Tungsten W

Discovery

In 1781 the Swedish chemist Carl Wilhelm Scheele obtained a new acid, tungstic acid, from a mineral then called tungsten and now known as scheelite. He could not isolate the metal itself.

In 1783 the Spanish brothers Juan José and Fausto Elhuyar obtained the same acid from wolframite and reduced it with charcoal, isolating metallic tungsten for the first time; they are generally credited with the discovery. In the early twentieth century William Coolidge developed a way to make tungsten ductile enough to draw into fine wire, and tungsten-filament lamps soon replaced earlier designs.

Origin of the name

Tungsten means "heavy stone" in Swedish. The symbol W comes from the German name Wolfram; a widely told explanation is that tin smelters said the mineral "devoured" tin like a wolf, lowering their yield. Many languages, including German and Swedish, still call the element wolfram.

Main uses

• Cemented carbide: tungsten carbide bound with cobalt is nearly as hard as diamond and is used for cutting tools, drill bits and mining equipment, the largest single use of tungsten.
• High-temperature parts: filaments in incandescent and halogen lamps, X-ray tube electrodes, TIG welding electrodes and plasma-facing components (divertors) in fusion reactors.
• Heavy alloys: counterweights, vibration weights, balancing masses and radiation shielding.
• Tool steels: tungsten keeps high-speed steels hard at cutting temperatures.

Isotopes

Natural tungsten has five isotopes (180, 182, 183, 184 and 186), with tungsten-184 the most abundant. Tungsten-180 has been found to undergo alpha decay with an extraordinarily long half-life. Tungsten-182 is produced by the decay of hafnium-182, which lets scientists use the hafnium-tungsten system to date the formation of planetary cores.

In everyday life

The Sangdong mine in Yeongwol, South Korea, was once among the world's largest tungsten mines and a major export earner for the country in the 1950s and 1960s. Because tungsten is almost exactly as dense as gold, counterfeit gold bars with tungsten cores are occasionally discovered. Some bacteria and archaea use tungsten in their enzymes, making it the heaviest element known to be used by living things. Solid tungsten has low toxicity, but dust from machining should not be inhaled.