COPPER(II) SULFATE

Copper(II) sulfate
Crystal of copper(II)sulphate4 · 5H2O Photo of powdered copper(II) sulfate pentahydrate Ball-and-stick model of the unit cell of anhydrous copper(II) sulfate Space-filling model of part of the crystal structure of anhydrous copper(II) sulfate
General
Systematic name	Copper(II) sulfate pentahydrate
Other names	Copper(II) sulfate Copper(II)sulphate Cupric sulfate Blue vitriol Bluestone Chalcanthite
Molecular formula	CuSO4·5H2O (pentahydrate) CuSO4 (anhydrous)
Molar mass	249.7 g/mol (pentahydrate) 159.6 g/mol (anhydrous)
Appearance	blue crystalline solid (pentahydrate) gray-white powder (anhydrous)
CAS number	[7758-99-8] (pentahydrate) [7758-98-7] (anhydrous)
EINECS number	231-847-6
Properties
Density and phase	2.284 g/cm³, solid
Solubility in water	31.6 g/100 ml (0 °C)
Melting point	110 °C (− 4H2O) 150 °C (423 K) (− 5H2O) 650 °C ''decomp.''
Structure
Coordination geometry	Octahedral
Crystal structure	Triclinic
Thermodynamic data
Standard enthalpy of formation Δf''H''°solid	-769.98 kJ/mol
Standard molar entropy ''S''°solid	109.05 J.K−1.mol−1
Safety data
EU classification	Harmful Dangerous for the environment
R-Phrases	, ,
S-Phrases	, , ,
NFPA 704
PEL-TWA	1 mg/m³ (OSHA)
IDLH (NIOSH)	100 mg/m³
Flash point	non flammable
RTECS number	GL8800000
Supplementary data page
Structure and properties	''n'', ''εr'', etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other cations	Nickel(II) sulfate Zinc sulfate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

'Copper(II) sulfate' ("sulphate" in most Commonwealth nations) is the chemical compound with the formula CuSO₄. This salt exists as a series of compounds that differ in their degree of hydration. The anhydrous form is a pale green or gray-white powder, while the pentahydrate, the most commonly encountered salt, is bright blue. This hydrated copper sulfate occurs in nature as the mineral called chalcanthite. The archaic name for copper(II) sulfate is "blue vitriol" or "bluestone"^[1]

Contents

Structure

Preparation

Uses

In organic synthesis

In school chemistry demonstrations

As an herbicide, fungicide, pesticide

Other uses

Safety

References

External links

Structure

In the pentahydrate, copper(II) is bonded to four molecules of water and to the oxygen atoms of two sulfate anions. The fifth water is not coordinated, but links the sulfate anions via hydrogen bonding. In the trihydrate, all three water molecules are bonded as well as one oxygen atom of the sulfate, to define a distorted square planar arrangement, two more oxygen ligands are ca. 2.4 Å distant from copper. In the anhydrous form, copper is bound to four oxygen atoms of sulfate (r_Cu-O = 1.9-2.0Å) and more weakly bonded to two other oxygen atoms (2.4 Å).^[2] A monohydrate is also known.

Preparation

Since it is available commercially, copper sulfate is usually purchased, not prepared in the laboratory. It can be made by the action of sulfuric acid on a variety of copper(II) compounds, for example copper(II) oxide. Copper(II) sulfate decomposes before melting. The common pentahydrate form dehydrates, losing four water molecules at 110 °C and all five at 150 °C. At 650 °C, copper(II) sulfate decomposes into copper(II) oxide (CuO) and sulfur trioxide (SO₃). When heated in an open flame the crystals are dehydrated and turn grayish-white.^[3]

Uses

In organic synthesis

Copper sulfate is employed in organic synthesis.^[4] The anhydrous salt catalyses the transacetalization in organic synthesis.^[5] The hydrated salt reacts with potassium permanganate to give an oxidant for the conversion of primary alcohols.^[6]

In school chemistry demonstrations

Copper sulfate is a commonly included chemical in children's chemistry sets and is often used in high school crystal growing.^[7] and copper plating experiments. Due to its toxicity, it is not recommended for small children. Copper sulfate is often used to demonstrate an exothermic reaction, in which steel wool or magnesium ribbon is placed in an aqueous solution of CuSO₄. It is used in school chemistry courses to demonstrate the principle of mineral hydration. The pentahydrate form, which is blue, is heated, turning the copper sulfate into the anhydrous form which is white, while the water that was present in the pentahydrate form evaporates. When water is then added to the anhydrous compound, it turns back into the pentahydrate form, regaining its blue colour.

As an herbicide, fungicide, pesticide

Copper sulfate pentahydrate is a fungicide. Mixed with lime it is called Bordeaux mixture to control fungus on grapes and other berries.^[8] Its use as an herbicide is not agricultural, but instead for control of invasive exotic aquatic plants and the roots of other invasive plants near various pipes that contain water. A dilute solution of copper sulfate is used to treat aquarium fish of various parasitic infections^[9], and is also used to remove snails from aquariums. However, as the copper ions are also highly toxic to the fish, care must be taken with the dosage. Most species of algae can be controlled with very low concentrations of copper sulfate.
===Analytical reagent===
Several chemical tests utilize copper sulfate. It is used in Fehling's solution and Benedict's solution to test for reducing sugars, which reduce the soluble blue copper(II) sulfate to insoluble red copper(I) oxide. Copper(II) sulfate is also used in the Biuret reagent to test for proteins.
Copper sulfate is also used to test blood for anemia ^[10]. A drop of the patient's blood is dropped into an aqueous solution of copper sulfate solution: if it sinks within a certain time, then the patient has sufficient hemoglobin levels and is not anemic. If the blood drop floats or sinks slowly, then the patient is iron-deficient and may be anemic.
In a flame test, its copper ions emit a deep blue-green light, much more blue than the flame test for barium.

Other uses

Other applications include hair dyes, coloring glass, and processing of leather and textiles. Can also be used to inhibit the growth of bacteria like e. coli. Another more commonly witnessed use is to give pyrotechnics a green coloring^[11].
A full list of uses can be seen here.

Safety

Copper sulfate is harmful by inhalation or ingestion, and can cause dermatitis with prolonged exposure^[1]. It is also toxic to aquatic organisms and may cause long term damage in the environment.

References

1. http://ptcl.chem.ox.ac.uk/MSDS/CO/copper_II_sulfate.html
2. Wells, A.F. (1984) ''Structural Inorganic Chemistry'', Oxford: Clarendon Press. ISBN 0-19-855370-6.
3. Holleman, A. F.; Wiberg, E. ''Inorganic Chemistry'' Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
4. Hoffman, R. V. "Copper(II) Sulfate" ''Encyclopedia of Reagents for Organic Synthesis'', 2001 John Wiley & Sons. DOI: 10.1002/047084289X.rc247
5. Hulce, M. Mallomo, J. P.; Frye, L. L.; Kogan, T. P.; Posner, G. H. “(S)-( + )-2-(p-Toluenesulfinyl)-2-Cyclopentanone: Precursor for Enantioselective Synthesis of 3-Substituted Cyclopentanones” Organic Syntheses, Collected Volume 7, p.495 (1990).
6. Jefford, C. W.; Li, Y.; Wang, Y. “A Selective, Heterogeneous Oxidation using a Mixture of Potassium Permanganate and Cupric Sulfate: (3aS,7aR)-Hexahydro-(3S,6R)-Dimethyl-2(3H)-Benzofuranone” Collective Volume 9, page 462.
7. http://www.newton.dep.anl.gov/askasci/chem03/chem03203.htm
8. http://www.copper.org/applications/compounds/copper_sulfate02.html
9. http://www.fishdoc.co.uk/treatments/copper.htm
10. http://cat.inist.fr/?aModele=afficheN&cpsidt=2686293
11. http://www.copper.org/applications/compounds/table_a.html
12. http://ptcl.chem.ox.ac.uk/MSDS/CO/copper_II_sulfate.html

External links

★ (anhydrous)

★ (pentahydrate)

★ National Pollutant Inventory - Copper and compounds fact sheet

★ UNCP Copper