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The process of purifying copper sulphate by crystallization. It describes the different steps involved in the process, the materials required, and the procedure to be followed. The document also explains the importance of purification and the role of crystallization in achieving it.
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Purification of Copper Sulphate by Crystallization Purification of Copper Sulphate by Crystallization The chemicals used for various purposes should be completely free from any type of impurities. Crystallization is an important purification process in which solid crystals are formed from a uniform solution. The different steps involved in the crystallization process are:
Stand with clamps Sand bath Procedure: Preparation of Solution of the Impure Sample Take about 30 ml of distilled water in a beaker. Add powdered crude sample of copper sulphate using a spatula. Stir the solution gently with the glass rod so that the powder dissolves. Add the powdered sample several times till a little of it remains un-dissolved in the beaker, even if it is stirred for some time. Now, add about 3 ml of dilute sulphuric acid to the solution using the measuring jar and gently stir the solution to make it clear. This prevents the hydrolysis of copper sulphate. Filtration of the Solution Place a filter paper in the funnel and clamp the funnel to the stand. Place the china dish under the funnel. The stem of the funnel should touch the wall of the china dish to avoid the solution splashing out. Pour the solution into the funnel over the glass rod and collect the filtrate in the china dish. The insoluble impurities are left on the filter paper. Concentration of the Filtrate Heat the china dish in a sand bath till the solution is reduced to about one- third of its original volume. To avoid crust formation on the side of the dish, stir the solution continuously with a glass rod. To know if the solution has reached its crystallization point, remove a drop of the solution at the end of the glass rod and cool it by blowing. The appearance of a crust or tiny crystals on the glass rod shows that the crystallization point has been reached. Now, transfer the hot saturated solution into the evaporating dish. Cooling of the Concentrated Solution Place the evaporating dish containing the hot saturated solution in a trough containing water. Cover the dish with the watch glass and allow it to cool slowly for some time. As the solution cools, deep blue crystals of copper sulphate separate and the crystallization will complete after half an hour. Separation and Drying of Crystals Decant the mother liquor carefully into a beaker. Wash the crystals 3 or 4 times with a little ethyl alcohol containing a small amount of cold water. Using the spatula, place the crystals on a filter paper which soaks up the solution. Transfer the crystals on another filter paper and dry them by pressing gently between the folds of the filter paper. Now, transfer the