We present a review of some aspects related to the experimental validity of the Sackur?Tetrode
equation for the entropy of monatomic ideal gases. First, we examine the main theoretical
assumptions which underlie the statistical derivation of the equation. Second, we discuss how
entropy can (and cannot) be measured in the laboratory. And third, we comment on to what extent the
experimental validation of the equation can be considered an evidence for an absolute scale of
entropies.