The Virial Equation Explicit in Pressure

An alternate form of the virial equation uses a power series in p. The result is 

This form of the virial equation usually does not represent the properties of the gas as well as does equation (A3.3), but it is often more useful since it can be solved explicitly for Vm. The coefficients in equations (A3.3) and (A3.5) are related through 

If p is not high, terms beyond the second and third virial coefficients in equation (A3.3) and (A3.5) are usually small and can be neglected. This is fortunate, since experimental data are usually not accurate enough to give reliable values for the higher order terms. At low pressures, equation (A3.5) is often used and truncated after the second virial coefficient so that 

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