Photometric determination of aluminum in iron and steel with aluminon using ascorbic acid as a masking agent

Abstract

One half gram of iron or steel sample is decomposed by treating with the mixture of 15 ml sulfuric acid (1+9)and 10 ml hydrogen peroxide (15% v/v).
After being cooled, interfering elements are removed by electrolysis with mercury cathode. The acidity of the solution is adjusted to pH about 4 with ammonia water (1+1) and hydrochloric acid(5 M) using p-nitrophenol as an indicator, then the solution is diluted exactly to 100 ml with water. A 25 ml aliquot is transferred to a 100 ml measuring flask, and 1 ml of ascorbic.acid solution (1% w/v), 5.0 ml of aluminon-buffer composite solution (prepared by dissolving 500 g of ammonium acetate, 0.8 g of aluminon and 90 ml of acetic acid in 1 liter of water) and 2 ml of gum arabic solution (5%, w/v) are added.
Then the solution is heated on a water bath or on a hot plate, cooled, diluted to the mark with water, and mixed. The absorbance is measured at 532 mμ in a 20 mm cells. The proposed method has three advantages over the JIS method; the sensitivity is higher by about thirty percent, the procedure is simpler, and the color is more stable (stable for at least 24 hours).