Magnesium stearate

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Magnesium stearate

Systematic name	Magnesium stearate
Chemical formula	C₃₆H₇₀MgO4
Molecular mass	591.27 g/mol
Melting point	88 °C
Boiling point	? °C
CAS number	[557-04-0]
SMILES	CCCCCCCCCCCCCCCCCC(=O)[O-]. CCCCCCCCCCCCCCCCCC(=O)[O-].[Mg+2]
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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 also a common ingredient in baby powders. In pure powder form, the substance can be a dust explosion hazard, although this issue is effectively moot 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.