Chloridometer

A chloridometer is a measuring instrument used to determine the concentration of chloride ions (Cl^–) in a solution. It uses a process known as coulometric titration or amperostatic coulometry, the accepted electrochemistry reference method to determine the concentration of chloride in biological fluids, including blood serum, blood plasma, urine, sweat, and cerebrospinal fluid. The coulometry process generates silver ions, which react with the chloride to form silver chloride (AgCl).

The first chloridometer was designed by a team led by Ernest Cotlove in 1958.

Other methods to determine chloride concentration include photometric titration and isotope dilution mass spectrometry.

An amperostat delivers a constant current of about 6—8 mA to the generator electrodes for the titration of the solution, and a digital timer is started. A second pair of silver electrodes are used as a detector to measure the conductance of the solution. The same constant current is known to titrate a given number of moles ${\displaystyle (n_{Cl^{-}})_{s}}$ of a chloride standard solution in time ${\displaystyle t_{s}}$. Titration of the assay solution will result in the generation of insoluble silver chloride until the chloride ions are consumed, after which time an increase in silver ions will be detected at the detector electrodes. This time, ${\displaystyle t_{u}}$, is the titration time of the solution being measured. The concentration of chloride ions in this solution is then calculated as:

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