The invention relates to a device for producing a gas mixture consisting of HMDSO and oxygen, whereby process gas is produced. In order to be able to continuously produce a large volume of process gas using such a device and to be able to withdraw the same at practical processable temperatures, the invention provides that a number of filling packages (2) are stacked in an elongated essentially vertical column (1) that can be cooled. In addition, an inlet tube (3), which is inserted into the column (1) from the exterior, and a gas outlet connection (6), which leads to the exterior, are secured in the upper area of said column (1). Devices (26) are also provided for measuring the temperature, the pressure and the amount of the exiting gas mixture. In addition, a distribution cup (29) which spans the cross-section of the column (1) and which is provided with gas flow-through openings (38) is placed underneath the inner discharge end (4) of the inlet tube (3).