Formation of mixed-metal complexes in the chromium (3)-rare earths-d-tartaric acid system

The complexing in the system of Cr(3)-r.e.e.-d-tartaric acid (H2T) in which rare earth elements are Nd, Eu, Gd, Tb, Er, was studied by the spestrophotometric technique and potentiometric titration. Experiments were carried out at the temperature of 97+-3 deg C. The pH 4,5-5,0 area was determined to be the area of existance of the mixed-metal complex. The relation of complex components was determined by the molar ratio method. For all the studied rare earths this relation equals Cr:r.e.e.:H2T=1:1:2