PVT Relations of Liquid Carbon Tetrachloride and n-Perfluoroheptane and a Test of the Clausius-Mosotti Equation

Values of (∂P/∂T)v for CCl4 and n-C7F16 have been measured over a range of approximately 20° and 160 atmospheres. The linear relation between P and T found in earlier studies to hold over 20 atmospheres for a number of liquids and solutions is here confirmed over the much larger range. One corollary is that (∂Cv/∂V)T=0; another is that the isothermal compressibility of C7F16, not hitherto known, is 2.38×10—4 atmosphere—1 at 25° and 1 atmosphere, and could easily be calculated for other temperatures. The terms in the equation (∂E/∂V)T=T(∂P/∂ T)v—P are given, also the function V2(∂E/∂V)T, shown in the earlier studies to be constant. Its value for CCl4 confirms the earlier studies; for n-C7F16 it is 101.5 atmospheres×liters.2 The dielectric constant of n-C7F16 has been measured at 16.0° and at 38.4°, and over a pressure range of 115 atmospheres. The values obtained conform closely to the Clausius-Mosotti equation, giving a molar polarization of 49.1 cc.