A recent application of the Maximum Entropy Formalism on liquid atomization problems led to the development of a mathematical volume-based drop-size distribution. This function, which depends on three parameters, is a reduction of the four-parameter generalized Gamma function. The aim of the present work is to investigate the relevance of the three parameters in the characterization of liquid atomization processes. To achieve this, a variety of experimental drop-size distributions of ultrasonic sprays were analyzed with the mathematical function. Firstly, it is found that the mathematical drop-size distribution is very suitable to represent the volume-based drop-size distribution of ultrasonic sprays. Furthermore, it is seen that when considering the three parameters introduced by the function, one of them is constant for all the situations investigated, and the other two are linked to a non-dimensional group that includes the main parameters controlling the drop production. These results are very important, since they suggest a possible development of physical models of primary atomization based on the M.E.F., which would allow for the prediction of the spray drop-size distribution. Thusfar, such a model does not exist.