Abstract: It is an object to provide a product having a good crystal particle size distribution of a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal without using a physical method for particle classification. To that end, a method for manufacturing a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal is used, wherein the recrystallizing step comprising a first cooling process of cooling a saturated solution with a temperature of 60° C. to 90° C. obtained in the dissolving step at a cooling speed of T° C./hour until the solution temperature of the saturated solution becomes a temperature of the range of 35 to 50° C., and a second cooling process of cooling the solution at a cooling speed of [T?18]° C./hour to [T?1]° C./hour from the end of the first cooling process to the solution temperature becoming a temperature of 10 to 20° C.

Abstract: An object of the present invention is to provide a method for preventing concentration of a radioactive substance in a generated extraction residue in a method of producing tantalum, niobium, or a similar substance including collecting and refining a raw material containing the substances through a fluoridation process by use of a hydrofluoric acid-containing solution. The object can be attained by employing an ingredient-regulated raw material prepared from an ore or a concentrate and, as an additive, a substance insoluble to hydrofluoric acid or a mixed acid containing hydrofluoric acid as an essential component; or by increasing the amount of the extraction residue through addition of the insoluble substance to a solvent during the fluoridation process, to thereby reduce the relative radioactive substance content to an arbitrary value.

Abstract: It is an object to provide a product having a good crystal particle size distribution of a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal without using a physical method for particle classification. To that end, a method for manufacturing a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal is used, wherein the recrystallizing step comprising a first cooling process of cooling a saturated solution with a temperature of 60° C. to 90° C. obtained in the dissolving step at a cooling speed of T° C./hour until the solution temperature of the saturated solution becomes a temperature of the range of 35 to 50° C., and a second cooling process of cooling the solution at a cooling speed of [T-18]° C./hour to [T-1]° C./hour from the end of the first cooling process to the solution temperature becoming a temperature of 10 to 20° C.

Abstract: An object of the present invention is to provide a method for preventing concentration of a radioactive substance in a generated extraction residue in a method of producing tantalum, niobium, or a similar substance including collecting and refining a raw material containing the substances through a fluoridation process by use of a hydrofluoric acid-containing solution. The object can be attained by employing an ingredient-regulated raw material prepared from an ore or a concentrate and, as an additive, a substance insoluble to hydrofluoric acid or a mixed acid containing hydrofluoric acid as an essential component; or by increasing the amount of the extraction residue through addition of the insoluble substance to a solvent during the fluoridation process, to thereby reduce the relative radioactive substance content to an arbitrary value.

Abstract: A copper powder for electroconductive paints comprising copper particles and an organic zirconate compound which has been applied as a coating on the surfaces of said particles and an electroconductive paint composition obtained from the copper powder for electroconductive paints. The organic zirconate compounds used in the present invention are an organic zirconate compound (RO).sub.x --Zr--(OR').sub.4-x having an easily hydrolyzable organic group and an organic group which is hardly hydrolyzable and exhibits lipophilicity or a mixture of a zirconium acylate polymer and a higher carboxylic acid ester.

Abstract: A process for preparing a copper powder for electroconductive paints, which comprises adding to a dispersion bath of copper powder and a dispersion medium a mixture of a titanium acylate polymer and a higher carboxylic acid ester to form a film of the titanium acylate polymer and the higher caboxylic acid ester on the surfaces of the particles of said copper powder, and if necessary, removing the dispersion medium to obtain the copper powder for electroconductive paints. The copper powder thus obtained is coated on the surfaces of its particles with the titanium acylate polymer and the higher carboxylic acid ester.

Abstract: A process for preparing a copper powder for electroconductive paints, which comprises adding to a dispersion bath of copper powder and a dispersion medium a mixture of a titanium acylate polymer and a higher carboxylic acid ester to form a film of the titanium acylate polymer and the higher carboxylic acid ester on the surfaces of the particles of said copper powder, and if necessary, removing the dispersion medium to obtain the copper powder for electroconductive paints. The copper powder thus obtained is coated on the surfaces of its particles with the titanium acylate polymer and the higher carboxylic acid ester.