This paper is devoted to power measurements at different locations of an ultrasonic device: the power displayed at the frequency generator, the electrical power input at the transducer (by measuring the applied voltage and intensity) and the acoustic power dissipated in the liquid medium (determined by a calorimetric method). These different measurements were recorded and compared for different media and different liquid heights in the reactor. When a chemical reaction takes place, the chemical yield was plotted against the different power measurements. The dissipated acoustic power per unit volume, although less accurate, appears to be the best measurement to establish a correlation with the influence of ultrasound on a chemical reaction.