Gadolinium Gd

Discovery

In 1880 the Swiss chemist Jean Charles Galissard de Marignac spotted spectral evidence of a new element in rare-earth oxides obtained from minerals such as gadolinite. In 1886 Paul-Émile Lecoq de Boisbaudran in France purified the oxide further and gave the element its name.

Pure gadolinium metal only became available in the twentieth century. Research in the 1930s showed that it becomes ferromagnetic below about 20 °C (293 K), a property otherwise found among the elements mainly in iron, cobalt and nickel.

Origin of the name

The element takes its name from the mineral gadolinite, which honours the Finnish chemist Johan Gadolin. In 1794 Gadolin isolated yttria, the first rare-earth oxide, from a mineral found at Ytterby in Sweden, and he is often called the father of rare-earth chemistry.

Main uses

• MRI contrast: gadolinium ions wrapped in chelating molecules are injected into the bloodstream, where they change the magnetic relaxation of nearby water and make blood vessels and tumours stand out.
• Nuclear engineering: gadolinium-157 has the largest thermal-neutron capture cross-section of any stable nuclide. Gadolinium oxide is mixed into some fuel as a "burnable poison" to tame reactivity early in a fuel cycle.
• Neutron detection: Japan's Super-Kamiokande detector dissolved a gadolinium compound in its water to capture neutrons more efficiently.
• Magnetic cooling: its large magnetocaloric effect makes it a model material for refrigeration without conventional refrigerant gases.

Isotopes

Natural gadolinium contains seven isotopes. Gadolinium-152 is radioactive with an extremely long half-life; the rest are stable. Gadolinium-155 and gadolinium-157 do most of the neutron absorbing. Artificial gadolinium-153, with a half-life of about 240 days, has been used as a radiation source in bone-density scanners.

In everyday life

If you have had a contrast-enhanced MRI, you have probably been injected with gadolinium. Most of it leaves the body in urine within a day or so, but in people with severe kidney disease a rare condition called nephrogenic systemic fibrosis has been linked to some agents, so kidney function is checked beforehand. Studies have also found traces retained in the brain after repeated doses, so doctors use these agents only when they add diagnostic value. Decisions about contrast should always be made with a medical professional.