calcium sulphate
White monoclinic crystal or crystalline powder. No taste. It is hygroscopic. 1 molecular crystal water is lost at 128℃, and all of it is lost at 163℃. Soluble in acid, sodium thiosulfate and ammonium salt solution, soluble in 400 parts of water, less soluble in hot water, extremely slow soluble in glycerol, almost insoluble in ethanol and most organic solvents.
Use of calcium sulfate
It can be used in building materials, heat insulation materials, coatings, reinforcing materials, etc. Used in paper industry, it can replace part or most of paper pulp. Length-diameter ratio ≤50 can be used as high-grade filler of paper, which can greatly improve paper output, reduce wood consumption, protect the environment and reduce wastewater pollution.
It can be used as reinforcing material in chemical industry, and anhydrous sulfuric acid whisker can be used for plastic granulation to enhance the strength and high temperature resistance of plastic particles and reduce the cost. In the production of PVC, polyethylene, propylene, polystyrene and other plastics, it can enhance the performance of products in all aspects, improve fineness, dimensional stability, surface smoothness, tensile strength, bending strength, bending elastic modulus and thermal deformation temperature, and reduce equipment wear.
Calcium sulfate whisker has good friction, thermal insulation, fire prevention and non-conductor insulation properties, and can replace asbestos as friction material, thermal insulation material and flame retardant (flame retardant) material. As asphalt filler, it can significantly improve the softening point of asphalt.
Characteristics of calcium sulfate:
The solubility of hydrous compounds in water is very low, reaching the maximum at100 f (38 c), but it will decrease at lower or higher temperatures. Moderate heating will take away most of the water, leaving some hydrated white powder, commonly known as plaster of Paris. Only by adding water can the hydrated form be regenerated from it. At first, a paste is formed, but as the compound absorbs water and gives off heat, it will soon solidify. Stronger heating will take away more water, leaving anhydrous forms or anhydrite.
Occurrence and production
Gypsum and anhydrite are a large number of deposited minerals. They are usually transparent or white, but they are changed into other colors by magazines and can be found in crystalline or granular rock layers. Gypsum deposits are formed by evaporation in the inland sea for hundreds of years: different mineral layers are deposited in turn, and due to the gradual disappearance of water, mineral layers with low water solubility will be formed first. When these deposits are heated, the water is dispersed, leaving anhydrite. 20 1 1, the United States found gypsum on Mars, indicating that there is water here.
Naturally occurring gypsum is sometimes called alabaster (usually used to make statues), but the word also applies to calcium carbonate. These two things can be distinguished by hydrochloric acid treatment. The reaction of calcium carbonate is to produce carbon dioxide bubbles, while gypsum is basically unaffected.
Most calcium sulfate comes from these sediments and is found all over the world. Some are obtained through by-products of industrial processing. The production of phosphoric acid from calcium phosphate rock is an example. In the laboratory, adding sulfuric acid to soluble calcium compounds can make pure substances; Because of its low solubility, it will precipitate into white fine powder.