Amalgam Reference Cathode

Thus of the separated reference anodes, the mercurous sulphate electrode is even somewhat superior to the calomel electrode because of its lower polarizability. As reference cathodes, amalgam electrodes have proved to be best. 

Fig. 6-5. RDE and HMRDE cathodic scans of nitrobenzene in 0.01 M HC104 at an amalgamated gold rotating disk. All A traces are RDE curves, all B traces are HMRDE curves. A, B are residual currents A5, B5 are for 5.0x 10-8 M and A50, B50 are for 49.2x 10-8 M. Scan rate for A, B, B5 is 1 mV/s for A50, B50, 3 mV/s. Current sensitivities indicated by markers. Upper potential scale refers to B traces, lower to A. Zero current of A on right ordinate, zero current of B is upper abscissa. Modulation and speed conditions fi1/2 = 60rpml/2, AQW2 = 6 rpm1/2, /= 3 Hz. Averaging time constant is 10 s for A, B, A5, B5, and 3 s for A50, B50. From [67].

Fig. 10.9. Controlled potential cathodic scans of Tl+ at an amalgamated gold disk electrode. All A scans are RDE curves, all B scans are in-phase HMRDE curves. (A, B) 0.01 mol dm" HC104 (A2, B2) 2.0 x 10-7 mol dm- TT in 0.01 mol dm- HCI04. The current sensitivities are indicated by the markers, zero current in all cases is the dashed line. For all curves ft = 3600 rpm, for HMRDE (B) Aft = 6 rpm, frequency = 3 Hz, averaging time constant is 3 s and the scan rate is 2 mV s"1 (after Reference [27]).

The results refer to Pb and Ni cathodes (with a temperature correction of 0.1 V), since ammonium amalgam is formed at a mercury cathode. 

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