In a previous report a new method for the preparation of orthanilic acid has been presented. According to the reaction, a mixture of 1 mole of sulfamlc acid and 4 mole of aniline, on heating at 160℃ for 13 hrs, offered about 0.4 mole of orthanilic-,0.3 mole of sulfanilic acid and a small amount of aniline disulfonic acid3. In this report the isolation of orthenilic-, and sulfanilic acid from the reaction mixture is described. The isolation was performed successfully by utilization of the differences of acidity and of solubility of potassium salt between the two isomers. The acidity of orthanilic acid was higher than that of sulfanilic acid and the solubility of potassium orthanilate was 34.8 g and that of sulfanilate was 47.4g per 100 ml of water at 31℃. Orthanilic- and sulfanilic acid of high purities were obtained in 80% yield from the reaction mixture.