Assessment of a new method for the differential pulse polarographic determination of silicon in steel

A procedure is described by which silicon in steel may be determined by differential pulse polarography after removal of iron. Silicomolybdic acid is formed within 20 min by reaction of the silicon with molybdate in the presence of methyl ethyl ketone: subsequent addition of citrate buffer prevents interference from phosphate and excess of molybdate. At the levels present in high-purity iron ( approximately 0.002%) the precision for silicon is better than that usually quoted for the molybdenum blue method. The steel is dissolved by standard procedures but iron must be removed before the silicon is determined. The lower limit imposed by the polarography is about 10(-5)% silicon, but the practical lower limit is probably set by the difficulty of removing the last traces of iron.