Lower limits of the potentiometric microtitration of chloride with silver ions

The lower levels of the potentiometric titration of chloride with silver ions were investigated. The titrant was 0.001 N acetonic silver perchlorate. The titration media were acetone and acetic anhydride:acetone (4:1). A silver sulfide ion-selective indicator electrode and a double-junction reference electrode were use to monitor emf's. This titration is limited only by the trace amounts of chloride in the reagents used. Satisfactory results and well-defined titration curves were obtained down to 7 μg of chloride per 50 ml of solution (0.2 μmol; 4 × 10^?6N).A small polarization current can be used to enhance the potentiometric breaks of this titration. In an 80% methanolic medium with 0.001 N aqueous silver nitrate and a polarization current of ?0.4 μA, the lower practical limit of this titration was near 22.3 μg of chloride (1.26 × 10^?5N).