J. Soc. Cosmetic Chemists, 19, 129-136 (Feb. 5, 1968) A Titration Method for Determination of the HLB's of Emulsifiers the JAMES J. MIDDLETON, B.A., M.B.A.* Presented May •, 1967, New York City Synopsis--A titration method for determining HLB's, particularly of emulsifiers, is pre- sented. This is a color-migration procedure, similar to the Epton method for determining anionics or cationits. Parameters of variables are discussed, especially as to the control of errors and their magnitude for any one variation. Application to the determination of the HLB requirements of mixed-oil phases is also discussed. INTRODUCTION The HLB concept (hydrophile-lipophile balance of a nonionic emulsifier) was introduced by Griffin (1). It has since been refined and extended by Griffin, Carter, and their group (2, 3), and summarized by Griffin (4). The practical value of the system to technical people in the cosmetic, detergent, and emulsion fields has been amply demonstrated. This system provides a unifying method which embraces several families of surfactants, and divides the effort required to select the most effective agent to use in a particular project. The HLB of an emulsifier is a number which expresses the ratio be- tween water-soluble groups and oil-soluble groups in the molecule. The higher the HLB number, the more water-directed is the entire molecule. Surfactants of a given chemical type can be arranged in a series, starting with the most oil-directed and advancing to the most water-directed as * Millmaster-Onyx Corp., Onyx Chemical Co. Div., 190 Warren Street, Jersey City, N. J. 07302. 129

130 JOURNAL OF THE SOCIETY OF COSMETIC CHEM1STS the numbers increase. Such series include the Span ©* and Tween ©* group and the Neutronyx©• surfactants. There are, of course, other tradename series too numerous to list here. Several authors have reported attempts to relate HLB to various other properties of the surfactant molecules (5-8). At present, how- ever, the most direct method, which at the same time includes factors in addition to the HLB itself, is actually to make a set of emulsions, using the desired oil phase, and varying the HLB throughout the set in a regu- lar manner. HLB values intermediate between those of commercial products can be achieved by mere mixing of these products. For ex- ample, blending 70% Tween 80 (HLB of 15) and 30% Span 80 (HLB of 4.3) (0.70 X 15) + (0.30 X 4.3) = 11.8, HLB of the blend. Thus, a higher-HLB emulsifier is mixed with a lower-HLB emulsifier in such pro- portions that the average HLB's of the several mixtures as calculated show a regular variation. The emulsions in the series are then com- pleted, and their stabilities are observed. The most stable ones cluster around a particular HLB range. Then, another set of emulsions is made, to range more compactly around this HLB stability-peak and sub- divide the values more finely than in the first set. This narrowing down process can be carried out further until an almost infinitesimal range is covered but there is a practical limit of refinement left to the judg- ment of the chemist. It is perfectly proper to speak of the HLB of a nonsurfactant, such as mineral oil. In this sense, we refer to the HLB required by the mineral oil to become emulsified, even though the oil itself has no duality of both oil- and water-solubility. In fact, mineral oil requires an HLB of 10 to become emulsified in water, and an HLB of 1.8 to form a water-in-oil system. The author has found that, for preliminary screening, a rapid titra- tion procedure is highly useful. Briefly, a water solution of the higher- HLB material is titrated with a solution of the lower-HLB material, in the presence of the oil phase. An indicator is used, the most dependable found so far being a carbon black. At the end point, the carbon mi- grates from the water phase into the oil, with high visibility. Under the experimental conditions detailed below, emulsification of the oil does not occur at the end point, and the phase separation is rapid. The crucial effect seems to be on the carbon black itself rather than on the oil phase, although this is still somewhat conjectural. * Atlas Chemical Industries, Inc., Wilmington, Del. t Onyx Chemical Co., Jersey City, N.J.