A novel high pressure tool: the solvation pressure of liquids

Abstract

Co-solvents were studied to determine if the change in the cohesive energy density (CED)generates an effective solvation pressure equivalent to the application of an externalhydrostatic pressure. Raman modes of chloroform under hydrostatic pressure withco-solvents (chloroform–ethanol, chloroform–acetone) and in the vapour phase wererecorded. In some cases the Raman frequency shifts indicate that the solvation pressurebehaves as a true hydrostatic pressure. The pressure-induced gelation of starch grains wasstudied in aqueous media. A higher co-solvent concentration is postulated to put the grainsunder effective negative pressure, and indeed an increase in the external pressure needed forgelation was seen after the introduction of solvents. The quantitative agreement betweenthe change of solvation pressure and hydrostatic pressure is very good over a wide range ofsolvent concentration.