Abstract: The present invention provides method of producing a trivalent and tetravalent mixed vanadium compound having excellent solubility with sulfuric acid directly from a tetravalent or pentavalent vanadium compound by using a reducing agent,and a method of producing a vanadium electrolyte. For example, a vanadium compound mainly containing a pentavalent vanadium compound; sulfur and concentrated sulfuric acid in molar ratios with respect to (one mol of vanadium atom in the pentavalent vanadium compound) 0.35 to 0.4:1.2 to 1.9 are kneaded into paste form, and the paste-form mixture is calcined at a temperature of not less than 150° C. to less than 440° C. so that a trivalent and tetravalent mixed vanadium compound is obtained, and a redox flow battery-use vanadium electrolyte is obtained by dissolving the trivalent and tetravalent mixed vanadium compound in a sulfuric acid solution.

Abstract: The present invention discloses a tertiary non-linear optical material comprising a quinone derivative expressed by any one of the general formulas: ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are as defined above, or the formula: ##STR2## The tertiary non-linear material enables the co-existence of large tertiary non-linear optical susceptibility and high-speed response.

Abstract: A method for producing a crystal film of an organic compound from a molten liquid or solution of the organic compound on a substrate or between a pair of substrates, the substrate or at least one of the pair of substrates having on a part of the surface thereof a three-dimensional geometrical structure capable of controlling the direction of the crystal growth of the organic compound, and the other part of the surface thereof than the part having a three-dimensional geometrical structure being smooth. The resulting crystal film comprises a sufficiently large single crystal for application to a practical element with its orientation controlled in an arbitrarily selected direction.

Abstract: A fiber type wavelength converter comprising a cladding made of a thin glass tube an inner wall of which is coated with a coupling agent, and a core which is contained in the cladding and made of a single crystal of methyl 4-hydroxybenzoate, which can convert a fundamental wave to a second harmonic effectively.