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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