In a 3-l. open flask, equipped with a mechanical stirrer and a thermometer and cooled in an ice bath, is placed a suspension of 65 g. (0.5 mole) of acrolein acetal (p. 17) in 600 cc. of water. The suspension is cooled to 5° (Note 1), and a solution of 80 g. (0.5 mole) of potassium permanganate in 1.5 l. of water is added, with stirring, at the rate of about 25 cc. per minute. The temperature is kept as near 5° as possible during the addition. Soon after the stirring is stopped, the mixture sets to a gel (Note 2). After standing for two hours, the mixture is heated for one hour on the steam bath and then filtered by suction on a 30-cm. Büchner funnel. The residual manganese dioxide is pressed thoroughly and washed with 150 cc. of cold water. The filtrate (about 2.3 l.) is kept cool and treated with 1.2 kg. of freshly dehydrated commercial potassium carbonate. The layers are separated and the water layer is extracted with four 100-cc. portions of ether. The ether extracts are added to the crude acetal layer, and the mixture, which may consist of two layers (Note 3), is dried over 10 g. of potassium carbonate. After removal of the ether, the residue is distilled under reduced pressure. The yield of product boiling at 120–121°/8 mm. is 55 g. (67 per cent of the theoretical amount).