This paper deals with the structure and chemistry of Nafion-H, the acidic form of Nafion, which is the trade name for a perfluorinated polymer manufactured by E. I. du Pont de Nemours & Co., Inc. Nafion-H and its salts are available from Dupont in both membrane and powder forms. Nafion composites with Teflon mesh (polytetrafluoroethylene) added to give increased mechanical strength are also available. In addition, sulfonated fluorocarbons modified with other chemically active polymers have been made by Dupont and by competing companies such as Ashai Chemical Industry Co., Ashai Glass Co., Tokuyama Soda Co., and Toya Soda Co.