The hydroxyl value of epoxy-containing polyester was determined by analyzing acetification principleand using acetyl chloride as acetifier and methylene chloride as solvent. 

Methylene chloride was used as extractant in the extraction of condensed liquid and 3% sodium carbonate solution was used in acid separation. 

Dichloromethane, dichloromethane, molecular CH2Cl2, molecular weight 84.93. Colorless transparent liquid with a pungent odour of similar ether. Insoluble in water, soluble in ethanol and ether. It is not flammable low boiling point solvent, commonly used instead of flammable petroleum ether, ether and so on.