Abstract: The concentration (c)-voltage (V) relations of K~+ and Ca~(2+) in surfactant solutions have been measured by ionic selective electrodes. The results show that it is very easy to form ion-pair, for alkyl sulfate(RS)and metallic cations which is the reason why the eletrolyte tolerance of RS is very low; The situation between the polyoxyethylene group in alkylpolyox yethylene ether sulfate salts (RE_nS) and multivalent metallic cations (Mn~(n+)) may be considered as the interaction performed by complexation, which prevents RE_nS and M~(n+) to form ion-pair, and this is one of the reasons why RE_nS have a higher eletrolyte tolerance.

Key words: Surfactant, Alkylpolyoxyethylene ether sulfate, Metallic ionsurfactant interaction