The analytical method of dichloromonofluoromethane (Freon-21) reported in our previous paper was modified for the determination of Freon dissolved in sea water and brine.
When the method described in previous paper was spplied to sea water or brine sample, the decreased recoveries which were found to be due to the precipitation of magnesium hydroxide were observed. The interference by magnesium could be partially settled by increasing the amount of sodium hydroxide which was used 1 ml of 5 N solution for the determination of Freon dissolved in fresh water. Satisfactory recoveries were gained by using 1.5 m
l of sodium hydroxide to sea water containing 5-25g/
l of chlorine and 2.0m
l of sodium hydroxide to brine containing 20-45g/
l of chlorine. In these cases, it was noted that the calibrations should be made to the known amounts of Freon dissolved in sea water (15g/
l of chlorine) and in brine (35g/
l of chlorine)(Fig.4). This modification, however, was not applicable to the brine of higher concentration and to those solutions containing c uprous or ferric ions more than 1mg/
l which caused the decline of recoveries as described in our previous paper.
It was also found that Freon could easily be expelled from aqueous solutions by aeration and absorbed quantitatively with ice-cooled pyridine by using the apparatus shown in Fig.5.
Nine m
l of pyridine were pipetted to each of the two absorption tubes kept in the ice-cooled bath. After 20 minute aeration of sample tube with a rate of 30m
l/min., 20m
l of 5N sodium hydroxide were added to the absorption tubes, and then the reaction was carried out as reported in our previous paper. As the result of our repeated experiments, 93% of Freon was found in the first absorption tube and the remaining 4% in the second tube.
Any inhibitory effects of concentrated chlorine, magnesium and other metals were not observed, and this method was confirmed to be applicable to a wide-ranged purpose.
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