I Have 2 soluble salts in aqueous distilled water solution. I know that one of the salts is K2SO4 and I know that the anion of the second salt is Cl-. I know that the second salt is either MgCl2, NaCl, CaCl2, or KCl. I tested for the anion for the second salt by adding AgNO3 into the solution and observing a white precipitate. When I added NaOH to it, I observed that the cloudy white precipitate disappeared and turned into small black precipitate which then settled to the bottom of the tube. Is there any way to get the cation of the second salt with this information, and are there any other test(s) I can do to find what the cation is for the second salt?