Researches on sulphanilamide, para-amino-benzoic acid and their derivatives. III: Ultraviolet absorption spectra and potentiometric titrations

With the aim of providing more facts for the discussion of the mode of action of the sulphonamides and of p-aminobenzoic acid, the ultraviolet absorption spectra are recorded for a number of sulphanilamide derivatives, p-aminobenzoic acid and related compounds. Moreover their electrochemical properties are determined by potentiometric titration. The results obtained permit a more detailed discussion of the state of these molecules in neutral solution, of the differences between p-aminobenzoic acid and its isomers and of those between sulphanilamide and its heterocyclic derivatives. Furthermore the separate position of compounds like p-aminomethylbenzoic acid and of p-aminomethyl-benzenesulphonamide (Marfanil) is clearly indicated.