F.5 CHem

Just use soultion with electrolyte to soak the filter paper for a salt bridge.

However, there are some restrictions.
1) The salt bridge must conduct electricity. i.e. the salt bridge has mobile ions

usually many ionic substances can be used

2)The substances in the salt bridge do not react with the solution in each half-cell.

If ZnCl2 is used in one of the half-cells, then AgNO3 must not be used to make the salt bridge because they react:
Ag+(aq) + Cl-(aq) à AgCl(s)
Which is know as precipitate reaction

So we usually use a ionic substances whose cation and anion do not form precipitates.
e.g all sodium salts are soluble
e.g all nitrates are soluble

hence NaNO3 is a ideal solution for the salt bridge.