Abstract: A dental handpiece includes a turbine arranged in a handpiece head for rotating a tool, wherein the turbine is supported by slide bearings or roller bearings arranged on the side of the rotor or turbine facing the tool and on the side of the rotor or turbine facing away from the tool. The handpiece head includes an air duct for the propulsion air and a return duct for the returned or used air. At least one opening in the turbine chamber wall in the area near the axis is connected through a connecting duct to the return duct.

Abstract: A chucking device for holding a dental tool by a collet chuck with collet chuck sleeve, wherein the collet chuck can be released by a push button against the force of clamping spring. The collet chuck sleeve has at both ends thereof axial slots, so that it is constructed at both ends as a collet chuck. The casing of the collet chuck is undercut at both ends, wherein the undercut at the side of the tool is mounted in an axially fixed, but rotating conical seat and the undercut on the side of the push button is mounted in a conical seat of an actuating member. The actuating member is under the influence of the clamping spring and, for releasing the collet chuck, the actuating member is displaceable against the force of the clamping spring toward the axially fixed seat. Instead of the collet chuck, it is also possible to provide two axially spaced apart groups of radially displaceable clamping elements.

Abstract: A method for economically producing high purity zirconium oxide by dissolving calcium zirconate in hydrochloric acid and adjusting the fluorine content of the solution and then mixing this solution with sulfuric acid and heating the mixed solution to a temperature of more than about 80.degree. C. for at least 10 minutes. The resulting suspension is diluted with water and allowed to stand and the precipitate is then filtered, washed and mixed with ammonium carbonate. Carbon dioxide is then passed into the solution, the resulting precipitate is filtered, washed, dried and finally calcined. The zirconium oxide obtained is of sufficiently high purity to be used in the manufacture of electro-ceramics.

Abstract: A method for the separation of a mixture of fine particles wherein the fraction to be separated has a surface which is more reactive chemically than the remaining fractions by grinding the mixture so that the fraction to be separated has a particle size of less than 50.mu., suspending the ground mixture at a temperature less than 100.degree. C. in a diluted aqueous solution of zirconium oxychloride or zirconium oxynitrate, allowing the solution to settle and decanting the deposited material and then adding a base to the decantate to precipitate the residue therein. This process allows selective separation of the fractions having a more chemically reactive surface without the use of complex equipment and with a minimum use of expensive additives and chemicals.

Abstract: This invention relates to a process for preparing carbonated zirconium oxide hydrate which comprises adding zirconium oxychloride . 8 H.sub.2 O to a saturated aqueous ammonium chloride and/or alkali chloride solution which, based upon zirconium oxychloride . 8 H.sub.2 O, contains at least equimolecular amounts of ammonium carbonate and/or alkali carbonate,Separating the resulting precipitated reaction product,And washing said product chloride-free with water.

Abstract: This invention relates to a process for preparing carbonated hydrated zirconium oxide which comprises dispersing zirconium oxychloride in an inert, non-polar solvent and reacting it, without the addition of water, with an at least equimolar quantity of ammonium carbonate or potassium carbonate, and separating the reaction product.