Abstract: A drum refiner for grinding fibrous material, preferably chips, has an engine-driven drumshaped rotor which is placed on a horizontal shaft. The rotor has grinding surfaces extending parallel to the rotor axis and corresponding opposing grinding surfaces arranged on the housing. The grinding elements are placed symmetrically about at least one material feeds which are conveniently evenly distributed around the circumference of the rotor. The grinding surfaces begin parallel to the axis and contiguously increasing in inclination forming a grinding gap inclined towards the rotor axis at an angle of approximately 5.degree. to 45.degree., preferably 15.degree.. The second embodiment includes grinding surfaces contiguously increasing in inclination and ending with an angle of inclination of approximately 90.degree. to the rotor axis.

Abstract: In a process for the electrolytic pickling of a high-grade steel strip, in particular a hot strip of high-grade steel, the hot strip of high-grade steel is alternately anodically and cathodically pickled in an aqueous solution of Na.sub.2 SO.sub.4 and subsequently in an aqueous solution of NaNO.sub.3 and NaF, as a result of which the formation of dangerous nitrous gases is prevented.