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.[1]

Sodium stearate
IUPAC name
sodium octadecanoate
Other names
sodium octadecanoate
3D model (JSmol)
ECHA InfoCard 100.011.354
EC Number
  • 212-490-5
Molar mass 306.466 g·mol−1
Appearance white solid
Odor slight, tallow-like odor
Density 1.02 g/cm3
Melting point 245 to 255 °C (473 to 491 °F; 518 to 528 K)
Solubility slightly soluble in ethanediol
NFPA 704 (fire diamond)
Flash point 176 °C (349 °F; 449 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references


Characteristic of soaps, sodium stearate has both hydrophilic and hydrophobic parts, the carboxylate and the long hydrocarbon chain, respectively. These two chemically different components induce the formation of micelles, which present the hydrophilic heads outwards and their hydrophobic (hydrocarbon) tails inwards, providing a lipophilic environment for hydrophobic compounds. The tail part dissolves the grease (or) dirt and forms the micelle. It is also used in the pharmaceutical industry as a surfactant to aid the solubility of hydrophobic compounds in the production of various mouth foams.


Sodium stearate is produced as a major component of soap upon saponification of oils and fats. The percentage of the sodium stearate depends on the ingredient fats. Tallow is especially high in stearic acid content (as the triglyceride), whereas most fats only contain a few percent. The idealized equation for the formation of sodium stearate from stearin (the triglyceride of stearic acid) follows:

(C18H35O2)3C3H5 + 3 NaOH → C3H5(OH)3 + 3 C18H35O2Na

Purified sodium stearate can be made by neutralizing stearic acid with sodium hydroxide.


  1. Klaus Schumann, Kurt Siekmann, "Soaps" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a24_247
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