Polarographic Determination of Arsenic in Iron and Steel

Abstract

In the quantitative determination of arsenic by polarography, hydrochloric, nitric and sulfuric acids or combined use of these acids and citric or tartaric acid have been used as supporting electrolytes. Studies on polarograms obtained by use of these electrolytes indicated that good polarogram was obtained by use of nitric acid with sodium chloride or ammonium chloride. This was applied on the determination of a trace of arsenic present as an impurity in iron and steel and good result was obtained. For separation of arsenic from iron, stannous chloride was used for deposition of metallic arsenic, this was taken up in nitric acid and sodium chloride was added as a supporting electrolyte. By addition of the chloride, half-wave potential shifted to (+) side, and 2 mol solution gave a two-step wave at -0.4 and -0.65V and lowered the slope of a portion of dispersed electric current to decrease the errors from graphing. As to the relation between arsenous acid and wave height, a satisfactory result was obtained by using 1N HNO3 and 2 mols NaCl solution when the concentration is within the range of 2×10-35 mol.