The compression of n-hexane, n-heptane, n-octane, and of binary and ternary mixtures of these hydrocarbons has been determined up to 5000 atmospheres, and at O", 25", 40°, and 60". The isotherms are expressed in the form of the Tait equation.The energy-volume coefficients, (aE/a V ) T and the pressure coefficients, (aP/aT)v, are found to be pure volume functions, and at all the temperatures and pressures employed the hydrocarbons mix without expansion or contraction in volume.
MEASUREMENTSof the decrease in volume undergone by liquids at high pressures are an important source of information about the intermolecular forces, and contribute towards a general theory of the liquid state. The first systematic study was made by Amagat ( A m . Chim. Phys., 1893, 29, 68, 505) on twelve organic liquids up to 3000 atmospheres and in the range 0-200".Bridgman (" The Physics of High Pressure," 2nd edn., 1949) developed new experimental methods by which Amagat's results were repeated and extended to 12,000 kg./cm.a, between 20" and 80". Bridgman (up. cit. ; see also Proc. Amer. Acad. Avts Sci., 1949, 77, 115-146) has measured the volume decrements of a large number of other liquids to 12,000 kg./cm.2, and in many cases to 40,000 or 50,000 kg./cm.a, but generally not at a sufficient number of different temperatures to enable detailed thermodynamic analysis of his results to be made.
