Synthesis of Isatoic anhydride

100 g of finely powdered phthalimide was added to a 2 L beaker, 250 mL of water was then added with stirring. In a separate beaker 28 g of sodium hydroxide was dissolved in a minimum amount of ice water needed, pour the solution to the 2-liter beaker with vigorous stirring. Then add 200 g of crushed ice to the beaker, add 590 g of  8.25% sodium hypochlorite solution at once with vigorous stirring. After 5 minutes add 41 g of 31% hydrochloric acid, then stir and after 5 minutes add 14 g of conc. hydrochloric acid. Heating the solution to 30°C, and remove from the hot plate stir for another 30 minutes. Filter and wash the product with 200 ml of warm water. Dry the product. Recrystallize in xylene or acetic acid.

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