Does Mercury change the colour of Gold from yellow to white? Most of the metals dissolve in Mercury. Just like salt, sugar dissolve in water. Salt and sugar are in crystal form and when they are in water atoms in them separate. Atoms of gold also get separated in Mercury. Not only gold other metals like copper, zinc also dissolve in water and for amalgams. When a small amount of Mercury touches the gold, amalgam is formed only in that place. Mercury has no stability in air and so the atoms that touch the gold react with the oxygen in the air to produce Mercuric Acid and it looks like a white spot on gold. To remove the spot rub the gold with cotton dipped in Stannous Chloride and rub repeatedly with copper or zinc.