<unk>  is a chemical compound with the formula<unk> . It is the simplest aldehyde—an organic compound containing a terminal carbonyl group: it consists
of exactly one carbonyl. It was first synthesized by the Russian chemist Aleksandr Butlerov (1828-1886), but was conclusively identified by August Wilhelm von Hofmann.<unk>  exists in several forms aside from<unk> : the cyclic trimer trioxane and the polymer paraformaldehyde. It exists in water as the hydrate H2C(OH)2. Aqueous solutions of<unk>  are referred to as formalin. "100%" formalin consists of a saturated solution of<unk>  (roughly 40% by mass) in water, with a small amount of stabilizer, usually methanol to limit oxidation and polymerization.<unk>  is an intermediate in the oxidation (or combustion) of methane as well as other carbon compounds, e.g. forest fires, in automobile exhaust, and in tobacco smoke. It is produced in the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons; thus, it becomes part of smog. Small amounts of<unk>  are produced as a metabolic byproduct in most organisms, including humans.
Formaldehyde
Nitrazine
Vinyl chloride
Toluene
Trichloroethylene
Acrolein
Ether
Silane