Phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point.

A supersaturated solution generally crystallises when 'seed' crystals are introduced and rapid equilibration occurs. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its crystalline form or particle size. Under certain conditions, the equilibrium solubility can be exceeded to give a so-called supersaturated solution, which is metastable. One may also speak of solid solution, but rarely of solution in a gas (see vapor–liquid equilibrium instead). Most often, the solvent is a liquid, which can be a pure substance or a mixture. Insolubility is the inability to dissolve in a solid, liquid or gaseous solvent. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration, where adding more solute does not increase the concentration of the solution and begins to precipitate the excess amount of solute. The solubility of a substance fundamentally depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure and presence of other chemicals (including changes to the pH) of the solution. Solubility is the property of a solid, liquid or gaseous chemical substance called solute to dissolve in a solid, liquid or gaseous solvent. The solution was initially prepared at 20 ☌ and then stored for 2 days at 4 ☌. Formation of crystals in a 4.2 M ammonium sulfate solution.

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