Chloridometer

Chloridometers are used to measure Cl^– ions in plant tissues. This instrument titrates the Cl^– with Ag⁺ released from a silver wire. It works as follows: Ag⁺ is released at a constant rate as current is passed between a pair of silver generator electrodes. Cl^– in the sample solution precipitates with the generated Ag⁺ as AgCl. After all the Cl^– in the sample has precipitated there is a steady increase in Ag⁺ in solution. This results in an increasing current through a pair of silver indicator electrodes. When an increase in an indicator current is detected, a relay is activated, and a timer is automatically stopped (the timer runs concurrently with Ag⁺ generation – amperometric indication). Since the rate of generation of Ag⁺ is constant, the amount of Cl^– precipitated from the sample is proportional to the elapsed time. Therefore, solutions with higher quantities of Cl^– take a longer time to reach the end-point, and Cl^– is quantified by making a standard curve to relate time to known concentrations of Cl^– in standard solutions.