Basic copper carbonate is a general term of a series […]
Basic copper carbonate is a general term of a series of compounds, not just the composition of Cu2 (OH) 2CO3 (chemical formula).
For example, the main component of natural malachite is an alkaline copper carbonate. The chemical formula can be written as Cu2 (OH) 2CO3 or CuCO3 · Cu (OH) 2. The color is green, but there is also a natural ore called bronze. The main chemical formula can be written Cu3 (OH) 2 (CO3) 2 or 2CuCO3. Cu (OH) 2, still called basic copper sulfate, is blue. In fact, in the sodium carbonate solution, CO 3 2- and OH- are simultaneously present in the solution due to the hydrolysis of carbonate ions. After the copper sulfate solution is added, bases having different compositions can be formed depending on the concentration of the reactants. The basic formula for the precipitation of copper carbonate and basic copper carbonate can be expressed as xCuCO3 · Cu (OH) 2 or even xCuCO3 · Cu (OH) 2 · zH2O. It usually has a very complex structure and can be interpreted as Complexes about hydroxide ions that act as oxygen bridges. There may also be some changes in the composition of the newly precipitated alkaline copper carbonate after "aging".
Generally (approximately), the more concentrated the sodium carbonate solution, the higher the concentration of carbonate ions, the more likely it is to form xCuCO3 · Cu (OH) 2 precipitates with larger x values, and the color of the precipitates is bluer, so the preparation for For basic copper carbonate Cu2 (OH) 2CO3, the method of adding sodium carbonate solution to copper sulfate solution should be used. It should not be reversed. When carbon dioxide bubbles are emitted, slowly add the sodium carbonate solution and stir well. , Control the pH value of the final solution not too high (pH = 8), and allow the precipitate to stand for a period (can be left for 24 hours) after the precipitate is completely aged, and then filtered.