Abstract: The capability of EDTA disodium salt(CDTA) solution as a second fixing solution to dissolve CaWO₄ core/AgX shell microcrystal emulsion was studied in this paper. The results showed that EDTA disodium salt (CDTA) solution is available for dissolving CaWO₄ in the range of pH 5~12, CaWO₄ can be fully dissolved. The capability of EDTA disodium salt(CDTA) solution to dissolve CaWO₄ core/AgX shell microcrystal emulsion is affected by temperature, pH value and concentration of EDTA disodium salt(CDTA) solution. In comparison with CDTA, the change of concentration of EDTA disodium salt solution makes a greater effect on the fixing capability of EDTA disodium salt than that of CDTA. Under the same conditions of temperature、concentration and pH value, the complexing speed of EDTA disodium salt solution with CaWO₄ is faster than that of CDTA solution.

Key words: CaWO₄ core/AgX shell microcrystal emulsion, second fixing, EDTA disodium salt(CDTA)