Zinc Zn

Discovery

Zinc was used in alloys long before it was recognised as a metal in its own right. Brass, an alloy of copper and zinc, was made in antiquity by heating copper with zinc ores such as calamine; the Romans produced it on a large scale for coins and ornaments.

Metallic zinc is tricky to produce because it boils at a relatively low temperature and escapes from a furnace as vapour. Metallurgists in India solved this by distillation: at Zawar in Rajasthan, zinc was smelted on a large scale in the medieval period using clay retorts turned upside down. China was producing zinc in quantity by the sixteenth and seventeenth centuries, and it was exported to Europe.

In Europe, William Champion patented a zinc smelting process at Bristol in 1738. In 1746 the German chemist Andreas Sigismund Marggraf isolated zinc by heating calamine with carbon in closed vessels and described its properties systematically, and he is often credited with its discovery in Europe.

Origin of the name

The name comes from the German Zink, used by the sixteenth-century physician Paracelsus. Its origin is uncertain; one suggestion links it to Zinke or Zinken, meaning a prong or tooth, from the jagged appearance of zinc crystals. The symbol is Zn.

Main uses

• Galvanising: about half of all zinc is used to coat steel, which protects it by corroding first, even where the coating is scratched.
• Alloys: brass, and zinc die-casting alloys for car parts, locks and hardware.
• Batteries: zinc is the anode in alkaline and zinc–carbon batteries and in zinc–air cells for hearing aids.
• Zinc oxide: it activates rubber vulcanisation and is used in sunscreens, ointments and paints.
• Agriculture and coins: zinc is a micronutrient added to fertilisers and feed, and the United States cent has been made mostly of zinc since 1982.

Isotopes

Zinc has five naturally occurring isotopes: zinc-64 (about 49 percent), zinc-66 (about 28 percent), zinc-67, zinc-68 (about 19 percent) and zinc-70. Zinc-70 may undergo extremely slow double beta decay, but for all practical purposes all five are stable. The radioactive zinc-65, with a half-life of about 244 days, is used as a tracer in studies of metabolism and metal wear.

In everyday life

Zinc is essential for immune function, wound healing, growth and the sense of taste and smell. It is found in oysters, red meat, seeds, nuts and legumes. Zinc deficiency is widespread in parts of the developing world and contributes to child illness.

Too much zinc from supplements can interfere with copper absorption. Welders who breathe fumes from galvanised steel can develop metal fume fever, a flu-like illness.