Abstract: A tungsten hexafluoride manufacturing method of the present invention includes a reaction step of reacting tungsten containing arsenic or an arsenic compound with a gas of a fluorine element-containing compound so as to obtain a mixture containing tungsten hexafluoride and a trivalent arsenic compound, and a distillation step of distilling and purifying the mixture so as to separate and remove a fraction containing the trivalent arsenic compound and to obtain tungsten hexafluoride.

Abstract: The present invention provides a method for producing trifluoromethanesulfonyl chloride. This method includes the step of reacting trifluoromethanesulfonic acid with phosphorous trichloride and chlorine. With this method, trifluoromethanesulfonyl chloride can be easily and highly selectively produced at high yield. The reaction may be carried out at about atmospheric pressure. Furthermore, the reaction may be carried out in the presence of phosphorus oxychloride either under a pressurized condition or at about atmospheric pressure.

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.