TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process: The mixture is condensed with high-, medium- and low-boiling fractions, each of which contains one or more components. Preferred mixtures contain 20-100 wt.% non-condensable components and are condensed at 100-350 degrees C. Suitable mixtures are reaction gases obtained from the gas-phase oxidation of 3-4C alkanes, alkenes, alkanols and/or alkanals and/or precursors of these to (meth)acrylic acid. The hot mixture is cooled before condensation.Preferred Apparatus: A column with one or more cooling devices is used; suitable separating devices are column packings or fillings and/or trays. EXAMPLE - A mixture with the following composition (wt.%) and a temperature of 270 degrees C was obtained from the production of acrylic acid by catalytic gas-phase oxidation: Water (4.4), formaldehyde (0.2), acetic acid (0.4), acrylic acid (10.1), maleic anhydride (0.07), benzoic acid (0.02), acrolein (0.1), phthalic anhydride (0.01), propionic acid (0.002), maleic acid (0.0), allyl acrylate (0.001), benzaldehyde (0.001), furfural (0.001), nitrogen (76.545), oxygen (3.6), carbon monoxide (0.075), carbon dioxide (2.6), propene (0.5), propane (0.7). This mixture was passed upwards at 3040 g/hour through a column (2.6 m x 8 cm diameter; Fig. 1) fitted with 27 bubble trays; the temperature in the sump was 120 degrees C, the heat from condensation was removed by heat exchangers at trays 1 and 27, and phenothiazine (stabilizer) was added continuously at the top of the column. A high-boiling fraction taken from the bottom of the column (120 degrees C; 1 g/hour) contained 40 wt.% acrylic acid, 45.464 wt.% phenothiazine, 9 wt.% benzoic acid, 3.6 wt.% phthalic anhydride and small amounts of other organic compounds as above. A side stream taken off at tray 3 (93 degrees C; 350 g/hour) comprised mainly acrylic acid (96.914 wt.%). A low-boiling fraction taken off at tray 27 (34 degrees C; 90 g/hour) contained mainly water (87.69 wt.%), acetic acid and acrylic acid. The off gas from the top of the column (25 degrees C; 2640 g/hour) contained mainly nitrogen (88.18 wt.%), with small amounts of water and the other inorganic gases.