Solubility diagram was investigated by the method of saturation in ampules at 25 ± 0.02 °C for 4 hours. The solubility diagram of the PrCl₃-C₆₀(OH)₂₄-H₂O ternary system at 25 °C occurs as simple eutonics, consisting of two branches, corresponding to the crystallization of crystalhydrates: PrCl₃ · 7H₂O and C₆₀(OH)₂₄ · 18H₂O. The diagram contains one non-variant point each - eutonics, which corresponds to saturation with pair of crystal-hydrates simultaneously. The diagram also contains very short branch of PrCl₃ · 7H₂O crystallization, and long branch of C₆₀(OH)₂₄ · 18H₂O, where the effect of fullerenol salt-out is distinctly observed.