New spectrophotometric evidence for the existence of HCrO-4
A spectrophotometric study of the protonation and dimerization of CrO2-4 at different concentrations in the pH range 8-2.5 at 25°C in 0.1 M (Na)Cl medium led to the characterization of HCrO-4 and Cr2O2-7 in terms of formation constants and absorption spectra. When the pH is varied at constant Cr(VI) concentration the experimental spectra exhibit one real and three accidental isosbestic points. The results of this investigation do not corroborate recent work in which the non-existence of HCrO4 was claimed. The spectrophotometric determined equilibrium constants have been verified by potentiometric titrations. The values are : log β11 = 6.09 ± 0.04 and log β22 = 13.94 ± 0.06. © 1998 Elsevier Science Ltd. All rights reserved.