Description and uses.
At ordinary temperature and pressure formaldehyde is a gas. It enters commerce as formalin, an aqueous solution containing 40 percent formaldehyde by volume (37 percent by weight) and from 6 to 14 percent methyl alcohol. It is generally made by the oxidation of methyl alcohol. Commercial formalin contains polymers which tend to precipitate in water solution; these are kept in solution by allowing from 6 to 14 percent methyl alcohol to remain in the solution.
The principal use of formaldehyde is in the manufacture of synthetic resins. Other uses are (in the order of their importance): In the manufacture of synthetic indigo; in the manufacture of hydrosulphite; as a disinfectant, deodorant, and preservative; as a fungicide; in embalming fluids; in tanning leather; and in the manufacture of coated paper and wallpaper.