pH-metric and spectrographic investigation of neodymium hydrazinediacetates in aqueous solutions

Mono-, bis, and tris-hydrazinediacetates of neodymium form in the system, depending on the ratio of neodymium (3) and hydrazinediacetic acid (H2Z) in solution, as well as on the pH. The absorption bands corresponding to NdZ+ and NdZ2- at 4285 and 4293 A can be detected in highly diluted solutions. At a reactant concentration ratio of 3:1 and higher, with pH>7, only the absorption band of 4301 A appears, which is correlated with the complex NdZ33- The pH-metric and spectrographic methods yield closely similar values of the stability constant for NdZ33-, namely Ksub(st)=3.69 and 3.52, respectively. For complexes of NdZ+ and NdZ- the stability constant has been found from the pH-metric titration curve and is equal to lgKsub(st)=7.08 and lg Ksub(st)=4.61, respectively. It is shown that complexes of neodymium with H2Z are slightly more stable than complexes of Nd with iminodiacetic acid