( ) The comparison between Boltzmann and Gibbs volume approaches shows that the temperatures converge to the same values for large N. The difference is already negligible for a 10-atoms molecule. However, for smaller molecules, the difference is significant, and it should be possible to probe it experimentally. In particular, we discuss how a common numerical approximation corresponds, in fact, to a shift from the Boltzmann into the Gibbs volume formulation.