252 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS HLB values for a wide variety of surfactants have been calculated or observed and are listed in Table 1. As with any system that deals with surfactants, there are occasional side effects which seem to alter the estab- lished value. These are often unique to the test that is being run and there is no explanation for them at the present time. Because of the difficulty, time, and expense involved in carrying out the experimental procedure, relatively few of the host of available surfactants have had their HLB values determined. However, this is not the disad- vantage that it first appears to be, since a rough estimate of the HLB can be made from the degree of water solubility and in many instances this is adequate for screening work. In its present form, the HLB system lacks exactness. A suitable simple laboratory method of measuring HLB values of surfactants accurately is needed. We have tried a variety of methods including solubility in water, or various solvents, ratio solubility in two solvents, solubilization behavior both for oils and dyes, surface and interfacial tension data, cloud point behavior, and many other properties. Of these the most promising is the determination of the cloud point of an aqueous sol'ution of the surfactant. However, this test still possesses severe limitations. In addition to hydrophile-lipophile balance, it is believed that surfactants possess a second property which is related to their behavior. We call it chemical type. For example, we may find that esters of a particular fatty acid provide better emulsification in a given system than any other fatty acid esters or polyoxyalkylene fatty alcohols may give better performance than esters. In all probability, chemical type is related to the attraction of the lipophilic group in the surfactant for the lipophilic material with which the surfactant is being used. This, we believe, governs the efficiency of a surfactant, provided it is of the proper HLB. This second characteris- tic point, the nature of the hydrophilic and lipophilic groups, also requires further study. To select a surfactant properly for any application, we believe that one must first have the optimum HLB value and secondly have the correct chemical type. Since, at the moment we have correlation only for the HLB value our procedure is to establish the required HLB and then try a variety of chemical types at that optimum HLB. This procedure eliminates trial of all surfactants that are of the wrong HLB and, thus, reduces the time and effort required to solve a problem. Just as each surfactant or surfactant blend exhibits an HLB value each lipophilic material or blend of lipophilic materials with which surfactants are used exhibits an optimum required HLB value for any specific formula- tion or application, 'Fable 2. The determination of required HLB values has also been studied both from the standpoint of calculation and

HLB VALUES OF NON-IONIC SURFACTANTS 253 TAn•.E 1--CA•.CV•.ATEr) Ant) DETm•mn•r) HLB V^Lv•s Name Mfr.* Chemical Designation Typet HI,Bt•' Span 85 1 Arlacel 85 1 Atlas G-1706 1 Span 65 l Arlacel 65 1 Atlas G-1050 1 Eracol EO-50 2 Emcol ES-50 2 Atlas G-1704 1 Eracol PO-50 2 Atlas G-922 1 "Pure" 6 Atlas G-2158 1 Emcol PS-50 2 Emcol EL-50 2 Era col PP-50 2 Arlacel C 1 Arlacel 83 Atlas G-2859 1 Atmul 67 1 Atmul 84 1 Tegin 515 5 Aldo 33 4 "Pure" 6 Atlas G-1727 1 Emcol PM-50 2 Span 80 Arlacel 80 1 Atlas G-917 1 Atlas G-3851 1 Eracol PL-50 2 Span 60 Arlacel 60 1 Atlas G-2139 1 Emcol DO-50 2 Atlas G-2146 1 Emcol DS-50 2 Atlas G-1702 1 Emcol DP-50 2 Aldo 28 4 Tegin 5 Emcol DM-50 2 Atlas G-1725 1 Atlas G-2124 1 Emcol DL-50 2 Glaurin 4 Span 40 1 Ariaeel 40 1 Atlas G-2242 1 Atlas G-2147 1 Sorbitan trioleate N 1.8 Sorbitan trioleate N 1.8 Polyoxyethylene sorbitol beeswax derivative N 2 Sorbitan tristearate N 2.1 Sorbitan tristearate N 2.1 Polyoxyethylene sorbitol hexastea- rate N 2.6 Ethvlene glycol fatty acid ester N 2.7 Eth3, lene glycol fatty acid ester N 2.7 Polyoxyethylene sorbitol beeswax derivative N 3 Propylene glycol fatty acid ester N 3.4 Propylene glycol monostearate N 3.4 Propylene glycol monostearate N 3.4 Propylene glycol monostearate N 3.4 Propylene glycol fatty acid ester N 3.4 Ethylene glycol fatty acid ester N 3.6 Propylene glycol fatty acid ester N 3.7 Sorbitan sesquioleate N 3.7 Sorbitan sesquioleate N 3.7 Polyoxyethylene sorbitol 4.5 oleate N 3.7 Glycerol monosrearate N 3.8 Glycerol monostearate N 3.8 Glycerol monostearate N 3.8 Glycerol monostearate N 3.8 Glycerol monostearate N 3.8 Polyoxyethylene sorbitol beeswax derivative N 4 Propylene glycol fatty acid ester N 4.1 Sorbitan mono61eate N 4.3 Sorbitan mono61eate N 4.3 Propylene glycol monolaurate N 4.5 Propylene glycol monolaurate N 4.5 Propylene glycol fatty acid ester N 4.5 Sorbitan monostearate N 4.7 Sorbitan monostearate N 4.7 Diethylene glycol mono61eate N 4.7 Diethylene glycol fatty acid ester N 4.7 Diethylene glycol monostearate N 4.7 Diethylene glycol fatty acid ester N 4.7 Polyoxyethylene sorbitol beeswax derivative N 5 Diethylene glycol fatty acid ester N 5.1 Glycerol monostearate (self-emulsi- fying) A 5.5 Glycerol monostearate (self-emulsi- fying) A 5.5 Diethylene glycol fatty acid ester N 5.6 Polyoxyethylene sorbitol beeswax derivative N 6 Diethylene glycol monolaurate (soap free) N 6.1 Diethylene glycol fatty acid ester N 6.1 Diethylene glycol monolaurate (soap free) N 6.5 Sorbitan monopahnitate N 6.7 Sorbitan monopahnitate N 6.7 Polyoxyethylene dioleate N 7.5 Tetraethylene glycol monostearate N 7.7