An extension of a conventional apparatus is presented and applied in order to measure viscosities and densities of pure and gas-saturated liquids at elevated pressures. The viscosity of n-decane at pressures up to 10 MPa is shown to deviate less than 1% from literature values. Viscosities and densities of a light sweet crude oil are reported at pressures in the range of atmospheric to 23 MPa and from 268 to 308 K. Both viscosity and density of pure hydrocarbon liquids increase as a function of pressure, while they decrease as expected in the presence of dissolved methane. For seawater, an abnormal behavior is found with respect to the pressure dependency of the viscosity.
