Note: Sodium Nitrate is somewhat hygroscopic. Stuff you make from it such as pyrotechnic compositions should be used soon after making and not stored for extended periods of time.
WARNING: Both procedures produce large quantities of ammonia gas. You have to do this experiment outside or in a fumehood.
First get ammonium nitrate from an instant cold pack as seen in our previous video: http://www.youtube.com/watch?v=6iMeBxNcZf0
For the baking soda method. Get 80 grams of ammonium nitrate and dissolve it in 150mL of water. Filter it off directly into 84 grams of sodium bicarbonate, which is baking soda. Then boil the mixture down to 100mL or less. This is needed to decompose the ammonium bicarbonate that's formed. It cannot be skipped. The boiling will release large amounts of ammonia so you have to do this outside or in a fumehood. Once it's boiled, leave it to evaporate until dry.
For the sodium hydroxide method: Place 80 grams of ammonium nitrate in a tall container and pour 40 grams of sodium hydroxide on top. Then carefully pour 30mL of water and stand back. It will quickly react to generate ammonia gas and sodium nitrate. Stir the mixture to make sure it's completely reacted and then add another 50mL of water and stir until dissolved. Filter it out and let the clear solution evaporate.
Both methods will produce pure sodium nitrate.
To test the sodium nitrate for reactivity just mix it with an equal amount of sugar and set it on fire. Sugar does not burn by itself but with sodium nitrate it will burn with a bright yellow flame.
Sodium hydroxide is also known as Lye, Caustic Soda, or "Red Devil Lye" and can easily be purchased online.