The phase equilibria and phase diagram of the quaternary system (LiCl-LiBO2-Li2SO4-H2O) at 298.15 K

which was not reported in the literature

were studied with the isothermal dissolution equilibrium method. Solubilities and physicochemical properties including refractive index (nD)

density (ρ)

pH and conductivity (κ) in the quaternary system were determined experimentally. According to the experimental data

the dry-salt diagram

water-phase diagram and the diagram of physicochemical properties versus lithium chloride concentration in the quaternary system were plotted

respectively. The experimental results showed that there were two invariant points named as invariant co-saturated point (Li2SO4·H2O + LiCl·H2O + LiBO2·2H2O) and incommensurate co-saturated point (Li2SO4·H2O + LiBO2·2H2O + LiBO2·8H2O)

five univariant curves and four crystalline regions corresponding to Li2SO4·H2O

LiCl·H2O

LiBO2·8H2O and LiBO2·2H2O in the quaternary system at 298.15 K. Neither double salt nor solid solution was formed

and the phase diagram of this system at 298.15 K belonged to hydrate-type Ⅱ. The two kinds of hydrate lithium-containing minerals (LiBO2·2H2O and LiBO2·8H2O) were found for the first time. The salting-out effect of LiCl in the solution was obvious for the composition of Li2SO4. The diagram of physicochemical properties including nD

ρ

pH and κ versus composition shows that the physicochemical properties were changed regularly with increasing lithium chloride concentration in the solution and the singular values were achieved at the invariant points of the quaternary system at 298.15 K.