Tetraamminecopper(II) sulfate monohydrate, or more precisely tetraammineaquacopper(II) sulfate, is the salt with the formula , or more precisely [. This dark blue to purple solid is a sulfuric acid salt of the metal complex (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. The correct concentrations of ammonia and copper(II) sulfate solution needed to synthesize the complex 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.
Synthesis
This compound can be prepared by adding concentrated aqueous solution of ammonia to a saturated aqueous solution of copper(II) sulfate pentahydrate followed by precipitation of the product with ethanol or isopropanol.
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Uses
The dark blue-violet color is used as a positive test to verify the presence of in a solution.