formaldehyde
Formaldehyde, chemical formula HCHO or CH2O, molecular weight 30.03, also known as formic aldehyde. Colorless, it has a stimulating effect on the eyes and nose. The gas has a relative density of 1.067 (air = 1) and a liquid density of 0.815 g/cm3 (-20 ° C). Melting point -92 ° C, boiling point -19.5 ° C. Soluble in water and ethanol. The concentration of the aqueous solution is as high as 55%, usually 40%, and is called formalin, commonly known as formalin, which is a colorless liquid with a pungent odor.
It has strong reducing properties, especially in alkaline solution, and it has stronger reducing ability. It can burn, vapor and air form an explosive mixture with an explosion limit of 7% to 73% by volume. The ignition point is about 300 °C.
It can be obtained by dehydrogenation or oxidation of methanol under the catalysis of metals such as silver or copper, and can also be separated from the oxidation products of hydrocarbons. It can be used as a raw material for phenolic resin, urea-formaldehyde resin, vinylon, urotropine, pentaerythritol, dyes, pesticides and disinfectants.
Industrial formaldehyde solution generally contains 37% formaldehyde and 15% methanol as a polymerization inhibitor with a boiling point of 101 °C.
On October 27, 2017, the list of carcinogens published by the World Health Organization's International Agency for Research on Cancer placed formaldehyde on a list of carcinogens.