Abstract: The concentration of molecular fluorine in a mixed gas such as an excimer laser gas can be determined easily, quickly and accurately by passing the mixed gas through a column packed with an alkali metal or alkaline earth metal compound which has no halogen atom and reacts with fluorine to form a solid fluoride together with molecular oxygen and/or carbon dioxide and measuring the concentration of oxygen or carbon dioxide in the fluorine-free gas flowed out of the packed column. If the mixed gas initially contains molecular oxygen or carbon dioxide, its concentration is measured separately after fixing fluorine in another column packed with an element which forms a fluoride. This analyzing method can be used in a feedback control system for controlling the concentration of fluorine in an excimer laser gas during operation of the laser to thereby stabilize the laser output power.

Abstract: The concentration of molecular fluorine in a mixed gas such as an excimer laser gas can be determined easily, quickly and accurately by passing the mixed gas through a column packed with an alakli metal or alkaline earth metal compound which has no halogen atom and reacts with fluorine to form a solid fluoride together with molecular oxygen and/or carbon dioxide and measuring the concentration of oxygen or carbon dioxide in the fluorine-free gas flowed out of the packed column. If the mixed gas initially contains molecular oxygen or carbon dioxide, its concentration is measured separately after fixing fluorine in another column packed with an element which forms a fluoride. This analyzing method can be used in a feedback control system for controlling the concentration of fluorine in an excimer laser gas during operation of the laser to thereby stabilize the laser output power.

Abstract: (CF.sub.3 SO.sub.2).sub.2 O is formed by reaction of CF.sub.3 SO.sub.3 H with P.sub.2 O.sub.5 and taken out of the reaction system by distillation, but the residue of the distillation contains a considerable amount of unreacted CF.sub.3 SO.sub.3 H. From the residue unreacted by adding water or a phosphoric acid solution, preferably the latter, to the residue to obtain a fluidic mixture containing an adequate amount of water and subjecting the mixture to distillation, preferably under reduced pressure at temperatures ranging from 180.degree. to 280.degree. C. It is possible to form additional CF.sub.3 SO.sub.3 H during the recovery process by adding a metal salt of CF.sub.3 SO.sub.3 H to the aformentioned mixture since the metal salt is decomposed by phosphoric acid contained in the mixture.

Abstract: A laser gas used in a rare gas fluoride excimer laser is efficiently refined with little loss of the principal rare gas such as Ar, Kr or Xe by sequential contact of the laser gas first with a reactive metal, e.g. Si or Fe, for conversion of the fluorine source gas such as F.sub.2 or NF.sub.3 to a metal fluoride, then with a solid alkaline compound, e.g. Ca(OH).sub.2, for conversion of gaseous fluorides to solid metal fluorides, next with zeolite which is adsorbent of most of the remaining impurities and finally with an alkaline metal, e.g. Ca or Na, for decomposition of CF.sub.4 to form a solid metal fluoride and carbon. CF.sub.4 is formed during operation of the excimer laser by reaction of fluorine with a fluororesin used as electrical insulator in the laser apparatus, and accumulation of CF.sub.4 in the laser gas caused significal lowering of the laser output power.

Abstract: A fluorocarbon carboxylic acid Rf(COOH).sub.m (Rf is C.sub.1 -C.sub.10 perfluoroalkyl group, m is 1 or 2) is prepared by the steps of hydrolyzing Rf(COF).sub.m with water to obtain an acidic solution, neutralizing the acidic solution with aqueous solution of KOH to form Rf(COOK).sub.m, precipitating and separating Rf(COOK).sub.m from the solution and converting Rf(COOK).sub.m into Rf(COOH).sub.m by acid decomposition. The content of free fluorine can extremely be reduced by treating Rf(COOK).sub.m with sulfuric acid and silica. The mother liquor is recycled after removing KF by treatment with a metal hydroxide and replenishing with KOH. In preparing a fluorocarbon sulfonic acid RfSO.sub.3 H (Rf is C.sub.1 -C.sub.3 perfluoroalkyl group) in substantially the same way, RfSO.sub.3 K is formed in aqueous solution of KOH by bringing gaseous RfSO.sub.2 F into contact with the KOH solution under normal pressure, while controlling the feed rate of RfSO.sub.

Abstract: In preparing a fluoroalkylsulfonate RfSO.sub.3 M, where Rf is a perfluoroalkyl gruop having not more than 6 carbon atoms and M is an alkali metal, by neutralization reaction between a fluoroalkylsulfonic acid RfSO.sub.3 H and an alkali metal carbonate or hydroxide, the reaction is carried out under acidic conditions such that at the end of the reaction pH of the reaction liquid is lower than 6, and preferably not higher than 3. By so maintaining the reaction liquid acidic, the obtained RfSO.sub.3 M becomes very low in the concentrations of anionic impurities such as free fluorine, free chlorine and carbonate radical and, besides becomes low in moisture absorbency.

Abstract: A fluoropolymer, e.g. polytetrafluoroethylene, is easily and efficiently converted into a lower molecular weight polymer in the form of a fine powder by subjecting the fluoropolymer to contact reaction with a gas comprising molecular fluorine or a suitable fluoride such as nitrogen trifluoride or xenon difluoride at a temperature between the melting temperature of the fluoropolymer and 600.degree. C., extracting a hot reaction gas produced by the contact reaction from the reactor and cooling the extracted reaction gas to a temperature not high than 100.degree. C. to thereby precipitate the molecular weight reduced fluoropolymer contained in the hot reaction gas as vapor.

Abstract: In forming a coating film of a fluororesin, e.g. polytetrafluoroethylene, on a metallic or nonmetallic surface by a physical vapor deposition technique, problems attributed to the necessity of intensely heating or bombarding the fluororesin as the evaporating source or target material are solved by using a molecular weight reduced fluororesin not higher than 5000 in molecular weight. It is best to use a low molecular weight fluororesin powder obtained by heating a high molecular weight fluororesin in presence of a fluorine source and precipitating the molecular weight reduced polymer from the reaction gas.

Abstract: A laser gas used in a rare gas halide excimer laser is efficiently refined with little loss of the essential rare gas such as Kr, Ar or Xe by contact of the laser gas with a solid alkaline compound, e.g. Ca(OH).sub.2, for conversion of acidic impurities and also the halogen source gas such as F.sub.2 or HCl into solid metal halides and contact of the remaining gas with zeolite which is adsorbent of the remaining impurities. When the halogen source gas comprises a highly oxidizing fluorine matter the laser gas is first brought into contact with a reactive metal, e.g. Si or Fe, to convert the oxidizing fluorine matter into metal fluorides to thereby prevent formation of O.sub.2, which is obstructive to the laser operation, by reaction of the oxidizing matter with the alkaline compound.

Abstract: A fluorine-containing high polymer, e.g. polytetrafluoroethylene, can easily and efficiently be converted into a wax-like lower molecular weight polymer by contact reaction of the high polymer with a gas comprising a fluorinating agent, which is selected from molecular fluorine, nitrogen-fluorine compounds represented by NF.sub.3, halogen fluorides represented by ClF.sub.3 and fluorides of rare gas elements represented by XeF.sub.2, at a temperature in the range from 250.degree. to 550.degree. C.

Abstract: NF.sub.3 is prepared with good yields by reaction between fluorine gas and an ammonium complex of a metal fluoride, such as (NH.sub.4).sub.3 AlF.sub.6, in solid phase. The metal flouride ammonium complex may be one additionally containing an alkali metal, such as (NH.sub.4).sub.2 NaAlF.sub.6. The gas-solid reaction is carried out preferably at temperatures above 80.degree. C. and at relatively low partial pressures of fluorine in the gas phase of the reaction system, so that the reaction is easy to control.

Abstract: A method and apparatus for preparation of a graphite fluoride such as (CF).sub.n or (C.sub.2 F).sub.n by heterogeneous contact reaction between a carbon material such as graphite or petroleum coke and fluorine gas at about 200.degree.-550.degree. C. The carbon material in the form of small pieces such as granules or powder particles is kept in a holder having a number of openings so as to form a carbon material layer in the holder, which is placed in a reactor so as to leave gas passages around the holder. With heating, fluorine gas is forcibly passed through the gas passages without agitating the carbon material in the holder. The openings of the holder are shaped and arranged such that the fluorine gas permeates through the carbon material layer in the holder. For example, the holder is an open-type box made of either a wire screen or a perforated metal plate, or a conveyor belt made of a wire screen.

Abstract: The use of an isotropic carbon block having an anisotropy of not more than 1.2 in terms of an anisotropic ratio of specific resistance as an anode in the production of fluorine by the electrolysis of an electrolyte comprising a mixed molten salt system of potassium fluoride and hydrogen fluoride has been found to be extremely useful for attaining increase in critical current density so that occurrence of the unfavorable anode effect can be effectively prevented. With such an isotropic carbon block anode, even if the anode effect occurs, the electrolysis can be stably continued again by lowering the potential of the electrode. Further, the incorporation of a fluoride into the isotropic carbon block anode and/or the addition of a fluoride into the electrolyte is effective for further increasing critical current density.

Abstract: Crude sodium hexafluorosilicate containing gypsum as a principal impurity can be refined economically with a minimized loss of fluorine by first making the crude fluorosilicate in the form of an aqueous slurry react with an alkali metal compound such as sodium carbonate or sodium hydroxide to form a soluble sulfate, and then treating the solid component of the reaction product with an acid solution in the presence of sodium ion, preferably at elevated temperatures near boiling point, to form a soluble calcium salt and crystallize sodium hexafluorosilicate. Sea water may be used both as the aqueous medium for the slurry in the first step and as the source of the sodium ions in the second step.

Abstract: Ammonium tetrafluoroaluminate particles having an average particle size above 50.mu. are reacted with an aluminum compound such as aluminum hydroxide or oxide first at a temperature of 250.degree. C to 300.degree. C and then at a temperature of 350.degree. to 500.degree. C to form crystalline particles of anhydrous aluminum fluoride (II) with an average particle size almost corresponding to the starting ammonium tetrafluoroaluminate. The heating of the crystalline particles to a temperature above 550.degree. C results in formation of aluminum fluoride (I) with a large average particle size.

Abstract: A process for preparing fluorine-rich organic compounds containing one or two carbon atoms from organic fluoro compounds of lower fluorine content in which starting partially or completely halogenated fluoro carbon compounds having at least one halogen atom other than fluorine, e.g., CHCl.sub.2 F, CHClF.sub.2, CCl.sub.2 F.sub.2, CCl.sub.3 F, C.sub.2 Cl.sub.3 F.sub.3, C.sub.2 Cl.sub.2 F.sub.4 and C.sub.2 Cl.sub.4 F.sub.2, are contacted under disproportionation conditions with a catalyst system of a specific type which comprises 0.1 - 5% by weight, as metal, of a nickel(II) halide, titanium(III) chloride or titanium(III) fluoride and a balance of an aluminum compound such as activated alumina, silica, alumina or aluminum fluoride.

Abstract: A process for producing sodium fluoride from sodium silicofluoride in which sodium silicofluoride is added to an ammonium fluoride solution for double decomposition reaction to obtain a slurry containing sodium fluoride as crystals and ammonium silicofluoride in dissolved form, and the solution from which the sodium fluoride crystals have been removed is added with ammonia to decompose the ammonium silicofluoride into silica and ammonium fluoride. The ammonium fluoride obtained by the decomposition is recycled to the double decomposition step. Alternatively, the ammonium fluoride is reacted with a sodium salt for recovery as sodium fluoride.

Abstract: An inorganic acid typified by H.sub.2 SO.sub.4 is added to an aqueous slurry of (NH.sub.4).sub.3 AlF.sub.6 and either Al(OH).sub.3 or Al.sub.2 O.sub.3, and the resulting mixture is kept for a while under the atmospheric pressure at or somewhat above room temperature. The acid is added preferably in such an amount that the pH of the slurry after completion of the reaction is 4 to 7.