Ionic surfactants capable of being used in hard water

The mechanism behind the influence of multi-valent ions on the solubility of ionic surfactants in hard water is explained. It is possible to synthesize suitable surfactants for detergency proceeding from the physical meaning of the Krafft point. The Krafft point is the term for the temperature above which the solubility of a surfactant in water suddenly increases due to formation of micelles. Below the Krafft temperature the solubility is so small that the surfactant is useless for practical application. For that reason the Krafft point for a particular surfactant should lie below the temperature for the intended application. By understanding the mechanism it is possible to manufacture ionic surfactants suitable for practical application such as for use in hard-water detergency, in tertiary oil recovery and so on.