Analytical Principle & Conversion Factor
Acid value is determined by dissolving the oil in a titrated ethanol-diethyl ether solvent mixture and titrating against standardized aqueous or ethanolic potassium hydroxide using phenolphthalein. For castor oil, Acid Value is related to Free Fatty Acids (FFA, % as ricinoleic acid) by the formula: Acid Value ≈ % FFA × 1.88 (or % FFA as oleic ≈ Acid Value / 1.99).
Why Acid Value Dictates Grade Selection
Refined grades such as First Special Grade (FSG) undergo caustic refining to bring AV below 2.0 mg KOH/g (FFA < 1.0%), preventing enzymatic rancidity. In contrast, Commercial Castor Oil (crude expelled) permits AV up to 4.0 or 6.0 mg KOH/g, making it cost-efficient for secondary chemical cleavage and industrial sulfonation where triglycerides are subsequently hydrolyzed anyway.
Frequently Asked Questions
Can high acid value castor oil be used in high-temperature lubricants? +
No. Elevated free fatty acid content causes copper/steel corrosion in gearboxes, catalyzes further thermal degradation, and forms acidic sludge under high friction loads.
How does Nagdev Products achieve low Acid Values in First Special Grade? +
By crushing fresh, dry North Gujarat castor seed with immediate continuous alkali refining and centrifugal separation, preventing hydrolytic degradation.