Diazobenzenesulfonic Acid Solution

Diazobenzenesulphonic acid solution

Heat 0.2 g of sulfanilic acid with 20 mL of 1m hydrochloric acid until dissolved, cool to about 4° and add, dropwise, 2.2 mL of a 4% w/v solution of sodium nitrite, swirling continuously. Allow to stand in ice for 10 minutes and add 1 mL of a 5% w/v solution of sulfamic acid.