A mixture of 7.0 g. of ethyl p-[(p-tridecyloxybenzyl)amino]benzoate (prepared as described in Example 22), 7.0 g. of potassium hydroxide and 150 ml. of ethanol-water (9:1) is refluxed for 3.5 hours. The solution is acidified while hot, diluted with water, filtered and the solid washed with water to give white crystals, m.p. 110°-113° C. and 145°-150° C. The solid is heated with 200 ml. of glacial acetic acid and the solution chilled and filtered to give crystals, m.p. 110°-112° C. and 155°-160° C. The filtrate is diluted with water to give white crystals (pure by TLC) m.p. 108°-112° C. and 150°-155° C. The first crop of crystals is slurried in 75 ml. of acetone, filtered and the filtrate chilled and filtered. The filtrate is diluted with water to give white crystals (pure by TLC). The two crops pure by TLC are combined, dried in vacuo to give white crystals, m.p. 110°-112° C. and 155°-160° C.
