Density, Speed of Sound, and Viscosity Measurements of Reference Materials for Biofuels

Measurements of density, speed of sound, and viscosity have been carried out on liquid certified reference materials for biofuels as a function of temperature at ambient pressure. The samples included anhydrous and hydrated bioethanol and two biodiesel fuels from different feedstocks, soy and animal fat. The ethanol samples were measured from a maximum temperature of 60 to 5 °C (speed of sound) and to −10 °C (density and viscosity), respectively. The biodiesel samples were characterized from 100 °C (density and viscosity) and from 70 °C (speed of sound) to 10 °C (animal fat-based) and 5 °C (soy-based). Densities were measured with two vibrating-tube instruments of different accuracy. The speeds of sound were measured with a propagation-time method in an acoustic cell that was combined with one of the densimeters. Viscosities were measured with an open gravitational capillary viscometer and with a rotating concentric cylinder viscometer, according to Stabinger. The measurement results are reported with detailed uncertainty analyses

Measurement and Correlation of Densities and Dynamic Viscosities of Perfluoropolyether Oils

The densities and dynamic viscosities of five different polydisperse perfluoropolyethers (PFPE) were measured at atmospheric pressure over the combined temperature range 263.15–373.15 K. For one PFPE being considered as a high-temperature high-pressure viscosity standard reference material, measurements were made on two separate samples to examine the lot-to-lot variability in density and viscosity; significant variability was observed only for the viscosity data. Experimental data were correlated as a function of temperature. A simple quadratic equation was used for density, while three equations (DIPPR, VFT, and Waterman) were applied to the viscosity data. The DIPPR equation represented the viscosity data with deviations approximately an order of magnitude lower than the other two equations