Abstract
A method of quantitative determination of several percent of copper and 0.11% of iron and zinc in aluminum alloy by means of S. W. polarography has been investigated. Copper and zinc in 0.1g sample is dissolved in hydrochloric acid-nitric acid mixture, evaporated to dryness and the residue is dissolved in 5 ml hydrochloric acid. This is made up to 50 ml with water and a portion is used for taking polarogram. Copper and zinc are determined by the waves at -0.25V and 1.05V respectively (mercury pool is used in each case). For determination of iron, another portion of the sample solution is evaporated to dryness and the residue is dissolved in hydrochloric acid (1 : 1). This in a separatory funnel is extracted with MIBK. The solvent layer is treated with water to back-extract the iron. The extract is concentrated to about 2 ml for driving off the solvent. This is made up to 25 ml with water, neutralized with 0.5N sodium hydroxide, using methyl red-methylene blue indicator, acidified with 1 ml hydrochloric acid (1 : 10), 7.5g sodium citrate is added, the solution is made up to 50 ml with water and a part of it is used for taking polarogram at -0.3V (against mercury pool) for the determination of iron from the wave height. This method is less affected by the presence of coexisting ions and the determination can be carried out within 1 hour.
