Spectrophotometric Titration of Milligram Quantities of Barium

Abstract

Manns et al have published a titrimetric method for barium in which 500 mg of barium acetate were titrated with 0.1 M Versene solution (disodium dihydrogen ethylenediaminatetetraacedic acid). The concentration of dye used by these investigators was such that under tungsten illumination a color change from wine-red to almost colorless was observed at the end-point. The application of this procedure by others to smaller amounts of barium has indicated the use of more dilute titrant and additional dye in order to detect the end-point. Under these conditions the color-change is extremely difficult to detect since one titrates until the last trace of wine-red color disappears leaving a clear blue color. The elimination of this visual difficulty by utilizing a spectrophotometric detection of the end-point is described in the present paper. In addition, this technique permits the determination of much smaller quantities of barium than is possible with the visual method.