Graphical methods for studies of aqueous aluminum hydroxide, fluoride, and sulfate complexes. Chemistry of aluminum in natural water

Published stability constants show that aluminum forms strong complexes with hydroxide, fluoride, and sulfate ions. Equilibrium calculations show that fluoride complexes probably will be the predominant form of aluminum solute species in natural water below neutral pH, when more than a few tenths of a part per million of fluoride, is present. Sulfate complexes of aluminum can be important below neutral pH if sulfate concentrations exceed 500 ppM. By means of graphs, the predominant complex species and proportion of uncomplexed aluminum activity to total aluminum concentration are shown as functions of the analytical concentration of aluminum and fluoride, or sulfate, for ionic strengths ranging from zero to that of sea water. In alkaline solutions the species Al(OH)/sub 4/-tends to predominate. The forms of aluminum complexes which can be expected to predominate, and extent of complexing in solutions containing both fluoride and sulfate, and the effects of pH on the complexing of aluminum by fluoride and sulfate also are shown by means of graphs.