Magnesiumcarbonate with a molecular weight of 84.31. White granular powder. It decomposes at 350℃ and loses carbon dioxide at 900℃. Slightly soluble in cold water and slowly soluble in acid. Its trihydrate is a colorless needle-like crystal with a melting point of 1Chemicalbook65℃ and a relative density of 1.850. The pentahydrate is a white monoclinic crystal with a relative density of 1.73, which is decomposed by heating in air. The hydrate can be obtained by adding sodium carbonate while introducing carbon dioxide into magnesium salt solution, and then drying the hydrate below 50℃ to obtain anhydrous substance.