Surfactant solubility in water increases with temperature increases gradually when it reaches a certain temperature, i.e., a sharp increase in the solubility, the solubility of which is called the critical temperature, expressed in tk. (T> tk-ionic surfactant is no longer a single ions, but the number of ions formed micelles).
When the surfactant solution when supersaturated, for critical solution temperature should be of the ionic surfactant monomer, micelles formed by a number of ions, surfactants solid undissolved coexistence triple point.