Sodium stearate

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]

Sodium stearate

Names
Preferred IUPAC name Sodium octadecanoate
Identifiers
CAS Number	822-16-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:132109 N
ChemSpider	12639 Y
ECHA InfoCard	100.011.354
EC Number	212-490-5
PubChem CID	2724691
UNII	QU7E2XA9TG Y
CompTox Dashboard (EPA)	DTXSID9027318
InChI 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 Y Key: RYYKJJJTJZKILX-UHFFFAOYSA-M Y 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
SMILES [Na+].[O-]C(=O)CCCCCCCCCCCCCCCCC
Properties
Chemical formula	C18H35NaO2
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 in water	soluble
Solubility	slightly soluble in ethanediol
Hazards
NFPA 704 (fire diamond)	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). N verify (what is YN ?) Infobox references

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]