effect on the differential capacitance curve.
In NaC104 electrolytes our results 12 agree substantially with Leikis eta/. 6'v that a capacitance minimum at -0.7 V occurs with dilute solutions.
In concentrated (,-~ 1 M) electrolytes, capacitance curves for NaC104 and NaOH are similar, no minimum at -0.7 V however develops on dilution of NaOH electrolytes, the differential capacitance curve for silver in dilute NaOH being flat and relatively featureless 13. "Electrode resistances" are fairly constant throughout.
The addition ofn-butylamine to the electrolytes (1 M NaOH and 1 M NaC104) greatly affected the differential capacitance curves for silver (see Fig. ). A broad (,-~ 0.5 V) capacitance minimum was observed at -0.1 V in both electrolytes indicating that n-butylamine is adsorbed in this potential region. Competition between the anion and n-butylamine for adsorption at the electrode 14 is unlikely in view of this relative insensitivity of the differential capacitance curve to changes in the anion. In neither electrolyte can we find evidence for the adsorption of n-butylamine at -0.7 V NHE. It may be that the threshold of the h.e.r, inhibits the adsorption of n-butylamine at these potentials; however, it is not clear why the adsorption should take place at -0.1 V NHE unless this potential represents Ez (in spite of theoretical predictions 9 and previous experimental data6'7'~2).