Epitochem

Stearic Acid

Stearic Acid

Stearic acid is a white or faintly yellow, crystalline solid or powder with a slight tallow-like odor and taste. It is a saturated fatty acid commonly used in pharmaceutical, cosmetic, and food products. The substance is derived from both animal and vegetable fats and consists mainly of stearic acid and palmitic acid. Commercial grades are defined by their stearic acid content, such as stearic acid 50, 70, or 95.

Chemical Name and CAS Registry Number :-Octadecanoic acid [57-11-4]
Functional Category :-Emulsifying agent; solubilizing agent; tablet and capsule lubricant.

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Pharmacopeial Specifications

Test JP PhEur USPNF
Acidity – ✔ –
Acid value 194–210 194–212 –
Appearance – ✔ –
Characters – ✔ –
Stearic acid content – 50: 40–60%
70: 60–80%
95: ≥90%		 ≥40%
Stearic + Palmitic acids – ≥90% ≥90%
Congealing temp. (°C) 56.0–72.0 – ≥54
Freezing point (°C) ✔ 50: 53–59
70: 57–64
95: 64–69		 –
Iodine value ≤4.0 ✔ ≤4.0
Nickel – ≤1 ppm –
Residue on ignition ≤0.1% – ≤0.1%
Heavy metals ≤20 ppm – ≤0.001%
Neutral fat/paraffin ✔ – ✔
Mineral acid ✔ – ✔
Org. volatile impurities – – ✔

Applications in Pharmaceutical Formulation or Technology

Used in oral formulations as a lubricant (1–3%) and binder. In topical forms, it acts as an emulsifying and solubilizing agent. When neutralized with alkalis or triethanolamine, it forms cream bases. Also used as a hardening agent in glycerin suppositories and widely used in cosmetics and food.

Comment

Various commercial grades exist with different physical properties based on stearic/palmitic acid ratio. The EINECS number is 200-313-4. The USPNF has separate monographs for standard and purified grades.

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