Solution adsorption techniques have been examined for their applicability in determining
the surface reactivity of graphite fiber surfaces. The graphite fibers examined were principally Thornel 50 and HMG 50 which derive from rayon as a precursor. Fiber surface conditions consisted of water sized as synthesized, oxidized in nitrogen-oxygen mixtures at 1200ยฐC and oxidized in hot nitric acid. Ionic solutions NaOH, LiOH, methylene blue chloride, metanil yellow, and chloroplatinic acid were adsorbed from water solution. Adsorption of the cationic dye, methylene blue chloride, and the anionic dye, metanil yellow, from a competitive solvent (water) provide a useful measure of the surface concentration of cationic and anionic adsorption sites for graphite fibers subjected to various surface treatment histories. The untreated water sized fibers are characterized by a predominance of anionic adsorption sites. Nitric acid oxidation treatment leads to a decline in the concentration of anionic adsorption sites, but results in a significant increase in the concentration of cationic adsorption sites. Surface carboxyl and hydroxyl appear to dominate in the adsorption characteristics of acid oxidized fibers but make a minor contribution to the adsorption properties of either untreated or air oxidized graphite fibers. There is good correspondence between the adsorption of the organic dye cation, methylene blue, and inorganic cations, such as sodium and lithium cations. Lithium adsorption is preferred to sodium because of the prevalence of contamination by sodium compounds. The population density of anionic adsorption sites on the untreated graphite fibers is compatible as to order of magnitude with the surface concentration of edge carbons estimated from published data on the crystallography of graphite fibers.