Stearic Acid
INCI: Stearic Acid
CAS # 57-11-4
EC # 200-313-4
Synonyms: Estearina. Acetylacetic acid. Stearophaneic acid.
Molecular Formula: C18H36O2 (pure stearic acid)
Molecular Weight: 284.48
Description: Mixture of palmitic (hexadecanoic) and stearic (octadecanoic) acids in various proportions, usually of origin
Vegetable oil (palm oil).
Physical and Chemical Data: Small white or almost white spheres and / or white or yellow-white powder.
Practically insoluble in water, soluble in 96% ethanol, and light petroleum ether (bp 50-70 ° C).
Melting point: 69-70 ° C.
Properties and uses:
Stearic acid possesses emollient and protective properties, which prevents the drying of the corneous layer of the skin, and is easily absorbed through it.
It is used as an emulsifier for the formation of base creams, sometimes used as evanescent emulsions, partially neutralized with an alkali (mainly triethanolamine).
The free stearic acid in these creams produces a pearled appearance. Stearic acid creams may appear cracked by desiccation or with lumps, due to their reactions with zinc or calcium salts.
It is used similarly to white wax for ointments and ceratos.
It is also used as a lubricant in the manufacture of tablets and capsules, and as an enteric coating for gastro-resistant pills and tablets.
Finally it has application as a hardening agent in suppositories.
Dosage:
As an emulsifier in ointments and creams: 1 - 20%.
As a lubricant: 1 - 3%.
Incompatibilities: Bases in general, metal hydroxides, oxidizing agents, and reducing agents.
Storage: In tightly closed containers. PROTECTING THE LIGHT
Observations:
- Stearic acid has emollient and surfactant properties for the skin.
- It is odorless and serves to create light-colored soaps.
- Adjusts the pH of the soap and produces hard soap bars.
- Because of its proprietary emulsion it is used to make creams and soaps.
- It is used as a substitute for palm oil.
