"Cocaine is derived from the coca plant, which, upon consumption, anesthetizes and stimulates the central nervous system.75 The coca plant can be chewed to induce a high and is difficult to obtain in the United States, as cocaine is usually exported from South America in powder form.76
"The chemical name for powder cocaine is cocaine hydrochloride, which is created through a complex process of heating and cooling coca leaves.77 After pulverizing coca leaves into a coarse powder, alcohol is added and distilled off in order to extract the most pure form of cocaine alkaloid.78 Powder cocaine is ingested intranasally, through snorting, and takes effect within five to fifteen minutes; the euphoria lasts up to two hours.79
"Cocaine freebase, first created in the 1970s, is smokeable. To create cocaine freebase, cocaine hydrochloride must be heated and then mixed with ammonia and ether.80 The substance cools and yields smokeable cocaine crystals after drying.81 Ether, an extremely flammable substance, renders the process of smoking cocaine freebase quite dangerous.82 After inhalation, cocaine reaches the brain within ten seconds, and the high lasts for up to five minutes.83
"In the 1980s, a less dangerous form of cocaine freebase was invented: crack cocaine.84 When cocaine powder is mixed with baking soda to form a paste and heated, the substance hardens into rocks.85 This product was given the street name 'crack,' for the crackling sound it makes when smoked.86"

Source

Beaver, Alyssa L., "Getting a Fix on Cocaine Sentencing Policy: Reforming the Sentencing Scheme of the Anti-Drug Abuse Act of 1986," Fordham Law Review (New York, NY: Fordham University School of Law, April 2010) Vol. 78, No. 5, p. 2540.
http://fordhamlawreview.org/a…