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252549 Sigma-Aldrich

Formaldehyde solution

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

Synonym: Formalin



Related Categories Aldehydes, Building Blocks, C1 to C6, Carbonyl Compounds, Cell Biology,
grade   ACS reagent
vapor density   1.03 (vs air)
vapor pressure   52 mmHg ( 37 °C)
  52 mmHg ( 37 °C)
assay   36.5-38.0%
autoignition temp.   572 °F
contains   10-15% Methanol as stabilizer (to prevent polymerization)
concentration   37 wt. % in H2O
impurities   ≤0.006 meq/g Titr. acid
ign. residue   ≤0.005%
color   APHA: ≤10
refractive index   n20/D 1.3765
density   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)
suitability   suitable for manufacturing use (Laboratory chemicals)


Frequently Asked Questions

Frequently Asked Questions are available for this Product.


1, 4 L in glass bottle

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

Physical form

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


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.

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.

Price and Availability

Tissue Diagnostics

All labs need water

Biomedical Applications
Safety & Documentation

Safety Information

Signal word 
UN 2209 8 / PGIII
WGK Germany 
Flash Point(F) 
147.2 °F
Flash Point(C) 
64 °C


Certificate of Analysis

Certificate of Origin

Frequently Asked Questions

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. http://www.sigmaaldrich.com/etc/medialib/docs/Sigma-Aldrich/General_Information/shippingandlong-termstoragev3.Par.0001.File.tmp/shippingandlong-termstoragev3.pdf
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.
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. These documents are located on the product detail page under Useful Links & Tools. Click on the following link to search for a Certificate of Analysis. Please click the following link to see the details on our Product Dating Information.
How do I get lot-specific information or a Certificate of Analysis?
A Certificate of Analysis is available by lot number and can be obtained through our Advanced Search Option: http://www.sigmaaldrich.com/catalog/AdvancedSearchPage.do
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. 
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, or search here. 
My question is not addressed here, how can I contact Technical Service for assistance?
Use the option to the right to "Ask a Question" by email of a Technical Service Scientist.
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.
Why is Product No. 252549, Formaldehyde solution, stabilized with methanol?
The methanol serves to slow the formation of paraformaldehyde.
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.
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.
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.
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.
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