Constant composition expansion vaporization

This procedure is called flash vaporization, flash liberation, pressure-volume relations, constant composition expansion, or flash expansion. 

Water, with the chemical formula HjO, has unique properties determining its physical and chemical nature. Water behaves unlike other compounds of similar molecular weight and atomic composition, which are mostly gasses at room temperature. Some physical properties of water are presented in Table 1.1. It has relatively low melting and boiling points, unusually high values for surface tension, permittivity (dielectric constant), and heat capacities of phase transition (heat of fusion, vaporization, and sublimation). Another unusual behavior of water is its expansion upon solidification. 

If we continue the expansion from point B, the mixture progresses through a sequence of two-phase states BE. In this two-phase expansion, the pressure continues to decrease, and the vapor phase grows at the expense of the liquid. During the expansion, the compositions of the vapor and liquid change, but the overall composition remains constant at zi = 0.8. 

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