Calcium Carbonate 98% ECHEMI

Calcium carbonate is a white fine crystalline powder, tasteless, odorless. There are two forms, amorphous and crystalline. The crystalline form can be divided into orthorhombic system and hexagonal system (anhydrous calcium carbonate is colorless trapezoid crystal, and hexahydrate calcium carbonate is colorless monoclinal crystal , which are columnar or diamond shaped, and the density is 2.93g/cm3. The melting point is 1339 ° C (decomposed at 825-896.6 ° C), and the melting point is 1289 ° C at 10.7MPa. It is almost insoluble in water, soluble in water containing ammonium salts or ferric oxide, and insoluble in alcohols 
Structure of matter
Its crystal structure is orthogonal crystal system. Each calcium carbonate molecule consists of one carbon atom and three oxygen atoms, each of which is connected to a calcium ion. Calcium carbonate is composed of calcium ions forming ionic bonds with carbonate ions, which are composed of carbon-oxygen covalent bonds. The carbonate belongs to the sp2 hybrid, and the central carbon atom has three orbitals and one p orbital. According to the VSEPR model, it belongs to the AY3 type molecule, and its ideal VSEPR model is a planar triangle, with three C-O bonds in the molecule as a planar triangle. In addition, it has a 4-orbital 6-electron p-p large bond [6]. In the crystal, the calcium carbonate molecules are arranged in a layered structure parallel to the a and c axes. These layers are connected to each other by coplanar oxygen atoms and form a 3D network. This structure makes calcium carbonate with high stability and hardness.
Chemical properties

Calcium carbonate is the commodity name of limestone, a valuable resource with a wide range of uses, as mineral raw material. In the history of human civilization, limestone has been widely used because of its wide distribution in nature and easy access. As an important building material, limestone has a long mining history. In modern industry, limestone is the main raw material for the manufacture of cement, lime and calcium carbide, and an indispensable flux limestone in metallurgical industry. After ultra-fine grinding, high-quality limestone is widely used in the manufacture of paper, rubber, paint, coating, medicine, cosmetics, feed, sealing, bonding, polishing and other products. According to incomplete statistics, the total ratio of limestone consumed by cement production and construction stone, lime production, metallurgical flux, and ultra-fine calcium carbonate is 1∶3. Limestone is a non-renewable resource. With the continuous progress of science and technology and the development of nanotechnology, the application fields of limestone will be further broadened. 
1. Used in plastic production
Calcium carbonate is widely used in filling polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), acrylobutadiene styrene copolymer (ABS) and other resins. The addition of calcium carbonate to improve some properties of plastic products to expand its application scope has a certain role, in plastic processing they can reduce resin shrinkage, improve flow deformation, control viscosity. They can also:
(1) improve the dimensional stability of plastic products;
(2) improve the hardness and rigidity of plastic products;
(3) improve the processing performance of plastics;
(4) improve the heat resistance of plastic products;
(5) improve the astigmatism of plastic;
(6) can make the product have some special properties;
(7) reduce the cost of plastic products. 
2. Used in the food industry
It can be used as an additive in the food industry. For example, it can be used as a variety of feed additives with a calcium content of more than 55.6% and no harmful ingredients. It can be used as calcium supplement with an absorption rate of up to 39%, second only to calcium hydroxy acid. It is soluble in gastric acid and has become the most widely used calcium supplement in dosage form. [7]
3. Used in construction industry
Can be used as plastic factory, rubber factory, coating factory, waterproof material factory raw materials and internal and external wall painting. It has the characteristics of high purity, high whiteness, non-toxic, odorless, low fine oil quality and low hardness. Marble is also an important building material that can be used in the construction of houses.
4. Used in chemical manufacturing industry
350 mesh to 400 mesh can be used in the manufacture of gusset plate, water pipe, chemical industry. The whiteness is above 93 degrees. 400 to 600 mesh can be used in toothpaste paste, soap. The whiteness is above 94 degrees. 800 purpose can be used for rubber, cable, pvc, whiteness above 94 degrees. [7]
It can also be used to manufacture optical neodymium glass raw materials.
5. Used for fine ceramic materials
Calcium carbonate can be used to prepare high temperature stable, dielectric, low thermal conductivity, microporous and highly pure ceramic materials. For example, white conductors are widely used in the preparation of spark plugs, and important fine ceramic materials such as semiconductor materials, alumina and enamel pigments.
6. Use mineral fillers and abrasives
Industrial calcium carbonate can also be used as mineral fillers and abrasives. In the production of chemical and construction materials, calcium carbonate can replace some expensive materials, such as lead ore, talc and talc. In the abrasive, the particle surface of calcium carbonate can interact with the abrasive matrix to enhance the abrasion resistance and grinding efficiency of the abrasive to improve the efficiency and durability of the abrasive.
7. Use in nutritional supplements
The main component of most calcium tablets on the market is calcium carbonate. Calcium carbonate should be taken with meals [21]. Because calcium carbonate contains carbolic acid, it is easy to produce carbon dioxide in an acidic environment, so it is not suitable for those with poor gastric acid secretion or those who are using gastric acid inhibitors [22].