Chevreul's salt
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IUPAC name
Copper(I, II) sulfite dihydrate
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Other names
Chevreul's salt
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Identifiers | |
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3D model (
JSmol ) |
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ChemSpider | |
PubChem CID
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UNII |
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CompTox Dashboard (EPA)
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Properties | |
Cu3H4O8S2 | |
Molar mass | 386.78 g·mol−1 |
Appearance | brick red powder |
Density | 3.57 |
Solubility | aqueous ammonia |
Thermal conductivity
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0.1 kWcm−1K−1 |
Structure[3] | |
monoclinic | |
P21/n[2] | |
a = 5.5671 Å, b = 7.7875 Å, c = c = 8.3635 Å α = 90°, β = 91.279o°, γ = 90°
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Lattice volume (V)
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362.5 Å3 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chevreul's salt (copper(I,II) sulfite dihydrate, Cu2SO3•CuSO3•2H2O or Cu3(SO3)2•2H2O), is a copper salt which was prepared for the first time by a French chemist Michel Eugène Chevreul in 1812. Its unusual property is that it contains copper in both of its common oxidation states, making it a mixed-valence complex. It is insoluble in water and stable in air.[4] What was known as Rogojski's salt is a mixture of Chevreul's salt and metallic copper.[5]
Preparation
Chevreul's salt is prepared by treating aqueous copper(II) sulfate with a solution of potassium metabisulfite. The solution changes colour from blue to green immediately. The identity of the green species is unknown. Heating this solution produces a reddish solid precipitate:
3 CuSO4 + 4 K2S2O5 + 3 H2O → Cu3(SO3)2•2H2O + 4 K2SO4 + 4 SO2 + H2SO4
When sodium ions are present in the solutions that form the salt, sodium can substitute for some of the copper (I), as the ions have the same charge and similar sizes.[3]
Reactions
Chevreul's salt exhibits properties of both copper(I) and copper(II). Hydrochloric acid produces a white solid of copper(I) chloride. If too much acid is added, the precipitate dissolves. If an ammonia solution is added to the product, it is dissolved and a deep blue color appears - the presence of [Cu(NH3)4]2+ complex.[5]
On heating in an inert atmosphere it is stable to 200 °C. It gives off water and sulfur dioxide to give CuSO4•Cu2O and CuSO4•2CuO. At 850 °C
Properties
The
The optical reflectance spectrum shows absorption around 425 nm with a shoulder to 500 nm. This is due to a cuprous sulfite
In the infrared range the band gap is 0.85 eV.[7]
Chevreul's salt is a representative member of an
The
The
In Chevreul's salt crystals there are two environments for copper. The +1 oxidation state copper is in a distorted tetrahedral space surrounded by three oxygens and a sulfur atom. The +2 oxidation state copper (or other metal in the isomorphic series) is in a distorted
The
Application
Chevreul's salt is used in a
Chevreul's salt is formed as a corrosion product on copper metal in the presence of humid air contaminated with sulfur dioxide. When first formed the salt has an unstable orthorhombic form with a = 5.591, b = 7.781 and c = 8.356 Å, which changes to the normal monoclinic form over a month, or faster when heated.[2]
References
- ISBN 9781483286433.
- ^ .
- ^ .
- ^ Chevreul, M. E. (1812). "Propriétés du sulfte de cuivre". Annales de Chimie. 83: 187.
- ^ .
- .
- ^ .
- ^ .
- S2CID 99729125.
- ISBN 9783662539736.
- .