(JP8148177-A)      Prodn. of an electrolytic soln. contg. vanadium as positive and negative electrode active materials is claimed. The solns. are suitable for a redox battery, and the process comprises: (a) a purificn. step in which a vanadium cpd. contg. impurities selected from vanadium pentoxide and ammonium metavanadate is dissolved in a solvent under an alkaline or neutral condition, a polyvanadate cpd. is pptd. by thermal polymerisation of vanadium ions under an acidic condition, and the polyvanadate cpd. is isolated from the soln. contg. impurities; (b) a de-ammoniation step in which a part of the polyvanadate cpd. prepd. in the purificn. is baked at 400-690C in an inert or oxidising gas atmos. so as to remove ammonium ions; (c) a trivalent vanadium cpd. forming step in which a trivalent vanadium cpd. is formed by treating another part of the polyvanadate cpd. prepd. in the purificn. under a reductive atmos.; (d) a V3+ electrolytic soln. forming step in which a trivalent vanadium electrolytic soln. is formed by dissolving the trivalent vanadium cpd. in an acid soln.; and (e) a V4+/V3+ mixed electrolytic soln. forming step in which vanadium pentoxide obtd. in the de-ammoniation step and a part of the trivalent vanadium cpd. obtd. in the V3+ electrolytic soln. forming step are reacted by mixing so that mixed electrolytic solns. having various mixing ratios of V4+ and V3+ are formed.    A further process for the prodn. of the electrolytic soln. is also claimed.    USE -   Used for a redox battery.    ADVANTAGE -   The process economically produces high purity vanadium electrolytic solns. not effecting the deterioration of the ion exchange membrane. The electrolytic soln. can be easily produced from low purity vanadium raw materials which are inexpensive and can be steadily supplied.    (JP10114525-A)      Prodn. of an electrolytic soln. contg. vanadium as positive and negative electrode active materials is claimed. The solns. are suitable for a redox battery, and the process comprises: (a) a purificn. step in which a vanadium cpd. contg. impurities selected from vanadium pentoxide and ammonium metavanadate is dissolved in a solvent under an alkaline or neutral condition, a polyvanadate cpd. is pptd. by thermal polymerisation of vanadium ions under an acidic condition, and the polyvanadate cpd. is isolated from the soln. contg. impurities; (b) a de-ammoniation step in which a part of the polyvanadate cpd. prepd. in the purificn. is baked at 400-690C in an inert or oxidising gas atmos. so as to remove ammonium ions; (c) a trivalent vanadium cpd. forming step in which a trivalent vanadium cpd. is formed by treating another part of the polyvanadate cpd. prepd. in the purificn. under a reductive atmos.; (d) a V3+ electrolytic soln. forming step in which a trivalent vanadium electrolytic soln. is formed by dissolving the trivalent vanadium cpd. in an acid soln.; and (e) a V4+/V3+ mixed electrolytic soln. forming step in which vanadium pentoxide obtd. in the de-ammoniation step and a part of the trivalent vanadium cpd. obtd. in the V3+ electrolytic soln. forming step are reacted by mixing so that mixed electrolytic solns. having various mixing ratios of V4+ and V3+ are formed.    A further process for the prodn. of the electrolytic soln. is also claimed.    USE -   Used for a redox battery.    ADVANTAGE -   The process economically produces high purity vanadium electrolytic solns. not effecting the deterioration of the ion exchange membrane. The electrolytic soln. can be easily produced from low purity vanadium raw materials which are inexpensive and can be steadily supplied.    (JP3085634-B2)      Prodn. of an electrolytic soln. contg. vanadium as positive and negative electrode active materials is claimed. The solns. are suitable for a redox battery, and the process comprises: (a) a purificn. step in which a vanadium cpd. contg. impurities selected from vanadium pentoxide and ammonium metavanadate is dissolved in a solvent under an alkaline or neutral condition, a polyvanadate cpd. is pptd. by thermal polymerisation of vanadium ions under an acidic condition, and the polyvanadate cpd. is isolated from the soln. contg. impurities; (b) a de-ammoniation step in which a part of the polyvanadate cpd. prepd. in the purificn. is baked at 400-690C in an inert or oxidising gas atmos. so as to remove ammonium ions; (c) a trivalent vanadium cpd. forming step in which a trivalent vanadium cpd. is formed by treating another part of the polyvanadate cpd. prepd. in the purificn. under a reductive atmos.; (d) a V3+ electrolytic soln. forming step in which a trivalent vanadium electrolytic soln. is formed by dissolving the trivalent vanadium cpd. in an acid soln.; and (e) a V4+/V3+ mixed electrolytic soln. forming step in which vanadium pentoxide obtd. in the de-ammoniation step and a part of the trivalent vanadium cpd. obtd. in the V3+ electrolytic soln. forming step are reacted by mixing so that mixed electrolytic solns. having various mixing ratios of V4+ and V3+ are formed.    A further process for the prodn. of the electrolytic soln. is also claimed.    USE -   Used for a redox battery.    ADVANTAGE -   The process economically produces high purity vanadium electrolytic solns. not effecting the deterioration of the ion exchange membrane. The electrolytic soln. can be easily produced from low purity vanadium raw materials which are inexpensive and can be steadily supplied.