  What is really measured in dynamic calorimetric experiments is still an open
question. This paper is devoted to this question, which can be usefully
envisaged by means of macroscopic non-equilibrium thermodynamics. From the
pioneer work of De Donder on chemical reactions and with other authors along
the 20th century, the question is tackled under an historical point of view. A
special attention is paid about the notions of frequency dependent complex heat
capacity and entropy production due to irreversible processes occurring during
an experiment. This phenomenological approach based on thermodynamics, not
widely spread in the literature of calorimetry, could open significant
perspectives on the study of macro-systems undergoing physico-chemical
transformations probed by dynamic calorimetry.
