Lanthanum

Lanthanum was discovered by Swedish chemist Carl Gustaf Mosander in 1839, in a sample of a mineral called cerite. But this discovery took a lot of patience!

In the 1820s, Mosander suspected that a sample of cerite he’d gotten from his mentor, legendary Swedish chemist Jöns Jacob Berzelius, might contain a new element. However, in the early 1820s, there was only one known source of cerite—a mine in Bastnäs, Sweden—which meant that supplies of the mineral were limited. Unfortunately, Mosander ran out of the mineral, which meant that he had to give up his quest for the new element for more than a decade.

In 1839, Mosander acquired more cerite and resumed his research. Ultimately, he succeeded in finding a new element in the mineral. But he was reluctant to announce his discovery, because he didn’t want to embarrass his mentor, Berzelius, who’d failed to find the element first. Finally, Mosander overcame his shyness and told Berzelius about the discovery. Berzelius suggested calling the new element “lanthan,” which came from the Greek word lanthanein, meaning “to lie hidden.”

Mosander still wasn’t sure that he’d completely separated the new element from his cerite, so he waited until 1840 to publish his results. By the time he officially announced lanthanum’s discovery, he’d further broken down the cerite into oxides that later yielded the new elements praseodymium and neodymium. In chemistry, it pays to be thorough!

Lanthanum is a rare earth metal that’s soft, silver, and ductile (meaning that it can be stretched) and malleable (meaning it can be hammered or shaped). Lanthanum is a lot more reactive than the other lanthanides—douse it with water, and it will give off hydrogen gas. Lanthanum metal is soft enough to be cut with a knife!

Hollywood owes lanthanum a thank you: Because the element produces an emissions spectrum like sunlight, it’s often used in photographic and film studio lighting.

Camera lenses also often contain lanthanum, which can improve the glass’s color spectrum. Because lanthanum nickel absorbs hydrogen gas—as a powder the compound can absorb up to 400 times its own volume in hydrogen—lanthanum nickel can be used to store hydrogen, which can make it useful for things like hydrogen-powered cars.

Lanthanum nickel does a great job of absorbing hydrogen, which makes it useful in things like hydrogen-powered cars. Hybrid cars also use lanthanum in their batteries. Up to 40% of all lanthanum oxide gets mixed into optical glass, which is in turn used in things like cameras and binoculars. Mischmetal alloy, which contains lanthanum, can be used to create sparks in lighters.

In nature, you’ll find lanthanum either as lanthanum-139 or lanthanum-138. But you’d have to look hard to find lanthanum-138. More than 99.9% of naturally occurring lanthanum is lanthanum-139. Both isotopes are stable (non-radioactive). Synthetic lanthanum radioisotopes generally have a half-life of less than one minute (although lanthanum-137 has a half-life of around 60,000 years).

It’s a lot easier to find lanthanum today than it was in Mosander’s day! Most lanthanum comes from monazite and bastnäsite, which can be up to 25% and 38% of the mineral, respectively. Most lanthanum ores come from the United States, Brazil, India, Sri Lanka, and Australia. About 12,500 metric tons of lanthanum are produced each year.