Determination of Total Cl in Organic Liquids

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Written and developed by Prof. Tor Bjørnstad (IFE/UiO) 

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Natural Cl has the two stable isotopes 35Cl(35%) and 37Cl(65%). Thermal neutrons induce the two reactions 35Cl(n,γ)36Cl (T1/2 = ) and 37Cl(n,γ)38Cl (T1/2 = 37.3 min). Only the second reaction is useful here. The actual gamma energies for 38Cl are 1642.7 keV and 2167.6 keV.


The detailed procedure is:

  1. Team 1 and Team 2 go to the detector room where a teacher will demonstrate the counting equipment. These teams will then be well prepared for the counting procedure after the following practical procedure.
  2. Team 3 and Team 4 go to the preparation laboratory and carry out the following procedure:
  3. Prepare a Cl-standard: Dry KCl in a heating cabinet at 110 oC for 24 h. Cool in a deccicator. Weigh exactly in ca. 0.21 g KCl and dissolve to 100.00 ml in a measuring flask with distilled water. This standard is approximately 1000 ppm.
  4. For the present analysis we will operate with a working standard of about 100 ppm. Take an aliquote of 10 ml from the standard and dilute to 100 ml with distilled water.
  5. Prepare 4 plastic irradiation ampoules by heat-sealing adequate lengths of a plastic (polyethylene) tubing in one end.
  6. To one ampoule transfer a fraction of 1.00 mL from the working standard. Heat-seal and label.
  7. To the three others transfer 3 parallels of 1.00 mL of the organic unknown sample. Heat-seal and label.
  8. Pack the ampoules into a rabbit container.
  9. Arrange irradiation with the reactor control room.
  10.  Irradiate the sample 5 min and transfer back to the lab.
  11.  After irradiation wash the ampoules on the outside with the washing solution sequence acetone-water-acid mixture-water-acetone. Every ampoule is washed for 5-10 s in each solution.
  12.  Samples are transferred to the counting laboratory and a demonstration is given of the counting equipment for teams 3 and 4.
  13. Position the first sample in front of the detector inside the lead shield and start counting. Start the stop-clock. Counting time 5-10 min.
  14. Count the two other samples and the standard in the end.
  15. Integrate the appropriate peaks and note the results.