Believe it or not, there are cheap ways to make potassium nitrate for your chemistry experiments. And the key ingredient… "sodium-free" salt.
Watch this science video tutorial from Nurd Rage on how to make potassium nitrate at home with Dr. Lithium.
You already learned how to make potassium nitrate in a past video, "How to make potassium nitrate from instant cold packs", but this is a cheaper way.
"Sodium-free" salt is actually potassium chloride. Instant cold packs contain ammonium nitrate and if the two are mixed potassium nitrate and ammonium chloride are formed in equilibrium. Fortunately potassium nitrate has lower solubility than ammonium chloride at colder temperatures giving us a means of separation.
Just mix 40 grams of ammonium nitrate with 100mL of water and stir until dissolved. Filter the mixture directly into 37 grams of potassium chloride. Gently heat until completely dissolved, do not boil. Cool the mixture to 0 Celsius in the freezer or on an ice bath. Filter the crystals and dry them. Now you have potassium nitrate.
To test it, mix two parts potassium nitrate with one part sugar and light it up. It should burn with a purple/pinkish flame.
Brought to you by one of WonderHowTo's favorite scientists, NurdRage.