CALCIUM SULFATE

Calcium sulfate is a grayish-white dense powder that occurs in nature in both an anhydrous form (anhydrite) and hydrated form(gypsum); it is also the byproduct of many chemical reactions. 
Calcium sulfate has many industrial uses;for example, as a source of sulfur and sulfuric acid,in cements, tiles and plaster,as a soil conditioner, in paints, dyes,and polishes, and as a food additive.Calcium sulfate.
Calcium sulfate is an inorganic salt with the chemical formula CaSO

CAS Number: 99400-01-8
Molecular Formula: CaO4S
Molecular Weight: 136.14

Synonyms: CALCIUM SULFATE, 7778-18-9, Anhydrous gypsum, Drierite, Karstenite, Muriacite, calcium sulphate, Basic calcium sulfate, Calcium sulfate, anhydrous, Calcium sulfate anhydrous, Crysalba, Osteoset, Thiolite, Anhydrous sulfate of lime, Natural anhydrite, Sulfuric acid, calcium salt (1:1), Anhydrous calcium sulfate, Oparex 10, Calmatrix, GIBS, Franklin Fiber H 45, SSS-A, Calcarea sulphurica, Dead-burned gypsum, Insoluble anhydrite, Raddichem 27, Calcium sulfate (1:1), Calcium sulfate (CaSO₄), Denka sigma 1000, CAS 20, Shigao, Calcii sulfas, Calcarea sulphurica 30C, Stone paste, Calcium sulphate anhydrous, Anhydrous sulphate of lime, Shi gao, Sulfuric acid calcium salt (1:1), Calcium sulphate, anhydrous, INS No. 516, Calcium (as sulfate), CI 77231, Native calcium sulphate, INS-516, E934B3V59H, NSC-529649, Precipitated calcium sulphate, CALCIUM SULPHATE ANHYDROUS (E516), E-516, CHEBI:31346, Calcium sulfate (1:1) dihydrate, SULFURIC ACID CALCIUM(2+) SALT (1:1), 231-900-3, Calcium salt of sulfuric acid, Calc Sulph, Gypsum, Dental, Calcarea Sulfurica, Calc Sulph 3X, Calc Sulph 6X, Calc Sulph 12X, Calc Sulph 14X, Calc Sulph 30X, Calc Sulph 200X, CALCAREA SULPH, Artificial Dental Stone, TONICPET 3, Dental Stone, Artificial, Stone, Artificial Dental, RefChem:917892, Calcarea Sulphurica 200CK, Calcarea Sulphurica 8003, Calcium sulfate, unspecified, WAT0DDB505, CALCAREA SULFURICA 6X, CALCAREA SULPHURICA 6X, SULFURIC ACID CALCIUM SALT, Bestmade Natural Products Calc Sulph, D-123, 604-615-0, Anhydrite, calcium;sulfate, CaSO₄, Sulfuric acid, calcium salt, Calcium Sulfate, Anhydrous, Puratronic (Metals Basis), Calcium sulfate [NF], Drierite, regular 8 mesh, MFCD00010912, Calcium sulfate (NF), Calcium sulfuricum, 99400-01-8, Caswell No. 152, Calcium sulphate, natural, CCRIS 3666, HSDB 902, EINECS 231-900-3, EPA Pesticide Chemical Code 005602, NSC 529649, Plaster of Paris, anhydrite, Kalziumsulfat, A 30, calcium sulfat, UNII-E934B3V59H, AI3-02330, Calcium Sulfate FCC, CaO₄S, Regular drierite 6 mesh, Calcium Sulfate Submicron, Calcium sulfate nanopowder, Drierite, regular 4 mesh, Calcium sulfate-325 mesh, Drierite commercial 4 mesh, Drierite commercial 6 mesh, Drierite commercial 8 mesh, Indicating drierite 8 mesh, EC 231-900-3, SCHEMBL4120, Drierite, indicating 4 mesh, CALCIUM SULFATE [MI], Drierite, indicating 6 mesh, Drierite commercial 200 mesh, CALCIUM SULFATE [HSDB], CHEMBL2106140, Drierite, regular 10–20 mesh, Drierite, regular 20–40 mesh, DTXSID9029699, Drierite with indicator, 4 mesh, Drierite with indicator, 6 mesh, Drierite with indicator, 8 mesh, Indicating drierite 10–20 mesh, CALCAREA SULPHURICA [HPUS], Drierite without indicator, 4 mesh, Drierite without indicator, 6 mesh, Drierite without indicator, 8 mesh, Drierite commercial 10–20 mesh, Drierite commercial 20–40 mesh, AKOS015902936, CALCIUM SULFATE ANHYDROUS [II], DB15533, CALCIUM SULFATE, UNSPECIFIED FORM, Drierite with indicator, 10–20 mesh, Drierite without indicator, 20–40 mesh, DB-230081, Drierite without indicator, 10–20 mesh, NS00074390, Calcium sulfate with cobalt chloride indicator, Drierite® indicating (CaSO₄), Lab Grade, D09201, USP Solution Calcium Sulfate TS, F545124, Q407258, Calcium Sulfate, Anhydrous, Puratronic (Metals Basis), PubChem, CALCIUM SULFATE;Calcium Sulfate Fcc;calcium sulfate for tofu;(2-Bromo-5-methoxy-59-methyl-phenyl)-methano

Calcium sulfate occurs in several hydrated forms; the anhydrous state (known as anhydrite) is a white crystalline solid often found in evaporite deposits. 
Its dihydrate form is the mineral gypsum, which may be dehydrated to produce bassanite, the hemihydrate state. 
Gypsum occurs in nature as crystals (selenite) or fibrous masses (satin spar), typically colorless to white, though impurities can impart other hues. 

All forms of calcium sulfate are sparingly soluble in water and cause permanent hardness when dissolved therein.
Calcium sulfate is an inorganic compound with the chemical formula CaSO₄.
It consists of calcium cations (Ca²⁺) and sulfate anions (SO₄²⁻) arranged in an ionic crystal lattice.

Calcium sulfate commonly occurs in several hydrated forms, including gypsum and plaster of Paris.
Calcium sulfate occurs naturally as the mineral gypsum (CaSO₄·2H₂O).
When partially dehydrated, it forms calcium sulfate hemihydrate (CaSO₄·½H₂O), commonly known as plaster of Paris.

The anhydrous form (CaSO₄) is also found in nature as the mineral anhydrite.
Physically, calcium sulfate is a white to colorless solid.
Its solubility in water is relatively low compared to many other sulfate salts.

Solubility varies depending on temperature and degree of hydration.
Chemically, calcium sulfate is stable under normal environmental conditions.
It does not readily decompose and is non-volatile.

In aqueous systems, it dissociates slightly into calcium and sulfate ions.
Calcium sulfate can be produced industrially from natural gypsum or as a by-product of chemical processes.
Calcium sulfate is also formed during flue gas desulfurization in power plants.

Controlled dehydration and rehydration processes allow conversion between its hydrated forms.
Calcium sulfate is widely studied in materials science, geology, and environmental chemistry.
Its phase transformations between gypsum, hemihydrate, and anhydrite are well characterized.

These transformations are important for both natural geological processes and industrial applications.
Calcium sulfate shows distinct physical and structural properties depending on its hydration state.
Gypsum contains two water molecules per formula unit, while plaster of Paris contains half a water molecule and anhydrite contains none.

These differences strongly affect hardness, reactivity with water, and mechanical strength.
When calcium sulfate hemihydrate is mixed with water, it undergoes an exothermic hydration reaction.
This reaction reforms gypsum and causes the material to set and harden.

This setting behavior is the basis for its widespread use in casting and construction materials.
In aqueous environments, calcium sulfate exhibits limited solubility and establishes a dissolution–precipitation equilibrium.
This equilibrium plays an important role in controlling water hardness and scaling.

Calcium sulfate is less soluble than calcium chloride but more soluble than calcium carbonate.
From a geological perspective, calcium sulfate deposits form through evaporation of sulfate-rich waters.
Large gypsum and anhydrite deposits are associated with evaporite formations.

These deposits provide valuable information about ancient climate and marine conditions.
Calcium sulfate is chemically neutral and does not significantly alter pH in solution.
This neutrality distinguishes it from many other calcium salts.

As a result, it is compatible with a wide range of chemical and biological systems.
Thermally, gypsum loses water in stages upon heating.
The first dehydration step forms hemihydrate, followed by complete dehydration to anhydrite.

These controlled phase changes are critical in industrial processing and materials design.
Calcium sulfate also exhibits good compatibility with organic and inorganic additives.

This allows modification of setting time, strength, and microstructure.
Such control is essential in construction, biomedical, and specialty material applications.

Melting point: >300°C
storage temp.: Hygroscopic, Room Temperature, under inert atmosphere
solubility: Water (Slightly)
form: Solid
color: Off-White to Pale Grey
Water Solubility: 2.4g/L
Solubility Product Constant (Ksp): pKsp: 4.31
Dielectric constant: 5.6（0.0℃

Calcium sulfate occurs at three levels of hydration with different crystallographic structures: anhydrous, dihydrate, and hemihydrate.
The anhydrous CaSO4 (anhydrite) crystallizes as an tightly-bound orthohombic lattice with space group Pnma, in which each Ca2+ is 8-coordinated, or surrounded, by 8 oxygen atoms from tetrahedral SO2−4. 
It is similar in topology to zircon.

The dihydrate CaSO4·2H2O (gypsum) forms a monoclinic crystal with space group C2/c. 
Its structure consists of alternating layers: one with Ca2+ coordinated with tetrahedral SO2−4 and another with interstitial water molecules.
Calcium sulfate has a long history of use in dentistry.

Calcium sulfate has been used in bone regeneration as a graft material and graft binder (or extender) and as a barrier in guided bone tissue regeneration. 
Calcium sulfate is a biocompatible material and is completely resorbed following implantation.
Calcium sulfate does not evoke a significant host response and creates a calcium-rich milieu in the area of implantation.

Calcium sulfate has a relatively low solubility in water, which is unusual among sulfate salts.
Its solubility slightly decreases as temperature increases, a behavior known as retrograde solubility.
This characteristic is important in scaling phenomena in boilers, heat exchangers, and desalination systems.

In natural waters, calcium sulfate contributes to permanent hardness.
Unlike temporary hardness caused by bicarbonates, sulfate-related hardness cannot be removed by boiling.
This makes calcium sulfate relevant in water treatment and industrial water management.

From a crystallographic standpoint, calcium sulfate forms well-defined crystal structures.
Gypsum crystals often grow as tabular or prismatic forms, sometimes producing large, transparent crystals known as selenite.
These crystal habits are studied in mineralogy and crystal growth research.

In biological and biomedical contexts, calcium sulfate is considered biocompatible.
It can dissolve gradually in physiological fluids, releasing calcium ions.
This property makes it suitable for temporary biomedical applications where resorption is desired.

Calcium sulfate plays a role in soil chemistry and agriculture.
It supplies both calcium and sulfur, which are essential plant nutrients.
Unlike lime, it improves soil structure without significantly changing soil pH.

Industrially, calcium sulfate is valued for its predictable hydration and dehydration behavior.
The ability to control setting time and mechanical strength through additives is critical.
This tunability supports its use across construction, medical, and specialty material sectors.

Environmentally, calcium sulfate is stable and non-toxic.
Calcium sulfate occurs naturally and participates in the global sulfur cycle.
Its presence in sediments and rocks helps scientists interpret past environmental conditions.

The main use of calcium sulfate is to produce plaster of Paris and stucco. 
These applications exploit the fact that calcium sulfate which has been powdered and calcined forms a moldable paste upon hydration and hardens as crystalline calcium sulfate dihydrate. 
Calcium sulfate is also convenient that calcium sulfate is poorly soluble in water and does not readily dissolve in contact with water after its solidification.

Uses:
Calcium Sulfate is most often used as “gypsum” which is the dihydrate. 
In the form of b-anhydrite (the nearly anhydrous form), it is used as a desiccant. 
Calcium sulfate is also used as a coagulant in products like “tofu”, which is a “bean curd”. 

When sold as a colorindicating variant under the name “Drierite ”, it appears blue or pink due to impregnation with cobalt chloride, which functions as a moisture indicator. 
In its natural state, unrefined calcium sulfate is a translucent, crystalline white rock. 
Many forms are known, including “Alabaster” and “Gypsum”, selenite, Satin spar, Desert rose, and Gypsum flower are four varieties of Gypsum minerals; all four varieties are crystalline. 

The four “crystalline” varieties of gypsum are sometimes grouped together and called selenite. 
All have the same chemical formulation, CaSO4·2H2O. All varieties of gypsum are very soft minerals (hardness: 2 on Mohs scale). 
This is the most important identifying characteristic of gypsum.

Calcium sulfate is widely used in the construction industry.
Gypsum is used to produce plaster, drywall, and gypsum boards for walls and ceilings.
Plaster of Paris is used for casting, molding, and decorative architectural elements.

In building and civil engineering, calcium sulfate is used as a setting regulator in cement.
Small additions control the hydration rate of cement and prevent flash setting.
This ensures workable concrete and consistent strength development.

Calcium sulfate is used in medical and biomedical applications.
Plaster of Paris is used for orthopedic casts, molds, and dental impressions.
Calcium sulfate pellets are also used as temporary bone fillers due to their biocompatibility and resorbability.

In agriculture, calcium sulfate (gypsum) is used as a soil conditioner.
It improves soil structure, reduces sodicity, and supplies calcium and sulfur nutrients.
Unlike lime, it does not significantly alter soil pH.

In food applications, calcium sulfate is used as a food additive.
Calcium sulfate functions as a firming agent, coagulant, and calcium source.
Common examples include tofu production and flour treatment.

Calcium sulfate is applied in water treatment.
Calcium sulfate helps control hardness, scaling, and mineral balance.
It is also used in wastewater treatment and sludge conditioning.

In industrial processes, calcium sulfate is used as a filler and extender.
Calcium sulfate improves texture, strength, and cost efficiency in paints, plastics, and paper.
Its chemical stability makes it suitable for a wide range of formulations.

Calcium sulfate is also used in laboratory and research applications.
Calcium sulfate serves as a drying agent and reference material.
Its well-characterized properties support analytical and materials research.

Calcium Sulfate is a general additive available as both calcium sul- fate anhydrous, made by the high-temperature calcining of gypsum which is then ground and separated, and calcium sulfate dihydrate, which is made by grinding and separating gypsum containing about 20% water of crystallization.
Calcium sulfate anhydrous contains approximately 29% calcium, and calcium sulfate dihydrate contains approximately 23% calcium. 

Calcium sulfate is used, among other things, as a filler and baking powder for standardization purposes; a firming agent in canned potatoes, tomatoes, carrots, lima beans, and pep- pers; in dough as a source of calcium ions (because the absence of calcium ions causes bread dough to be soft and sticky and to pro- duce bread of poor quality); in soft-serve ice cream to produce dry- ness and stiffness; as a calcium ion source for reaction with alginates to form dessert gels; and as a calcium source for food enrichment.
Calcium sulfate is used in the ceramics and pottery industry as a mold material.

Plaster molds made from calcium sulfate hemihydrate absorb water efficiently and allow precise shaping.
This is essential for slip casting of ceramic components.
In the glass industry, calcium sulfate is used as a fining agent and flux modifier.

Calcium sulfate helps remove bubbles and improve glass clarity during melting.
Controlled sulfate content influences glass viscosity and quality.
Calcium sulfate is applied in pharmaceutical manufacturing as an excipient.

Calcium sulfate is used as a filler, binder, or diluent in tablets and capsules.
Its chemical inertness and biocompatibility make it suitable for oral dosage forms.
In paper and pulp processing, calcium sulfate is used as a filler and coating pigment.

Calcium sulfate improves paper brightness, smoothness, and printability.
It also contributes to dimensional stability and cost reduction.
Calcium sulfate is utilized in mining and metallurgy.

Calcium sulfate is used in flotation processes and as a by-product in mineral processing.
Recovered gypsum is often reused in construction or agriculture.
In environmental engineering, calcium sulfate is used in flue gas desulfurization systems.

It is produced as synthetic gypsum during sulfur dioxide removal from exhaust gases.
This by-product is then recycled into building materials.
Calcium sulfate is used in art, sculpture, and education.

Plaster of Paris is widely used for art casting, molds, and teaching demonstrations.
Its fast setting and ease of handling make it ideal for creative and instructional use.
In food processing beyond tofu, calcium sulfate is used to improve texture and firmness.

Safety Profile:
Calcium sulfate is generally considered to have low toxicity and is not classified as hazardous under normal conditions of use.
Calcium sulfate is a naturally occurring mineral widely used in construction, food, medical, and agricultural applications.
Normal handling does not pose significant health risks.

Exposure to dust or fine particles may cause mechanical irritation to the eyes, skin, or respiratory tract.
Inhalation of calcium sulfate dust can lead to coughing, throat irritation, or short-term breathing discomfort.
Adequate ventilation and dust control measures are recommended in occupational environments.

Prolonged skin contact with dry calcium sulfate powder may cause mild dryness or irritation.
This effect is physical rather than chemical and is usually reversible.
Protective gloves and basic hygiene practices help minimize discomfort.

Accidental ingestion of small amounts is generally not harmful.
However, excessive ingestion may cause gastrointestinal discomfort such as constipation or irritation.
Such exposure is unlikely outside industrial or laboratory settings.