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Physical & Chemical properties

Melting point / freezing point

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Description of key information

Pure formaldehyde has a melting point/freezing point between -92 °C  and -118°C 
An aqueous solution of 30.19 % formaldehyde has a melting point/freezing point of ca -18.8 °C

Key value for chemical safety assessment

Additional information

Melting point/freezing point pure formaldehyde:

Fifteen published handbooks and/or authoritative online databases were identified containing information on the melting point/freezing point of pure formaldehyde.

The CRC (2010), Kirk-Othmer (2015), Yaws (2010), EPA (2008), Reaxys _Harries (2015), Knovel (2012) reported a value of -92 °C

The Merck index (2013), Ullmanns (2012), INCHEM (1991), Reaxys_Spence (2015) reported a value of ca. -118 °C

The Gestis database as as well as the Chemsafe database reported a temperature of -117 °C

The Verschueren (2001) handbook and SYKE (2015) online database reported a melting/freezing temperature of -92 °C as well as -118 °C.

The RömppChemie database (2015) reported both -92 °C and -117 °C as melting/freezing temperature.

Based on these data the melting point/freezing point of pure formaldehyde is between -92 °C and -118°C

Melting point/freezing point aqueous formaldehyde solutions:

Three sources were identified containing information on the melting point/freezing point of aqueous formaldehyde solutions.

In an experimental study (BASF 1987, key) the freezing point of a 30.19 % formaldehyde solution (1% methanol) was determined to be -18.8, and the freezing point of 40.08 % solution (1.05 % methanol) was -25.9 °C. A 50 % formaldehyde solution (1.6% methanol) solidified at -9 °C.

In another supporting study from BASF (2000) the freezing point of a 20 % formaldehyde solution (8.5 % methanol) was determined to be -16.3 °C.

Also in an experimental determination of the freezing point of an 25% aqueous formaldehyde solution published by Walker (1967), the freezing point was determined to be -16.45 - -15.45 °C. The freezing point of water is lowered by formaldehyde. In the case of dilute solutions this lowering is as would be expected for the dissolved hydrate, methylene glycol, but decreases at higher concentrations because of the formation of the hydrated polymers.