Holmium(III) oxide: Difference between revisions

| SPhrasesGHSPictograms = {{S22GHS07}}, {{S24/25GHS09}}

'''Holmium(III) oxide''', or '''holmium oxide''' is a [[chemical compound]] of athe [[rare-earth element]] [[holmium]] and [[oxygen]] with the [[chemical formula|formula]] Ho₂O₃. Together with [[dysprosium(III) oxide]] (Dy₂O₃), holmium oxide is one of the most powerfully [[Paramagnetism|paramagnetic]] substances known. The oxide, also called '''holmia''', occurs as a component of the related erbium oxide [[mineral]] called [[erbia]]. Typically, the oxides of the trivalent [[lanthanide]]s coexist in nature, and separation of these components requires specialized methods. Holmium oxide is used in making specialty colored [[glass]]es. Glass containing holmium oxide and holmium oxide solutions have a series of sharp [[optical absorption]] peaks in the visible [[spectrum|spectral range]]. They are therefore traditionally used as a convenient calibration standard for [[Monochromator|optical spectrophotometers]].

Holmium oxide has a [[cubic crystal system|cubic]], yet rather complex [[bixbyite]] structure, with many atoms per unit cell and a large lattice constant of 1.06&nbsp;nm. This structure is characteristic of oxides of heavy rare-earth elements, such as Tb₂O₃, Dy₂O₃, Er₂O₃, Tm₂O₃, Yb₂O₃ and Lu₂O₃. The thermal expansion coefficient of Ho₂O₃ is also relatively large at 7.4&nbsp;×10⁻⁶/°C.<ref>{{cite journal |doi =10.10161021/0022-5088(69)90137-4cr940055h|title =PreciseThe determinationBinary ofRare the lattice parameters of holmium and erbium sesquioxides atEarth elevatedOxides temperatures|year=1998 |last1=1969Adachi |authorfirst1=Gin-ya |last2=Singh,Imanaka H|journalfirst2=Nobuhito |journal=Journal ofChemical theReviews Less Common Metals|volume=98 |issue=184 |pages =172|last21479–1514 =Dayal|first2 pmid=B|issue11848940 =2}}</ref>

A typical extraction process of holmium oxide can be simplified as follows: the mineral mixtures are crushed and ground. Monazite, because of its magnetic properties can be separated by repeated electromagnetic separation. After separation, it is treated with hot concentrated [[sulfuric acid]] to produce water-soluble sulfates of several rare earth elements. The acidic filtrates are partially neutralized with [[sodium hydroxide]] to pH 3-43–4. [[Thorium]] precipitates out of solution as hydroxide and is removed. After that, the solution is treated with [[ammonium oxalate]] to convert rare earths in to their insoluble [[oxalate]]s. The oxalates are converted to oxides by annealing. The oxides are dissolved in [[nitric acid]] that excludes one of the main components, [[cerium]], whose oxide is insoluble in HNO₃.