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Lead - An Introduction

Updated by Reginald Davey 31/08/22

Lead (Pb) has existed for several thousand years from the times of Exodus. According to alchemists, lead is the oldest metal that is associated with the planet Saturn.

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Lead: Historical and Modern Uses

Lead has been utilized for millennia due to its beneficial properties in a multitude of industries. In ancient times, the Romans used this natural resource widely in piping to deliver water to their population as well as for underfloor hypocausts. It was used as a glaze for pottery, as well as in ancient Egypt for darkening their eyelids in a cosmetic known as Kohl.

Before the twentieth century, lead was used primarily in countries such as the United States for burial vault liners, ammunition, leaded glass, ceramic glazes, protective coatings, and water pipes. Over the course of the twentieth century, lead demand increased with the spread of automobiles, lead shielding in medical devices and nuclear reactors, and its use in gasoline. Today, lead is mined globally, with vast amounts extracted from ore veins annually.

Since the latter part of the 20th century, environmental and health concerns have led to changing uses of lead, with its removal from gasoline and from piping. Today, lead is primarily used in lead-acid batteries, ammunition, lead oxides for the ceramics and glass industry, sheet lead, casting materials, and lead shielding for applications such as nuclear reactors and X-ray machines.

Material Properties of Lead 

Lead possesses numerous properties which make it suitable for a wide array of industrial and commercial purposes. Lead density is higher than that of most other common metals, and it is soft, malleable, and has a low melting point. When freshly cut, it is silvery blue in color, which tarnishes to dull gray upon exposure to air. High lead density is due to its high atomic weight and tightly packed cubic structure.

An extremely soft metal, it is possible to scratch lead with a fingernail. The maximum bulk modulus of this metal is 45.8 MPa, which is lower than other common engineering metals, making it easier to compress. Lead has a lower tensile strength than metals such as aluminum and copper. Adding antimony or copper in small amounts can strengthen this material.

The melting point of lead is 595-601 Kelvin, with a minimum service temperature of 0 K and maximum service temperature of 323 K. Additionally, lead has the lowest boiling point of all carbon group elements. Additionally, the electrical resistivity of lead is higher than that of other industrial metals, almost by an order of magnitude. It is a superconductor at extremely low temperatures (<7.19 K.)

The surface of lead gets oxidized, making it highly resistant to corrosion. Even though lead gets dissolved in nitric acid, it does not dissolve in hydrochloric or sulfuric acid. Therefore, it is regarded as one of the most stable metals.

Natural lead is a blend of four stable isotopes : 208Pb (52.3%), 206Pb (23.6%), 207Pb (22.6%), and 204Pb (1.48%). Isotopes of lead are the result of each three series of naturally existing radioactive elements. They are 208Pb for the thorium series, 206Pb for the uranium series, and 207Pb for the actinium series. There are 27 other radioactive isotopes of lead.

Due to its ability to capture neutrons and gamma rays, lead is widely used as radiation shielding.

Occurrence

Although lead occurs as such in nature, it is rare. Lead is chiefly obtained from galena (PbS) through the process of roasting. Cerussite (PbCO3), minium (Pb3O4), and anglesite (PbSO4) are the common minerals in which lead can be found.

Environmental Properties

Lead resists several environmental effects very well, with the exception of oxidation at high temperatures. This has made the material extremely attractive for multiple applications.

Applications

Metallic lead can be used in the following applications:

  • Ammunition
  • Storage batteries
  • In storage tanks, pipes, gutters, fittings, flashing, and roofing in plumbing
  • Bearing metals and solders
  • Cable coverings for power lines and telephone line to avoid mechanical injury
  • Collapsible piping
  • Automotive fuel tanks to protect against corrosion (Terneplate)
  • Locomotive crosshead linings (Dandelion metal), machine bearings (Hoyt metal), and railway car bearings (lining metal)
  • As a vibration and sound absorber
  • Manufacture of lead tetraethyl
  • As an alloying element to enhance certain mechanical properties like elongation, hardness, and tensile strength
  • Toys, small moldable articles
  • Radiation shielding, used around X-ray equipment and nuclear reactors, in the form of neoprene-lead fabric, paints (Chemtree 82), ceramic mortars, shielding cements, and other plastic composite structures.

Compounds of lead are used in the following areas:

  • Lead dioxide or lead peroxide (PbO2) is a brown powder used in dyes, matches, as an oxidizing agent, and as a mordant in pyrotechnics.
  • Pigments for paints, for example, PbCrO4 or yellow chrome, 2PbCO3.Pb(OH)2 or white lead, PbWO4 or lead tungstate (a yellow pigment), and Pb3O4 or red lead.
  • Lead meta-silicate (PbSiO3) is a white crystal used for fireproofing textiles and glazing ceramics.
  • Due to its sensitivity to heat rays, lead sulfide (PbS) can be used as a filler in missiles.
  • Lead oxide is used to manufacture fine crystal glass and flint glass, as a filler in rubbers, and for achromatic lenses.

Health Problems Associated with Lead

Due to the harmful effects on human health, lead requires stringent environmental and handling controls. Lead poisoning can cause severe health problems due to its extreme toxicity when inhaled or swallowed. There is no safe level of lead exposure, and lead has no known biological role.

Lead causes damage to almost every organ and biological system and can cause adverse mental health outcomes for patients. Continuous exposure can lead to bioaccumulation. Lead interferes with the actions of enzymes by binding to active sites and mimicking and displacing beneficial molecules such as calcium and iron. Severe brain damage can occur due to lead’s ability to cross the blood-brain barrier.

Many other harmful health effects occur when the human body is exposed to lead. This is a global issue due to the prevalence of lead mining, battery manufacture, environmental disposal of lead-containing materials and devices, and battery recycling, which is performed in unsafe conditions in developing nations.

In Summary

Lead is an eminently useful industrial material that is utilized in vast amounts globally. Beneficial properties such as high lead density and good passivity make it suitable for multiple products. However, lead requires specific, tightly regulated environmental and workplace controls due to its extreme toxicity even at relatively small concentrations.

Further Reading and More Information

Kropschot, S.J & Doesbrich, J.L (2011) Uses of Lead [online] geology.com. Available at:

https://geology.com/usgs/lead/

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Reginald Davey

Written by

Reginald Davey

Reg Davey is a freelance copywriter and editor based in Nottingham in the United Kingdom. Writing for AZoNetwork represents the coming together of various interests and fields he has been interested and involved in over the years, including Microbiology, Biomedical Sciences, and Environmental Science.

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