Finally, it should be noted that secondary formation of formaldehyde occurs in air through the oxidation of volatile organic compounds (VOCs) and reactions between ozone (mainly from outdoors) and alkenes (especially terpenes) have been widely described. However, formaldehyde is also extensively produced industrially worldwide for use in the manufacture of resins, as a disinfectant and fixative, or as a preservative in consumer products.Īll these man-made products and uses are the major indirect sources of formaldehyde, in particular indoors. Other combustion processes (power plants, incineration, etc.) also represent sources of formaldehyde emissions in the atmosphere. Anthropogenic sources include direct ones such as on-site industrial emissions and fuel combustion from traffic. In the environment, it is released through biomass combustion (forest and bush fires) or decomposition and through volcanoes, for example. The octanol/water partition coefficient (log K ow) is 0.35, the vapour pressure is 5.19 × 10 5 Pa at 25 ☌ and the Henry's Law constant is 3.41 × 10 −2 Pa.m 3/mol at 25 ☌.įormaldehyde is ubiquitously found in the environment, because it is formed primarily by numerous natural sources and anthropogenic activities. Formaldehyde is soluble in water (around 400 g/l at 20 ☌), ethanol and chloroform and miscible with acetone, benzene and diethylether. The main chemical and physical properties (of the pure substance) are as follows ( 1, 2): molecular mass 30.03 g/mol relative vapour density 1.03–1.07 (air = 1) melting point −92 ☌ and boiling point −19.1 ☌. The half-life estimated for these reactions is about one hour depending on the environmental conditions. It also reacts very quickly with the hydroxyl radicals to give formic acid. In ambient air, formaldehyde is quickly photo-oxidized in carbon dioxide.

Formaldehyde can also be obtained commercially as a 30–50% (by weight) aqueous solution, known as formalin. Formaldehyde (molecular formula H 2-C=O CAS number 50-00-0) is a colourless gas, flammable and highly reactive at room temperature.

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