Basic sodium carbonate precipitation can be obtained by adding sodium carbonate to a dilute copper sulfate solution or by passing carbon dioxide into a suspension of copper hydroxide. 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 because it reacts with hydrochloric acid in the stomach to form copper ions that cause heavy metal poisoning. Drink after poisoning: fresh milk or egg white solution. Basic copper carbonate exists in the form of minerals in nature, commonly known as malachite. It is insoluble in water, soluble in acid, hot water or heated to 220 ° C to decompose into copper oxide, water and carbon dioxide (basic copper carbonate → heated copper oxide + water + 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. The latter chemical formula is 2CuCO3·Cu(OH)2, it can be used to make signal flares, pyrotechnics, insecticides ,paint pigments and antidote, as well as for electroplating. In addition, basic copper carbonate can react with dilute sulfuric acid to form copper sulfate, water and carbon dioxide. The chemical reaction formula is: Cu2(OH)2CO3+ 2H2SO4=2CuSO4+3H2O+CO2 ↑
The precipitate obtained from the solution is initially green, and after standing it becomes dark green in the solution, which is insoluble in water and soluble in acid. Also dissolved in cyanide, ammonium salt and alkali metal carbonate aqueous solution to form a copper complex; Cu2(OH)2CO3: a deep sky blue bright monoclinic crystal, or a tight crystalline group. It is insoluble in water, soluble in ammonia and hot and concentrated sodium bicarbonate solution to form a blue color.
Beautiful green powdery crystals that decompose when heated to 220 °C. Insoluble in water and ethanol, soluble in ammonia to form divalent copper ammonia complexes. Dissolved in acid to form the corresponding copper salt, dissolved in an aqueous solution of cyanide, ammonia, ammonium and alkali metal carbonate to form a copper complex. When boiled in water or heated in a strong alkaline solution, brown copper oxide is formed. It can react with hydrogen sulfide to form copper sulfide. 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, slowly turning into green malachite. In nature, it exists in the form of azurite.
Bright green malachite (CuCO3·Cu(OH)2) and blue azurite (Cu3(CO3)2(OH)2) are two naturally occurring basic copper carbonates.