Oxidation‐Reduction Equilibria in Molten Na ₂ O.2SiO ₂ Glass

The oxidation‐reduction equilibria in molten glasses having a soda/silica ratio of 1/2 and containing small amounts of variable‐valence ions of the transition elements titanium, vanadium, iron, cobalt, and nickel, the post‐transition elements tin and antimony, and the rare‐earth element cerium were obtained by equilibrating the melts with various atmospheres. The simple mass expression image was always applicable. In the expression, n is the number of electrons involved in the valence change of the metal M. The value of n is 1 for all systems except for the ions of antimony and tin where n is 2. The ions found are those generally accepted as existing in glass melts which are Ti 3+ , Ti 4+ ; Fez+, Fe 3+ ; Ce 3+ , Ce 4+ ; Mn 2+ , Mn 3 ; Co 2+ , Co 3+ ; Ni 2+ , Ni 3 ; Sb 3+ , Sb 5+ ; and Sn 2+ , Sn 4+ . Two mass action expressions were needed for vanadium‐containing glasses to describe the equilibria between 5+, 4+, and 3 f species.