sulfates. Journal of the American Chemical Society, 64, 503–508.
Yoder, C.H. and Flora, N.J. (2005) Geochemical applications of the simple salt approximation to the lattice energies of complex materials. American Mineralogist, 90, 488–496.
Young, S.W. and Stearn, A.E. (1916) The basic copper sulfates. Journal of the American Chemical Society, 38, 1947–1953.



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