To a beaker 800 mL of hot water, 76 mL of 25% ammonia, 19.2 g of ammonium carbonate and 10.8 g of ammonium chloride are added, while heating at 55°C 163 g of isatoic anhydride is added over the course of 30 minutes with stirring. After the addition the solution is heated at 60°C for additional 10 minutes, the solution is then cooled down in a freezer, filtered and washed with some water. Recrystallize the crude product from hot water. The brown coloration of the pure product may be removed with some decolorizing activated carbon.
The alkaline solution
Addition of the isatoic anhydride
The crude product crystallized out on cooling
The pure recrystallized product