Determination of sulfuric acid in metallurgical process streams by discontinuous flow analysis

Discontinuous flow analysis was applied to the determination of sulfuric acid in metallurgical process samples by photometric titration using a bromophenol blue indicator. Over-estimation of the level of acid due to the precipitation of metal hydroxides and oxides was prevented by titrating with sodium acetate. At a throughput of 110 samples h−1, the method exhibited excellent repeatability and reproducibility, with relative standard deviations of less than 1% throughout. Determinations on samples taken from copper, manganese and zinc refining operations compared well with results obtained using the existing industry procedure of manual titration with hydroxide to a pH 3.9 endpoint. Of twelve metals investigated, only arsenic(V) and iron(III) interfered to a significant extent. High levels of cadmium, chromium(III), copper(II) and lead(II) resulted in small positive errors, whereas calcium, cobalt(II), magnesium, manganese(II), nickel(II) and zinc did not interfere.