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There are very few suitable low melting point salts. Lead bromide has a low melting point
and makes an interesting electrolysis experiment. Potassium bromide may have too high a
melting point, 682oC, to melt easily. The lead bromide is melted in a 100 mL hard glass
beaker, or in a crucible. The carbon electrodes are supported by a strip of wood with two
holes bored 2 cm apart for the electrodes. Connect crocodile clips to the rods and complete
the circuit with a torch bulb, to indicate when a current is flowing, and a 12-volt torch
battery or cells wired in series. The electrodes can be labelled positive and negative. The
only ions present in this melt are the bromide and lead ions. Bromine is readily seen coming
off at the positive electrode, which is the anode. The fact that bromine appears only at the
positive electrode helps in the understanding of the existence of a negative bromide ion.
Lead has both a lower melting point and a greater density than lead bromide and therefore
appears as a melt at the bottom of the beaker. The small globule of lead, which accumulates
at the negative electrode, the cathode, can be seen after about 10 minutes of electrolysis.
Decant off the molten lead bromide carefully into another crucible. The electric current
has split up crystalline lead bromide into bromine gas and lead metal.
sharon kalunda answered the question on April 12, 2019 at 08:24
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