Calcium sulfate dried

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... 

Synonyms annalin calcii sulfas hemihydricus calcined gypsum dried calcium sulfate dried gypsum E516 exsiccated calcium sulfate plaster of Paris sulfate of lime yeso bianco. Appearance a white or almost white, odorless, crystalline, hygroscopic powder. 

Solubility practically insoluble in ethanol (95%) slightly soluble in water more soluble in dilute mineral acids. Comments the BP 2004 defines dried calcium sulfate as predominantly the hemihydrate, produced by drying powdered gypsum (CaS04 2H20) at about 150°C, in a controlled manner, such that minimum quantities of the anhydrous material are produced. Dried calcium sulfate may also contain suitable setting accelerators or decelera-tors. 

Hemihydrate, dried calcium sulfate dried gypsum plaster of Paris Annalin. Fine, odorless, tasteless powder. When mi zed with water, sets to a hard mass. Keep well closed. 

SYNONYMS calcium sulfate, hemihydrate, dried calcium sulfate, gypsum hemihydrate, hemihydrate gypsum, (note plaster of paris is the hemihydrate form of calcium sulfate and gypsum is the dihydrate form). 

Anyhydrous compounds have important applications in the chemistry laboratory Calcium chloride forms three hydrates—a monohydrate, a dihydrate, and a hexahydrate. As shown in Figure 10.18, anhydrous calcium chloride is placed in the bottom of tightly sealed containers called desiccators. The calcium chloride absorbs moisture from the air inside the desiccator, creating a dry atmosphere in which other substances can be kept dry. Calcium sulfate is often added to solvents such as ethanol and ethyl ether to keep them free of water. 

Synonyms/Trade Names Calcium sulfate hemihydrate. Dried calcium sulfate, Gypsum hemihydrate, Hemihydrate gypsum [Note Plaster of Paris is the hemihydrate form of Calcium Sulfate Gypsum is the dihydrate form.] ... 

Synonyms Dried calcium sulfate Dried gypsum Gypsum hemihydrate Plaster of Paris... 

Dried calcium sulfate. See Calcium sulfate hemihydrate... 

Use dry calcium sulfate + cobalt chloride granules (97 + 3 mix) in the aeration dryer. This granular material changes gradually firom blue to pink color indicating absorption of water. 

Naphthalenesulfonic Acid. The sulfonation of naphthalene with excess 96 wt % sulfuric acid at < 80°C gives > 85 wt % 1-naphthalenesulfonic acid (a-acid) the balance is mainly the 2-isomer (P-acid). An older German commercial process is based on the reaction of naphthalene with 96 wt % sulfuric acid at 20—50°C (13). The product can be used unpurifted to make dyestuff intermediates by nitration or can be sulfonated further. The sodium salt of 1-naphthalenesulfonic acid is required, for example, for the conversion of 1-naphthalenol (1-naphthol) by caustic fusion. In this case, the excess sulfuric acid first is separated by the addition of lime and is filtered to remove the insoluble calcium sulfate the filtrate is treated with sodium carbonate to precipitate calcium carbonate and leave the sodium l-naphthalenesulfonate/7J(9-/4-J7 in solution. The dry salt then is recovered, typically, by spray-drying the solution. 

Salt that is substantially free of sulfate and other impurities is the cell feed. This grade may be purchased from commercial salt suppHers or made on site by purification of cmde sea or rock salt. Dried calcium chloride or cell bath from dismanded cells is added to the bath periodically as needed to replenish calcium coproduced with the sodium. The heat required to maintain the bath ia the molten condition is suppHed by the electrolysis current. Other electrolyte compositions have been proposed ia which part or all of the calcium chloride is replaced by other salts (61—64). Such baths offer improved current efficiencies and production of cmde sodium containing relatively Htde calcium. 

Fig. 1. Scanning electron micrograph of dried crystals of 5200 ppm calcium sulfate solution containing (a) zero, (b) 10, and (c) 25 mg/L of added...

Calcium sulfate (anhydrous). (Prepared by heating the dihydrate or the hemihydrate in an oven at 235° for 2-3h it can be regenerated.) Available commercially as Drierite. It forms the hemihydrate, 2CaS04.H20, so that its capacity is fairly low (6.6% of its weight of water), and hence is best used on partially dried substances. It is very efficient (being comparable with phosphorus pentoxide and concentrated sulfuric acid). Suitable for most organic compounds. Solvents boiling below 100° can be dried by direct distillation from calcium sulfate. 

Calcium sulfate hemihydrate []0034-76-1 j M 145.2. Sol in H2O (0.2 parts/100 at 18.75°). Completely dehydrated >650°. Dry below 300° to give a solid with estimated pore size ca 38% of vol. Anhydrous CaS04 has high affinity for H2O and will absorb 6.6% of its weight of H2O to form the hemihydrate (gypsum). It sets to a hard mass with H2O, hence should be kept in a tightly sealed container. 

Paints and coatings for automobiles have not been immune to damage by air polluhon. Wolff and co-workers (13) found that damage to automobile finishes was the result of scarring by calcium sulfate crystals formed when sulfuric acid in rain or dew reacted with dry deposited calcium. 

In a dry, 250 ml, three-necked flask equipped with a dropping funnel and magnetic stirrer are placed 40 ml of dry /-butyl alcohol (distilled from calcium hydride) and 4.0 g (0.036 mole) of potassium /-butoxide. The solution is cooled in ice and 40 g (49 ml, 0.49 mole) of dry cyclohexene is added. Bromoform (10 g, 3.5 ml, 0.039 mole) is added to the cooled, stirred reaction vessel dropwise over about hour, and the vessel is stirred an additional hour with the ice bath removed. The reaction mixture is poured into water (approx. 150 ml), and the layers are separated. The aqueous layer is extracted with 25 mi of pentane, and the extract is combined with the organic layer. The combined layers are dried (sodium sulfate), and the solvent is removed. The product is purified by distillation, bp 10078 mm. 

The chloroform solution of the hydrochloride was dried over anhydrous calcium sulfate, and evaporated to dryness, leaving a semisolid residue of product ester hydrochloride. 

Calcium sulfate, CaS04> is used as a drying agent and sold under the trade name Drierite. For the reaction... 

A solution of 183 g. (1.10 moles) of triethyl phosphite (Note 1) in 200 ml. of petroleum ether (b.p. 30-60°) is added to a 3-1., three-necked, round-bottomed flask equipped with a mechanical stirrer, a thermometer, a dropping funnel, and an air condenser the open end of the condenser is connected to a drying tube filled with calcium sulfate or calcium chloride. The flask is immersed in a freezing mixture of sodium chloride and ice, and the stirrer is started. When the temperature of the phosphite solution reaches 0°, a solution of 273 g. (1.00 mole) of hexachlorocyclopentadiene (Note 2) in 100 ml. of petroleum ether (b.p. 30-60°) is added through the dropping funnel at such a rate that the temperature remains between 0° and 10°. The addition requires about 4-6 hours. After the addition is complete, the freezing mixture is removed, and the brown, clear solution is allowed to warm up to room temperature. 

Acetone (certified ACS) was purchased from Fisher Scientific and was dried over calcium sulfate and filtered prior to use. Anhydrous sodium iodide was purchased from Acros Organics and used as received. 

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