Calcium Sulfate

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calcium sulfate

[′kal·se·əm ′səl‚fāt]
(inorganic chemistry)
CaSO4 A white crystalline salt, insoluble in water; used in Keene's cement, in pigments, as a paper filler, and as a drying agent.
Either of two hydrated forms of the salt: the dihydrate, CaSO4·2H2O, and the hemihydrate, CaSO4·½H2O.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Calcium Sulfate

 

CaSO4, a salt, existing in nature as the dihydrate CaSO4-2H2O (gypsum, selenite) and in an anhydrous state (anhydrite). Anhydrous calcium sulfate occurs in the form of colorless crystals with a density of 2.96 g/cm3 and a melting point of 1450°C. It combines very slowly with water, exhibiting a poor solubility of 0.2036 g per 100 g H2O at 20°C and 0.067 g at 100°C. The half-hydrate CaSO4-1/2 H2O is known; when mixed with water, it hardens rapidly, converting into CaSO«2H2O. Calcium sulfate is used in the manufacture of figures and casts, as a construction material, and in medicine.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

calcium sulfate

Anhydrite or gypsum dihydrate which has been calcined to the point at which all the water of crystallization has been removed.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
(2006) found that relatively higher SAR values after second crop could be elaborated on the basis of more accumulation of salts which caused precipitation of CaSO4 and CaCO3 due to low solubility resulting into high Na+concentration and thus SAR.
En el caso Caso4 se realizan algunos eventos de capacitacion (entre ellos de la tematica TIC).
Weathering by dissolving action is important in areas with gypsum (CaSO4 x 2H2O).
Obtained solution can be more easily filtered than solution containing clay and CaSO4 solids.
Ganguly, "Thermoluminescence of CaSO4 doped with rare earths," Journal of Physics C: Solid State Physics, vol 7, no.
The mixing proportion was 1: 0.6: 2.5 (1 litre broth: 600g CaSo4: 2.5kg charcoal), and was used in the field study as soil application at the rate of 10 kg [ha.sup.-1].
But pyretic sulfur and sulfur from gypsum can during combustion form anhydrite (CaSO4) with CaO from calcite, while Fe from pyrite forms with oxygen hematite.
The obtained results indicate a light sub-saturation with regard to the halite (NaCl), and a sub-saturation with regard to the gypsum (CaS[O.sub.4], 2[H.sub.2]O) and the aragonite (CaC[O.sub.3]), the dolomite ([Ca.sup.++], [Mg.sup.++])[(C[O.sub.3]).sub.2] and of the anhydrite (CaSO4) in all the watershed (Tab.1).
However, to maintain the total hardness, the salts of CaSO4 and MgSO4 (to increase hardness) while ethylenediaminetetraacetic acid (EDTA) and its sodium salt were used to decrease the water hardness.
Previous studies suggest that as the salt concentration in soil solution increases Ca2+ precipitates as CaCO3 and, to a lesser extent as CaSO4, leaving preponderance of Na+ in soil solution that subsequently induces Na+ adsorption on the cation exchange sites (Suarez, 1981) and increases soil pH.
Careful observation of correlation coefficients among the ionic components suggests that NaCl, CaSO4, MgSO4, MgCl2, HNO3, NH4NO3, NH4SO4 and (NH4)2SO4 are predominant species combinations.