ピロガロールによる鉄の吸光度定量

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There are many organic reagents for colorimetric analysis of iron. In case of the determination of Cb by the coloration with pyrogallol, it is disturbed by the presence as the iron forms a purple complex salt, and this iron-pyrogallol complex salt is applied for the spectrophotometric analysis. The sample is fused with potassium pyrosulfate, the solution is treated with sodium sulfite solution for adjusting of the pH, but the solution is neutralized with dilute NH<SUB>4</SUB>OH when the sample was decomposed with the acid, sodium sulfite is added, then the color is developed with pyrogallol. In case of the presence of elements which form precipitate in a slightly alkaline reaction, good result is obtained by the addition of ammonium oxalate. The maximum absorption of iron-pyrogallol complex salt is found at 500 mμ on pH 7.8. However, using of wave length at 550 mμ is preferable in order to minimize the effect of disturbing elements and observe a definite absorption on various pH. A definite absorption is observed with the use of wave length at 550 mμ and pH 7.07.8 and the deviation is greater by use of wave length at 500 or 570 mμ.The maximum absorption is found at 550 mμ with pH below about 7. 2. The amount of 5 % pyrogallol necessary for formation of the complex salt is 3 cc. for 0. 2 mg. iron. It is necessary to run blank test when nickel and chromium are present as disturbing elements. The presence of 0. 1 mg. Cb, 0.2 mg. Ti or 0. 1 mg. Mo gives no great error in the determination at 550 mμ but the presence of these element above the limit cause disturbances. The estimation line obtained by use of wave length at 550 mμ followed Beers Law excellently and 10-mm. layer was suitable when the concentration of iron was 0. 11. 0 mg. /100 cc.

ピロガロールによる鉄の吸光度定量

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