The
solubility of a substance is a measure of the amount dissolving in a given volume of solution at a certain temperature. A solution of a solid that is in equilibrium with undissolved solid is said to be
saturated.
The solubility of an
ionic solid is related, through the balanced equation for dissolving, to the change in
concentration of the ions that are the products of the reaction.
CaF
2(
s)

Ca
2+(
aq) + 2F
–(
aq)
For slightly soluble solids the reaction is reactant-favoured, as shown by the equilibrium arrow.
Solubility varies with
temperature and may also depend on what other solutes are present.
The solubility of CaF2 in aqueous CaCl2 is different than it is in water at the same temperature.