All three members of group 12 are used in the manufacture of batteries. Zinc is used in carbon-zinc cells, where it acts as both the container and the negative pole; mercury (II) oxide is used in mercury cells, where it functions as the positive pole; and nickel is used in rechargeable nickel-cadmium batteries. The toxicity of mercury has meant that some battery companies no longer manufacture mercury cells. The mercury cells pictured are no longer produced.
Zinc is also alloyed with copper in brasses, and is used most widely as a protective coating for other metals. Galvanization (which involves dipping metals in molten zinc) and electrolytic deposition give surfaces which are extremely resistant to corrosion. Cadmium, although produced in much smaller quantities than zinc, is also used in electroplating.
Mercury is used in thermometers and, with silver and tin, in dental amalgams. Its compounds, like the element itself, are highly toxic, and they are used in insecticides.
