# 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 .

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