In the 1-l. three-necked flask A (Fig. 8) is placed 550 cc. (4.56 moles) of 46 per cent hydrobromic acid (sp. gr. 1.46) (Note 1). Ethylene oxide (Note 2) is led into the acid solution as indicated in Fig. 8. The tank E is arranged on a balance so that the amount of ethylene oxide which is used can be weighed. B is a U-tube containing water to indicate the rate of flow of the gas. D is a glass coil surrounded by ice and salt which cools the gas nearly to the liquefaction temperature. C is another U-tube containing water which shows whether or not the gas is being completely absorbed.

The flask A is surrounded by an ice-salt bath and the stirrer is started. When the temperature of the acid has dropped to 10°, 132 g. (3 moles) of ethylene oxide is added over a period of about two and one-half hours (Note 3). The stirring is continued for one hour (Note 4) after all of the ethylene oxide has been added and the temperature is maintained below 10° during the reaction.

After this time the excess hydrobromic acid is neutralized with excess sodium carbonate, of which about 100 g. of anhydrous salt is required. To the aqueous solution is then added about 100 g. of anhydrous sodium sulfate until some of the solid does not dissolve. A layer of ethylene bromohydrin separates and is collected in 200 cc. of ether. The ether layer is below the aqueous layer. The solid sodium sulfate is filtered from the solution and washed once or twice with a small amount of ether (Note 5) to remove any mechanically held bromohydrin. The aqueous filtrate is twice extracted with 200-cc. portions of ether (Note 6). The combined ether extracts are dried overnight with anhydrous sodium sulfate, filtered and distilled from a steam bath (Note 7). The remaining bromohydrin is distilled under reduced pressure (Note 8). After two distillations the fraction boiling at 55–59°/22 mm. (Note 9) is pure ethylene bromohydrin. The yield is 327–345 g. (87–92 per cent of the theoretical amount).