Absorption of sodium lauryl sulphate at the benzene-water interface

Summary The interfacial tension of benzene-water interface was measured as a function of sodium lauryl sulphate concentration in presence of 0, 0,1 and 1 M sodium chloride. Analysis of pressure-area curves constructed from these data indicated qualitatively the validity of the onekT and twokT forms of theGibbs equation respectively for the presence and absence of neutral salt. The proposed dimerisation of lauryl sulphate ions in the bulk was shown not to affect the- A curves to a large extent in the high pressure region. The limiting area per adsorbed ion was evaluated from an empirical plot. The experimental pressure was found to deviate significantly from that expected theoretically from theGouy model of the electrical double layer. This deviation was explained on the basis of the discrete-ion-effect proposed byBell, Levine andPethica.Based in part, upon the thesis submittedby A. K. Chatterjee (Chattopadhyay) for Ph. D. degree of the Jadavpur University, 1966.The authors are grateful to Dr.G. M. Bell and Dr.B. A. Pethica for the interpretation of several points of their theory in a private communication. Thanks are also due to the Council of Scientific and Industrial Research. India for the financial assistance.