Determination of the critical constants of high-boiling hydrocarbons Experiments with gallium as a containing liquid

Abstract

The critical temperature and pressure and the critical end-point temperature and pressure of n-nonane, n-decane, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene, and naphthalene were measured with mercury and compared with the critical temperature and pressure of n-nonane, 1,2,4-trimethylbenzene, and naphthalene when measured with gallium. To within the accuracy of the measurements, the values of the critical temperature and pressure obtained with gallium and with mercury were the same. However, the chemical and physical properties of gallium are such as to make it very difficult to devise a procedure that would ensure highly accurate results. Its use as a confining liquid is therefore limited. The differences between the critical temperature and pressure of the pure compounds and critical end-point temperature and pressure of the binary mixtures of mercury + hydrocarbon, ΔT and Δp, respectively, show that the solubility of mercury has a relatively small effect ΔT on the critical temperature, whereas Δp, the partial pressure of mercury, is proportional to, but less than, the vapor pressure of pure mercury. A plot of log 10( Δp kPa ) against ( T K ) −1 gives a linear relation which serves as a method of estimating the partial pressure of mercury at a given temperature.