Anthranilic acid (10 grams) is dissolved in acetic anhydride (20 ml) and the temperature raised progressively to 190-200°C at which temperature distillation takes place. The last traces of acetic acid are removed under vacuum and after cooling to about 50-60°C, o-toluidine (10 grams) is added in portions. The temperature is then raised to 170-200°C when the excess water and o-toluidine is gradually distilled off, finally maintaining the temperature at 180-200°C for 2 hours. After cooling to about 100°C, 30ml dilute HCl is added and the mixture boiled and stirred. The solution is neutralized with NaOH with stirring, and the crude product which separates is recrystallized twice from alcohol. The yield is 70% of theory.