Density measurements of compressed solid and liquid argon

A method is described by which the equation of state of liquids and reasonably soft solids can be determined experimentally. A unique feature of the apparatus is that while the quantity of material occupying a known volume is weighed, pressure and temperature are measured concurrently. First results are reported for solid and liquid argon in the temperature range from 96 to 154 °K and at pressures from about 100 to 2000 kg/cm2. The liquid data determine the PVT surface to within 0.1% for each of the variables. Data for solid argon have so far been limited to a zone of 20-degree width along the melting line. Thermal expansion and compressibility of the liquid are computed. From the volume change on melting it is concluded that the latent heat increases linearly over the full pressure range.