To measure the concentration of chloride ions in a water sample using potentiometry, you will need to use an ion-selective electrode ISE that is sensitive to chloride ions. A silver/silver chloride Ag/AgCl electrode is commonly used for this purpose. Here is a step-by-step procedure to measure chloride ion concentration using potentiometry:1. Gather the necessary equipment: You will need a chloride ion-selective electrode Ag/AgCl electrode , a reference electrode e.g., a saturated calomel electrode or a silver/silver chloride reference electrode , a pH/mV meter or an ion meter, a magnetic stirrer, and standard chloride solutions for calibration.2. Calibration: Prepare a series of standard chloride solutions with known concentrations e.g., 1, 10, 100, and 1000 mg/L . Measure the potential mV of each standard solution using the Ag/AgCl electrode and the reference electrode. Record the potential values and create a calibration curve by plotting the potential mV on the y-axis and the logarithm of the chloride concentration log [Cl-] on the x-axis. The calibration curve will be used to determine the concentration of chloride ions in the unknown water sample.3. Prepare the water sample: Collect the water sample and filter it if necessary to remove any suspended particles. The sample should be at room temperature for accurate measurements.4. Measure the potential of the water sample: Place the water sample in a beaker and immerse the Ag/AgCl electrode and the reference electrode in the sample. Stir the sample gently using a magnetic stirrer. Allow the potential to stabilize and then record the potential mV of the water sample.5. Determine the chloride concentration: Use the recorded potential of the water sample and the calibration curve to determine the concentration of chloride ions in the water sample. Locate the potential value on the y-axis of the calibration curve, find the corresponding x-axis value log [Cl-] , and then calculate the chloride concentration by taking the antilogarithm of the x-axis value.6. Report the results: Report the concentration of chloride ions in the water sample in the appropriate units e.g., mg/L or ppm .By following these steps, you can accurately measure the concentration of chloride ions in a water sample using potentiometry with a chloride ion-selective electrode.