The results of spectroscopic studies of Nb anodic dissolution, dissolution of NbCl5 and reaction of various niobium oxides with HCl in different chloride melts at 450-7500C are presented. Nb(III) species, NbCl63-, is the major product of niobium anodic dissolution at current densities up to 40 mA/cm2. Addition of NbCl5 to alkali chloride melts predominantly leads to the formation of Nb(V) species, NbCl6-. Upon increasing Nb(V) concentration NbCl6- tend to decompose to Nb(IV) and Cl2. Reaction of NbO and NbO2 with HCl proceeds via an intermediate oxygen-containing Nb(IV) complexes. Oxygen-free Nb(IV) ions, NbCl62-, were obtained by exchange reactions between metallic niobium and melts containing Bi(III), Ag(I) or Ni(II) chloro-ions. Electroreduction of Nb(III) on a tungsten working electrode below -1.45 V vs. Cl2/Cl- led to the formation of metallic niobium, no evidence of intermediate reduction products was obtained.
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