4 EXPERIMENTAL

1. Paper: A and B Smith Company newsprint and Andrews/Nelson/White-head American Etching 100% cotton rag paper were used in the experiments. The pH of each paper was determined before and after deacidification by cold extraction.
2. Reflectance Measurements: A Kollmorgen model D-1 “Color-Eye” reflectance spectrophotometer modified for small area viewing was used for all reflectance measurements. Individual samples were measured over a black glass background relative to BaSO4 at 500 nm with the spectral component excluded.
3. Tensile Strength Measurements: All paper samples were conditioned at 20�C and 50% R.H. for at least 72 hours prior to testing. The samples were cut to � inch in the cross direction and 3 inches in the machine direction, and measurments were made in the machine direction only.
4. Conditions for Accelerated Aging: The paper samples were sealed inside glass tubes measuring 120 mm by 17 mm. Ten samples were sealed in each tube in order to obtain an average of ten measurements of tensile strength and reflectance for each data point. A humidity of 100% was maintained in each tube by including a milliliter of water in the base of each tube, the paper samples being supported over the water by a glass pedestal.
5. Method of Deacidification: The rag and newsprint papers were soaked in a 0.02% aqueous solution of calcium hydroxide to neutralize acidity. Calcium carbonate was precipitated in the paper by a subsequent immersion in a 0.02% aqueous solution of sodium carbonate. Excess sodium and calcium compounds were washed out of the paper with de-ionized water leaving only calcium carbonate in the paper.
6. Data Analysis: Error estimates shown in the data tables are 95% confidence intervals. For values of i and j, these confidence intervals were obtained from linear regressions of rate-versus-oxygen-concentration data.7 For values of kd/ku, between 9 and 20 individual determinations were made and averaged.