The Equations of Haar, Gallagher, and Kell

In 1978, Haar and Gallagher developed an equation of state for ammonia, and in 1984 Haar, Gallagher and Kell published an equation of state for water. Both equations became accepted as standards, and although they have been superseded by more recent formulations by Tillner-Roth et for ammonia and Wagner and PruC for water, they are still frequently used in industrial applications. 

The equation by Haar and Gallagher for ammonia is given in specific quantities by 

The equation of state for water includes a so called base function as well as the residual component and the ideal gas contribution, 

The base function is used to represent the dilute-gas region and was derived from the Ursell-Mayer virial theory, 

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