conductometry
/ kon-duk-TOM-uh-tree /
Pure water barely carries electricity, but stir in some salt and it conducts much better — the dissolved ions act like tiny charge carriers ferrying current across the solution. Conductometry simply measures how well a solution conducts electricity, and from that reads how many ions are swimming in it. The saltier (more ionic) the water, the higher the conductance.
Formally, conductometry measures the electrical conductance of a solution between two electrodes, which depends on the total concentration of ions and on how mobile each kind of ion is. It is a non-specific bulk measurement: it does not say which ions are present, only how much ionic content there is overall. To avoid driving reactions at the electrodes, it is done with a small alternating current rather than a steady one.
It matters because it is simple, rugged, and cheap, and is the standard quick check of water purity and total dissolved ions — from deionized lab water to drinking water and aquariums. It also pinpoints the end point of certain titrations by tracking the V-shaped change in conductance. The caveat is its lack of selectivity: it lumps all ions together, so it answers 'how ionic' but never 'which ion'.
A water-purification system uses a conductivity meter as its alarm: as long as the conductance stays very low the water is pure, but if conductance creeps up, ions are leaking in and the cartridge needs replacing — no need to know which ions, only that there are too many.
Conductance rises with total ion content, but tells you nothing about identity.
Conductometry measures bulk solution conductance and is non-specific, so it differs sharply from potentiometry's ion-selective electrodes: use conductometry to gauge 'how ionic', and an ion-selective electrode when you must know which ion and how much.