Ammonium perrhenate
Encyclopedia
Ammonium perrhenate is the ammonium
salt of perrhenic acid
, NH4ReO4. This is the most common form in which rhenium
is traded. Prices are quoted in US Dollars per kg Rhenium
content. Rhenium
content of APR is typically 69.0 - 69.4%.
The crystal structure of APR is that of scheelite
, in which the atomic cation is replaced by the ammonium molecular cation. It undergoes a molecular orientational ordering transition on cooling without change of space group, but with a highly anisotropic change in the shape of the unit cell, resulting in the unusual property of having a positive temperature and pressure Re NQR coefficient.
NH4ReO4 can be regarded as the prototype structure of a family of ammonium scheelites, which include the pertechnetate
(NH4TcO4), periodate
(NH4IO4), tetrachlorothallate (NH4TlCl4) and tetrachloroindate (NH4InCl4).
(also known as base piranha
).
powder can be produced from APR by reducing it with hydrogen
:
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
salt of perrhenic acid
Perrhenic acid
Perrhenic acid is the chemical compound with the formula Re2O72. It is obtained by evaporating aqueous solutions of Re2O7. Conventionally, perrhenic acid is considered to have the formula HReO4, and a species of this formula forms when rhenium oxide sublimes in the presence of water or steam...
, NH4ReO4. This is the most common form in which rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
is traded. Prices are quoted in US Dollars per kg Rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
content. Rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
content of APR is typically 69.0 - 69.4%.
Structure
Scheelite
Scheelite is a calcium tungstate mineral with the chemical formula CaWO4. It is an important ore of tungsten. Well-formed crystals are sought by collectors and are occasionally fashioned into gemstones when suitably free of flaws...
, in which the atomic cation is replaced by the ammonium molecular cation. It undergoes a molecular orientational ordering transition on cooling without change of space group, but with a highly anisotropic change in the shape of the unit cell, resulting in the unusual property of having a positive temperature and pressure Re NQR coefficient.
NH4ReO4 can be regarded as the prototype structure of a family of ammonium scheelites, which include the pertechnetate
Pertechnetate
The pertechnetate ion is an oxoanion with the chemical formula TcO4−. It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium...
(NH4TcO4), periodate
Periodate
Periodate is an anion composed of iodine and oxygen. Periodates include two forms. The metaperiodate ion is IO4−; the orthoperiodate ion is IO65−. Usually both forms are called periodates. Periodate is the conjugate base of periodic acid....
(NH4IO4), tetrachlorothallate (NH4TlCl4) and tetrachloroindate (NH4InCl4).
Preparation
Ammonium perrhenate may be prepared from elemental rhenium by dissolving in ammoniacal hydrogen peroxideHydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
(also known as base piranha
Piranha solution
Piranha solution, also known as piranha etch, is a mixture of sulfuric acid and hydrogen peroxide , used to clean organic residues off substrates...
).
Reactions
Pure rheniumRhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
powder can be produced from APR by reducing it with hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
:
- 2 NH4ReO4 + 7 H2 → 2 Re + 8 H2O + 2 NH3