Abstract: With the light burning powder refined liquid and ammonia as raw materials，the influence of impurity ions in steamed ammonia refining fluid on the magnesium hydroxide morphology was investigated.Cationic NH⁴⁺，Ca²⁺，and anion SO₄^2- were selected as the research objects to investigate their influences on the morphology and particle size of magnesium hydroxide.The products were characterized by scanning electron microscopy（SEM），X-ray diffraction（XRD），and laser par- ticle size analyzer.Results showed that NH⁴⁺ and Ca²⁺ little influenced on the performance of magnesium hydroxide product， and the SO₄^2-  had a great influence on the morphology and particle size of magnesium hydroxide product.BaCl₂ was used to remove SO₄^2- in the solution.The difference of the undesulphurized and desulphurized products was also compared with the product prepared with pure magnesium chloride.

Key words: light burning powder, ammonia, impurity ions, magnesium hydroxide