Content deleted Content added
Rescuing 0 sources and tagging 1 as dead.) #IABot (v2.0.9.5 |
Citation bot (talk | contribs) Altered title. Added bibcode. | Use this bot. Report bugs. | Suggested by Abductive | Category:E-number additives | #UCB_Category 235/313 |
||
| (11 intermediate revisions by 6 users not shown) | |||
Line 5:
| verifiedrevid = 443496462
| Name = Calcium sulfate
| ImageFile1= CaSO4simple.svg
| ImageSize =
| ImageName = Calcium sulphate anhydrous
Line 52:
|Section2={{Chembox Properties
| Density = 2.96 g/cm<sup>3</sup> (anhydrous) <br> 2.32 g/cm<sup>3</sup> (dihydrate)
| Solubility = 0.26 g/100ml at 25 °C (dihydrate)<ref>{{cite journal |last1=Lebedev |first1=A. L. |last2=Kosorukov |first2=V. L. |date=2017 |title= Gypsum Solubility in Water at 25°C |url=https://link.springer.com/content/pdf/10.1134/S0016702917010062.pdf |journal=Geochemistry International |volume=55 |issue=2 |pages=171–177 |doi=10.1134/S0016702917010062|bibcode=2017GeocI..55..205L |s2cid=132916752 }}</ref>
| Solvent = [[glycerol]]
| SolubleOther = slightly soluble (dihydrate)
Line 95:
==Hydration states and crystallographic structures==
[[Image:CaSO4.tif|thumb|left|Structure of the hemihydrate of calcium sulfate reveals a dense network of Ca-O-S bonds. Color code: red (O), green (Ca), orange (S).]]
The compound exists in three levels of hydration corresponding to different crystallographic structures and to minerals:
* {{chem|CaSO|4}} ([[anhydrite]]): anhydrous state.<ref>{{cite journal| doi = 10.1107/S0567740875007145| title = Anhydrite: A refinement| journal = Acta Crystallographica Section B| volume = 31| issue = 8| pages = 2164| year = 1975| last1 = Morikawa| first1 = H.| last2 = Minato| first2 = I.| last3 = Tomita| first3 = T.| last4 = Iwai| first4 = S.| bibcode = 1975AcCrB..31.2164M}}</ref> The structure is related to that of [[zirconium orthosilicate]] (zircon): {{chem|Ca||2+}} is 8-coordinate, {{chem|SO|4|2-}} is tetrahedral, O is 3-coordinate.
* {{chem|CaSO|4|·2H|2|O}} ([[gypsum]] and [[selenite (mineral)]]): dihydrate.<ref>{{cite journal| doi = 10.1107/S0567740874004055| title = A refinement of the crystal structure of gypsum {{chem|CaSO|4|·2H|2|O}}| journal = Acta Crystallographica Section B| volume = 30| issue = 4| pages = 921| year = 1974| last1 = Cole| first1 = W.F.| last2 = Lancucki| first2 = C.J.| doi-access = }}</ref>
* {{chem|CaSO|4|·{{sfrac|2}}H|2|O}} ([[bassanite]]): hemihydrate, also known as [[plaster of Paris]]. Specific hemihydrates are sometimes distinguished: α-hemihydrate and β-hemihydrate.<ref name=t>Taylor H.F.W. (1990) ''Cement Chemistry''. Academic Press, {{ISBN|0-12-683900-X}}, pp. 186-187.</ref>
Line 130 ⟶ 131:
Calcium sulfate has a long history of use in dentistry.<ref>{{Cite journal|last1=Titus|first1=Harry W.|last2=McNally|first2=Edmund|last3=Hilberg|first3=Frank C.|date=1933-01-01|title=Effect of Calcium Carbonate and Calcium Sulphate on Bone Development|journal=Poultry Science|language=en|volume=12|issue=1|pages=5–8|doi=10.3382/ps.0120005|issn=0032-5791|doi-access=free}}</ref> It has been used in bone regeneration as a graft material and graft binder (or extender) and as a barrier in guided bone tissue regeneration. It is a biocompatible material and is completely resorbed following implantation.<ref>{{Cite journal |last1=Thomas |first1=Mark V. |last2=Puleo |first2=David A. |last3=Al-Sabbagh |first3=Mohanad |date=2005 |title=Calcium sulfate: a review |url=https://pubmed.ncbi.nlm.nih.gov/16393128/ |journal=Journal of Long-Term Effects of Medical Implants |volume=15 |issue=6 |pages=599–607 |doi=10.1615/jlongtermeffmedimplants.v15.i6.30 |issn=1050-6934 |pmid=16393128}}</ref> It does not evoke a significant host response and creates a calcium-rich milieu in the area of implantation.<ref>{{Cite web|date=2020-03-25|title=Biphasic Calcium Sulfate - Overview|url=https://www.augmabio.com/abca/clinical-literature/biphasic-calcium-sulfate-overview/|access-date=2020-07-16|website=Augma Biomaterials}}</ref>
===
[[File:Drierite.jpg|thumb
When sold at the anhydrous state as a desiccant with a color-indicating agent under the name [[Drierite]], it appears blue (anhydrous) or pink (hydrated) due to impregnation with [[cobalt(II) chloride]], which functions as a moisture indicator.
===Sulfuric acid production===
Up to the 1970s, commercial quantities of [[sulfuric acid]] were produced from anhydrous calcium sulfate.<ref>[https://www.cementkilns.co.uk/cement_kiln_whitehaven.html Whitehaven Cement Plant]</ref> Upon being mixed with [[shale]] or [[marl]], and roasted at 1400°C, the sulfate liberates [[sulfur dioxide]] gas, a precursor to [[sulfuric acid]]. The reaction also produces [[calcium silicate]], used in [[cement]] [[Clinker (cement)|clinker]] production.<ref name="anhydrite process">[https://www.cementkilns.co.uk/cemkilndoc054.html Anhydrite Process]</ref><ref>[https://d28rz98at9flks.cloudfront.net/9554/Rec1949_044.pdf COMMONWEALTH OF AUSTRALIA. DEPARTMENT OF SUPPLY AND SHIPPING. BUREAU OF MINERAL RESOURCES GEOLOGY AND GEOPHYSICS. REPORT NO.1949/44 (Geol. Ser. No. 27) by E.K. Sturmfels THE PRODUCTION OF SULPHURIC ACID AND PORTLAND CEMENT FROM CALCIUM SULPHATE AND ALUMINIUM SILICATES]</ref>
:{{chem2|2 CaSO4 + 2 SiO2 + C → 2 CaSiO3 + 2 SO2 + CO2}}
Some component reactions pertaining to calcium sulfate:
:{{chem2|CaSO4 + 2 C → CaS + 2 CO2}}
:{{chem2|3 CaSO4 + CaS + 2 SiO2 → 2 Ca2SiO4 + 4 SO2}}
:{{chem2|3 CaSO4 + CaS → 4 CaO + 4 SO2}}
:{{chem2|Ca2SiO4 + CaO → Ca3OSiO4}}
==Production and occurrence==
Line 159 ⟶ 149:
In addition to natural sources, calcium sulfate is produced as a by-product in a number of processes:
*In [[flue-gas desulfurization]], exhaust gases from [[fossil-fuel power station]]s and other processes (e.g. cement manufacture) are scrubbed to reduce their sulfur
:{{chem2|SO2 + 0.5 O2 + CaCO3 -> CaSO4 + CO2}}
Related sulfur-trapping methods use [[calcium hydroxide|lime]] and some produces an impure [[calcium sulfite]], which oxidizes on storage to calcium sulfate.
Line 171 ⟶ 161:
Calcium sulfate is also a common component of [[fouling]] deposits in industrial heat exchangers, because its solubility decreases with increasing temperature (see the specific section on the retrograde solubility).
==Solubility==
[[File:Temperature dependence calcium sulfate solubility.svg|thumb|400px|left|Temperature dependence of the solubility of calcium sulfate (3 phases) in pure water.]]
The solubility of calcium sulfate decreases as temperature increases. This behaviour ("retrograde solubility") is uncommon: dissolution of most of the salts is [[endothermic]] and their solubility increases with temperature.The retrograde solubility of calcium sulfate is also responsible for its precipitation in the hottest zone of heating systems and for its contribution to the formation of [[Fouling#Precipitation fouling|scale]] in [[boiler]]s along with the precipitation of [[calcium carbonate]] whose [[solubility]] also decreases when [[Carbon dioxide|CO<sub>2</sub>]] degasses from hot water or can escape out of the system.▼
▲[[File:Temperature dependence calcium sulfate solubility.svg|thumb|400px|left|Temperature dependence of the solubility of calcium sulfate (3 phases) in pure water.]]{{clear left}}
▲The retrograde solubility of calcium sulfate is also responsible for its precipitation in the hottest zone of heating systems and for its contribution to the formation of [[Fouling#Precipitation fouling|scale]] in [[boiler]]s along with the precipitation of [[calcium carbonate]] whose [[solubility]] also decreases when [[Carbon dioxide|CO<sub>2</sub>]] degasses from hot water or can escape out of the system.
==See also==
| |||