Vapor-liquid distribution and Krichevskii parameters of hydroxides Si(IV), B, Ge(IV), As(III) and Sb(III) in water

Abstract

The vapor–liquid partitioning of Si(OH)4, B(OH)3, Ge(OH)4, As(OH)3 and Sb(OH)3 in water at temperatures between 567.7 and 633.2 K was studied by sampling the coexisting vapor and liquid phases. For Ge(OH)4 and Sb(OH)3 the measurements in pure water have been made for the first time. Distribution constants for all hydroxides of metalloids, KD, are smaller than unity, i.e., these compounds strongly partition into the liquid phase. Correspondingly, the values of the Krichevskii parameter, AKr, the property that governs the thermodynamic properties of a solute close to the critical point of a solvent, for all these species are negative and equal (in MPa) to −178.6 ± 3.6 for Si(OH)4, −172.4 ± 5.5 for Ge(OH)4, −77.8 ± 1.3 for B(OH)3, −112.6 ± 4.6 for As(OH)3, and −160 ± 12 for Sb(OH)3, correspondingly. For indicated species the recommended values of KD are tabulated at T ≥ 523.15 K.