Abstract
A method of EDTA masking-coprecipitation of minute amount of antimony was presented, and was applied with good result to the determination of antimony in iron and steel. The method of determination was square wave polarography using 3 N hydrochloric acid as supporting electrolyte. The recommended procedure is as follows.
Dissolve 0.20.5 g of sample in the least amount of sulfuric acid. Add 70 mg of Cr(III) as a coprecipitant and EDTA equivalent to sample, and make alkaline with ammonia. Separate the precipitate by centrifuge with 3000 rpm for 5 min. in a 50 ml centrifuge tube. Wash the precipitate once with water, and dissolve it in 3 N HCl to make up to 25 ml. Take the polarogram (from -0.07 V to -0.25 V vs. Hg pool) without deaeration. The working curve was prepared by carrying through the procedure on the solution containing equal amount of iron with the sample solution added with standard antimony solution. As much as 150 μg of Bi, 100 μg of Cu, 1 mg of tin and lead, and 100 μg of tantalum were permitted.
