Fibrous brucite (FB) may release free radicals in water, display chemical activity in acid solution and has cytotoxicity in body liquid. In solution, FB can react with all substances that release ammonia ions and give off protons because of FB can ionize out hydroxyl in water. The existence of ferrous iron in FB usually results in concomitant occurrence of oxidation and reduction, finally forming compound ferric iron ammonia salts. So, the brucite dusts may react with and be dissolved partly in soluble ammonia salts of the human body and ammonia ions of body liquid. The increase in grain size and temperature is beneficial to the increase of dissolved magnesium in the balance system. High-concentration ammonia salts have a large dissolving capacity at high temperature. The total amount of Mg and Fe ions in the equilibrium solution depends on the solubility of resulting double salts. The reaction speed is decided by the speeds of ionization of ammonia salts and brucite together. NH4Cl (1.25 mol/L), (NH4)2SO4(0.5 mol/L) and NH4HSO4(1.25 mol/L) are the ammonia salts that can not only prevent Fe2+from being oxidized or precipitated but also cause brucite to be dissolved better at 40~80℃.