is a highly sensitive and precise electrochemical analytical technique that can measure microgram quantities of sulfur and chlorine in a solvent. A minute quantity of solvent is combusted in a quartz pyrolysis tube, and the combustion products—typically carbon dioxide (CO₂), water, sulfur dioxide (SO₂), and hydrogen chloride (HCl)—flow to a titration cell. In the test for sulfur, the SO₂ reacts with iodine in the cell, creating an electrical imbalance that is detected by sensor electrodes. The iodine is then restored to its original concentration by means of a current produced at generator electrodes by a microcoulometer. The amount of current and time required to restore the system to equilibrium is directly proportional to the amount of sulfur present in the solvent sample. In the test for chlorine, the HCl reacts in the titration cell with silver ions.