Determination of unsulphonated ester and soap

Weigh a 5 g sample in a beaker, dissolve in 50 ml neutral ethanol and titrate to phenolphthalein with 0.1 M sodium hydroxide. Transfer to a separating funnel, using 50 ml water. 

Extract with three 50 ml portions of petroleum ether (caution flammable). Keep the lower layer. 

Combine the petroleum ether extracts and wash with 50 ml water. Add the water to the lower layer from step 2. 

Evaporate the petroleum ether extract almost to dryness on a steam bath. Complete the evaporation under an air jet without heating. Add 5 ml acetone and repeat the evaporation. Dry to constant weight in a vacuum desiccator at room temperature. The residue is the unsul-phated ester. 

Acidify the combined lower layers from steps 2 and 3 with IM 

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