Nitrate negatives

In response to Frank Reynolds inquiry concerning the testing of
cellulose nitrate negatives, I believe this question has been
answered before on CoOL. One of the best tests is the
diphenylamine/sulphuric acid test. Many wet chemical tests involve
the use of toxic chemicals, but if they are used properly, there is
no danger whatsoever.

In a fume hood, add 20 mg of diphenylamine to 1.0 ml of concentrated
sulphuric acid, mix well with a glass stirring rod and apply 1 to 2
drops directly to the sample.  Let the solution stand for several
minutes. Cellulose nitrate produces an intense blue color.

Alternatively, if you have access to an analytical laboratory,
cellulose nitrate shows prominent bands on an infrared spectrum, at
6.1 and 11.9.

As a postscript, the trichloroethylene test is not always reliable
for nitrate film, as the film may have a gelatin coating.

Stephen Koob
Conservator
The Corning Museum of Glass
One Corning Glass Center
Corning, NY 14830
607 974 8228
Fax: 607 974 8470

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                  Conservation DistList Instance 13:23
                 Distributed: Tuesday, October 5, 1999
                       Message Id: cdl-13-23-004
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