William Crookes isolates thallium metal in 1862…

William Crookes isolates thallium metal in 1862 (on March 10) as, independently, does French chemist Claude-August Lamy.

The researchers had expected to isolate tellurium after removing selenium from the byproducts, but instead have found the new element by observing the prominent green spectral line generated by selenium-bearing pyrites that have been used in the manufacture of sulfuric acid.

The element's name derives from Greek thallos, a young, or green, twig or shoot, after the color of the elements spectral line signature and the bright green color it imparts to flames.