Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
The pH is the negative logarithm (base ten) of the hydrogen ion concentration in a solution. An increase of one pH unit implies a ten-fold increase in hydrogen ion concentration. At a neutral pH of 7 there are equal numbers of hydrogen ions and hydroxyl ions. The value of pH has a profound influence in papermaking because it affects the ionic character of fibers and many additives. Fibers tend to become increasingly anionic as the pH is increased in the range 3 to 8. Papermakers' alum is strongly cationic under acidic papermaking conditions (3.5 < pH < 5.5), but it quickly loses its cationic charge after addition to alkaline furnish (7 < pH < 9). The acidity of a furnish equals the amount of strong base such as NaOH needed to raise the pH to 8.3.
Request from the webmaster: Our goals include brevity and accuracy. Hopefully we have succeeded with the first goal without sacrificing the second. Please let us know right away if you find an error or omition. Also, please indicate points that need a clearer description.
RETURN TO INDEX PAGE OF ENCYCLOPEDIA
This page is maintained by Martin hubbe, Associate Professor of Wood and Paper Science, NC State University, email@example.com .