214
5 – Applications
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Figure 82 – Schematic of cell used for measuring O
2−
activity
in molten salt LiCl-KCl (from Tremillon & Picard, 1983).
This cell uses the following electrochemical chain:
α β
γ
δ
ε
λ
χ
Cu / Ag / Ag
+
in LiCl-KCl / porous alumina / O
2−
in LiCl-KCl / YSZ / Pt,O 2 / Cu
(1) (2)
(3)
(4)
(5)
(6) (7) (8)
where α, β, γ, …, χ represent the interfaces and (1), (2), (3), …, (8) represent
the phases.
The cell consists of
2 a reference electrode made of the first species (Ag
+
/Ag) (interface β) obtained by dissolving a certain amount of AgCl in the molten salt LiCl-KCl,
denoted “int. ref.,”
2 a gaseous measuring electrode (interface λ) obtained by depositing a platinum coating (7) on the inside of a stabilized zirconia tube (YSZ), which is
in contact with the ambient air,
2 the stabilized zirconia membrane (6), which is sensitive to O
2−
ions (interface ε),
2 a liquid junction within a porous alumina tube (4) between the reference
salt (3) and the salt being studied (5).
The emf of the chain is
ΔE = φ
8 − φ
1
where φ is the electric potential.