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Gypsum

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Identification
Molecular formula
CaSO4·2H2O
CAS number
10101-41-4
IUPAC name
calcium;sulfate;dihydrate
State
State

Gypsum is a solid at room temperature.

Melting point (Celsius)
1 450.00
Melting point (Kelvin)
1 723.00
Boiling point (Celsius)
100.00
Boiling point (Kelvin)
373.00
General information
Molecular weight
172.17g/mol
Molar mass
172.1710g/mol
Density
2.3200g/cm3
Appearence

Gypsum is typically found as colorless to white or grayish crystals. These crystals are often translucent with a pearly or silk-like luster. It can also appear in a finely granular or powdery form. Gypsum is well-known for its softness and can easily be scratched with a fingernail, which is why it is used to represent the hardness of 2 on the Mohs scale of mineral hardness.

Comment on solubility

Solubility of Calcium Sulfate Dihydrate (CaSO4·2H2O)

Calcium sulfate dihydrate, commonly known as gypsum, presents interesting properties regarding its solubility:

  • Solubility in Water: The solubility of CaSO4·2H2O in water is relatively low, estimated at around 2.0 g/L at room temperature.
  • Temperature Effect: As the temperature increases, the solubility of calcium sulfate dihydrate tends to increase slightly, though it remains limited compared to many other ionic compounds.
  • pH Influence: The solubility can also be affected by the pH of the solution, where a more alkaline environment can facilitate a slight increase in solubility.
  • Applications: This low solubility makes gypsum valuable in various applications, such as in the construction industry and agriculture, where controlled release of calcium is beneficial.

To summarize, while CaSO4·2H2O does dissolve in water, it does so at a modest rate and is significantly less soluble than many other salts. As noted in scientific discussions, "its solubility limit presents a unique balance, allowing it to serve multiple functional roles while minimizing excessive leaching."

Interesting facts

Interesting Facts About Calcium Sulfate Dihydrate

Calcium sulfate dihydrate, commonly known as gypsum, is an intriguing compound with a myriad of applications and characteristics. Here are some fascinating aspects of this compound:

  • Natural Occurrence: Gypsum is found in sedimentary rock formations and is often mined for its plaster and drywall applications. It is also a natural mineral formed through evaporation processes.
  • Construction Material: One of the primary uses of calcium sulfate dihydrate is in the construction industry, where it acts as a key ingredient in plaster and drywall, providing excellent fire resistance and sound insulation.
  • Soil Amendment: Gypsum is used as a soil conditioner to improve soil structure, enhance water infiltration, and reduce erosion, making it valuable in agriculture.
  • Food Industry: This compound is also utilized as a food additive, often listed as E516, which serves as a coagulant in products like tofu and is used to fortify certain foods with calcium.
  • Cultural Significance: Gypsum has been used historically in art and architecture. The famous French painter Jean-Auguste-Dominique Ingres used powdered gypsum to create his artworks, highlighting its versatility beyond industrial applications.
  • Interesting Properties: Calcium sulfate dihydrate can be heated to produce calcium sulfate (anhydrite) and water, a process that is often used to create plaster for building materials. This reversibility makes it unique among many construction materials.

In summary, calcium sulfate dihydrate is not just a simple compound; it is a vital element in construction, agriculture, and even food processing. Its ability to serve multiple purposes across various industries underscores its importance and versatility.

Synonyms
Calcium sulfate dihydrate
10101-41-4
Satinite
Light spar
Mineral White
Satin spar
Annaline
Compactrol
Magnesia White
Native calcium sulfate
Sulfuric acid, calcium salt, hydrate (1:1:2)
Precipitated calcium sulfate
Calcium sulfate, dihydrate
Alabaster
Shigao
Stone paste
Calcium sulphate dihydrate
Shi gao
Sulfuric acid, calcium(2+) salt, dihydrate
Sulfuric acid, calcium salt (1:1), dihydrate
Calcium sulfate dihydrate (CaSO4.2H2O
UNII-4846Q921YM
Calcium(II) sulfate, dihydrate (1:1:2)
Native calcium sulphate
C.I. 77231
CaSO4.2H2O
4846Q921YM
Precipitated calcium sulphate
calcium sulfate--water (1/2)
DTXSID7047514
CHEBI:32583
CALCIUM SULFATE DIHYDRATE (II)
CALCIUM SULFATE DIHYDRATE [II]
CALCIUM SULFATE DIHYDRATE (EP MONOGRAPH)
CALCIUM SULFATE DIHYDRATE [EP MONOGRAPH]
Sulfuric acid, calcium salt, dihydrate
DTXCID7015674
calcii sulfas
calcium sulfate (1:1) dihydrate
terra alba
Phosphogypsum
Landplaster
GIPS
13397-24-5
calcium;sulfate;dihydrate
MFCD00149625
Gypsite
Primoplast
Gypsum stone
Duracal Cemen
Tiger Kencoat
Crystacal R
CoCoat T
G 6 (refractory
SK (mineral)
G 75 (mineral
G 16 (gypsum
Gypsum (Ca(SO4).2H2O)
PE 20A
land plaster
Calcium sulphate solution
GYPSUM [JAN]
GYPSUM [JP]
CaSO4-2H2O
SCHEMBL22965
GYPSUM FIBROSUM [CHP]
CALCIUM SULFATE [WHO-IP]
Calcium sulfate dihydrate, reagent
Calcium sulfate dihydrate ACS grade
CALCII SULFAS [WHO-IP LATIN]
AKOS015903950
CALCIUM SULFATE DIHYDRATE [MI]
CALCIUM SULFATE DIHYDRATE [WHO-DD]
NS00113026
CALCIUM SULFATE (1:1) DIHYDRATE [WHO-IP]
Q30135771