Analysis of Acid Papers by Non-Aqueous Solvent Extraction- Spectrophotometry and Upside-down pH Glass Electrode

Non-aqueous solvent extraction of acid in papers is described; the process employs a liquid ion-exchanger in chloroform. The amounts of the acid in the so-called acid paper are determined by the normal method of aqueous extraction and by the organic solvent extraction and the values are compared. The results of investigation confirm that the acid content of the acid paper must be determined by the non-aqueous solvent extraction. It is pointed out that the level of the acidification of the "acid paper" can not be presented in terms of the value of pH, as is usually done, but instead should be presented in terms of the amount of substance (mol) of acid per gram of paper. Because the analysis of the "acid paper" must be carried out on a nondestructive basis, the upside-down glass electrode pH meter is recommended as a conventional tool for the nondestructive determination of the acidity of papers of precious books. Examples of the latter case are shown.