| The mean activity coeffcients of LiCl for LiCI-Li,B,O,-H,O system have beendetermined in the ionic strength range from 0.01 to 2.50 mo1. kg-' at 298. l5K by the method ofEMF using a pair of lithium ion-se1ective e1ectrode and Ag/AgCl electrode. Dissociatedequilibrium constant (K.), Thermodynamic constant (K), Stoichiometric associated equilibriumconstant (K.,'), and Pitzer ion interaction parameters were evaluated from present measurementsusing multiple regression and iterative method. T11e experimental activity coeffcients werecompared with those calculated by Pitzer equations from this work and references, presentingreasonable agreement. The activity coeffcients of LiCl in the medium of aq. Li,B,O, werecompared with those in aq. Li,SO#. The resu1ts show that the activity coeffcients of LiClincrease with increasing of Li,B,O, in the medium of aq. Li,B#O, and decrease withincreasing of Li,SO, in the medium of aq. Li,SO, in the ionic strength rang from 0.0l to 0.50mol. kg-'.We developed an isopiestic apparatus .A lid-lowering mechanism was installed to cover thesample cups within the isopiestic container. The reliability of the isopiestic messurements wasexamined fOr MgB#O, aqueous solutions at low concentrations. The isopiestic equilibriummolalities were measured, the water activities and osmotic coeffcients of aqueous MgB#O,have been determined from unsaturated to supersaturated at 298. l5K by using this improvedisopiestic apparatus, the results show that the water activities and osmotic coeffcients ofaqueous MgB.O, decrease with increasing of the ionic strength, the water activities of MgB#O,aqueous solutions are lower than those of NaCl. CaCl, at the same concentration. It indicatedthat MgB#O, in concentrated aqueous solutions tend to hydrate and to form polyborates. |
