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Magnesium stearate

Magnesium stearate
IUPAC name Magnesium octadecanoate
CAS number 557-04-0
PubChem 11177
Molecular formula C36H70MgO4
Molar mass 591.27 g/mol
Melting point

88 °C

Boiling point


MSDS External MSDS
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Magnesium stearate, also called octadecanoic acid, magnesium salt, is a white substance which is solid at room temperature. It has the chemical formula C36H70MgO4. It is a salt containing two equivalents of stearate (the anion of stearic acid) and one magnesium cation (Mg2+). Magnesium stearate melts at about 88 °C, is not soluble in water, and is generally considered safe for human consumption. Because it is widely regarded as harmless, it is often used as a filling agent in the manufacture of medical tablets and capsules. In this regard, the substance is also useful because it has lubricating properties, preventing ingredients from sticking to manufacturing equipment during the compression of chemical powders into solid tablets. It is used to bind sugar in hard candies. It is also a common ingredient in baby powders. In pure powder form, the substance can be a dust explosion hazard, although this issue is effectively insignificant beyond the manufacturing plants using it.

When used as a filling agent in the manufacture of capsules and tablets, such as vitamins, the source of this ingredient is typically beef. However, there is an increasing number of vegetarian options in which the product specifically indicates it contains magnesium stearate from vegetable sources.

Magnesium stearate is a major component of "bathtub rings".


    • International Chemical Safety Card 1403
    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Magnesium_stearate". A list of authors is available in Wikipedia.
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