Isopiestic measurements were performed in binary and ternary systems of the type Fe2(SO4)3–H2SO4–H2O, FeCl3–H2O, and FeCl3–MCln–H2O (M = Na, K, Mg, or Ca). Numeric data for water isoactivity lines are presented and osmotic coefficients are calculated. The obtained data were recalculated using Pitzer’s equations. Pertinent parameters are given.

Performance assessment studies in underground disposal of radioactive or toxic waste need to consider all reactive interactions between waste and its surroundings. Thermodynamic equilibrium and reaction path calculations represent an important tool for this purpose. The reliability of the results depends first of all on the quality of the thermodynamic database used for the calculations. Several quality criteria of thermodynamic databases are discussed in connection with the characteristics of current database projects [Nuclear Energy Agency Thermochemical Database (NEA-TDB), Yucca Mountain database, Dortmund Databank (DDB), Common Thermodynamic Database (CTD), FreeGS, and Thermodynamic Reference Database (THEREDA)] including the situation for molten salts. The future role of the IUPAC standard for thermophysical and thermochemical data storage is emphasized.

Isopiestic measurements were performed in aqueous FeCl2-solutions and in ternary systems of the type FeCl2–MCln–H2O (M = Na, K, Mg, Ca). Numeric data for water-isoactivity lines are presented and pertinent osmotic coefficients are calculated. The obtained data were recalculated using Pitzer’s equations. Pertinent parameters are given.

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