Sir William Crookes
English physicist and chemist
June 17, 1832 - April 4, 1919

Born in England, Crookes entered the Royal College of Chemistry at the age of sixteeen. At the age of nineteen, he published his first paper, "On the Selenocyanides." Crookes started publication of Chemical News in 1859, acting as editor until 1906, and was a professor at the Royal College of Chemistry.

Using the spectroscope invented by Bunsen and Kirchoff, Crookes examined residues from a sulfuric acid plant for the presence of selenium and possibly tellurium. He found no spectral lines from tellurium, however. Instead he found a beautiful green line in the emission spectrum of the material. He concluded that this could only arise from a previously unknown element, and he named the element thallium, from the Greek meaning "green branch." He first announced his discovery in 1861 in the Chemical News.

Crookes also established the identity of the helium discovered by Ramsay as identical to that discovered by Lockyer in the sun, and studied radioactivity and rarified gases.