Metastable Equilibria for the Quaternary System Li2B4O7+Na2B4O7+K2B4O 7K2B4O7+H2O at 15 °C

Metastable equilibrium solubilities and such physico-chemical properties as densities, conductivity, pH, refractive index and viscosity of the solution for the quaternary system Li2B4O7+Na2B4O7+K2B4O7+H2O at 15 degrees C were determined experimentally. According to the experimental data, the metastable equilibrium phase diagram was plotted. In the metastable phase diagram, there are one invariant point, three univariant curves, and three fields of crystallization: Li2B2O4 center dot 16H(2)O, Na2B4O7 center dot 10H(2)O, and K2B4O7 center dot 4H(2)O. Potassium borate (K2B4O7 center dot 4H(2)O) has the smallest crystallization field and sodium borate (borax) has the biggest one. Also, the relationship diagram between the properties and the ion concentration of solution was constructed. It can be seen from the relationship diagram that the metastable equilibrium solution density values, viscosity values and refractive index values are increased apparently with the rise of lithium borate concentration, reaching the maximum values at invariant point F. Electrical conductivity values and pH values, however, fall down with the rise of ion concentration on the whole.