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 ofAustria's Imperial Printing Press. After studying at the Vienna Polytechnic,Auer trained in Heidelberg under Robert Bunsen (who later invented the famousBunsen burner). There Auer grew interested in the rare earth elements, whichled to his discovery of two new metals, neodymium and praseodymium.
Auer's devotion to this class of elements had many practical results. By thelate 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 substances, he invented the incandescent gas mantle--a cylindrical shell that glows with a bright white light when placed over a gas flame. These mantles were made by soaking a piece of cotton in a metal salt solution (99 % thorium and 1 % cerium), then burning off the fabric to leave a shell of incandescent metal oxide.
Auer's invention could not have been better timed for the gaslight industry.Electric lights were just being introduced, but the early models produced a relatively feeble light, comparable to old-fashioned gaslights. Auer's mantlegave gas lighting the edge it needed to compete with electric lights for manyyears.
However, Auer was a true scientist and did not take sides in the war betweengaslight and incandescent electric light. In 1898, to improve the electric bulb, Auer invented a filament made of osmium--one of his beloved rare earth metals--to replace the carbon filaments then in use. Although this metal was too expensive for commercial bulbs, Auer had paved the way for development of metallic filaments. Within a decade, an American chemist, Irving Langmuir, hadinvented the tungsten filament, which is still used in today's bulbs.
Also, around 1900, Auer invented an alloy called misch metal to replace flintin sparking devices such as cigarette lighters. Auer's misch metal contained, of course, rare earth elements, notably cerium. At the time, cerium was being dumped in factory yards and given away free with other elements, so Auer was trying to find a practical use for it. His invention represented the firstimprovement on the prehistoric method of sparking with flint and steel. Modern "flint-ignited" lighters actually use misch metal instead of true flint.
Auer's interest in lighting and, specifically, in rare earth metals, dominated his scientific career. When he was elevated to the Austrian aristocracy in1901, he chose the words " more light" as his baronial motto.