Salt bridge

In electrochemistry, a salt bridge or ion bridge is an essential laboratory device discovered over 100 years ago. ^[1] It contains an electrolyte solution, typically an inert solution, used to connect the oxidation and reduction half-cells of a galvanic cell (voltaic cell), a type of electrochemical cell. ^[1][2] In short, it functions as a link connecting the anode and cathode half-cells within an electrochemical cell.^[3] It also maintains electrical neutrality within the internal circuit and stabilizes the junction potential between the solutions in the half-cells.^[4] Additionally, it serves to minimize cross-contamination between the two half cells. ^[1][5]

A salt bridge typically consists of tubes filled with an electrolyte solution. These tubes often have diaphragms such as glass frits at their ends to help contain the solution within the tubes and prevent excessive mixing with the surrounding environment.^[3] When setting up a salt bridge between different solvents of half-cells, it is crucial to ensure that the electrolyte used in the bridge is soluble in both solutions and does not interact with any species present in either solutions. ^[3]

There are several types of salt bridges: glass tube bridges (traditional KCl-type salt bridge and ionic liquid salt bridge), filter paper bridges, porous frit salt bridges, fumed-silica, and agar gel salt bridges.

The following sections will explore in greater detail the characteristics and applications of glass tube bridges, filter paper bridges, fumed silica salt bridges, and charcoal salt bridges.