(Ph Eur)
DEFINITION
Mixture consisting mainly of stearic (octadecanoic) acid (C18H36O2; Mr 284.5) and palmitic
(hexadecanoic) acid (C16H32O2; Mr 256.4) obtained from fats or oils of vegetable or animal
origin.
Content:
Stearic acid 50: Stearic acid: 40% to 60%. Sum of contents of stearic and palmic acid minimum minimum 90%
Stearic acid 70: Stearic acid: 60% to 80%. Sum of contents of stearic and palmic acid minimum minimum 90%
Stearic acid 95: Stearic acid: >90%. Sum of contents of stearic and palmic acid minimum minimum 96%
CHARACTERS
Appearance: White or almost white, waxy, flaky crystals, white or almost white hard masses, or white or yellowish-white powder.
Solubility: Practically insoluble in water, soluble in ethanol (96 per cent) and in light petroleum (bp: 50-70 °C).
IDENTIFICATION
A. Freezing point (see Tests).
B. Acid value: 194 to 212, determined on 0.5 g.
C. Examine the chromatograms obtained in the assay.
Results The principal peaks in the chromatogram obtained with the test solution are similar in
retention time to those in the chromatogram obtained with the reference solution.
TESTS
Appearance: Heat the substance to be examined to about 75 °C. The resulting liquid is not more intensely coloured than reference solution.
Acidity: Melt 5.0 g, shake for 2 min with 10 mL of hot carbon dioxide-free water, cool slowly and filter.
To the filtrate add 0.05 mL of methyl orange solution R. No red colour develops.
Iodine value:
Stearic acid 50: I. V. = maximum 4
Stearic acid 70: I. V. = minimum 4
Stearic acid 95: I. V. = minimum 1.5
Freezing point:
Stearic acid 50: 53-59
Stearic acid 70: 57-64
Stearic acid 95: 64-69
Nickel: Maximum 1 ppm.
Octadecanoic acid.
Stearic acid [57-11-4].
Stearic Acid is manufactured from fats and oils derived from edible sources and is a mixture of Stearic Acid (C18H36O2) and palmitic acid (C16H32O2). The content of C18H36O2 is not less than 40.0 percent, and the sum of the two is not less than 90.0 percent.
NOTE: Stearic Acid labeled solely for external use is exempt from the requirement that it be prepared from edible sources.
Iodine value: not more than 4.
Residue on ignition: not more than 4 mg, determined on a 4-g portion (0.1%).
Heavy metals: 0.001%.
Mineral acid: Shake 5 g of melted Stearic Acid with an equal volume of hot water for 2 minutes, cool, and filter: the filtrate is not reddened by the addition of 1 drop of methyl orange.
Neutral fat or paraffin: Add 1 g of Stearic Acid to 30 mL of anhydrous sodium carbonate solution (1 in 60) in a flask, and boil the mixture: the resulting solution, while hot, shows not more than a faint opalescence.
Organic volatile impurities: meets the requirements.
Octadecanoic Acid
C18H36O2 Formula wt 284.48
CAS: [57-11-4]
DESCRIPTION
Stearic Acid occurs as a hard, white or faintly yellow, somewhat glossy and crystalline solid or as a white or yellowwhite powder. It is a mixture of solid organic acids obtained from fats consisting chiefly of Stearic Acid (C18H36O2) and palmitic acid (C16H32O2). Stearic Acid is practically insoluble in water. One gram dissolves in about 20 mL of alcohol, in 2 mL of chloroform, and in about 3 mL of ether.
REQUIREMENTS
Acid Value: Between 196 and 211.
Iodine Value: Not more than 7.
Lead: Not more than 2 mg/kg.
Residue on Ignition: Not more than 0.1%.
Saponification Value: Between 197 and 212.
Titer (Solidification Point): Between 54.5° and 69°.
Unsaponifiable Matter: Not more than 1.5%.
Water: Not more than 0.2%.
