The solubility of β-FeF 3 ‚3H 2 O has been measured in solutions with different concentrations of nitric acid (0 to 7 m) and hydrofluoric acid (1 to 6 m) at the temperatures of (30, 40, and 50) °C. The total iron concentration at equilibrium was measured with inductively coupled plasma (ICP) spectroscopy. The solubility was evaluated in terms of the stepwise complexation of iron by fluoride ions at different ionic strength and temperature. The solubility of β-FeF 3 ‚3H 2 O increases with decreasing concentration of HF and HNO 3 and increasing temperature.