Determination of nitrate in pickling baths with a nitrate-selective electrode and a standard addition procedure

A reverse addition method for the determination of nitrate in pickling baths is described. Calibration solutions of nitric acid were added to the standard solution so that the slope and intercept of the electrode response function could be determined. The standard deviation of the method was better than 1 %. Nitrate in pickling baths containing hydrofluoric and nitric acids was measured and compared to measured hydrogen ion concentrations as a function of running time for the bath. The effects of iron(III) and hydrofluoric acid on the results were studied.