Viton is a trade name for fluorocarbon elastomers (FKMs) manufactured by DuPont Performance Elastomers. There are several grades of Viton that are acceptable for 0-98% sulfuric acid and 85% phosphoric acid at 80 degrees C. These include Viton B, Viton GF-S, and Viton ETP-S. Other manufacturers of FKM elastomers include 3M (Dyneon), Daikin (Dai-El), Parker, and Solvay-Solexis (Technoflon). You should consult the FKM manufacturers for specific recommendations for your application.