magnesium carbonate trihydrate, also known as MgCO3, is a white, solid mineral with a density of 2.91 g/cm3. It is insoluble in water and only sparingly soluble in acetone or ammonia. It is a strong acid-forming compound and reacts with bases to form magnesium hydroxide, magnesium silicate, and magnesium oxide. It is a common ingredient in baking powders and is used to reduce the acidity of foods. Magnesium carbonate has a low boiling point and melting point, and tarnishes slightly in air.

It occurs naturally in the anhydrous salt magnesite (MgCO3) and in the di, tri, and pentahydrate minerals barringtonite, nesquehonite, and lansfordite. The anhydrous salt has a triclinic structure, while the dihydrate and trihydrate forms have monoclinic structures. Magnesium carbonate is the magnesium salt that reacts most rapidly with acids, and it has an unusually high decomposition temperature of 540 degC.

The present invention relates to a process for purifying sugar-containing aqueous juice by adding and mixing with the prelimed sugar juice reactive magnesium carbonate trihydrate in an amount sufficient to raise the pH value of the resulting prelimed sugar juice to about 10.0, agitating the resulting mixture until substantial decolorization is effected, and removing the precipitate formed. This process is advantageous because it can provide sugar juice with a low ph value and an acceptable color at a lower cost than that obtained by other processes, and also allows the resulting product to be easily filtrable. This method is particularly useful in the manufacture of cane sugar.