In an equilibrium state with or without polarisation the potential of a working electrode is linked to the amount of active species in the conductive solution. The difference of potential between the working electrode and a reference electrode (fixed potential) allows the monitoring of the concentration evolution during the addition of a reagent.
Multiple reactions can be used in potentiometry, redox, precipitation, acid-base, ion pairing, complex formation… Direct addition can be used for fast chemical reaction, the potential indicates the end of the reaction induced by a stoechiometric addition of reagent.
Back titrations are used for slower reactions, after an excess addition, the reagent is back titrated by another reagent on a faster reaction.
