Amagat unit

The second virial coefficient has the dimensions of a volume per mole. The unit often chosen is the Amagat unit which is by definition the molar volume of the gas at 0 °C and 1 atm. The exact value of this unit depends upon the gas considered but is approximately equal to 2-24 x 10 cm. /mole. Alternatively, it is now becoming customary to give B directly in terms of cm. /mole. 

Fig. 3. Numerical calculated position and intensities of the pure rotational spectrum of dipolarly unstable tetrahedral systems for the following parameter values (in inverse centimeters) A = 0.5, B = 5.24, kT = 200. Marked with crosses and circles and unmarked are the R, R", and R branches, respectively, with the Q transition indicated by an arrow (p is the gas pressure in amagat units).

We only give values at 50 and 100 amagat units, since the theory is restricted to low densities and since R (co) is practically a linear function of q in this region. 

Note that the value of JRT in the appropriate units is the value of the right-hand side of the given equation as p->0. This expression is tidcen from International Critical Tables (vol. lu, p. 8), and much of the p-F-2 data in the literature am quoted in this form. It is equivalent to the use of the Amagat unit of volume which is the volume of 1 mol of gas at 0 and 1 atm and is close to 22.4 dm, but varies slightly from gas to gas. 

A. Michels (translated by H. J. Michels and edited by S. Angus), A note on the Amagat unit of volume, Report PC/D30, lUPAC Thermodynamic Tables Project Centre, Imperial College, London, 1970. 

Fig. 1.16. Angular momentum and kinetic energy correlation functions for compressed nitrogen. MD simulation from [62], T = 300 K. The lines are continuous (800 amagat), close dotted (600 amagat), sparse dotted (400 amagat), dashed (300 amagat) and pairwise dotted (200 amagat). Reduced time units are the same as in Fig. 1.15.

About units. For our survey of measured spectra and the comparisons with theory that follow in Chapters 5 and 6, it is useful to remember that frequencies are often expressed in units of Hertz, or of cm-1, or in cycles per 2n seconds. In order to avoid confusion we shall distinguish the notations f,v=f /c, and co = 2nf, respectively, where c designates the speed of light in vacuum. Similarly, gas densities will be expressed as number densities, n, the number of particles per volume, or in units of amagat, q = n/Na, where Na is the number of particles per cubic centimeter of the gas under consideration for most gases of interest Na is about equal to Loschmidt s number, Na Nl = 2.686763 xlO19 cm-3 amagat-1, the particle density of an ideal gas at standard temperature and pressure. The values of fundamental constants are taken from [124],... 

Fig. 3.19. The far infrared absorbance spectrum (in arbitrary units) of pure HD at 43 amagat and 77 K (smoothed). The sharp Ro(J) lines sit upon a broad collision-induced background after [398],...

Table 5.2. Various computed binary and ternary moments M , with and without Wigner-Kirkwood corrections, for helium-argon mixtures at various temperatures. Units of Mo and Mi are 10 33 J amagat N and 10-20 W amagat N, where N = 2 and 3 for binary and ternary moments, respectively. The asterisk indicates that Wigner-Kirkwood corrections have not been made to the entries on that line [296].

Table 6.5. Temperature dependence of the moment of the enhancement spectra of hydrogen-helium mixtures in the fundamental band of H2. The superscripts 12 and 122 stand for H2-He and H2-He-He the term M 122 = M H2 He H9 + M H2—He—He)//. ancj sjmjiar for M n Units are 10-35 J amagat N and 10-22 W amagat N for the zeroth and first moments, with JV = 2 for the binary and N = 3 for the ternary moments [296].

The name amagat is unfortunately used as a unit for both molar volume and amount density. Its value is slightly different for different gases, reflecting the deviation from ideal behaviour for the gas being considered. 

Amagat volume unit - A non-Sl unit previously used in high pressure science. It is defined as the molar volume of a real gas at one atmosphere pressure and 273.15 K. The approximate value is 22.4 L/mol. 

A unit of volume (strictly a ratio of volumes) that is unique to p, V, T work is the Amagat volume, much used in the accurate studies by Michels and his colleagues at the van der Waals Laboratory, Amsterdam. The Amagat volume of a gas is the ratio between the volume of a fixed mass of the gas at any temperature and pressure and its volume at some reference temperature and pressure— 273.15 K and 1 standard atmosphere in Amsterdam work. The usefulness of the Amagat volume in reporting p, K, T measurements was explained in a report prepared by Professor Michels shortly before his death. 

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