Viscosities of Tetraalkylammonium Bromide Aqueous Solutions under High Pressure

Abstract

The viscosities of 0.1mol·kg^-1 aqueous solutions of tetraalkylammonium bromide (R₄NBr; R=Me, Et, n-Pr, and n-Bu) were measured at 5.0, 10.0, 15.0, 25.0, 40.0, and 50.0°C up to 375MPa, using a high pressure rolling-ball viscometer. The reproducibility of the viscosities under high pressure was within ±1%. The viscosity minimum observed at 5.0°C for pure water became shallow or disappeared by adding R₄NBr salts and with increasing temperature. The additive effect became larger in order of the alkyl chain length of R₄NBr salts. The activation energy (E_v) and activation volume (V_v) for the viscous flow of aqueous solutions of R₄NBr were estimated at each pressure. The minimum of E_v at about 250MPa was observed and its minimum became shallow in order of the alkyl chain length of R₄NBr. The V_v of R₄NBr increased with increasing pressure.