This Day in Chemistry: Paul-Émile Lecoq de Boisbaudran

18th April 2018

Chemistry

On 18th April, 1838, in Cognac, France, Paul-Émile Lecoq de Boisbaudran was born. Most commonly known for his work in spectroscopy, de Boisbaudran was a French chemist who discovered the elements samarium, dysprosium, europium and gallium.

De Boisbaudran shows that you don’t always have to attend formal schooling to become an industry-leading academic. This key figure, who played an important role in our understanding of rare earth elements and the acceptance of the periodic table, was actually self-taught.

Whilst working in his family’s new wine business, de Boisbaudran began reading the syllabus of the École Polytechnique, pursuing scientific topics. These led him to repeat the experiments he read about in a laboratory he fitted himself. What started out as a tickling curiosity eventually led to important discoveries that helped shape the world of chemistry.

An infographic showing the achievements of French chemist, Paul-Émile Lecoq de Boisbaudran

Spectroscopy

De Boisbaudran is widely noted for his work in spectroscopy, which he used to analyse the spectra of 35 elements. This was important because it led him to the discovery of several rare earth metals.

In science, spectroscopy is used to study and measure the relationship between matter and electromagnetic radiation. When these two interact, they produce a spectrum of visible light which can then be measured.

De Boisbaudran used spectroscopy to analyse the spectra of 35 elements. He did this by using a Bunsen burner – and sometimes an electric spark – to encourage luminescence. Through this method, he discovered several new elements. These included samarium, dysprosium, europium, and most significantly, gallium.

A prism

De Boisbaudran was best known for his work in spectroscopy, which he used to analyse over 35 elements. He talks about this in his 1874 book ‘Spectres Lumineux.’

Gallium

In 1875, de Boisbaudran was examining a sample of sphalerite, also known as zinc blende, when he observed its now-characteristic spectrum: two violet lines.

After isolating the metal, de Boisbaudran named the resulting element Gallia, drawing from the Latin word for France to nod towards his native homeland. This later became gallium (Ga).

However, although de Boisbaudran identified and isolated gallium, it was Dmitri Mendeleyev who predicted its existence.

Mendeleyev, the father of the periodic table, predicted that an element positioned below aluminium in the table would come into existence in the future. He referred to this undiscovered element as eka-aluminium, which is Sanskrit for beyond aluminium.

According to Mendeleyev, eka-aluminium would have several distinctive properties, including a low melting point and high density. He also predicted its atomic mass.

In 1875, after de Boisbaudran had isolated and discovered gallium, he realised that its properties were virtually identical to those predicted by Mendeleyev. Through spectroscopy, de Boisbaudran had uncovered Mendeleyev’s prediction, and eka-aluminium became gallium.

This was not only an important breakthrough for de Boisbaudran, it was also a crucial moment for Mendeleyev and his periodic table. By validating Mendeleyev’s predictions, de Boisbaudran brought a crucial turning point that led to the wide acceptance of the periodic table.

Crumpled sheet of silver

De Boisbaudran discovered gallium in 1875. As one of the elements predicted by Mendeleyev, this discovery led to the general acceptance of the periodic table by validating Mendeleyev’s predictions.

Discovering Rare Earth Metals

Spectroscopy not only led de Boisbaudran to discover gallium, it also allowed him to identify several other rare earth metals.

In 1879, he discovered samarium (Sm) when he isolated it as an oxide from the mineral samarskite and noticed its sharp optical absorption lines.

De Boisbaudran also spectroscopically identified europium (Eu) in 1890 when he saw that fractions obtained from samarium-gadolinium concentrates had spectral lines that were not created by samarium or gadolinium.

Perhaps his most trying discovery was dysprosium (Dy). The French chemist first discovered dysprosium as an impurity in erbium oxide. While de Boisbaudran knew he had a new element on his hands, it was a challenge to separate it out.

De Boisbaudran employed precipitation using ammonia, and it took him over 30 tries to get a sample of the element. Finally, in 1886, his efforts paid off and he was able to separate the element. Because of this struggle, he called it dysprosium after the Greek word for ‘hard to get’ – dysprositos.

Periodic table

Paul-Émile Lecoq de Boisbaudran discovered several rare earth metals, including samarium, dysprosium and europium. He also uncovered one of Mendeleyev’s predicted elements, gallium.

De Boisbaudran’s use of spectroscopy to identify these elements – as well as his many other achievements – eventually led him to be awarded with the Davy Medal for his scientific work in 1879.

At ReAgent, we sometimes use spectroscopy in the chemical analysis of our products, including our purified water. We also use spectrophotometry to identify the presence of impurities, such as silica, in our water to ensure absolute purity.

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