Abstract: The reaction mechanism and optimization process conditions of producing basic magnesium carbonate by twice-carbonization process from light-burned dolomite powder under normal pressure are discussed. The research results indicate that 60um long -2um diameter rod-like basic magnesium hydroxide containing 42% magnesium oxide and 0.07% calcium oxide and having a brightness of 97.3% can be produced at the following conditions: stop-point pH values for the primary and secondary carbonization being pH₁＝10 and pH₂＝9, carbonizing CO₂ partial pressure being Pco₂1 =0.03 MPa and Pco₂2=0.1 MPa, carbonizing solution concentration of 25 g/L and agitation speed of 400 r/min.

Key words: Light-burned dolomite, Twice-carbonization, Basic magnesium carbonate