Tetraamminecopper(II) sulfate
chemical compound
Tetraamminecopper(II) sulfate monohydrate, or more precisely tetraammineaquacopper(II) sulfate, is the salt with the formula [Cu(NH3)4]SO4·H2O, or more precisely [Cu(NH3)4(H2O)]SO4. This dark blue to purple solid is a sulfuric acid salt of the metal complex [Cu(NH3)4(H2O)]2+ (tetraammineaquacopper(II) cation). It is closely related to Schweizer's reagent, which is used for the production of cellulose fibers in the production of rayon.
Properties
The deep blue crystalline solid tends to hydrolyse and evolve (release) ammonia upon standing in air. It is fairly soluble in water. The brilliant dark blue-violet color of tetraamminecopper(II) sulfate solution is due to the presence of [Cu(NH3)4]2+ (tetraamminecopper(II) cation).
Corrosion
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.
Structure
The solid state structure of tetraamminecopper(II) sulfate monohydrate confirms that the compound is a salt.
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