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n. ~ 1. A substance that reacts with an alkali to form a salt. - 2. A substance with a pH between 1.0 and 7.0.

- acid, acidic, adj. ~ 3. The condition of having a high acid content.


Acid in materials generally results in a decreased life expectancy and brittleness.

(Roberts and Etherington 1982) Acids, and particularly the inorganic acids (because of their corrosiveness and low volatility), are harmful to paper and bookbinding materials. Their presence weakens the holding power of the individual links of the cellulose chains of paper, causing brittleness; results in corrosive effects in some inks; and weakens the fibers of leather. The source of acids in archival materials may be intrinsic or extrinsic. They may be present in the materials used in the manufacture of paper, adhesives, leather, etc., and may be left in intentionally, e.g., alum-rosin sizing; they may be introduced during manufacture and not sufficiently removed, e. g., acids used in clearing and/or dyeing leather; or they may gain access during storage, e.g., sulfuric acid in paper or leather, resulting from the atmospheric pollutant, sulfur dioxide (SO2).