Abstract: As to a reactor which is used in a process for producing hydrogen fluoride through a reaction of fluorite with sulfuric acid, and which comprises means for applying a shearing force to a content therein between the means and an inner surface thereof, a metal material is used for at least a portion of a part of the means which part is opposed to the inner surface, the metal material comprising tungsten carbide and a material comprising at least one element, or an alloy comprising two or more elements, selected from the group consisting of nickel, chromium, cobalt, iron, tungsten and carbon, the metal material comprising 30 to 90% by weight of tungsten carbide. Thereby, it becomes possible to reduce the wear of an edge of the means for applying the shearing force to the content (the reaction mixture) between the means and the inner surface.

Abstract: A method of managing audio parameter of application software according to the present invention is a method of managing audio parameter of application software used on the operating system, wherein at start of the application software, a starting audio parameter set in said operating system is stored, and whatever the starting audio parameter may be, audio data playback function is performed according to an exiting audio parameter when the application software was exited last time; and at exit of the application software, audio parameter at this time is stored as the exiting audio parameter of the application software and setting is switched from the exiting audio parameter to the starting audio parameter and audio data playback function is performed according to the starting audio parameter.

Abstract: As to a reactor which is used in a process for producing hydrogen fluoride through a reaction of fluorite with sulfuric acid, and which comprises means for applying a shearing force to a content therein between the means and an inner surface thereof, a metal material is used for at least a portion of a part of the means which part is opposed to the inner surface, the metal material comprising tungsten carbide and a material comprising at least one element, or an alloy comprising two or more elements, selected from the group consisting of nickel, chromium, cobalt, iron, tungsten and carbon, the metal material comprising 30 to 90% by weight of tungsten carbide. Thereby, it becomes possible to reduce the wear of an edge of the means for applying the shearing force to the content (the reaction mixture) between the means and the inner surface.

Abstract: A method of quickly and safely determining the component concentrations of a three-component mixture comprising substantially sulfuric acid, hydrogen fluoride and water, which comprises measuring at least one set of three physical quantities of (1) temperature, (2) ultrasonic wave propagation velocity and (3) electric conductivity or viscosity of the three-component mixture and converting the obtained values to the component concentrations on the basis of a working curve representing the relationship between each component concentration of the three-component mixture and the three physical quantities; and a method of continuous production of hydrogen fluoride for controlling a water concentration in the reaction system by using this method.