to 400 ml beaker is placed 60 ml of aniline ax ml of concentrated hydrochloric acid. In small beaker to prepare a saturated solution of potassium nitrite xg. Both beakers placed in the cooling bath (crushed ice and salt). after about 15 minutes, start adding sodium nitrite to a solution of aniline hydrochloride - maintaining the temperature at 0 ° C! During the addition of nitrite vigorously stir the solution gets pasty consistency (arising benzendiazonium chloride reacts with excess aniline to form an azo dye), after addition of all the nitrite let loose mixture to warm to room temperature. Resuspended azo filtered and dried in air.