Some salts containing two different metallic elements give test for only one of them in solution, such salts are

Some salts containing two different metallic elements give test for only one of them in solution, such salts are complex salts. For example, K₄[Fe(CN)₆] is a complex salt. In aqueous solution, it will dissociate into K⁺ ions and [Fe(CN)₆]⁴⁻ ions. The aqueous solution of K₄[Fe(CN)₆] will give test for K⁺ ions only. It will not give test for Fe²⁺ ions.