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Physical & Chemical properties

Flash point

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For pure formaldehyde, the flash point does not need to be tested as the substance is a gas.
For aqueous solutions, the flash point value depends on formaldehyde concentration and methanol concentration. It can be concluded that without methanol addition, the flash point will not be lower than 80°C. A concentration of 15% methanol results in a flash point of 50°C, while a concentration of 10% methanol result in a flash point above 60°C.

Key value for chemical safety assessment

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Flash Point of aqueous formaldehyde solutions

Thirteen sources concerning the flash point of aqueous formaldehyde were identified.

According to Walker (1967) the experimentally determined flash point of a solution containing 37% formaldehyde is 85, 77.2, and 63.9 for solutions containing 1, 5, or 10% methanol respectively. The experimental determined flashpoint of a formaldehyde solution containing 1% methanol was 85, 80.6, and 79.4 for solution containing 37, 45, or 50% formaldehyde, respectively. From this study it can be concluded that increasing amounts of methanol and increasing formaldehyde concentrations decrease the flash point. According to a study performed by BASF (1988) the experimentally determined (according to DIN EN 22719 CC) flashpoint of a 55% formaldehyde solution is 84 °C. According to a more recent study from BASF (2009) the flash point of a solution containing 49.28 % formaldehyde and 1.57 % methanol was determined (according to DIN EN ISO 2719 Pensky-Martens closed cup method) to be 80.5 °C. In two other studies (BASF 1988) a 31 and 37% formaldehyde solution was tested for its flash point according to DIN EN 22719 (Pensky-Martens closed cup) and according to DIN ISO 2592 (Cleveland open cup). When tested for its flash point the ignition flame extinguist or the substance began to boil.

According to the Merck Index (2013) the flash point is 60 °C for a solution containing ca. 37% formaldehyde usually with 10 -15% methanol. In addition, according to Hawley’s dictionary (2012) and HSDB (2015, the flash point is 50 °C and 85 °C for an aqueous 37% formaldehyde solution with 15% methanol, or methanol free solution respectively. According to the online source CHRIP (2015) the flashpoint of a 37 % formaldehyde solution is 85 °C. The CRC handbook (2010) and the online database Knovel (2012) both reporting a flash point of 85 °C, but no information on concentration in water is available. The online databases GESTIS and RömppChemie report a flashpoint of 32 – 61 °C. However, formaldehyde concentrations are not reported.

For aqueous solutions, the flash point value depends on formaldehyde and methanol concentration in the solution. Overall it can be concluded that without methanol addition, the flash point will not be lower than 80°C. Methanol concentrations decrease the flash point: a concentration of 15% methanol results in a flash point of 50°C, while a concentration of 10% methanol result in a flash point above 60°C.