Passing a current from a metal wire through an electrolyte solution

[sceptichymist]

I am having trouble understanding how current can move through an electrolyte solution that does not contain ions of the metal of which the electrode supplying the current is made. For instance, if a silver wire were submerged in a solution of potassium chloride and, how would current pass into the solution?

I am in a neurobiology lab and we use glass electrodes containing a silver wire in a potassium chloride solution to inject current into living cells. I have been struggling to understand how it is we are doing so. Any help would be appreciated.

 

[Drakkith]

Electrons don't care what material they are in. As long as there is a low enough resistance or high enough voltage, they will move. Can you tell us what you do know about electricity? That way we can respond appropriately.

 

[Integral]

There is little or no electron flow in such solutions. What you have is a ionic solution, the Cl and K ions exist separately in solution. The positive ions will migrate to the negative terminal and the negatives will go to the other. This is due to the electric field in the solution. Seems to me you could be evolving Cl gas a one terminal. Note that my chemistry is ancient so I cannot tell you which, Cl or K, is positive or negative, I cannot tell you exactly what is going to happen. If Borek comes in he will be able to fill in the details.

 

[sceptichymist]

I know that the carriers of charge that move through a metal wire are electrons. I know that the magnitude of current is directly proportional to the magnitude of electric potential difference between the two points it is moving and inversely proportional to the resistance of the material through which it is moving. Also, the carriers of charge responsible for current moving through an electrolyte solution are not lone electrons, but rather atoms with charge imbalances (ions). When an electrode is submerged in a solution and an external voltage drives a current into the electrode, one of the chemical species in the solution is reduced. Often, I have encountered examples of electrodes in solutions containing ions of the electrode, i.e. a copper electrode in a solution of copper II sulfate. What I don't know is, in my example in my original post, what is reduced, and how are we injecting current into the cells?

 

[Drakkith]

Ah ok, my mistake. I neglected to pay attention to the electrolyte part.