n.a measure of the acidity or alkalinity of some substance, determined by the concentration of hydrogen ionsBarrow 1943, 151It is possible to measure the degree of this acidity by laboratory tests and to rate it according to a standardized scheme technically known as pH values. These are expressed as logarithms ranging from 1 to 7, a low pH representing a high acid content. Samples of badly deteriorated papers which I have tested have been found to be very acid, with a pH as low as 3.1, and similar findings have been reported by the National Bureau of Standards and the U. S. Department of Agriculture.Barrow 1948, 299–300A test for acidity on the inked and uninked areas of several old documents of the period seemed desirable. This test was limited to fourteen sheets that were considered of no historical value and were either purchased or given to the writer for this purpose. The pH of these papers was determined colorimetrically and the method of preparation of the sample was the same as that developed by Dr. Herbert F. Launer of the National Bureau of Standards.McCarthy 1969, 335At the end of each of the two deacidification processes described, a pH determination should be made to check the effectiveness of the treatment. This can be accomplished through two methods. A test paper with a known pH that is equal to the lowest pH of the papers to be treated can be inserted into the manuscripts before treatment by VPD.Fox 1985, 27Computer printout paper will also present a challenge because of its high acidic level. At Yale University, an informal sampling of tractor-feed computer paper showed that it had a pH level of around 5.4—over ten times more acidic than a neutral 7.0 level.Fox 1985, 37, fn. 3A 7.0 pH value is “neutral”; values lower than 7.0 are acidic, and those above 7.0 are alkaline. Because the pH values are calculated on a logarithmic scale, each decrease of 1.0 represents a tenfold change in acidity; thus, 6.0 is ten times more acidic than 7.0, and 5.0 is 100 times more acidic than the neutral 7.0.Ritzenthaler 2010, 54Acidity and alkalinity are measured on the pH scale. . . This is an arbitrary numerical scale ranging from 0 to 14, with 7.0 being the point of neutrality. All numbers above 7.0 represent increasing alkalinity, and all numbers below 7.0 indicate increasing acidity.
Notes
pH is measured on a scale from 0 to 14; values below 7.0 are acidic, and values above 7.0 are alkaline. A pH of 7.0 is neutral.
