purpose of the salt bridge in electrochemical cells

One way of looking at it is to say that the salt bridge allows the current to continue to flow. That is, it supplies the the continuous path which every continuous flow of current requires.

> I thought electrons flowed from a high concentration of e- to a lower concentration of e-
other things being equal, yes.

consider:
air flows from a high concentration of air molecules to a lower concentration of air molecules
If you try to pump air from one sealed container to another sealed container, eventually pressure will build up, making it harder to pump.

perhaps i don't fully understand why you need a continuous path.

I thought i understood that you needed a continous path in an electric circuit so the electrons could keep flowing but in the electrochemical cell it is ions from the electrolyte flowing across the salt bridge and not the electrons.

Perhaps electrons will flow to an area of more positive charge where the positive charge isn;t necessarily due to 'less electrons' but simply due to less negative charge (where the charge could come from the ions in the electrolyte)

Think of it as a physical exchange payoff, and to expand on ozo's idea of pressure, lets go really broad general analogy:  Think of people entering a large, enclosed volume like a huge gymnasium or theater, that is sealed airtight except the doorway where people enter.
As people enter, they displace a volume of air back behind them.  If people didn't displace the air, the air pressure would increase strongly as they volume for the air in the room decreased, and eventually, and it would grow more and more difficult for each person to enter into the room until eventually the pressure would resist anyone from entering.

The salt bridge allows for the exchange of the counterforces to allow the current to flow continuously (until depleting reactions, or completely filling the gymnsasium...).  You could also think of it as the empty-buckets being returned in a bucket-brigade to facilitate the transportation of more water up the other side of the bucket brigade - sure the brigade can transport water in one direction with their system, but eventually, they run out of the ability to produce buckets of water unless they are provided with a supply of them, and the other end of the chain is building up a huge supply of them that gets in their way -- so return the buckets at the same rate that you pass the full ones along, and you now have a continuous current of waterbuckets passing along without disruptions or slowing down until the water is depleted (or the fire is depleted;)

Salt bridge allows for the separation of the two end-events to participate in a needed exchange in order to close a loop.

just as there is a limit to how much air you can pump from one sealed container to another before the tenancy to flow from higher concentration to lower makes it difficult to pump, there is a limit to how many electrons you can push from one isolated cell to another.
whereas if you had two connected containers, you could keep pumping air from one to the other for as long as you had energy to do so

Hi

Thanks very much for the answers and the effort to use analogies. I would find it useful if you could look at the points I made:

I thought i understood that you needed a continous path in an electric circuit so the electrons could keep flowing but in the electrochemical cell it is ions from the electrolyte flowing across the salt bridge and not the electrons.

"erhaps electrons will flow to an area of more positive charge where the positive charge isn;t necessarily due to 'less electrons' but simply due to less negative charge (where the charge could come from the ions in the electrolyte)"

To me the salt bridge is removing a build up of negative charge but it isnt removing the build up of electrons. I thought you had to remove the electron build up but that could be my old misconceptions from something i learnt many years ago