In a 50 ml beaker equiped with a stirring bar, dissolve 1.25 g of cupric sulfate pentahydrate in 25 ml of water. Stir the mixture, and warm to 40 - 50 ºC on a sand bath to aid dissolution. Using a pipet, add 50% ammonium hydroxide to the warm, stirred, light blue solution, until an intense blue color ammonium complex is evident. During this addition, a precipitate of copper hydroxide may form initially, but it will dissolve on further addition of of the ammonium hydroxide solution.
Add 400 mg of sodium hydroxide flakes to the deep blue solution, and the stir the mixture for 15-20 minutes at 55-60 ºC. A light blue solid of copper (II) hydroxide precipitates during this time. Allow the mixture to cool to room temperature and collect the precipitate by vacuum filtration. Wash the blue solid with three 10 ml portions of warm water.
Transfer the solid Cu(OH)2 to a 50 ml beaker, and dissolve it in the minimum amount of 10% acetic acid. Warming on the sand bath with stirring aids the dissolution process. Concentrate the solution nearly to dryness by warming it on a sand bath under a slow stream of nitrogen. Collect the beautiful deep blue crystals that form by filtration using a Hirsch funnel. Dry the product on filter paper.
Experiment from Microscale Inorganic Chemistry, Szafran, Z.; Pike, R. M.; Singh, M.M. John Wiley and Sons, Inc.: New York, 1991.
© 2004 by Lawrence T. Sein. All rights reserved.
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