N-ベンゾイル-N-フエニルヒドロキシルアミンによる食塩中の鉄の光度定量

概要

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The photometric method was investigated to determine iron (III) in common salt on the basis of the extraction with N-benzoyl-N-phenylamine (BPA) as a reagent in chloroform. Iron (III)-BPA complex was easily extracted at pH over 1.8 and the extracted complex indicated its maximum absorption at about 435mμ, and its coloration was stable at least for 2 hours. The light absorbancy was measured with a 420 mμ filter, and its coloration was almost constant in the pH range, 1.8 to 3.2. The caliblation curve followed the Beer's law in the range from 0.01 to 0.1 mg. per 10 ml. in chloroform. The presence of a large amount of sodium did not interfere with this extracting procedure. The established procedure was as follows: A 2.5-0.5g. portion, containing 0.01-0.08mg. Fe (III), of sample salt is weighed and dissolved in water, and 0.5 ml. of hydrogenperoxide solution (3 %) is added. After boiling, the solution is transferred into 100 ml. of separating funnel. After cooling, 3 ml. of ammonium acetate buffer solution (10%) of pH 2.2 is added and the obtained solution is diluted to 25ml. with water. Then, the solution is extracted with 10 ml. aliquot of chloro-form solution of BPA (0.2%). This extracting method is suitable for the determination of a small amount of iron in common salt, and the time required is about 30 minutes.
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