A Potentiometric Method for the Determination of Chloride in Milk

Abstract

When chlorides in milk are titrated directly using chromate as indicator, the results are too high because of interference by protein. Potentiometric titration curves obtained by substituting a pure silver electrode for the glass electrode of a pH meter showed that this interference could be eliminated by titrating in nitric acid solution at pH 2, dilute 10 ml of milk with 20 ml of dilute nitric acid (6 ml/1). The inflection (end) point occurred at 250 millivolt with respect to a saturated calomel electrode (Beckman, asbestos fiber type). The procedure is recommended as rapid and accurate if the silver electrode is kept clean. A 10% weight/volume solution of KA1(SO4)2.12H2O can be substituted for the nitric acid with little loss in accuracy.