Abstract
Orthophosphates of aluminum have been the subject of numerous studies since the middle of the nineteenth century. They have acquired importance in such diverse fields as the earth sciences, chemical engineering, and medicine. The chemical problems associated with this Al2O3[BOND]P2O5[BOND]H2O system mainly arise from the marked tendency to form polymeric aluminum orthophosphate complexes in solution; equilibrium is reached only with difficulty, and crystallization of single phases is the exception rather than the rule. However, the crystal structures of several aluminum orthophosphates (including minerals) have been elucidated, and it is now possible to give a systematic description of this class of compounds and the conditions necessary for their formation.
