In order to obtain information about the physical conditions that prevail in collapsing bubbles, we can use two different types of experiments: sonoluminescence measurements and sonochemical measurements. Sonoluminescence and sonochemistry must in some way be interrelated but this interrelation is far from obvious. Indeed, the detectable products of a sonochemical reaction are rarely the products directly formed during the bubble collapse. They are the final products of a series of different steps which are generally not known. This issue will be discussed on the basis of quantitative sonochemical experimental results obtained in Brussels at two different frequencies (20 kHz and 1.7 MHz), using pulsed and continuous pressure waves. Special emphasis will be put on the time evolution of a chemiluminescent system during and after a pulse of ultrasound or during a pulses series. The evolution of the system was followed by pressure intensity measurements, light diffusion measurements, and luminescence measurements.