Element of the Month October: Lead
Lead is the heaviest stable element in the periodic table. The three lead isotopes 206Pb, 207Pb and 208Pb are end products of the three natural decay series. They are therefore found quite frequently in the earth’s crust.
Freshly cut, lead is silver, metallic. When exposed to air, a dull, bluish-white oxide layer, also known as lead ash, quickly forms. As a finely dispersed powder, lead is self-igniting even at room temperature.
Lead is classified as mineral, but it rarely occurs in native form. It is found in many regions of the world, from Finland to Germany to Italy. The largest deposits in Europe are located in Sweden and Poland. The best-known lead ore is galena (PbS). But there are other naturally occurring minerals, including cerussite, crocoite, and anglesite. Thanks to the relatively closed material chain, the largest source of lead is recycling.
Toxicity of lead
Elemental lead is non-toxic to humans in compact form. Since lead forms a dense, poorly water-soluble protective layer when exposed to air, hazardous substance labelling can be dispensed with. Dissolved lead and lead compounds, as well as lead dust, are considered toxic if they are inhaled or swallowed. Caution should also be exercised with organo-lead compounds, such as tetraethyl lead. These are highly lipophilic and are rapidly absorbed through the skin.
A single intake of metallic lead is only noticeable at really high doses. However, steadily ingested, small amounts of lead accumulate in the body and are deposited, for example, in the bones. Chronic lead poisoning is manifested by headaches, fatigue, weight loss, defects in blood formation, nervous system and muscles. The toxicity of lead is due to a disruption of hemoglobin synthesis.
Lead inhibits several enzymes at the same time and interferes with the incorporation of iron into the hemoglobin molecule. As a result, the oxygen supply to the body’s cells is no longer secured.
Use of lead from the Bronze Age to the present
Lead has been used since the early Bronze Age. Both for the production of everyday objects and in the form of slingshot projectiles and, from the Roman Empire until the 70s, for the production of water pipes.
Today, around 60% of the amount of lead mined is used for lead-acid batteries. Other areas of application include alloys, radiation protection (X-rays) and processing in the construction industry.
Of particular importance for current research are perovkites: a class of compounds containing lead ions. These are being discussed as next-generation solar cells as well as for applications as light-emitting field-effect transistors.
In addition, further physical investigations into the mechanisms of optical and electronic, macro- and microscopic processes are investigated. The use of these compounds for the construction of near-band X-ray lasers is also being examined.