To a suspension of 180 g of 6-amino-4-hydroxy-2-naphthalenesulfonic acid in 4 liters of water was added 75 ml of 10N sodium hydroxide. To the resulting solution was added 181.8 g of sodium acetate trihydrate, followed by 190 g of m-nitrobenzoyl chloride. The mixture was stirred vigorously under argon at room temperature for 8 hours and then filtered. The solid was washed with water, ethanol and then ether and dried at room temperature. The resulting brown solid (299.4 g) was added to a mixture of 1500 ml of water and 1200 ml of 1N sodium hydroxide and stirred under argon for one hour. The mixture was filtered and the filtrate was acidified to pH 3 with concentrated hydrochloric acid. The resulting precipitate was collected by filtration, washed with water, ethanol, then ether and dried in vacuo in hot water and gave 221.7 g of 4-hydroxy-6-m-nitrobenzamido-2-naphthalenesulfonic acid, sodium salt.
