Precise Coulometric Titrations of Halides

The determination of halides is of interest in many chemical investigations. For example, in a recent determination of the atomic weight of chlorine[l] * it was necessary to determine the chloride content of dilute solutions with high precision. For such applications, coulometric titration is particularly advantageous because it involves a minimum of manipulation. A further advantage is that the titrant is generated in situ in amount that is measured in terms of physical quantities. Although a number of publications have been concerned with the coulometric determination of halides [2, 3,4, 5] there seem to have been no attempts made to establish the conditions for high-precision titrations, i.e., better than 0.1 percent. Accordingly, the work reported in this paper was undertaken as part of a continuing program at the National Bureau of Standards to develop coulometric titrations of high precision and accuracy[6].