Basic copper carbonate
Template:Short description Template:For Template:Chembox Basic copper carbonate is a chemical compound, more properly called copper(II) carbonate hydroxide. It can be classified as a coordination polymer or a salt. It consists of copper(II) bonded to carbonate and hydroxide with formula Template:Chem2. It is a green solid that occurs in nature as the mineral malachite. It has been used since antiquity as a pigment, and it is still used as such in artist paints, sometimes called verditer, green bice, or mountain green.<ref name=Ullmann>Template:Cite book</ref>
Sometimes basic copper carbonate refers to Template:Chem(Template:Chem)2(Template:Chem)2, a blue crystalline solid also known as the mineral azurite. It too has been used as pigment, sometimes under the name mountain blue or blue verditer.
Both malachite and azurite can be found in the verdigris patina that is found on weathered brass, bronze, and copper. The composition of the patina can vary, in a maritime environment depending on the environment a basic chloride may be present, in an urban environment basic sulfates may be present.<ref>Encyclopedia Of Corrosion Technology (Google eBook), Philip A. Schweitzer P.E.; CRC Press, 2004, Template:ISBN</ref>
This compound is often improperly called (even in chemistry articles) copper carbonate, cupric carbonate, and similar names. The true (neutral) copper(II) carbonate CuCO3 is not known to occur naturally.<ref>Template:Holleman&Wiberg</ref> It is decomposed by water or moisture from the air. It was synthesized only in 1973 by high temperature and very high pressures.<ref name="SeidelEhrhardt1974">Template:Cite journal</ref>
PreparationEdit
Basic copper carbonate is prepared by combining aqueous solutions of copper(II) sulfate and sodium carbonate. Basic copper carbonate precipitates from the solution, with release of carbon dioxide Template:Chem:<ref name="hep">Jack Reginald Irons Hepburn (1927): "The chemical nature of precipitated basic cupric carbonate". Article CCCLXXXVI, Journal of the Chemical Society (Resumed), volume 1927, pp. 2883–2896. {{#invoke:doi|main}}</ref>
Basic copper carbonate can also be prepared by treating aqueous solutions of copper(II) sulfate with sodium bicarbonate.
Copper(II) sulfate may also be substituted with Copper(II) chloride.
ReactionsEdit
Basic copper carbonate is decomposed by acids, such as solutions of hydrochloric acid Template:Chem, into the copper(II) salt and carbon dioxide.
In 1794 the French chemist Joseph Louis Proust (1754–1826) thermally decomposed copper carbonate to CO2 and CuO, cupric oxide.<ref>Template:Cite journal</ref>
The basic copper carbonates, malachite and azurite, both decompose forming H2O, CO2, and CuO, cupric oxide.<ref name="BrownMackenzie1984">Template:Cite journal</ref>
UsesEdit
Basic copper carbonate is used to remove thiols and hydrogen sulfide from some gas streams, a process called "sweetening". Like many other copper compounds, it also has been used as an algaecide, wood preservative and similar applications. It is a precursor to various catalysts and copper soaps.<ref name=Ullmann/>
Both malachite and azurite, as well as synthetic basic copper carbonate have been used as pigments.<ref>Valentine Walsh, Tracey Chaplin, Pigment Compendium: A Dictionary and Optical Microscopy of Historical Pigments, 2008, Routledge, Template:ISBN</ref> One example of the use of both azurite and its artificial form blue verditer<ref>Blue verditer, ColourLex</ref> is the portrait of the family of Balthasar Gerbier by Peter Paul Rubens.<ref>Robert L. Feller, Rubens’s: The Gerbier Family: Technical Examination of the Pigments and Paint Layers, Studies in the History of Art, Vol. 5 (1973), pp. 54–74.</ref> The green skirt of Deborah Kip is painted in azurite, smalt, blue verditer (artificial form of azurite), yellow ochre, lead-tin-yellow and yellow lake. The green color is achieved by mixing blue and yellow pigments.<ref>Peter Paul Rubens, The Gerbier Family, ColourLex</ref>
ReferencesEdit
External linksEdit
- National Pollutant Inventory – copper and compounds fact sheet
- Azurite at ColourLex
- Blue verditer at ColourLex