saltsolubility

Salt solubility is the maximum amount of a salt that can dissolve in a solvent at a given temperature to form a saturated solution. It is commonly expressed as grams of solute per 100 grams of solvent or as molarity. For many salts, solubility is described by an equilibrium in which the solid dissolves to yield its constituent ions.

For sparingly soluble salts, the solubility product constant (Ksp) characterizes dissolution: AB(s) ⇌ A+(aq) + B−(aq); Ksp = [A+][B−]. The solubility of such salts depends on temperature; many become more soluble with higher temperature, though the exact trend is determined by the enthalpy of dissolution and the lattice energy.

Several factors influence salt solubility. Lattice energy and hydration energy determine whether dissolution is favorable. Temperature is a key variable, and pH can affect solubility for salts of weak acids or bases by shifting equilibria. The common ion effect—adding an ion that is already present in the dissolution products—reduces solubility. For gases, solubility is strongly affected by pressure, but this effect is negligible for most solid salts in liquid water.

Solubility is measured and often represented by solubility curves that show how solubility changes with temperature. Practical implications include natural water chemistry, precipitation and scaling in industrial systems, and pharmaceutical formulation, where achieving and maintaining a desired solubility is important for efficacy and stability.