Krafft Point and Related Technical Terms

Another term, the critical solution temperature (CST), was introduced to designate the temperature beyond which the solubility of nonionic surfactants in organic solvents increases markedly, as marked by an inflection in the solubility curve. Mazer and Benedek used the critical micellar temperature (CMT) to refer to the phase boundary between a hydrated solid phase and a micellar phase. The CMT value was taken as the midpoint of the temperature range over which the hydrated solid phase clarified on slow warming with vigorous shaking. 

As can be seen, concepts of the Krafft point fall ito two different categories those involving a phase transition of solid surfactant and those involving a solubility increase up to the CMC. The two views are incompatible according to the former, the Krafft point is a definite temperature (a point), whereas according to the latter, it is a narrow temperature range. This conflict is addressed in the following sections. 

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