Abstract
A sphere falling viscometer using a diamond anvil high pressure cell reported in the former report is improved to measure the viscosity at an elevated temperature under high pressure. A standard liquid JS200 for viscometer calibration and a synthetic lubricant UNIVIS P12 are employed to evaluate the accuracy and reproducibility of this viscometric system. The viscosities obtained show good agreement with those of NRLM, and observed temperature and pressure ranges are two or three times as large as those NRLM. The viscosity-temperature relations obtained under high pressure can be expressed by Walther's equation, and are consistent with the Eyring model employing an absolute rate process.
