Copper(II) sulfate

Copper(II) sulfate
Crystal of CuSO4·5H2O	Anhydrous CuSO4 powder
Ball-and-stick model of CuSO4	Space-filling model CuSO4
IUPAC name Copper(II) sulfate
Other names Cupric sulfate Blue vitriol (pentahydrate) Bluestone (pentahydrate) Bonattite (trihydrate mineral) Boothite (heptahydrate mineral) Chalcanthite (pentahydrate mineral) Chalcocyanite (mineral)
Identifiers
CAS number	7758-98-7 Y,  7758-99-8 (pentahydrate)
PubChem	24462
ChemSpider	22870 Y
UNII	KUW2Q3U1VV Y
EC number	231-847-6
KEGG	C18713 Y
ChEBI	CHEBI:23414 Y
ChEMBL	CHEMBL604 Y
RTECS number	GL8800000 (anhydrous) GL8900000 (pentahydrate)
Jmol-3D images	Image 1
SMILES [O-]S(=O)(=O)[O-].[Cu+2]
InChI InChI=1S/Cu.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Y Key: ARUVKPQLZAKDPS-UHFFFAOYSA-L Y InChI=1/Cu.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Key: ARUVKPQLZAKDPS-NUQVWONBAI
Properties
Molecular formula	CuSO4
Molar mass	159.62 g/mol (anhydrous) 249.70 g/mol (pentahydrate)
Appearance	blue (pentahydrate) gray-white (anhydrous)
Density	3.603 g/cm3 (anhydrous) 2.284 g/cm3 (pentahydrate)
Melting point	110 °C (·4H2O) 150 °C (423 K) (·5H2O) < 650 °C decomp.
Solubility in water	pentahydrate 316 g/L (0 °C) 2033 g/L (100 °C) form unspecified 320 g/L (20°C) 618 g/L (60°C) 1140 g/L (100 °C)
Solubility	anhydrous insoluble in ethanol pentahydrate soluble in methanol 10.4 g/L (18 °C) insoluble in ethanol
Refractive index (nD)	1.514 (pentahydrate)
Structure
Crystal structure	Orthorhombic (chalcocyanite), space group Pnma, oP24, a = 0.839 nm, b = 0.669 nm, c = 0.483 nm[1] Triclinic (pentahydrate), space group P1, aP22, a = 0.5986 nm, b = 0.6141 nm, c = 1.0736 nm, α = 77.333°, β = 82.267°, γ = 72.567°[2]
Thermochemistry
Standard molar entropy So298	109.05 J K−1 mol−1
Hazards
MSDS	anhydrous pentahydrate
EU Index	029-004-00-0
EU classification	Harmful (Xn) Irritant (Xi) Dangerous for the environment (N)
R-phrases	R22, R36/38, R50/53
S-phrases	(S2), S22, S60, S61
NFPA 704	0 2 1
Flash point	Non-inflammable
LD50	300 mg/kg (oral, rat) 87 mg/kg (oral, mouse) 470 mg/kg (oral, mammal)
Related compounds
Other cations	Nickel(II) sulfate Zinc sulfate
Y sulfate (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Copper(II) sulfate, also known as cupric sulfate, is the chemical compound with the chemical 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, whereas the pentahydrate (CuSO₄·5H₂O), the most commonly encountered salt, is bright blue. Copper sulfate exothermically dissolves in water to give the aquo complex [Cu(H₂O)₆]²⁺, which has octahedral molecular geometry and is paramagnetic. Other names for copper(II) sulfate are "blue vitriol" and "bluestone".^[3]

Preparation and occurrence

Preparation of copper(II) sulfate by electrolyzing sulfuric acid, using copper electrodes

Copper sulfate is produced industrially by treating copper metal or its oxides with sulfuric acid. For laboratory use, copper sulfate is usually purchased.

The anhydrous form occurs as a rare mineral known as chalcocyanite. The hydrated copper sulfate occurs in nature as chalcanthite (pentahydrate), and two more rare ones: bonattite (trihydrate) and boothite (heptahydrate).

Chemical properties

Copper(II) sulfate pentahydrate decomposes before melting at 150 °C, losing two water molecules at 63 °C, followed by two more at 109 °C and the final water molecule at 200 °C.^[4][5]

Dehydration proceeds by decomposition of the tetraaquacopper(2+) moeity, two opposing aqua groups are lost to give a diaquacopper(2+) moeity. The second dehydration step occurs with the final two aqua groups are lost. Complete dehydration occurs when the only unbound water molecule is lost.

At 650 °C, copper(II) sulfate decomposes into copper(II) oxide (CuO) and sulfur trioxide (SO₃).

Its blue color is due to water of hydration. When heated in an open flame the crystals are dehydrated and turn grayish-white.^[6]

Copper sulfate reacts with concentrated hydrochloric acid. In the reaction the blue solution of copper(II) turns green, due to the formation of tetrachlorocuprate(II):

Cu²⁺ + 4 Cl^– → CuCl₄^2–

It also reacts with more reactive metals than copper (e.g. Mg, Fe, Zn, Al, Sn, Pb etc.):

CuSO₄ + Zn → ZnSO₄ + Cu

CuSO₄ + Fe → FeSO₄ + Cu

CuSO₄ + Mg → MgSO₄ + Cu

CuSO₄ + Sn → SnSO₄ + Cu

3 CuSO₄ + 2 Al → Al₂(SO₄)₃ + 3 Cu

The copper formed is deposited on the surface of the other metal. The reaction stops when no free surface of the metal is present anymore.

Uses

As a herbicide, fungicide and pesticide

Copper sulfate pentahydrate is a fungicide.^[7] However, some fungi are capable of adapting to elevated levels of copper ions.^[8] Mixed with lime it is called Bordeaux mixture and used to control fungus on grapes, melons, and other berries.^[9] Another application is Cheshunt compound, a mixture of copper sulfate and ammonium carbonate used in horticulture to prevent damping off in seedlings. Its use as a herbicide is not agricultural, but instead for control of invasive aquatic plants and the roots of plants near pipes containing water. It is used in swimming pools as an algaecide. A dilute solution of copper sulfate is used to treat aquarium fish for parasitic infections,^[10] and is also used to remove snails from aquariums. Copper ions are highly toxic to fish, so care must be taken with the dosage. Most species of algae can be controlled with very low concentrations of copper sulfate. Copper sulfate inhibits growth of bacteria such as Escherichia coli.

For most of the twentieth century, chromated copper arsenate (CCA) was the dominant type of wood preservation for uses other than deep driven piles, utility poles, and railroad ties. To make pressure-treated wood, a large cylinder is filled with an aqueous chemical bath. Copper sulfate pentahydrate is dissolved in the water along with other additives prior to the lumber being placed inside the cylinder. When the cylinder is pressurized, the chemicals are absorbed by the wood, giving the wood fungicidal, insecticidal, and UV-light-reflecting properties that help preserve it.

Niche uses

Being a relatively benign and cheap reagent, copper(II) sulfate has attracted many niche applications over the centuries.

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. The blood is tested by dropping it into a solution of copper sulfate of known specific gravity – blood which contains sufficient hemoglobin sinks rapidly due to its density, whereas blood which does not, floats or sinks less rapidly.^[11]

In a flame test, its copper ions emit a deep blue-green light, much more blue than the flame test for barium.

Organic synthesis

Copper sulfate is employed in organic synthesis.^[12] The anhydrous salt catalyses the transacetylation in organic synthesis.^[13] The hydrated salt reacts with potassium permanganate to give an oxidant for the conversion of primary alcohols.^[14]

Chemistry education

Copper sulfate is a commonly included chemical in children's chemistry sets and is often used to grow crystals in schools and in copper plating experiments. Because of 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 color, and is known as blue copperas.^[15] Copper(II) sulfate pentahydrate can easily be produced by crystallization from solution as copper(II) sulfate is quite hydroscopic.

In an illustration of a "single metal replacement reaction," iron is submerged in a solution of copper sulfate. Upon standing, iron reacts, producing iron(II) sulfate, and copper precipitates.

Fe + CuSO₄ → FeSO₄ + Cu

Lowering a zinc etching plate into the copper sulfate solution.

Medical

Copper sulfate was also used in the past as an emetic.^[16] It is now considered too toxic for this use.^[17] It is still listed as an antidote in the World Health Organization's ATC code V03.^[18]

Art

In 2008, the artist Roger Hiorns filled an abandoned waterproofed council flat in London with 75,000 liters of copper sulfate solution. The solution was left to crystallize for several weeks before the flat was drained, leaving crystal-covered walls, floors and ceilings. The work is titled Seizure.^[19]

Etching

Copper sulfate is also used to etch zinc plates for intaglio printmaking.^[20][21]

Toxicological effects

Copper sulfate is an irritant.^[22] The usual routes by which humans can receive toxic exposure to copper sulfate are through eye or skin contact, as well as by inhaling powders and dusts.^[23] Skin contact may result in itching or eczema.^[24] Eye contact with copper sulfate can cause conjunctivitis, inflammation of the eyelid lining, ulceration, and clouding of the cornea.^[25]

Upon acute oral exposure, copper sulfate is only moderately toxic.^[26] According to studies, the lowest dose of copper sulfate that had a toxic impact on humans is 11 mg/kg.^[27] Because of its irritating effect on the gastrointestinal tract, vomiting is automatically triggered in case of the ingestion of copper sulfate. However, if copper sulfate is retained in the stomach, the symptoms can be severe. After 1–12 grams of copper sulfate are swallowed, such poisoning signs may occur as a metallic taste in the mouth, burning pain in the chest, nausea, diarrhea, vomiting, headache, discontinued urination, which leads to yellowing of the skin. In case of copper sulfate poisoning, injury to the brain, stomach, liver, or kidneys may also occur.^[25]

References

1. ^ Kokkoros, P. A.; Rentzeperis, P. J. (1958). "The crystal structure of the anhydrous sulphates of copper and zinc". Acta Crystallographica 11 (5): 361–364. doi:10.1107/S0365110X58000955. 
2. ^ Bacon G.E. and Titterton D.H. (1975). "Neutron-diffraction studies of CuSO4· 5H2O and CuSO4· 5D2O". Z. Kristallogr. 141 (5–6): 330–341. doi:10.1524/zkri.1975.141.5-6.330. 
3. ^ "Copper(II) sulfate MSDS". Oxford University. http://ptcl.chem.ox.ac.uk/MSDS/CO/copper_II_sulfate.html. Retrieved 2007-12-31. 
4. ^ Andrew Knox Galwey, Michael E. Brown (1999). Thermal decomposition of ionic solids. Elsevier. pp. 228–229. ISBN 0444824375. http://books.google.com/books?id=i9nyvTYBQtAC&pg=PA229. 
5. ^ Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman (2001). Inorganic chemistry. Academic Press. p. 1263. ISBN 0123526515. http://books.google.com/books?id=LxhQPdMRfVIC&pg=PA1263. 
6. ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5. 
7. ^ Johnson, George Fiske (1935). "The Early History of Copper Fungicides". Agricultural History 9 (2): 67–79. JSTOR 3739659. 
8. ^ Parry, K. E.; Wood, R. K. S. (1958). "The adaption of fungi to fungicides: Adaption to copper and mercury salts". Annals of Applied Biology 46 (3): 446. doi:10.1111/j.1744-7348.1958.tb02225.x. 
9. ^ "Uses of Copper Compounds: Copper Sulfate's Role in Agriculture". Copper.org. http://www.copper.org/applications/compounds/copper_sulfate02.html. Retrieved 2007-12-31. 
10. ^ "All About Copper Sulfate". National Fish Pharmaceuticals. http://www.fishyfarmacy.com/Q&A/all_about_copper.html. Retrieved 2007-12-31. 
11. ^ Barbara H. Estridge, Anna P. Reynolds, Norma J. Walters (2000). Basic Medical Laboratory Techniques. Thomson Delmar Learning. p. 166. ISBN 0766812065. 
12. ^ Hoffman, R. V. (2001). Copper(II) Sulfate, in Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rc247. 
13. ^ Hulce, M. Mallomo, J. P.; Frye, L. L.; Kogan, T. P.; Posner, G. H. (1990), "(S)-( + )-2-(p-Toluenesulfinyl)-2-Cyclopentanone: Precursor for Enantioselective Synthesis of 3-Substituted Cyclopentanones", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV7P0495 ; Coll. Vol. 7: 495 
14. ^ 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", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv9p0462 ; Coll. Vol. 9: 462 
15. ^ "Process for the preparation of stable copper (II) sulfate monohydrate applicable as trace element additive in animal fodders". http://www.freepatentsonline.com/4315915.html. Retrieved 2009-07-07. 
16. ^ Holtzmann NA, Haslam RH (July 1968). "Elevation of serum copper following copper sulfate as an emetic". Pediatrics 42 (1): 189–93. PMID 4385403. http://pediatrics.aappublications.org/cgi/content/abstract/42/1/189. 
17. ^ Olson, Kent C. (2004). Poisoning & drug overdose. New York: Lange Medical Mooks/McGraw-Hill. p. 175. ISBN 0-8385-8172-2. 
18. ^ V03AB20
19. ^ "Seizure homepage". Artangel.org.uk. http://www.artangel.org.uk/projects/2008/seizure. Retrieved 2009-09-21. 
20. ^ Bordeau etch. Greenart.info (2009-01-18). Retrieved on 2011-06-02.
21. ^ The Chemistry of using Copper Sulfate Mordant. Ndiprintmaking.ca (2009-04-12). Retrieved on 2011-06-02.
22. ^ Windholz, M., ed. 1983. The Merck Index. Tenth edition. Rahway, NJ: Merck and Company.
23. ^ U. S. Environmental Protection Agency. 1986 Guidance for reregistration of pesticide products containing copper sulfate. Fact sheet no 100. Office of Pesticide Programs. Washington, DC.
24. ^ TOXNET. 1975–1986. National library of medicine's toxicology data network. Hazardous Substances Data Bank (HSDB). Public Health Service. National Institute of Health, U. S. Department of Health and Human Services. Bethesda, MD: NLM.
25. ^ ^{a b} Clayton, G. D. and F. E. Clayton, eds. 1981. Patty's industrial hygiene and toxicology. Third edition. Vol. 2, Part 6 Toxicology. NY: John Wiley and Sons. ISBN 0471012807
26. ^ 1986. Guidance for reregistration of pesticide products containing copper sulfate. Fact sheet no 100. Office of Pesticide Programs. Washington, DC.
27. ^ National Institute for Occupational Safety and Health (NIOSH). 1981–1986. Registry of toxic effects of chemical substances (RTECS). Cincinnati, OH: NIOSH.

External links

• International Chemical Safety Card 0751
• International Chemical Safety Card 1416
• National Pollutant Inventory – Copper and compounds fact sheet