This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
When the leaves of a book are accidentally stained with ink it can be removed quite readily by the following process: After removing as much of the ink as possible with a camel's-hair brush dipped in water, soak the stained parts in a solution of oxalate of potash, or better still, oxalic acid. This will remove all the ink. Treat again with water, as before, so that when it dries out no salt Will appear on the paper. This process does not affect printer's ink. - Contributed By S. G. Thompson, Owensboro, Ky.