Coulometry

Key facts and history

American chemist G. G. Grower first applied surface coulometry in 1917 to check the quality of tinned copper wire.^[2] Coulometric methods were widely used in the mid-twentieth century but later declined as voltammetric and non-electrochemical methods took over.^[3] One coulometric method still widely used today is the Karl Fischer method.^[3] Michael Faraday established the laws of electrolysis and created the earliest charge-measuring device by employing water electrolysis.^[4]

In constant-current coulometric titration, the amount of analyte is found by measuring how long the current flows through the sample.^[3] A benefit of coulometric titration is that constant-current sources for titrant generation are simple to construct and offer greater sensitivity and control compared to adding titrant mechanically from a burette.^[3] Titrants that are chemically unstable or difficult to manage, for instance bromine or Karl Fischer reagents, can be employed readily in this technique.^[3]

What the research sources say

Clinical chemistry uses a Cotlove chloridometer to measure chloride levels in blood samples, as described in a 1990 Butterworths book.^[5][6] An encyclopedia entry from 2005 by Peter C. Hauser explains that coulometric microtitrators generate protons or hydroxide ions at the working electrode through water electrolysis.^[3][7] According to the same source, microtitrators are not absolute methods because they need calibration due to variable diffusion.^[3][7]