310 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS each day sees higher standards. Improved methods of deodorizing find ready acceptance and soon be- come necessities. The deodorant manufacturer has found a rapidly expanding demand and market for products which are simple to use and effective in practice. The public has learned the priceless value in the use of deodorants. The cosmetic chemist is contrib- uting generously to our social life by removing that offensive barrier of smell which throughout the ages has been holding people apart.
CLASSIFICATION OF SURFACE-ACTIVE AGENTS BY "HLB"t By Wx•,•,x• C. G•,•FFx•r ,/it/as Powder Company,//Filmington, Del. SINCE rH•. •NXUODtrCX•ON of the "HLB" system of classifying and selecting emulsifiers (6) numer- ous requests have been received concerning its derivation. The term "HLB" comes from the words hydrophile-lipophile balance. Emul- sifiers consist of a molecule that combines both hydrophilic and li- pophilic groups (or polar and non- polar groups) and it is the balance of the size and strength of these two opposing groups that we call HLB. Surface-active agents have been classified in many ways: including chemical types and according to ionization. Classification by HLB permits some prediction of behavior and reduces the amount of work in- volved in the selection of an emulsi- fier, wetting agent, or other type of agent. Emulsifiers constitute one of the widest used subdivisions of surface- active agents and we will use this group as an illustration of the manip- ulation of the HLB system, with reference to other applications later. )Presented at the October i '1, 1949, Meeting, Chicago Chapter, Chicago, I11. A complete system for selecting an emulsifier would provide the best emulsifier to give the desired form of product for the desired raw ma- terials. Thus, knowing the materi- als to be emulsified, the most ef- ficient emulsifier could be chosen for the desired type of emulsion. AcTioN ov EMtrzsiviZl•S An emulsifier has two actions that are distinctly different. The accepted action is that of promoting the formation of an emulsion mak- ing the emulsion easier to. prepare producing a finer particle size and aiding the stability of the emulsion. The second action, which occurs along with the preparation of the emulsion, consists in controlling the type of emulsion that is to be formed, O/W or W/O. This second action appears to be a function of HLB. In evolving a system for the selec- tion of emulsifiers, we will first con- sider briefly the theory of emu}sifica- tion. For practical purposes, an emulsion consists of two immiscible liquids, one being dispersed as a multitude of small particles in the 311
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