Calcium sulfate.dihydrate CaSO

Barium hydroxide Ba(OH)j 8HjO 2.55 KC Calcium sulfate dihydrate CaSO 2HjO 3.14 10-3... 

Barium hydroxide Ba(OH)j 8H3O 2.55 10- Calcium sulfate dihydrate CaSO H O 3.14 10- ... 

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. 

CaSO 2H2O CSH2 Calcium sulfate dihydrate (gypsum) 3.5... 

It is well known that chemically, gypsum is calcium sulfate dihydrate "CaS0. 2H20" which on heating to a temperature of about 130°C loses three fourths of its water and becomes the hemihydrate CaSO,. HpO (Plaster of Paris). 

Two main categories of the wet process exist, depending on whether the calcium sulfate is precipitated as the dihydrate or the hemihydrate. Operation at 70—80°C and 30% P20 in the Hquid phase results in the precipitation of CaSO 2 filterable form 80—90°C and 40% P20 provide a filterable CaSO O.5H2O. Operation outside these conditions generally results in poor filtration rates. A typical analysis of wet-process acid is given in Table 4. For more detailed discussion of the wet-process acid, see Fertilizers. 

Sulfates and Sulfites. Calcium sulfate [7778-18-9] occurs in large deposits as CaSO and as gypsum, CaSO -2H20. The dihydrate is a... 

Calcium sulfate [7778-18-9J, CaSO, ia mineral form is commonly called gypsum and occurs abundandy ia many areas of the wodd. In natural deposits, the main form is the dihydrate. Some anhydrite is also present ia most areas, although to a lesser extent. Mineral composition can be found ia Table 1. 

From a pure, saturated solution of calcium sulfate the dihydrate CaSO ZHjO crystallizes if the temperature is below 60°G. If the crystaUization occurs at a higher temperature the anhydrous salt GaSO is formed. From common seawater, with its high content of sodium chloride, anhydrous calcium sulfate may also be formed at temperatures down to 30°G [14.3]. During geological periods these processes have occurred in nature and formed the minerals gypsum, the dihydrate, and anhydrite, anhydrous calcium sulfate. 

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