Editing Virial equation of state

The virial equation of state is used to describe the behavior of diluted gases. 
It is usually written as an expansion of the [[compresiblity factor]], <math> Z </math>, in terms of either the
density or the pressure. In the first case:
 
:<math> \frac{p V}{N k_B T } = Z = 1 + \sum_{k=2}^{\infty} B_k(T) \rho^{k-1}</math>.

where 

* <math> p </math> is the pressure

*<math> V </math>  is the volume

*<math> N </math> is the number of molecules

*<math> \rho \equiv \frac{N}{V} </math> is the (number) density

*<math> B_k\left( T \right) </math> is called the k-th virial coefficient

[[category:equations of state]]