Thermodynamics of the LiOH + H₂O System

Abstract

Literature data for the solubility of anhydrous lithium hydroxide and lithium hydroxide monohydrate in pure water have been compiled and critically evaluated. The selected data have been represented by empirical temperature−molality expressions from which the coordinates of the eutectic and of the peritectic have been calculated. The phase diagram of the LiOH + H2O system is presented. A model using Pitzer's ion interaction approach for the calculation of the thermodynamic properties of aqueous LiOH solutions is built by fitting literature values for the osmotic coefficient obtained from isopiestic and from freezing point depression measurements from the eutectic point (255 K) to 473 K. Heat capacities of aqueous LiOH solutions are then calculated using the first and second derivatives with respect to temperature of these expressions and are compared to direct measurements. The solubility products of LiOH(s) and of LiOH·H2O(s) are calculated from their solubilities in pure water. Standard entropies, enthalpies, and heat capacities of formation of solid lithium hydroxides retrieved from fits of their solubility products with respect to temperature are compared to literature values, which are mainly derived from calorimetric measurements.

Probing water dynamics with OH−

“…This conclusion is corroborated by the observation that several peculiarities of thermodynamic/structural quantities are observed for all three solute species. Namely the apparent heat capacity changes sign [37,38], the vapor pressure reaches a plateau [39][40][41], the specific conductance is maximum [42] and, in particular, clear changes of the H-bond connectivity are visible, as shown in Fig. 5.…”

Behavior of LiOH·H2O crystals obtained by evaporation and by drowning out

“…Monnin and Dubois [21] reported a fusion temperature for LiOH·H 2 O of 383 K, and thus the present polymorphic crystalline system can be classified as enantiotropic. Ternary systems The enthalpies of the two crystal solutions in ethanol + water ( ethanol/water ratio = 0.1) are determined as for binary systems, taking into account that in Eq.…”

A thermodynamic model of aqueous electrolyte solution behavior and solid-liquid equilibrium in the Li-H-Na-K-Cl-OH-H2O system to very high concentrations (40 molal) and from 0 to 250 C

“…The recent parameters provided by Monnin and Dubois (2005) allow describing the osmotic coefficients of LiOH aqueous solutions as a function of temperature up to the solubility of LiOH solid salts. However, new experimental measurements of osmotic coefficient were published at the same time by Nasirzadeh and others (2005), which could not be used by Monnin and Dubois (2005).…”