DETERMINATION OF HLB 131 Figure 1. Titration with Neutronyx 640 and 626 ©, Lorol //5. © Left, before end point Center, at end point Right, after end point EXPERIMENTAL Ten per cent water solutions are made of the emulsifier under test, and also of an emulsifier with known HLB. The lower HLB surfactants ordinarily require a hydro-alcoholic solvent, but the alcohol content should be kept as low as possible. Water solutions are preferred, even if they are cloudy, as long as they are stable. Ten milliliters of the higher-HLB solution are added to a 100-ml grad- uated cylinder. About 0.1 g carbon black* is added, and the cylinder is shaken to wet out and disperse the pigment. Water is added to total about 80 ml. Ten grams of the selected oil phase is added and the con- tainer is shaken gently to mix the contents without generating a great deal of foam. The low-HLB solution is added in increments from a burette. Unless one can estimate in advance the probable titrant vol- ume and thus approach it rapidly, it is well to start with 1-ml additions, shaking after each, then allowing the phases to separate. The end point is taken as an apparently even division of black between the two phases. Figure 1 shows such a titration. The oil phase is lauryl alco- holt and the two surfactants used are ethoxylated nonyl phenols, Neu- tronyx //640 and //626, with emulsifying HLB's of 15 and 10.7, respec- tively. The center cylinder shows the end point at the calculated mix- * Carbon Black, Vulcan #9 ©, Godfrey L. Cabot Co., 125 High St., Boston, Mass. ,+ Lorol #5, © E. I. dupont de Nemours & Co., Wilmington, Del.

132 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 16 14 12 I I I I IHLB I (Tran, 'sfer) 2 4 6 8 10 12 14 16, Figure 2. Correlation of transfer or titration end point HLB with o/w emulsification HLB requirement: 1. Lorol #b ©, 2. Butyl Myristate, and 3. Klearol© mineral oil ture HLB of 12.66. On the left is a titration with 0.5 ml less titrant, and on the right, with 0.5 ml more. This is a fine example of the precision of the method when carefully performed, since despite the great visible dif- ferences, the HLB's are, from left to right, 12.70, 12.66, and 12.62, as cal- culated from the known quantities of the two emulsifiers used, and their known HLB values. Similar titrations utilizing the same Neutronyx, with mineral oil* as the oil phase, gave a value of 3.6 for the end point. Butyl myristate showed an end point at 6. CALCULATIONS The published HLB requirements for the emulsification of lauryl al- cohol or mineral oil into water are 14 and 10, respectively (9). The same reference includes the HLB requirement of 11 for butyl myristate. When these emulsification values were compared with the values shown by our carbon black migration end points, a straight-line relationship, graphically, was found (Fig. 2). The line-locus is y = 0.45x -[- 8.3 y * Klearol©, Sonneborn Division (Witco Chemical Co.), 277 Park Ave., New York, N.Y.