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Tetraethyl orthosilicate

≥99.0% (GC)

Orthosilicic acid tetraethyl ester, Silicon tetraethoxide, TEOS, Tetraethyl silicate, Tetraethoxysilane, Tetraethoxysilicon(IV)
Linear Formula:
CAS Number:
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vapor density

7.2 (vs air)

Quality Level

vapor pressure

<1 mmHg ( 20 °C)


≥99.0% (GC)



refractive index

n20/D 1.382 (lit.)
n20/D 1.383


168 °C (lit.)


0.933 g/mL at 20 °C (lit.)

SMILES string




InChI key


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General description

Tetraethyl orthosilicate (TEOS) is an inorganic material that can be used as a silica source for the synthesis of silica-based materials such as silicon dioxide, silicon oxycarbides, silanol, siloxane polymer, and organosilicon thin films for a variety of applications. It can also be used in the synthesis of blended membranes, and the production of aerogel. Other applications include coatings for carpets and other objects.


Tetraethyl orthosilicate (TEOS) can be used:
  • As a reagent along with ferric chloride in the synthesis of dihydropyrimidinones.
  • As a modifier in fabrication of humidity sensing material, poly(2-acrylamido-2-methylpropane sulfonate) (poly-AMPS).
  • As a medium to synthesize triarylamines and diaryl ethers via copper catalyzed, ligand free-Ullmann reaction.
  • As a precursor for the preparation of silica xerogel which finds application in pharmaceutical drug carriers.
  • As a precursor for the synthesis of spherical silica particles by Stober process.

Commonly used as a precursor to prepare xerogel
Will interact with dodecylamine in the formation of intercalation compounds of H+-magadiite and used in a study of mixed-metal bioactive glasses.


1 L in glass bottle
250 mL in glass bottle


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Hazard Statements

Hazard Classifications

Acute Tox. 4 Inhalation - Eye Irrit. 2 - Flam. Liq. 3 - STOT SE 3

Target Organs

Respiratory system

Storage Class Code

3 - Flammable liquids



Flash Point(F)

113.0 °F - closed cup

Flash Point(C)

45 °C - closed cup

Personal Protective Equipment

dust mask type N95 (US), Eyeshields, Gloves

Certificate of Analysis

Certificate of Origin

  1. How does the storage temperature relate to shipping conditions?

    The storage conditions that a Sigma-Aldrich catalog and label recommend for products are deliberately conservative. For many products, long-term storage at low temperatures will increase the time during which they are expected to remain in specification and therefore are labeled accordingly. Where short-term storage, shipping time frame, or exposure to conditions other than those recommended for long-term storage will not affect product quality, Sigma-Aldrich will ship at ambient temperature. The products sensitive to short-term exposure to conditions other than their recommended long-term storage are shipped on wet or dry ice. Ambient temperature shipping helps to control shipping costs for our customers. At any time, our customers can request wet- or dry-ice shipment, but the special handling is at customer expense if our product history indicates that the product is stable for regular shipment. See Shipping and Storage for more information.

  2. Which document(s) contains shelf-life or expiration date information for a given product?

    If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.

  3. How do I get lot-specific information or a Certificate of Analysis?

    The lot specific COA document can be found by entering the lot number above under the "Documents" section.

  4. How do I find price and availability?

    There are several ways to find pricing and availability for our products. Once you log onto our website, you will find the price and availability displayed on the product detail page. You can contact any of our Customer Sales and Service offices to receive a quote.  USA customers:  1-800-325-3010 or view local office numbers.

  5. What is the Department of Transportation shipping information for this product?

    Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product. 

  6. What type of applications can Product No. 86578, Tetraethyl orthosilicate (TEOS), be used in?

    TEOS can be used to synthesize sol-gels or aerogels.

  7. How do you create a sol-gel with Tetraethyl orthosilicate (TEOS), Product No. 86578?

    TEOS can be polymerized with water; the polymerization is based on the hydrolysis or the Si-O-Et groups through forming networks linked by Si-O-Si groups.

  8. How can I accelerate the polymerization of Tetraethyl orthosilicate (TEOS), Product No. 86578?

    The polymerization of TEOS can be accelerated or driven to completion by the addtion of acid or base, both of which serve as a catalyst.

  9. What are the applications of sol-gels formed from Tetraethyl orthosilicate (TEOS), Product No. 86578?

    One of the most improtant application of the sol-gel process is the snythesis of zeolites. Other applications are optical ceramic materials or functionalized biosensors.

  10. What is the vapor pressure of Tetraethyl orthosilicate (TEOS), Product No. 86578, at room temperature?

    The vapor pressure of TEOS at room temperature is 1.5 Torr.

  11. My question is not addressed here, how can I contact Technical Service for assistance?

    Ask a Scientist here.

Preparation of silicon oxycarbide glass fibers from organically modified silicates
Hu, Yi
Journal of materials science & technology, 35(12), 3155-3159 (2000)
A spectroscopic study of an anhydrous tetraethyl orthosilicate-boric acid-ethanol system
Zha Congji, et al.
Journal of Sol-Gel Science and Technology, 13(1-3), 103-107 (1998)
Removal of Cu (II) and Fe (II) ions through thin film composite (TFC) with hybrid membrane
Sulaiman NA, et al.
Journal of Engineering Science and Technology, 36-49 (2016)
Reaction of poly (vinyl butyral) with tetraethyl orthosilicate: grafting of siloxane chains and new composites
Annenkov VV, et al.
Polymer International, 53(6), 772-776 (2004)
Ullmann reaction in tetraethyl orthosilicate: a novel synthesis of triarylamines and diaryl ethers
Zhao Y, et al.
Chemical Communications (Cambridge, England), 30(449), 3186-3188 (2007)

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