In a 1-l. round-bottomed flask, fitted with a reflux condenser attached to a gas trap, are placed 118 g. (1 mole) of succinic acid and 215 cc. (235 g., 3 moles) of acetyl chloride. The mixture is gently refluxed on the steam bath until all the acid dissolves; this requires one and a half to two hours. The solution is allowed to cool undisturbed and is finally chilled in an ice bath. The succinic anhydride, which separates in beautiful crystals, is collected on a Büchner funnel, washed with two 75-cc. portions of ether, and dried in a vacuum desiccator. The yield of material melting at 118–119° is 93–95 g. (93–95 per cent of the theoretical amount).

Two hundred thirty-six grams (2 moles) of succinic acid (Note 1) and 153.5 g. (1 mole) of phosphorus oxychloride are placed in a 1-l. Claisen flask. One neck of the flask is equipped with a reflux condenser connected to a gas trap; the other neck and the side arm of the flask are closed with corks. The mixture is heated (Note 2) with a free flame for about fifty minutes until no more hydrogen chloride is evolved. The condenser is removed and the flask is arranged for distillation, with a tube leading from the side arm of the receiver to the drain in order to carry off the vapors. A few cubic centimeters of distillate is collected below 255°, at which temperature the receiver is changed and succinic anhydride is collected from 255–260° (Note 3). The product melts at 118–120° and weighs 164–192 g. (82–96 per cent of the theoretical amount).

The succinic anhydride may be purified by dissolving 50 g. of the crude material in 35 cc. of acetic anhydride. The hot solution is cooled in an ice bath. The crystals are filtered with suction, washed with two 20-cc. portions of cold, absolute ether, and air-dried quickly at 40°. The yield of the pure anhydride, which melts at 119–120°, is 43.5 g.