Abstract: An apparatus for producing seed crystals in melts has a vertically oriented, closed vessel having a vessel base and having at least one inlet for the melt and having at least one outlet opening for the inoculated melt provided with seed crystals. A preferably annular region of the vessel wall is constructed as a cooling surface. In the interior of the vessel there is arranged a scraping unit which comprises a motor-driven rotating shaft which extends axially through the vessel as far as a point just short of the vessel base. At its end towards the vessel base, the shaft is provided with at least one scraping arm which, starting from the lower end of the shaft close to the vessel base, extends first in the direction towards the vessel wall and thence substantially parallel to the annular cooling surface and axially parallel to the drive shaft.

Abstract: There is disclosed a process for purifying ground- and wastewaters, which comprises subjecting said waters to a membrane separation process between a biological treatment step and adsorption on activated carbon.

Abstract: There is disclosed a process in which a melt of a 2-aryl-2H-benzotriazole containing colored contaminants, or a solution thereof in an organic nonpolar solvent, is purified by treatment with a strongly acidic synthetic cationic exchange resin.

Abstract: A process for the production of amino-I-acid (2-naphthylamino-5,7-disulfonic acid) starting from Tobias acid (2-naphthylamine-1-sulfonic acid), which comprises sulfonating Tobias acid with fuming sulfuric acid (oleum) isothermically at room temperature, further sulfonating the resulting 2-naphthylamine-1,5-disulfonic acid without isolation, by rapidly heating the reaction mixture to 110.degree. to 140.degree. C. to give 2-naphthylamine-1,5,7-trisulfonic acid, hydrolyzing the trisulfonic acid in sulfuric acid having a concentration between 80 and 98%, at a temperature of 100.degree.-180.degree. C., to give the amino-I-acid, precipitating this latter from dilute sulfuric acid and isolating it from the reaction mixture, and the amino-I-acid obtained by this process.