Schweizer's reagent
Schweizer's reagent is the chemical complex
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...

 tetraamminediaquacopper dihydroxide, [Cu(NH3)4(H2O)2](OH)2. It is prepared by precipitating copper(II) hydroxide
Copper(II) hydroxide
Copper hydroxide is the hydroxide of the metal copper with the chemical formula of Cu2. Copper hydroxide is a pale blue, gelatinous solid. Some forms of copper hydroxide are sold as "stabilized" copper hydroxide, quite likely a mixture of copper carbonate and hydroxide...

 from an aqueous solution of copper sulfate using sodium hydroxide or ammonia, then dissolving the precipitate in a solution of ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...


When the entire amount of copper is precipitated as hydroxide, it is a good idea to filter it and dispose of the filtrate and rinse the precipitate from sulfate and other excess ions.

It forms a deep azure solution. If the solution is evaporated, it leaves light blue precipitate of copper hydroxide. This is because the formation of the tetraminocupric complex is reversible and ammonia evaporates together with the water. If the evaporation is conducted under stream of ammonia, then deep blue needle-like crystals are formed. These crystals should be kept in isolation or in ammonia atmosphere.

Schweizer's reagent finds use in production of cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 products such as rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...

 and cellophane
Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria and water makes it useful for food packaging...

, because wood-pulp, cotton fiber, and other natural cellulose sources are soluble in the solution. Dissolved cellulose precipitates when the solution is acidified.
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