Copper(II) carbonate
Encyclopedia
Copper carbonate (often called copper carbonate or cupric carbonate) is a blue-green compound
(chemical formula CuCO3) forming part of the verdigris
patina
that is found on weathered brass
, bronze
, and copper
. The colour can vary from bright blue to green, because there may be a mixture of both copper carbonate and basic copper carbonate in various stages of hydration
. It was formerly much used as a pigment
, and is still in use for artist's colours.
It has also been used in some types of make-up, like lipstick
, although it can also be toxic to humans. It also has been used for many years as an effective algaecide in farm ponds and in aquaculture operations. Copper carbonate was the first compound to be broken down into several, separate elements (copper, carbon, and oxygen). It was broken down in 1794 by the French chemist Joseph Louis Proust (1754–1826). When burnt, it thermally decomposes to form CO2 and CuO, a black solid. It can be used to copper plate
a metallic surface by adding sulfuric acid and heat it (to produce copper sulfate) then passing a charge through it with the metal in the liquid. This process is known as electroplating
.
Copper in moist air slowly acquires a dull green coating because its top layer has oxidised with the air. Some architects use this material on rooftops for this interesting colour. The green material is a 1:1 mole mixture of Cu(OH)2
and CuCO3:
Copper carbonate decomposes at 290 °C, giving off carbon dioxide
and leaving copper(II) oxide
:
Basic copper(II) carbonate occurs naturally as malachite
(Cu2(OH)2CO3) and azurite
(Cu3(OH)2(CO3)2).
. Copper basic carbonate precipitates from the solution:
The formation of copper carbonate can be verified in the following steps:
a) Centrifuge the above mentioned solution, 1 minute at 6000 g is sufficient
b) Wash the precipitate with distilled water and centrifuge again
c) The colour of the precipitate is blue, like that of several copper salts but none of the sodium salts
d) If dilute (1M) hydrochloric acid is added, then bubbles of CO2 will emerge and the precipitate will be fully solubilised. These would not be formed if dilute hydrochloric acid was added to solid Na2SO4.
Pure copper carbonate is obtained from basic copper carbonate in the presence of carbon dioxide at 180 °C and 4.6 MPa (46 atm) pressure.
copper carbonate reacts with acids and gives carbon dioxide and corresponding copper(II) salts of that acid:
2) Decomposition:
CuCO3 → CuO + CO2
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
(chemical formula CuCO3) forming part of the verdigris
Verdigris
Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over a period of time. It is usually a basic copper carbonate, but near the sea...
patina
Patina
Patina is a tarnish that forms on the surface of bronze and similar metals ; a sheen on wooden furniture produced by age, wear, and polishing; or any such acquired change of a surface through age and exposure...
that is found on weathered brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
, bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...
, and copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
. The colour can vary from bright blue to green, because there may be a mixture of both copper carbonate and basic copper carbonate in various stages of hydration
Hydration reaction
In organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group and a hydrogen cation are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group. The reaction usually runs in a strong acidic, aqueous...
. It was formerly much used as a pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
, and is still in use for artist's colours.
It has also been used in some types of make-up, like lipstick
Lipstick
Lipstick is a cosmetic product containing pigments, oils, waxes, and emollients that applies color, texture, and protection to the lips. Many varieties of lipstick are known. As with most other types of makeup, lipstick is typically, but not exclusively, worn by women...
, although it can also be toxic to humans. It also has been used for many years as an effective algaecide in farm ponds and in aquaculture operations. Copper carbonate was the first compound to be broken down into several, separate elements (copper, carbon, and oxygen). It was broken down in 1794 by the French chemist Joseph Louis Proust (1754–1826). When burnt, it thermally decomposes to form CO2 and CuO, a black solid. It can be used to copper plate
Copper plating
Copper plating is the process in which a layer of copper is deposited on the item to be plated by using an electric current.Three basic types of processes are commercially available based upon the complexing system utilized:...
a metallic surface by adding sulfuric acid and heat it (to produce copper sulfate) then passing a charge through it with the metal in the liquid. This process is known as electroplating
Electroplating
Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...
.
Copper in moist air slowly acquires a dull green coating because its top layer has oxidised with the air. Some architects use this material on rooftops for this interesting colour. The green material is a 1:1 mole mixture of Cu(OH)2
Copper(II) hydroxide
Copper hydroxide is the hydroxide of the metal copper with the chemical formula of Cu2. Copper hydroxide is a pale blue, gelatinous solid. Some forms of copper hydroxide are sold as "stabilized" copper hydroxide, quite likely a mixture of copper carbonate and hydroxide...
and CuCO3:
- 2 Cu (s) + H2O (g) + CO2 + O2 → Cu(OH)2 + CuCO3 (s)
Copper carbonate decomposes at 290 °C, giving off carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and leaving copper(II) oxide
Copper(II) oxide
Copper oxide or cupric oxide is the higher oxide of copper. As a mineral, it is known as tenorite.-Chemistry:It is a black solid with an ionic structure which melts above 1200 °C with some loss of oxygen...
:
- CuCO3 (s) → CuO (s) + CO2 (g)
Basic copper(II) carbonate occurs naturally as malachite
Malachite
Malachite is a copper carbonate mineral, with the formula Cu2CO32. This green-colored mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Individual crystals are rare but do occur as slender to acicular prisms...
(Cu2(OH)2CO3) and azurite
Azurite
Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France...
(Cu3(OH)2(CO3)2).
Preparation
Copper carbonate is prepared by combining aqueous solutions of copper sulfate and sodium carbonateSodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
. Copper basic carbonate precipitates from the solution:
- 2 CuSO4 + 2 Na2CO3 + H2O → Cu2(OH)2CO3 + 2 Na2SO4 + CO2
The formation of copper carbonate can be verified in the following steps:
a) Centrifuge the above mentioned solution, 1 minute at 6000 g is sufficient
b) Wash the precipitate with distilled water and centrifuge again
c) The colour of the precipitate is blue, like that of several copper salts but none of the sodium salts
d) If dilute (1M) hydrochloric acid is added, then bubbles of CO2 will emerge and the precipitate will be fully solubilised. These would not be formed if dilute hydrochloric acid was added to solid Na2SO4.
Pure copper carbonate is obtained from basic copper carbonate in the presence of carbon dioxide at 180 °C and 4.6 MPa (46 atm) pressure.
Reactions
1) Reaction with acids:copper carbonate reacts with acids and gives carbon dioxide and corresponding copper(II) salts of that acid:
- copper carbonate + hydrochloric acid → copper chloride + water + carbon dioxide:
- CuCO3 + 2HCl → CuCl2 + H2O + CO2
- copper carbonate + sulfuric acid → copper sulfate + water + carbon dioxide:
- CuCO3 + H2SO4 → CuSO4 + H2O + CO2
- copper carbonate + nitric acid → copper nitrate + water + carbon dioxide:
- CuCO3 + 2HNO3 → Cu(NO3)2 + H2O + CO2
- copper carbonate + acetic acid → copper acetate + water + carbon dioxide:
- CuCO3 + 2CH3COOH → Cu(CH3COO)2 + H2O +CO2
2) Decomposition:
- copper carbonate decomposes at 290°C and forms copper(II) oxide:
CuCO3 → CuO + CO2