The standard potential of the electrode Pb mid PbSO₄(s) mid SO₄²⁻, for PbSO₄ + 2e⁻ → Pb + SO₄²⁻, is…

The hydrogen electrode at $1\ \text{bar}$ has $E = -0.0591\ \text{V} \times \text{pH}$, so with a reference electrode of potential $E_{ref}$ the cell emf is $E_{ref} + 0.0591\ \text{V} \times \text{pH}$. A glass electrode is calibrated with two buffers: the slope is the change in reading divided by the change in pH. For a silver halide, $E^\circ(\text{AgX/Ag}) = E^\circ(\text{Ag}^+/\text{Ag}) + 0.0591\ \text{V}\log K_{sp}$, and the same form holds for another metal with $\dfrac{0.0591\ \text{V}}{n}$.