»Tetanus and Diphtheria Toxoids Adsorbed for Adult Use conforms to the regulations of the FDAconcerning biologics (see Biologics á1041ñ).It is a sterile suspension prepared by mixing suitable quantities of adsorbed diphtheria toxoid and adsorbed tetanus toxoid using the same precipitating or adsorbing agent for both toxoids.The antigenicity or potency and the proportions of the toxoids are such as to provide,in each dose prescribed in the labeling,an immunizing dose of Tetanus Toxoid Adsorbed as defined for that product,and one-tenth of the immunizing dose of Diphtheria Toxoid Adsorbed as defined for that product for children,such that in the specific guinea pig antigenicity test it meets the requirement of production of not less than 0.5unit of diphtheria antitoxin per mLand each immunizing dose has an antigen content of not more than 2Lf (flocculating units)value as measured with the U.S.Reference Diphtheria Antitoxin for Flocculation Test.Each component meets the other requirements for those products.It contains not more than 0.02percent of residual free formaldehyde.