Use a silver wire or strip in contact with excess solid silver sulfate, immersed in a sulfate filling solution of known, stable activity. A porous frit connects the filling solution ionically to the sample while limiting bulk mixing. The reference housing should maintain the salt/electrolyte composition rather than letting the sample directly determine it.
Connect the unknown working electrode to the positive input and the silver reference to the negative input of a high-input-impedance voltmeter. The frit or sulfate-compatible salt bridge completes the ionic circuit. At negligible measuring current,
(1)
A stable, small junction contribution is desirable. The reference electrode should not carry the counterelectrode current in a driven experiment: a separate counterelectrode is used when current is passed.
Figure 1.
A sulfate-compatible silver reference measures a potential difference with negligible current
. Original circuit schematic. Silver, excess silver sulfate and controlled sulfate electrolyte define the reference compartment; the frit provides ionic contact. The voltmeter polarity fixes the sign of the measured working-minus-reference potential. Details.

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