Solubility of the Aqueous Reciprocal Quaternary System Li+, Na+//CO32–, SO42––H2O at 273.15 K

Abstract

An isothermal evaporation method was employed to study the solubilities of the aqueous quaternary system Li+, Na+//CO32–, SO42––H2O at 273.15 K, and the corresponding densities of the equilibrated solution were determined by the specific gravity bottle method. According to the experimental data, the metastable phase diagram, the water content diagram, and the density versus composition diagram were constructed. Results indicate that the quaternary system is of a complex type due to the two double salts Na3Li(SO4)2·6H2O and 2Na2SO4·Na2CO3 formed. There are four invariant points, six crystallization fields corresponding to four single salts (Li2CO3, Li2SO4·H2O, Na2SO4·10H2O, and Na2CO3·10H2O) and two double salts (Na3Li(SO4)2·6H2O and 2Na2SO4·Na2CO3) in this metastable phase diagram. The comparison was made between the metastable phase diagrams at 273.15 K and at 288.15 K and also between the metastable phase diagram at 273.15 K and stable phase diagrams at (298.15, 323.15, and 373.15) K. Results show that double salt 2Na2SO4·Na2CO3 is formed at T = (273.15, 323.15, and 373.15) K, while it is not formed at T = (288.15 and 298.15) K.