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Mezhueva M. A., Danilina V. V., Kurskii V. F., Cherkasov D. G. Extractive Crystallization of Salt and Phase Equilibria in the Ternary System Sodium Nitrate – Water – Dipropylamine . Izvestiya of Saratov University. New series. Series: Chemistry. Biology. Ecology, 2019, vol. 19, iss. 4, pp. 401-414. DOI:


Extractive Crystallization of Salt and Phase Equilibria in the Ternary System Sodium Nitrate – Water – Dipropylamine


Phase equilibria in the ternary system sodium nitrate – water – dipropylamine where the constituent binary liquid system is characterized by a trend to form a lower critical solution temperature (LCST) were studied using the visual-polythermal method in the range −10.0–90.0° C. It was found that the introduction of sodium nitrate into the water – dipropylamine system led to a significant decrease in the mutual solubility of the components. Based on the polythermal data obtained isothermal phase diagrams of the studied ternary system were plotted at −10.0, −1.5, −1.9, 0.0, 0.9, 1.5, 5.0, 25.0, 50.0, and 90.0° C. The compositions of the liquid phases of the monotectic state were graphically determined and the distribution coefficients of dipropylamine between these phases were calculated at 10, 15, 20, 25, 30, 35, 40, 50, 60 and 90° C. Sodium nitrate was found to be an effective salting–out agent of dipropylamine in the range of 10–90° C. It was established that the effect of salting-out of dipropylamine from aqueous solutions with sodium nitrate amplifies with increasing temperature and takes on the maximum value (961.0) at 90° C. The effectiveness of the use of dipropylamine in extractive crystallization of sodium nitrate from its unsaturated aqueous solutions containing 43.0, 44.0, 45.0 and 46.0 wt.% of the salt in the range of 10–60° C was estimated. The dependences of the yield of solid sodium nitrate on the amount of dipropylamine introduced were found. It was established that the maximum yield of sodium nitrate (81%) was observed for the section containing 46 wt.% of the salt, at 90 wt. % of the introduced amine and 35.0° C. 

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