On the precipitation of salts/complexes of trivalent cations with humic acid

It was found that some trivalent cations form precipitates with humic acid at pH 4.2. The precipitates contain less metal cations than suggested by the neutralization-charge model for soluble complexes based on the available anionic sites. It is suggested that cations, which can form inner-sphere complexes, may precipitate before they are completely neutralized, while those that do not form complexes precipitate only after complete neutralization. This revised version was published online in July 2006 with corrections to the Cover Date.