アスコルビン酸をいんぺい剤とするアルミノン吸光光度法による鉄鋼中のアルミニウム定量法

概要

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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).
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