Simultaneous Determination of Chlorine, Bromine and lodine in Sedimentary Rocks by Neutron Activation
1971 Volume 20 Issue 4 Pages 165-170
Details
1971 Volume 20 Issue 4 Pages 165-170
The analytical procedure established in the present work is as follows; The crushed rock samples of 1 g were sealed in polyethylene vials and irradiated in the pneumatic tube of the JRR-2 reactor at a flux of 8×1013 n/cm2·sec for 20 min. Samples and monitors were fused with sodium hydroxide in nickel crucibles, in the presence of carriers. The fusion cake was dissolved in water and acidified to about 2M H2SO4. Fe3+ was added to oxidize I- to I2, and I2 was distilled into sodium sulfite solution. KMnO4 was then added to oxidize Br- and Cl- to Br2 and Cl2, and these elements were separated from mother solution by distillation. Chemical yields were measured colorimetrically for iodine and potentiometrieally for chlorine and bromine. Yields consistently ranged from 80%-90% and time required for chemical separation was about 50 min.
The distillates were counted on a γ-ray spectrometer, consisting of 3in.×3in. NaI (Tl) crystal and a 400-channel pulse height analyser. The following γ-rays were measured: 128I, 0.445 MeV; 38Cl, 1.60 and 2.17 MeV; 82Br, 0.55 and 0.78 MeV. The activity measurement for 82Br was done after one day cooling.
Interference from (n, p), (n, α), (n, 2n) and fission reactions was negligible.
The present method was applied to sedimentary rock samples of Niigata prefecture and highly reproducible results were obtained. The sensitivity is 10-8g for iodine, 10-7g for chlorine and bromine.
