ABSTRACT
The desire for cleanliness and other cosmetic benefits (fragrance, beauty, skin care) has been part of the human condition since early written history. Modem cleansers are based on fats, oils, and their derivatives, which have been utilized for cleansing in various forms for over two millennia (Fig. 1). Soap, generally defined as the alkali salt of a fatty acid, is a member of the general class of compounds called surfactants (surface-active agents). These molecules are characterized by having a hydrophilic head group and a hydrophobic 308tail. Synthetic detergents (or syndets) are another class of surfactant with similar structure and mechanisms of soil removal. However other key properties—for example, lather, bar feel, and sensitivity to water hardness—can be quite different.
