Departure enthelpy vs. Excess enthelpy vs. Residual enthelpy?

[maistral]

TL;DR

The title.

I am getting confused as these three kinds of 'enthalpies' keep on appearing in the literature I am reading. How are they different? From what I can understand, they are all deviations from ideality, and that they can be 'estimated' using an equation of state. Other than that, how do they differ from each other?

 

[Chestermiller]

Summary:: The title.

I am getting confused as these three kinds of 'enthalpies' keep on appearing in the literature I am reading. How are they different? From what I can understand, they are all deviations from ideality, and that they can be 'estimated' using an equation of state. Other than that, how do they differ from each other?

A residual property of a pure gas or gaseous mixture represents the value of the property relative to an ideal gas or ideal gas mixture at the same temperature or pressure. So the word residual applies to gases.

An excess property applies to liquid solutions, and is the value of the property relative to an ideal liquid solution at the same temperature and pressure.

See Chapter 11 of Smith and Van Ness or Perry's Handbook.