Use
Methanol in methyl acetate can be detected by measuring its solubility in water. At 20o, the solubility of methyl acetate in water is ca 35g per 100mL, but 1% MeOH confers complete miscibility. Methanol can be removed by conversion to methyl acetate, by refluxing for 6hours with acetic anhydride (85mL/L), followed by fractional distillation. Acidic impurities can be removed by shaking with anhydrous K2CO3 and distilling. An alternative treatment is with acetyl chloride, followed by washing with concentrated NaCl and drying with CaO or MgSO4. (Solid CaCl2 cannot be used because it forms a crystalline addition compound.) Distillation from copper stearate destroys peroxides. Free alcohol or acid can be eliminated from methyl acetate by shaking with strong aqueous Na2CO3 or K2CO3 (three times), then with aqueous 50% CaCl2 (three times), saturated aqueous NaCl (twice), drying with K2CO3 and distilling it from P2O5. [Beilstein 2 IV 122.]