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.

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