In the case of an electrochemical cell formed between half cells, Pb+2 /Pb and Cu+2 /Cu, Pb /Pb2+ serves as the anode and Cu2+/Cu as the cathode. Consequently, Pb is oxidized to Pb2+ ions in the spontaneous anode reaction. If aqueous NaCl solution is used in the salt bridge, the Cl- ions will form a precipitate of PbCl2 at the anode-salt bridge interface, which will interfere with the passage of electrons adversely, eventually stopping the cell reactions altogether after some time.