Abstract: A measurement sensitivity of an electro-optical element higher is made highly sensitive, and an optical-voltage sensor having a simple structure capable of being formed by directly laminating the highly sensitive electro-optical elements is provided.

Abstract: An optical-voltage sensor having a simple structure and being capable of being formed by directly laminating highly sensitive electro-optical elements is disclosed. The optical-voltage sensor includes a light source 1, a polarizer 2, a ¼ wavelength plate 3, an analyzer 5, and an O/E converting portion. Two electro-optical elements 4a, 4b are arranged adjacent to each other along a light transmitting direction between the ¼ wavelength plate 3 and analyzer 5. Transparent electrodes 7 are attached to front and back surfaces of each of the electro-optical elements 4a, 4b, and voltages having a magnitude equal to one another and a polarity opposite to one another are applied to the electro-optical elements 4a, 4b from a power supply 8a and a power supply 8b, respectively.

Abstract: A SF.sub.6 gas insulating electric apparatus usable as a circuit breaker, etc., containing a SF.sub.6 gas insulator and a resin insulator, both of which insulators are present in an atmosphere to be exposed to arcs, characterized by making at least the surface portion to be exposed to arcs of the resin insulator from a polymer containing nitrogen atoms or a polyolefin resin, and if necessary together with an inorganic filler powder, is excellent in both surface and inner arc resistance and can maintain breaking performance for a long period of time.

Abstract: Titanium minerals are concentrated by leaching with an acid leaching agent in the presence of a chelating agent, sulfonate surfactant or polyacrylamide surfactant, wherein the iron components are removed from the minerals.