Precipitation is also useful to isolate the products of a reaction during workup. Ideally, the product of the reaction is insoluble in the reaction solvent. Thus, it precipitates as it is formed, preferably forming pure crystals. An example of this would be the synthesis of porphyrins in refluxing propionic acid.
Freebase(0.00 / 0 votes)Rate this definition: Cellophane. Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria and water makes it useful for food packaging.
opium. noun. 1  A bitter, yellowish-brown, strongly addictive narcotic drug prepared from the dried latex of unripe pods of the opium poppy and containing alkaloids such as morphine, codeine, and papaverine.2  Something that numbs or stupefies. a yellow to dark brown, addicting, narcotic drug prepared from the juice of the unripe seed capsules of the opium poppy: it contains such alkaloids as morphine, codeine, and papaverine, and is used as an intoxicant and medicinally to relieve pain and produce sleep.