Hebei Messi Biology Co., Ltd. stated that reagent-grade magnesium carbonate is alkaline hydrated magnesium carbonate or normal hydrated magnesium carbonate. Due to different crystallization conditions, the product is divided into light and heavy. It is a trihydrate at room temperature. Reagent-grade magnesium carbonate is a white monoclinic crystal with a relative density of 2.254. It is slightly soluble in water, insoluble in ethanol, and can be dissolved and foamed by dilute acid. It foams and decomposes in acid to release carbon dioxide, and is heated and calcined to generate magnesium oxide and carbon dioxide. Odorless. Relative density 2.2. Melting point 350℃. It is stable in air and almost insoluble in water, but causes a slight alkaline reaction in water.
Application of magnesium carbonate in food additives: acidity regulator (PH regulator); alkaline agent; desiccant; color preservative; anti-caking agent; carrier; leavening agent; acidity regulator; free flow agent; flour treatment agent; nutritional supplement; PH regulator; processing aid; release agent; EEC approved for: table salt, powdered sugar, acidified cream, milk, ice cream, biscuits, waffles. Used to prepare chemical leavening agents. The residual amount in food should be ≤0.5% (Japan). Used to prevent salt from agglomerating and add 0.1% to 0.3%. It can also be used in industries such as toothpaste, medicine and cosmetics.
Preparation process of magnesium carbonate
Method 1: Mix magnesite (MgCO3) and coke and roast to obtain magnesium oxide. After adding water to make it muddy, CO2 is introduced to obtain magnesium bicarbonate. After filtering, the filtrate is heated to obtain basic carbonate precipitation.
Method 2: Heat dolomite with a low fire, only decompose magnesium carbonate and crush it, and react with water and CO2 at 5 to 6 atmospheres. Magnesium oxide becomes magnesium bicarbonate and dissolves, leaving calcium carbonate, which is filtered and heated to obtain.
Method 3: Dissolve equal amounts of crystalline magnesium sulfate and crystalline sodium carbonate in 10 times the amount of water, heat to 60 ℃ ~ 80 ℃ and mix thoroughly, and precipitate while generating CO2 gas. Filter out the precipitate, mix with hot water at 70 ℃ ~ 80 ℃, filter again, precipitate, and dry at 50 ℃ ~ 60 ℃ after sufficient washing.
Method 4: Prepare from brine after salt production. Add sulfuric acid to the brine, pass hydrogen, heat to remove bromine, then add sodium carbonate, stir, and react. At this time, basic magnesium carbonate precipitate is generated, filter, wash with water, and dry at above 50 ℃ to obtain precipitated magnesium carbonate (heavy magnesium carbonate).