Detergents, term applied to materials, the solutions of which aid in the removal of dirt or other foreign matter from contaminated surfaces. Until the 1940s soap was the only important detergent. Today soap is but one of a great many detergent products. The ingredients of detergents are often called surface-active agents, or surfactants, because they act upon a surface. A common feature of detergents is that they are made up of comparatively large molecules (molecular weight over 200). One part of the molecule is soluble in organic material, and the other part is soluble in water.
During World War II the shortage of fats, from which soap is made, spurred the development of soapless or synthetic detergents, primarily in the United States. After the war the need for new types of detergents for automatic washing machines accelerated the trend.
Detergents are made by treating an aromatic, or benzene-type, compound with sulfuric acid, followed by neutralization with alkali to convert the product to its sodium salt. The detergent products of these reactions came into wide use in the late 1940s and early '50s and proved to be effective in hard water and cool or cold water, whereas soap is often wholly ineffective under both conditions. These detergents, however, became a public nuisance because, unlike soaps, they were neither soluble nor biodegradable; that is, once put into water they tended to remain there, resisting conversion into less complex and more soluble substances. The detergents tended to create foam in cesspools and in sewage-disposal plants as well. They even appeared in naturally occurring ground and surface waters.
Replacing the aromatic compound with a so-called linear alkyl-type compound in the process described above led to a more desirable product. It was as effective as the former kind in its detergent action but was more biodegradable and soluble. The new linear alkylate sulfonate is changed to harmless products by microorganisms in cesspools,...