短絡電流滴定法によるチオシアン酸アンモニウム中の微量チオ尿素の迅速定量(ノート)

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A method for the rapid determination of micro amounts of thiourea in ammonium thiocyanate has been investigated by means of the short-circuit amperometric argentometric titration. A rotating (1200 rpm) platinum wire electrode and a mercury-mercury(II) iodide electrode (-0.23 V vs. SCE) were used. By this technique 5 × 10-5 F thiourea in the presence of an 800-fold amount of thiocyanate could be titrated directly with the relative error of +0.1% and the coefficient of variation (c. v.) of 0.3% at 5060°C in a solution containing 0.5 F ammonia, 0.025 F ammonium carbonate and 0.02% gelatin.By applying the standard addition method 2.5 × 10-6 F thiourea in the presence of a 12000-fold amount of ammonium thiocyanate could be determined with the relative error of +2.7% and c. v. of 3.5%. This method was applied to the analysis of thiourea in some commercial ammonium thiocyanate(industrial and reagent grade).
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