Calcium carbonate (CaCO3). Lime and limestone are large quantities of materials used in construction materials and industries. Limestone can be directly processed into stone and fired into lime. Quicklime CaO absorption of moisture or water becomes hydrated lime and hydrated lime was mostly the Ca (OH) 2, can be called the calcium hydroxide, hydrated lime through into lime, lime putty, etc., used as coating material and tile adhesive.
Calcium carbonate is a compound, the chemical formula is CaCO3. CAS number 34-471-1. It is a common material on earth and can be found in rocks. The main components of the back shell and snail shell. It is found in nature with calcite and calcite. Calcite is a trigonal crystal, hexagon crystal, pure calcite is colorless and transparent, generally white, with 56% CaO, 44% CO2, 2.715 g/cm3, mohs hardness is 3, and the property is relatively crisp. The stone belongs to the oblique square strain, the rhombic crystal, which is grey or white, with a density of 2.94 g/cm3, and the mohs hardness is 3.5-4, and the properties are dense. The crystallization of calcite in the physical properties of limestone is very important. Dense limestone exhibits high porosity of fine grained crystal structure with high strength. The density of limestone is about 2.65~2.80 g/cm3, the dolomite limestone is 2.70-2.90 g/cm3, and the dolomite is 2.85-2.95 g/cm3. Volume density depends on porosity.
Limestone thermal expansion: there is data shows, the limestone under 800 ℃, within the scope of the micro crystal limestone of the average thermal expansion coefficient is (4.5 ~ 5.0 * 10 ^ (6) / ℃, while the coarse crystal increases to 10.1 * 10 ^ (6) / ℃. The heating experiment of limestone is very important in lime production. In the limestone decomposition under 800 ℃ limestone expansion of crystallization in the body, forming crack in the highly crystalline limestone, and the crystal bigger by heat into powder by rupture, is very good for crystal growth, contains a lot of dense calcite limestone powder is serious.
The main chemical properties of limestone, calcium carbonate, are decomposed into calcium oxide and carbon dioxide at higher temperatures, with the following chemical properties.
L) chemical resistance
In addition to acid, many erosive substances do not erode or can only slowly erode limestone.
2) anti-acid properties
The limestone reacts with all the strong acids, producing calcium salts and releasing carbon dioxide, and the rate of reaction depends on the impurities in the limestone and the size of their crystals. The higher the impurity content, the larger the crystal and the smaller the reaction speed. Dolomite reacts slowly to limestone. Dolomite and limestone methods: with 10% hydrochloric acid drops on the dolomite with a small amount of air bubbles, drops are tasteless bubble violently in the limestone, the gas can make the clarification of limewater turbid.
3) properties of various gases
Chlorine and hydrogen chloride in the dry bath state and normal temperature and CaCO3, reaction very slow, it was not until 600 ℃ after began to accelerate, CaCl2 is generated; There was no significant effect on CaCO3 either in gaseous or liquid state at ambient temperature. And nitrogen dioxide (NO2) at 15 ℃ with CaCO3 reaction between Ca (NO3) 2, NO and CO2.
Limestone is mainly formed in the shallow sea. Limestone can be divided into granule limestone (water transport and deposition formation). Biological skeleton limestone and chemical, biochemical limestone. The structure can be divided into bamboo-leaf limestone, limestone, blocky limestone and so on. The main chemical composition of limestone is the ablation of calcium carbonate. Therefore, the limestone and karst caves are formed in the limestone areas, which are called karst topography.
Limestone usually contains some dolomite and clay minerals, which are called mudstone when the content of clay minerals reaches 25%~ 50%. The content of dolomite is 25%~ 50%, which is called dolomite limestone. The limestone distribution is quite extensive and the lithology is homogeneous and easy to be mined. It is a widely used building material.
The limestone mainly consists of calcium carbonate, which can dissolve in water containing carbon dioxide. Normally a liter of water containing carbon dioxide can dissolve about 50 mg of calcium carbonate.
According to a survey by geologists in the guilin area, the water in the area can dissolve each year and erode the surface of the limestone with a thin layer of fingernails. Don't look at the annual corrosion, but the history of earth development is extremely long. It was about 3 million years ago, in the most recent geological period, the quaternary. Even this slow rate of dissolution can dissolve 900 meters in 3 million years. The solitary peak of guilin is only a hundred and two meters high, and the maximum height of the common karst is only a few tens of meters. But also not have limestone can form the landform, but need to have a large area, big thickness, geological pure limestone, also requires a warm and humid climate conditions is likely to develop into such a perfect landscape, formed as the beautiful natural scenery.