1. Commercial phthaloyl chloride contains about 94% of halide and some phthalic anhydride. The amount of chloride specified corresponds to a slight molar excess.

2. The checkers employed a modified Widmer column¹ (Fig. 13) that has been used in many organic laboratories, but not officially described. They also used a Vigreux column (50 cm. effective length, 2.7 cm. inside diameter); the first distillation then required 1.5 hours, and the yield was 82–83%. The final temperature of the reaction mixture and observed boiling point will depend upon the type of apparatus used.

3. This procedure has also been checked using a fractionating column 30 cm. in length and 1.5 cm. in inside diameter packed with glass Wilson rings² and provided with the usual jackets for electrical heating. The distillation requires 3 hours. If this column is used, a single distillation gives a product pure enough for most purposes. An unpacked, indented column of about the same dimensions was unsatisfactory (checked by N. L. Drake).

4. Rubber stoppers are used throughout. Tightly fitting ground-glass connections are convenient but unnecessary. The third neck of the flask is used when acid chlorides are prepared from the corresponding acids (Note 9).

5. Above 135° the reaction is likely to get out of control; the ensuing decomposition seriously reduces the yield. For this reason the flask should be immersed only slightly in the oil bath (about one-third of the depth of the liquid layer).

6. With some lots of phthaloyl chloride, owing to the presence of an unknown impurity, the first few drops of the distillate have a reddish color. If the distillation is interrupted and air admitted to the system, the same phenomenon is observed on resuming the distillation.

7. The yield obtained is usually nearer the higher figure. The checkers carried out this preparation using five times these amounts and a 3-l. flask. The distillation times were 1 hour for the first and 3 hours for the final distillation.

8. Fumaryl chloride is best preserved in sealed glass containers. Bottles, closed by rubber stoppers free from sulfur, can be used for short periods. Ground-glass-stoppered bottles are unsuitable, the joints readily becoming "frozen," owing to hydrolysis of the chloride.

9. According to the submitters, yields of the order of 95% of other acid chlorides can be obtained by the use of phthaloyl chloride (1 mole of chloride to 1 mole of a monobasic acid, 2 moles of chloride to 1 mole of a dibasic acid). Zinc chloride, as catalyst, is not necessary in the reaction of most acids and their anhydrides with phthaloyl chloride. When acids are used, it is best to add one of the components slowly, in order to avoid a too violent evolution of hydrogen chloride on warming.