Grapical Methods for Study of Dissolved Aluminum Complexes (*)

The distribution of ionic species in dilute solutions at 25 °C and 1 atmosphere pressure can be computed by mathematical procedures based on the law of mass action and related thermodynamic equations. The computations require some knowledge of concentrations of ions and the forms of complexes or ion-pairs, and their stability constants, or their free energies of formation. Sufficient information is now available to permit accurate computations of the amount and form of dissolved species of many constituents of natural water. Graphs can be prepared which give relatively simple and direct insights into the details of natural water chemistry. Examples in this paper show the solubility of aluminum in relation to pH, the dominant dissolved forms of aluminum in solutions containing various concentrations of fluoride, and the proportions of uncomplexed to total dissolved aluminum in such solutions. Graphs also are given showing the interrelated complexing effects of fluoride and sulfate and fluoride and hydroxide.