Castor Oil
(kas' tor oyl).
DEFINITION
Castor Oil is the fixed oil obtained from the seed of Ricinus communis L. (Fam. Euphorbiaceae). It contains no added substances.
IMPURITIES
• Heavy Metals, Method II 231:
NMT 10 ppm
SPECIFIC TESTS
• Specific Gravity 841:
0.9570.961
• Distinction from Most Other Fixed Oils:
It is only partly soluble in solvent hexane (distinction from most other fixed oils), but it yields a clear liquid with an equal volume of alcohol (foreign fixed oils).
• Fats and Fixed Oils, Free Fatty Acids 401:
The free fatty acids in 10 g require NMT 3.5 mL of 0.10 N sodium hydroxide for neutralization.
• Fats and Fixed Oils, Hydroxyl Value 401
Free acid determination
Sample:
10 g
Titrimetric system
(See Titrimetry 541.)
Mode:
Direct titration
Titrant:
0.5 N alcoholic potassium hydroxide VS
Endpoint detection:
Visual
Analysis:
Transfer the Sample to a 250-mL conical flask, add 10 mL of pyridine that has been neutralized previously to phenolphthalein, and swirl to mix. Add 1 mL of phenolphthalein TS, and titrate with Titrant to a faint pink endpoint. Record the volume of Titrant consumed (VA).
Hydroxyl value determination
Sample:
2 g
Blank:
5.0 mL of a freshly prepared mixture of 1 volume of acetic anhydride and 3 volumes of pyridine
Titrimetric system
(See Titrimetry 541.)
Mode:
Residual titration
Titrant:
0.5 N alcoholic potassium hydroxide VS
Endpoint detection:
Visual
Analysis:
Transfer the Sample to a glass-stoppered, 250-mL conical flask. Add 5.0 mL of a freshly prepared mixture of 1 volume of acetic anhydride and 3 volumes of pyridine, and swirl to mix. Connect the flask to a reflux condenser, and heat on a steam bath for 2 h. Add 10 mL of water through the condenser, swirl to mix, heat on a steam bath for an additional 10 min, and allow to cool to room temperature. Add through the condenser 15 mL of normal butyl alcohol that has been neutralized previously to phenolphthalein, remove the condenser, and wash the tip of the condenser and the sides of the flask with an additional 10 mL of neutralized normal butyl alcohol. Add 1 mL of phenolphthalein TS, and titrate with Titrant to a faint pink endpoint. Calculate the hydroxyl value in the portion of Oil taken:
Result = {[VB + (W × VA/WA) VT] × Mr × N}/W
Acceptance criteria:
160168
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight containers, and avoid exposure to excessive heat.
Auxiliary Information
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USP35NF30 Page 2522
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