ylikyllästymiseen

Ylikyllästyminen, known in English as supersaturation, is a thermodynamic phenomenon where a solution contains more dissolved solute than it would normally be able to hold at a given temperature and pressure. This state is unstable, and the excess solute is poised to precipitate out of the solution, often triggered by a slight disturbance.

Supersaturated solutions are typically prepared by dissolving a solute in a solvent at an elevated temperature, where solubility is higher. As the solution cools slowly and without agitation, it can remain in a supersaturated state. If the solution is then cooled too rapidly or subjected to mechanical shock, such as stirring or the introduction of a seed crystal, the excess solute will rapidly crystallize or precipitate out of the solution until it reaches its equilibrium saturation point.

This principle is applied in various industrial processes, including the crystallization of sugars, salts, and pharmaceuticals. It's also observed in everyday phenomena like the rapid hardening of certain candy products or the formation of crystals in cooling beverages. The instability of supersaturated solutions makes them useful for controlled crystallization and the production of pure crystalline solids.