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Precipitations is usually made from hot solution. Most crystals are appreciably more soluble at 100oC than at room temperature, and consequently the initial degree of super-saturation is less in the hot solution that it would be a cold one. This lead to the formation of the minimum number of initial nuclei. Further advantages are that heat aids in the coagulation of colloidal particles, that the amount of adsorption is decreased by increase in temperature, and that the speed of exchange of ions between solid and solution is increase. Since the solubility is usually increase with rise in temperature, it is necessary is most analyses to cool the solution to room temperature before filtration.