The method for producing dichlorimium trioxide and alkali dichromate includes the following steps: calcining ammonium chromate alkali metal double salt at 650-1200 deg.C for 0.5-3 hr., then dissolving the calcined product in water and making solid-liquid separation, collecting precipitate dichromium trioxide product; then evaporating and concentrating mother liquor according to conventional method, cooling and crystallizing, and making solid-liquid separation to separate the alkali dichromate as product from alkali chromate as by-product. Said alkali chromate can be returned, and can be utilized circularly. Said dichronium trioxide contains no sulfur, can be used as high-grade raw material for smelting metal chromium, also can be used as pigment and grinding material. |