|University Federico II
of Naples, Italy
Think of adding some teaspoons of the common salt (sodium chloride) to a glass of water: you will observe that, at first, the salt will dissolve completely. When a well defined number of additions is reached, more added salt will not dissolve any further, and the excess salt makes a deposit on the bottom of the glass.
Addition of a solid to a given volume of a liquid. When solution becomes saturated, further addition will cause precipitation of the solute
So, observation leads us to the conclusion that a maximum amount of a substance exists that dissolves in a given volume of solvent. When this point is reached, solution is saturated. Solubility is just defined as the concentration of the saturated solution. Solubility can vary greatly, and it can take very low or very high values depending on the properties of the substance under examination and on the interactions that it forms with the solvent. Solubility depends on the temperature, too. As a consequence, when solubility values of a substance in a given solvent are reported, it is necessary to specify at what temperature experiments were carried out.