Microfilm deterioration

I ran into a situation I hadn't previously encountered yesterday, and
I'm interested to learn if anyone else has seen anything similar.

A collection of county records was filmed at some indeterminate date,
perhaps into the mid-60s.  Records of the filming project are lacking.
The film is 16mm, and seems to be diazo negative.  The image color is
blue, perhaps not as dark a blue as other diazo that I've seen, but
distinct.

Two different processes are underway.  Images near the beginning of the
roll have faded, changing color to pinkish purple and losing density.
Further on in the roll, the film base is changing color, from an almost
neutral transparency to a distinct brown.  Also, there seems to be the
faintest odor of vinegar when the reel is almost completely unspooled.

Thinking about it, I realized that most diazos must be on acetate bases.
(At my home shop, we film only silver, and, since 1986, polyester base.
I'm pretty unfamiliar with diazo.)

Fortunately, this film is not a critical preservation copy.  The source
documents are ledger volumes, not the ideal size for 16mm reproduction.
A 35mm silver film was produced later, probably on better advice.

Even so, does anyone know if this is one of the usual deteriorations for
the medium, or is it possible that I've run into an unusual silver
process?

Michael McCormick
WRHS

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                  Conservation DistList Instance 7:81
                  Distributed: Thursday, May 12, 1994
                        Message Id: cdl-7-81-007
                                  ***