deacidification
A term generally considered to mean the removal of
acid from, or the reduction of the acidity in, a
material, such as paper. The usual process of
deacidification is to treat the paper with a mild
alkali which initially neutralizes any acid
present and is then converted into a compound that
remains in the fibers of the paper to act as a
buffer to neutralize any further acidity that may
develop (usually as a result of exposure of the
paper to atmospheric SULFUR DIOXIDE ).
High concentrations of strong alkalies are to be
avoided because if the pH of the paper is allowed
to rise to a very high level, i.e., 10.0 or above,
and to remain there for any length of time, there
is risk of oxidation of the cellulose under such
alkaline conditions. In the usual case, however,
even if the pH, immediately subsequent to
acidification, is as high as 10.0, reaction with
atmospheric carbon dioxide usually reduces it
below that point.
The weakness of most deacidification methods is
that slightly alkaline papers are immune to acid
attack only for as long as the free alkali
remains, and when this is neutralized the paper is
again vulnerable. In order to prevent this, the
amount of residual alkali remaining in the paper
following treatment should be equivalent to at
least 3% calcium carbonate by weight of the paper.
See also: ALKALINE
RESERVE ;DOUBLE
DECOMPOSITION ;NON-AQUEOUS
DEACIDIFICATION ;VAPOR-PHASE
DEACIDIFICATION .
(31 , 33 , 39 , 198 , 265 )
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