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.