JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS way insolubilised and fixed in it during retraction. This effect is one of the most important features of dilute solutions of foaming agents. In these solutions, although the dynamic and the static surface tensions are very high, stable foam columns may be obtained as a result of the compression of originally unstable lamin•e. Indeed, a• the foam column rises, mechanical changes are established, and lamime of initially large surface areas are Figure 6 (above) ß An example ol • irreversible behaviour on retraction. Figure 7 (below): Reversibility on traction and retraction exhibited with sodium aleate. (See page 223:) 224 (Continued on next page)

'?i'::Figure 8. Variation o• mersoloce •oam volume :: •::• retracted and stab•l•se8 by the higher :• •'sudace concentration then reached. ?/•:•'Tract•on and •etract•on at high ?speeds have shown that' • •or a given •:'' solute the •oam volume increases as .. ':•: Dy decreases. •aximum foaming ß ?•' is observed when Dv • 0. Yurther •:•: increase in concentration above the ß :•" optimum results •n decrease •of ' loanting, due to a slowing down of the •: rate of adsorption. Yigure 8 demon- strates clearly the •erso]ate foam volume as a of Dy. • CONCLUSION The study of foaming, using direct and indirect methods, has been reviewed. The wire frame technique FOAM FORMATION AND FOAM STABILITY adapted for' that study has been described in detail. Various factors controlling foam formation and foam stability, i.e., the rate of adsorption in the surface layer and the-rate of desorption on compression of the lamina, have been followed, using the traction and retraction curves. Drainage of the interlamellar liquid and stability of the thinned laminse may be easily followed on the trac- tion curves. Stabilisation of the lamin•e on compression was demon- strated on the retraction curves and it is concluded that foaming agents tend to stabilise the lamina during the retraction process. REFERENCES • D.G. Dervichian. 1944. Corps Gras Savons, Vol. 2, No. 6, p. 164. 2 j. Plateau. 1873. "Statique experi- mentale et th•mique des liquides soumis aux seules forces moleculaires." a R. ]E. Wilson and E. D. Ries. 1923. Coil. Symp. Monograph, p. 161. 4 •. O. Clark. 1947. Chem. Research Special Report I%. 161. Dept. of Scienti- fic and Industrial Research. 5 E. J. Burcik. 1950. J. Colloid Science, 5, 421. 6 R. Matalon. "Surface Chemistry," Butterworth, pp. 195-201. ? Lenard et al. 1924. Ann. der Physzk, 74, pp. 381-404. 8 R. Matalon. 1948. Memorial Services chirniques etat, 84, 345-351. 9 R. Matalon. 1948. 15th June Dr. Ing. thesis, Lyon. x0 R. Matalon. 1951. The Journal of the Society of Cosmetic Chemists, II, No. 3, p. 122. n Unpublished work. •a M. Raison, R. Matalon. 1948. Memorial Services chimiques etat, 84, pp. 353-371. 225