Fluorometric determination of aluminum in iron and steel with 2, 4-dihydroxybenzaldehyde-semicarbazone

Abstract

A method for the determination of aluminum in iron and steel was studied, using 2, 4-dihydroxybenzaldehyde-semicarbazone (DHBS) as a fluorometric reagent. One gram of the sample was dissolved by heating with 20 ml of sulfuric acid (1+9) and several drops of hydrogen peroxide (3 w/v%). The solution obtained was filtered through filter paper (No. 5C), and the residue was washed with warm sulfuric acid (2+100). The filtrate and washings were used for the following procedure. The residue was fused with 2 g of potassium pyrosulfate in a platinum crucible, and the melt was dissolved in the above filtrate and washings. After the solution was diluted to 100 ml with water, interfering elements were removed by electrolysis with mercury cathode. The solution was made up to 250 ml with water, from which a (0.11.0) ml portion was transferred into a 25 ml measuring flask, and diluted to 10 ml with water. Two milliliters of 0.1% DHBS solution in DMF and 2.0 ml of 20 w/v% ammonium acetate solution were added. The pH of the solution was adjusted to 5.4±0.1 with 1 N ammonia water, and diluted to the mark with water. The fluorescence intensity was measured with primary (UV-D1) and secondary filter (420 nm interference filter). No appreciable interference was caused by other impurities likely to be present in iron and steel. The accuracy of the procedure was checked by J.S.S. samples. The proposed method was applicable to the determination of aluminum above 0.001% in iron and steel.