Palmitic acid

• USP–NFPalmitic Acid

Hexadecanoic acid; cetylic acid; n-hexadecoic acid; 1-pentadecanecarboxylic acid

Hexadecanoic acid · [57-10-3]

UNII 2V16EO95H1 · PubChem CID 985

C16H32O2 · 256.42

Lubricant

Typical concentrations: — · Dosage forms: Solid

Used as a lubricant and as an emulsifying agent (after neutralisation to soaps) in topical and oral products, as a lipid component of solid lipid nanoparticles and other lipid carriers, and as a constituent of many fatty-acid mixtures, notably pharmacopoeial stearic acid. It is also used in cosmetics and foods.

Hard, white or faintly yellowish, slightly glossy crystalline solid, flakes or powder with a slight characteristic odour. It is the most common saturated fatty acid in animal and plant fats.

Melting point

about 60–63 °C (high-purity material ≈ 63 °C)

Acid value

≈ 219 (theoretical for the pure acid)

Solubility

practically insoluble in water; soluble in hot ethanol, ether and chloroform; slightly soluble in cold ethanol

pKa

≈ 4.8 (in dilute solution; apparent value in lipid assemblies is higher)

Stable; as a saturated fatty acid it is resistant to oxidation. Store in a well-closed container in a cool, dry place.

Incompatible with strong oxidising agents and bases (with which it forms soaps); it may react with basic drugs and with metal salts.

Obtained by hydrolysis of fats such as palm oil, followed by separation of the fatty acids by fractional distillation and/or crystallisation.

A normal dietary component; regarded as non-toxic and only mildly irritant at the levels used as an excipient.

Observe normal precautions for the quantity handled. Avoid generating dust; eye protection, gloves and a dust mask are recommended.

Described in the USP–NF. Fatty acids are permitted as food additives in the USA under specified conditions (21 CFR 172.860).

Stearic acid; myristic acid; cetyl palmitate; glyceryl palmitostearate; isopropyl palmitate.

Commercial palmitic acid is often supplied as blends with stearic acid; the ratio of the two acids affects melting behaviour and lubricant or emulsifying performance, so the grade composition should be specified.