What is nicotine?

   Nicotine is a natural chemical made in tobacco plants. It is poisonous and small amounts eaten or injected can cause severe nausea or death.
   Pure nicotine is a clear liquid, but it becomes dark brown when exposed to air. Its formula is Ci0Hi4N2. It has a burning, bitter taste. It is classed as an alkaloid.
   Nicotine is used in insecticides and for studies of nerve and heart reactions. It is a hazard to smokers though their bodies develop some resistance to its effects.