iron

History

The Iron Age began around 1200 BC, but the first iron used was from meteorites. Smelting iron from ore was learned by the Hittites in Asia Minor. In 1747, French physician Pierre Menard de la Grosse proved the presence of iron in blood, and a century later Henry Bessemer invented the converter for mass steel production.

How it works

In a blast furnace, resembling a red-hot volcano, iron oxides are reduced by carbon—coal 'takes away' oxygen, leaving pure metal. In our body, iron, changing its charge, 'charges' with oxygen in the lungs and 'discharges' in tissues, like a battery ensuring continuous respiration.

History

The Iron Age began around 1200 BC, but the first iron used was from meteorites. Smelting iron from ore was learned by the Hittites in Asia Minor. In 1747, French physician Pierre Menard de la Grosse proved the presence of iron in blood, and a century later Henry Bessemer invented the converter for mass steel production.

How it works

In a blast furnace, resembling a red-hot volcano, iron oxides are reduced by carbon—coal 'takes away' oxygen, leaving pure metal. In our body, iron, changing its charge, 'charges' with oxygen in the lungs and 'discharges' in tissues, like a battery ensuring continuous respiration.

History

Iron smelting began in Anatolia around 1500 BC. Meteoritic iron was used as early as the 4th millennium BC. In 1747, Menard de la Grosse discovered iron in blood ash. In 1932, Hans Fischer deciphered the structure of heme. Iron's magnetism was studied by Gilbert (1600), but only Maxwell (1873) gave a rigorous theory of the electromagnetic field, explaining ferromagnetism as the result of microscopic currents.

How it works

Ferromagnetism of iron is due to exchange interaction, aligning the spins of unpaired d-electrons. This creates macroscopic domains that reorient in an external field. According to Maxwell's equations for media with magnetic hysteresis, the hysteresis loop determines the coercive force and remanent magnetization. Upon heating above the Curie point, thermal fluctuations destroy magnetic order (Boltzmann statistics). In biology, oxidation of Fe²⁺ to Fe³⁺ allows cytochromes to transfer electrons in the respiratory chain.

Open problems & fun facts

Understanding the exact mechanism of iron crystallization in the Earth's inner core to predict the evolution of the magnetic field; Development of rare-earth-free permanent magnets based on iron with specified coercivity; Overcoming the toxicity of free iron when creating drugs for treating anemia

💡 Pure iron is soft: its hardness on the Mohs scale is only 4 out of 10. But adding 0.5% carbon yields steel that cuts glass. And the Earth's core is a solid iron ball the size of the Moon, heated to 5500°C, rotating inside a liquid outer core, creating the planet's magnetic field.