Products
Stearic acid is available as a pure substance in pharmacies and drugstores. The name “stear” comes from the Greek and means tallow or lard, so it shows the origin of the substance.
Structure and properties
Stearic acid or octadecanoic acid (C18H36O2, Mr = 284.5 g/mol) is a saturated and unbranched C18 fatty acid, i.e., a fatty acid with 18 carbon atoms. Its salts, for example magnesium stearate, calcium stearate and sodium stearate, are called stearates. This also applies to the esters. The prefix is stearyl-, e.g. stearyl alcohol. The European Pharmacopoeia defines stearic acid as a mixture of fatty acids that contains palmitic acid in addition to stearic acid. The substance exists as white, waxy, flaky crystals, hard masses or as a white to yellowish white powder and is practically insoluble in water. The melting point is in the range of 50 to 70 °C, and the density is lower than that of water. Stearic acid is a natural fatty acid found in many vegetable and animal fats (e.g. butter, lard) and fatty oils in the form of triglycerides and is obtained by saponification. High concentrations are found, for example, in coconut oil and shea butter. Animal fats usually contain larger proportions.
Fields of application
Stearic acid is used as an excipient in the manufacture of liquid, semisolid and solid pharmaceuticals, as well as in cosmetics and skin care products. It is also used as a food additive.
