CHEMISTRY OF NIOBIUM CHLORIDES IN THE CSCL-NACL EUTECTIC MELT .3. SOLUBILITY OF NB2O5 AND SRO IN THE CSCL-NACL EUTECTIC MELT WITH ADDITIONSOF NBCLX (X=4, 5)

The reactions between NbClx (x = 4, 5) and Nb2O5(s) or SrO(s) have bee n studied in the eutectic NaCl-CsCl melt at 650 degrees C. Samples wer e taken from melts containing NbClx in equilibrium with these oxides a nd analysed for oxygen, niobium and, if present, strontium. The analys is indicated that NbCl5 reacted with Nb2O5(s) according to the reactio ns 3NbCl(6)(-) + Nb2O5(s) + 7Cl(-) = 5NbOCl(5)(2-) s and NbOCl52- + Nb 2O5(s) + (3x - 5Cl- = 3NbO(2)Cl(x)((x-1)-). The first reaction was com pletely shifted to the right. The equilibrium established for the seco nd reaction had an equilibrium constant (pure component standard rate) K = 5 x 10(-5). NbCl4 reacted with Nb2O5 according to the reaction 3N bCl(6)(2-) + Nb2O5(s) = 3NbOCl(x)((x-2)-) + 2NbOCl(5)(2-) + (8 - 3xCl- . The NbOCl52- formed in this reaction reacted further with Nb2O5(s). In the presence of an excess of SrO(s), Nb(IV) and Nb(V) precipitated probably as NbO2(s) and MNbO(3)(s) (M = Na,Cs, 1/2 Sr), respectively.