what is formalin
Formalin is a solution in water of the gas formaldehyde (CH 2 O). A saturated solution contains about 40% by volume â or 37% by weight â of the gas, plus a small amount of a stabilizer, usually 10-12% methanol; this prevents polymerization.ormaldehyde is manufactured industrially by the oxidation of methanol. Large amounts of the chemical are made this way for use in the production of plastics and resins. Formalin is produced by dissolving the gas in water until the desired concentration is reached, up to a maximum of 40%.