Copper Acetate(WSDTY) is supposed to form green solutions. Cupric subacetate or basic cupric acetate can be blue if the ratio of cupric acetate to cupric hydroxide to water is 1:1:5. Drying this removes the water (and the nice blue color) producing copper acetate (green) and copper hydroxide (greenish blue) or copper oxide (brownish black) with further heating.

Not pure but i have toilet cleaner that contains HCl, along with detergents and coloring (blue) it is only 20% HCl. Iron allowed to react with it turns the solution a light yellow. If it was soluble what color would the solution be, assuming you have pure HCl with no coloring? How pure is the muritic acid you get from a hardware store?

I think it is probably fair to assume that the black stuff is some type of Copper salt, right, since what other cations are present in the solution....Sodium, but Na will certianly not plate out and I dont think it could be any Sodium salt since those are usually white and will readily dissolve in water. If it is a Copper salt, then dissolving it in solution will yeild Cu+2 ions which will form a complex with water molecules turning the solution blue. If the solution becomes concentrated enough, it will begin to form complexes with the Chloride ions as well and turn the solution a dark green. it might be Copper(II) Oxide, in which case it will be readily soluble in HCl and yeild a blue solution when dillute (forming CuCl2 (aq)). The toilet bowl cleaner might work as long as you are able to tell a color change if it occurs. The muriatic acid you get at the hardware store is very pure HCl. The stuff I buy is about 37% HCl by weight, the rest being water.

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