Calcium sulfate, dihydrate

Gypsum is widely distributed naturally as calcium sulfate dihydrate [101012-1-4], CaS04-2H2 0. When partially calcined, the hemihydrate, CaS04 H2 0, is formed (see Calciumcompounds-calciumsulfates). Gypsum has been used in one form since 1756 for making dental casts, and in another form since 1844 for dental impressions (101). 

AG jg g- - (-104.9 kJ)- (298 K) (-290.2 J/K) (10 kJ/J) - -18.4 kJ Thus, anhydrous calcium sulfate acts as a chemical sponge at room temperature, trapping water vapor spontaneously to form calcium sulfate dihydrate. 

In a subsequent work, Raff used the CIE system to quantify the colors that could be obtained when using FD C aluminum lakes as colorants in tablet formulations [43]. He reported on the concentration dependence of the tristimulus values obtained when calcium sulfate dihydrate was compressed with various amounts of FD C Blue No. 2 aluminum lake, and one example of the reported data is found in Table 1. 

Marshall, W.L. and R. Slusher, 1966, Thermodynamics of calcium sulfate dihydrate in aqueous sodium chloride solutions, 0-110°. The Journal of Physical Chemistry 70,4015 1027. 

Guillini A process for making gypsum from the waste product from the Wet Process for making phosphoric acid. The waste is heated with water in an autoclave this removes impurities and converts the calcium sulfate dihydrate to the hemi-hydrate. 

Prayon One of the Wet processes for making phosphoric acid by reacting phosphate rock with sulfuric acid. The byproduct is gypsum, calcium sulfate dihydrate. It uses a compartmentalized, multi-section, lined, concrete reactor, with finishing tanks in which the gypsum crystals mature. In 1990 one third of the wet process phosphoric acid made in the Western World was made in this way. The process was developed in 1977 by the Societe de Prayon, Belgium. Variations are known as PH2, PHI 1, and PH12. One variation uses solvent extraction with isopropyl ether and tri-n-butyl phosphate. 

Calcium sulfate P-hemihydrate, 4 583 manufacture of, 4 588-590 Calcium sulfate dihydrate (gypsum), 4 582 5 479t... 

Zhang, Y. and Muhammed, M. Solubility of calcium sulfate dihydrate in nitric acid solutions containing calcium nitrate and phosphoric acid, J. Chem. Eng. Data, 34(1) 121-124, 1989. 

As stated earlier in this paper, FGD wet scrubbers can produce either calcium sulfite (the typical product) or calciiun sulfate. The DDO crystallizer is advantageous for either product. The following industrial case history describes the production of calcium sulfate dihydrate (or gypsum) product fi om an industrial in-plant weak sulfuric acid liquor using a DDO crystallizer configuration. 

This paper has described advantages of the sinq>le DDO ciystallizer for production of calcium sulfite in a bench-scale study and calcium sulfate dihydrate (gypsum) in an industrial process. 

Calcium hydroxide on heating at 580°C loses its water, forming calcium oxide (CaO). Ca(OH)2 forms calcium carbonate by absorbing CO2 from air or when CO2 is passed through a suspension in water. Reaction with sulfuric acid yields calcium sulfate dihydrate ... 

It combines with sulfur dioxide to form calcium sulfite hemihydrate, CaSOs MiH20 which can oxidize in air in the presence of moisture to give calcium sulfate dihydrate, CaS04 2H2O. However, when SO2 is passed through a solution of calcium hydroxide, calcium bisulfite, Ca(HS03)2 is obtained. The solution is yellowish when it contains bisulfite in aqueous SO2. 

Synonyms anhydrous calcium sulfate-anhydrite muriacite karstenite anhydrous gypsum anhydrous sulfate of lime hemihydrate-plaster of Paris annalin dried gypsum dried calcium sulfate dihydrate-gypsum alabaster satin spar mineral white terra alha satinite light spar selenite precipitated calcium sulfate native calcium sulfate... 

Gypsum (Calcium Sulfate Dihydrate, Alabaster), CaSO4.2H20 raw 172.17, sp gr 2.31-2.33, white substance, mp loses 3/2HaO by 128° and rest by 167° hardness 1.5 to 2. Occurs naturally in the USA, Canada, England, France, Sicily, Switzerland etc si sol in w sol in acids, glycerin and aqueous Na3S2Oa and ammonium salts... 

CHEMICAL NAME = calcium sulfate calcium sulfate dihydrate ... 

Gypsum calcium sulfate dihydrate CaS04 2H20... 

Calcium sulfate dihydrate, gypsum CaS04 2H20 60-130 Not available 21 21 0... 

Strelyuk described a thin-layer chromatographic method for the qualitative detection of dipyridamole [62], Data were presented on the use of various reagents for the detection by solution color change and precipitate formation in the thin-layer chromatography of dipyridamole. Thin-layer chromatography was on silica gel-calcium sulfate dihydrate, with methanol aqueous ammonia or benzene-dioxane being used as the mobile phase with detection at 270-330 nm. The Rvalues were 0.7-0.75 and 0.5-0.55 for the two solvent systems, and the detection limit was... 

Some types of ionic compounds can absorb water so that each formula unit is attached to a specific number of water molecules. They are called hydrates. Ba0H2 8H20 is called barium hydroxide octahydrate. CaS04 2H20 is called calcium sulfate dihydrate. Can you see the pattern Try naming MgS04 7H20. Use Table 3.8 to help you. You will learn more about hydrates in Chapter 6. 

Compounds that have no water molecules incorporated into them are called anhydrous to distinguish them from their hydrated forms. For example, a chemist might refer to CaS04 as anhydrous calcium sulfate. This is because it is often found in hydrated form as calcium sulfate dihydrate, shown in Figure 6.9. 

Alabaster is a compact form of gypsum often used in sculpture. Gypsum is the common name for calcium sulfate dihydrate, CaS04-2H20. 

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