This method can be used for the determination of chlorine incompressed hydrogen gas or for the determination of hydrogenchloride in other gas systems, such as refinery recycle gases. Themethod as applied to compressed hydrogen does not distinguishbetween chlorine and hydrogen chloride and the results areexpressed in terms of mol ppm of chlorine. For recycle gasanalysis, the chlorine is in the form of hydrogen chloride and isexpressed as such. Two to six cubic feet of sample is sufficient todetect a chlorine or hydrogen chloride content equal to or greaterthan 1 mol ppm. Chlorine content in the range of 0.1 to 1.0 mol ppmcan be determined by the use of a proportionately largersample.