Four principal species are present initially in the reaction mixture: copper (II)
ions [actually Cu(H2O)6
2+ ions], ammonia molecules (NH3), sulfate ions
(SO4
2-), and water. The product of the synthesis is therefore presumed to be
formed by the reaction of two or more of these species. Ethanol is also present,
but it is an indirect participant in the reaction. In aqueous solutions ethanol,
which is miscible with water but of lower dielectric constant, decreases the
solubility of ionic compounds. The marked color change that occurs in the
reaction is an important clue to the nature of the product. The product is
analyzed for copper (II) ions, sulfate ions, and ammonia molecules. Water is
determined as the mass of a sample of the compound that is not accounted for
as one of these three species