A 3-l. Pyrex flask (Note 1) is fitted with an efficient mechanical stirrer, a dropping funnel, a thermometer, and an upright tube (Note 2) to act as an air condenser and to carry the trimethylene oxide vapors through a spiral condenser. In the flask are placed 1344 g. (24 moles) of potassium hydroxide and 120 ml. of water. The contents are heated to about 140° with stirring (Note 3). The upper part of the flask should be kept sufficiently hot so that the potassium hydroxide mush which is thrown up on the sides does not solidify. The spiral condenser is then packed with an ice-salt mixture, and 1092 g. (8 moles) of γ-chloropropyl acetate (p. 203) (Note 4) is slowly run into the flask by means of the dropping funnel so that the distillate comes over at the rate of about 1 drop a second. The time required for the addition is 1.5–3 hours. After all the ester has been added, the mixture is stirred, with continued heating at 140–150°, until the distillate amounts to 250–400 g., depending on how efficiently the air condenser has separated the trimethylene oxide from higher-boiling substances. About 100 g. of potassium hydroxide pellets is added to the crude distillate, which is then distilled through a 25-cm. fractionating column packed with ¼-in. Berl Saddles. By careful distillation the trimethylene oxide can be obtained in a single fractionation, the portion boiling at 45–50° being collected. The higher-boiling residue still contains some trimethylene oxide, but consists mostly of water, allyl alcohol, and unchanged γ-chloropropyl acetate. The yield is 195–205 g. (42–44%). Redistillation over freshly fused potassium hydroxide gives a product boiling at 47–48°; n_²³D 1.3905.