322 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS PERCENTAGE OF "•B" 0 S I0 15 20 25 30 35 40 45 50 55 60 65 70 75 •0 85 90 95 I00 ATLAS HLB COMPUTOGRAPH 27 27 FOR COMBINATIONS OF SURFACE ACTIVE AGENTS 26 26 25 -- 25 24 24 2• 2• 22 • 22.• 2l 21" 2O 20 0 19 19 ../ { lB 18 O 16 -- 16 • ,40 ...I 15 15-TW[EN •0 14 14 13 -TWoeEN 21 12 12 II I-TWEEN •5 65 10 -- J . IO-'TWEEN B I 9 SPAN 20 -- - , 7 •-- 7 SPAN '-- - 6 SPAN 62 -- - 5 5 SPAN, -- - SPAN 4 4 SPAN 65- _-2: - z SPAN I 0 0 0 .5 I0 15 20 25 30 35 40 45 50 55 60 65 70 75 8,0 65 90 95 100 PERCENTAGE OF "B" SPAN• TWF...oeN: RE.•. U.S. PAT. OFF, emulsifier immensely. In the case of soaps, traces of multivalent ions completely change the HLB. An- other instance that we have ob- served was with an amine-neutral- ized aryl sulfate, where the presence of acidic constituents lowered the HLB of the emulsifier markedly. Likewise, in Table 6 we have listed the estimated required HLB values for several of the more com- monly used oils and waxes. These

CLASSIFICATION OF SURFACE-ACTIVE AGENTS 323 T. BL• 6 Oil or Wax Required HLB for o/w w/o Emulsion Emulsion Cottonseed Oil Carbontetrachloride ParafFin (household) . Microcrystalline wax (Micropac Q, S-V) Mineral Oil, White, light (Marcol GX) Mineral Oil, White, heavy (Nujol) Mineral Seal Oil Petrolatum, white (White Perrecta) Silicone Oil (G. E.) Kerosene Naphtha ß Cetyl Alcohol Orthodichlorobenzene •' Beeswax, white Carnauba Wax Candelilla Wax Lanolin, U.S. P., anhyd. Dimethyl Phthalate Or thophenylphenol Stearic Acid 9 9.5* io Io.5 Io.5' xo.5 Io.5' I3' I3 i3' io-i6 I4.5' i4.5' I5 i5' 17 * Tentative. •' Plus small amounts (3-5%) of pine oil and isopropyl alcohol. values are reported only in half- unit increments due to lack of pre- cision in measurement. However, the values are amply accurate for use with the HLB values for the enmlsifiers in a selection of an emulsifier combination. The oils and waxes are tabulated in ascend- ing order of required HEWs. As would be expected similar values are noted for like chemical types. METHOD OF USE OF HLB VALu•.s We have developed a "refined trial-and-error system" based on HLB values. In any emulsification problem one of two conditions can exist: (1) the problem can be to emulsify an oil phase of unknown composition, or (2) the approximate desired formula may be known in- cluding the composition of the oil phase. If the properties, particularly the required HLB, of the oil phase are unknown as in the first condition, a preliminary exploratory test is set up. This is usually done with a non-ionic emulsifier combination, such as Span 60 and Tween 60, of known HLB values. The first series of determinations are prepared with various ratios of these emulsifiers using a maximum amount of total emulsifier. Usu- ally a series, resembling those in the top row of Fig. 6, is obtained. It appears that the optimum HLB for this system is between samples 3 and 4. A more accurate determina- tion of the required HLB is next obtained by the preparation of a second series, using small increments of this same pair of emulsifiers as shown in the second row of tests. After determination of the opti-