Metal Profile: Lead
Lead is a soft, gray, lustrous metal with a high density and low melting point. Although hazardous to our health, humans have been extracting and using lead for over 6000 years.
- Atomic Symbol: Pb
- Atomic Number: 82
- Atomic Mass: 207.2 amu
- Melting Point: 327.5°C (600.65 K, 621.5 °F)
- Boiling Point: 1740.0°C (2013.15 K, 3164.0 °F)
- Density: 11.36 g/cm3
Ancient Egyptians were likely the first to extract lead, which they used to make small sculptures.
Compounds of lead have also been found in Egyptian pottery glazes. In China, lead was used to forge coins by 2000BC.
The Greeks were the first to recognize lead's corrosion resistant properties and applied lead as a protective covering on ship hulls (an application that lead compounds are still used for to this day). The Romans, consequently, began extracting large quantities of lead to for their expansive water systems.
By the first century AD, it is believed that Roman lead production was approximately 80,000 tonnes per year. Sheets of lead were used to line baths, while lead piping was created by wrapping sheets of lead metal around a rod and soldering the edges together. Lead piping, which was used until the 20th century, helped protect against corrosion, but also resulted in widespread lead poisoning.
By the Middle Ages, lead was being used as a roofing material in some areas of Europe because of its resistance to fire.
In fact, both Westminster Abbey and St. Paul's Cathedral in London have lead roofs that date back hundreds of years. Later, pewter (an alloy of tin and lead) was used to make mugs, plates, and cutlery.
Following the development of firearms, lead's high density was identified as an ideal material for bullets - or lead shot.
Lead shot was first produced in the mid-17th century by allowing melted lead droplets to fall into the water where they would solidify in a spherical shape.
About half of all lead produced each year comes from recycled material, which means that lead has one of the highest recycling rates of all materials in common use today. In 2008, worldwide production of lead exceeded 8 million tonnes.
The largest producers of mined lead are China, Australia, and the USA, whereas the largest producers of recycled lead are the USA, China, and Germany. China alone accounts for about 60 percent of all lead production.
The most economically important lead ore is called galena. Galena contains lead sulfide (PbS), as well as zinc and silver, all of which can be extracted and refined to produce pure metals. Other ores that are mined for lead include anglesite and cerussite.
A large proportion (about 90 percent) of all lead is used in lead-acid batteries, lead sheets and other metal applications that are recyclable. As a result, about 5 million tonnes of lead (or 60 percent of all production) were produced from recycled materials in 2009.
The primary application for lead continues to be in lead-acid batteries, which account for approximately 80 percent of the metal's use.
Lead acid batteries are ideal for all types of vehicles because of their relatively large power-to-weight ratio, which allows them to supply the high surge currents required by automobile starter motors.
Advances in lead-acid battery discharge/charge cycles have also made these viable as power storage cells at emergency power stations for hospitals and computer installations, as well as in alarm systems. They are also used as storage cells for renewable energy sources, such as wind turbines and solar cells.
Although pure lead is very reactive, lead compounds, such as lead oxide, can by very stable, making them suitable as ingredients in corrosion resistant coating for iron and steel. Lead coatings are used to protect ship hulls, while lead stabilizers and sheathings are used to protect underwater power and communication cables.
Lead alloys are still used in some bullets and, due to the metal's low melting point, in metal solders. Lead glass has special applications in camera lenses and optical instruments, while lead crystal, which contains up to 36 percent lead, is used to create decorative pieces. Other lead compounds are still used in some paint pigments, as well as matches and fireworks.
Over the past 40 years, greater awareness about the negative health effects of lead has resulted in many countries banning numerous of lead products. Leaded fuel, which was widely used for much of the 20th century, is now banned in most developed countries. Similar bans exist for paints with lead pigments, lead fishing sinkers, and lead piping.
Street, Arthur. & Alexander, W. O. 1944. Metals in the Service of Man. 11th Edition (1998).
Watts, Susan. 2002. Lead. Benchmark Books.