Abstract

Soap is the oldest surface active preparation known to humanity and its use for cleaning has been reported since Roman times. Soap itself is comprised of a family of simple surfactants which are alkaline salts of fatty acids; a typical example being sodium dodecanoate, ie, CH₃(CH₂)₁₀COO^–Na⁺. The principle raw materials for preparation of soap are animal and vegetable oils/fats which are traditionally converted into soap employing alkaline saponification reactions. In global terms even today, bulk of the soap is used for cleaning and hygiene purposes and it is produced in the bar form, although liquid or gel form soap preparations have also become popular recently, in some parts of the world. The traditional fat/oil saponification process also continues to be used for manufacture of soap even now; however it is rapidly being substituted by novel fat splitting followed by fat neutralization processes. The original frame-cooling operation for converting the soap mass into a bar has been replaced by novel extrusion forming or moulding operations. Most of the early improvements and variations in soap formulation were brought about leveraging availability of a wide range of oils/fats, and development of new processes eg, hydrogenation, bleaching etc, to make them suitable for soap-making. However, more recently soap bars, gels and liquids incorporating non-soapy synthetic surfactants and functional ingredients, are being developed and marketed for offering novel benefits and superior performances to consumers. Apart from its use as a cleaning/hygiene agent, soap has also found many industrial applications such as a wetting agent, as an emulsifier or as a lubricant.