Abstract: Polyester yarn is made by melt spinning the polyester filaments which are then cooled at least to solidification and heated by counterflow with prestretching to a crystallinity in excess of 24%. The prestretched filaments are gathered and stretched to after-stretching at a temperature of 80.degree. C. to 250.degree. C. to a final titer of 1.0 dtex to 7.5 dtex with a stretching ratio of 1:1.5 to 1:1.15. The yarn is then wound up at a rate of 5000 to 8000 m/min.

Abstract: Polyester yarn is produced from melt spun filament by prestretching the filaments individually in counterflow with a gaseous medium and then afterstretching the polyester filaments with an individual titer of 1.0 dtex to 7.5 dtex with a stretching ratio of 1:1.5 to 1:1.15 at a temperature of 80.degree. to 250.degree. C. The filaments are collected and then wound up as a yarn at a speed of 5000 to 8000 m/min.

Abstract: Oxygen-containing compounds are prepared by oxidizing a hydrocarbon in the liquid phase with a gas containing molecular oxygen, at elevated temperatures and under superatmospheric pressure, by a continuous process in which the said gas is fed into the liquid reaction mixture, in a downward direction, at several points along the reaction zone via nozzle apertures, so that it emerges at each nozzle aperture with a velocity of from 0.01 to 1 m/sec in an amount of from 0.001 to 10 liters per second per nozzle aperture, and the said reaction mixture is brought into substantially uniform contact with the gas containing molecular oxygen, over the volume of the reaction zone.