Calcium sulphate. Description

In modern inorganic chemistry, the classification of salts, the interaction and properties of elements and their various compounds is of great importance. There are substances that take special places among others. Such compounds, in particular, should include calcium sulphate. Formula of the substance CaSO4.

The comparatively large deposits of this compound in the earth's crust make it possible to use it as a raw material in obtaining various materials. The obtained substances can be successfully applied in construction, medicine and other fields.

In natural natural conditions, deposits of a mineral having the composition CaSO4 2 H2O are found. Calcium sulphate is also found in marine (about 1800 000 tons per cubic meter) and fresh water.

Anhydride CaSO4 is a white powder with a density of 2.90-2.99 grams per cubic centimeter. The compound actively absorbs moisture from the air. Due to this property, calcium sulfate is used as a desiccant.

At a temperature of one thousand four hundred and fifty degrees the substance melts and decomposes. The solubility of the substance is enhanced in the presence of HCl, HNO3, NaCl, MgCl2. Calcium sulphate reacts with sulfuric acid, when sintered with carbon it is restored.

Being in water together with MgSO4 and MgCl2, CaSO4 gives it a constant stiffness. Chemical softening of the liquid is possible with the help of reagents. Reduction of water hardness is based on the introduction of substances enriched in its anions.

Water softening is also carried out by the ion exchange method. This method is based on the ability of individual artificial and natural ion exchangers - high-molecular compounds - to exchange the radicals that make up their composition, the ions present in the solution. Aluminosilicates (Na2 [Al2Si2O8] ∙ nH2O, for example) are often used as ion exchangers.

Hydrate with the composition 2CaSO4 H2O - alabaster (burnt gypsum) - is used in making binders. These substances are powdery compounds, from which, when mixed with water, a plastic mass first forms and subsequently solidifies into a solid body. The production of alabaster is carried out during the burning of gypsum under the influence of temperature from one hundred and fifty to one hundred and seventy degrees. This property is used in the production of partition walls and slabs, casts of objects, as well as for plastering.

Firing under the influence of temperature more than two hundred degrees leads to the formation of a soluble form of calcium sulfate anhydrous, at a temperature of more than five hundred degrees - an insoluble form. The latter loses the ability to attach water, in connection with this can not be used as an astringent material.

Natural gypsum can be used as a starting material in the production of cement and sulfuric acid by a combined method.

Natural calcium sulfate can also be used as a desiccant in the analysis of organic compounds. Anhydrous compound is able to absorb 6.6% moisture from the whole mass. Calcium sulphate is also used in the manufacture of thermal insulation materials.