Dilution enthalpies of LiBO2 and LiB5O8 aqueous solutions at 298.15 K and the application of ion-interaction model

The dilution enthalpies of LiBO 2 (aq) from 0.0398 to 0.7684 mol·kg −1 and LiB 5 O 8 (aq) from 0.0521 to 0.8067 mol·kg −1 at 298.15 K and 101.325 kPa were investigated using the microcalorimeter BT 2.15. The apparent molar enthalpies on two lithium borates were obtained, and the diagrams of their apparent molar enthalpy against molality for LiBO 2 (aq) and LiB 5 O 8 (aq) were also plotted. Considering the constructers of BO 2 - and B 5 O 8 - in aqueous solution are existed as in [B(OH) 4 ]- and [B 5 O 6 (OH) 4 ]-, the Pitzer single-salt parameters ( β M X ( 0 ) L ${\beta }_{\mathrm{M}\mathrm{X}}^{\left(0\right)\mathrm{L}}$ , β M X ( 1 ) L ${\beta }_{\mathrm{M}\mathrm{X}}^{\left(1\right)\mathrm{L}}$ , β M X ( 2 ) L ${\beta }_{\mathrm{M}\mathrm{X}}^{\left(2\right)\mathrm{L}}$ , C M X L $C_{\mathrm{M}\mathrm{X}}^{\mathrm{L}}$ ) for LiB(OH) 4 and LiB 5 O 6 (OH) 4 were obtained for the first time. A comparison between the calculated apparent molar enthalpies for LiBO 2 (aq) and LiB 5 O 8 (aq) based on Pitzer model and those determined experimentally agree well, which indicate that the Pitzer single parameters of LiB(OH) 4 and LiB 5 O 6 (OH) 4 obtained are reliable.