Thorium dioxide (ThO₂), also called thorium(IV) oxide (IUPAC) is a white, crystalline powder. It was formerly known as thoria or thorina. It is produced mainly as a by-product of lanthanide and uranium production^[1]. IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... It has been suggested that this article or section be merged with Solution. ... Water has the chemical formula H2O, meaning that one molecule of water is composed of two hydrogen atoms and one oxygen atom. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ... The coordination geometry of an atom is the geometrical pattern formed by its neighbors in a molecule or a crystal. ... Rose des Sables (Sand Rose), formed of gypsum crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Fluorite (also called fluor-spar) is a mineral composed of calcium fluoride, CaF2. ... The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 atmosphere... In chemistry, the standard molar entropy is the entropy content of one mole of substance, under conditions of standard temperature and pressure. ... Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main source of European Union law concerning chemical safety. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... The dielectric constant εr (represented as or K in some cases) is defined as the ratio: where εs is the static permittivity of the material in question, and ε0 is the vacuum permittivity. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... IR spectrum of a thin film of liquid ethanol. ... Nuclear Magnetic Resonance Spectroscopy most commonly known as NMR Spectroscopy is the name given to the technique which exploits the magnetic properties of nuclei. ... It has been suggested that Mass spectrum be merged into this article or section. ... // An ion is an atom, group of atoms, or subatomic particle with a net electric charge. ... // An ion is an atom, group of atoms, or subatomic particle with a net electric charge. ... Uranium trioxide (UO3), also called uranyl oxide, uranium(VI) oxide, and uranic oxide, is the hexavalent oxide of uranium. ... Prepared during the reprocessing of nuclear fuel by calcination of plutonium(IV) oxalate, Pu(C2O4)2. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... The lanthanide series comprises the 15 elements from lanthanum to lutetium on the periodic table, with atomic numbers 57 through 71. ... General Name, Symbol, Number uranium, U, 92 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Atomic mass 238. ...

The compound is radioactive due to the radioactivity of thorium. Thorium dioxide can be used as a nuclear fuel. (Refer to the article of thorium for more information on this application.) The high thermal stability of thorium dioxide has given it applications in flame spraying and high temperature ceramics. Thorium dioxide was the primary ingredient in the X-ray contrast medium Thorotrast. Use of Thorotrast was abandoned when it turned out to be a carcinogen, sometimes causing cholangiocarcinoma. Today, barium sulfate is the standard X-ray contrast agent. Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Atomic mass 232. ... In nuclear physics, a nuclear reaction is a process in which two nuclei or nuclear particles collide, to produce different products than the initial products. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Atomic mass 232. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Thorotrast is a suspension containing particles of the radioactive compound thorium dioxide, ThO2, used as a contrast medium in X-ray diagnostics in the 1930s and 40s (use in some countries, such as the U.S. continued into the 1950s). ... // Carcinogen In pathology, a carcinogen is any substance or agent that promotes cancer. ... Cholangiocarcinoma is an adenocarcinoma of the biliary duct system. ... Granulated Barium Sulfate Barium sulfate (or barium sulphate), white crystalline salt which is insoluble in water. ...

Thorium dioxide is used as a stabilizer in tungsten electrodes in TIG welding and electron tubes. As an alloy, thoriated tungsten metal is not easily deformed because the high fusion material thoria augments the high temperature mechanical properties, and thorium helps stimulate the emission of electrons (thermions). It is the most popular oxide additive because of its low cost, but is being phased out in favor of non-radioactive elements such as cerium, lanthanum and zirconium. General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Atomic mass 183. ... Gas Tungsten Arc Welding (GTAW) is commonly known as Tungsten Inert Gas Welding (TIG), however since some process variations utilize active (other than inert) shielding gases, the correct technical term is GTAW. In this process a non-consumable tungsten electrode is used and the electric arc occurs between this electrode... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... Thermionic emission is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. ... General Name, Symbol, Number cerium, Ce, 58 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Atomic mass 140. ... General Name, Symbol, Number lanthanum, La, 57 Chemical series lanthanides Group, Period, Block 3, 6, f Appearance silvery white Atomic mass 138. ... General Name, Symbol, Number zirconium, Zr, 40 Chemical series transition metals Group, Period, Block 4, 5, d Appearance silvery white Atomic mass 91. ...

A major use in the past was in gas mantles, which were frequently composed of 99% ThO₂ and 1% cerium(IV) oxide. Even as late as the 1980's it was estimated that about half of all ThO₂ produced (several hundred tonnes per year) was used for this purpose^[1]. Some mantles still use thorium, but yttrium oxide (or sometimes zirconium oxide) is used increasingly as a replacement. For other uses of mantle see: mantle (disambiguation) An incandescent gas mantle, gas mantle, or Welsbach mantle is a device for generating bright white light when heated by a flame. ... Flash point None R/S statement R: ? S: ? RTECS number  ? Supplementary data page Structure and properties n, εr, etc. ... Yttrium oxide is an oxide of yttrium. ... Zirconia (ZrO2) is a white crystalline oxide of zirconium that is used as a refractory, in insulation, abrasives, enamels and glazes. ...

Thorium dioxide was formerly added to glasses during manufacture to increase their refractive index, producing thoriated glass with up to 40% ThO₂ content. These glasses were used in the construction of high-quality photographic lenses. However, the radioactivity of the thorium caused both a safety and pollution hazard and self-degradation of the glass (turning it yellow or brown over time). Lanthanum oxide has replaced thorium dioxiode in almost all modern high-index glasses. The material definition of glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly to below its glass transition temperature, thereby not giving enough time for a regular crystal lattice to form. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... Photographic lens One of Canons most popular wide angle lenses - 17-40 f/4 L The zoom lens of the Canon Elph A photographic lens (or more correctly, objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images... Lanthanum(III) oxide is a white solid. ...

The melting point of thorium oxide is 3300°C - the highest of all oxides. Only a few elements (including tungsten) and a few compounds (including tantalum carbide) have higher melting points. General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Atomic mass 183. ... Tantalum carbide (TaC) is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. ...

References

1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, Oxford, UK, 1984. See pages 1425, 1456.