Holmium earths

L. Holmia, for Stockholm). The special absorption bands of holmium were noticed in 1878 by the Swiss chemists Delafontaine and Soret, who announced the existence of an "Element X." Cleve, of Sweden, later independently discovered the element while working on erbia earth. The element is named after cleve s native city. Holmia, the yellow oxide, was prepared by Homberg in 1911. Holmium occurs in gadolinite, monazite, and in other rare-earth minerals. It is commercially obtained from monazite, occurring in that mineral to the extent of about 0.05%. It has been isolated by the reduction of its anhydrous chloride or fluoride with calcium metal. 

Pure holmium has a metallic to bright silver luster. It is relatively soft and malleable, and is stable in dry air at room temperature, but rapidly oxidizes in moist air and at elevated temperatures. The metal has unusual magnetic properties. Few uses have yet been found for the element. The element, as with other rare earths, seems to have a low acute toxic rating. 

Some nut trees accumulate mineral elements. Hickory nut is notable as an accumulator of aluminum compounds (30) the ash of its leaves contains up to 37.5% of AI2O2, compared with only 0.032% of aluminum oxide in the ash of the Fnglish walnut s autumn leaves. As an accumulator of rare-earth elements, hickory greatly exceeds all other plants their leaves show up to 2296 ppm of rare earths (scandium, yttrium, lanthanum, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). The amounts of rare-earth elements found in parts of the hickory nut are kernels, at 5 ppm shells, at 7 ppm and shucks, at 17 ppm. The kernel of the Bra2d nut contains large amounts of barium in an insoluble form when the nut is eaten, barium dissolves in the hydrochloric acid of the stomach. 

The compounds of the rare earth elements are usually highly colored. Neodymium s compounds are mainly lavender and violet, samarium s yellow and brown, holmium s yellow and orange, and erbium s rose-pink. Europium makes pink salts which evaporate easily. Dysprosium makes greenish yellow compounds, and ytterbium, yellow-gold. Compounds of lutetium are colorless, and compounds of terbium are colorless, dark brown, or black. 

Rare earth. One of a group of 15 chemically related elements lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. 

Dysprosium - the atomic number is 66 and the chemical symbol is Dy. The name derives from the Greek dysprositos for hard to get at , due to the difficulty in separating this rare earth element from a holmium mineral in which it was found. Discovery was first claimed by the Swiss chemist Marc Delafontaine in the mineral samarskite in 1878 and he called it philippia. Philippia was subsequently found to be a mixture of terbium and erbium. Dysprosium was later discovered in a holmium sample by the French chemist Paul-Emile Lecoq de Boisbaudron in 1886, who was then credited with the discovery. It was first isolated by the French chemist George Urbain in 1906. 

Holmium - the atomic number is 67 and the chemical symbol is Ho. The name derives from the Latin holmia for Stockholm . It was discovered in erbia earth by the Swiss chemist J. L. Soret in 1878, who referred to it as element X. It was later independently discovered by the Swedish chemist Per Theodor Cleve in 1879. It was first isolated in 1911 by Holmberg, who proposed the name holmium either to recognize the discoverer Per Cleve, who was from Stockholm or perhaps to establish his own name in history. 

ISOTOPES There are a total of 57 isotopes of holmium. Only one of these, Ho-165, is stable, and it is the only isotope found in the Earth s crust. All the other 56 isotopes have half-lives of a few milliseconds to 1.20x10+ years, the half-life of Ho-166. 

Holmium is a crystal-like, solid rare-earth with a metaUic luster. It is one of the more scarce elements of the lanthanide series. It is soft, hke lead, and can be hammered and pounded into thin sheets. 

Holmium is the 12th most abundant of the rare-earths found in the Earths crust. Although it is the 50th most abundant element on Earth, it is one of the least abundant lanthanide metals. It is found in gadolinite and the monazite sands of South Africa and Austraha and in the beach sands of Florida and the Carolinas in the United States. Monazite sand contains about a 50% mixture of the rare-earths, but only 0.05% by weight is holmium. Today, small quantities of holmium are produced by the ion-exchange process. 

In the 1800s chemists searched for new elements by fractionating the oxides of rare-earths. Carl Gustaf Mosander s experiments indicated that pure ceria ores were actually contaminated with oxides of lanthanum, a new element. Mosander also fractionated the oxides of yttria into two new elements, erbium and terbium. In 1878 J. Louis Soret (1827—1890) and Marc Delafontaine (1837-1911), through spectroscopic analysis, found evidence of the element holmium, but it was contaminated by the rare-earth dysprosia. Since they could not isolate it and were unable to separate holmium as a pure rare-earth, they did not receive credit for its discovery. 

In 1879 holmium was discovered, independently, by Per Theodor Cleve (1840—1905), who managed to isolate holmium from the other rare-earths. Cleve received credit for the discovery of holmium and named it for the Latin word holmia, which means Stockholm, a city in his native country, Sweden. 

Because holmium is produced in such very small amounts, it is not a potential hazard to the general public. However, professional chemists take the same precautions as they do with other rare-earths. 

Einsteinium has homologous chemical and physical properties of the rare-earth holmium (g Ho), located just above it in the lanthanide series in the periodic table. 

The first isotope of this element having mass number 253 and half-life 20 days was detected in 1952 in the Pacific in debris from the first thermonuclear explosion. The isotope was an alpha emitter of 6.6 MeV energy, chemically analogous to the rare earth element holmium. Isotope 246, having a half-life 7.3 minutes, was synthesized in the Lawrence Berkeley Laboratory cyclotron in 1954. The element was named Einsteinium in honor of Albert Einstein. Only microgram amounts have been synthesized. The element has high specific alpha activities. It may be used as a tracer in chemical studies. Commercial applications are few. 

Holmium is obtained from monazite, bastnasite and other rare-earth minerals as a by-product during recovery of dysprosium, thulium and other rare-earth metals. The recovery steps in production of all lanthanide elements are very similar. These involve breaking up ores by treatment with hot concentrated sulfuric acid or by caustic fusion separation of rare-earths by ion-exchange processes conversion to halide salts and reduction of the hahde(s) to metal (See Dysprosium, Gadolinium and Erbium). 

Holmium chloride is obtained from rare-earth minerals. Recovery steps are discussed above (see Holmium). The rare-earth mineral is cracked by acid attack by heating with hydrochloric acid. The water-soluble chloride salt is filtered and separated from insoluble residues. The hydrated chloride salt is heated at 350°C in a current of hydrogen chloride to yield anhydrous H0CI3. Heating in air in the absence of hydrogen chloride yields holmium oxychloride, HoOCl. Hohnium chloride may be purified by distdlation or vacuum sublimation. 

Hohnium oxide occurs in nature, usually associated with small quantities of other rare-earth oxides. Commercial applications of this compound have not been explored fuUy. It is used in refractories and as a catalyst. Characteristic spectral emission lines of holmium oxide glass are used to cahbrate spectrophotometers. ... 

Lutetium is produced commercially from monazite. The metal is recovered as a by-product during large-scale extraction of other heavy rare earths (See Cerium, Erbium, Holmium). The pure metal is obtained by reduction of lutetium chloride or lutetium fluoride by a alkali or alkaline earth metal at... 

Cleve s fame rests chiefly, however, on his discoveries among the rare earths. After obtaining some erbia from which all the ytterbia and scandia had been removed, and after noticing that the atomic weight of the erbium was not constant, he succeeded in resolving the earth into three constituents erbia, holmia, and thulia (21). The absorption bands of holmium had already been noticed by the Swiss chemists M. Delafontaine... 

In the year 1886 Lecoq de Boisbaudran separated pure holmia into two earths, which he called holmia and dysprosta. He accomplished this by fractional precipitation, first with ammonium hydroxide and then with a saturated solution of potassium sulfate, and found that the constituents of impure holmium solutions precipitate in the following order terbium, dysprosium, holmium, and erbium (3, 37, 48). Lecoq de Boisbaudran never had an abundant supply of raw materials for his remarkable researches on the rare earths, and he once confided to Professor Urbain that most of his fractionations had been carried out on the marble slab of his fireplace (56). 

Even more striking in the old tooth is the abundance of rare earths (dysprosium, holmium, erbium, thulium, ytterbium, and lutetium) and the elements tantalum, tungsten, gold, thorium, and uranium. Rare earth minerals are found in Scandinavia (in fact, many rare earth elements were discovered there), but what were they used for Did people prepare food with them Did they somehow get into the food chain ... 

B. Evans, Assistant Chemist. Rare-Earth Information Center. Energy itnd Mineral Resources Research Institute. Iowa Slate University. Ames. I,A. http //www.cxternal.ameslab.gov/. Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Neodymium Rare-Earth Elements and Metals Praseodymium Samarium Scandium Terbium Thulium Ytterbium and Yttrium Daniel F. Farkas, Oregon State University. Corvallis. OR. http // oregonstate.edu/. Food Processing... 

The lanthanide elements were once known as the rare earths. Lanthanides, however, are not particularly rare. Holmium, one of the less common lanthanides, is still 20 times more abundant than silver on Earth. The rare earth name comes instead from how difficult it was for early chemists to separate all of the lanthanides from one another. Because these elements add electrons to an inner shell, they all show the same face to other elements. This makes them all react very similarly with other elements, and it can be tricky to tell them apart. 

Lanthanide bromides and iodides have found important applications in a completely different field. They are added as additives in high-pressure discharge lamps in the lighting industry to improve the arc stability and the colour quality. The latter is due to the contribution of the multiline spectrum of the doped rare earths which are added to the salt mixture. Lanthanide trihalides of dysprosium, holmium, thullium, gadolinium and lutetium are used frequently for this purpose (Hilpert and Niemann, 1997). 

One possible application in which large amounts of rare earths and actinides would be processed occurs in some schemes for nuclear waste management. If it should prove to be advantageous to remove transplutonium elements from nuclear waste, for example, the recovery of Am and Cm from the much larger amounts of rare earths would be required. This problem has been investigated by the author in tracer tests with rare earth mixtures typical of fission products, using a heavy rare earth such as holmium as a stand-in for Am and Cm (Fig. 5). It is clear that the bulk of the holmium can be recovered in reasonable purity, and that the bulk of the lighter rare earths is effectively separated from the very small amount of heavy rare earths, Am, and Cm. 

The position of yttrium in rare earth chemistry has always been interesting and this is also the case with respect to complex formation. The electrostatic model suggests placement of yttrium between holmium and thulium. It has been shown that it is not the case [14]. When one considers the stability constant data of group 1 ligands, yttrium is similar to the heavy rare earths. When the second group of ligands is considered, yttrium exhibits a behaviour similar to the lighter rare earth elements. 

Lasing action has been observed with other rare earths. The lower laser level in holmium is close to the ground state and can operate as a four level laser at liquid nitrogen temperatures. Erbium is similar to holmium. With other rare earths, alternate wavelengths can be obtained. Both Ho and Er operate in a region greater than 1.5 pm. Erbium can also... 

The term rare earth elements is sometimes applied to the elements La-Lu plus yttrium. The convenience of including La, which, strictly speaking, is not a lanthanide, is obvious. The reason for including Y is that Y has radii (atomic, metallic, ionic) that fall close to those of erbium and holmium and all of its chemistry is in the trivalent state. Hence it resembles the later lanthanides very closely in its chemistry and occurs with them in Nature. 

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