The partitioning of a suite of chlorohydrocarbons including superhydrophobic polychlorinated biphenyls between humic acid and water is investigated. Measured equilibrium partition coefficients do not increase regularly with molecular descriptors such as 1‐octanol/water partition coefficient (Kow ), supercooled liquid aqueous solubility, molecular weight and molar volume. Rather, for compounds with log Kow of 5.5 or more, the humic acid/water partition coefficient reaches a limiting value of approximately 105 ml g‐1. Reasons for this behaviour are discussed and similarities drawn with results from triolein/water and organism/water systems. Supercooled liquid solubility of test compounds in humic acid is also calculated.