Sulfate-sensing electrodes. The lead- amalgam/lead-sulfate electrode (IUPAC Technical Report)

A new, simplified design and a convenient preparation procedure for the Pb(Hg)|PbSO4|SO42- electrode are proposed. This procedure ensures preparation of stable amalgams and reproducible electrode potentials, which make this electrode useful and attractive for both thermodynamic investigations and electroanalytical applications. For these purposes, the electrode prepared according to the proposed procedure has been exhaustively characterized both thermodynamically and as a sulfate-sensing electrode, in different sulfate solutions, including H2SO4. Also, a practical standardization procedure has been proposed. The Pb(Hg)|PbSO4|SO42- electrode can be structured with a built-in concentrated Li2SO4 salt bridge for use as a sulfate-based reference electrode. This electrode can be operated as a reference electrode alternative to the conventional calomel or Ag|AgCl reference electrodes in electroanalytical practice.

The influence of ammonium lignosulphonate as an expander on the formation of PbSO4 on lead amalgam electrodes

Linear potential sweeps and potentiostatic pulse perturbations have been employed to investigate the influence of the expander ammonium lignosulphonate, on the anodic formation of PbSO4 on lead amalgam electrodes in sulphuric acid solutions at 24 °C. It was found that the expander strongly adsorbs onto the clean amalgam surface thus affecting the formation of the PbSO4 film. The expander increased the charge necessary for passivation, inhibited the cathodic reduction of the film, and produced a more porous film. Evidence is given for the presence of an optimum concentration of expander. Some speculations concerning the mode of action of the expander onto the amalgam surface are presented.