Hello all,
  I have been having problems with some of our new nickel tubes being used
in a miniaturized conventional fluorination line for small (3mg) Qz
samples. We have contamination problems, apparently from the machining and
welding and I would like to know if users have followed a particular
clean-up procedure. One that was suggested to me is 'nickel passivization'
-- apparently a series of nitric acid treatments. This supposedly removes
surface gunk and renders surfaces even more inert than machined nickel. Any
observations about whether this is a good idea or not?
  It seemed to me that the BrF5 would do a pretty good cleanup job after a
standard solvent series, but I think the welding was done with a good deal
of machine oil on the tube bore at the time. We now get high (>100%) yields
in about 1/3 of our vessels and the d18-O values are too negative.

  Many thanks for any suggestions.

- David


               David Dettman          [log in to unmask]
               Dept. of Geosciences   ph. (520) 621-4618
               Univ. of Arizona       FAX (520) 621-2672
               Gould-Simpson Bldg.
               Tucson, AZ 85721