In a 12-l. round-bottomed flask equipped with stirrer, dropping funnel, and efficient reflux condenser are placed 450 g. (5 moles) of urethan (m.p. 46–48°), 7.5 l. of dry ether, and 218 g. of sodium wire (Note 1) and (Note 2). The mixture is warmed, and evolution of hydrogen accompanied by formation of sodium compound soon begins; after 2–3 hours the greater part of the metal will have been replaced by a gelatinous white precipitate. The stirrer is now started and the mixture warmed under reflux for an additional 2 hours. The flask is then cooled externally with running water, and 1050 g. (9.6 moles) of ethyl chlorocarbonate is added slowly over a period of 2 hours. The gelatinous precipitate becomes powdery, and the remainder of the sodium dissolves. After all the ester has been added, the mixture is stirred overnight at room temperature and then filtered (Note 3). The white residue is washed with 1 l. of ether, and the ether is removed from the combined solutions by evaporation on a steam bath (Note 4). The residual oil is distilled; after a fore-run containing some urethan, the product distils at 143–147° /12 mm. The yield is 575–640 g. (51–57%). On redistillation, all the product boils at 146–147° /12 mm.