Open Access

Percy W. Bridgman

• A new method of measuring compressibility and thermal expansions of liquids has been developed, in which the liquid is enclosed in a sylphon, which is then exposed to external hydrostatic pressure, and the volume change determined from the change of length of the sylphon. This method has been applied to 18 liquids at 0°, 50°, and 95° up to a pressure of 12000 kg, or to the freezing pressure, and the results are collected into extensive tables giving the volume as a function of pressure aand temperature over this range. In the discussion it is shown that small scale differences in the volumes of various isomers persist to high· pressures, and there is no simple connection between the relative densities at atmospheric pressure and at high pressure, The compressibility falls off rapidly with rising pressure, as was found in a preceding investigation. Two liquids are found to have the abnormally low compressibility of water. Thermal expansion also drops off by a large factor with increasing pressure, but not as much as the compressibility, as was also found before. The "pressure coefficient" (δp /δt) , is not a function of volume only, as has often been supposed, and suggestions are made as to the theoretical significance of this.