Sodium stearate (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

: Sodium Octadecanoate) is the

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

stearic acid Stearic acid ( , ) is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a soft waxy solid with the formula . The triglyceride derived from three molecules of stearic acid is called stearin. Stearic acid ...

. This white solid is the most common

soap Soap is a salt (chemistry), salt of a fatty acid (sometimes other carboxylic acids) used for cleaning and lubricating products as well as other applications. In a domestic setting, soaps, specifically "toilet soaps", are surfactants usually u ...

. It is found in many types of solid

deodorant A deodorant is a substance applied to the body to prevent or mask body odor caused by bacterial breakdown of perspiration, for example in the armpits, groin, or feet. A subclass of deodorants, called antiperspirants, prevents sweating itself, t ...

s, rubbers, latex paints, and inks. It is also a component of some

food additives Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke (smoking) and sugar (crystallization), have been used for ...

and food flavorings.Klaus Schumann, Kurt Siekmann, "Soaps" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2005, Wiley-VCH, Weinheim. Sodium stearate powder

Use

Having the characteristics of

s, sodium stearate has both

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are n ...

and

hydrophobic In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thu ...

parts, a

carboxylate In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an anion, an ion with negative charge. Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,... ...

and a long hydrocarbon chain. These two chemically different components induce the formation of

micelle A micelle () or micella () ( or micellae, respectively) is an aggregate (or supramolecular assembly) of surfactant amphipathic lipid molecules dispersed in a liquid, forming a colloidal suspension (also known as associated colloidal system). ...

s, 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 Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word ''surfactant'' is a Blend word, blend of "surface-active agent", coined in ...

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 Saponification is a process of cleaving esters into carboxylate salts and Alcohol (chemistry), alcohols by the action of aqueous alkali. Typically aqueous sodium hydroxide solutions are used. It is an important type of alkaline hydrolysis. When the ...

of oils and fats. The percentage of the sodium stearate depends on the ingredient fats.

Tallow Tallow is a rendered form of beef or mutton suet, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton suet. In this context, tallow is animal fat that conforms to certain technical criteria, inc ...

is especially high in stearic acid content (as the

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

), 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

with sodium hydroxide. : C₁₇H₃₅COOH+NaOH→C₁₇H₃₅COONa+H₂O

Applications

Sodium stearate is used in :

1. Soap and Detergents

Sodium stearate is best known as the main ingredient in bar soapmain ingredient in bar soap. It serves as a cleansing agent by emulsifying oils and suspending dirt so it can be rinsed away. It's the backbone of traditional soap-making, dating back centuries. In solid soaps, sodium stearate provides: * Cleansing power * Hardness (makes the bar solid) * Mildness to skin (relative to synthetic detergents)

2. Deodorants and Antiperspirants

In deodorant sticks, sodium stearate acts as a gel-forming agent. It thickens and stabilizes the stick, giving it that smooth, glide-on texture while keeping the formulation intact.

3. Cosmetics

Sodium stearate appears in: * Creams * Lotions * Makeup products It works as a: * Co-emulsifier (helps mix oil and water) * Thickening agent * Stabilizer for emulsions

4. Industrial Uses

* Used as a lubricant in plastic and rubber manufacturing * Acts as a release agent in molding operations * Can function as a dispersing agent or gelling agent in wax-based systems

Biological and Environmental Impact

Safety Safety is the state of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk. Meanings The word 'safety' entered the English language in the 1 ...
and
Toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...

Sodium stearate is generally recognized as safe (GRAS) by the FDA for use in food contact and cosmetics. It is considered non-toxic, non-carcinogenic, and non-irritating in typical concentrations used in consumer products. In powdered form, however, inhalation should be avoided as with any fine particulate. It can cause temporary respiratory irritation.

Biodegradability

As a salt of a naturally occurring fatty acid, sodium stearate is readily biodegradable under environmental conditions. It breaks down into

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

, and

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

salts, posing minimal ecological risk when used in typical quantities.

References

External links

Safety Data
{{Stearates Organic sodium salts Stearates Soaps Anionic surfactants