Yttrium history

Smith Hopkins, 1935 very pure. (Gadolin 1794, 1796 Weeks 1968) (http //www.rsc.Org/periodic-table/element/39/yttrium history)... 

Mineral sources, lanthanide and yttrium distribution in, 14 6311 Mineral spirits, solvent for cosmetics, 7 832 Minerals processing, history of, 16 596t. 

Reiterating, the phosphatic mineral of such phosphorites is essentially francolite, a carbonate fluorapatite of somewhat variable composition (McConnell, 1971 Rooney and Kerr, 1967). Although not proven to be contained within the apatitic phase through isomorphic substitution, some of the continental phosphorites are of considerable interest because of accumulations of uranium, thorium, yttrium, rare earths, scandium, and vanadium therein. These rarer components are thought to be related to diagenetic processes, in which case they were extracted from sea water during the early formative histories of the phosphorites. 

Also, dielectric materials, especially, during the exposure to the atmosphere, absorb water and OH leads to detrimental interface reactions and water absorption and interface reactivity of yttrium oxide gate dielectrics on silicon was investigated. From the infrared absorption analysis, water vapor was significantly absorbed in the atmosphere. Similar oxidation are expected other high-K materials while the rate of OH absorption is expected to depend on the deposition process and their thermal history [29]. 

Lanthanum (Z = 57) and the following fourteen lanthanides from cerium (Z = 58) to lutetium (Z = 71) are usually classihed as rare-earth elements. Two more elements can be added to the list yttrium (Z — 39) and scandium (Z = 21) their properties are similar to those of lanthanum and they are linked historically with the rare earths. It was precisely the discovery of yttrium that began the history of rare-earth elements. Scandium, mentioned only briefly here, is considered in greater detail in Chapter 9. 

In total, the rare-earth elements (REEs) represent Vg of all the natural elements and their discoveries spanned 113 years—from 1794 (the discovery of yttrium) to 1907 (the discovery of lutetium). One of REEs, promethium, was prepared artificially much later. The unusual history of REEs is due to their extraordinary properties and, first of all, to their striking chemical similarity. In minerals and ores they are encountered all together at the same time, and it is extremely difficult to break the mixture into constituents. This made the history of REEs very rich in false discoveries with new elements often turning out to be mere combinations of already known ones. Even real discoveries did not always relate to pure rare-earth elements in many cases the newly discovered elements proved later to be a mixture of two or more unknown elements. That is why the widely accepted dates of the discovery of some REEs must be treated with a pinch of salt. 

Another important feature in the history of REEs was that they all were first extracted in the form of oxides. Chemists of the past used the name earths for oxides of, for instance, magnesium, calcium (cf. alkaline earths ) and applied it (erroneously, as it became clear later) to oxides of the first REEs, yttrium and cerium. Hence the term rare earths . Pure metals were prepared long after the discovery of the corresponding elements. For instance, a series of heavy lanthanides was prepared as pure metals only after the Second World War. Therefore, in our subsequent narration, the term REEs will refer to oxides. 

Another example is given by discoveries of three totally unrelated elements—bromine, yttrium, and helium. What is the meaning of their dates of discovery in Table 4 The date for bromine (1826) corresponds to the extraction of the element in a free form. The date for yttrium corresponds to the preparation of its oxide (1794). Forty years later it became clear that the yttrium of Gadolin had in fact been a mixture of rare earths, and a relatively clean yttrium oxide was prepared by Mosander. Thus, in 1794 a mixture of related elements was discovered rather than an individual element. The accepted date of discovery of helium (1868) corresponds to an event which had never before happened in the history of elements. For the first time a conclusion about the existence of a new element was made proceeding from an unknown line in the spectrum of solar prominences rather than from experiments with material terrestrial objects. This element remained a pure hypothesis until it was found on Earth (1895). 

From Figure 17.3 it is clear that the history of discoveries falls into three different periods. The first, about 1800, was the time for the basic discoveries, yttrium and cerium the second, around 1840, resulted in four new elements, erbium, terbium, lanthanum and didymium. Not until the introduction of the spectroscopy in the middle of the 19 century and the development of improved separation techniques did the discoveries enter the third period, 1870-1910. Yet, the last REM, promethium, was not discovered until 1945. Some biographical information about the actual discoverers is given along with the different discovery descriptions below. 

The history of rare earth separations dates back to the discovery of yttria in the year 1794, and the isolation of ceria in 1803 after which a total of 17 rare earth elements. Sc, Y, La, Ac and the lanthanide elements (except Pm), were isolated laboriously (in varying degrees of purity) by relatively inefficient fractional precipitation methods, prior to 1947. Such methods have (for the most part) been outmoded by the development of more elegant counter-current techniques during the last 30 years. While the purpose of this chapter is to summarize and comment upon recent progress in means of isolating individual lanthanides and yttrium, some mention of well-developed processes for the preliminary treatment of rare earth mixtures must be made, to place the subject of component resolution in proper context. 

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