In modern inorganic chemistry, the classification of salts, the interaction and properties of elements and their various compounds are of great importance. There are substances that, among others, occupy special places. Such compounds, in particular, should include calcium sulfate. Formula of the substance CaSO4.
The relatively large deposits of this compound in the
earth's crust make it possible to use it as a raw material in the production of various materials. The resulting substances can be successfully used in construction, medicine and other fields.
Under natural conditions, deposits of a mineral having the composition CaSO4 2 H2O are found. Calcium sulfate is also found in marine (about 1800 000 tons per cubic meter) and fresh water.
CaSO4 anhydride 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 also 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 sulfate reacts with sulfuric acid, when sintering with carbon is restored.
Being in water together with MgSO4 and MgCl2, CaSO4 gives it constant rigidity. Chemical softening of the liquid is possible using reagents. The decrease in water hardness is based on the introduction of substances enriched in its anions.
Water softening is also carried out by ion exchange. This method is based on the ability of individual artificial and natural ion exchangers - high molecular weight compounds - to exchange the radicals in their composition for ions present in the solution. Aluminosilicates (Na2 [Al2Si2O8] ∙ nH2O, for example) often act as ion exchangers.
Hydrate with the composition 2CaSO4 H2O - alabaster (burnt gypsum) - is used in the manufacture of binders. These substances are powdery compounds, from which, when mixed with water, first a plastic mass forms, and subsequently hardens into a solid body. Obtaining alabaster is carried out in the process of firing gypsum under the influence of temperature from one hundred fifty to one hundred and seventy degrees. This property is used in the manufacture of partition panels and plates, casts of objects, as well as in the implementation of plastering.
Firing under the influence of a temperature of 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, and therefore can not be used as a binder.
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 capable of absorbing 6.6% of moisture from the total mass. Calcium sulfate is also used in the manufacture of heat-insulating materials.