what is nicotine'
Nicotine is a highly addictive substance that occurs naturally in tobacco. It is the active ingredient in tobacco smoke. It has a pungent odor and an acrid taste. Nicotine is defined as a poisonous, oily, pale yellow substance that turns brown upon exposure to air. In concentrated form, this chemical is used as a potent insecticide. The amount of nicotine which occurs in tobacco leaves ranges from 2% to 7%. A smoker inhales approximately 3 mg of nicotine per cigarette.