August 27, 1875 – Paul E. Lecoq de Boisbaudran discovers gallium

Paul Émile Lecoq de Boisbaudran (1838-1912) discovered gallium (Ga), element number 31, by spectroscopy, by examining a zinc blende and two ultraviolet lines appearing, a spectral characteristic of this element. That same year, he isolated it by electrolysis of the hydroxide in a potassium hydroxide (KOH) solution and named it after his native Gallia, although its existence had been predicted in 1871 by Mendeleev, who called it eka-aluminium.

A soft, grayish metal in the liquid state that takes on a silvery hue when solidified, gallium is used in the construction of integrated circuits and in the manufacture of mirrors, glass, and ceramics. As a curiosity, gallium melts at temperatures close to room temperature and even, sometimes when held in the hand, below its melting point (28.56°C).

In an article published two years later in Annales de Chimie, Lecoq de Boisbaudran noted that his research had actually begun 15 years earlier, although he lacked the resources to carry it out.

In 1879, he was awarded the Royal Society's Davy Medal for his discovery.

Lecoq later discovered, using the same procedure, samarium (1880) and dysprosium (1886).