Metals didymium

In 1841 Mosander had treated lanthana with dilute nitric acid, and had extracted from it a new rose-colored oxide, which he believed contained a new element. He named the new metal didymium because, as he said, it seemed to be an inseparable twin brother of lanthanum (27, 29, 46). 

Gr. neos, new, and didymos, twin) In 1841, Mosander, extracted from cerite a new rose-colored oxide, which he believed contained a new element. He named the element didymium, as it was an inseparable twin brother of lanthanum. In 1885 von Welsbach separated didymium into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate. While the free metal is in misch metal, long known and used as a pyrophoric alloy for light flints, the element was not isolated in relatively pure form until 1925. Neodymium is present in misch metal to the extent of about 18%. It is present in the minerals monazite and bastnasite, which are principal sources of rare-earth metals. 

It is easy to reduce anhydrous rare-earth hatides to the metal by reaction of mote electropositive metals such as calcium, lithium, sodium, potassium, and aluminum. Electrolytic reduction is an alternative in the production of the light lanthanide metals, including didymium, a Nd—Pt mixture. The rare-earth metals have a great affinity for oxygen, sulfur, nitrogen, carbon, silicon, boron, phosphoms, and hydrogen at elevated temperature and remove these elements from most other metals. 

A commercial mixture of several of the rare-earth elements is called didymium (Di). It is neither an element nor a compound, but is used to name the mixture of oxides and salts of most of the rare-earth elements that are extracted from the ore monazite. Another unique substance, called misch metal, is an alloy of iron and several rare-earth elements (La, Ce, and Pr). This mixture is pyrophoric, which means it sparks when scratched. This is why it is used for cigarette-lighter flints. 

Mosander, C. G., On the new metals lanthanium and didymium, which are associated with cerium and on erbium and terbium, new metals associated with yttria, Phil. Mag., [3], 23, 241-54 (Oct., 1843). 

One method of preparation consists in a modification of the Goldschmidt process. Niobium pentoxide is mixed with an alloy of the rare earths, called mixed metal, obtained in the manufacture of thorium nitrate, and consisting roughly of 45 per cent, of cerium, 20 per cent, of lanthanum, 15 per cent, of didymium, and about 20 per cent, of other rare-earth metals. The reaction is carried out in a magnesia-lined crucible, and is started with a firing mixture of barium peroxide, potassium chlorate, and aluminium powder. Considerable evolution of heat takes place and the reduction is extremely rapid a button of niobium is obtained 4 which, however, is not pure. 

Arsenites of the Rare Earth Metals.—When cerium dioxide is heated with arsenious oxide some oxidation of the latter occurs, but the product appears to be a mixture of oxides.5 Didymium hydrogen orthoarsenite, Di2(HAs03)3, has been obtained6 as a white, granular, insoluble powder by boiling didymium hydroxide with an aqueous solution of arsenious oxide. Lanthanum hydrogen orthoarsenite, La2(HAs03)3, has been prepared in a similar manner. The existence of these compounds needs confirmation, however.7... 

Many metal chlorides when heated with an excess of nitric acid are converted into the nitrates. Thus, J. L. Smith found that the transformation occurs with potassium or sodium chloride in the presence of 7 to 8 parts of nitric acid J. S. Stas said that at 40°-50°, potassium, sodium, or lithium chloride require respectively 3, 4, and 5-5 parts of nitric acid. J. L. Smith said that ammonium chloride and nitric acid yield nitrous oxide. H. Wurtz found that auric, cadmium, cerium, lanthanum, didymium, ferric, and platinic chlorides are decomposed by nitric acid incompletely and with difficulty. S. Schlesinger said that the two copper chlorides, mercurous, zinc, and lead chlorides, are decomposed, but, added H. Wurtz, with difficulty and incompletely while mercuric ajid silver chlorides are not attacked. F. Rose found cobalt amminochlorides are readily converted into the nitrate. 

Neodymium-based catalysts are favored over other Ln metals because they are highly active and the catalyst precursors are readily available for reasonable prices. In addition, Nd catalyst residues do not catalyze aging of the rubber. The use of didymium catalyst systems is also reported in the literature. Didymium consists of a mixture of the three lanthanides neodymium (72 wt. %), lanthanum (20 wt. %) and praseodymium (8 wt. %). 

Praseodymium 59 Pr Alloys, didymium glass (for protective goggles), yellow ceramic pigments, cryogenic refrigerant, misch metal... 

Neodymium 60 Nd Electronics, steel manufacture, glazes and coloured glass (including didymium glass), lasers, magnets, petroleum cracking catalysts, misch metal ... 

Molybdates of the Rare Earth Metals. —Salts of the type M2(Mo04)3 have been described. The cerous salt is obtained as yellow crystals by fusing together anhydrous cerous chloride and sodium molybdate. The density of the molten salt is 4-56. The crystals are similar to those of lead and bismuth molybdates, as also are those of didymium molybdate. ... 

It is doubtful whether cerium and lantanium do not belong to the preceding order, to which also belong, in all probability, the three new metals of Mosander, didymium, erbium, and terbium. 

Group III. Earth metals Beryllium 6.9 Aluminum 13.7 Zirconium 33.6 Cerium 47 Lanthanium 47 Didymium 48 Thorium 59.6. The aluminum is twice the beryllium, or the third part from the sum of beryllium with zirconium (see Table 1.4). 

TABLE 1.4 Selective Combinations of Earth Metal Elements (the Lanthanium and the Didymium Were Identical With Cerium, or Close) (Newlands, 1863)... 

The trivalency of yttrium (which is now present in oxide instead ofYO) was provided by the periodic law and now become very likely that Cleve and all the other investigators of the rare metals, not only have adopted, but have applied it without any new demonstration to the elements so imperfect (as the groups of cerite and gadolinite) especially since when Hildebrand had determined the specific heat of lanthanum and didymium and he had confirmed the expectations suggested by the periodic law. 

The discovery of the rare earths in 1794 was a prototype of a surprise, it was not just one more metallic element, such as strontium and titanium. Many early observations are fascinating Berzelius report that a very high concentration of didymium can be kept in solution in aqueous ammonia containing ammonium... 

Electrolytic method used for the first time to prepare rare earth metals (La, Ce and didymium [lPr-3Nd])... 

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