Coulometric trace determination of chloride

1-2000 nmole of chloride was determined by coulometric titration with silver ions. The error was 0.1-5 %, depending on sample size. Chloride in water could be determined down to 0.01 ppm. The titrations were made in 75% acetic acid, 25% water. The displacement of the electrode potential on dilution of the solvent with water was determined. Two alternative procedures to compensate the end-point displacement are described. The titration times were 2-4 min for pretitration of the solvent and 2-4 min for titration of the sample. In some cases another 4 min were required for equilibrium to be reached. Various solvent compositions were used in order to find the optimum conditions.