Stability of Neptunium(V) in Concentrated Acetic Acid Solutions

Abstract

Np(V) acetate in glacial acetic acid and aqueous acetic acid solutions is resistant to disproportiona-tion and occurs in equilibrium with the NpO₂(Ac)·H₂O precipitate. Within the time of dehydration with excess acetic anhydride, Np(V) disproportionates. The inverse reproportionation process occurs after adding excess water to anhydrous acetic acid containing acetic anhydride, Np(IV), and Np(VI). Addition of HClO₄ causes rapid disproportionation of Np(V) in anhydrous acetic acid and in concentrated acetic acid solutions. The spectra of suspensions containing Np(V) and potassium acetate in concentrated acetic acid contain absorption bands with maxima at 990 and 1020 nm, assigned to NpO₂(Ac)₃^2- anions and K₂NpO₂(Ac)₃ particles, respectively.