An adaption of the above cell arrangement could, alternatively, be used, albeit with caveats. A transparent, acrylic second-generation cell of the above type was modified by drilling a 6 mm wide hole from the top of the cell to the electrolyte reservoir cavity as shown in Figure . A Hg/HgO reference electrode was then introduced into the resulting cavity, such that its active end was immersed in the liquid electrolyte in the reservoir. The electrical connections were then made as described above, with the cell or its contents maintained under an inert Ar atmosphere.