Equilibria in solutions of rhodium(III) complex with ethylenediaminetetraacetic acid (EDTA)

Equilibria in the solutions of the rhodium(III) complex of EDTA (H4Y) are studied by means of electronic absorption spectrometry. Mathematical treatment of the spectra provided the estimation of the parameters of spectral bands for two complexes [Rh(Y)(H2O)](-) (lambda(max) = 302 +/- 2 and 371 +/- 2 nm; E >(max) = 265 +/- 3 and 275 +/- 3 L/(cm mole), respectively) and [Rh(Y)](-) (lambda(max) = 289 +/- 2 and 353 +/- 2 nm; E >(max) = 240 +/- 3 and 415 +/- 5, respectively). The equilibrium constant [Rh(Y)(H2O)](-) ai [Rh(Y)](-) is estimated at pK (eq) = -2.7 +/- 0.2. The description of the calculation procedure is provided.