In this work, some observations that confirm non-specific interactions between zirconium and hafnium are presented. This phenomenon, which induces significant differences between the spectrophotometric and extractive behaviour of the isolated elements related to their mixtures, indicates the existence of an important synergistic effect on the depolymerisation reactions involved in the aqueous chemistry of the elements. All experimental evidences suggest that the presence of zirconium can minimise the polymerisation of hafnium, favouring its reaction with the studied complexing agent. (C) 1999 Elsevier Science B.V. All rights reserved.494937941