October 31 - November 3, 2004
Element of the Day
Friday, October 22
From
the Anglo-Saxon word lead. Lead's chemical symbol comes from the Latin word for
lead, plumbum. It is sometimes found free in nature, but is usually obtained
from the ores galena (PbS), anglesite (PbSO4), cerussite (PbCO3) and minum
(Pb3O4). Although lead makes up only about 0.0013% of the earth's crust, it is
not considered to be a rare element since it is easily mined and refined. Most
lead is obtained by roasting galena in hot air, although nearly one third of the
lead used in the United States is obtained through recycling efforts.
Discovered by: Lead has been known since ancient times.
Uses: Several lead alloys are widely used. Solder, an alloy that is nearly half lead and half tin, is a material with a relatively low melting point that is used to join electrical components, pipes and other metallic items. Type metal, an alloy of lead, tin and antimony, is a material used to make the type used in printing presses and plates. Babbit metal, another lead alloy, is used to reduce friction in bearings.
Lead forms many useful compounds. Lead monoxide (PbO), also known as litharge, is a yellow solid that is used to make some types of glass, such as lead crystal and flint glass, in the vulcanizing of rubber and as a paint pigment. Lead dioxide (PbO2) is a brown material that is used in lead-acid storage batteries. Trilead tetraoxide (Pb3O4), also known as red lead, is used to make a reddish-brown paint that prevents rust on outdoor steel structures. Lead arsenate (Pb3(AsO4)2) has been used as an insecticide although other, less harmful, substances have now largely replaced it. Lead carbonate (PbCO3), also known as cerussite, is a white, poisonous substance that was once widely used as a pigment for white paint. Use of lead carbonate in paints has largely been stopped in favor of titanium oxide (TiO2). Lead sulfate (PbSO4), also known as anglesite, is used in a paint pigment known as sublimed white lead. Lead chromate (PbCrO4), also known as crocoite, is used to produce chrome yellow paint. Lead nitrate (Pb(NO3)2) is used to make fireworks and other pyrotechnics. Lead silicate (PbSiO3) is used to make some types of glass and in the production of rubber and paints.