Products
Magnesium stearate is available as a pure substance in pharmacies. It is found as an excipient in many medicines and especially in tablets. Calcium stearate is also used more rarely.
Structure and properties
Magnesium stearate is a hydrophobic compound of magnesium and a mixture of solid organic acids, mainly consisting of varying proportions of magnesium stearate and magnesium palmitate of plant or animal origin. In a narrower sense, magnesium stearate (Mg(C18H35O2)2, Mr = 591.3 g/mol) a salt consisting of a magnesium ion (Mg2+) and two stearates. A stearate is a salt of stearic acid, a C18 fatty acid. Magnesium stearate exists as a white, very fine, light powder that is greasy to the touch. It is practically insoluble in water.
Effects
Magnesium stearate is very commonly used as a lubricant. It improves lubricity by reducing friction and adhesion. Magnesium stearate prevents powder from sticking to machinery during manufacturing – for example, to the punch during tableting.
Areas of application
Magnesium stearate is used as a pharmaceutical excipient for tablet, capsule and powder production, among other applications.
