324 JOURNAL OF T•IE SOCIETY OF COSMETIC CHEMISTS .., '•-• ß ß H H ]man . • • • JlaL •,) q, II ,+ -- Figure &--Example HLB use emulsions, alLpurpose cream (Top Row) Preliminary determination of required HLB of oil phase. (Middle Row) Final estimation of required HLB, value 10.4. (Bottom Row) Comparison of various chemical types, all at same HLB Figure 7.--Effect of polyol on all-purpose cream (Top Row.) Various amounts of Arlex. (Bottom Rozo) Various polyols. mum point, the chemical classifica- tion for the emulsifier is studied by preparing a third test series, as in the third row, in which emulsifiers of selected different chemical types are tried, all of which have been previously blended to the required HLB. After choosing the chemical type, a final series usually suffices to provide a blend of emulsifiers of the chosen chemical type at the most favorable HLB and at the minimum required total concen- tration. This last series of samples is usually put through more exten- sive and more stringent stability tests. If the required HLB of the oil phase is known approximately, the first series of tests may be elimi- nated. If it is known with greater accuracy, both the first and second 'series of tests may be omitted. For an example, an All-Purpose Cream has been chosen with a pro- posed formula of: Beeswax ...................... 5 Mineral Oil .................... 26 Hydrogenareal Vegetable Oil ..... 18 Polyol ........................ 4 Emulsifier ..................... 5-10 Water, q. s. to make ............ 100 The oil phase, then consists of the following approximate percentages. Oil or Wax Beeswax Mineral Oil Hydrogenareal vege- table oil Average estimated required HLB Esti- mated Re- quired % X % HLB HLB 10 15 1.5 53 10 5.3 37 9 3.3 10.1 Calculation of an estimated re- quired HLB gives a value slightly over 10. Therefore, the initial series with this oil phase can be pre- pared combining Span 60 and Tween 60 to give HLB values close to 10, as in the second row, Fig. 6. Span 60-Tween 60 Calculated HLB 50-50 9.8 45-55 10.3 40-60 10.8 35 --65 11.3 25-75 12.4

CLASSIFICATION OF SURFACE-ACTIVE AGENTS 325 The best ratio in this series is 45% Span 60 and 55% Tween 60 at a calculated HLB of 10.3. The evaluation of different chemi- cal types of emulsifiers is then con- sidered as previously mentioned. For this example, the stearate blend is the best chemical type. Usually it will be desirable to cover a much wider range of alternate chemical types than the space limitation per- mitted us in the third row of Fig. 6. It must be remembered that all blends must be at the correct HLB. It is interesting to note that the addition of polyol to the aqueous phase of an emulsion such as was just studied does not appear to alter the HLB appreciably. The samples in the top row of Fig. 7 show the effect of adding various amounts of commercial sorbitol sirup. The per- centages are the amount of Adex* in the total formula, not the amount in the aqueous phase. Therefore, for the fourth sample the aqueous phase contains approximately 40% polyol which is a sizable proportion. In the second row, three different polyols are employed. Little dif- ference is noted in the emulsifica- tion, regardless of the type of polyol used. This does not imply that the three polyols will produce similar cosmetic effects. These differences are well known and are due to the variations in hygroscopicities, co- solubilities, and other physical prop- erties of the polyols themselves. The data indicate that at the proper balance of emulsifier, the emulsifi- cation will not be appreciably fected by the type and amount of polyol. The dividing line between in- gredients and emulsifie•:s is often not clear. Stearic acid, lanolin, cholesterol, and beeswax are just a few examples of materials that may serve a dual role. An example of this is in soap-emulsified-facial- creams in which the stearic acid is partially neutralized. In this, the stearic acid forms a bulk of the oil phase, but portions of the stearic acid are present as emulsifier, both neutralized and as free acid. By examining a system, it is usually possible to evaluate each ingredient in the terms of its uses. APPLICATIONS OTHER THAN EMUL- SI FICATION (1) Atntifoaming Antifoaming is quite a specific action, therefore it is surprising when most of the Atlas agents that have found success as antifoam agents fall in the range of 1.5-3 and all are less than 8. No complete study of this subject, as with emulsi- fiers, has been made or is contem- plated. (2) PI"etting and Spreading Atlas wetting and spreading agents fall in the rather narrow HLB range of 7 to 9. We have frequently tried products outside this range, but with little success, particularly when the values were greater than 9. Wetting is usually desired in an aqueous solution, suspension, or O/W emulsion, and this is probably the cause of the narrow effective