measured adsorption of 100 cc. of N*/g. for the monolayer. This total surface of the graphite dust is comparable with those of the best commercial activated carbons, and in addition 1.2% of this total surface showed a powerful chemical activity.3. Nitrogen adsorption isotherms on graphite powder (raw material), finished graphite rods (brushes), and powder formed by pulverizing the rods in a high-speed impact grinder indicated surface areas of 7.7,1.3 and 4.6 sq. m./g., respectively, compared with 435 sq. m./g. for the wear-dust.4. It is shown that for a laminar model of graphite fragments in which the ratio of edge area to face area is small, the surface area per unit weight is independent of size and shape and depends only on the thickness of the fragments. A thickness of 20.4 Á. is indicated for the carbon wear-dust. A minimum average diameter of 3500 Á. is indicated for the face dimension on the assumption that hydrogen reacts quantitatively with edge atoms.5. It is suggested that the chemically active portion of the dust represents unsaturated carbon valences at points of cleavage at right angles to the main cleavage plane. The wear dust appears to differ from previous carbon samples studied in that these strong valence bonds have been freshly opened, mechanically, and occur in large numbers; whereas the corresponding bonds in other carbons are ordinarily saturated by chemisorbed gas and are not opened by ordinary outgassing procedures.

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