On shear stresses in liquids at high pressure

A method has been developed by which experimental determinations may be made of the pressure and temperature limits of hydrostatic conditions in any liquid pressure transmitting media. Some experimental results for pentane, H62/56 oil and a polyphenyl ether are presented, and pressure-temperature diagrams are drawn for the last two. It is suggested that above 30 kb shear stresses may result from very high viscosity rather than from freezing. Some consequences of assuming the viscosity mechanism are deduced, and the experimental observations are used to provide empirical constants in equations predicting the shear stress and the pressure at which deformation occurs in particular circumstances. Implications of the work for the design of high pressure experiments are discussed.