A Falling Body High-Pressure Viscometer

This paper describes the construction, working equations, and operation of a semi-automated high-pressure falling body viscometer used in the pressure range 0.1 MPa to 400 MPa and at temperatures between 255 K and 368 K. The viscometer employs self-centering sinkers, each a hollow cylinder with a solid hemispherical face. This results in a viscosity-independent sinker calibration constant. With sinkers of different diameters, a broad range of Reynolds numbers is accessible. The dependence of the calibration constants (A) on sinker clearance (c), A proportional to c(-3), conforms with theory. It has been used for both high and low viscosity molecular liquids and viscous ionic liquids. It is hoped that a complete description may be of use to others wishing to build and operate such an instrument.