A simple and reliable method has been developed for the state analysis of small amount of aluminum in steel. The procedure is as follows: 1. Separation of aluminum compound
(a) The steel sample covered with close-texture filter peper as a diaphragm, connected as an anode, is dissolved into 130
ml of 1% NaCl-5% EDTA electrolyte (pH 6-7) with current density of 50mA/cm
2 for 2hr. Remove the anode, and residue is collected into filter paper using methanol. Add 50
ml of 4% iodine methanol solution to the residue and warm at 60× for 30 min.
(b) Filter and wash with methanol. Add 10
ml of HNO
3 and 10
ml of HClO
4 to the filterate and evaporate to dense white fumes. Cool, dilute to 100
ml, and determine aluminum in cementite in accordance with section 2.
(c) Transfer a fifth parts of the electrolyte to a beaker. Add 15
ml of HNO
3 and 10
ml of HClO
4 and evaporate to dense white fumes. Cool, dilute to 100
ml, and determine aluminum as solid solution in accordance with section 2.
(d) Transfer the paper and residue (paragraph (b)) to a beaker, add 30
ml of HNO
3 (1: 1) and 5
ml of H
2O
2 and boil for 10min.
(e) Filter and wash with water. Add 10
ml of HClO
4 to the filterate and evaporate to dense white fumes. Cool, dilute to 100
ml, and determine aluminum as AlN in accordance with section 2.
(f) Transfer the paper and residue (paragraph (e)) to a platinum crucible, heat until the carbon is gone. Add 1g of Na
2CO
3 and ignite for 20min at 900 to 1000×C. Cool, dissolve in 30
ml of water containing 5m/ of HCl. Add 10m/ of HClO
4 and evaporate to dense white fumes. Cool, dilute to 20
ml. Filter through into a 100
ml volumetric flask, and wash with water until to the mark, and determine aluminum as oxide in accordance with section 2.
2. Photometric determination of aluminum.
Transfer 5
ml of each of the solutions of section 1 (b), (c), (e) and (f) to 50
ml volumetric flasks. To each, add 10
ml of water and 5
ml of 0.1% Eriochrome Cyanine R solution and allow to stand for 2 to 3 min. Add 3
ml of 2% mercaptoacetic acid and 10
ml of buffer solution and dilute to 50
ml. Warm at 80×C for 1min. Cool and measure the absorbance against blank solution at 590
mu.
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