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5.11 DETERMINATION OF ESTERS

5.11 DETERMINATION OF ESTERS

 ​           Boil a convenient amount of ethanol thoroughly to expel carbon dioxide and neutralize it to phenolphthalein TS. Unless otherwise directed in the monograph, weigh accurately about 2 g of the test substance, or other suitable quantity, so that the volume of 0.5 M ethanolic potassium hydroxide VS to be added is at least twice that theoretically required, dissolve it in 5 ml of the neutralized ethanol contained in a hard-glass flask, and neutralize the free acid in the solution with 0.1 M ethanolic potassium hydroxide VS, using 0.2 ml of phenolphthalein TS as indicator. Add 25.0 ml of 0.5 M ethanolic potassium hydroxide VS, attach the flask to a reflux condenser, and boil on a water-bath for 1 hour. Add 20 ml of water, and titrate the excess of alkali with 0.5 M hydrochloric acid VS, using a further 0.2 ml of phenolphthalein TS as indicator. Repeat the operation without the test substance. The difference between the titrations is equivalent to the alkali required to saponify the esters.

APPENDICES • 5.11 DETERMINATION OF ESTERS
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หมายเหตุ / Note : TP II 2011 PAGE 483