PROPERTIES AND STRUCTURE OF SILICAS 521 (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) J. J. Fripiat, M. C. Gastucke and R. Brichard, Surface heterogeneity in silica gel from kinetics of isotopic exchange OH-OD,J. Phys. Chem., 66, 805 (1962). C. G. Armistead, A. H. Typer, F. H. Hambleton, S. A. Mitchell and J. A. Hockey, The surface hydroxylation ofsilica,J. Phys. Chem., 73, 3947 (1969). F. H. Van Cauwelaert, P. A. Jacobs and J. B. Uytterhoeven, Identification of the A-type hydroxyls on silica surfaces, J. Phys. Chem., 76, 1434 (1972). (a) S. K. Wason (toJ. M. Huber Corp.) U.S. Patent 3893840 (1975). (b) S. K. Wason (toJ. M. Huber Corp.) U.S. Patent 4040858 (1977). (c) S. K. Wason and R. K. Mays (toJ. M. Huber Corp.) U.S. Patent 4067746 (1978). (a) S. K. Wason (toJ. M. Huber Corp.) U.S. Patent 3988162 (1976). (b) S. K. Wason (toJ. M. Huber Corp.) U.S. Patent 4015966 (1977). Determination of Oil Absorption, Amer. Soc. Test. Mater. Stand., D, 281. S. Brunauer, P. H. Emmett and E. Teller, Adsorption of gases in multimolecular layers, J. Amer. Chem. Soc., 60, 309 (1938). Coulter Electronics, Inc., 590 West Twentieth Street, Hialeah, FL 33010. N.M. Winslow and J. J. Shapiro, An instrument for the measurement of pore size distribution by mercury penetration, A.S.T.M. Bulletin, February 1959, (Aminco Reprint No. 105). G. K. Stookey and J. C. Muhler, Laboratory studies concerning the enamel and dentin abrasion properties of common dentifrice polishing agents, J. of Dent. Res., 47, 524 (1968). P. C. Kitchin and H. B. G. Robinson, How abrasive need a dentifrice be?, J. of Dent. Res., 27, 501 (1948). N.J. Dudding, L. O. Dahl and J. C. Muhler, Patient reactions to brushing teeth with water, dentifrice, or salt and soda, J. Periodontol., 31,386 (1960). H. B. McCauley, M. J. Sheehey, D. B. Scott, P. H. Keyes, S. J. Fanale and P. P. Dale, Clinical efficacy of powder and paste dentifrices, J. Amer. Dent. Ass., 33,993 (1946). Council on Dental Therapeutics, Reports of Council and Bureaus: Abrasivity of current dentifrices, J. Amer. Dent. Ass., 81, 1177 (1970). P. C. Kitchin, The prevalence of toothroot exposure, and the relation of the extent of such exposure to the degrees of abrasion in different age classes, J. of Dent. Res., 20, 565 (1941). R. J. Grabenstetter, R. W. Broze, F. L. Jackson and A. W. Radike, The measurement of the abrasion of human teeth by dentifrice abrasives: a test utilizing radioactive teeth, J. of Dent. Res., 37, 1060 (1958).

Book Review CHARACTERIZATION OF POWDER SURFACES, Edited by G. D. Parfitt and K. S. W. Sing, Academic Press Inc., London, England, 1976, x + 464 pages. Price $30.25. The primary thrust of this ex- cellent book relates to those us- ing powders as pigments and filters in paints, inks, plastics, fibres and equivalent applications. Each of the nine chapters is writ- ten by specialists in the areas covered. The first three are funda- mental, surface characteriza- tions-first chemical and then physical, with the trilogy being completed with flow property evaluations. Each of these develops the fundamentals for ap- propriate evaluation of the cited property. This reviewer found the chapter on flow to be particu- larly of interest. The next three are directed to specific pigments--inorganic white, inorganic colored and or- ganic. Each is discussed systematically and, although pri- marily aimed at the paint and ink industry, these chapters can develop a better comprehension of some of the coated pigments now available for cosmetic use. The final three chapters cover the specific topics of carbon blacks, silicas and clays. The last two are of special interest, even to those tending to work solely with suspensions and lotions. Un- fortunately, the clay chapter is the shortest in the book, only 28 pages. Each chapter is well referenced and quite current for an edited volume. The index appears to be complete and reasonably de- tailed. For those actively working in powder technology this should be an excellent addition to their personal libraries. Others with more occasional needs would find this of value in a company or de- partmental library holding.w JOHN H. WooD--School of Pharmacy, Virginia Common- wealth University. 523