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".
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; 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.
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
). When heated in an open flame the crystals are dehydrated and turn grayish-white.
As an herbicide, fungicide, 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. 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 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 for various parasitic infections, 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
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.
In a flame test, its copper ions emit a deep blue-green light, much more blue than the flame test for barium.
Copper sulfate is employed in organic synthesis
. The anhydrous salt catalyses the transacetalization
in organic synthesis. The hydrated salt reacts with potassium permanganate
to give an oxidant for the conversion of primary alcohols.
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
ribbon is placed in an aqueous solution
. 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.
In an illustration of a "single metal replacement reaction," iron is submerged in a solution of copper sulfate. Upon standing, iron dissolves and copper precipitates.
- Fe + CuSO4 → FeSO4 + Cu
The copper can also be electroplated to the iron.
Other applications include hair dyes
, coloring glass, processing of leather
and in pyrotechnics as a green colorant. It is used by some organic cattle farmers in solution as a footbath as a way of increasing the hardness of hoof, thereby reducing incidence of lameness. It also can change the color of a flame if added to it in its dry state, making it green.