If you turn the wheel, a small flame immediately jumps up. Ideal for lighting candles and cigarettes. But why does this fire jump up from a lighter? By turning the small wheel, pieces of mischmetal break loose, an alloy of rare earth metals with pyrophoric properties. At room temperature, such material ignites spontaneously when exposed to air. A large component of this ‘flint’ is lanthanum.
Lanthanum falls into the rare-earth category, along with scandium, yttrium, and all the other lanthanides: the top of the two fold-out rows at the bottom of the periodic table. But the name rare earth is misleading. When the material was first mined, its scarcity was an assumption, but even the rarest rare earth, lutetium, is more abundant than gold. And lanthanum? It ranks 28th in the list of most common elements in the earth’s crust.
Read about rare earths: Is Europe’s green future in a Swedish mine? That remains to be seen
A silvery white substance
In 1803, the mineral cerite arrived at the lab where the Swedish physician and chemist Carl Gustaf Mosander worked. He did not spend much time on this mineral until it aroused his interest in 1839. Curious about its composition, he tried to dissect the rock and found a silver-white substance. Since the element had played hide and seek for some 36 years, he named it lanthanum, derived from the ancient Greek word for “to be hidden.” However, Mosander was in no hurry to publish. He insisted on purifying the substance first, keeping the element hidden from the rest of the world for another three years.
This was not due to ignorance of the chemist. Lanthanides are difficult to purify due to their close similarity in solubility. It was painstaking work: recrystallizing a thousand times to achieve a somewhat solid result. In 1923 it was only really possible to obtain lanthanum in pure form.
Lanthanum reacts easily with other substances and the element owes many of its applications to this. One of the first was the processing in the incandescent wicks of old-fashioned gas lamps. Since then, lanthanum can be found in TVs, fluorescent lamps and camera lenses, among other things.
Improve exhaust gases
Lanthanum, like other rare earth metals, is now important for the transition towards a greener car industry. In both normal, hybrid and hydrogen cars, the element matters. As a catalyst, lanthanum oxides improve exhaust gases by reducing nitrogen oxides (NOX) to nitrogen (N2) and CO in CO2. Nickel-metal hydride batteries, the most common batteries in hybrid cars, require kilos of lanthanum because the addition of lanthanum to an alloy provides increased capacity, strength and corrosion resistance. And lanthanum seems to be a panacea for hydrogen storage: an alloy together with nickel can store up to five hundred times its own volume of hydrogen, with the bonus that you can also easily extract the hydrogen from the foamy substance. Ideal for the fuel tank of hydrogen cars.
Thus, this once hidden element turns out to be a hidden force in the route to sustainability.