Schweizer's reagent

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Ball-and-stick model of the tetraamminediaquacopper (II) cation, [Cu(NH3)4(H2O)2]2+

Schweizer's reagent is the chemical complex tetraamminediaquacopper dihydroxide, [Cu(NH3)4(H2O)2](OH)2. It is prepared by precipitating copper(II) hydroxide from an aqueous solution of copper sulfate using sodium hydroxide or ammonia, then dissolving the precipitate in a solution of ammonia.

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 products such as rayon and cellophane, 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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References[edit]

  • Walther Burchard, Norbert Habermann, Peter Klüfers, Bernd Seger, Ulf Wilhelm (1994). "Cellulose in Schweizer's Reagent: A Stable, Polymeric Metal Complex with High Chain Stiffness". Angewandte Chemie International Edition in English 33 (8): 884–887. doi:10.1002/anie.199408841. 
  • Eduard Schweizer (1857). "Das Kupferoxyd-Ammoniak, ein Auflösungsmittel für die Pflanzenfaser". J Prakt. Chem. 72 (1): 109–111. doi:10.1002/prac.18570720115. 
  • George B Kauffman (1984). "Eduard Schweizer (1818-1860): The Unknown Chemist and His Well-Known Reagent". J. Chem. Educ. 61 (12): 1095–1097. doi:10.1021/ed061p1095.