Illustrated Glossary of Organic Chemistry

Azo dye (diazo dye): A dye molecule containing a diazo functional group between two aromatic rings. Most azo dyes are red, orange, or yellow. Prontosil, an early antibiotic, is a red azo dye.

Name of azo dye:
 FD&C Red #40
(Allura Red AC)		    
FD&C Yellow #5
(Tartrazine)
   Mixture of
FD&C Yellow #5
and FD&C Blue #1   

FD&C Blue #1  
Azo dye molecular structure:
Note diazo functional group.



Mixture of FD&C Yellow #5
and FD&C Blue #1

Not an azo dye.
Aqueous solution of azo dye: