An all-glass reference electrode for molten salt systems

Electrode potentials in fused systems X. Measurement of cation concentration in molten salts using glass membrane electrodes

“…W e begin by di sc ussin g a simpl e co nce nt ration cell + X~ = 1 gives wh ere th e a's re prese nt ac ti viti es on the mole frac ti o n sca le. As s hown previously th e e mf of thi s cell is (1) whi c h is formally also th e potential of th e cell with liquid jun c tion . Th e c hi ef differ e nce betwee n me mo brane a nd liquid jun ction pote ntial s is th at in th e form er c ase (a) only ions tran s porte d across the glass ar e in clud e d in the s umm a ti on, a nd (b) if th e melt co ntain s more than 2 perce nt sodium , ti is a constant in any cell and ca n be ta ke n outside th e integral [5].…”

“…A number of membran e elec trode designs, all based on the Ag-Ag+ equilibrium, have been published [1,2,3,4).1 In contrast to aqueous systems in which the glass electrode functions as indicator electrode, primarily for pH measurements, in molten salts it serves as a reference electrode with respect to which potential changes at other electrodes can be observed. For this appli cation the primary requirement is stability and reproducibility, i.e., several electrodes of identical design s hould vary as little as possible in potential be havior.…”

“…For sys te ms co ntainin g a sin gle ani on only catio n term s ar e in c lude d in th e s umm ati on. S in ce It ; = L e q ( 1) beco mes Equation (2) is use ful for th e meas ure me nt of a n unkn own co mpositi on onl y if (a) tM t is r e ally inde· pe nd e nt of compos iti on ove r til e e ntire c on centration ra nge, (b) no chan ges occ ur in th e refe re nce electrode , e.g. co mpos iti o n c h anges by va pori za ti on , a nd (c) th e th erm od yna mi c be havi or of th e melt , i. e. , th e ac tivit y coefficients of the components , are known.…”

Self-optimizing control

“…Pyrex, so called sodium glass, is commonly used as a reference electrode at a molten salts temperature between 450 and 600 o C, since it can be fabricated easily into a thin-wall tube and thus provide a sufficient ionic conductivity. [4][5][6] It cannot be used at the temperatures above 600 o C, since it can be deformed easily due to its low melting point (820 o C).…”

E.M.F. study of lower oxidation states in molten sodium tetrachloroaluminate

“…Junctions employed varied from the fine porosity frit used by Hill, et al (29), to the asbestos fiber sealed through glass used by both Senderoff and Brenner (30) and Flengas and Ingraham (28), to the thin glass bubble developed by many workers and applied specifically to dilute Ag"*" solutions by Bockris, et al (31).…”