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For other uses, see Soap (disambiguation).
A collection of decorative soaps, often found in hotels
Two equivalent images of the chemical structure of sodium stearate, a typical soap. In chemistry, soap is a salt of a fatty acid. Soaps are mainly used as surfactants for washing, bathing, and cleaning, but they are also used in textile spinning and are important components of lubricants. Soaps for cleansing are obtained by treating vegetable or animal oils and fats with a strongly alkaline solution. Fats and oils are composed of triglycerides; three molecules of fatty acids are attached to a single molecule of glycerol. The alkaline solution, which is often called lye, (although the term "lye soap" refers almost exclusively to soaps made with sodium hydroxide) brings about a chemical reaction known as saponification. In saponification, the fats are first hydrolyzed into free fatty acids, which then combine with the alkali to form crude soap. Glycerol (glycerine) is liberated and is either left in or washed out and recovered as a useful byproduct, depending on the process employed. Soaps are key components of most lubricating greases, which are usually emulsions of calcium soap or lithium soaps and mineral oil. These calcium- and lithium-based greases are widely used. Many other metallic soaps are also useful, including those of aluminium, sodium, and mixtures of them. Such soaps are also used as thickeners to increase the viscosity of oils. In ancient times, lubricating greases were made by the addition of lime to olive oil.
|Contents | |1 Mechanism of cleansing soaps | |1.1 Accumulation of dust on fabrics | |1.2 Action of soap | |1.3 Effect of the alkali | |1.4 Effects of fats | |2 History of cleansing soaps | |2.1 Early history | |2.2 Roman history | |2.3 Islamic history | |2.4 Medieval history | |2.5 15th–19th centuries | |3 Liquid soap | |4 Soap-making processes | |4.1 Cold process | |4.1.1 Hot processes | |4.1.2 Molds | |4.2 Purification and finishing | |5 See also | |6 References | |7 Further reading | |8 External links |
Mechanism of cleansing soaps
Structure of a micelle, a cell-like structure formed by the aggregation of soap subunits (such as sodium stearate): The exterior of the micelle is hydrophilic (attracted to water) and the interior is lipophilic (attracted to oils).
Accumulation of dust on fabrics
When we wear clothes and as a result of our physical movement, frictional force is applied to the cloth surface and the cloth fibres become charged. This is so because during the moving process, either electrons from the cloth shift to our body or some electrons get shifted from our body to the clothes. In either case,...