Magnesium stearate is the chemical compound with the formula . It is a soap, consisting of

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

containing two equivalents of stearate (the anion of stearic acid) and one

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

cation (Mg²⁺). Magnesium stearate is a white, water-insoluble powder. Its applications exploit its softness, insolubility in many solvents, and low toxicity. It is used as a

release agent A release agent (also mold release agent, release coating, or mold release coating) is a chemical used to prevent other materials from bonding to surfaces. It can provide a solution in processes involving mold release, die-cast release, plastic r ...

and as a component or lubricant in the production of pharmaceuticals and cosmetics.Angelo Nora, Alfred Szczepanek, Gunther Koenen, "Metallic Soaps" in Ullmann's Encyclopedia of Industrial Chemistry 2005 Wiley-VCH, Weinheim.

Manufacturing

Magnesium stearate is produced by the reaction of

sodium stearate Sodium stearate is the sodium salt of stearic acid. This white solid is the most common soap. It is found in many types of solid deodorants, rubbers, latex paints, and inks. It is also a component of some food additives and food flavorings.Klaus ...

with magnesium salts or by treating magnesium oxide with stearic acid. Some nutritional supplements specify that the sodium stearate used in manufacturing magnesium stearate is produced from vegetable-derived stearic acid.

Uses

Magnesium stearate is often used as an anti-adherent in the manufacture of medical tablets, capsules and powders. In this regard, the substance is also useful because it has

lubricating Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology. Lubrication mechanisms such as fluid-lubrica ...

properties, preventing ingredients from sticking to manufacturing equipment during the compression of chemical powders into solid tablets; magnesium stearate is the most commonly used lubricant for tablets. However, it might cause lower wettability and slower disintegration of the tablets and slower and even lower dissolution of the drug. Magnesium stearate can also be used efficiently in dry coating processes. In the creation of pressed candies, magnesium stearate acts as a

and it is used to bind sugar in hard candies such as mints. Magnesium stearate is a common ingredient in baby formulas. In the EU and

EFTA The European Free Trade Association (EFTA) is a regional trade organization and free trade area consisting of four European states: Iceland, Liechtenstein, Norway and Switzerland. The organization operates in parallel with the European U ...

it is listed as food additive E470b.

Occurrence

Magnesium stearate is a major component of bathtub rings. When produced by soap and

hard water Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, which are largely made up of calcium and magnesium carbonates, bicarbo ...

, magnesium stearate and

calcium stearate Calcium stearate is a carboxylate salt of calcium, classified as a calcium soap. The salt is a component of some lubricants, surfactants, as well as many foodstuffs. It is a white waxy powder. Production and occurrence Calcium stearate is pro ...

both form a white solid insoluble in water, and are collectively known as

soap scum Soap scum or lime soap is the white solid composed of calcium stearate, magnesium stearate, and similar alkaline earth metal derivatives of fatty acids. These materials result from the addition of soap and other anionic surfactants to hard water. H ...

Safety

Magnesium stearate is generally considered safe for human consumption at levels below 2500 mg per kg of body weight per day and is classified in the United States as generally recognized as safe (GRAS). In 1979, the FDA's Subcommittee on GRAS Substances (SCOGS) reported, "There is no evidence in the available information on ... magnesium stearate ... that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when they are used at levels that are now current and in the manner now practiced, or which might reasonably be expected in the future."FDA's SCOGS Database
Report No. 60; ID Code: 557-04-0; Year: 1979

References

Excipients Magnesium compounds Stearates