Saturated solution

Saturated solution is a solution that does not change its concentration in contact with the solute under certain thermodynamic conditions (pressure, temperature). In practice, this means that no precipitate is formed without the change of the thermodynamic conditions from the saturated solution, but no more precipitates can be dissolved in it.

In the saturated solution in contact with the dissolved substance, there is a dynamic equilibrium, in that the rate of dissolution and precipitation is exactly the same.

Liquid saturated solution is obtained in laboratories usually by gradually adding the dissolved substance until the next portion of the solution is dissolved. The saturated solution can also be obtained by changing the thermodynamic conditions (eg, lowering the temperature until the initial precipitation is observed) or by slow evaporation of the solvent.

Regardless of how the solution is obtained, the saturated solution under the given thermodynamic conditions always has the same concentration. This concentration is called the solubility of the substance. Information on these concentrations is collected in a variety of databases and physicochemical guides. Using a variety of techniques that slow down or block the crystallization process, such as very slow cooling of a perfectly clean solution, it is possible to obtain a supersaturated solution, ie one which has a higher concentration than the saturated solution. The supersaturated solutions are very unstable and upon receipt from the environment of any crystallization impulse such as a small crystalline drop or a slight shake, the excess of the substance is precipitated rapidly until the saturated solution is reached.

wiki