The process to obtain pure solids of copper sulphate is called crystallisation.

Crystallisation is a process in which a solid substance is dissolved in a solvent to form a solution, and then the solvent is slowly evaporated or cooled down to allow the formation of pure solid crystals. This method is commonly used to purify solids and separate them from impurities.

The steps involved in the process of crystallisation are:

1. Dissolving the solid: The first step in the process is to dissolve the solid substance, in this case, copper sulphate, in a suitable solvent. The solvent used should be able to dissolve the solid at a high temperature but have a low solubility at a lower temperature. In the case of copper sulphate, water is commonly used as the solvent.

2. Heating and stirring: The mixture of the solid and solvent is heated and stirred to ensure that the solid completely dissolves in the solvent. The heating helps to increase the solubility of the solid in the solvent.

3. Filtering: After the solid is completely dissolved, the solution is filtered to remove any insoluble impurities that may be present. This step helps to obtain a clear solution.

4. Cooling or evaporation: The filtered solution is then allowed to cool down slowly or evaporate slowly. As the temperature decreases, the solubility of the solid decreases, and the solid particles start to come together to form crystals. The crystals grow over time and can be observed as the solution becomes more concentrated.

5. Separating the crystals: Once a sufficient amount of crystals has formed, they can be separated from the remaining solution. This can be done by carefully pouring off the solution or using a filter paper to collect the crystals.

6. Drying the crystals: The separated crystals are then dried to remove any remaining moisture. This can be done by placing the crystals on a filter paper or in an oven at a low temperature.

By following these steps, pure solids of copper sulphate can be obtained through the process of crystallisation. The crystals obtained are usually more pure compared to the original solid, as impurities are left behind in the solution during the filtration and crystallisation process.