Phase diagram of the liquid ternary system hexane-dimethylformamide-solvate of thorium(IV) nitrate with tri-n-butyl phosphate at various temperatures

The phase diagram of the ternary liquid system hexane-dimethylformamide-[Th(NO 3 ) 4 (TBP) 2 ] was studied at various temperatures. The system consists of two pairs of partially miscible liquids: hexane-dimethylformamide and [Th(NO 3 ) 4 (TBP) 2 ]-hexane. The area of separation into two liquid phases in the system [Th(NO 3 ) 4 (TBP) 2 ]-hexane is narrowed with heating; the upper critical temperature T cr is 337.85±0.25 K. The influence of temperature on the area of separation into layers of the system hexane-dimethylformamide is insignificant. The ternary liquid system is characterized by two homogeneous and one two-phase area of liquid solutions at T < 338 K. One of the phases contains variable amounts of [Th(NO 3 ) 4 (TBP) 2 ] and hexane, and also small amounts of dimethylformamide; the other phase contains variable amounts of dimethylformamide and [Th(NO 3 ) 4 (TBP) 2 ] and also small amounts of hexane. With increasing temperature, the two-phase area is narrowed and deformed and the homogeneous areas are extended. At T > 338 K, the system transforms into a ternary liquid system with one pair of partially miscible liquids (hexane-dimethylformamide).