Polyhydric alcohols or polyols contain three or more CH
2
OH functional groups. The monomeric compounds have the general formula R(CH
2
OH)
n
, where
and R is an alkyl group or C.CH
2
OH; the dimers and trimers are also commercially significant. Each polyhydric alcohol is a white solid, ranging from the crystalline pentaerythritols to the waxy trimethylol alkyls. The trihydric alcohols are very soluble in water, as is ditrimethylolpropane. Pentaerythritol is moderately soluble and dipentaerythritol and tripentaerythritol are less soluble. Pentaerythritol and trimethylolpropane have no known toxic or irritating effects. Finely powdered pentaerythritol, however, may form explosive dust clouds. Pentaerythritol is produced by reaction of formaldehyde and acetaldehyde in the presence of a basic catalyst, generally an alkali or alkaline‐earth hydroxide. Dipentaerythritol and tripentaerythritol are obtained as by‐products of the pentaerythritol process and may be further purified by fractional crystallization or extraction. Pentaerythritol and trimethylolpropane are classified as nuisance particulate and dust, respectively. The most important industrial use of pentaerythritol is in a wide variety of paints, coatings, and varnishes, where the cross‐linking capability of the four hydroxy groups is critical.
