In a flask, dissolve 20 gram aniline in dilute HCl and cool it to 5°C. In this flask, NaNO2 solution is added, resulting in benzenediazonium chloride. Fill this solution in a separating funnel and drop it into a 500 ml flask.
In this flask, 10 gram cupreous chloride and 100 ml HCl solution water is kept on the heat. This flask is equipped with an ejector air capacitor. It mixes all the benzenediazonium chloride in the flask, then heats the flask at 60°C for half an hour on a water heater.