Carl Auer von Welsbach

Carl Auer von Welsbach (1858–1929) was an Austrian chemist and inventor who separated ytterbium into the elements later named ytterbium and lutetium, which he called cassiopeium.

Lutetium: Lutetium is the chemical element with atomic number 71, a dense silvery metal in the lanthanide series. Auer named this element cassiopeium after separating it from ytterbium.
Fractional crystallization: Fractional crystallization separates substances by repeatedly crystallizing them from solution according to differences in solubility. Auer used repeated fractionation to concentrate the components of ytterbia.
Robert Bunsen: Robert Bunsen was a German chemist known for laboratory methods, spectroscopy, and the Bunsen burner. Auer studied under Bunsen at Heidelberg, where he developed his expertise in analytical chemistry.
Gas mantle: A gas mantle is a heat-resistant mesh that emits visible light when heated by a fuel flame. Auer's mantle made gas lighting substantially brighter by exploiting rare-earth oxides.
Periodic table: The periodic table arranges chemical elements by atomic number and recurring chemical properties. Separating lutetium helped clarify the membership and ordering of the rare-earth elements.
Ytterbium: Ytterbium is the chemical element with atomic number 70, a soft silvery metal in the lanthanide series. Auer began with material then believed to be a single element and separated lutetium from it.
Rare-earth separation: Rare-earth separation is the chemical isolation of individual rare-earth elements from mixtures with similar properties. Auer's work was an early example of the painstaking separation methods the field required.
Jean Charles Galissard de Marignac: Jean Charles Galissard de Marignac was a Swiss chemist whose work included the discovery of ytterbium and gadolinium. Marignac's identification of ytterbia supplied the starting point for Auer's later separation.
Gas lighting: Gas lighting produces illumination by burning manufactured or natural gas in lamps. The mantle was Auer's most influential contribution to nineteenth-century gas lighting.
Lutetium-176: Lutetium-176 is a naturally occurring radioactive isotope of lutetium with a half-life of about 38 billion years. The element Auer isolated later became useful in geochronology through this long-lived isotope.

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