抄録
The Krafft points of some zwitter ionic or amphoteric surfactants have been measured in the presence and absence of inorganic salts. The zwitter ionic surfactants can be classified into two groups with respect to the Krafft point change upon the addition of salts. The Kraff t points of the surfactants in group I are depressed by added salts, whereas the surfactants in group II are not salted-in. It is found from the molecular structure of the zwitter ionic surfactants classified into group I and II that the distance between positive and negative charge of the surfactant molecule is the governing factor to distinguish between the salting-in type and the salting-out type of the surfactant. The zwitter ionic surfactants with the charge-charge distance longer than 0.40.5 nm may be salted-in, probably because the ions of the added salt can enter into the interior of the zwitter ions of the surfactant and interact electrostatically with them at the surface of the micelles.
