392 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS centration plots were linear extra- polation to infinite dilution gave the ideal droplet diameters. As will be seen from the table, these agreed well with the calculated values, and ß indicate the general correctness of TAI• Loe 1 Volume of Oleic •---- Droplet Diameters, •. ----• Acid, Light- Cc. Calc. X-ray Scattering 0.75 363 480 330 1.00 280 300-350 285 1.50 201 185-235 210 2.00 164 125-190 165 3.16 120 100-125 107 the hypothesis. The diameters in the last column were derived as- suming that the paraffin chains of the soap form part of the scattering unit. If, as is possible, they do not, calculations must be made without the monolayer, and 50 A. added to the result. If this is done, the re- sults are: 365, 295, 220, 155, 128 A., also in good agreement with the calculated values. If the two sets of experimental values are used to derive the thickness of the mono- layer, a value of 22 A. is obtained. Of course, the fa•t that the lowest concentration that could be investi- gated was about 10 per cent lays the accuracy of the extrapolation open to criticism, but it seems to be justi- fied by the results. We have also examined the system benzene - water - cetyltrime thylam- monium bromide-chloroform, which forms dispersions completely anal- ogous to the others. However, interpretation of the results must be made on a different basis, be- cause the area occupied per CTAB molecule could not be determined a priori. Again, x-ray and light- scattering results agreed, and in this case it proved possible to carry light-scattering measurements down to a concentration of 6 per cent. It will be seen that the area per CTAB molecule is found from the light-scattering results to be 3545 A.2, which is not much more than the area per molecule in a close- packed monolayer of CTAB (28-30 A?). This indicates that the area available for the chloroform is not more than about 18 A.2 The chloroform will alter the hydro- phobic-hydrophilic balance of the oil phase, and must be associated in some way with the positively charged nitrogen atoms of the soap. TASLE 2 Light- Area per Wt. of Scattering X-ray CTAB CTAB, Diameter, Spacing, Mole- Gm. A. A. cule, A? 1.50 320 369 45 2.25 280 Ca. 270 35 3.00 200 ... 40 REFERENCES (1) Schulman, J. H., and Rideal, E. K., _Proc. Roy. Soc., 122B, 29, 46 (1937). (2) Schu[man, J. H., and Stenhagen, E., Ibid., 126B, 356 (1938). (3) Marsden, J., and Schulman, J. H., Trans. Faraday Soc., 34, 748 (1938). (4) Cockbain, E.G., and Schulman, J. H., Ibid., 35, 1 (1938). (5) Schulman, J. H., and Hughes, A. H., Blochem. 7., 29, 1236, 1243 (1935). (6) Schulman, J. H., and Matalon, R., Faraday Sot., 43, 479 (1947)iH" (7) Matalon, R., Trans. and Schulman, J. ., Faraday Soc. Discussion "Lipoprotexns 6, 27 (1949). (8) Dory, P., and Schulman, J. H., fbid. 21. (9) Elkes, J. J., Frazer, A. C., Schulman,

•:,:-: ß PENETRATION AND COMPLEX-FORMATION IN MONOLAYERS 393 •g!3:: !': I. H., and Stewart, H. C., ]roe. Roy. Ross, S., and McBain, J. W, Ibid., 68, '?f•f• 7•oc., 184A, 102 (1945). 296 (1946). ß '(10) Schulman, J. H., and Cockbain, E.G., (17) Harkins, W. D., Mattoon, R. W., and ' :i•i:': ' I Trans. FaradaySoc.,36,651,661 (1940). Corrin, M. L., Ibid., 68, 220 (1946). ii$}ii:(l ) Alexander, A. E., and Schulman, J.H., Matloon, R. W., Stearns, R. S., and Ibid., 36, 960 (1940). Harkins, W. D., y. Chem. _Phys., 15, •)' '•i/!}.11:"i i2 ) Schulman, J. H., and Friend, J.A., 209 (1947). Harkins, W. D., and Mir- unpublished work. telman, R., y. Colloid Sci., 4, 367 (1949). :i•?!:(13) Schulman, J. H., and McRoberts, T.S., (18) Schulman, J. H., and Hoar, T. P., Na- • •: :. Tran. Faraday Sot., 42B, 165 (1946). Schulman, J. H., and Friend, J. A., un- (19) !?•ublished work. mess, K., and Gundermann, J., Ber., 70, (20) 1800 (1937). Hess, K., Kiessig, H., and Philippoff, W., Naturwiss., 26, 186 (21) (1938). Hess, K., and Kiessig, H., Chem. Bet., 81, 327 (1948). (22) McBain, J. W., and O'Connor, J.J., (23) .7..fro. Chem. Soc., 62, 2855 (1940). lure, 152, 102 (1943). Schulman, J. H., and Riley, D. P., y. Colloid Sci., 3, 383 (1948). Schulman, J. H., and Friend, J. A., Ibid., 4, 497 (1949). Matalon, R., and Schulman, J. H., y. Coil. Science, 4, 689 (1949). Matalon, R., unpublished. Wolstenholme, G. A., and Schulman, J. H., Trans. Faraday Soc. (in press). ::: ,