Lignin, << LIHG nihn, >> is a complex substance formed by certain plant cells. It is the substance in wood that makes wood stiff. Lignin is found in the cell walls of woody tissue and is similar to plant cellulose. It is made up of chains of repeating carbohydrate molecules called polymers. Lignin, like cellulose, permits water and gases to pass through it. In the manufacture of paper, lignin is removed from wood by treating the wood fibers with sodium sulfite, sodium hydroxide, or a mixture of sodium hydroxide and sodium sulfide.
Although lignin is primarily a waste product in paper manufacturing, some lignin is now used as fuel in paper-pulp mills. It is also used in making plastics, fertilizer, artificial vanilla, cosmetics, building board, rubber, fire extinguishers, and other items.
