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How to Make Napalm B

Chemical Synthesis of a Gelled Sol

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Napalm B, more usually just called napalm, is an example of a gelled sol. This easy napalm synthesis is an interesting introduction to sols and gels.

Materials

  • 35 g polystyrene (e.g., Styrofoam or other polystyrene foam, used for insulated cups and packing peanuts)
  • 100 ml gasoline
  • matches or a lighter

Procedure

  1. Break the polystyrene into small chunks. Sometimes you can find polystyrene foam beads, which will work fine without any additional processing.

     

  2. Pour 100 ml of gasoline into a glass container, such as a 250 ml beaker. Any similar-size glass container is fine.

     

  3. Stir in the polystyrene, a little at a time. The polystyrene foam will fizz and seem to dissolve, although this really is the formation of the gelled sol.

     

  4. When all of the polystyrene has been added, there should be no remaining liquid gasoline. The glass container will contain a semi-rigid sol.

Observations and Experimentation with Napalm and the Gelled Sol

  1. In an outdoor location, away from heat or flame, invert the container of gelled sol. Notice that it will resist flowing out of the container. Although the sol is a liquid, it behave like a solid in that it maintains its form.

     

  2. If the sol does not fall out of the glass container, gently tap it to dislodge it. Note the characteristics of Napalm B that make it a gelled sol.

     

  3. On a fire-safe surface, ignite the napalm. If you like, compare the combustion of napalm with combustion of 100 ml of gasoline.

Safety

This project is best performed outdoors, since gasoline vapors are volatile and toxic. Wear protective goggles and gloves to protect yourself from splashing of the liquid. Use care when igniting the napalm. It's advisable to have a fire extinguisher handy. This project is intended for mature chemistry students. Keep all materials away from children and pets.

Reference: Robert Bruce Thompson, Illustrated Guide to Home Chemistry Experiments -- All Lab, No Lecture (2008) O'Reilly, pp. 326-329.

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