Preparation of solution A: Combine 2 g of p-nitroaniline, 5.5 mL of conc. HCl and 5.5 mL of water, heat slightly to dissolve everything then place the beaker into an ice bath. Dissolve 1.5 g of sodium nitrite in 3.5 mL of water and add it to the solution with stirring, the temperature must not rise above 5°C.
Preparation of solution B: Combine 2.1 g of 1-naphtanol, 2.8 g of sodium hydroxide and 10 mL of water, stir until dissolved. Cool down to 0°C.
To the solution A pour the solution B slowly with very vigorous stirring. Add 5 mL of conc. HCl, filter, and wash with 100 mL of water.