For several 1,3-diaryl- and 1-alkyl-3-aryltriazenes, infraared evidence of tautomerism III has been given;1,2in their ir spectra, in fact, these compounds generally show two separate N-H stretching bands. The relative intensities of these bands are influenced by the substituents,1,2It was recognized,how ever, that the tautomeric equilibrium constants KTcannot be determined with accuracy by ir bands intensity measurements as the molar extinction coefficients of forms I and II are not known.1