The performance of packed bed adiabatic gas absorbers has been analyzed using the enthalpy and material balance equations incorporating a new parameter, f(r), defined as the fraction of the heat of absorption that is accounted for in the gas stream. An experimental programme to evaluate f(r) was carried out and the data correlated. It was found that f(r) was dependent on the thermo-physical properties and the hydrodynamic conditions. It is postulated that the mechanism by which this heat transfer occurs is by turbulence at the interface and by entrainment.