Recent studies using neutron scattering and atomic force microscopy show that humic acid particles of colloidal size have a fractal structure with a high water content. Electromotive force studies using glass and redox electrodes show oscillations in humic acid solutions indicating a non- equilibrium nature of the system. Binding studies indicate that humic acids interact with copper and calcium ions via binding sites existing both within the particles and on their surfaces. These latter findings were shown by three series of studies involving kinetic data and two sets of steady-state data: pH titrations and data recorded via metal ion sensitive electrodes. The steady-state was controlled via a redox electrode.