For removing silica from high concentration medium after digestion of the diasporic bauxite by sub-molten salt,the research used calcium hydroferrocarbonate with the new desilication reagent.In the reaction,calcium carbonate,calcium hydroxide and calcium ferrite were by-product,therefore the reaction factors showed significant influence on the synthesis and disilicating efficiency.To explore the synthesis mechanism and optimize the reaction factors,the composition of the intermediate obtained from the synthesis reaction was investigated through the combination of FTIR,ICP-AES and desilication reaction.The FTIR and desilication reaction results revealed that calcium hydroferrocarbonate is metastable compound in solution,and the reaction temperature and reaction time have significant influence on the systhesis.With the temperature and reaction time increasing,the content of calcium hydroferrocarbonate in the composition first increased and then reduced.The optimal factors were:temperature of 30 ℃,reaction time of 16 hours,the liquid to solid mass ratio of 20 and rpm of 500 r·min-1.The crystal structure of calcium hydroferrocarbonate was investigated,and was found to be rhombohedral,including H2O bond,—OH bond and Fe—O bond.