An automated photometric end point detection of the Ba(C104)2titration of sulfate using thorin as an indicator is described. The technique has a detection limit of 1–2 μg of sulfate. Results of studies of end point, pH effect, and ionic strength or cation effect are given. Although ion exchange is usually unnecessary, it is described and studied. Comparisons are made between the photometric end point detection, visual end point detection, and microgravimetric sulfate determination.