Weigh accurately 0.5 gm of sample into 50 ml neutralized ethanol taken in a 250 ml conical flask. Swirl the solution to dissolve the sample and heat on a water bath, if necessary.
Titrate the solution with 0.1 Normal potassium hydroxide solution using a 5 ml burette with phenolphthalein as indicator. Add drop-wise near the end point. Note the burette reading when the colorless solution changes to pink on a single drop.
Acid value = (A---N---56.1)/W
A = Milliliters of 0.1 Normal potassium hydroxide required for sample titration.
N = Normality of potassium hydroxide solution.
W= Weight in grams of the sample taken.