A comparative analysis of the results of our polythermal study of the ternary systems sodium (potassium, cesium) nitrate – water – triethylamine has been carried out to estimate the efficiency of the use of triethylamine in the extractive crystallization of alkali metal nitrates from water–salt solutions containing 43.0, 44.0, 45.0, 46.0, and 47.0 wt. % sodium nitrate in the range of 10.0–25.0°C, 20.0, 21.0, and 22.0 wt.% potassium nitrate and 18.0, 19.0, 20.0 and 21.0 wt. % cesium nitrate in the range of 20.0–25.0°C. The dependences of the yield of these salts on the amount of triethylamine added and temperature have been found. It has been established that the maximum yield of sodium nitrate (79.4%) is observed for the aqueous solution with 47 wt.% salt upon the introduction of 90 wt.% triethylamine at 25.0° C. The maximum yield in the systems potassium (cesium) nitrate – water – triethylamine was 68.9% (22 wt. % potassium nitrate solution) and 66.2% (21 wt. % cesium nitrate solution) at 20.0° C and 90 wt. % amine content.