설명(영) |
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Soaps are the salts of water-insoluble Fatty Acids with various bases. Soaps were the first surface-active agents prepared by man.
Soaps are subdivided into water-soluble and water-insoluble types. The former are the salts of fatty acids with ammonia, low molecular weight Amines, especially Alkanolamines, and alkali metals, especially sodium and potassium. Water-insoluble fatty acid salts result from reaction with metallic cations, such as zinc and aluminum, alkaline earths such as calcium and magnesium, and long-chain fatty amines.
The water-soluble salts of fatty acids, derived from alkaline hydrolysis (saponification) of plant or animal Fats and Oils, are used widely as skin cleansers (in bar form and the like) and in laundry and other cleaning applications. In cosmetics, such soaps are used as emulsifiers, in shaving products, and occasionally in shampoos. These soaps are also commonly used for gelling hydro-alcoholic sticks, such as deodorants. As a rule, water-soluble soaps in cosmetics are formed in situ by reaction of the fatty acid(s) with the desired alkali. Some soap bars are still produced by the classic kettle soap process via alkaline saponification of fats and oils.
The water-insoluble soaps are used as binders and fillers in loose and compressed powders, as hydrophobic solids in skin applications and as lubricants in pharmaceutical tablet manufacture. Metallic soaps are commonly used as emulsion stabilizers in w/o emulsions, and occasionally employed in drugs and cosmetics to thicken or gel hydrocarbons. |