“Sodium metasilicate”的意思、由来-开放百科全书

词条

Sodium metasilicate

释义

Preparation and properties
Structure
Uses
See also
References

{{merge|Sodium silicate|discuss=Talk:Sodium metasilicate#Merger proposal|date=September 2018}}{{Chembox
| Watchedfields = changed
| verifiedrevid = 476992453
| ImageFile1 = Na2SiO3idealized.png
| ImageSize1 = 244
| ImageName1 = Structural formula of polymeric sodium silicate
| ImageFile2 = Sodium-metasilicate-chain-from-xtal-3D-balls.png
| ImageFile2_Ref = {{chemboximage|correct|??}}
| ImageSize2 = 244
| ImageName2 = Ball and stick model of polymeric sodium silicate
| ImageFile3 = Křemičitan sodný.PNG
| ImageFile3_Ref = {{chemboximage|correct|??}}
| ImageSize3 = 244
| ImageName3 = Sample of sodium silicate in a vial
| IUPACName = Sodium metasilicate
| OtherNames =
|Section1={{Chembox Identifiers
| index1_label = pentahydrate
| index2_label = nonhydrate
| Abbreviations = E550
| CASNo = 6834-92-0
| CASNo1 = 10213-79-3
| CASNo2 = 13517-24-3
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII = 052612U92L
| UNII2 = D8D44215LZ
| PubChem = 23266
| PubChem1 = 61495
| PubChem2 = 61639
| ChemSpiderID = 21758
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 600-279-4
| EC_number = 229-912-9
| RTECS = VV9275000
| UNNumber = 1759 3253
| MeSHName = Sodium+metasilicate
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 60720
| SMILES = [Na+].[Na+].[O-][Si]([O-])=O
| StdInChI = 1S/2Na.O3Si/c;;1-4(2)3/q2*+1;-2
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/2Na.O3Si/c;;1-4(2)3/q2*+1;-2
| StdInChIKey = NTHWMYGWWRZVTN-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = NTHWMYGWWRZVTN-UHFFFAOYAB
|Section2={{Chembox Properties
| Na=2 | O=3 | Si=1
| Formula = Na₂SiO₃
| Appearance = White crystals
| Density = 2.61 g/cm³
| MeltingPtC = 1088
| RefractIndex = 1.52
| Solubility = 22.2 g/100 ml (25 °C)
160.6 g/100 ml (80 °C)
| SolubleOther = insoluble in alcohol
|Section3={{Chembox Thermochemistry
| DeltaHf = −1561.43 kJ/mol
| DeltaGf = −1427 kJ/mol
| Entropy = 113.71 J/(K·mol)
| HeatCapacity = 111.8 J/(K·mol)
|Section4={{Chembox Hazards
| ExternalSDS = Avantor Performance Materials
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 0
| LD50 = 1153{{clarify|reason=units?|date=January 2017}} (rat, oral)
| GHSPictograms = {{GHS05}}{{GHS07}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|302|314|315|318|319|335}}
| PPhrases = {{P-phrases|260|261|264|270|271|280|301+312|301+330+331|302+352|303+361+353|304+340|305+351+338|310|312|321|330|332+313|337+313|362|363|403+233|405|501}}
}}Sodium metasilicate is the chemical substance with formula {{chem|Na|2|SiO|3}}, which is the main component of commercial sodium silicate solutions. It is an ionic compound consisting of sodium cations {{chem|Na|+}} and the polymeric metasilicate anions [–{{chem|Si|O|3|2-}}–]_n. It is a colorless crystalline hygroscopic and deliquescent solid, soluble in water (giving an alkaline solution), but not in alcohols.^[1]

Preparation and properties

The anhydrous compound can be prepared by fusing silicon dioxide {{chem|SiO|2}} (silica, quartz) with sodium oxide {{chem|Na|2|O}} in 1:1 molar ratio.^[2]

The compound crystallizes from solution as various hydrates, such as

pentahydrate {{chem|Na|2|SiO|3}}·5{{chem|H|2|O}} (CAS 10213-79-3, EC 229-912-9, PubChem, 57652358)
nonahydrate {{chem|Na|2|SiO|3}}·9{{chem|H|2|O}} (CAS 13517-24-3, EC 229-912-9, PubChem 57654617)^[3]

Structure

In the anhydrous solid, the metasilicate anion is actually polymeric, consisting of corner-shared {SiO₄} tetrahedra, and not a discrete SiO₃²⁻ ion.^[4]

In addition to the anhydrous form, there are hydrates with the formula Na₂SiO₃·nH₂O (where n = 5, 6, 8, 9), which contain the discrete, approximately tetrahedral anion SiO₂(OH)₂²⁻ with water of hydration. For example, the commercially available sodium silicate pentahydrate Na₂SiO₃·5H₂O is formulated as Na₂SiO₂(OH)₂·4H₂O, and the nonahydrate Na₂SiO₃·9H₂O is formulated as Na₂SiO₂(OH)₂·8H₂O.^[5] The pentahydrate and nonahydrate forms have their own CAS Numbers, [https://pubchem.ncbi.nlm.nih.gov/compound/Sodium_metasilicate_pentahydrate 10213-79-3] and [https://pubchem.ncbi.nlm.nih.gov/compound/Sodium_metasilicate_nonahydrate 13517-24-3] respectively.

Uses

Sodium Metasilicate reacts with acids to produce silica gel.^[6]

Cements and Binders - dehydrated sodium metasilicate forms cement or binding agent.
Pulp and Paper - sizing agent and buffer/stabilizing agent when mixed with hydrogen peroxide.
Soaps and Detergents - as an emulsifying and suspension agent.
Automotive applications - decommissioning of old engines (CARS program), cooling system sealant, exhaust repair.
Egg Preservative - seals eggs increasing shelf life.
Crafts - forms "stalagmites" by reacting with and precipitating metal ions.

References

1. ^Chemical Book: "Sodium metasilicate". Accessed on 2018-05-13.
2. ^J. F. Schairer and N. L. Bowen (1956): "The system {{chem|Na|2|O}}—{{chem|Al|2|O|3}}—{{chem|SiO|2}}". American Journal of Science, volume 254, issue 3, pages 129-195 {{doi|10.2475/ajs.254.3.129}}
3. ^M. F. Bechtold (1955): "Polymerization and Properties of Dilute Aqueous Silicic Acid from Cation Exchange" Journal of Physical Chemistry, volume 59, issue 6, pages 532–541. {{doi|10.1021/j150528a013}}
4. ^{{Greenwood&Earnshaw}}
5. ^Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications {{ISBN|0-19-855370-6}}
6. ^https://sciencing.com/uses-sodium-metasilicate-5447484.html

3 : Inorganic silicon compounds|Sodium compounds|Silicates

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Preparation and properties

Structure

Uses

See also

References