Calcium carbonate

Synonyms: Calcium carbonate, Carbonic acid calcium salt, Limestone, Calcite, Aragonite, Chalk, Marble, Precipitated calcium carbonate (PCC), Ground calcium carbonate (GCC)

Calcium carbonate is an inorganic salt with the formula CaCO₃, consisting of calcium ions (Ca²⁺) and carbonate ions (CO₃^2-) arranged in a crystal lattice. It occurs naturally in three anhydrous polymorphs—calcite, aragonite, and vaterite—with calcite being the most thermodynamically stable under ambient conditions. The carbonate ion is planar with D_3h symmetry, and the calcium ions are coordinated to six oxygen atoms in a distorted octahedral geometry. This simple yet versatile structure underpins its widespread industrial and pharmaceutical utility.

Commercially, calcium carbonate is derived from limestone, marble, or chalk deposits (ground calcium carbonate, GCC) or produced synthetically via carbonation of calcium hydroxide (precipitated calcium carbonate, PCC). It is available in various grades, including technical, food, and pharmaceutical (USP/EP/BP) grades, each with specific purity and particle size distributions. The pharmaceutical grade is typically a fine, white powder with high chemical purity, meeting stringent limits for heavy metals and microbial contamination.

In the pharmaceutical and nutraceutical industries, calcium carbonate serves as a calcium supplement, antacid, and excipient. As a supplement, it provides essential calcium for bone health and is often combined with vitamin D to enhance absorption. As an antacid, it neutralizes gastric acid, offering rapid relief from heartburn and indigestion. In tablet formulations, it acts as a diluent, binder, or coating agent, contributing to tablet hardness and disintegration. Beyond pharma, it is a key raw material in the production of glass, ceramics, paints, plastics, and paper, where it functions as a filler, extender, or whitening agent.

Chemical Structure & Properties

Calcium carbonate is an ionic compound that crystallizes in three polymorphs: calcite (trigonal), aragonite (orthorhombic), and vaterite (hexagonal). Calcite is the most common and stable form, characterized by a rhombohedral lattice. The compound has a molecular weight of 100.09 g/mol, a density of 2.71 g/cm³ (calcite), and a Mohs hardness of 3. It is practically insoluble in water (solubility product K_sp = 3.3 × 10^-9 at 25 °C) but dissolves readily in dilute acids, releasing carbon dioxide. Upon heating above 825 °C, it decomposes to calcium oxide and carbon dioxide. Its refractive index is 1.49–1.66, and it exhibits birefringence. These properties make it suitable for applications requiring thermal stability, acid reactivity, and optical clarity.

Механизм действия

• Antacid activity: Calcium carbonate neutralizes gastric acid (HCl) to form calcium chloride, water, and carbon dioxide, raising gastric pH and relieving symptoms of hyperacidity.
• Calcium supplementation: It provides bioavailable calcium, which is absorbed in the small intestine via active transport (calbindin-mediated) and passive diffusion, supporting bone mineralization and neuromuscular function.
• Phosphate binding: In patients with chronic kidney disease, calcium carbonate binds dietary phosphate in the gastrointestinal tract, forming insoluble calcium phosphate complexes that are excreted, thereby reducing serum phosphate levels.
• Excipient functionality: As a filler, it increases tablet mass and improves compressibility; as a coating agent, it provides a smooth, white opaque film.

Quality Specifications

Supply & Documentation

• Capacity: 500 metric tons per month
• Срок выполнения заказа: 3–5 рабочих дней (товары, имеющиеся в наличии)
• Documentation: COA, MSDS, TDS, GMP, ISO 9001, Kosher, Halal
• Packaging: 25 kg multi-wall paper bags, 500 kg / 1000 kg jumbo bags, or as per customer request

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