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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.

The solubilities of hydrogen and nitrogen in polystyrene have been found to be proportional to the pressure in the range 80-300 atmospheres, and the solubility constants have been determined a t temperatures up to 190".The diffusion constants of the same gases in polystyrene, at high pressure, have been measured in the range 20-190", and found to increase exponentially with temperature.A few diffusion and solubility constants have been obtained for carbon dioxide and ethylene ; and the rate of desorption of hydrogen and nitrogen from polystyrene has been studied. * (i) = Axial diffusion method ; (ii) = modified axial diffusion method ; (iii) = radial diffusion method.

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Bamford, Levi, avLd Newitt : Physical avLd 91.Measurements are recorded of the vapour pressures and freezing points of dimethyl-, diethyl-, di-n-propyl-, and di-n-butyl-zinc, trimethyl-, tri-n-propyl-, and triisopropyl-boron, solutions of trimethylboron in n-heptane, trimethyl-and triethyl-aluminium, trimethyl-and triethyl-stibine, dimethylcadmium and trimethylbismuth. From the vapour-pressure curves, the boiling points, latent heats of vaporization, and the Trouton constants have been calculated. I ;n recorded values of their physical constants. For example, in the case of the zinc alkyls recorded values of the boiling points differ by 2" for the dimethyl, by 5" for the diethyl and by 14" for the n-propyl derivative. No data for the freezing points of boron, aluminium, antimony, cadmium, and bismuth alkyls are available and the vapour-pressure data are scanty or absent.In the course of an investigation into the properties of a series of these compounds, described in subsequent papers, advantage has been taken of the availability of pure specimens to determine the vapour pressuretemperature curves, freezing points and, in some instances, the heats of combustion. The vapour-pressure and freezing-point data are included in the present paper. EXPERIMENTAL.Pressures are measured by a Bourdon gauge B, which is maintained at any desired temperature by the air-jacket J , and can be read to 0.01 mm.We wish to thank Miss B. M. Gaunt, B.Sc., for valuable assistance in preparing the pure samples of alkyls used in this work.Pressures were measured over the range 0-120" without any evidence of decomposition.This was prepared from n-butyl iodide by the above method.Similarly, diethylmercury (20 g.) and aluminium (6 g.) gave an almost theoretical yield. This was prepared by the action of antimony trichloride on the Grignard reagent.Yield, 45%. Triethylstibine.The ether was separated by repeated fractionation under reduced pressure and in a vacuum. Yield 80%.