  Two equations for the calculation of the critical energy required for
homogeneous nucleation in a superheated liquid, and the related critical radius
of the nucleated vapour bubble, are obtained, the former by the direct
application of the first law of thermodynamics, the latter by considering that
the bubble formation implies the overcoming of a barrier of the free enthalpy
potential. Comparisons with the currently used relationships demonstrate that
the sensitivity of the bubble chambers employed in dark matter searches can be
sometimes notably overestimated.
