The Experimental Study on Absorbing Solution and Collecting Conditions in method for Determination of Low Concentration of Chlorine in Air by means of Absorptiometry

Abstract

As absorbing reagents serving as color developing reagent, N, N'-diethyl-p-phenylenediamine (DPD), 3, 3'-dimethylnaphthidine (DMN) and 2, 2'-adino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were examined. The most suitable pH and composition in each solution is as follows: DPD: PH 6.3, 0.2 mg/ml, DMN: 3, 6μg/ml, ABTS: 2.5, 0.1 mg/ml. The collecting vessel used in DPD and DMN method was not a sinteredglass bubbler but a midget impinger. In ABTS method, sample air must be drawn with a sintered glass bubbler (No.1, pore size: 0.1-0.12 mm). Maximum drawing rate to obtain collection efficiency near 100% with 10 nal of the solution (depth: 22 mm) and observed chlorine recoveries from standard gas flow were as follows: DPD: 1.5 liter/min, 96%; DMN: 0.8, 97; ABTS: 1.5, 100. ABTS method had large colorstability and little interference of SO₂, DMN method had low blank value and little interference of NO₂ and O₃. These two methods were better than usual o-tolidine method. The Cl₂ concentration which may be determined with sample size of 1 liter and coefficient of variance in the determination were as follows: DMN: 0.22-2 ppm, 3.2%; ABTS: 0.13-3, 2.8.