Solubility of Solids in Liquid Solvents

If a solid with an amorphous or crystalline structure is dissolved in a large excess of solvent, the dilute solution gives one homogeneous phase. If more solid is added to the diluted solution, up to the point where the solid can no longer be dissolved, the solution is saturated or at solubility equilibrium. The maximum solubility or the maximum capacity of the solvent to dissolve the solid has then been reached. 

The solubility of the substance to be dissolved in the solvent depends on the temperature, molar amount of solvent in the crystals, and hence the form of the crystals the dependenee on pressure is only minor. For the same crystal form, solubility usually increases with a higher temperature. If the molar volume of the solid decreases during 

In Fig. 1-39, cooling a solution from point A down to the solubility curve SC, causes crystallization to take place (the case of over solubility will be discussed later). The mass fraction of solvent in the solution thus increases because of partial crystallization of the dissolved solid. During the cooling process, the change of state of the solution moves along the solubility curve SC until the eutectic point E is reached, the solution then freezes completely. 

If a solution is cooled from B, then the solvent freezes when the ice curve IC is reached. The dissolved substance becomes enriched (the concentration of the solution is increased because the fraction of solvent 

II 1 vo phase region, solution, and solvent as the bottom layer 

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