Solubilities and properties (density

conductivity and pH value) of solutions in the quaternary system Li+

K+//CO2-3

B4O2-7-H2O at 288 K were experimentally studied with the isothermal equilibrium method. The phase diagram of the system consisted of two invariant points E and F

five univariant curves

and four crystallization fields that belonged to K2CO3·3/2H2O，Li2B4O7·3H2O，K2B4O7·4H2O and Li2CO3. The composition of the solution corresponding to E was w（CO2-3）=2.27 %，w（B4O2-7）=6.05 %，w（K+ ）=4.30%，w(Li+)=0.30 % and the equilibrium solids were Li2B4O7· 3H2O+K 2B4O7·4H2O+Li2CO3;The composition of the solution for F was w(CO2-3)=22.45%，w(B4O2-7)=1.88%，w(K+ )=29.96%，w(Li+ )=0.03% and the equilibrium solids were K2CO3·3/2H2O+K 2B4O7·4H2O+Li2CO3. K2CO3 possesses strong salting-out effect on K2B4O7

Li2CO3 and Li2B4O7.