This invention relates to a method for the determination of gas in a fluid, wherein the mixture of gas and fluid both is delivered by a pump and is subjected to a change in volume and pressure, operating parameters of the pump, which represents the change in volume and pressure, are detected, and from the operating parameters of the pump the gas content is determined in consideration of a system compressibility, wherein the system compressibility in the pumping device filled with gas is determined by sequence of process steps. The invention furthermore relates to an apparatus for performing this method into a dialysis machine which contains a corresponding apparatus.
