Excess specific volume of water + tert-butyl alcohol solvent mixtures: Experimental data, modeling and derived excess partial specific thermodynamic quantities

The aim of this work is to develop a model for the dependence of the excess specific volume of the water + tert-butyl alcohol system on both composition and temperature under the temperature and pressure conditions relevant to the manufacturing and processing of poorly water-soluble drug formulations intended to be freeze-dried. For this purpose, experimental excess volumes of binary solvent mixtures were obtained from density measurements performed with a vibrating-tube density meter and carried out at atmospheric pressure for thirty-nine compositions covering the whole composition range and at five temperatures over the range from 293.15 to 313.15 K. For every temperature investigated, experimental excess volume data were fitted by a Redlich-Kister-based equation. By considering the temperature dependence of the regression coefficient estimates thus determined, the complete model equation was obtained and further validated by testing its correlative and predictive capabilities against data from this work and those from literature, respectively. Then, it was used to derive expressions for the excess partial thermodynamic quantities and their variations with respect to composition and temperature were discussed in terms of molecular interactions and structural arrangements in solution.