Tetraamminecopper(II) sulfate

From Wikipedia, the free encyclopedia
  (Redirected from Cuprammonium)
Jump to: navigation, search
Tetraamminecopper(II) sulfate
Ball-and-stick model of the Tetraamminecopper(II) cation
Copper tetrammine sulfate.jpg
CAS number 14283-05-7 YesY
PubChem 61513
Molecular formula [Cu(NH3)4(H2O)n]SO4
Molar mass 245.79 g/mol
Appearance dark blue-purple solution or crystals
Odor Ammonia
Density 1.81 g/cm3
Solubility in water 18.5 g/100 g (21.5 °C)[1]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Tetraamminecopper(II) sulfate is the inorganic compound with the formula [Cu(NH3)4(H2O)n]SO4. This dark blue solid is a metal complex. It is closely related to Schweizer's reagent, which is used for the production of cellulose fibers in the production of rayon.

Preparation, structure, properties[edit]

This compound can be prepared by adding concentrated solution of ammonia to a saturated aqueous solution of copper sulfate followed by precipitation of the product with ethanol. The deep blue crystalline solid tends to hydrolyse and evolve (release) ammonia upon standing in air.[1] The correct concentrations of ammonia and copper sulfate solution can be determined by colorimetry. The combination of the correct concentrations will produce the highest absorbance read out on the colorimeter and as a result the formula of the complex can be verified.

In the solid state, the salt contains the [Cu(NH3)4H2O]2+ dication, which has a square pyramidal molecular geometry. The Cu-N and Cu-O distances are about 210 and 233 pm.[2]


The characteristic deep blue colour of the tetraammine complex is found in brass and copper alloys where attack from ammonia has occurred leading to cracking. The problem was first found in ammunition cartridge cases when they were stored near animal waste, which produced trace amounts of ammonia. This type of corrosion is known as season cracking.

An ammonia solution of tetraamminecopper(II) sulfate.


  1. ^ a b O. Glemser, H. Sauer "Tetraamminecopper (II) Sulfate" Handbook of Preparative Inorganic Chemistry, 2nd Ed., Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1021.
  2. ^ Morosin "The Crystal Structures of Copper Tetraammine Complexes. A. Cu(NH3)4SO4.H2O and Cu(NH3)4SeO4" Acta Cryst. 1969, vol. B25, pp. 19-30. doi:10.1107/S0567740869001725

External links[edit]