when zinc comes into contact with humid air containing carbon dioxide, a dense film will be formed on the surface, which can protect its interior from being oxidized. this film is basic zinc carbonate (ZnCO3 · 3Zn(OH)2), and basic zinc carbonate is a relatively tight protective film. Reaction equation: CO2 4Zn 2O2 3H2O = ZnCO3 · 3Zn(OH)2.
Natural basic zinc carbonate minerals are called "water zinc ore". Chemical formula ZnCO3 · 2Zn(OH)2 · H2O. Molecular weight 342.15. White amorphous powder. Relative density 4.42~4.45. Soluble in dilute acid and alkali, slightly soluble in ammonia and ammonium salt, insoluble in water, ethanol and acetone. Decompose to carbon dioxide and zinc oxide at 300 ℃. It reacts with H2O2 to release CO2 and form peroxide. Fluorescence can occur when heated to room temperature at 250~500 ℃ for different times.
Preparation method: Basic zinc carbonate is also called transparent zinc white. When zinc white ZnO is manufactured by wet method, the calcination temperature is controlled to produce by-product, because it is a white transparent powder. In industry, soda ash solution is added to zinc sulfate solution to produce white basic zinc carbonate precipitate. Wash it with water and filter it to be the product. 4ZnSO4 4Na2CO3 H2O & rarr;3 ZnCO3 · Zn (OH)2 4Na2SO4 CO2. In addition, zinc carbonate can be prepared by boiling together with water.
Basic zinc carbonate uses: can be used to make latex film products, pigments, rayon, catalytic desulfurizer, medicine with basic zinc carbonate as a light astringent, preservative, talcum powder, disinfectant and skin protection agent. Since the transparency of basic zinc carbonate is close to that of natural rubber, it is used as a reinforcing agent and vulcanization accelerator in transparent rubber products.