Saturation

Etymology

Latin saturatus, past participle of saturare, from satur well-fed

• Date: 1538

Definitions

• 1 : to satisfy fully : satiate
• 2 : to treat, furnish, or charge with something to the point where no more can be absorbed, dissolved, or retained <water saturated with salt>
• 3 a : to fill completely with something that permeates or pervades <book is saturated with Hollywood — Newgate Callendar>

b : to load to capacity

• 4 : to cause to combine until there is no further tendency to combine

Description

In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of it will appear as a precipitate. This point of maximum concentration, the saturation point, depends on the temperature of the liquid as well as the chemical nature of the substances involved. This can be used in the process of recrystallisation to purify a chemical: it is dissolved to the point of saturation in hot solvent, then as the solvent cools and the solubility decreases, excess solute precipitates. Impurities, being present in much lower concentration, do not saturate the solvent and so remain dissolved in the liquid. If a change in conditions (e.g. cooling) means that the concentration is actually higher than the saturation point, the solution has become supersaturated.