Standard cells with Cd-Pb amalgam electrode

In order to improve the characteristics of standard cells, those containing composite amalgam electrode have been studied. The criterion and test procedures established for selecting high-quality standard cells have been applied. The addition of Pb to Cd amalgam has the effect of reducing the temperature coefficient. The most appropriate composition of amalgam is that of 10 wt % Cd, 3-9 wt % Pb, and the balance Hg. The cells with Cd-Pb amalgam electrode have an EMF higher by about 1000 μV than that of normal Weston cell, and a temperature coefficient at 20° C or -17 μV/°C. The other characteristics and stability are the same as those of normal cells and they are suitable for high-precision work. Although zero temperature coefficient may be obtained by adding Pb and Bi to Cd amalgam, its characteristics are inferior to those of normal cells.