# Chemistry - How to identify an emerald green solution with possibly two anions?

You can have two different anions if your solution is a mixture of two different metal salts, a chloride and a sulfate. The color change from green to blue upon dilution with water fits well with $$\ce{Cu^2+}$$ being the corresponding cation. Concentrated solutions of $$\ce{CuCl2}$$ are green due to the presence of chlorocuprates, like $$\ce{[CuCl3]^{-}}$$ and $$\ce{[CuCl4]^{2-}}$$. When water is added, a stepwise ligand exchange takes place, and the pale blue color of $$\ce{[Cu(H2O)6]^{2+}}$$ starts to appear. The image below shows copper(II) chloride solutions of different concentrations: Green when the chloride concentration is high, and blue when it is lower (Wikipedia: copper chloride).

In summary, the observations (color change, precipitates) indicate that you have an aqueous solution of $$\ce{CuCl2}$$ and $$\ce{CuSO4}$$.