Hydrogen peroxide and EDTA

In Instance 13:51, Chris Cheffins asks what is the right
concentration of EDTA to use in hydrogen peroxide bleach.

I'm not a paper conservator, but speaking as a chemist, 0.1M sounds
far too much.  The purpose of the EDTA is to stabilise the peroxide,
by chelating any transition metals (such as copper or iron) which
catalyse its breakdown. These metals will be present in very small
quantities, so not much EDTA would be needed to mop them up.  For
this purpose I would have thought that 0.001M or even less would be
sufficient.

The other thing to bear in mind is that at the higher concentration,
EDTA residues may remain in the paper, unless it is washed very
thoroughly.

Barry Knight
English Heritage
London


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                  Conservation DistList Instance 13:52
                  Distributed: Friday, April 21, 2000
                       Message Id: cdl-13-52-009
                                  ***