Synthetic detergents are made up of molecules which concentrate at water-oil and water-air interfaces. By virtue of their tendency to thus concentrate they show, in varying degrees, wetting, foaming, emulsifying, dispersing and solubilizing properties. Detergency is a composite of these properties. A molecule of. a synthetic detergent consists of a nonpolar oil-soluble portion, a polar water-soluble portion, and a connecting linkage. A few years ago, natural fats and oils furnished the nonpolar hydrocarbon chains for most synthetic detergents. Thus coconut oil, reduced to fatty alcohols, was converted to sodium lauryl sulfate, or, without reduction, to sodium lauric acid monoglyceride sulfate. Fatty acids were reacted with ethylene oxide to form polyoxyethylene esters which served as nonionic detergents. In recent years, petroleum-based synthetic detergents have become increasingly important. They furnish more detergent power in terms of cost than do the fat-based detergents. In view of the worldwide shortage of fats and oils and increasing demand for those as food, the fat-based detergents will probably fade in relative importance for economic reasons. In the United States the petroleum-derived alkyl aryl sulfonates are the most popular type of general purpose detergent. Though excellent cleaning and foaming agents, they have certain disadvantages, notably hygroscopicity which leads to caking, and tendency to leave the skin sticky and, later, harsh. Hence sulfated detergents hold their markets for some applications, for instance shampooing. In Britain, secondary alcohol sulfates derived from petroleum are popular, but they are inferior in quality to fatty alcohol sulfates. Non-ionic detergents, although still not sold in enormous quantities, are expanding rapidly and may rival the alkyl aryl sulfonates. The most promising ones appear to be the alkyl aryl polyoxyethylene ethers, which are made from three basic raw materials, all derived from petroleum. Development of a normal straight-chain C12 to C14 sulfate made synthetically from non-fat materials at low cost would revolutionize the synthetic detergent industry. This is a clear challenge to petroleum chemists. © 1951 Energy Institute. All rights reserved.