Measurement of hydrogen-ion concentration, or pH, may be made colorimetrically, by means of the proper use of suitable neutralization indicators, or, more accurately, by potentiometric methods employing any of various electrodes, which exhibit the proper specificity for hydrogen ions.
Hydrogen-ion concentration is important in archival work because it has been adequately demonstrated that the presence of acid(s) in ink, leather, paper, etc., has or can have, a deleterious effect on such materials, the extent of the effect depending not so much on the volume of acid present, as on the type of acid and its concentration, i.e., a large volume of a relatively weak organic acid, such as formic acid, is less harmful than a smaller amount of a powerful, inorganic acid, such as sulfuric acid. As a decrease of pH means a logarithmic increase in acid concentration, levels of concentration below pH 5.0, or under certain circumstances, even 6.0, become important. Conversely, although not as serious a problem, a high concentration of hydroxyl ions, corresponding to a pH of 10.0 or above, can lead to serious oxydization of cellulosic materials.
The increase in hydrogen-ion concentration as pH declines is given be
pH moles/ liter 7.0 0.0000001 6.0 .000001 5.0 .00001 4.0 .0001 3.0 .001 2.0 .01 1.0 .1 0.0 1.0
See also:ACID ; ALKALI . (17 , 195 , 235 )
Timestamp: Saturday, 19-Nov-2011 13:18:42 PST
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