ABSTRACT
The dead-stop method is based on the phenomenon of polarization. A constant potential difference is applied to two identical electrodes immersed into the solution. If the solution contains a reversible redox couple, a current will flow through the cell, which can be measured by a microamperemeter. If the redox system present is irreversible and the sum of the overpotentials of the anodic and cathodic processes exceeds the external voltage applied to the electrodes, in principle no current can pass through the cell; in practice the current is very small. The Karl Fischer method can be used for the accurate and rapid determination of small amounts of water. The basis of the method is that sulfur dioxide reacts with iodine in the presence of water in a reaction leading to equilibrium.
