Copper(II) sulfate 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, whereas the pentahydrate, the most commonly encountered salt, is bright blue. 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). Archaic names for copper(II) sulfate are "blue vitriol" and "bluestone".[1]
Preparation
Preparation of copper(II) sulfate by electrolyzing sulfuric acid, using copper electrodes
Since it is available commercially, copper sulfate is usually purchased and 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; this oxide can be generated with the addition of hydrogen peroxide to the acid. It may also be prepared by electrolyzing sulfuric acid, using copper electrodes.
Chemical properties
Copper(II) sulfate pentahydrate decomposes before melting, 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). Its blue color is due to water of hydration. When heated in an open flame the crystals are dehydrated and turn grayish-white.[2]
Uses
As a herbicide, fungicide and pesticide
Copper sulfate pentahydrate is a fungicide. Mixed with lime it is called Bordeaux mixture and used to control fungus on grapes, melons, and other berries[3]. 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 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 for various parasitic infections,[4] 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. Copper sulfate inhibits growth of bacteria such as E. coli.
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 slowly.[5]
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.[6] The anhydrous salt catalyses the transacetalization in organic synthesis.[7] The hydrated salt reacts with potassium permanganate to give an oxidant for the conversion of primary alcohols.[8]
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. 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 color, and is known as blue copperas.[9]
In an illustration of a "single metal replacement reaction," iron is submerged in a solution of copper sulfate. Upon standing, iron dissolves, producing iron(II) sulfate, and copper precipitates.
- Fe + CuSO4 → FeSO4 + Cu
The copper can also be electroplated to the iron.[citation needed]
Copper sulfate was also used in the past as an emetic.[10] It is now considered too toxic for this use.[11] It is still listed as an antidote in the World Health Organization's ATC code V03.[12]
References
- ^ "Copper(II) sulfate MSDS". Oxford University. http://ptcl.chem.ox.ac.uk/MSDS/CO/copper_II_sulfate.html. Retrieved on 2007-12-31.
- ^ Holleman, A. F.; Wiberg, E. Inorganic Chemistry Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ "Uses of Copper Compounds: Copper Sulfate's Role in Agriculture". Copper.org. http://www.copper.org/applications/compounds/copper_sulfate02.html. Retrieved on 2007-12-31.
- ^ "All About Copper Sulfate". National Fish Pharmaceuticals. http://www.fishyfarmacy.com/Q&A/all_about_copper.html. Retrieved on 2007-12-31.
- ^ Barbara H. Estridge, Anna P. Reynolds, Norma J. Walters (2000). Basic Medical Laboratory Techniques. Thomson Delmar Learning. pp. 166. ISBN 0766812065.
- ^ Hoffman, R. V. "Copper(II) Sulfate" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley & Sons. DOI: 10.1002/047084289X.rc247
- ^ 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.; Coll. Vol. 7: 495.
- ^ 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.; Coll. Vol. 9: 462.
- ^ http://66.102.9.104/search?q=cache:Jj02FqBkPCAJ:www.freepatentsonline.com/4315915.html+Blue+copperas&hl=en&ct=clnk&cd=3&gl=uk
- ^ 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.
- ^ Olson, Kent C. (2004). Poisoning & drug overdose. New York: Lange Medical Mooks/McGraw-Hill. pp. 175. ISBN 0-8385-8172-2.
- ^ V03AB20
External links
-sulfate-pentahydrate-sample.jpg)
-sulfate-unit-cell-3D-balls.png)
-sulfate-3D-vdW.png)
