定電流分極電位差滴定法による金属アルミニウム中の微量塩素の定量

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Chlorine in aluminum metal was titrated argentometrically without separation of aluminum ion. The sample was dissolved with a sodium hydroxide solution. After filtration of the residue, the solution was acidified by citric and nitric acid solutions. Then the equal volume of ethanol was added to the sample solution, and the solution was titrated with a 0.01 Nsilver nitrate standard solution. Well defined titration curves could be obtained by the potentiometry at a constant current ( 1 μA) with a couple of pretreated silver electrodes pair. The potential difference of the electrodes should be measured just 1 min after the addition of the standard solution. The following pretreatments of the electrodes were recommended : the electrodes were chlorinated anodically in 0.1 Nhydrochloric acid for 2 min (current density : about 0.6 mA/cm2), then washed thoroughly with water until the potential difference between the electrodes decreased to less than 10 mV (passing no polarizing current and on stirring). This treatment was necessary before each titration. The washing procedure of the surface of the sample was essentially important. Reproducible results could be obtained when the samples were washed with petroleum benzine. Coefficients of variation of the results were less than 11 % when the samples contained 1545 ppm of chlorine.
社団法人日本分析化学会の論文