It is a well-known fact that the equilibrium diazonium diazo shifts with the alteration of the concentration of mineral acid: acids transpose the diazo into the diazonium compound. Substituents in the nucleus also have a pronounced influence upon the situation of this eq~ ilibrium.~ The equilibrium shifts to diazo compound if the substituents are more negative. As the reaction of coupling takes place between the diazo compound and the azo component ...