20.9 g of dimethyl-5-amino-benzene-1,3-dicarboxylate was dissolved in 20 ml of concentrated hydrochloric acid in 200 ml of ice water. The solution was diazotized with 7 g of sodium nitrite dissolved in 30 ml of water. 30.4 g of 2-hydroxy-phenylacetic acid was dissolved in 200 ml of water and 24 g of sodium hydroxide. The solution was cooled with 100 g of ice. To this hydroxide solution was then added the diazonium salt solution, all at once, and with vigorous stirring. After 30 seconds the solution was acidified with acetic acid and the precipitate was filtered off. The precipitate was leached with an about 25% ethanol solution which was then diluted with water until a state of weak opalescence was reached. The solution was treated with active carbon and evaporated down to half its volume. Sodium hydrogen carbonate was added until the solution was clear, whereupon the solution was heated (80° C.) and acidified with hydrochloric acid. The solution was cooled, the crystals were filtered off and dried.
