He was also one of three scientists to independently discover the element lutetium (which he named cassiopeium), separating it from ytterbium in 1907, setting off the longest priority dispute in the history of chemistry.

His father, ennobled in 1860 (as Alois Ritter Auer von Welsbach),[10] was director of the Imperial printing office (K.-k. Hof- und Staatsdruckerei) in the days of the Austrian Empire.

[11] In 1878, Auer entered the University of Vienna, studying mathematics, general chemistry, engineering physics, and thermodynamics.

[2]: 132 [11] In 1885, Auer von Welsbach used a method of fractional crystallization that he had developed himself to separate the alloy didymium into its two parts, for the first time.

[2]: 69 In 1890 he introduced a new form of the mantle based on a mixture of 99% thorium dioxide and 1% cerium(IV) oxide, which he developed in collaboration with his colleague Ludwig Haitinger.

Another company founded to produce the newer design was formed in 1891, working with fellow student from the university Ignaz Kreidl, and the device quickly spread throughout Europe.

[27][28] Auer von Welsbach then started work on development of metal-filament mantles, first with platinum wiring, and then osmium.

[2]: 105–111 [6] In 1903 Auer von Welsbach won another patent for a fire striker ("flint") composition named ferrocerium.

Three different Auermetalls were developed: the first was iron and cerium, the second also included lanthanum to produce brighter sparks, and the third added other heavy metals.

In Auer von Welsbach's first alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium".

[31]: 190  In 1910, one of his companies helped to establish Vienna as a center of radiation research by producing the first major quantity of radium chloride (3-4 grams) in Europe.

[32] Between 1907 and 1918, Auer von Welsbach focused on isolating preparations of actinium and thorium as by-products of radium extraction.

[31]: 218–219 He kept up an active correspondence with physicist Stefan Meyer, managing director of the Institute for Radium Research, Vienna, to discuss the extraction of actinium.

[11][33] The following photographs show scientific equipment from Auer von Welsbach's laboratory, from "Spektroskopische Methoden der analytischen Chemie" (1922).

[33] In 2008 (150 years after his birth), Auer von Welsbach was selected as a main motif for a high-value collectors' coin: the Austrian €25 Fascination Light.