Tetraammincopper(II) sulfate is a complex compound which has a dark blue color. The solution of this compound was prepared from copper(II) sulfate and ammonia solutions.
First, I've made a solution of copper(II) sulfate which has light blue color.
Then to this solution I've added ammonia. See what happened.
In the bottom of the tube we see copper(II) sulfate solution. Then there is a zone where we can see a solid copper(II) hydroxide which is formed by reaction of ammonium hydroxide and copper(II) sulfate. At the top of the test tube where is the excess of ammonia solution, copper(II) hydroxide dissolves and the tetraammincopper(II) complex ion is formed.
Of course other compounds can be found in this solution (ammonium sulfate, tetraammincopper(II) hydroxide).
Well, this compound is charming because of its dark blue color, but if you want to have it at home or somewhere else, you have to make sure that it's well closed unless you want to smell like a toilet which wasn't cleaned for weeks...
