Abstract: Homogeneous compressed gas mixtures with SF.sub.6 and a gas with a density at least 4 grams per liter lower can be prepared by using a mixing station with at least the following elements: a gas premixer in which the separate gases are brought together; a static mixer and/or a buffer tank connected thereto; a compressor connected to the buffer tank or static mixer; and when a buffer tank is used, a return line from the compressor output to the buffer tank. Mixtures of SF.sub.6 and N.sub.2, useful for example as insulating gas for current conducting underground cables, can be produced by this process, which is capable of processing large flow rates. Mass flowmeters ensure high precision and reliability. Also disclosed is a mobile mixing station for implementing this process.