Viscosity study of tert-butyl alcohol aqueous solution by Brownian motion and gravimetric capillaries

Abstract Molecular interactions influence the viscosity of liquids and reveal the nature of liquid mixtures. Water and tert-butyl alcohol mixtures exhibit strange viscosity behavior induced by concentration differences. The macroscopic viscosity of the aqueous alcohol solutions was examined with a Ubbelohde viscometer and a gravimetric capillary. The microscopic viscosity was calculated from the trajectory analysis of the Brownian motion of 1 μm sized polystyrene beads. A discrepancy between the macroscopic and microscopic viscosity was observed specifically at lower concentrations, indicating that the water fluctuation in the solution is critical for the Brownian motion. A new method investigating molecular interactions using Brownian motions is demonstrated.