Series evaluation of the isotherm data of CO2 between 0 and 150°C. and up to 3000 atm

The usual method of expressing the results of isotherm measurements is in a series in terms either of the pressure or the density. From the value of the first coefficients of the powers of p and d, theoretical conclusions have been drawn (Fowler 1929, p. 211 etc.). A series evaluation of an isotherm is also of great help in finding the pressure at a given density or the density at a given pressure. An attempt was therefore made to represent the isotherm data of CO2 given in previous publications (Michels, A. and C. 1935; Michels, A. and C. and Wouters 1935) by a series equation. Gerver (1934, p. 71) has already shown that the expansion in a p series is less adequate for isotherms of high densities and the evaluation was therefore carried out in a d series. It will be shown in the present paper that for the densities under consideration the d series also does not give an ideal representation of the experimental results. 1—A first trial was made to represent the experimental data in a series pv = A + Bd + Cd2 + Dd4 + Ed6 + Fd8, in which d is expressed in Amagat units. Following a suggestion of Kamerlingh Onnes, the odd powers, except the first one, were omitted.