A CONTINUOUSLY WEIGHED PYCNOMETER FOR MEASURING FLUID PROPERTIES

This paper documents the construction details and experimental procedu res for the continuously weighed pycnometer used in our laboratory to measure fluid properties such as densities, saturation pressures, phas e boundaries. and isothermal compressibilities. This apparatus consist s of a cell suspended from an electronic balance at all times and a va riable volume bellows cell which is used to adjust the confined sample density within an isothermal enclosure. The principal advantages of t his apparatus are rapid measurement and relatively high accuracy. Some experimental results are presented to illustrate capability. The acce ssible experimental ranges are 100-450 K up to 200 MPa; measurement ac curacy is 0.1% or better.