Abstract: In the process according to the invention, the cellulose ether to be depolymerized is depolymerized in the form of an acid slurry in an apparatus which consists of an acid-resistant material and is provided with an inlet and outlet, where the inlet and outlet are separated from one another by a filter element, at a temperature above the flocculation temperature of the depolymerized cellulose ether in the space between the inlet and the filter element, subsequently neutralized and then separated from the filtrate by releasing the filtrate, which, in contrast to the cellulose ether, is not retained by the filter element. If necessary, this can be followed by purification and drying of the cellulose ether.

Abstract: A description is given of superconducting substances having a content of Bi, Sr, Ca and Cu, and of processes for their preparation from the metal oxides within a range which is specified by the overall composition Bi.sub.a (Sr,Ca).sub.b -Cu.sub.6 O.sub.x, where a=3-24 and b=3.23-24, with an Sr/Ca atomic ratio of 1:9-9:1 and a Bi:(Ca+Sr) atomic ratio of 0.3-1.5. The transition temperature is at least 60 K. The principal phase crystallizes in the orthorhombic system. The pure compounds Bi.sub.4 (Sr,Ca).sub.4 Cu.sub.2 O.apprxeq..sub.12 and Bi.sub.4 (Sr,Ca).sub.6 Cu.sub.4 O.apprxeq..sub.20.

Abstract: To prepare a phase-pure, ceramic oxide superconductor which contains, in addition to copper, at least one alkaline earth metal from the group comprising Ba, Sr and Ca, and at least one metal from the group comprising Y, La, Tl, Pb and the rare earths, for example of YBa.sub.2 Cu.sub.3 O.sub.7-x, a solution is prepared which contains the metal components in the atomic ratios of the superconductor. The metals are precipitated as oxalates by combining this solution with an oxalic acid solution, the mixture of the oxalates is separated off, dried and decomposed to form the oxides, and the latter are subsequently sintered at temperatures of from 700.degree. to 900.degree. C. in the presence of oxygen to form the superconductor. In this process, the heating of the metal oxalates and the oxides formed therefrom up to 700.degree. C. is carried out at a maximum oxygen partial pressure of 50 mbar, preferably in an inert gas.

Abstract: Alkaline earth metal indates of the formula (Sr,Ca)In.sub.2 O.sub.4 can be converted by sintering or fusing into compact moldings which, owing to their stability are suitable even at temperatures of at least 800.degree. C. as reaction vessels for chemical reactions in the presence of bismuth (III) oxide and/or alkaline earth metal oxides.

Abstract: An alkaline earth metal chelate complex of 2,2,6,6-tetramethylheptanedione of the formula (I)M.sup.2+ (C.sub.11 H.sub.19 O.sub.2).sup.-.sub.2.L.sub.k (I)is described, in which M is calcium, strontium or barium, L is a ligand and k is a number from 1 to 3, the complex being free of water of hydration and the ligand L being an aliphatic ether having at least two oxygen atoms in the molecule. A process for the preparation of the chelate complex and its use for the production of coated substrates are also described.

Abstract: The invention relates to a process for producing a bismuth-, copper-, strontium- and calcium-containing high-temperature superconductor, in which an aqueous solution is produced which has a pH of 0.5-4 and which contains the metals in an atomic ratio corresponding to a high-temperature superconductor, the solution is combined with an oxalic acid solution to precipitate the metals quantitatively as oxalates, the oxalates formed are separated off and decomposed thermally to form the oxides and the latter are reacted in the presence of oxygen at temperatures above 700.degree. C. to form the desired high-temperature superconductor. The process comprises concentrating the aqueous solution of the metal until a precipitate begins to appear and using the oxalic acid as a solution in an organic solvent which is miscible with water The oxalates are decomposed at 550-700.degree. C. in the presence of oxygen.

Abstract: Solutions containing the cations of the metals Y, Ba, Cu in the atomic ratio 1:2:3 or the cations of the metals Bi, Sr, Ca and Cu having the atomic ratios of a high-temperature superconductor bound to polyacrylic acid in water as dispersant and having a viscosity of 150-10,000 cSt (at 20.degree. C.) serve to produce superconducting filaments or coatings.To produce a superconducting filament, a solution is forced through a nozzle and the extruded filamentous strand is left to solidify in an organic solvent which is miscible with water, the filament is isolated, dried and heated to at least 800.degree. C. in the presence of oxygen, annealed at at least 800.degree. C. for at least one hour in the presence of oxygen and then cooled.

Abstract: An oxide ceramic superconductor can be obtained if the oxides of bismuth, strontium, calcium and copper are mixed, the atomic ratios of the metals corresponding to a high-temperature superconductor, the mixture is mixed with an alkaline earth metal indate powder of the formula (Sr,Ca)In.sub.2 O.sub.4 and the mixture is heated for a prolonged period in the presence of oxygen. The presence of the indate promotes the development of a phase having a critical temperature of 110K.

Abstract: Black crystal compositions having the empirical composition Bi.sub.a Sr.sub.b Cu.sub.c O.sub.d are described where a+b+c=1, A=0.36-0.557, b=0.098-0.496, c=0.1-0.4 and d=approximately 1+a/2. These compositions have a superconducting transition temperature T.sub.c for superconductivity of greater than 20 K and contain a principal phase which crystallizes in the orthorhombic system. They can be prepared from the mixture of the oxides in the atomic ratio stated by heating to 700.degree.-1000.degree. C.