Chromotropic acid tests

I have been conducting chromotropic acid tests according to the
recommended procedure outlined by Jinping Zhang, David Thickett, and
Lorna Green in "Two Tests for the Detection of Volatile Organic
Acids and Formaldehyde" (JAIC 33(1994): 47-54), with the following
variation to the apparatus they describe: rather than use a modified
ground glass stopper with a suspended reaction dish, I have been
placing a .1 ml Supelco micro reaction vessel (cat no. 2-7034) in
the bottom of the 50 ml reaction flask and putting 10 drops of
chromotropic acid solution into it.  Other than that, everything is
as specified in Zhang, Thickett, and Green's paper.

In testing a range of materials, I'm finding that while the solution
does not turn purple within the specified 30 minute period, a purple
species will appear if I continue to run the test for a period of 2
to 28 hours.  Purple species do not appear in any blind controls run
concurrently with these tests.  Which brings me to my questions:

    Has anyone else had similar experiences when running
    chromotropic acid tests?

    Is the appearance of this purple species--even though it is
    occurring well beyond the specified test period--significant?

Will Jeffers
Collections Care Specialist
Department of Scientific Research
Museum of Fine Arts
465 Huntington Avenue
Boston, MA 02115
USA
617-369-3466
Fax: 617-369-3702


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                  Conservation DistList Instance 14:37
                 Distributed: Tuesday, January 9, 2001
                       Message Id: cdl-14-37-019
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