Copper carbonate, also known as basic copper carbonate, is a malachite green color, so it is also called malachite. It is a precious mineral gem. It is a substance produced by the reaction of copper with oxygen, carbon dioxide and water in the air. It is also called copper rust and is green in color. Heating in air decomposes into copper oxide, water and carbon dioxide. Soluble in acid and form the corresponding copper salt. It is also soluble in cyanide, ammonium salts and aqueous alkali metal carbonate solutions to form copper complexes. When boiled in water or heated in a strong alkali solution, brown copper oxide is formed and decomposed into black copper oxide at 200 °C. It is unstable in hydrogen sulfide atmosphere and can react with hydrogen sulfide to form copper sulfide. There are more than ten forms of compounds in the basic copper carbonate according to the ratio of CuCO3:H2O. It exists in the form of malachite in nature.
When placed in the air for a long time, it absorbs moisture and emits carbon dioxide, which gradually turns into a green malachite. It exists in the form of azurite in nature.
Copper carbonate and copper hydrogencarbonate are not actually present. Precipitation of basic copper carbonate can be obtained by adding sodium carbonate to a dilute copper sulfate solution or by passing carbon dioxide into a copper hydroxide suspension. Basic copper carbonate can be regarded as composed of copper hydroxide and copper carbonate. Actually, there are two kinds of copper hydroxide, copper carbonate and copper hydroxide.
The former chemical formula is CuCO3·Cu(OH)2, which is a grass-green monoclinic crystalline fibrous group or a dark green powder. The precipitate obtained from the solution initially appeared green, and after leaving it turned dark green in the solution. It is toxic and is the main component of green rust (commonly known as patina) produced on the copper surface.
The latter chemical formula is 2CuCO3·Cu(OH)2, deep sky blue, very bright monoclinic crystals, or tightly crystalline lumps. It is insoluble in water, soluble in ammonia and hot and concentrated sodium bicarbonate solution to form a blue color, which decomposes at 300 °C.
Basic copper carbonate can be used in the manufacture of signal flares, pyrotechnics, paint pigments, other copper salts, solid phosphor activators, insecticides, seed treatments and as fungicides and antidotes, as well as in electroplating.