Sodium stearate

Last updated
Sodium stearate
Stearic Acid Sodium Salt Structural Formula V.2.svg
Names
Preferred IUPAC name
Sodium octadecanoate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.011.354 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 212-490-5
PubChem CID
UNII
  • InChI=1S/C18H36O2.Na/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20;/h2-17H2,1H3,(H,19,20);/q;+1/p-1 Yes check.svgY
    Key: RYYKJJJTJZKILX-UHFFFAOYSA-M Yes check.svgY
  • InChI=1/C18H36O2.Na/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20;/h2-17H2,1H3,(H,19,20);/q;+1/p-1
    Key: RYYKJJJTJZKILX-REWHXWOFAA
  • [Na+].[O-]C(=O)CCCCCCCCCCCCCCCCC
Properties
C18H35NaO2
Molar mass 306.466 g·mol−1
Appearancewhite 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)
soluble
Solubility slightly soluble in ethanediol
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
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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Sodium stearate (IUPAC: Sodium Octadecanoate) 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]

Contents

Use

Having the characteristics of soaps, sodium stearate has both hydrophilic and hydrophobic parts, a carboxylate and a long hydrocarbon chain. 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.

Production

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:

(C17H35CO2)3C3H5 + 3 NaOH → C3H5(OH)3 + 3 C17H35CO2Na

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

C17H35COOH + NaOH → C17H35COONa + H2O

Safety and environmental considerations

Stearate salts, as found in many commercial soaps are of low toxicity, hence their wide use in domestic settings. They do pose some problems for wastewater treatment as they biodegrade relatively slowly and impose a high biological oxygen demand. [1]

References

  1. 1 2 Schumann, Klaus; Siekmann, Kurt (2000). "Soaps". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a24_247. ISBN   978-3-527-30385-4.
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