Soap

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In chemistry, soap is a salt of a fatty acid.[1] Soap is mainly used for washing and cleaning, but soaps are also important components of lubricants. Soaps for cleansing are obtained by treating vegetable or animal oils and fats with a strongly alkaline solution. The alkaline solution, often lye, promotes what is known as saponification. In saponification, fats are broken down (hydrolyzed) yielding crude soap, i.e. impure salts of fatty acids, with glycerol as a byproduct

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Soaps for lubrication greases

Soaps are key components of most lubrication greases, which are usually emulsions of calcium and lithium soaps in a mineral oil. Lithium-based greases are particularly important. Many other metal ions are used, including aluminium, sodium, and mixtures of various metal ions. Such soaps are sometimes classified as thickeners, meaning that they elevate the viscosity of the oil. In ancient times, lubricating greases were prepared by the addition of lime to olive oil.[2]

Mechanism of cleansing soaps

When used for cleaning, soap serves as a surfactant in conjunction with water. The cleaning action of this mixture is attributed to the action of micelles, tiny spheres coated on the outside with polar carboxylate groups, encasing a hydrophobic (lipophilic) pocket that can surround the grease particles, allowing them to dissolve in water. The hydrophobic portion is made up of the long hydrocarbon chain from the fatty acid. In other words, whereas normally oil and water do not mix, the addition of soap allows oils to dissolve in water, allowing them to be rinsed away. Synthetic detergents operate by similar mechanisms to soap.

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