Chemical Properties
grey metal ingot
Physical properties
Holmium is a crystal-like, solid rare-earth with a metallic luster. It is one of the more scarceelements of the lanthanide series. It is soft, like lead, and can be hammered and pounded intothin sheets.
Its melting point is 1,474°C, its boiling point is 2,700°C, and its density is 8.79g/cm3.
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 havehalf-lives of a few milliseconds to 1.20×10+3 years, the half-life of Ho-166.
Origin of Name
Derived from the Latin word for the ancient city named Holmia (present-
day Stockholm, located in Sweden).
Occurrence
Holmium is the 12th most abundant of the rare-earths found in the Earth’s crust. Althoughit 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 Australia and in thebeach sands of Florida and the Carolinas in the United States. Monazite sand contains about a50% mixture of the rare-earths, but only 0.05% by weight is holmium. Today, small quantitiesof holmium are produced by the ion-exchange process.
Characteristics
Although stable at room temperatures, holmium will corrode at higher temperatures andhumidity. Its oxide coating is a yellowish film that reacts slowly with water and dissolves inweak acids. Holmium has one of the highest magnetic properties of any substance, but it haslittle commercial use.
Production Methods
Holmium is obtained from monazite, bastnasite and other rare-earth minerals as a by-product during recovery of dysprosium, thulium and other rareearth metals. The recovery steps in production of all lanthanide elements arevery similar. These involve breaking up ores by treatment with hot concentrated sulfuric acid or by caustic fusion; separation of rare-earths by ionexchange processes; conversion to halide salts; and reduction of the halide(s)to metal (See Dysprosium, Gadolinium and Erbium).
Bulk holmium metal is prepared by reduction of holmium chloride or fluo-ride by sodium, calcium, or magnesium in a tantalum crucible under argonatmosphere:
2HoF3 + 3Ca → 3CaF2 + 2Ho
Pure holmium metal is obtained by distillation of crude metal at 1,500°C.
General Description
Holmium Wavelength Calibration Standard is a high-quality secondary reference standard offered as a suitable alternative to NBS Holmium Oxide Solution (No. 2034). It is used to establish the accuracy of conventional spectrophotometers in the spectral range 240 to 650 nm. The product consists of Holmium perchlorate (15% w/v) in 10% perchloric acid.
Hazard
Because holmium is produced in such very small amounts, it is not a potential hazard tothe general public. However, professional chemists take the same precautions as they do withother rare-earths.
reaction suitability
reagent type: catalyst
core: holmium
