Dissolution (chemistry)

Dissolution

Dissolution is the process by which a solid or liquid forms a homogeneous mixture with a solvent (solution). This can be explained simply as a breakdown of the crystal lattice into individual ions, atoms or molecules.

Dissolution testing is widely used in the pharmaceutical industry for optimization of formulation and quality control.

Ionic Compounds

For ionic compounds, dissolution takes place when the component ions dissociate into its component parts. This normally occurs in polar solvents, such as Water or Ammonia.
NaCl_(s) → Na⁺_(aq) + Cl^-_(aq)

In a colloidal dispersed system, ion dissolution arises, where the dispersed particles exist in equilibrium with their saturated counter part, i.e.

NaCl_(s) → Na⁺_(aq) + Cl^-_(aq)

The behavior of this system is characterised by the components activity coefficients and solubility product, i.e.

$a_{Na^{+}}\cdot a_{Cl^{-}}=K_{sp}$

The ability of an ion to preferentially dissolve (as a result of unequal activities) is classified as the Potential Determining Ion. This in turn results in the remaining particle possessing either a net positive/negative surface charge.<br /

Polar Compounds

Other compounds experience dissolution simply as a breakdown of their crystal lattice, and due to their polarity, or non-polarity, mix perfectly with the solvent.

See also

• Solvation