Carl Auer von Welsbach (1 September 1858 – 4 August 1929),[3] who received the Austrian noble title of Freiherr Auer von Welsbach in 1901,[4][5] was an Austrian scientist and inventor, who separated didymium into the elements neodymium and praseodymium in 1885. 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.[6]
He had a talent not only for making scientific advances, but also for turning them into commercially successful products. His work on rare-earth elements led to the development of the ferrocerium "flints" used in modern lighters, the gas mantle that brought light to the streets of Europe in the late 19th century, and the metal-filament light bulb.[7][8] He took the phrase plus lucis, meaning "more light", as his motto.[9]
Carl Auer von Welsbach | |
|---|---|
 | |
| Born | Carl Auer 1 September 1858 |
| Died | 4 August 1929 (aged 70) |
| Nationality | Austrian |
| Other names | Carl Freiherr Auer von Welsbach |
| Alma mater | University of Vienna University of Heidelberg |
| Known for | rare-earth elements discovery of praseodymium discovery of neodymium discovery of lutetium lighting improvements |
| Spouse(s) | Marie Anna Nimpfer[1] (1869–1950)[2]: 83 |
| Awards | Elliott Cresson Medal (1900) Wilhelm Exner Medal (1921) |
| Scientific career | |
| Fields | Chemistry |
| Doctoral advisor | Robert Bunsen |
https://en.wikipedia.org/wiki/Carl_Auer_von_Welsbach
Ferrocerium is a synthetic pyrophoric alloy that produces hot sparks that can reach temperatures of 3,000 °C (5,430 °F) when rapidly oxidized by the process of striking the rod, thereby fragmenting it and exposing those fragments to the oxygen in the air. This property allows it to have many commercial applications, such as the ignition source for lighters (where it is often known by the misleading name "flint"), strikers for gas welding and cutting torches, deoxidization in metallurgy, and ferrocerium rods (also called ferro rods, flint-spark-lighters and wrongly "flint-and-steel" as this is the name of a different type of lighter using a section of high carbon steel and a natural flint). Due to ferrocerium's ability to ignite in adverse conditions, rods of ferrocerium are commonly used as an emergency combustion device in survival kits.[1]
Ferrocerium was invented in 1903 by the Austrian chemist Carl Auer von Welsbach. It takes its name from its two primary components: iron (from Latin: ferrum), and the rare-earth element cerium.[2] The pyrophoric effect is dependent on the brittleness of the alloy and its low autoignition temperature.[3]
It is also known in Europe as Auermetall after its inventor Baron Carl Auer von Welsbach. 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 the Baron von Welsbach's first alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium".
A modern ferrocerium firesteel product is composed of an alloy of rare-earth metals called mischmetal (containing approximately 20.8% iron, 41.8% cerium, about 4.4% each of praseodymium, neodymium, and magnesium, plus 24.2% lanthanum.[4]) A variety of other components are added to modify the spark and processing characteristics.[1] Most contemporary flints are hardened with iron oxide and magnesium oxide.
| Element | Iron | Cerium | Neodymium | Praseodymium | Magnesium | Lanthanum |
|---|---|---|---|---|---|---|
| Fraction | 20.8% | 41.8% | 4.4% | 4.4% | 4.4% | 24.2% |
The rare-earth elements, also called the rare-earth metals or (in context) rare-earth oxides, or the lanthanides (though yttrium and scandium are usually included as rare-earths) are a set of 17 nearly-indistinguishable lustrous silvery-white soft heavy metals.[1] Scandium and yttrium are considered rare-earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties, but have different electronic and magnetic properties.[2][3]
The 1985 International Union of Pure and Applied Chemistry "Red Book" (p. 45) recommends that lanthanoid is used rather than lanthanide. The ending "-ide" normally indicates a negative ion. However, owing to wide current usage, "lanthanide" is still allowed and is roughly analogous to rare earth element.
In pure form, these metals tarnish slowly in air at room temperature, and react slowly with cold water to form hydroxides, liberating hydrogen. They react with steam to form oxides, and at elevated temperature (400 °C) ignite spontaneously and burn with a fierce colorful pyrotechnic flame.
These elements and their compounds have no known biological function. The water-soluble compounds are mildly to moderately toxic, but the insoluble ones are not.[4]
The rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes, but since they do not occur as base metals or in lump or visible quantities like iron or aluminum, their names and properties are unfamiliar in everyday life. One of the most familiar may be unusually powerful neodymium magnets sold as novelties.
Despite their name, rare-earth elements are relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68 parts per million, more abundant than copper. All isotopes of promethium are radioactive, and it does not occur naturally in the earth's crust; however, a trace amount is generated by decay of uranium 238. They are often found in minerals with thorium, and less commonly uranium. Because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated in rare-earth minerals. Consequently, economically exploitable ore deposits are sparse (i.e. "rare").[5] The first rare-earth mineral discovered (1787) was gadolinite, a black mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from a mine in the village of Ytterby in Sweden; four of the rare-earth elements bear names derived from this single location.
According to chemistry professor Andrea Sella, rare-earth elements differ from other elements, insofar that "rare-earth metals, when looked at anatomically, seem to be inseparable from each other, in that they are all almost exactly the same in terms of their chemical properties. However, in terms of their electronic properties, their magnetic properties, each one is really exquisitely unique, and so it can occupy a tiny niche in our technology, where virtually nothing else can."[2] For example, "the rare-earth elements praseodymium (Pr) and neodymium (Nd) can both be embedded inside glass and they completely cut out the glare from the flame when one is doing glass-blowing."[2]
https://en.wikipedia.org/wiki/Rare-earth_element
No comments:
Post a Comment