This volume presents and evaluates reported solubility data for the title compounds, complementing an earlier volume in the IUPAC Solubility Data Series dealing with alkali metal halides. Orthophosphates have been known and used for many years; principal applications include their use in fertilizers, as corrosion inhibitors and in piezoelectric components. Most published data relate to sodium and potassium orthophosphates; introductory chapters on these two systems are followed by chapters dealing with individual phosphates with various metal/phosphorus ratios, together with coverage of ternary and multicomponent systems. In compiling the data, all relevant articles published up to 1984 have been consulted. Critical evaluation of the data has made possible the definition of recommended solubility values.