Since effervescent pharmaceuticals are more sensitive to ambient humidity during the manufacturing process and storage, the strict control of their carbon dioxide content becomes a prerequisite to guarantee their physicochemical stability. Indirect gravimetry is a simple and precise method that consists in taking the weight before and after the effervescent reaction allowing to determine the released amount of carbon dioxide. Some authors have used it with devices that lead to longer analysis times and poor accuracy of measurements (due to the excess of released carbon dioxide). The device that we have built (proposed name "CARBONDIOXIMETER") is very easy to set up, and yields quick, accurate, precise and reproducible results. An assay takes three minutes in an acidic medium and five minutes in carbon dioxide free water). Moreover, through the interconnection of scales, registration and treatment of the results can be performed by a printer or a computer. Thus, the "Carbondioximeter" is contributing to the control of physicochemical stability of effervescent pharmaceuticals during the manufacturing process and storage.