The solubility or saturation condition is experimentally determined by heating a suspension and observing the temperature at which the solids are completely dissolved. Above this temperature the solution is undersaturated. When again cooling this same solution, temperatures below that of saturation can be reached without the formation of any crystals. In this region the solution is called supersaturated. The difference between the concentration of the supersaturated solution, c, and the saturated concentration, c*, is the so-called absolute supersaturation, which is the driving force for the crystallization process: