# Enthalpy

**Enthalpy** () ^{[1]}^{[2]} is defined as:

where is the internal energy, is the pressure, is the volume.
is a *conjugate pair*. The differential of this function is

From the Second law of thermodynamics one obtains

thus we arrive at

For we have the following *total differential*

## References[edit]

- ↑ J. P. Dalton "Researches on the Joule-Kelvin effect, especially at low temperatures. I. Calculations for hydrogen", KNAW Proceedings
**11**pp. 863-873 (1909) - ↑ Irmgard K. Howard "H Is for Enthalpy, Thanks to Heike Kamerlingh Onnes and Alfred W. Porter", Journal of Chemical Education
**79**pp. 697-698 (2002)