Abstract: The interaction between C₁₄BE and NaCMC has been studied by using the surface tension method.In the neutral water solution, the effect of NaCMC on the surface activity of C₁₄BE is weak, but with the addition of NaCl, two transition points appeared on the surface tension-concentration curve.This indicated that a water soluble C₁₄BE/NaCMC complex was formed by hydrophobic effect. In the solution of pH=2,the existence of two transition points also indicated the formation of C₁₄BE/NaCMC complex because of hydrogen-binding.It is the advantage for zwitterionic surfactant that the effect of electrolyte on it is weaker compared with that of its ionic surfactant.

Key words: Surface activity, Tetradecyl betaine(C₁₄BE), Sodium carboxymethyl cellulose (NaCMC), Critical micelle concentration(cmc).