The metal that poisoned Ancient Rome
Lead is a malleable, low-melting metal of a silvery-white color with a bluish tinge. It is quite soft: it can be cut with a knife and scratched with a fingernail. It is a rather heavy metal, with a density of 11.3415 g/cm³ at 20 °С.
In nature this metal makes up 1.6•10⁻³ % of the mass of the earth’s crust, but is hardly ever encountered in its original form. Lead is a component of 80 minerals including galena PbS, cerussite PbCO₃ and anglesite PbSO₄ (lead sulfate).
Lead in history
Lead has been known since ancient times. The smelting of lead was once of the first metallurgical processes discovered by humanity. Perhaps this is why the origin of the name of this metal is lost in the depths of time.
The first items made of lead date from 6,400 BCE. In Ancient Egypt, a statue made of lead was found dating from 3,100 – 2,900 BCE. Additionally, the Ancient Egyptians used lead compounds as cosmetics. There are examples of the use of galena (lead sulfide), cerussite (lead carbonate) and phosgenite (lead carbonate with chlorine anions). Phosgenite is quite a rare mineral, and the Ancient Egyptians made it artificially.
The largest producer and consumer of lead in antiquity was the Roman Empire. Lead production reached 80,000 tons a year! The Ancient Romans mainly made pipes from it, as the metal was easy to roll and join. Additionally, dishes were made from lead. Lead was even added to wine to improve its taste! But Pliny and Vitruvius warned that lead could poison the body. Gradual poisoning from lead compounds caused a drop in fertility, and damaged the brain and nervous system. According to some theories, this was one of the factors that caused the fall of the Roman Empire.
In the Middle Ages, people continued to add lead to wine, causing epidemics of lead colic. In Ancient Russia, church roofs were covered in lead. The metal was also used to make bullets and shot. After the industrial revolution, lead was used increasingly for the manufacture of tins for food, printing type etc. Additionally, in 1921 the American engineer Thomas Midgley found that adding tetraethyl lead to petrol increased its octane level. Despite the toxicity of this fuel, it continued to be used for a long time. Its manufacture was ceased in the USA in 1986, and not until 2000 in EU countries.
Use of lead
Despite their toxicity, lead and its compounds have found wide application.
Chemical sources of electrical energy use lead bismuthate, sulfide and iodide, lead chloride, sulfate and lead dioxide
Radiation protection in nuclear reactors and medical devices (for protection from X-rays)
In electronics lead alloys are used as solders, for figure casting and the manufacture of ball bearings.
Lead chromate and basic lead carbonate carbonate Pb(OH)₂•PbCO₃ are yellow and white dyes respectively.
In geology, the content of lead isotopes in minerals is determined in order to establish their age. The stable isotope Pb-204 is both non-radiogenic (of a natural origin, not as the result of radioactive decay) and radiogenic (as the result of the decay of radioactive nuclei). The amount of radiogenic nuclei depends on time, so the summary content of lead isotopes in rock can give information about its age.
But nowadays, the use of lead is restricted in many ways because of its toxicity. Severe lead poisoning causes cramp, fainting, and pains in the stomach and joints. Lead accumulates in bones, and also in the liver and kidneys. Over a long time, lead causes damage to the nervous system, mental retardation (especially to children) and chronic brain diseases.
Beethoven is believed to have died from lead poisoning. This also caused the death of the British architectural expedition of John Franklin in 1845-1848.