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Lead is a heavy, soft, relatively inexpensive metal ($116 a ton in 1940) which in ancient times was a byproduct of silver mining. Lead found uses in plumbing and other applications where its easy workability and resistance to corrosion are valuable. A very dense metal (11.34 g/cm, about half again as dense as iron), it also found use as a ballast and, later, as a component of small arms bullets. Lead was also put to use in low-melting alloys, as a gasoline additive, in storage batteries, and in many other applications, so that primary lead production became the most important source of the metal.
Lead usually occurs as galena (lead sulfide), which
is
easily refined by first roasting the ore to remove the sulfur,
then
smelting with carbon to remove
oxygen, leaving a mixture of lead and other metals. This is
purified by skimming off the copper
that rises to the top, then adding zinc
which extracts any silver or gold
before it, too, rises to the top to be skimmed off. The valuable
gold
and silver are recovered by boiling off the volatile zinc. The
pure lead was often alloyed with antimony or copper to increase
its hardness.
Compounds of lead are quite toxic, and because the body has difficulty ridding itself of lead, it is a cumulative poison. Today safer alternatives have been found for most traditional uses of lead.
Lead was not a serious limiting resource for the Allies, though wartime demand was so great (including as a substitute for scarcer resources) that there were occasional shortages. The United States produced considerable lead from mines in Missouri, and there were also large deposits in Australia and smaller deposits at various locations in the western United States, including Alaska. Japan produced less than 10% of its requirements of lead in the home islands, so that this metal was among the depressingly long list of essential industrial materials that had to be imported. The seizure of Burma, an important lead producer, eased the situation only to the extent that shipping was available to get the lead back to Japan.
References
U.S. Geological Survey (accessed 29 December 2006)
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