Lester Haar

Thermodynamic Properties of Ammonia

An analytic thermodynamic surface has been fitted to the experimental data for ammonia for the temperature range extending from the triple point to 750 kelvins and for the pressure range extending from the dilute gas to 500 MPa (5000 bar). Values for the thermodynamic properties are tabulated at closely spaced intervals. A major part of the correlation was devoted to a study of the extent to which thermodynamic inconsistencies degrade the accuracy of the derived properties. This study focused as much on methods for correlating the data as on the data themselves. As a consequence, we are able to assign close tolerances to the tabulated thermodynamic properties over the range of the surface, including properties for the coexisting phases and even close to the liquid‐vapor critical point.

High‐Speed Machine Computation of Ideal Gas Thermodynamic Functions. I. Isotopic Water Molecules

A procedure is developed for the machine computation of the partition functions for non‐rigid rotating anharmonic oscillators. Vibrational‐rotational coupling terms and low temperature rotational corrections are included. A general code has been designed to permit the calculation of the ideal gas thermodynamic functions for a large variety of molecular structures on the National Bureau of Standards Eastern Automatic Computer—SEAC. The method is illustrated by evaluating the thermodynamic functions for an asymmetric top molecule. Tables of Cp0/R, (H0–E00)/RT, (E00–F0)/RT, and S0/R have been evaluated for H2O, HDO, D2O, HTO, DTO, and T2O at close intervals from 50° to 5000°K. The time required for these computations is of the order of several minutes per molecule. The results for H2O are in good agreement with those obtained by direct summation.

A new representation for thermodynamic properties of a fluid

It is proposed to consider the contribution of the nonisolated molecular pairs to the configurational Helmholtz energy, i.e., the quantity f*/RT−Bρ, where the product of the second virial coefficient B times molar density ρ covers the contribution of the isolated pairs. Especially illuminating is the difference function Δ = (f*/RT−Bρ)real  fluid −(f*/RT−Bρ)hard  body  fluid. From the few examples given it seems that this difference function is of a general nature provided that the anisotropy of the hard bodies corrsponds to the anisotropy of the molecules of the real fluid. The difference function can be correlated empirically in a simple way and can be used for estimating thermodynamic properties at intermediate and low densities from high density results.

Solubility of Condensed Substances in Dense Gases and the Effect on PVT Properties

An analytic relation is derived in terms of the molecular interactions for the density dependence of the solubility of a liquid or solid in a dense gas using a modified van der Waals equation. It is shown that at high gas densities the solubility is sharply reduced. It is also shown that the effect of the solubility enhancement on high‐density PVT measurements is smaller than previously thought. The analysis is applied to the case where the condensed material is liquid mercury. Solubility‐vs‐density isotherms and the effect of the solubility on PVT measurements are obtained at 50, 150, 250, and 400°C for the following gaseous species: He, H2, Ne, Ar, Kr, Xe, N2, NH3, H2O. The need for accurate experimental data at high gas densities to test further the essential features of the analysis is discussed.

High‐Speed Machine Computation of Ideal Gas Thermodynamic Functions. II. The Diatomic Free Radicals of the Isotopic Hydrides of Oxygen and Sulfur

The partition functions for the free radicals are obtained in closed form. They include terms to account for the special low‐temperature effects arising with these molecules. The splitting of the 2π ground state is complicated by the uncoupling of the electronic spin from the nuclear axis. In addition to this effect the partition function includes first‐order corrections for rotation‐vibration coupling, rotational stretching, and vibrational anharmonicity. Tables of thermal functions are computed on the NBS Eastern Automatic Computer—SEAC—from 50° to 5000°K for OH, OD, OT, SH, SD, and ST.