Reactions between mercury vapor and chlorine gas at occupational exposure levels

Abstract

The aim of this study was to investigate, whether reactions between elemental mercury vapor and chlorine gas should be considered, from a hygienic point of view, at concentration levels today relevant in a chloralkali plant. The homogeneous gas phase reaction between the two components was studied by monitoring the mercury vapor concentration in air mixtures, containing 0.01 ppm of mercury vapor and 1 ppm of chlorine gas, enclosed in a 200-litre gas bag made of Tedlar®, a fluorocarbon polymer. The reaction rate, at least at room temperature, was found to be negligible. The slight decrease in the mercury vapor bag concentration still recorded (2% an hour), was suggested to originate from heterogeneous oxidation reactions occurring on the walls of the bag. Furthermore, air mixtures containing mercury vapor and chlorine gas were brought together with various aqueous solutions. Electrode potential measurements of the solutions and mass transfer studies with respect to mercury were carried out. It was concluded that elemental mercury vapor is not oxidized by chlorine gas, at heterogeneous contact with “chlorine consuming” surfaces. Other kinds of surfaces, however, might give a substantial support to such oxidation reactions. For example, minus errors have here been noticed at measuring mercury vapor concentrations in the presence of chlorine gas by the use of an UV-detector, because of surface reactions taking place in the gas cell.