DETERMINATION OF HLB 135 saturated solution. HLB's of these mixtures titrated with increasing accuracy as the content of petrolatum was increased. EFFECTS OF OTHER FACTORS The effects of added electrolyte, alcohol, and increased temperature are of minor influence when relatively small changes are made in these parameters. Above certain levels, the effects become so large that the author has not yet been able to measure them completely with accept- able accuracy. Up to 1% electrolyte in the titration is tolerable, whether acetic acid, sodium or potassium chloride, or aluminum salts, so long as no chemical reaction occurs in the system. Up to about 10% alcohol, ei- ther ethyl or isopropyl, can also be accommodated. Temperatures to 35 øC induce little change. Above this, titration HLB's rise rapidly (considerably more of the low HLB titrant must be added) and duplica- tion of results becomes difficult. The fact that these three factors change the HLB of a system is of great interest. Those who develop emulsion products are aware that any one of these can destroy an otherwise elegant formulation. It is therefore suggested that titrations be performed after including the elec- trolyte or alcohol in the water phase. This may ease later efforts to as- sure stability. As to temperature, stable emulsions have been found to separate after oven storage. The change of HLB requirement reported here may be a sufficient explanation, although not a remedy. Possibly supplying an HLB intermediate between the two may offer stability at both oven and room-temperature conditions. These three factors most likely operate by changing the hydration of the ethylene oxide chains, thereby altering the micelle structure and critical micelie concentration of the system. The method has other built-in bonuses, which can be used with in- genuity to solve many difficult cases, sometimes almost accidentally. The author had occasion recently to emulsify a very dark colored oily material. Obviously, a prior determination of the HLB was desirable. While dubious that any darkening of the oil from the carbon migration would be observable, the titration was tried anyway. To observe the darkening was, indeed, hopeless. But, rewardingly, at one point the water phase suddenly became almost white as the carbon transferred into the oil, not only demonstrating the end point, but also greatly relieving one anxious chemist. The HLB determined was, actually, quite cor-

136 JOURNA L OF THE SOCIETY OF COSMETIC CHEMISTS rect, as shown by the stable emulsions later compounded using the con- verted O/W HLB. This titration method, while probably not foolproof, is a convenient and easy means for rapidly developing information to prepare specific emulsion formulations. The choice of emulsifiers is quickly narrowed down, and the application range of a new emulsifier is quickly deter- mined. In the hands of a skilled chemist, many of its shortcomings can be avoided, and the procedure probably can be improved into greater usefulness as experience with it grows. (Received May 19, 1967) REFERENCES (1) Griffin, W. C., Classification of surface-active agents by "HLB," J. Soc. Cosmetic Chem~ ists, 1,311-26 (1949). (2) Griffin, W. C., Calculation of HLB Values of non-ionic surfactants, Ibid., 5, 249-55 (1954). (3) Griffin, W. C., Clues to surfactant selection offered by the HLB System, Q/•/c. Dig., Federation Paint &• Varnish Production Clubs, 28, 466-75 (1956). (4) Griffin, W. C., Emulsification, in Sagarin, E., Cosmetics: Science and Technology, Inter- science Publishers, New York, N.Y., 1957, pp. 998-1033. (5) Becher, P., The effect of the nature of the emulsifying agent on emulsion inversion, J. Soc. Cosmetic Chemists, 9, 141-8 (1958). (6) Ross, S., Chen, E. S., Becher, P., and Ranuto, H. J., Spreading coefficients and hydro- phile-lipophile balance of aqueous solutions of emulsifying agents, J. Phys. Chem., 63, 1681-3 (1959). (7) Becher, P., Spreading, HLB, and emulsion stability, J. Soc. Cosmetic Chemists, 11, 325- 32 (1960). (8) Greenwald, H. L., Brown, G. L., and Fineman, M. N., Determination of the hydrophile- lipophile character of surface-active agents and oils by a water titration, Anal. Chem., 28, 1693-7 (1956). (9) Atlas Chemical Industries, Inc., The Atlas HLB System, pamphlet, 1963.