Testing exhibition materials

    **** Moderator's comments: Doug was tempted to withdraw this
    posting as being "picky", but I learned useful stuff from it and
    browbeat him into reconsidering, so blame me, not him.

Pretty much everyone that I run into in conservation talks about the
Beilstein test as being a test for chlorides and it's not quite that
specific. However, if we found things with organic bromides or
iodides they probably wouldn't be good either. The test isn't
sensitive to fluorides so things like Teflon and Kynar would not be
ruled out as bad (which is good.)(...so I'm probably splitting hairs
with this posting anyway.... :^))

Let me quote from my old college organic lab text [D. Pasto and C.
Johnson. Laboratory Text for Organic Chemistry: a source book of
chemical and physical techniques, Englewood Cliffs, NJ:
Prentice-Hall, Inc. 1979.]:

   "Beilstein test for halogens: The presence of chlorine, bromine,
    or iodine in organic compounds can be detected by the Beilstein
    test. The test depends on the production of a volatile copper
    halide when an organic halide is strongly heated with copper
    oxide. The test is extremely sensitive, and a positive test
    should always be confirmed by other methods.....

    A blue-green flame produced by volatile copper halides
    constitutes a positive test for chlorine, bromine, or iodine
    (copper fluoride is not volatile).

    Very volatile compounds may evaporate before proper
    decomposition occurs, causing the test to fail. Certain
    compounds such as quinoline, urea, and pyridine derivatives give
    misleading blue-green flames owing to the formation of volatile
    copper cyanide."

I remember being warned about the possibility of sweat contamination
possibly affecting the test, but it was based on conjecture and not
necessarily on fact. Many of my demonstration samples I've handled
without gloves and have not found any false positive results.

-Doug

                                  ***
                  Conservation DistList Instance 10:95
                 Distributed: Wednesday, April 30, 1997
                       Message Id: cdl-10-95-001
                                  ***