Viscosity Measurements on Liquids to Pressures of 60 kbar

A rudimentary capillary-type viscometer for measuring viscosities between 103 and 1010 poise at high pressures is described. Measurements are reported on petroleum ether to 57 kbar where the viscosity is approximately 1010 poise and on a 1:1 mixture of n-pentane-isopentane to 54 kbar where the viscosity is approximately 106 poise. Measurement precision of the technique is a few percent, but uncertainty in absolute determination at maximum pressure is only within a factor of two. Viscous stresses are shown to decay exponentially with time even at the highest pressures, and no effects of residual stress are observed.