The adsorption of naphthalene by a Bosket loam soil was studied at 6.5, 15, 25, and 37C. Because the solubility and vapor pressure of naphthalene are precisely known over this temperature range, a complete thermodynamic description of the differences between standard vapor, crystal, solution, and soil-adsorbed states is possible. The results indicate that enthalpies and entropies of the solution and surface standard states are quite similar (though very different from the vapor state) resulting in a near-zero standard enthalpy difference and a small standard entropy increase for adsorption from solution. Considering naphthalene as a model for herbicides and as a probe into the nature of the soil surface, the results emphasize the importance of the unique structured nature of water acting as a solvent, and the competition of water for adsorption sites.
