Sodium chloride clearly interfered with the mercury sorption of poly(S-r-limonene)-an important new finding. For a 100 mL sample of 5 ppm Hg 2+ containing 6.85 mM NaCl, 500 mg of the poly(S-r-limonene)-coated silica gel only removed 86% of the mercury after 5 minutes. For a 100 mL sample of 5 ppm Hg 2+ containing 599 mM NaCl, 500 mg of the poly(S-r-limonene)coated silica gel only removed 30% of the mercury after 5 minutes. In contrast, with no exogenous NaCl added in an otherwise identical experiment, 99% of the mercury was removed.