[Studies in Surface Science and Catalysis] Proceedings of the International Conference on Colloid and Surface Science, 25th Anniversary of the Division of Colloid and Surface Chemistry, The Chemical Society of Japan Volume 132 || Adsorption of Nonionic Surfactants, Triton X and Triton N, on Hydroxyapatite after Surface Modification with Sodium Dodecyl Sulfate in an Aqueous Phase*)*)This study was supportedby Grant-in-Aid for Scientific Research (C)-(2) #11672143(1999-2000) of The Ministry of Education, Science, Sports and Culture, Japan.