Unlike many other notable scientists of the past, Karl Auer had the benefit of a good education, thanks to his father's well-paid position as director of Austria's Imperial Printing Press. After studying at the Vienna Polytechnic, Auer trained in Heidelberg under Robert Bunsen (who later invented the famous Bunsen burner). There Auer grew interested in the rare earth elements, which led to his discovery of two new metals, neodymium and praseodymium.

Auer's devotion to this class of elements had many practical results. By the late 1800s, gas made from coal had become a common source of light in towns and cities. Although gaslight was an enormous improvement over candles and lamps, Auer came up with an idea that would enable gas flames to give off much more light. He noticed that certain rare earth metals would glow brilliantly when heated by a gas flame. In 1885, after testing several...