Copper sulphate reactions. Image 3 of 3. This show the product of a reaction between copper sulphate solution with first ammonia and then hydrochloric acid. The addition of hydrochloric acid causes tetrachlorocuprate II complex ions ((CuCl4)2-) to form. These are yellow in colour, and mix with the blue copper ions to produce green. The initial copper sulphate solution can be seen in image A500/561. The reaction of that solution with ammonia can be seen in image A500/562.