AbstractThe Polarographic behaviour of quinaldic acid in the presence of lanthanide cations (Kd3+, Gd3+, Er3+) is studied atpH=4.5 and 0.1MHClO4as supporting electrolyte. The polarographic reduction gives two waves at lower concentrations of quinaldic acid and three waves at higher concentrations. The nature of the waves was investigated. The dissociation constant of quinaldic acid as well as the stability constants of some lanthanide cation complexes with quinaldic acid were determined potentiometrically in 75% (v/v) dioxane‐water at 25°Cand 0.1MKNO3. The solid complexes of Nd, Gd and Er were isolated and studied byir, differential thermal analysis (DTA) and thermogravimetric analysis (TGA) techniqu