Abstract: A fluorite with excellent laser durability is provided by devising a heat-treatment method for CaF2 crystal. A fluorite production method is proposed, wherein heat-treatment is carried out by providing, through compartment walls in the periphery of a fluorite crystal, a fluoride gas trap layer containing a fluoride gas-adsorbing material.

Abstract: A fluorite with excellent laser durability is provided by devising a heat-treatment method for CaF2 crystal. A fluorite production method is proposed, wherein heat-treatment is carried out by providing, through compartment walls in the periphery of a fluorite crystal, a fluoride gas trap layer containing a fluoride gas-adsorbing material.

Abstract: The present invention provides a discharge lamp lighting system in which a discharge lamp is lighted by a commercial power source without using a choke transformer, electric power can be saved, and, in order to prevent a bad influence of high harmonic waves generated from the discharge lamp upon other electronic equipment, the impedance ratio resonating with the third high harmonic wave component of the power source is established between a capacitor and a choke coil provided between the discharge lamp and an alternate current power source to facilitate resonance of the third high harmonic wave component, and, when a starting lighting circuit is temporarily turned ON, the discharge lamp is lighted.

Abstract: Red phosphorus flame retardants for synthetic resin are produced by a method comprising the steps of heating yellow phosphorus at temperatures of 250.degree. to 600.degree. C. to effect a partial conversion of yellow phosphorus to red phosphorus; removing unconverted yellow phosphorus; and coating particles of the resulting red phosphorus with at least one of thermosetting resin and metal hydroxide. The thus obtained red phosphorus flame retardants are very stable because of significantly improved heat resistance, water resistance and weatherability and thus can provide nonflammable resinous compositions which can be used for long period of time. The nonflammable composition consists essentially of 100 parts by weight of polyolefine resin, 20 to 200 parts by weight of hydrated inorganic filler and 0.1 to 30 parts by weight of the coated red phosphorus flame retardant.

Abstract: A flame retardant comprising of spherical red phosphorus free of pulverized face which is directly produced in the form of fine powder by conversion of yellow phosphorus, without pulverizing process. The red phosphorus characterized by its surface state and shape entirely different from any prior pulverized red phosphorus has not only a high flame retarding ability, but also a superior combination of chemical and physical properties, particularly with regard to corrosion resistance, moisture resistance, mechanical strength and dielectric properties which make it highly valuable and useful as a flame retardant for various nonflammable resinous compositions used in electric articles including electronic parts, machines, automobiles and buildings. The flame retardant is desirably coated with thermosetting rein and/or hydroxide of aluminum and/or zinc, thereby greatly improved in its stability.

Abstract: A flame retardant comprising of spherical red phosphorus free of pulverized face which is directly produced in the form of fine powder by conversion of yellow phosphorus, without pulverizing process. The red phosphorus characterized by its surface state and shape entirely different from any prior pulverized red phosphorus has not only a high flame retarding ability, but also a superior combination of chemical and physical properties, particularly with regard to corrosion resistance, moisture resistance, mechanical strength and dielectric properties which make it highly valuable and useful as a flame retardant for various nonflammable resinous compositions used in electric articles including electronic parts, machines, automobiles and buildings. The flame retardant is desirably coated with thermosetting resin and/or hydroxide of aluminum and/or zinc, thereby greatly improved in its stability.