Book-repair specialists use the term foxing to refer to various kinds of mildew on book pages. The word name comes from ferrous oxide, the chemical compound found in paper that attracts the mildew. Foxing almost always occurs in damp conditions because paper is hygroscopic, which means that moisture in the atmosphere is drawn to it. The moisture allows the mildew to thrive. Unless the foxing is repaired, the affected pages can eventually disintegrate.
Fill the paint tray with tap water.
Dissolve enough Chloramine-T powder in the tap water to turn it green.
Fold the book's boards straight up and submerge the affected pages in the Chloramine-T and tap water solution for five minutes. Be careful not to damage the book's binding.
Remove the pages from the solution and air dry them.
After your pages have dried, repeat the process for any other pages that need to be repaired.
Prevent foxing by keeping antique books in polythene or other protective materials.
Make sure that your problem is foxing rather than oxidation. Foxing turns pages green, and oxidation typically turns them a coppery, reddish colour.