Preparation of an Azo Dye / Dyeing with Your Azo Dye
CHM 2012 Experiment 5A: Preparation of Azo Dye1Procedure:
A – Synthesis of Diazonium Salt:
1) Transfer approximately 190 mg of your assigned aminobenzenesulfonic acid and
2.5 mL of a 2.5% sodium carbonate solution into a test tube.
2) Prepare a boiling water bath using approximately 100 mL of water in a 250 mL
beaker. Add a wooden applicator stick to the reaction mixture containing test
tube and begin heating in the boiling water bath.
3) Once the aminobenzenesulfonic acid is dissolved cool the reaction mixture to
4) Transfer approximately 80 mg of sodium nitrite to the test tube containing the
aminobenezesulfonic acid reaction mixture. Stir until the sodium nitrite dissolves
5) Prepare an ice bath and cool the test tube containing the reaction mixture.
Subsequently add 4-5 small pieces of ice and four drops of conc. Hydrochloric
acid to the test tube. Stir the reaction mixture.
6) Allow the reaction mixture to continue cooling with periodic stirring until a white
precipitate appears. If no precipitate emerges after 10 minutes move on to the
synthesis of the azo dye.
B – Synthesis of Azo Dye:
1) Calculate the mass of 1 mmol of your assigned aromatic compound and transfer
this mass to a 25 mL Erlenmeyer flask. Subsequently add 1 mL of a 3M NaOH
solution, mix thoroughly using a glass stir rod, and allow the flask to cool in an ice
2) Stir the diazonium salt suspension prepared in part A in the test tube thoroughly
and transfer the contents to the aromatic compound containing Erlenmeyer flask.
Continue stirring the reaction mixture in the Erlenmeyer flask. Use