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Formaldehyde solution

ACS reagent, 37 wt. % in H2O, contains 10-15% Methanol as stabilizer (to prevent polymerization)

Linear Formula:
CAS Number:
Molecular Weight:
MDL number:
PubChem Substance ID:

Quality Level


ACS reagent

vapor density

1.03 (vs air)

vapor pressure

52 mmHg ( 37 °C)
52 mmHg ( 37 °C)





autoignition temp.

572 °F


10-15% Methanol as stabilizer (to prevent polymerization)


37 wt. % in H2O


≤0.006 meq/g Titr. acid

ign. residue



APHA: ≤10

refractive index

n20/D 1.3765


1.09 g/mL at 25 °C (lit.)

anion traces

chloride (Cl-): ≤5 ppm
sulfate (SO42-): ≤0.002%

cation traces

Fe: ≤5 ppm
heavy metals: ≤5 ppm (by ICP-OES)


suitable for manufacturing use (Laboratory chemicals)

SMILES string




InChI key


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General description

Formaldehyde (formalin) is produced by oxidation of methanol. It is made of 37% formaldehyde and impurities such as methanol, small amounts of formic acid, aldehydes and ketones. It is used as a denaturant in formaldehyde-agarose gel electrophoresis of RNA.


Formaldehyde solution has been used for cross-linking/fixing of cells in ChIP (chromatin immunoprecipitation) assay. It has been used for fixing of cells for imaging.
Formaldehyde solution has been used as a fixing agent to fix cells during immunofluorescence imaging and for cross-linking cells during chromatin immunoprecipitation (ChIP) assay.


25, 100, 4×100, 500, 6×500 mL in glass bottle
1, 4 L in glass bottle

Physical form

This product is a solution of approximately 37% by weight of formaldehyde gas in water.

Other Notes

The article number 252549-4X2.5L will be discontinued. Please order the single bottle 252549-2.5L which is physically identical with the same exact specifications.
The article number 252549-6X1L will be discontinued. Please order the single bottle 252549-1L which is physically identical with the same exact specifications.

Signal Word


Hazard Classifications

Acute Tox. 2 Inhalation - Acute Tox. 3 Dermal - Acute Tox. 3 Oral - Carc. 1B - Eye Dam. 1 - Flam. Liq. 3 - Muta. 2 - Skin Corr. 1B - Skin Sens. 1 - STOT SE 1 - STOT SE 3

Target Organs

Respiratory system

Storage Class Code

3 - Flammable liquids



Flash Point(F)

132.8 °F - closed cup

Flash Point(C)

56 °C - closed cup

Certificate of Analysis

Enter Lot Number to search for Certificate of Analysis (COA).

Certificate of Origin

Enter Lot Number to search for Certificate of Origin (COO).

  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. What is the difference between formaldehyde and paraformaldehyde?

    Paraformaldehyde is the polymeric form of formaldehyde. Paraformaldehyde is a solid, and formaldehyde is a gas. Formaldehyde solutions consist of formaldehyde gas dissolved in a solvent of some kind.

  3. 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.

  4. 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.

  5. 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.

  6. 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. 

  7. Do you offer any aqueous paraformaldehyde solutions?

    Product No. 252549 is an aqueous solution of formaldehyde with methanol present to prevent polymerization of the formaldehyde to paraformaldehyde.  Over time (e.g., if a lot of the methanol evaporates), the solution may precipitate the insoluble paraformaldehyde. To break up that polymer, gentle heating should be sufficient. The polymer form has very low solubility in water.

  8. Why is Product No. 252549, Formaldehyde solution, stabilized with methanol?

    The methanol serves to slow the formation of paraformaldehyde.

  9. What is the difference between Formaldehyde solution Products 252549 and 533998?

    The two products are the same chemically. However, the 252549 is designated as an ACS reagent grade. With this description additional specifications are included.

  10. Do you offer 100% formaldehyde instead of solutions like Product No. 252549?

    Formaldehyde in its pure form is a gas. The maximum concentration of formaldehyde in aqueous solution is about 37% by weight.  This is equivalent to an approximately 13.3 M solution.

  11. What is a common application for Product No. 252549, Formaldehyde solution?

    Formaldehyde can be used in multiple applications in different fields.  One common application is that this product is a common building block for the synthesis of more complex compounds and materials.

  12. Is the concentration of Product No. 252549, Formaldehyde solution, expressed as a weight percent solution?

    Yes, 37% is a reference to weight percent solution.  Unless otherwise noted, this is the standard practice for reporting concentration by percent. In terms of volume percent, this solution would be approximately 40% by volume.

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

    Ask a Scientist here.

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