The free fatty acid contained in 1g of beeswax consumes milligrams of potassium hydroxide (KOHmg/g). It is one of the quality indicators of beeswax. Generally, the acid value of pure beeswax is 4～9KOH mg/g for medium beeswax and 15～23KOH mg/g for western beeswax. Artificially adulterated beeswax will cause the acid value of beeswax to be high or low. For example, beeswax mixed with paraffin, stearic acid, tallow, etc., has low acid value; beeswax mixed with rosin, etc., has high acid value . The method for determining the acid value of beeswax is neutralization titration.
1. Accurately weigh 3 g of wax and place in a 200 mL flask.
2. Add 25 mL of neutralized dehydrated alcohol and warm until melted.
3. Shake the mixture and add 1 mL of phenolphthalein indicator solution.
4. Tiltrate the warm liquid with 0.5 N alcoholic potassium hydroxide solution until a permanent, faint pink colour is obtained.