Calcium Stearate
Octadecanoic acid, calcium salt;
Calcium stearate
[1592-23-0].
(kal' see um steer' ate).
Octadecanoic acid, calcium salt;
Calcium stearate
[1592-23-0].DEFINITION
Calcium Stearate is a compound of calcium with a mixture of solid organic acids obtained from fats. It consists chiefly of variable proportions of calcium stearate and calcium palmitate. It contains the equivalent of NLT 9.0% and NMT 10.5% of calcium oxide (CaO).
IDENTIFICATION
• A. Identification Tests—General, Calcium 
191
191
Sample:
1 g
Analysis:
Heat the Sample with a mixture of 25 mL of water and 5 mL of hydrochloric acid.
Acceptance criteria:
Fatty acids are liberated and appear as an oily layer floating on the surface of the liquid. The water layer meets the requirements.
• B.
Sample:
25 g
Analysis:
Mix the Sample with 200 mL of hot water, add 60 mL of 2 N sulfuric acid, and heat the mixture, with frequent stirring, until the separated fatty acid layer is clear. Wash the fatty acids with boiling water until free from sulfate, collect them in a small beaker, and warm on a steam bath until the water has separated and the fatty acids are clear. Allow the acids to cool, pour off the water layer, and melt the acids. Filter into a dry beaker, and dry at 105
for 20 min.
for 20 min.
Acceptance criteria:
The fatty acids so obtained congeal at a temperature NLT 54 (see Congealing Temperature 651).
(see Congealing Temperature 651).
ASSAY
• Procedure
Sample:
1.2 g
Titrimetric system
(See Titrimetry 541.)
541.)
Mode:
Direct titration
Titrant:
0.05 M edetate disodium VS
Endpoint detection:
Colorimetric
Analysis:
Boil the Sample with 50 mL of 1 N sulfuric acid for about 3 h using a watch glass cover to avoid splattering, or until the separated fatty acid layer is clear, adding water if necessary, to maintain the original volume. [Note—Stirring may be helpful in obtaining a clear layer and decreasing extraction time. ] Cool, filter, and wash the filter and the flask thoroughly with water until the last washing is not acid to litmus. Neutralize the filtrate with 1 N sodium hydroxide to litmus. While stirring, preferably with a magnetic stirrer, titrate with 0.05 M edetate disodium VS as follows. Add about 30 mL from a 50-mL buret, then add 15 mL of 1 N sodium hydroxide and 300 mg of hydroxy naphthol blue. Continue the titration to a blue endpoint. Each mL of 0.05 M edetate disodium is equivalent to 2.804 mg of calcium oxide (CaO).
Acceptance criteria:
9.0%–10.5%
IMPURITIES
• Heavy Metals 231
231
Test preparation:
Place 2.5 g of Calcium Stearate in a porcelain dish, and add 5 mL of a 1-in-4 solution of magnesium nitrate in alcohol. Cover the dish with a 7.5-cm, short-stem funnel so that the stem is straight up. Heat on a hot plate at low heat for 30 min, then heat at medium heat for 30 min, and cool. Remove the funnel, and heat the dish over a suitable burner until most of the carbon is burned off. Cool, add 10 mL of nitric acid, and transfer the solution into a 250-mL beaker. Add 5 mL of 70% perchloric acid, cautiously evaporate to dryness, add 2 mL of hydrochloric acid to the residue, and wash down the inside of the beaker with water. Evaporate carefully to dryness again, swirling near the dry point to avoid spattering. Repeat the hydrochloric acid treatment, then cool, and dissolve the residue in about 10 mL of water. Add 1 drop of phenolphthalein TS and add sodium hydroxide TS until the solution just turns pink. Then add 3 N hydrochloric acid until the solution become colorless. Add 1 mL of 1 N acetic acid and a small amount of charcoal, and pass through filter paper into 50-mL color-comparison tubes. Wash with water, and dilute with water to 40 mL.
Monitor preparation:
Place 500 mg of Calcium Stearate in a porcelain dish, and add 5 mL of a 1-in-4 solution of magnesium nitrate in alcohol. Cover the dish with a 7.5-cm, short-stem funnel so that the stem is straight up. Heat on a hot plate at low heat for 30 min, then heat at medium heat for 30 min, and cool. Remove the funnel, add 2 mL of Standard Lead Solution (20 µg of Pb), and heat the dish over a suitable burner until most of the carbon is burned off. Cool, add 10 mL of nitric acid, and transfer the solution into a 250-mL beaker. Add 5 mL of 70% perchloric acid, cautiously evaporate to dryness, add 2 mL of hydrochloric acid to the residue, and wash down the inside of the beaker with water. Evaporate carefully to dryness again, swirling near the dry point to avoid spattering. Repeat the hydrochloric acid treatment, then cool, and dissolve the residue in about 10 mL of water. Add 1 drop of phenolphthalein TS and add sodium hydroxide TS until the solution just turns pink. Then add 3 N hydrochloric acid until the solution become colorless. Add 1 mL of 1 N acetic acid and a small amount of charcoal, and pass through filter paper into 50-mL color-comparison tubes. Wash with water, and dilute with water to 40 mL.
Analysis:
Add 1.2 mL of thioacetamide–glycerin base TS and 2 mL of pH 3.5 acetate buffer to each tube. Allow to stand for 5 min.
Acceptance criteria:
The color of the Test preparation does not exceed that of the Monitor preparation (NMT 10 ppm).
SPECIFIC TESTS
• Loss on Drying 731:
Dry a sample at 105 to constant weight, using 2-h increments of heating: it loses NMT 4.0% of its weight.
731:
Dry a sample at 105 to constant weight, using 2-h increments of heating: it loses NMT 4.0% of its weight.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Robert H. Lafaver, M.S.
Scientific Liaison 1-301-816-8335 |
(EXC2010) Monographs - Excipients |
USP35–NF30 Page 1724