What color is copper sulfate

Copper (II) sulfate
Copper (II) sulfate pentahydrate
Copper (II) sulfate
Copper (II) sulfate pentahydrate
159.609 g / mol
249.685 g / mol

0.01 mg / m3 A (MAK)
3.6 g / cm3
2.286 g / cm3
+560 ° C (decomposition)
100g H2O dissolve 20.77g (L) (anhydrous)
100g H2O dissolve 36.2 g (L) (pentahydrate)

White powder (anhydrous)

Blue, crystalline powder (pentahydrate)

Special notes for schools
Copper (II) sulphate is toxic; when taken internally, it causes severe nausea. According to the GHS classification, it is assigned to category 4 within the corresponding hazard class, which is why fatal poisoning occurs very rarely in connection with the induced nausea. Circulatory disorders arise as a result of oral intake, liver and kidney damage are also possible. Repeated and prolonged skin contact can cause allergic reactions on the skin. On contact with the eyes, inflammatory or purulent reactions occur in the eye. Therefore, you have to wear protective goggles and always wash your hands well after working. Copper (II) sulphate can damage aquatic organisms, which endangers the ecological balance in water bodies. Under no circumstances may waste be disposed of in the sewage system.

The pentahydrate is blue, the anhydrous form white.

When the pentahydrate is heated, the water escapes.

Copper (II) sulfate pentahydrate forms blue crystals according to the triclinic crystal system. It occurs naturally in the mineral chalcanthite. Copper sulfate pentahydrate was previously known as "copper vitriol". Anhydrous copper (II) sulfate is a white powder that turns slightly blue with humidity. It dissolves well in water and forms a blue solution. At +20 ° C, 1000 grams of the saturated copper (II) sulfate pentahydrate solution contain 17.2 percent by mass. The density of this solution is 1.1965 g / cm3. The solubility increases when heated:

Water solubility (L): 100g H.2O solve Copper (II) sulfate anhydrous

0 ° C
20 ° C
40 ° C
60 ° C
80 ° C
100 ° C
25.5 g
36.2 g
48.0 g
60.0 g
70.0 g
83.0 g

Water solubility (L): 100g H.2O solve Copper (II) sulfate pentahydrate

0 ° C
20 ° C
40 ° C
60 ° C
80 ° C
100 ° C
14.8 g
20.77 g
29.0 g
39.1 g
53.6 g
73.6 g

When heated, the blue pentahydrate loses its crystal water and finally turns white. The crystal water is released in stages. At +95 ° C a trihydrate forms, at +116 ° C a monohydrate and at around +200 ° C anhydrous, white copper (II) sulfate is obtained. The process is reversible, the addition of water leads to the pentahydrate again.

Heating: CuSO4 • 5 H.2O (blue) CuSO4 (white) + 5 H.2O
Addition of water: CuSO4 (white) + 5 H.2O CuSO4 • 5 H.2O (blue)

When heated very strongly to over +560 ° C, the anhydrous copper (II) sulfate breaks down into copper oxide, sulfur dioxide and oxygen. The flame sample shows a blue-green flame color. The aqueous copper (II) sulfate solution has a disgusting, metallic taste. If you filter a hot, saturated solution into a Petri dish, triclinic crystals form on cooling:

Crystal growth in the petri dish

Triklines crystal grown on wool thread

If concentrated ammonia solution is added to a concentrated copper (II) sulphate solution, an ultramarine blue precipitate is formed. After filtering with the help of a frit and washing with ethanol or denatured alcohol at the same time, tetraammine copper (II) sulfate monohydrate can be obtained after drying:

CuSO4 + 4 NH3 + H2O [Cu (NH3)4]SO4 • H2O

When adding ammonia solution to copper (II) sulfate solution
an ultramarine blue precipitate is formed.

The cobalt blue powder obtained in this way is not stable in the air; it weathers to a green powder. It is also visually different from the turquoise-blue copper (II) sulfate pentahydrate. It contains a tetraamine copper complex. Copper (II) sulfate pentahydrate and its aqueous solution also contain complexes. Hence, the common name is actually incorrect.

Copper (II) sulfate pentahydrate (left) and
Tetraammine copper (II) sulfate monohydrate (right)
Copper (II) sulfate can be produced in the laboratory by dissolving copper (II) oxide in dilute sulfuric acid:

CuO + H2SO4 (aq) CuSO4 + H2O

Hot, concentrated sulfuric acid does not react with copper to develop hydrogen, but instead forms copper sulfate, sulfur dioxide and water:

Cu + 2H2SO4  CuSO4 + SO2 + 2 H.2O

In industrial production, copper waste and waste that occurs during the roasting of sulphidic ores are mixed with hot, dilute sulfuric acid. The reaction succeeds with the addition of atmospheric oxygen:

2 Cu + 2 H2SO4 (aq) + O2  2 CuSO4 + 2 H.2O
Copper (II) sulfate is used to produce color pigments and copper salts such as copper (II) oxide. It is used as a fungicide for seeds, for the preservation of wood and animal hide, for copper plating in galvanic baths, for copperplate etching in printing works or in dyeing works for the post-treatment of dyeings. It was used in medicine as an emetic and tapeworm remedy. Today this method is only used in veterinary medicine. In fireworks it is added as a coloring component to create the blue flame color. In the laboratory, white copper (II) sulfate can be used to detect water. This is also suitable as a drying agent.

The water detection paper turns blue with water.

Further information and media
Information about the sulfates
Student exercises for growing crystals
Research assignments: Growing crystals
Student exercises: exothermic and endothermic reactions (experiments with copper sulfate)