Calciothermic reactions are metallothermic reduction reactions (more generally, thermic chemical reactions) which use

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

metal as the

reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are common reducing agents include hydrogen, carbon ...

at high temperature. Calcium is one of the most potent reducing agents available, usually drawn as the strongest oxidic reductant in

Ellingham diagram An Ellingham diagram is a graph showing the temperature dependence of the stability of compounds. This analysis is usually used to evaluate the ease of reduction of metal oxides and sulfides. These diagrams were first constructed by Harold Ellin ...

s, though the

lanthanides The lanthanide () or lanthanoid () series of chemical elements comprises at least the 14 Metal, metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. In the periodic table, they fill the 4f orbitals. Lutetium ...

best it in this respect in oxide processes. On the other hand, this trend does not continue to other compounds that are non-oxides, and for instance

lanthanum Lanthanum is a chemical element; it has symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements bet ...

is produced by the calciothermic reduction of the

chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...

, calcium being a more potent reducing agent than lanthanum involving chlorides. Calciothermic processes are used in the extraction of metals such as

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

zirconium Zirconium is a chemical element; it has Symbol (chemistry), symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyis ...

, and

thorium Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and ha ...

from oxide

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...

s. An interesting way of performing calciothermic reductions is by in-situ generated metallic calcium, dissolved in molten calcium chloride, as shown in the FFC Cambridge Process.

References

Inorganic reactions Metallurgy {{Reaction-stub

See also

References