Acetyl value and ester value
- 1. Acetyl value • Definition - Acetyl value is the number which expresses in miligrams the amount of KOH required to neutralise the acetic acid liberated by the hydrolysis of 1g of the acetylated substance Significance Measure the hydroxy acids in lipids
- 2. Procedure • Determine the saponification of value of the given substance or fat • Place 10 g of fat substance with 20 ml of acetic anhydride in long necked, round bottomed 200 ml of flask attached to a reflux air condenser
- 3. Procedure Support the flask on a sheet of heat resistant material in which a hole of about 4 cm in diameter has been cut and heat it with a small, naked flame not more than 25 mm in height and which does not impinge on the bottom of the flask.
- 4. Procedure • Boil gently for 2 hours, allow to cool, pour into 600 ml of water contained in large beaker • Add 0.2 g of pumice powder and boil for 30 minutes. cool, transfer to a separator and discard the lower layer.
- 5. Procedure • Wash the acetylated product with 3 or more quantities, each of 50 ml of a warmed saturated solution of NaCl until the washings are no longer acid to litmus paper • Finally shake with 20 ml of warm water and remove the aqueous as completely as possible
- 6. Procedure • Pour the acetylated substance in to a small dish,add 1 g of powdered anhydrous sodium sulphate, • Stirr thoroughly and filter through a dry pleated filter • Determine the saponification value of the acetylated substance
- 7. Calculation • Acetyl value = 1335(b-a) / (1335-a) Where a = saponification value of the substance b = saponification value of the acetylated substance
- 8. Ester value • Ester value is the number of milligrams of KOH required to saponify the esters present in 1g of the substance • Ester value = saponification value – Acid value
- 9. Procedure • Determine the acid value and the saponification value Calculate the ester value from calculation Ester value = saponification value - acid value