Perrhenic acid
Structural formula | |||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
General | |||||||||||||||||||
Surname | Perrhenic acid | ||||||||||||||||||
other names |
|
||||||||||||||||||
Molecular formula | HReO 4 | ||||||||||||||||||
Brief description |
colorless to pale yellowish liquid |
||||||||||||||||||
External identifiers / databases | |||||||||||||||||||
|
|||||||||||||||||||
properties | |||||||||||||||||||
Molar mass | 251.21 g mol −1 | ||||||||||||||||||
Physical state |
liquid (solution in water) |
||||||||||||||||||
density |
|
||||||||||||||||||
Vapor pressure |
23 hPa (20 ° C) |
||||||||||||||||||
pK s value |
−1.25 |
||||||||||||||||||
solubility |
miscible with water |
||||||||||||||||||
safety instructions | |||||||||||||||||||
|
|||||||||||||||||||
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Perrhenic acid is an inorganic chemical compound from the group of acids . It is only available in an aqueous solution. As solid perrhenic Dirheniumdihydratoheptoxid Re is 2 O 7 (OH 2 ) 2 , respectively.
Extraction and presentation
An aqueous perrhenic acid solution can be obtained by reacting rhenium with hydrogen peroxide .
It is also possible to display it by dissolving rhenium (VII) oxide in water.
The solutions can only be used up to a concentration of max. 70 percent by weight of HReO 4 are evaporated, above that HReO 4 evaporates .
Solid perrhenic acid can be obtained from an aqueous, as concentrated as possible, perrhenic acid solution by removing excess water in the desiccator using phosphorus pentoxide or magnesium perchlorate .
properties
Perrhenic acid cannot be represented as a pure substance and only exists as a colorless to slightly yellowish solution. Dirhenium dihydratoheptoxide is a pale yellowish, extremely hygroscopic solid. It is soluble in nitromethane and decomposes at 65 ° C with volatilization of HReO 4 . It has a monoclinic crystal structure with the space group P 2 1 / m (space group no. 11) and the lattice parameters a = 882 pm, b = 889 pm, c = 503 pm and β = 112.0 °, with O 3 Re- O-ReO 3 (OH 2 ) 2 molecules.
use
Perrhenic acid is used to produce highly conductive and superconducting synthetic metals.
Individual evidence
- ↑ a b c d data sheet Perrhenic acid, 75-80% aq. Soln. at AlfaAesar, accessed on August 2, 2013 ( PDF )(JavaScript required) .
- ↑ a b c d e data sheet Perrhenic acid solution, 75-80 wt.% In H from Sigma-Aldrich , accessed on August 2, 2013 ( PDF ).
- ↑ a b c d e f Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1632.
- ↑ Entry on Perrhenate. In: Römpp Online . Georg Thieme Verlag, accessed on September 13, 2018.
- ↑ H. Beyer, O. Glemser, B. Krebs, G. Wagner: The structure of dirhenium dihydratoheptoxide Re2O7 (OH2) 2. - A new type of water binding in an aquoxide -. In: Journal of Inorganic and General Chemistry. 376, 1970, p. 87, doi : 10.1002 / zaac.19703760111 .