Abstract: Equilibria in the formation of Schiff bases between eight aromatic aldehydes including salicylaldehyde and pyridoxal 5'-phosphate with a variety of different amines, diamines, and amino acids have been investigated. The formation constants, the acid dissociation constants of the Schiff bases, and the absorption spectra of the various ionic species of the Schiff bases have been evaluated. The spectra have been resolved into ...