Hydroxyl value á401ñ—
Transfer 2g,accurately weighed,to a glass-stoppered,250-mLconical flask,add 5.0mLof a freshly prepared mixture of 1volume of acetic anhydride and 3volumes of pyridine,and swirl to mix.Connect the flask to a reflux condenser,and heat on a steam bath for 2hours.Add 10mLof water through the condenser,swirl to mix,heat on a steam bath for an additional 10minutes,and allow to cool to room temperature.Add through the condenser 15mLof normal butyl alcohol that previously has been neutralized to phenolphthalein,remove the condenser,and wash the tip of the condenser and the sides of the flask with an additional 10mLof neutralized normal butyl alcohol.Add 1mLof phenolphthalein TS,and titrate with 0.5Nalcoholic potassium hydroxide VSto a faint pink endpoint.Perform a blank determination on a 5.0mLportion of the acetic anhydride-pyridine mixture.To determine the amount of free acid in the Oil,weigh accurately 10g into a 250-mLconical flask,add 10mLof pyridine that previously has been neutralized to phenolphthalein,swirl to mix,add 1mLof phenolphthalein TS,and titrate with 0.5Nalcoholic potassium hydroxide VSto a faint pink endpoint.Calculate the hydroxyl value taken by the formula:
56.1N[A+(BW/D)-C]/W,
in which
Nis the normality determined for the alcoholic potassium hydroxide solution,
Ais the volume,in mL,of 0.5
Nalcoholic potassium hydroxide consumed by the blank,
Bis the volume,in mLconsumed in the free-acid titration,
Wis the weight,in g,of Oil taken,
Dis the weight,in g,of Oil used in the free-acid titration,and
Cis the volume,in mL,consumed in the sample titration.The hydroxyl value is between 160and 168.