1. When weigh the crude copper sulfate crystal, we should first grind it in the mortar, otherwise it will be difficult and time consuming to weigh and dissolve.
2. Stir with a glass rod to dissolve when heated to dissolve, but the glass rod should not touch the wall of the beaker, otherwise the beaker will be damaged.
3. When using pH test paper, the test paper should not be directly put into the beaker solution, otherwise it will not only make the measurement inaccurate, but also contaminate the solution.
4. During the precipitation process, pH test paper should be used to detect the acidity and alkalinity of the solution, and the pH value of the solution should be controlled to about 4. If the pH value is too small, Fe(OH) will not completely affect the purity of the product copper sulfate. If the pH value is too large, Cu(OH)2 will also precipitate, which will affect the yield of the product.
5. During the evaporation process, the evaporating dish is heated on the asbestos wire mesh and concentrated to a thin layer of crystal on the surface of the solution. It is very prone to bumping and splashing the liquid. Therefore, the heating should be stopped at this time, and it should not be evaporated. Residual mother liquor also facilitates the dissolution of soluble impurities, thus ensuring the purity of the CuSO4″3H2O crystal obtained by recrystallization. Of course, insufficient concentration and too much residual mother liquor will also affect the yield of copper sulfate crystals obtained by recrystallization. .
6. Before pumping and filtering, some of the crystals remaining in the evaporating dish can be carefully transferred to the Buchner funnel with a glass rod. When pumping the air, drain the mother liquor entrained between the crystals as much as possible and wash with alcohol. After pumping and vacuuming, the crystals in the Buchner funnel should be completely taken out, and the precipitated or dried ones should be sucked with absorbent paper or filter paper, but the crystals obtained by recrystallization should not be baked and baked to avoid losing crystal water.