Solubility equilibrium

The solubility equilibrium (also: solubility equilibrium ) describes the dynamic equilibrium between soil body and a saturated solution.

For saturated solutions can be shown directly by a few examples, that in equilibrium a constant mass transfer takes place, so that particles of the soil body go into solution, but also that particles from the solution into the soil body pass ( crystallization). So there is a dynamic equilibrium in which the dissolution rate is equal to the rate of crystallization. Sediment and saturated solution form a heterogeneous system.

With the help of the principle of the smallest constraint, one can predict how the solubility equilibrium depends on the temperature:

• Runs the solution process is exothermic, so the solubility decreases with increasing temperature.
• Is the solution process is endothermic, so the solubility to increase in temperature.

The solubility equilibrium can be disturbed by substances which react with the solute (for example: the addition of hydronium ions to the solution of a hydroxide ). There then arises a new equilibrium.