Electroanalysis with tungsten electrodes : I. The tungsten/platinum bimetallic pair in potentiometry at zero current

The W/Pt bimetallic pair has been applied in various potentiometric titrations. Except for the neutralization of dicarboxylic acids, e.g., oxalic, the pair is suitable for neutralization titrations where ΔE/ΔV values at the equivalence point are higher on W than on Pt. Tungsten oxides increase the inflexion pd. The pair is also suitable for oxidation/reduction titrations using permanganate, dichromate, and ceric sulfate, and for precipitation reactions with silver nitrate. However, it gives a small inflexion pd in the oxidation of thiosulfate by iodine. EDTA titrations of copper, magnesium, and calcium give a sharp inflexion in the case of copper only. This pair may be useful in routine analyses requiring a robust electrode assembly but not a high degree of accuracy.