Liquid phase PVTx properties of carbon tetrachloride-octamethylcyclotetrasiloxane binary mixtures

Abstract

Measurements are reported for the compressions of pure carbon tetrachloride, octamethylcyclotetrasiloxane, and three of their mixtures from atmospherlc to near freezing pressures at temperatures from 273 to 413 K. Nine isothermal equations of state were tested for precision in description of the data. Calculated excess volumes of mixing are reported. Comparison is made with available PVT data and isothermal and adiabatic compressibility results at atmospheric and elevated pressures. Important advances toward better understanding of the liquid state have been made recently as a result of studies which use as a starting point the hard-sphere model. The structure of a real fluid is determined primarily by the repulsive forces between the molecules while the attractive forces may be considered a uniform potential field which holds the molecules together. The methods for describing the attractive forces become increasingly important in the compressed liquid region. These theories, when dealing with mixtures, are sensitive to the difference in molecular sizes. A mixture which has been studied at atmospheric pressure because of the spherical symmetry of its components as well as the large disparity in their size is carbon tetrachloride-octamethylcyclotetrasiloxane (OMCTS). We here describe measurements of the compressions of the two pure components and three of their mixtures. These data allow testing of isothermal equations of state as well as detailing the effect of pressure on the excess volume and hence the Gibbs free energy. Experimental Program and Results