the methane molecule. This explains the drop in enthalpy, since hydrogen bonding is increased compared to pure water, and the drop in entropy, since a solvent excluded volume has come into existence along with an ordered network of water molecules. Hildebrand challenged this popular view in a series of papers in the late 1960s and 1970s and concluded that methane has a just a 40% lower diffusivity in water than in carbon tetrachloride. If water was enclatherated or in an iceberg-type structure, then he predicted that this diffusivity difference between water and carbon tetrachloride ought to be significantly larger. This conflict of ideas still exists in the literature with publications between 2000 and 2010 for the clathrate-type hydrophobic hydration still being submitted in computer simulations of various types. There are papers, however, which cite Hildebrand's earlier criticisms of this model and suggest that hydrophobicity arises from the small size of water increasing the free energy required to develop a suitable cavity for certain solutes to occupy. With George Scatchard, Hildebrand developed an equation for excess molar volumes in mixtures. References Further reading Hildebrand J. H., To tell or to hear some new thing, American Scientist, vol. 51, p. 2–11, 194 (1963) Hildebrand J. H., Is there a "hydrophobic effect"?, Proc. Natl. acad. Sci. USA, vol. 76, no. 1, p. 194 (1979) Hofinger S. and Zerbetto F., Simple models for hydrophobic hydration, Chem. Soc. Rev., vol. 34, p. 1012 (2005) Silverstein T. P., Hydrophobic solvation NOT via clathrate water cages, J. Chem. Educ. vol. 85, no. 7, p. 917 (2008) External links Oral History interview transcript with Joel Hildebrand 6 August 1962, American Institute of Physics, Niels Bohr Library and Archives National Academy of Sciences Biographical Memoir 1881 births 1983 deaths American centenarians Men centenarians 20th-century American chemists University of Pennsylvania alumni University of California, Berkeley College of Letters and Science faculty American shooting survivors Fellows of the American Physical Society Members of the American Philosophical Society