A refrigerator is proposed comprising a fluid mixing apparatus (100) for adding a gas, contained in a storage bottle (125) provided with a valve device (130), to a liquid within a mixing chamber (105) the mixing between the gas and the liquid within the mixing chamber forms a composite solution of mixed gas and liquid and gas being not mixed with the liquid. The pressure value of said non-mixed gas is indicative of the amount of mixed gas within the composite solution. The fluid mixing apparatus according to an embodiment of the present invention comprises a pressure detector (199) configured to detect the pressure value of the non-mixed gas within the mixing chamber and control means (145, 165, 170, 175, 180, 185, 190, 195, 197) for controlling, as a function of the detected pressure value, the opening or closing of said valve device in order to automatically adjust the gas flow from the storage bottle to the mixing chamber.
