Reference electrodes, resin-coated

A bare platinum electrode was cleaned as previously described and then allowed to come to adsorption equilibrium with air in the gas chamber. When dry nitrogen was passed through the chamber, the potential difference between the platinum surface and the FEP resin-coated electrode increased rapidly, reaching an equilibrium value 0.5 volt higher in approximately 2 hours. Dry oxygen was then introduced into the chamber and the surface potential of the platinum decreased to a steady-state value of + 0.2 volt relative to the reference electrode (see Figure 6). This system was allowed to remain in that condition for 24 hours, during which time there was only a 20-mv. increase in the contact... 

Active electrode. Platinum coated with bulk Ci8 amine Reference electrode. Gold with FEP resin coating All measurements at 23° G. and 50% R. H. 

A major difficulty with contact potential work is the provision of a completely inert reference electrode. Poisoned nickel has been used, but aged gold or platinum is more widely applicable. Bewig and Zisman have described reference electrodes of gold and platinum coated with Teflon resin. These electrodes were more stable than the bare metals in wet and dry oxygen, nitrogen and in carbon dioxide, hydrogen and helium. 

Fig. 9. Clark-type wall-jet oxygen sensor fabricated from printed circuit board. (A) cross-section, (B) active surface view (without organic layers) (1) reference anode (Cu/Ni/Au/Ag/ AgCl), (2) gelatin layer containing KCl, (3) Working cathode (Cu/Ni/Au), (4) polystyrene layer, (5) board substrate, (6) electrode contact, (7) metal-coated hole (Cu) filled with epoxy resin.

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